You will no longer surprise anyone with either solar panels or wind turbines, which generate electricity in all regions of the world. But the output from these devices is not constant and it is necessary to install backup power sources or connect to the network to obtain electricity during the period when renewable energy sources do not generate electricity. However, there are plants developed in the 19th century that use “alternative” fuels to generate electricity, i.e. do not burn gas or petroleum products. Such installations are fuel cells.

HISTORY OF CREATION

Fuel cells (FC) or fuel cells were discovered back in 1838-1839 by William Grove (Grove, Grove), when he was studying the electrolysis of water.

Help: Electrolysis of water is the process of decomposition of water under the influence of electric current into hydrogen and oxygen molecules

Having disconnected the battery from the electrolytic cell, he was surprised to find that the electrodes began to absorb the released gas and generate current. The discovery of the process of electrochemical “cold” combustion of hydrogen was a significant event in the energy industry. He later created the Grove battery. This device had a platinum electrode immersed in nitric acid and a zinc electrode in zinc sulfate. It generated a current of 12 amperes and a voltage of 8 volts. Grow himself called this design "wet battery". He then created a battery using two platinum electrodes. One end of each electrode was in sulfuric acid, and the other ends were sealed in containers with hydrogen and oxygen. There was a stable current between the electrodes, and the amount of water inside the containers increased. Grow was able to decompose and improve the water in this device.

"Battery Grow"

(source: Royal Society of the National Museum of Natural History)

The term “fuel cell” (English “Fuel Cell”) appeared only in 1889 by L. Mond and
C. Langer, who tried to create a device for generating electricity from air and coal gas.

HOW IT WORKS?

A fuel cell is a relatively simple device. It has two electrodes: anode (negative electrode) and cathode (positive electrode). A chemical reaction occurs at the electrodes. To speed it up, the surface of the electrodes is coated with a catalyst. FCs are equipped with one more element - membrane. The conversion of the chemical energy of the fuel directly into electricity occurs thanks to the work of the membrane. It separates the two chambers of the element into which fuel and oxidizer are supplied. The membrane allows only protons, which are produced as a result of fuel splitting, to pass from one chamber to another at an electrode coated with a catalyst (electrons then travel through an external circuit). In the second chamber, protons combine with electrons (and oxygen atoms) to form water.

Working principle of a hydrogen fuel cell

At the chemical level, the process of converting fuel energy into electrical energy is similar to the conventional combustion process (oxidation).

During normal combustion in oxygen, oxidation of organic fuel occurs, and the chemical energy of the fuel is converted into thermal energy. Let's see what happens during the oxidation of hydrogen with oxygen in an electrolyte environment and in the presence of electrodes.

By supplying hydrogen to an electrode located in an alkaline environment, a chemical reaction occurs:

2H 2 + 4OH - → 4H 2 O + 4e -

As you can see, we get electrons that, passing through the external circuit, arrive at the opposite electrode, to which oxygen flows and where the reaction takes place:

4e- + O 2 + 2H 2 O → 4OH -

It can be seen that the resulting reaction 2H 2 + O 2 → H 2 O is the same as during normal combustion, but The fuel cell produces electric current and some heat.

TYPES OF FUEL CELLS

It is customary to classify fuel cells according to the type of electrolyte used for the reaction:

Note that fuel cells can also use coal, carbon monoxide, alcohols, hydrazine, and other organic substances as fuel, and air, hydrogen peroxide, chlorine, bromine, nitric acid, etc. as oxidizing agents.

FUEL CELL EFFICIENCY

A feature of fuel cells is no strict limitation on efficiency, like heat engines.

Help: EfficiencyCarnot cycle is the highest possible efficiency among all heat engines with the same minimum and maximum temperatures.

Therefore, the efficiency of fuel cells in theory can be higher than 100%. Many smiled and thought, “The perpetual motion machine has been invented.” No, here we should go back to the school chemistry course. The fuel cell is based on the conversion of chemical energy into electrical energy. This is where miracles happen. Certain chemical reactions as they occur can absorb heat from the environment.

Help: Endothermic reactions are chemical reactions accompanied by the absorption of heat. For endothermic reactions, changes in enthalpy and internal energy have positive values ​​(Δ H >0, Δ U >0), thus the reaction products contain more energy than the starting components.

An example of such a reaction is the oxidation of hydrogen, which is used in most fuel cells. Therefore, theoretically, the efficiency can be more than 100%. But today, fuel cells heat up during operation and cannot absorb heat from the environment.

Help: This limitation is imposed by the second law of thermodynamics. The process of heat transfer from a “cold” body to a “hot” one is not possible.

Plus, there are losses associated with nonequilibrium processes. Such as: ohmic losses due to the specific conductivity of the electrolyte and electrodes, activation and concentration polarization, diffusion losses. As a result, part of the energy generated in fuel cells is converted into heat. Therefore, fuel cells are not perpetual motion machines and their efficiency is less than 100%. But their efficiency is greater than that of other machines. Today Fuel cell efficiency reaches 80%.

Reference: In the forties, the English engineer T. Bacon designed and built a battery of fuel cells with a total power of 6 kW and an efficiency of 80%, running on pure hydrogen and oxygen, but the power-to-weight ratio of the battery turned out to be too small - such elements were unsuitable for practical use and too expensive (source: http://www.powerinfo.ru/).

FUEL CELL PROBLEMS

Almost all fuel cells use hydrogen as fuel, so the logical question arises: “Where can I get it?”

It seems that a fuel cell was discovered as a result of electrolysis, so it is possible to use the hydrogen released as a result of electrolysis. But let's look at this process in more detail.

According to Faraday's law: the amount of a substance that is oxidized at the anode or reduced at the cathode is proportional to the amount of electricity passing through the electrolyte. This means that in order to get more hydrogen, you need to spend more electricity. Existing methods of water electrolysis operate with an efficiency of less than one. Then we use the resulting hydrogen in fuel cells, where the efficiency is also less than unity. Therefore, we will spend more energy than we can produce.

Of course, you can use hydrogen produced from natural gas. This method of producing hydrogen remains the cheapest and most popular. Currently, about 50% of the hydrogen produced worldwide comes from natural gas. But there is a problem with storing and transporting hydrogen. Hydrogen has a low density ( one liter of hydrogen weighs 0.0846 g), so to transport it over long distances it must be compressed. And these are additional energy and monetary costs. Also, don’t forget about safety.

However, there is also a solution here - liquid hydrocarbon fuel can be used as a source of hydrogen. For example, ethyl or methyl alcohol. True, this requires a special additional device - a fuel converter, which at high temperatures (for methanol it will be about 240 ° C) converts alcohols into a mixture of gaseous H 2 and CO 2. But in this case, it is already more difficult to think about portability - such devices are good to use as stationary or car generators, but for compact mobile equipment you need something less bulky.

Catalyst

To enhance the reaction in the fuel cell, the anode surface is usually treated with a catalyst. Until recently, platinum was used as a catalyst. Therefore, the cost of the fuel cell was high. Secondly, platinum is a relatively rare metal. According to experts, with the industrial production of fuel cells, proven reserves of platinum will run out in 15-20 years. But scientists around the world are trying to replace platinum with other materials. By the way, some of them achieved good results. So Chinese scientists replaced platinum with calcium oxide (source: www.cheburek.net).

USING FUEL CELLS

The first fuel cell in automotive technology was tested in 1959. The Alice-Chambers tractor used 1008 batteries to operate. The fuel was a mixture of gases, mainly propane and oxygen.

Source: http://www.planetseed.com/

Since the mid-60s, at the height of the “space race,” spacecraft creators became interested in fuel cells. The work of thousands of scientists and engineers allowed us to reach a new level, and in 1965. fuel cells were tested in the United States on the Gemini 5 spacecraft, and later on the Apollo spacecraft for flights to the Moon and the Shuttle program. In the USSR, fuel cells were developed at NPO Kvant, also for use in space (source: http://www.powerinfo.ru/).

Since in a fuel cell the final product of hydrogen combustion is water, they are considered the cleanest in terms of environmental impact. Therefore, fuel cells began to gain popularity against the backdrop of general interest in the environment.

Already, car manufacturers such as Honda, Ford, Nissan and Mercedes-Benz have created cars powered by hydrogen fuel cells.

Mercedes-Benz - Ener-G-Force powered by hydrogen

When using hydrogen cars, the problem with hydrogen storage is solved. The construction of hydrogen gas stations will make it possible to refuel anywhere. Moreover, refueling a car with hydrogen is faster than charging an electric car at a gas station. But when implementing such projects, we encountered a problem similar to that of electric vehicles. People are ready to switch to a hydrogen car if there is infrastructure for them. And the construction of gas stations will begin if there are a sufficient number of consumers. Therefore, we again came to the dilemma of the egg and the chicken.

Fuel cells are widely used in mobile phones and laptops. The time has already passed when the phone was charged once a week. Now the phone is charged almost every day, and the laptop works for 3-4 hours without a network. Therefore, mobile technology manufacturers decided to synthesize a fuel cell with phones and laptops for charging and operation. For example, the Toshiba company in 2003. demonstrated a finished prototype of a methanol fuel cell. It produces a power of about 100 mW. One refill of 2 cubes of concentrated (99.5%) methanol is enough for 20 hours of operation of the MP3 player. Again, the same Toshiba demonstrated a cell for powering laptops measuring 275x75x40mm, allowing the computer to operate for 5 hours on a single charge.

But some manufacturers have gone further. The PowerTrekk company has released a charger of the same name. PowerTrekk is the world's first water charger. It is very easy to use. The PowerTrekk requires the addition of water to provide instant electricity via the USB cord. This fuel cell contains silicon powder and sodium silicide (NaSi) when mixed with water, the combination generates hydrogen. Hydrogen is mixed with air in the fuel cell itself, and it converts hydrogen into electricity through its membrane-proton exchange, without fans or pumps. You can buy such a portable charger for 149 € (

Fuel cells (electrochemical generators) represent a very efficient, durable, reliable and environmentally friendly method of generating energy. Initially, they were used only in the space industry, but today electrochemical generators are increasingly used in various fields: power supplies for mobile phones and laptops, vehicle engines, autonomous power sources for buildings, and stationary power plants. Some of these devices operate as laboratory prototypes, while others are used for demonstration purposes or are undergoing pre-production testing. However, many models are already used in commercial projects and are mass-produced.

Device

Fuel cells are electrochemical devices capable of providing a high conversion rate of existing chemical energy into electrical energy.

The fuel cell device includes three main parts:

1. Power generation section;
2. CPU;
3. Voltage transformer.

The main part of the fuel cell is the power generation section, which is a battery made of individual fuel cells. A platinum catalyst is included in the structure of the fuel cell electrodes. Using these cells, a constant electric current is created.

One of these devices has the following characteristics: at a voltage of 155 volts, 1400 amperes are produced. The battery dimensions are 0.9 m in width and height, and 2.9 m in length. The electrochemical process in it is carried out at a temperature of 177 °C, which requires heating of the battery at the time of start-up, as well as heat removal during its operation. For this purpose, a separate water circuit is included in the fuel cell, and the battery is equipped with special cooling plates.

The fuel process converts natural gas into hydrogen, which is required for an electrochemical reaction. The main element of the fuel processor is the reformer. In it, natural gas (or other hydrogen-containing fuel) interacts at high pressure and high temperature (about 900 ° C) with water vapor under the action of a nickel catalyst.

To maintain the required temperature of the reformer there is a burner. The steam required for reforming is created from the condensate. An unstable direct current is generated in the fuel cell battery and a voltage converter is used to convert it.

Also in the voltage converter block there are:

• Control devices.
• Safety interlock circuits that shut down the fuel cell during various faults.

Operating principle

The simplest proton exchange membrane cell consists of a polymer membrane that is located between the anode and cathode, as well as the cathode and anode catalysts. The polymer membrane is used as an electrolyte.

• The proton exchange membrane looks like a thin solid organic compound of small thickness. This membrane works as an electrolyte; in the presence of water, it separates the substance into negatively and positively charged ions.
• Oxidation begins at the anode, and reduction occurs at the cathode. The cathode and anode in a PEM cell are made of porous material; it is a mixture of platinum and carbon particles. Platinum acts as a catalyst, which promotes the dissociation reaction. The cathode and anode are made porous so that oxygen and hydrogen pass through them freely.
• The anode and cathode are located between two metal plates, they supply oxygen and hydrogen to the cathode and anode, and remove electrical energy, heat and water.
• Through channels in the plate, hydrogen molecules enter the anode, where the molecules are decomposed into atoms.
• As a result of chemisorption under the influence of a catalyst, hydrogen atoms are converted into positively charged hydrogen ions H+, that is, protons.
• Protons diffuse to the cathode through the membrane, and a flow of electrons goes to the cathode through a special external electrical circuit. A load is connected to it, that is, a consumer of electrical energy.
• Oxygen, which is supplied to the cathode, upon exposure, enters into a chemical reaction with electrons from the external electrical circuit and hydrogen ions from the proton exchange membrane. As a result of this chemical reaction, water appears.

The chemical reaction that occurs in other types of fuel cells (for example, with an acidic electrolyte in the form of orthophosphoric acid H3PO4) is completely identical to the reaction of a device with a proton exchange membrane.

Kinds

Currently, several types of fuel cells are known, which differ in the composition of the electrolyte used:

• Fuel cells based on orthophosphoric or phosphoric acid (PAFC, Phosphoric Acid Fuel Cells).
• Devices with proton exchange membrane (PEMFC, Proton Exchange Membrane Fuel Cells).
• Solid oxide fuel cells (SOFC, Solid Oxide Fuel Cells).
• Electrochemical generators based on molten carbonate (MCFC, Molten Carbonate Fuel Cells).

Currently, electrochemical generators using PAFC technology have become more widespread.

Application

Today, fuel cells are used in the Space Shuttle, reusable spacecraft. They use 12 W units. They generate all the electricity on the spacecraft. The water that is formed during the electrochemical reaction is used for drinking, including for cooling equipment.

Electrochemical generators were also used to power the Soviet Buran, a reusable spacecraft.

Fuel cells are also used in the civilian sector.

• Stationary installations with a power of 5–250 kW and above. They are used as autonomous sources for heat and power supply to industrial, public and residential buildings, emergency and backup power supplies, and uninterruptible power supplies.
• Portable units with a power of 1–50 kW. They are used for space satellites and ships. Instances are created for golf carts, wheelchairs, railway and freight refrigerators, and road signs.
• Mobile installations with a power of 25–150 kW. They are beginning to be used in military ships and submarines, including cars and other vehicles. Prototypes have already been created by such automotive giants as Renault, Neoplan, Toyota, Volkswagen, Hyundai, Nissan, VAZ, General Motors, Honda, Ford and others.
• Microdevices with a power of 1–500 W. They find application in advanced handheld computers, laptops, consumer electronic devices, mobile phones, and modern military devices.

Peculiarities

• Some of the energy from the chemical reaction in each fuel cell is released as heat. Refrigeration required. In an external circuit, the flow of electrons creates a direct current that is used to do work. Stopping the movement of hydrogen ions or opening the external circuit leads to the stop of the chemical reaction.
• The amount of electricity that fuel cells create is determined by gas pressure, temperature, geometric dimensions, and type of fuel cell. To increase the amount of electricity produced by the reaction, fuel cells can be made larger, but in practice several cells are used, which are combined into batteries.
• The chemical process in some types of fuel cells can be reversed. That is, when a potential difference is applied to the electrodes, water can be decomposed into oxygen and hydrogen, which will be collected on the porous electrodes. When the load is turned on, such a fuel cell will generate electrical energy.

Prospects

Currently, electrochemical generators require large initial costs to be used as the main source of energy. With the introduction of more stable membranes with high conductivity, efficient and cheap catalysts, and alternative sources of hydrogen, fuel cells will become highly economically attractive and will be implemented everywhere.

• Cars will run on fuel cells; there will be no internal combustion engines at all. Water or solid-state hydrogen will be used as an energy source. Refueling will be simple and safe, and driving will be environmentally friendly - only water vapor will be produced.
• All buildings will have their own portable fuel cell power generators.
• Electrochemical generators will replace all batteries and will be installed in any electronics and household appliances.

Advantages and disadvantages

Each type of fuel cell has its own disadvantages and advantages. Some require high quality fuel, others have a complex design and require high operating temperatures.

In general, the following advantages of fuel cells can be noted:

• environmental safety;
• electrochemical generators do not need to be recharged;
• electrochemical generators can create energy constantly, they do not care about external conditions;
• flexibility in scale and portability.

Among the disadvantages are:

• technical difficulties with fuel storage and transportation;
• imperfect elements of the device: catalysts, membranes, and so on.

Fuel cell ( Fuel Cell) is a device that converts chemical energy into electrical energy. It is similar in principle to a conventional battery, but differs in that its operation requires a constant supply of substances from the outside for the electrochemical reaction to occur. Hydrogen and oxygen are supplied to the fuel cells, and the output is electricity, water and heat. Their advantages include environmental friendliness, reliability, durability and ease of operation. Unlike conventional batteries, electrochemical converters can operate virtually indefinitely as long as fuel is supplied. They don't have to be charged for hours until they're fully charged. Moreover, the cells themselves can charge the battery while the car is parked with the engine turned off.

The most widely used fuel cells in hydrogen vehicles are proton membrane fuel cells (PEMFCs) and solid oxide fuel cells (SOFCs).

A proton exchange membrane fuel cell works as follows. Between the anode and cathode there is a special membrane and a platinum-coated catalyst. Hydrogen is supplied to the anode, and oxygen (for example, from air) is supplied to the cathode. At the anode, hydrogen is decomposed into protons and electrons with the help of a catalyst. Hydrogen protons pass through the membrane and reach the cathode, and electrons are transferred to the external circuit (the membrane does not allow them to pass through). The potential difference thus obtained leads to the generation of electric current. On the cathode side, hydrogen protons are oxidized by oxygen. As a result, water vapor appears, which is the main element of car exhaust gases. Possessing high efficiency, PEM cells have one significant drawback - their operation requires pure hydrogen, the storage of which is a rather serious problem.

If such a catalyst is found that replaces expensive platinum in these cells, then a cheap fuel cell for generating electricity will immediately be created, which means the world will get rid of oil dependence.

Solid Oxide Cells

Solid oxide SOFC cells are much less demanding on fuel purity. In addition, thanks to the use of a POX reformer (Partial Oxidation), such cells can consume regular gasoline as fuel. The process of converting gasoline directly into electricity is as follows. In a special device - a reformer, at a temperature of about 800 ° C, gasoline evaporates and decomposes into its constituent elements.

This releases hydrogen and carbon dioxide. Further, also under the influence of temperature and using SOFC directly (consisting of a porous ceramic material based on zirconium oxide), hydrogen is oxidized by oxygen in the air. After obtaining hydrogen from gasoline, the process continues according to the scenario described above, with only one difference: the SOFC fuel cell, unlike devices operating on hydrogen, is less sensitive to impurities in the original fuel. So the quality of gasoline should not affect the performance of the fuel cell.

The high operating temperature of SOFC (650–800 degrees) is a significant drawback; the warm-up process takes about 20 minutes. But excess heat is not a problem, since it is completely removed by the remaining air and exhaust gases produced by the reformer and the fuel cell itself. This allows the SOFC system to be integrated into a vehicle as a separate device in a thermally insulated housing.

The modular structure allows you to achieve the required voltage by connecting a set of standard cells in series. And, perhaps most importantly from the point of view of the implementation of such devices, SOFC does not contain very expensive platinum-based electrodes. It is the high cost of these elements that is one of the obstacles in the development and dissemination of PEMFC technology.

Types of fuel cells

Currently, there are the following types of fuel cells:

• A.F.C.– Alkaline Fuel Cell (alkaline fuel cell);
• PAFC– Phosphoric Acid Fuel Cell (phosphoric acid fuel cell);
• PEMFC– Proton Exchange Membrane Fuel Cell (fuel cell with a proton exchange membrane);
• DMFC– Direct Methanol Fuel Cell (fuel cell with direct breakdown of methanol);
• MCFC– Molten Carbonate Fuel Cell (fuel cell of molten carbonate);
• SOFC– Solid Oxide Fuel Cell (solid oxide fuel cell).

Advantages of fuel cells/cells

A fuel cell/cell is a device that efficiently produces direct current and heat from hydrogen-rich fuel through an electrochemical reaction.

A fuel cell is similar to a battery in that it produces direct current through a chemical reaction. The fuel cell includes an anode, a cathode and an electrolyte. However, unlike batteries, fuel cells cannot store electrical energy and do not discharge or require electricity to recharge. Fuel cells/cells can continuously produce electricity as long as they have a supply of fuel and air.

Unlike other power generators, such as internal combustion engines or turbines powered by gas, coal, fuel oil, etc., fuel cells/cells do not burn fuel. This means no noisy high pressure rotors, no loud exhaust noise, no vibration. Fuel cells/cells produce electricity through a silent electrochemical reaction. Another feature of fuel cells/cells is that they convert the chemical energy of the fuel directly into electricity, heat and water.

Fuel cells are highly efficient and do not produce large amounts of greenhouse gases such as carbon dioxide, methane and nitrous oxide. The only emission products during operation are water in the form of steam and a small amount of carbon dioxide, which is not released at all if pure hydrogen is used as fuel. Fuel elements/cells are assembled into assemblies and then into individual functional modules.

History of development of fuel cells/cells

In the 1950s and 1960s, one of the most pressing challenges for fuel cells arose from the National Aeronautics and Space Administration's (NASA) need for energy sources for long-duration space missions. NASA's alkaline fuel cell uses hydrogen and oxygen as fuel by combining the two chemical elements in an electrochemical reaction. The output is three useful byproducts of the reaction in space flight - electricity to power the spacecraft, water for drinking and cooling systems, and heat to warm the astronauts.

The discovery of fuel cells dates back to the beginning of the 19th century. The first evidence of the effect of fuel cells was obtained in 1838.

In the late 1930s, work began on fuel cells with an alkaline electrolyte and by 1939 a cell using high-pressure nickel-plated electrodes was built. During the Second World War, fuel cells/cells were developed for British Navy submarines and in 1958 a fuel assembly consisting of alkaline fuel cells/cells with a diameter of just over 25 cm was introduced.

Interest increased in the 1950s and 1960s, and also in the 1980s, when the industrial world experienced a shortage of petroleum fuels. During the same period, world countries also became concerned about the problem of air pollution and considered ways to generate electricity in an environmentally friendly manner. Fuel cell technology is currently undergoing rapid development.

Operating principle of fuel cells/cells

Fuel cells/cells produce electricity and heat due to an electrochemical reaction taking place using an electrolyte, a cathode and an anode.

The anode and cathode are separated by an electrolyte that conducts protons. After hydrogen flows to the anode and oxygen to the cathode, a chemical reaction begins, as a result of which electric current, heat and water are generated.

At the anode catalyst, molecular hydrogen dissociates and loses electrons. Hydrogen ions (protons) are conducted through the electrolyte to the cathode, while electrons are passed through the electrolyte and travel through an external electrical circuit, creating a direct current that can be used to power equipment. At the cathode catalyst, an oxygen molecule combines with an electron (which is supplied from external communications) and an incoming proton, and forms water, which is the only reaction product (in the form of vapor and/or liquid).

Below is the corresponding reaction:

Reaction at the anode: 2H 2 => 4H+ + 4e -
Reaction at the cathode: O 2 + 4H+ + 4e - => 2H 2 O
General reaction of the element: 2H 2 + O 2 => 2H 2 O

Types and variety of fuel elements/cells

Just as there are different types of internal combustion engines, there are different types of fuel cells - choosing the right type of fuel cell depends on its application.

Fuel cells are divided into high temperature and low temperature. Low temperature fuel cells require relatively pure hydrogen as fuel. This often means that fuel processing is required to convert the primary fuel (such as natural gas) into pure hydrogen. This process consumes additional energy and requires special equipment. High temperature fuel cells do not need this additional procedure as they can "internally convert" the fuel at elevated temperatures, meaning there is no need to invest in hydrogen infrastructure.

Molten Carbonate Fuel Cells/Cells (MCFC)

Molten carbonate electrolyte fuel cells are high temperature fuel cells. The high operating temperature allows the direct use of natural gas without a fuel processor and low calorific value fuel gas from industrial processes and other sources.

The operation of RCFC differs from other fuel cells. These cells use an electrolyte made from a mixture of molten carbonate salts. Currently, two types of mixtures are used: lithium carbonate and potassium carbonate or lithium carbonate and sodium carbonate. To melt carbonate salts and achieve a high degree of ion mobility in the electrolyte, fuel cells with molten carbonate electrolyte operate at high temperatures (650°C). Efficiency varies between 60-80%.

When heated to a temperature of 650°C, the salts become a conductor for carbonate ions (CO 3 2-). These ions pass from the cathode to the anode, where they combine with hydrogen to form water, carbon dioxide and free electrons. These electrons are sent through an external electrical circuit back to the cathode, generating electric current and heat as a by-product.

Reaction at the anode: CO 3 2- + H 2 => H 2 O + CO 2 + 2e -
Reaction at the cathode: CO 2 + 1/2O 2 + 2e - => CO 3 2-
General reaction of the element: H 2 (g) + 1/2O 2 (g) + CO 2 (cathode) => H 2 O (g) + CO 2 (anode)

The high operating temperatures of molten carbonate electrolyte fuel cells have certain advantages. At high temperatures, natural gas is internally reformed, eliminating the need for a fuel processor. In addition, advantages include the ability to use standard construction materials such as stainless steel sheets and nickel catalyst on the electrodes. The waste heat can be used to generate high pressure steam for a variety of industrial and commercial purposes.

High reaction temperatures in the electrolyte also have their advantages. The use of high temperatures requires significant time to achieve optimal operating conditions, and the system responds more slowly to changes in energy consumption. These characteristics allow the use of fuel cell installations with molten carbonate electrolyte under constant power conditions. High temperatures prevent carbon monoxide from damaging the fuel cell.

Fuel cells with molten carbonate electrolyte are suitable for use in large stationary installations. Thermal power plants with an electrical output power of 3.0 MW are commercially produced. Installations with output power up to 110 MW are being developed.

Phosphoric acid fuel cells/cells (PAFC)

Phosphoric (orthophosphoric) acid fuel cells were the first fuel cells for commercial use.

Phosphoric (orthophosphoric) acid fuel cells use an electrolyte based on orthophosphoric acid (H 3 PO 4) with a concentration of up to 100%. The ionic conductivity of phosphoric acid is low at low temperatures, for this reason these fuel cells are used at temperatures up to 150–220°C.

The charge carrier in fuel cells of this type is hydrogen (H+, proton). A similar process occurs in fuel cells with a proton exchange membrane, in which hydrogen supplied to the anode is split into protons and electrons. Protons travel through the electrolyte and combine with oxygen from the air at the cathode to form water. The electrons are sent through an external electrical circuit, thereby generating an electric current. Below are reactions that generate electric current and heat.

Reaction at the anode: 2H 2 => 4H + + 4e -
Reaction at the cathode: O 2 (g) + 4H + + 4e - => 2 H 2 O
General reaction of the element: 2H 2 + O 2 => 2H 2 O

The efficiency of fuel cells based on phosphoric (orthophosphoric) acid is more than 40% when generating electrical energy. With combined production of heat and electricity, the overall efficiency is about 85%. In addition, given operating temperatures, waste heat can be used to heat water and generate atmospheric pressure steam.

The high performance of thermal power plants using fuel cells based on phosphoric (orthophosphoric) acid in the combined production of thermal and electrical energy is one of the advantages of this type of fuel cells. The units use carbon monoxide with a concentration of about 1.5%, which significantly expands the choice of fuel. In addition, CO 2 does not affect the electrolyte and the operation of the fuel cell; this type of cell works with reformed natural fuel. Simple design, low degree of electrolyte volatility and increased stability are also advantages of this type of fuel cell.

Thermal power plants with electrical output power of up to 500 kW are commercially produced. The 11 MW installations have passed the appropriate tests. Installations with output power up to 100 MW are being developed.

Solid Oxide Fuel Cells (SOFC)

Solid oxide fuel cells are the highest operating temperature fuel cells. The operating temperature can vary from 600°C to 1000°C, allowing the use of different types of fuel without special pre-treatment. To handle such high temperatures, the electrolyte used is a thin solid metal oxide on a ceramic base, often an alloy of yttrium and zirconium, which is a conductor of oxygen ions (O2-).

The solid electrolyte provides a sealed transition of gas from one electrode to another, while liquid electrolytes are located in a porous substrate. The charge carrier in fuel cells of this type is the oxygen ion (O 2-). At the cathode, oxygen molecules from the air are separated into an oxygen ion and four electrons. Oxygen ions pass through the electrolyte and combine with hydrogen, creating four free electrons. The electrons are sent through an external electrical circuit, generating electric current and waste heat.

Reaction at the anode: 2H 2 + 2O 2- => 2H 2 O + 4e -
Reaction at the cathode: O 2 + 4e - => 2O 2-
General reaction of the element: 2H 2 + O 2 => 2H 2 O

The efficiency of the produced electrical energy is the highest of all fuel cells - about 60-70%. High operating temperatures allow combined production of thermal and electrical energy to generate high pressure steam. Combining a high-temperature fuel cell with a turbine makes it possible to create a hybrid fuel cell to increase the efficiency of generating electrical energy by up to 75%.

Solid oxide fuel cells operate at very high temperatures (600°C–1000°C), resulting in significant time to reach optimal operating conditions and a slower system response to changes in energy consumption. At such high operating temperatures, no converter is required to recover hydrogen from the fuel, allowing the thermal power plant to operate with relatively impure fuels resulting from gasification of coal or waste gases, etc. The fuel cell is also excellent for high power applications, including industrial and large central power plants. Modules with an electrical output power of 100 kW are commercially produced.

Direct Methanol Oxidation Fuel Cells/Cells (DOMFC)

The technology of using fuel cells with direct methanol oxidation is undergoing a period of active development. It has successfully proven itself in the field of powering mobile phones, laptops, as well as for creating portable power sources. This is what the future use of these elements is aimed at.

The design of fuel cells with direct oxidation of methanol is similar to fuel cells with a proton exchange membrane (MEPFC), i.e. A polymer is used as an electrolyte, and a hydrogen ion (proton) is used as a charge carrier. However, liquid methanol (CH 3 OH) oxidizes in the presence of water at the anode, releasing CO 2, hydrogen ions and electrons, which are sent through an external electrical circuit, thereby generating an electric current. Hydrogen ions pass through the electrolyte and react with oxygen from the air and electrons from the external circuit to form water at the anode.

Reaction at the anode: CH 3 OH + H 2 O => CO 2 + 6H + + 6e -
Reaction at the cathode: 3/2O 2 + 6 H + + 6e - => 3H 2 O
General reaction of the element: CH 3 OH + 3/2O 2 => CO 2 + 2H 2 O

The advantage of this type of fuel cells is their small size, due to the use of liquid fuel, and the absence of the need to use a converter.

Alkaline fuel cells/cells (ALFC)

Alkaline fuel cells are one of the most efficient cells used to generate electricity, with power generation efficiency reaching up to 70%.

Alkaline fuel cells use an electrolyte, an aqueous solution of potassium hydroxide, contained in a porous, stabilized matrix. The potassium hydroxide concentration may vary depending on the operating temperature of the fuel cell, which ranges from 65°C to 220°C. The charge carrier in SHTE is the hydroxyl ion (OH -), moving from the cathode to the anode, where it reacts with hydrogen, producing water and electrons. The water produced at the anode moves back to the cathode, again generating hydroxyl ions there. As a result of this series of reactions taking place in the fuel cell, electricity and, as a by-product, heat are produced:

Reaction at the anode: 2H 2 + 4OH - => 4H 2 O + 4e -
Reaction at the cathode: O 2 + 2H 2 O + 4e - => 4 OH -
General reaction of the system: 2H 2 + O 2 => 2H 2 O

The advantage of SHTE is that these fuel cells are the cheapest to produce, since the catalyst required on the electrodes can be any of the substances that are cheaper than those used as catalysts for other fuel cells. SFCs operate at relatively low temperatures and are among the most efficient fuel cells - such characteristics can consequently contribute to faster power generation and high fuel efficiency.

One of the characteristic features of SHTE is its high sensitivity to CO 2, which may be contained in fuel or air. CO 2 reacts with the electrolyte, quickly poisons it, and greatly reduces the efficiency of the fuel cell. Therefore, the use of SHTE is limited to enclosed spaces, such as space and underwater vehicles, they must run on pure hydrogen and oxygen. Moreover, molecules such as CO, H 2 O and CH4, which are safe for other fuel cells, and even act as fuel for some of them, are harmful to SHFC.

Polymer Electrolyte Fuel Cells (PEFC)

In the case of polymer electrolyte fuel cells, the polymer membrane consists of polymer fibers with water regions in which there is conduction of water ions H2O+ (proton, red) attaches to a water molecule). Water molecules pose a problem due to slow ion exchange. Therefore, a high concentration of water is required both in the fuel and at the outlet electrodes, limiting the operating temperature to 100°C.

Solid acid fuel cells/cells (SFC)

In solid acid fuel cells, the electrolyte (CsHSO 4) does not contain water. The operating temperature is therefore 100-300°C. The rotation of the oxy anions SO 4 2- allows the protons (red) to move as shown in the figure. Typically, a solid acid fuel cell is a sandwich in which a very thin layer of solid acid compound is sandwiched between two electrodes that are tightly pressed together to ensure good contact. When heated, the organic component evaporates, exiting through the pores in the electrodes, maintaining the ability of multiple contacts between the fuel (or oxygen at the other end of the element), the electrolyte and the electrodes.

Various fuel cell modules. Fuel cell battery

1. Fuel cell battery
2. Other equipment operating at high temperatures (integrated steam generator, combustion chamber, heat balance changer)
3. Heat resistant insulation

Fuel cell module

Comparative analysis of types and varieties of fuel cells

Innovative energy-efficient municipal heat and power plants are typically built on solid oxide fuel cells (SOFC), polymer electrolyte fuel cells (PEFC), phosphoric acid fuel cells (PAFC), proton exchange membrane fuel cells (PEMFC) and alkaline fuel cells (ALFC). . Typically have the following characteristics:

The most suitable should be considered solid oxide fuel cells (SOFC), which:

• operate at higher temperatures, reducing the need for expensive precious metals (such as platinum)
• can operate on various types of hydrocarbon fuels, mainly natural gas
• have a longer start-up time and are therefore better suited for long-term action
• demonstrate high power generation efficiency (up to 70%)
• Due to high operating temperatures, the units can be combined with heat transfer systems, bringing the overall system efficiency to 85%
• have virtually zero emissions, operate silently and have low operating requirements compared to existing power generation technologies

Fuel cell type	Working temperature	Power generation efficiency	Fuel type	Application area
RKTE	550–700°C	50-70%		Medium and large installations
FCTE	100–220°C	35-40%	Pure hydrogen	Large installations
MOPTE	30-100°C	35-50%	Pure hydrogen	Small installations
SOFC	450–1000°C	45-70%	Most hydrocarbon fuels	Small, medium and large installations
PEMFC	20-90°C	20-30%	Methanol	Portable
SHTE	50–200°C	40-70%	Pure hydrogen	Space research
PETE	30-100°C	35-50%	Pure hydrogen	Small installations

Since small thermal power plants can be connected to a conventional gas supply network, fuel cells do not require a separate hydrogen supply system. When using small thermal power plants based on solid oxide fuel cells, the heat generated can be integrated into heat exchangers to heat water and ventilation air, increasing the overall efficiency of the system. This innovative technology is best suited to efficiently generate electricity without the need for expensive infrastructure and complex instrument integration.

Application of fuel cells/cells

Application of fuel cells/cells in telecommunication systems

Due to the rapid proliferation of wireless communication systems throughout the world, as well as the increasing socio-economic benefits of mobile phone technology, the need for reliable and cost-effective power backup has become critical. Electricity grid losses throughout the year due to bad weather conditions, natural disasters or limited grid capacity pose an ongoing challenge for grid operators.

Traditional telecom power backup solutions include batteries (valve-regulated lead-acid battery cell) for short-term backup power and diesel and propane generators for longer-term backup power. Batteries are a relatively cheap source of backup power for 1 - 2 hours. However, batteries are not suitable for longer-term backup power because they are expensive to maintain, become unreliable after long periods of use, are sensitive to temperatures, and are hazardous to the environment after disposal. Diesel and propane generators can provide long-term power backup. However, generators can be unreliable, require extensive maintenance, and release high levels of pollutants and greenhouse gases.

To overcome the limitations of traditional power backup solutions, innovative green fuel cell technology has been developed. Fuel cells are reliable, quiet, contain fewer moving parts than a generator, have a wider operating temperature range than a battery: from -40°C to +50°C and, as a result, provide extremely high levels of energy savings. In addition, the lifetime costs of such an installation are lower than those of a generator. Lower fuel cell costs result from just one maintenance visit per year and significantly higher plant productivity. At the end of the day, the fuel cell is a green technology solution with minimal environmental impact.

Fuel cell installations provide backup power for critical communications network infrastructures for wireless, permanent and broadband communications in the telecommunications system, ranging from 250 W to 15 kW, they offer many unrivaled innovative features:

• RELIABILITY– few moving parts and no discharge in standby mode
• ENERGY SAVING
• SILENCE– low noise level
• SUSTAINABILITY– operating range from -40°C to +50°C
• ADAPTABILITY– installation outdoors and indoors (container/protective container)
• HIGH POWER– up to 15 kW
• LOW MAINTENANCE REQUIREMENT– minimal annual maintenance
• ECONOMICAL- attractive total cost of ownership
• GREEN ENERGY– low emissions with minimal impact on the environment

The system senses the DC bus voltage at all times and smoothly accepts critical loads if the DC bus voltage drops below a user-defined set point. The system runs on hydrogen, which is supplied to the fuel cell stack in one of two ways - either from an industrial hydrogen source or from a liquid fuel of methanol and water, using an integrated reforming system.

Electricity is produced by the fuel cell stack in the form of direct current. The DC power is transferred to a converter, which converts the unregulated DC power coming from the fuel cell stack into high quality regulated DC power for the required loads. Fuel cell installations can provide backup power for many days as the duration is limited only by the amount of hydrogen or methanol/water fuel available.

Fuel cells offer superior energy savings, improved system reliability, more predictable performance in a wide range of climates, and reliable operational durability compared to industry standard valve-regulated lead-acid battery packs. Lifetime costs are also lower due to significantly lower maintenance and replacement requirements. Fuel cells offer environmental benefits to the end user as disposal costs and liability risks associated with lead-acid cells are a growing concern.

The performance of electric batteries can be adversely affected by a wide range of factors such as charge level, temperature, cycling, life and other variables. The energy provided will vary depending on these factors and is not easy to predict. The performance of a proton exchange membrane fuel cell (PEMFC) is relatively unaffected by these factors and can provide critical power as long as fuel is available. Increased predictability is an important benefit when moving to fuel cells for mission-critical backup power applications.

Fuel cells generate power only when fuel is supplied, similar to a gas turbine generator, but have no moving parts in the generation area. Therefore, unlike a generator, they are not subject to rapid wear and do not require constant maintenance and lubrication.

The fuel used to drive the extended duration fuel converter is a fuel mixture of methanol and water. Methanol is a widely available, commercially produced fuel that currently has many uses, including windshield washers, plastic bottles, engine additives, and emulsion paints, among others. Methanol is easily transported, can be mixed with water, has good biodegradability and does not contain sulfur. It has a low freezing point (-71°C) and does not decompose during long-term storage.

Application of fuel cells/cells in communication networks

Secure communications networks require reliable backup power solutions that can operate for hours or days in emergency situations if the power grid is no longer available.

With few moving parts and no standby power loss, innovative fuel cell technology offers an attractive solution to current backup power systems.

The most compelling argument for using fuel cell technology in communications networks is the increased overall reliability and safety. During events such as power outages, earthquakes, storms and hurricanes, it is important that systems continue to operate and are provided with reliable backup power over an extended period of time, regardless of temperature or the age of the backup power system.

The line of fuel cell-based power devices are ideal for supporting classified communications networks. Thanks to their energy-saving design principles, they provide environmentally friendly, reliable backup power with extended duration (up to several days) for use in the power range from 250 W to 15 kW.

Application of fuel cells/cells in data networks

Reliable power supply for data networks, such as high-speed data networks and fiber optic backbones, is of key importance throughout the world. The information transmitted over such networks contains critical data for institutions such as banks, airlines or medical centers. A power outage in such networks not only poses a danger to the transmitted information, but also, as a rule, leads to significant financial losses. Reliable, innovative fuel cell installations that provide backup power supply provide the reliability needed to ensure uninterrupted power supply.

Fuel cell units, powered by a liquid fuel mixture of methanol and water, provide reliable backup power with extended duration, up to several days. In addition, these units have significantly reduced maintenance requirements compared to generators and batteries, requiring only one maintenance visit per year.

Typical application site characteristics for using fuel cell installations in data networks:

• Applications with power consumption quantities from 100 W to 15 kW
• Applications with battery life requirements > 4 hours
• Repeaters in fiber optic systems (hierarchy of synchronous digital systems, high-speed Internet, voice over IP...)
• Network nodes for high-speed data transmission
• WiMAX transmission nodes

Fuel cell power backup installations offer numerous benefits for mission-critical data network infrastructures compared to traditional battery or diesel generators, allowing for increased on-site deployment options:

1. Liquid fuel technology solves the problem of hydrogen placement and provides virtually unlimited backup power.
2. Thanks to their quiet operation, low weight, resistance to temperature changes and virtually vibration-free operation, fuel cells can be installed outside buildings, in industrial buildings/containers or on rooftops.
3. Preparations for the use of the system on site are quick and economical, and operating costs are low.
4. The fuel is biodegradable and provides an environmentally friendly solution for urban environments.

Application of fuel cells/cells in security systems

The most carefully designed building security and communications systems are only as reliable as the power supply that supports them. While most systems include some type of uninterruptible power backup system for short-term power losses, they do not accommodate the longer-term power outages that can occur after natural disasters or terrorist attacks. This could be a critical issue for many corporate and government agencies.

Vital systems such as CCTV access monitoring and control systems (ID card readers, door lock devices, biometric identification technology, etc.), automatic fire alarm and fire extinguishing systems, elevator control systems and telecommunication networks, are at risk in the absence of a reliable, long-lasting alternative power supply.

Diesel generators make a lot of noise, are difficult to locate, and have well-known reliability and maintenance problems. In contrast, a fuel cell installation that provides backup power is quiet, reliable, produces zero or very low emissions, and can be easily installed on a rooftop or outside a building. It does not discharge or lose power in standby mode. It ensures the continued operation of critical systems, even after the facility ceases operations and the building is vacated.

Innovative fuel cell installations protect expensive investments in critical applications. They provide environmentally friendly, reliable backup power with extended duration (up to many days) for use in the power range from 250 W to 15 kW, combined with numerous unrivaled features and, especially, high levels of energy savings.

Fuel cell power backup installations offer numerous advantages for use in mission-critical applications such as security and building control systems over traditional battery-powered or diesel generator applications. Liquid fuel technology solves the problem of hydrogen placement and provides virtually unlimited backup power.

Application of fuel cells/cells in municipal heating and power generation

Solid oxide fuel cells (SOFCs) provide reliable, energy-efficient, and emission-free thermal power plants to generate electricity and heat from widely available natural gas and renewable fuel sources. These innovative installations are used in a variety of markets, from home power generation to remote power supply, as well as auxiliary power supplies.

Application of fuel cells/cells in distribution networks

Small thermal power plants are designed to operate in a distributed power generation network consisting of a large number of small generator sets instead of one centralized power plant.

The figure below shows the loss in efficiency of electricity generation when it is generated at a thermal power plant and transmitted to homes through the traditional power transmission networks currently in use. Efficiency losses in centralized generation include losses from the power plant, low-voltage and high-voltage transmission, and distribution losses.

The figure shows the results of the integration of small thermal power plants: electricity is generated with generation efficiency of up to 60% at the point of use. In addition to this, a household can use the heat generated by the fuel cells to heat water and space, which increases the overall efficiency of fuel energy processing and increases energy savings.

Use of fuel cells to protect the environment - utilization of associated petroleum gas

One of the most important tasks in the oil industry is the utilization of associated petroleum gas. Existing methods of utilizing associated petroleum gas have a lot of disadvantages, the main one being that they are not economically viable. Associated petroleum gas is burned, which causes enormous harm to the environment and human health.

Innovative thermal power plants using fuel cells using associated petroleum gas as fuel open the way to a radical and cost-effective solution to the problems of associated petroleum gas utilization.

1. One of the main advantages of fuel cell installations is that they can operate reliably and stably on associated petroleum gas of variable composition. Due to the flameless chemical reaction that underlies the operation of the fuel cell, a decrease in the percentage of, for example, methane only causes a corresponding decrease in power output.
2. Flexibility in relation to the electrical load of consumers, drop, load surge.
3. For the installation and connection of thermal power plants on fuel cells, their implementation does not require capital costs, because The units can be easily installed on unprepared sites near fields, are easy to use, reliable and efficient.
4. High automation and modern remote control do not require permanent presence of personnel at the installation.
5. Simplicity and technical perfection of the design: the absence of moving parts, friction, and lubrication systems provides significant economic benefits from the operation of fuel cell installations.
6. Water consumption: none at ambient temperatures up to +30 °C and negligible at higher temperatures.
7. Water outlet: none.
8. In addition, thermal power plants using fuel cells do not make noise, do not vibrate, do not produce harmful emissions into the atmosphere

Nissan hydrogen fuel cell

Mobile electronics are improving every year, becoming more widespread and accessible: PDAs, laptops, mobile and digital devices, photo frames, etc. All of them are constantly updated with new functions, larger monitors, wireless communications, stronger processors, while decreasing in size . Power technologies, unlike semiconductor technology, are not advancing by leaps and bounds.

The existing batteries and accumulators to power the achievements of the industry are becoming insufficient, so the issue of alternative sources is very acute. Fuel cells are by far the most promising area. The principle of their operation was discovered back in 1839 by William Grove, who generated electricity by changing the electrolysis of water.

Video: Documentary, fuel cells for transport: past, present, future

Fuel cells are of interest to car manufacturers, and spaceship designers are also interested in them. In 1965, they were even tested by America on the Gemini 5 spacecraft launched into space, and later on Apollo. Millions of dollars are still being invested in fuel cell research today, when there are problems associated with environmental pollution and increasing emissions of greenhouse gases generated during the combustion of fossil fuels, the reserves of which are also not endless.

A fuel cell, often called an electrochemical generator, operates in the manner described below.

Being, like accumulators and batteries, a galvanic element, but with the difference that the active substances are stored in it separately. They are supplied to the electrodes as they are used. Natural fuel or any substance obtained from it burns on the negative electrode, which can be gaseous (hydrogen, for example, and carbon monoxide) or liquid, like alcohols. Oxygen usually reacts at the positive electrode.

But the seemingly simple principle of operation is not easy to translate into reality.

DIY fuel cell

Video: DIY hydrogen fuel cell

Unfortunately, we do not have photographs of what this fuel element should look like, we rely on your imagination.

You can make a low-power fuel cell with your own hands even in a school laboratory. You need to stock up on an old gas mask, several pieces of plexiglass, alkali and an aqueous solution of ethyl alcohol (more simply, vodka), which will serve as “fuel” for the fuel cell.

First of all, you need a housing for the fuel cell, which is best made from plexiglass, at least five millimeters thick. The internal partitions (there are five compartments inside) can be made a little thinner - 3 cm. To glue plexiglass, use glue of the following composition: six grams of plexiglass shavings are dissolved in one hundred grams of chloroform or dichloroethane (work is done under a hood).

Now you need to drill a hole in the outer wall, into which you need to insert a glass drain tube with a diameter of 5-6 centimeters through a rubber stopper.

Everyone knows that in the periodic table the most active metals are in the lower left corner, and highly active metalloids are in the upper right corner of the table, i.e. the ability to donate electrons increases from top to bottom and from right to left. Elements that can, under certain conditions, manifest themselves as metals or metalloids are in the center of the table.

Now we pour activated carbon from the gas mask into the second and fourth compartments (between the first partition and the second, as well as the third and fourth), which will act as electrodes. To prevent coal from spilling out through the holes, you can place it in nylon fabric (women's nylon stockings are suitable). IN

The fuel will circulate in the first chamber, and in the fifth there should be an oxygen supplier - air. There will be an electrolyte between the electrodes, and in order to prevent it from leaking into the air chamber, you need to soak it with a solution of paraffin in gasoline (ratio of 2 grams of paraffin to half a glass of gasoline) before filling the fourth chamber with carbon for the air electrolyte. On the layer of coal you need to place (by slightly pressing) copper plates to which the wires are soldered. Through them, the current will be diverted from the electrodes.

All that remains is to charge the element. For this you need vodka, which must be diluted with water 1:1. Then carefully add three hundred to three hundred fifty grams of caustic potassium. For the electrolyte, 70 grams of potassium hydroxide is dissolved in 200 grams of water.

The fuel cell is ready for testing. Now you need to simultaneously pour fuel into the first chamber and electrolyte into the third. A voltmeter connected to the electrodes should show from 07 volts to 0.9. To ensure continuous operation of the element, it is necessary to remove spent fuel (drain into a glass) and add new fuel (through a rubber tube). The feed rate is adjusted by squeezing the tube. This is what the operation of a fuel cell looks like under laboratory conditions, the power of which is understandably low.

Video: Fuel cell or eternal battery at home

To ensure greater power, scientists have been working on this problem for a long time. The active steel in development houses methanol and ethanol fuel cells. But, unfortunately, they have not yet been put into practice.

Why the fuel cell is chosen as an alternative power source

A fuel cell was chosen as an alternative power source, since the end product of hydrogen combustion in it is water. The only problem is finding an inexpensive and efficient way to produce hydrogen. Enormous funds invested in the development of hydrogen generators and fuel cells cannot but bear fruit, so a technological breakthrough and their real use in everyday life is only a matter of time.

Already today the monsters of the automotive industry: General Motors, Honda, Draimler Coyler, Ballard are demonstrating buses and cars that run on fuel cells, the power of which reaches 50 kW. But the problems associated with their safety, reliability, and cost have not yet been resolved. As already mentioned, unlike traditional power sources - batteries and accumulators, in this case the oxidizer and fuel are supplied from the outside, and the fuel cell is only an intermediary in the ongoing reaction of burning fuel and converting the released energy into electricity. “Combustion” occurs only if the element supplies current to the load, like a diesel electric generator, but without a generator and a diesel engine, and also without noise, smoke and overheating. At the same time, the efficiency is much higher, since there are no intermediate mechanisms.

Video: Hydrogen fuel cell car

Great hopes are placed on the use of nanotechnology and nanomaterials, which will help miniaturize fuel cells while increasing their power. There have been reports that ultra-efficient catalysts have been created, as well as designs for fuel cells that do not have membranes. In them, fuel (methane, for example) is supplied to the element along with the oxidizer. Interesting solutions use oxygen dissolved in air as an oxidizer, and organic impurities that accumulate in polluted waters are used as fuel. These are so-called biofuel elements.

Fuel cells, according to experts, may enter the mass market in the coming years.

Hydrogen fuel cells convert the chemical energy of fuel into electricity, bypassing the ineffective processes of combustion and conversion of thermal energy into mechanical energy, which involve large losses. A hydrogen fuel cell is electrochemical The device directly generates electricity as a result of highly efficient “cold” combustion of fuel. The hydrogen-air proton exchange membrane fuel cell (PEMFC) is one of the most promising fuel cell technologies.

Eight years ago, six liquid diesel pumps were discovered in Western Europe; they must be two hundred before the end. We are a far cry from the thousands of fast charging terminals that are hatching all over the place to encourage the spread of electric propulsion. And that's where the rub hurts. And we better announce graphene.

The batteries haven't had their last word

There's more to it than autonomy, which is why limiting charging times is slowing EV adoption. However, he recalled in a note this month to his customers that batteries have a limitation, limited to this type of probe at very high voltages. Thomas Brachman will be told that a hydrogen distribution network still needs to be built. The argument is that he sweeps his hand, recalling that the multiplication of fast charge terminals is also very expensive, due to the high cross-section of high-voltage copper cables. “It is easier and cheaper to transport liquefied hydrogen by truck from buried tanks near production sites.”

A proton-conducting polymer membrane separates the two electrodes, anode and cathode. Each electrode is a carbon plate (matrix) coated with a catalyst. At the anode catalyst, molecular hydrogen dissociates and gives up electrons. Hydrogen cations are conducted through the membrane to the cathode, but electrons are given into the external circuit, since the membrane does not allow electrons to pass through.

Hydrogen is not yet a pure vector of electricity

As for the cost of the battery itself, which is a very sensitive information, Thomas Brachmann has no doubt that it can be significantly reduced as efficiency increases. “Platinum is the element that costs more.” Unfortunately, almost all hydrogen comes from fossil energy sources. Moreover, dihydrogen is just a vector of energy, and not a source from which a non-negligible part is consumed during its production, its liquefaction, and then its conversion into electricity.

At the cathode catalyst, an oxygen molecule combines with an electron (which is supplied from the electrical circuit) and an incoming proton and forms water, which is the only product of the reaction (in the form of vapor and/or liquid).

Membrane-electrode units, which are the key generating element of the energy system, are made from hydrogen fuel cells.

The car of the future behaves like a real one

The battery balance is approximately three times higher, despite losses due to heat in the drivers. Alas, the miracle car will not hit our roads except as part of public demonstrations. Brachmann, who reminds us that the natural silence of an electric car enhances the impression of living in a noisy world. Despite all the difficulties, the steering and brake pedal provide a natural consistency.

Miniature battery but improved performance

The gadget is visible, the central screen diffuses the images of the camera placed in the right mirror as soon as the turn signal is activated. Most of our American customers no longer require, and this allows us to keep prices down - justifies the chief engineer, who offers a lower tariff than. It's actually worth talking about a fuel cell stack since there are 358 that work together. The main reservoir, with a capacity of 117 liters, is pressed against the rear wall of the bench, preventing it from being folded, and the second - 24 liters, is hidden under the seat.

Advantages of hydrogen fuel cells compared to traditional solutions:

- increased specific energy intensity (500 ÷ 1000 Wh/kg),

- extended operating temperature range (-40 0 C / +40 0 C),

- absence of heat spot, noise and vibration,

- reliability at cold start,

- practically unlimited energy storage period (no self-discharge),

First two-stroke fuel cell

Despite its compact size, this new fuel cell converts dihydrogen into electrical current faster and better than its predecessor. It delivers oxygen to the pile elements at a rate previously considered incompatible with their durability. Excess water that previously limited the flow rate is best evacuated. As a result, the power per element increases by half, and efficiency reaches 60%.

This is due to the presence of a 1.7 kWh lithium-ion battery - located under the front seats, which allows additional current to be delivered under strong accelerations. Or the forecast autonomy is 460 km, ideally consistent with what the manufacturer claims.

- the ability to change the energy intensity of the system by changing the number of fuel cartridges, which provides almost unlimited autonomy,

The ability to provide almost any reasonable energy intensity of the system by changing the hydrogen storage capacity,

- high energy intensity,

- tolerance to impurities in hydrogen,

But a thousand parts facilitate air flow and optimize cooling. Even more than its predecessor, this electric car shows that the fuel cell is front and center. A big challenge for the industry and our leaders. Meanwhile, it is very smart who will know which fuel cell or battery will prevail.

A fuel cell is an electrochemical energy conversion device that can produce electricity in the form of direct current by combining a fuel and an oxidizer in a chemical reaction to produce a waste product, typically a fuel oxide.

- long service life,

- environmental friendliness and quiet operation.

Power supply systems based on hydrogen fuel cells for UAVs:

Installation of fuel cells on unmanned vehicles instead of traditional batteries, it multiplies the flight duration and payload weight, increases the reliability of the aircraft, expands the temperature range of UAV launch and operation, reducing the limit to -40 0C. Compared to internal combustion engines, fuel cell-based systems are silent, vibration-free, operate at low temperatures, are difficult to detect during flight, do not produce harmful emissions, and can efficiently perform tasks from video surveillance to payload delivery.

Each fuel cell has two electrodes, one positive and the other negative, and the reaction that produces electricity occurs at the electrodes in the presence of an electrolyte, which carries charged particles from electrode to electrode, while electrons circulate in external wires located between the electrodes to create electricity.

The fuel cell can generate electricity continuously as long as the required flow of fuel and oxidizer is maintained. Some fuel cells produce only a few watts, while others can produce several hundred kilowatts, while smaller batteries are likely to be found in laptops and cell phones, but fuel cells are too expensive to become small generators used to produce electricity for homes and businesses.

Composition of the power supply system for UAVs:

Economic Dimensions of Fuel Cells

Using hydrogen as a fuel source entails significant costs. For this reason, hydrogen is now an uneconomic source, particularly because other less expensive sources can be used. Hydrogen production costs can vary as they reflect the cost of the resources from which it is extracted.

Battery fuel sources

Fuel cells are generally classified into the following categories: hydrogen fuel cells, organic fuel cells, metallic fuel cells, and redox batteries. When hydrogen is used as a fuel source, chemical energy is converted into electricity during the reverse hydrolysis process to produce only water and heat as waste. A hydrogen fuel cell is very low, but can be more or less high in hydrogen production, especially if produced from fossil fuels.

• - fuel cell battery,
• - Li-Po buffer battery to cover short-term peak loads,
• - electronic control system ,
• - fuel system consisting of a cylinder with compressed hydrogen or a solid source of hydrogen.

The fuel system uses high-strength lightweight cylinders and reducers to ensure maximum supply of compressed hydrogen on board. It is allowed to use different sizes of cylinders (from 0.5 to 25 liters) with reducers that provide the required hydrogen consumption.

Hydrogen batteries are divided into two categories: low temperature batteries and high temperature batteries, where high temperature batteries can also use fossil fuels directly. The latter consist of hydrocarbons such as oil or gasoline, alcohol or biomass.

Other fuel sources in batteries include, but are not limited to, alcohols, zinc, aluminum, magnesium, ionic solutions and many hydrocarbons. Other oxidizing agents include, but are not limited to, air, chlorine and chlorine dioxide. Currently, there are several types of fuel cells.

Characteristics of the power supply system for UAVs:

Portable chargers based on hydrogen fuel cells:

Portable chargers based on hydrogen fuel cells are compact devices, comparable in weight and dimensions to existing battery chargers that are actively used in the world.

The ubiquitous portable technology in the modern world regularly needs to be recharged. Traditional portable systems are practically useless at low temperatures, and after performing their function they also require recharging using (electrical networks), which also reduces their efficiency and the autonomy of the device.

Each dihydrogen molecule acquires 2 electrons. The H ion moves from the anode to the cathode and causes an electric current by transferring an electron. What might fuel cells for airplanes look like? Today, tests are being carried out on aircraft to try to fly them using a lithium-ion hybrid fuel cell battery. The fuel cell's true benefit lies in its low-weight integrity: it is lighter, which helps reduce aircraft weight and therefore fuel consumption.

But for now, flying a fuel cell aircraft is not possible because it still has many drawbacks. Image of a fuel cell. What are the disadvantages of a fuel cell? First of all, if hydrogen were common, using it in large quantities would be problematic. Indeed, it is available not only on Earth. It is found in oxygen-containing water and ammonia. Therefore, it is necessary to electrolyze water to obtain it, and this is not yet a widespread method.

Hydrogen fuel cell systems require only the replacement of a compact fuel cartridge, after which the device is immediately ready for use.

Features of portable chargers:

Uninterruptible power supplies based on hydrogen fuel cells:

Guaranteed power supply systems based on hydrogen fuel cells are designed to organize backup power supply and temporary power supply. Guaranteed power supply systems based on hydrogen fuel cells offer significant advantages over traditional solutions for organizing temporary and backup power supply, using batteries and diesel generators.

Hydrogen is a gas, making it difficult to contain and transport. Another risk associated with the use of hydrogen is the risk of explosion, as it is a flammable gas. what supplies the battery for its production on a large scale requires another source of energy, be it oil, gas or coal, or nuclear energy, which makes its environmental balance significantly worse than kerosene and make heap, platinum, a metal that is even rarer and more expensive than gold.

The fuel cell provides energy by oxidizing the fuel at the anode and reducing the oxidizer at the cathode. The discovery of the fuel cell principle and the first implementations in the laboratory using sulfuric acid as an electrolyte is credited to chemist William Grove.

Characteristics of the uninterruptible power supply system:

Fuel cell is an electrochemical device similar to a galvanic cell, but differs from it in that the substances for the electrochemical reaction are supplied to it from the outside - in contrast to the limited amount of energy stored in a galvanic cell or battery.

Indeed, fuel cells have some advantages: those that use dihydrogen and dioxide only emit water vapor: it is therefore a clean technology. There are several types of fuel cells, depending on the nature of the electrolyte, the nature of the fuel, direct or indirect oxidation, and operating temperature.

The following table summarizes the main characteristics of these various devices. Several European programs are looking at other polymers, such as polybenzimidazole derivatives, which are more stable and cheaper. Battery compactness is also an ongoing challenge with membranes on the order of 15-50 microns, porous carbon anodes and stainless steel bipolar plates. Life expectancy can also be improved since, on the one hand, traces of carbon monoxide on the order of a few ppm in hydrogen are real poisons for the catalyst, and on the other hand, control of water in the polymer is mandatory.

Rice. 1. Some fuel cells

Fuel cells convert the chemical energy of fuel into electricity, bypassing ineffective combustion processes that occur with large losses. They convert hydrogen and oxygen into electricity through a chemical reaction. As a result of this process, water is formed and a large amount of heat is released. A fuel cell is very similar to a battery that can be charged and then use the stored electrical energy. The inventor of the fuel cell is considered to be William R. Grove, who invented it back in 1839. This fuel cell used a sulfuric acid solution as an electrolyte and hydrogen as a fuel, which was combined with oxygen in an oxidizing agent. Until recently, fuel cells were used only in laboratories and on spacecraft.

Unlike other power generators, such as internal combustion engines or turbines powered by gas, coal, fuel oil, etc., fuel cells do not burn fuel. This means no noisy high-pressure rotors, no loud exhaust noise, no vibrations. Fuel cells produce electricity through a silent electrochemical reaction. Another feature of fuel cells is that they convert the chemical energy of the fuel directly into electricity, heat and water.

Fuel cells are highly efficient and do not produce large amounts of greenhouse gases such as carbon dioxide, methane and nitrous oxide. The only emissions from fuel cells are water in the form of steam and a small amount of carbon dioxide, which is not released at all if pure hydrogen is used as fuel. Fuel cells are assembled into assemblies and then into individual functional modules.

Fuel cells have no moving parts (at least not within the cell itself) and therefore do not obey Carnot's law. That is, they will have greater than 50% efficiency and are especially effective at low loads. Thus, fuel cell vehicles can become (and have already proven to be) more fuel efficient than conventional vehicles in real-world driving conditions.

The fuel cell produces a constant voltage electric current that can be used to drive the electric motor, lighting, and other electrical systems in the vehicle.

There are several types of fuel cells, differing in the chemical processes used. Fuel cells are usually classified by the type of electrolyte they use.

Some types of fuel cells are promising for power plant propulsion, while others are promising for portable devices or to drive cars.

1. Alkaline fuel cells (ALFC)

Alkaline fuel cell- This is one of the very first elements developed. Alkaline fuel cells (AFC) are one of the most studied technologies, used since the mid-60s of the twentieth century by NASA in the Apollo and Space Shuttle programs. On board these spacecraft, fuel cells produce electrical energy and potable water.

Alkaline fuel cells are one of the most efficient cells used to generate electricity, with power generation efficiency reaching up to 70%.

Alkaline fuel cells use an electrolyte, an aqueous solution of potassium hydroxide, contained in a porous, stabilized matrix. The potassium hydroxide concentration may vary depending on the operating temperature of the fuel cell, which ranges from 65°C to 220°C. The charge carrier in SHTE is the hydroxyl ion (OH-), moving from the cathode to the anode, where it reacts with hydrogen, producing water and electrons. The water produced at the anode moves back to the cathode, again generating hydroxyl ions there. As a result of this series of reactions taking place in the fuel cell, electricity and, as a by-product, heat are produced:

Reaction at the anode: 2H2 + 4OH- => 4H2O + 4e

Reaction at the cathode: O2 + 2H2O + 4e- => 4OH

General reaction of the system: 2H2 + O2 => 2H2O

The advantage of SHTE is that these fuel cells are the cheapest to produce, since the catalyst needed on the electrodes can be any of the substances that are cheaper than those used as catalysts for other fuel cells. In addition, SHTEs operate at relatively low temperatures and are among the most efficient.

One of the characteristic features of SHTE is its high sensitivity to CO2, which may be contained in fuel or air. CO2 reacts with the electrolyte, quickly poisons it, and greatly reduces the efficiency of the fuel cell. Therefore, the use of SHTE is limited to enclosed spaces, such as space and underwater vehicles; they operate on pure hydrogen and oxygen.

2. Molten carbonate fuel cells (MCFC)

Fuel cells with molten carbonate electrolyte are high temperature fuel cells. The high operating temperature allows the direct use of natural gas without a fuel processor and low calorific value fuel gas from industrial processes and other sources. This process was developed in the mid-60s of the twentieth century. Since then, production technology, performance and reliability have been improved.

The operation of RCFC differs from other fuel cells. These cells use an electrolyte made from a mixture of molten carbonate salts. Currently, two types of mixtures are used: lithium carbonate and potassium carbonate or lithium carbonate and sodium carbonate. To melt carbonate salts and achieve a high degree of ion mobility in the electrolyte, fuel cells with molten carbonate electrolyte operate at high temperatures (650°C). Efficiency varies between 60-80%.

When heated to a temperature of 650°C, the salts become a conductor for carbonate ions (CO32-). These ions pass from the cathode to the anode, where they combine with hydrogen to form water, carbon dioxide and free electrons. These electrons are sent through an external electrical circuit back to the cathode, generating electric current and heat as a by-product.

Reaction at the anode: CO32- + H2 => H2O + CO2 + 2e

Reaction at the cathode: CO2 + 1/2O2 + 2e- => CO32-

General reaction of the element: H2(g) + 1/2O2(g) + CO2(cathode) => H2O(g) + CO2(anode)

The high operating temperatures of molten carbonate electrolyte fuel cells have certain advantages. The advantage is the ability to use standard materials (stainless steel sheets and nickel catalyst on the electrodes). The waste heat can be used to produce high pressure steam. High reaction temperatures in the electrolyte also have their advantages. The use of high temperatures requires a long time to achieve optimal operating conditions, and the system responds more slowly to changes in energy consumption. These characteristics allow the use of fuel cell installations with molten carbonate electrolyte under constant power conditions. High temperatures prevent damage to the fuel cell by carbon monoxide, “poisoning,” etc.

Fuel cells with molten carbonate electrolyte are suitable for use in large stationary installations. Thermal power plants with an electrical output power of 2.8 MW are commercially produced. Installations with output power up to 100 MW are being developed.

3. Phosphoric acid fuel cells (PAFC)

Fuel cells based on phosphoric (orthophosphoric) acid became the first fuel cells for commercial use. This process was developed in the mid-60s of the twentieth century, tests have been carried out since the 70s of the twentieth century. The result was increased stability and performance and reduced cost.

Phosphoric (orthophosphoric) acid fuel cells use an electrolyte based on orthophosphoric acid (H3PO4) at concentrations up to 100%. The ionic conductivity of phosphoric acid is low at low temperatures, so these fuel cells are used at temperatures up to 150-220 °C.

The charge carrier in fuel cells of this type is hydrogen (H+, proton). A similar process occurs in proton exchange membrane fuel cells (PEMFCs), in which hydrogen supplied to the anode is split into protons and electrons. Protons travel through the electrolyte and combine with oxygen from the air at the cathode to form water. The electrons are sent through an external electrical circuit, thereby generating an electric current. Below are reactions that generate electric current and heat.

Reaction at the anode: 2H2 => 4H+ + 4e

Reaction at the cathode: O2(g) + 4H+ + 4e- => 2H2O

General reaction of the element: 2H2 + O2 => 2H2O

The efficiency of fuel cells based on phosphoric (orthophosphoric) acid is more than 40% when generating electrical energy. With combined production of heat and electricity, the overall efficiency is about 85%. In addition, given operating temperatures, waste heat can be used to heat water and generate atmospheric pressure steam.

The high performance of thermal power plants using fuel cells based on phosphoric (orthophosphoric) acid in the combined production of thermal and electrical energy is one of the advantages of this type of fuel cells. The units use carbon monoxide with a concentration of about 1.5%, which significantly expands the choice of fuel. Simple design, low degree of electrolyte volatility and increased stability are also advantages of such fuel cells.

Thermal power plants with electrical output power of up to 400 kW are commercially produced. Installations with a capacity of 11 MW have passed appropriate tests. Installations with output power up to 100 MW are being developed.

4. Proton exchange membrane fuel cells (PEMFC)

Proton exchange membrane fuel cells are considered the best type of fuel cells for generating power for vehicles, which can replace gasoline and diesel internal combustion engines. These fuel cells were first used by NASA for the Gemini program. Installations based on MOPFC with power from 1 W to 2 kW have been developed and demonstrated.

The electrolyte in these fuel cells is a solid polymer membrane (a thin film of plastic). When saturated with water, this polymer allows protons to pass through but does not conduct electrons.

The fuel is hydrogen, and the charge carrier is a hydrogen ion (proton). At the anode, the hydrogen molecule is split into a hydrogen ion (proton) and electrons. Hydrogen ions pass through the electrolyte to the cathode, and electrons move around the outer circle and produce electrical energy. Oxygen, which is taken from the air, is supplied to the cathode and combines with electrons and hydrogen ions to form water. The following reactions occur at the electrodes: Reaction at the anode: 2H2 + 4OH- => 4H2O + 4eReaction at the cathode: O2 + 2H2O + 4e- => 4OH Overall cell reaction: 2H2 + O2 => 2H2O Compared to other types of fuel cells, fuel cells with a proton exchange membrane produce more energy for a given volume or weight of the fuel cell. This feature allows them to be compact and lightweight. In addition, the operating temperature is less than 100°C, which allows you to quickly start operation. These characteristics, as well as the ability to quickly change energy output, are just a few that make these fuel cells a prime candidate for use in vehicles.

Another advantage is that the electrolyte is a solid rather than a liquid. It is easier to retain gases at the cathode and anode using a solid electrolyte, so such fuel cells are cheaper to produce. With a solid electrolyte, there are no orientation issues and fewer corrosion problems, increasing the longevity of the cell and its components.

5. Solid oxide fuel cells (SOFC)

Solid oxide fuel cells are the highest operating temperature fuel cells. The operating temperature can vary from 600°C to 1000°C, allowing the use of different types of fuel without special pre-treatment. To handle such high temperatures, the electrolyte used is a thin solid metal oxide on a ceramic base, often an alloy of yttrium and zirconium, which is a conductor of oxygen ions (O2-). The technology of using solid oxide fuel cells has been developing since the late 50s of the twentieth century and has two configurations: planar and tubular.

The solid electrolyte provides a sealed transition of gas from one electrode to another, while liquid electrolytes are located in a porous substrate. The charge carrier in fuel cells of this type is the oxygen ion (O2-). At the cathode, oxygen molecules from the air are separated into an oxygen ion and four electrons. Oxygen ions pass through the electrolyte and combine with hydrogen, creating four free electrons. The electrons are sent through an external electrical circuit, generating electric current and waste heat.

Reaction at the anode: 2H2 + 2O2- => 2H2O + 4e

Reaction at the cathode: O2 + 4e- => 2O2-

General reaction of the element: 2H2 + O2 => 2H2O

The efficiency of electrical energy production is the highest of all fuel cells - about 60%. In addition, high operating temperatures allow for the combined production of thermal and electrical energy to generate high-pressure steam. Combining a high-temperature fuel cell with a turbine makes it possible to create a hybrid fuel cell to increase the efficiency of generating electrical energy by up to 70%.

Solid oxide fuel cells operate at very high temperatures (600°C-1000°C), resulting in significant time required to reach optimal operating conditions and a slower system response to changes in energy consumption. At such high operating temperatures, no converter is required to recover hydrogen from the fuel, allowing the thermal power plant to operate with relatively impure fuels resulting from gasification of coal or waste gases, etc. The fuel cell is also excellent for high power applications, including industrial and large central power plants. Modules with an electrical output power of 100 kW are commercially produced.

6. Direct methanol oxidation fuel cells (DOMFC)

Direct methanol oxidation fuel cells They are successfully used in the field of powering mobile phones, laptops, as well as to create portable power sources, which is what the future use of such elements is aimed at.

The design of fuel cells with direct oxidation of methanol is similar to the design of fuel cells with a proton exchange membrane (MEPFC), i.e. A polymer is used as an electrolyte, and a hydrogen ion (proton) is used as a charge carrier. But liquid methanol (CH3OH) oxidizes in the presence of water at the anode, releasing CO2, hydrogen ions and electrons, which are sent through an external electrical circuit, thereby generating an electric current. Hydrogen ions pass through the electrolyte and react with oxygen from the air and electrons from the external circuit to form water at the anode.

Reaction at the anode: CH3OH + H2O => CO2 + 6H+ + 6eReaction at the cathode: 3/2O2 + 6H+ + 6e- => 3H2O General reaction of the element: CH3OH + 3/2O2 => CO2 + 2H2O The development of such fuel cells has been carried out since the beginning of the 90s s of the twentieth century and their specific power and efficiency were increased to 40%.

These elements were tested in the temperature range of 50-120°C. Because of their low operating temperatures and the absence of the need for a converter, such fuel cells are a prime candidate for use in mobile phones and other consumer products, as well as in car engines. Their advantage is also their small size.

7. Polymer electrolyte fuel cells (PEFC)

In the case of polymer electrolyte fuel cells, the polymer membrane consists of polymer fibers with water regions in which conduction water ions H2O+ (proton, red) attaches to a water molecule. Water molecules pose a problem due to slow ion exchange. Therefore, a high concentration of water is required both in the fuel and at the outlet electrodes, which limits the operating temperature to 100°C.

8. Solid acid fuel cells (SFC)

In solid acid fuel cells, the electrolyte (CsHSO4) does not contain water. The operating temperature is therefore 100-300°C. The rotation of the SO42 oxyanions allows the protons (red) to move as shown in the figure. Typically, a solid acid fuel cell is a sandwich in which a very thin layer of solid acid compound is sandwiched between two electrodes that are tightly pressed together to ensure good contact. When heated, the organic component evaporates, exiting through the pores in the electrodes, maintaining the ability of multiple contacts between the fuel (or oxygen at the other end of the element), the electrolyte and the electrodes.

9. Comparison of the most important characteristics of fuel cells

Characteristics of fuel cells

Fuel cell type	Operating temperature	Power generation efficiency	Fuel type	Scope of application
				Medium and large installations
			Pure hydrogen	installations
			Pure hydrogen	Small installations
			Most hydrocarbon fuels	Small, medium and large installations
				Portable installations
			Pure hydrogen	Space researched
			Pure hydrogen	Small installations

10. Use of fuel cells in cars

In light of recent events related to overheating, fires and even explosions of laptops due to the fault of lithium-ion batteries, one cannot help but recall new alternative technologies, which, according to most experts, in the future will be able to supplement or replace today's traditional rechargeable batteries. We are talking about new power sources – fuel cells.

According to an empirical law formulated 40 years ago by one of the founders of Intel, Gordon Moore, processor performance doubles every 18 months. Batteries can't keep up with chips. Their capacity, according to experts, increases only by 10% per year.

The fuel cell operates on the basis of a cellular (porous) membrane that separates the anode and cathode spaces of the fuel cell. This membrane is coated on both sides with appropriate catalysts. Fuel is supplied to the anode; in this case, a methanol solution (methyl alcohol) is used. As a result of the chemical reaction of fuel decomposition, free charges are formed that penetrate through the membrane to the cathode. The electrical circuit is thus closed, and an electric current is created in it to power the device. This type of fuel cell is called Direct Methanol Fuel Cell (DMFC). The development of fuel cells began a long time ago, but the first results, which gave rise to talk about real competition with lithium-ion batteries, were obtained only in the last two years.

In 2004, there were about 35 manufacturers on the market for such devices, but only a few companies were able to declare significant success in this area. In January, Fujitsu presented its development - the battery had a thickness of 15 mm and contained 300 mg of a 30 percent methanol solution. A power of 15 W allowed it to power the laptop for 8 hours. A month later, a small company, PolyFuel, was the first to announce the launch of commercial production of the very membranes that should be equipped with fuel power supplies. And already in March, Toshiba demonstrated a prototype of a mobile PC running on fuel. The manufacturer stated that such a laptop can last five times longer than a laptop using a traditional battery.

In 2005, LG Chem announced the creation of its own fuel cell. About 5 years and 5 billion dollars were spent on its development. As a result, it was possible to create a device with a power of 25 W and a weight of 1 kg, connected to a laptop via a USB interface and ensuring its operation for 10 hours. This year, 2006, was also marked by a number of interesting developments. In particular, American developers from the company Ultracell demonstrated a fuel cell that provides a power of 25 W and is equipped with three replaceable cartridges with 67 percent methanol. It is capable of powering a laptop for 24 hours. The weight of the battery was about a kilogram, each cartridge weighed about 260 grams.

In addition to being able to provide greater capacity than lithium ion batteries, methanol batteries are non-explosive. The disadvantages include their rather high cost and the need to periodically change methanol cartridges.

Even if fuel batteries do not replace traditional ones, they will most likely be used in conjunction with them. According to experts, the fuel cell market in 2006 will be about $600 million, which is a fairly modest figure. However, by 2010, experts predict its threefold increase - up to 1.9 billion dollars.

Discussion of the article “Alcohol batteries are replacing lithium ones”

zemoneng

Holy shit, I found information about this device in a women's magazine.
Well, I’ll say a few words about this:
1: the inconvenience is that after 6-10 hours of operation, you will have to look for a new cartridge, which is expensive. Why should I spend money on this nonsense?
2: as far as I understand, after receiving energy from methyl alcohol, water should be released. A laptop and water are incompatible things.
3: why do you write in women's magazines? Judging by the comments “I don’t know anything.” and “What is this?”, this article is not at the level of a site dedicated to BEAUTIES.

Description:

This article examines in more detail their design, classification, advantages and disadvantages, scope of application, effectiveness, history of creation and modern prospects for use.

Using fuel cells to power buildings

Part 1

This article examines in more detail the principle of operation of fuel cells, their design, classification, advantages and disadvantages, scope of application, efficiency, history of creation and modern prospects for use. In the second part of the article, which will be published in the next issue of the ABOK magazine, provides examples of facilities where various types of fuel cells were used as sources of heat and power supply (or only power supply).

Water can be stored even in both directions in both compressed and liquefied form, but this is also slush, both of which are caused by significant technical problems. This is due to high pressures and extremely low temperatures due to liquefaction. For this reason, for example, a water fuel dispenser stand must be designed differently than we are used to; the end of the filling line connects the robotic arm to a valve on the car. Connecting and filling is quite dangerous, and therefore it is best if it happens without human presence.

Introduction

Fuel cells are a very efficient, reliable, durable and environmentally friendly way to generate energy.

Initially used only in the space industry, fuel cells are now increasingly used in a variety of areas - as stationary power plants, heat and power supplies for buildings, vehicle engines, power supplies for laptops and mobile phones. Some of these devices are laboratory prototypes, some are undergoing pre-production testing or are used for demonstration purposes, but many models are mass-produced and used in commercial projects.

Such a device is in a test run at the airport in Munich, try driving here with individual cars and buses. A high kilogram of mileage is cool, but in practice it is just as important as how many kilograms it will cost, and how much space in the car a strong, insulated fuel tank will take up. Some other problems with water: - create a complex air bath - problem with garages, auto repair shops, etc. - thanks to a small molecule that penetrates every bottleneck, screws and valves - compression and liquefaction require significant energy expenditure.

A fuel cell (electrochemical generator) is a device that converts the chemical energy of fuel (hydrogen) into electrical energy directly through an electrochemical reaction, in contrast to traditional technologies that use the combustion of solid, liquid and gaseous fuels. Direct electrochemical conversion of fuel is very effective and attractive from an environmental point of view, since the operation process produces a minimal amount of pollutants and there is no strong noise or vibration.

The special pressures, compression and set of necessary safety measures have a very good value in the assessment at the end of the water, compared to liquid hydrocarbon fuels, which are produced using lightweight, non-pressurized containers. Therefore, perhaps very urgent circumstances may contribute to his truly flattering pleasure.

In the near future, car manufacturers are still looking for cheaper and relatively less dangerous liquid fuels. The hot melt may be methanol, which can be extracted relatively easily. Its main and only problem is toxicity, on the other hand, like water, methane can be used both in internal combustion engines and in a certain type of fuel chain. It also has some advantages in internal combustion engines, including in terms of emissions.

From a practical point of view, a fuel cell resembles a conventional voltaic battery. The difference is that the battery is initially charged, i.e. filled with “fuel”. During operation, “fuel” is consumed and the battery is discharged. Unlike a battery, a fuel cell uses fuel supplied from an external source to produce electrical energy (Fig. 1).

In this regard, the water can rise to relatively unexpected and yet capable competition. The fuel cell is a source of current generated by an electrochemical reaction. Unlike all our known batteries, it receives reagents and discharges waste constantly, so unlike a battery, it is virtually inexhaustible. Although there are many different types, the following diagram of a hydrogen fuel cell helps us understand how it works.

The fuel is supplied to the positive electrode, where it is oxidized. O2 oxygen enters the negative electrode and can be reduced.

It was even possible to develop a fuel cell that directly burned coal. Since the work of scientists from the Lawrence Livermore Laboratory, which was able to test a fuel cell that directly converts coal into electricity, could be a very important milestone in the development of energy, we will stop at a few words. Coal soil up to 1 micron in size is mixed at 750-850 ° C with molten lithium, sodium or potassium carbonate.

To produce electrical energy, not only pure hydrogen can be used, but also other hydrogen-containing raw materials, for example, natural gas, ammonia, methanol or gasoline. Ordinary air is used as a source of oxygen, also necessary for the reaction.

When using pure hydrogen as a fuel, the reaction products, in addition to electrical energy, are heat and water (or water vapor), i.e., gases that cause air pollution or cause the greenhouse effect are not emitted into the atmosphere. If a hydrogen-containing feedstock, such as natural gas, is used as a fuel, other gases such as carbon and nitrogen oxides will be a by-product of the reaction, but the amount is much lower than when burning the same amount of natural gas.

Then everything is done in the standard way according to the above diagram: oxygen in the air reacts with carbon to carbon dioxide, and energy is released in the form of electricity. Although we know of several different types of fuel cells, they all work according to the principle described. This is a kind of controlled combustion. When we mix hydrogen with oxygen, we get a fission mixture that explodes to form water. Energy is released in the form of heat. A hydrogen fuel cell has the same reaction, the product is also water, but the energy is released as electricity.

The process of chemically converting fuel to produce hydrogen is called reforming, and the corresponding device is called a reformer.

Advantages and disadvantages of fuel cells

Fuel cells are more energy efficient than internal combustion engines because there is no thermodynamic energy efficiency limitation for fuel cells. The efficiency of fuel cells is 50%, while the efficiency of internal combustion engines is 12-15%, and the efficiency of steam turbine power plants does not exceed 40%. By using heat and water, the efficiency of fuel cells is further increased.

The big advantage of a fuel cell is that it produces electricity from fuel one way or another directly, without an intermediate thermal plant, so emissions are lower and efficiency is higher. It reaches 70%, while as a standard we achieve 40% conversion of coal to electricity. Why don't we build giant fuel cells instead of power plants? A fuel cell is a rather complex device that operates at high temperatures, so the requirements for electrode materials and the electrolyte itself are high.

Unlike, for example, internal combustion engines, the efficiency of fuel cells remains very high even when they are not operating at full power. In addition, the power of fuel cells can be increased by simply adding individual units, while the efficiency does not change, i.e. large installations are just as efficient as small ones. These circumstances make it possible to very flexibly select the composition of equipment in accordance with the wishes of the customer and ultimately lead to a reduction in equipment costs.

Electrolytes include, for example, ion exchange membranes or conductive ceramic materials, or rather expensive materials, or phosphoric acid, sodium hydroxide or molten alkali metal carbonates, which are very aggressive to alter tissue. It was this difficulty that, after the initial enthusiasm in the twentieth century, fuel cells, outside of the space program, were not more significant.

Interest then waned again when it became clear that wider use was beyond the capabilities of the technology at the time. However, over the past thirty years, development has not stopped, new materials and concepts have appeared, and our priorities have changed - we now pay much more attention to protecting the environment than then. Therefore, we are experiencing something of a renaissance in fuel cells, which are increasingly being used in many areas. There are 200 such devices around the world. For example, they serve as a backup device where network failure could cause serious problems - for example, in hospitals or military establishments.

An important advantage of fuel cells is their environmental friendliness. Fuel cell emissions are so low that in some areas of the United States, their operation does not require special approval from government air quality regulators.

Fuel cells can be placed directly in a building, reducing losses during energy transportation, and the heat generated as a result of the reaction can be used to supply heat or hot water to the building. Autonomous sources of heat and electricity can be very beneficial in remote areas and in regions characterized by a shortage of electricity and its high cost, but at the same time there are reserves of hydrogen-containing raw materials (oil, natural gas).

They are used in very remote locations where it is easier to transport fuel than to stretch the cable. They may also start competing with power plants. This is the most powerful module installed in the world.

Almost every major automaker is working on a fuel cell electric vehicle project. It appears to be a much more promising concept than a conventional battery electric car because it doesn't require a long charging time and the infrastructure change required is not as extensive.

The advantages of fuel cells are also the availability of fuel, reliability (there are no moving parts in a fuel cell), durability and ease of operation.

One of the main disadvantages of fuel cells today is their relatively high cost, but this disadvantage can soon be overcome - more and more companies are producing commercial samples of fuel cells, they are constantly being improved, and their cost is decreasing.

The growing importance of fuel cells is also illustrated by the fact that the Bush administration has recently rethought its approach to automobile development, and the funds it spent on developing cars with the best possible mileage are now transferred to fuel cell projects. Development financing does not simply remain in the hands of the state.

Of course, the new drive concept is not limited to passenger cars, but we can also find it in mass transit. Fuel cell buses carry passengers on the streets of several cities. Along with car drives, there are a number of smaller ones on the market, such as powered computers, video cameras and mobile phones. In the picture we see a fuel cell to power the traffic alarm.

The most effective way is to use pure hydrogen as a fuel, but this will require the creation of a special infrastructure for its production and transportation. Currently, all commercial models use natural gas and similar fuels. Motor vehicles can use regular gasoline, which will allow maintaining the existing developed network of gas stations. However, the use of such fuel leads to harmful emissions into the atmosphere (albeit very low) and complicates (and therefore increases the cost of) the fuel cell. In the future, the possibility of using environmentally friendly renewable energy sources (for example, solar or wind energy) to decompose water into hydrogen and oxygen using electrolysis, and then converting the resulting fuel in a fuel cell, is being considered. Such combined plants, operating in a closed cycle, can represent a completely environmentally friendly, reliable, durable and efficient source of energy.

Worth mentioning is the use of fuel cells in landfills, where they can burn off gas emissions and help improve the environment in addition to producing electricity. Several test facilities are currently operational, and an extensive installation program of these facilities is being prepared at 150 test sites across the United States. Fuel cells are simply useful devices, and we're sure to see them more and more often.

Chemists have developed a catalyst that could replace expensive platinum in fuel cells. Instead, he uses about two hundred thousand cheap iron. Fuel cells convert chemical energy into electrical energy. Electrons in different molecules have different energies. The energy difference between one molecule and another can be used as a source of energy. Just find a reaction in which electrons move from higher to lower. Such reactions are the main source of energy for living organisms.

Another feature of fuel cells is that they are most efficient when using both electrical and thermal energy simultaneously. However, not every facility has the opportunity to use thermal energy. If fuel cells are used only to generate electrical energy, their efficiency decreases, although it exceeds the efficiency of “traditional” installations.

The best known is respiration, which converts sugars into carbon dioxide and water. In a hydrogen fuel cell, two-atom hydrogen molecules combine with oxygen to form water. The energy difference between the electrons in hydrogen and water is used to generate electricity. Hydrogen cells are probably the most commonly used to drive cars today. Their massive expansion also prevents small hooking.

In order for an energetically rich reaction to take place, a catalyst is needed. Catalysts are molecules that increase the likelihood of a reaction occurring. Without a catalyst, it could also work, but less often or more slowly. Hydrogen cells use precious platinum as a catalyst.

History and modern use of fuel cells

The principle of operation of fuel cells was discovered in 1839. The English scientist William Robert Grove (1811-1896) discovered that the process of electrolysis - the decomposition of water into hydrogen and oxygen through electric current - is reversible, i.e. hydrogen and oxygen can be combined into water molecules without combustion, but with the release of heat and electric current. Grove called the device in which such a reaction was possible a “gas battery,” which was the first fuel cell.

The same reaction that occurs in hydrogen cells also occurs in living cells. Enzymes are relatively large molecules made up of amino acids that can be combined like Lego bricks. Each enzyme has a so-called active site, where the reaction is accelerated. Molecules other than amino acids are also often present at the active site.

In the case of hydrogen acid, this is iron. A team of chemists, led by Morris Bullock of the US Department of Energy's Pacific Laboratory, was able to mimic the reaction at the hydrogenation active site. Like an enzyme, hydrogenation is sufficient for platinum with iron. It can split 0.66 to 2 hydrogen molecules per second. The difference in voltage ranges from 160 to 220 thousand volts. Both are comparable to current platinum catalysts used in hydrogen cells. The reaction is carried out at room temperature.

The active development of technologies for the use of fuel cells began after the Second World War, and it is associated with the aerospace industry. At this time, a search was underway for an effective and reliable, but at the same time quite compact, source of energy. In the 1960s, NASA (National Aeronautics and Space Administration, NASA) specialists chose fuel cells as a power source for the spacecraft of the Apollo (manned flights to the Moon), Apollo-Soyuz, Gemini and Skylab programs. . The Apollo spacecraft used three 1.5 kW (2.2 kW peak) plants using cryogenic hydrogen and oxygen to produce electricity, heat and water. The mass of each installation was 113 kg. These three cells operated in parallel, but the energy generated by one unit was sufficient for a safe return. Over the course of 18 flights, the fuel cells operated for a total of 10,000 hours without any failures. Currently, fuel cells are used in the Space Shuttle, which uses three 12 W units to generate all the electrical energy on board the spacecraft (Fig. 2). The water obtained as a result of the electrochemical reaction is used for drinking water and also for cooling equipment.

One kilogram of iron costs 0.5 CZK. Therefore, iron is 200 thousand times cheaper than platinum. In the future, fuel cells may be cheaper. Expensive platinum is not the only reason why they should not be used, at least not on a large scale. Handling it is difficult and dangerous.

If hydrogen chambers were to be used in bulk to drive cars, they would have to build the same infrastructure as gasoline and diesel. In addition, copper is needed to produce the electric motors that power hydrogen-powered cars. However, this does not mean that fuel cells are useless. When there's oil, maybe we have no choice but to run on hydrogen.

In our country, work was also carried out on the creation of fuel cells for use in astronautics. For example, fuel cells were used to power the Soviet Buran reusable spacecraft.

Development of methods for the commercial use of fuel cells began in the mid-1960s. These developments were partially funded by government organizations.

Currently, the development of technologies for the use of fuel cells is proceeding in several directions. This is the creation of stationary power plants on fuel cells (both for centralized and decentralized energy supply), power plants for vehicles (samples of cars and buses on fuel cells have been created, including in our country) (Fig. 3), and also power supplies for various mobile devices (laptop computers, mobile phones, etc.) (Fig. 4).

Examples of the use of fuel cells in various fields are given in Table. 1.

One of the first commercial fuel cell models designed for autonomous heat and power supply to buildings was the PC25 Model A manufactured by ONSI Corporation (now United Technologies, Inc.). This fuel cell with a rated power of 200 kW is a type of cell with an electrolyte based on phosphoric acid (Phosphoric Acid Fuel Cells, PAFC). The number “25” in the model name means the serial number of the design. Most previous models were experimental or test units, such as the 12.5 kW "PC11" model introduced in the 1970s. The new models increased the power extracted from an individual fuel cell, and also reduced the cost per kilowatt of energy produced. Currently, one of the most efficient commercial models is the PC25 Model C fuel cell. Like Model A, this is a fully automatic 200 kW PAFC fuel cell designed for on-site installation as a self-contained source of heat and power. Such a fuel cell can be installed outside a building. Externally, it is a parallelepiped 5.5 m long, 3 m wide and high, weighing 18,140 kg. The difference from previous models is an improved reformer and a higher current density.

Table 1 Field of application of fuel cells

Region applications Nominal power Examples of using Stationary installations 5–250 kW and higher Autonomous sources of heat and power supply for residential, public and industrial buildings, uninterruptible power supplies, backup and emergency power supply sources Portable installations 1–50 kW Road signs, freight and refrigerated railroad trucks, wheelchairs, golf carts, spaceships and satellites Mobile installations 25–150 kW Cars (prototypes were created, for example, by DaimlerCrysler, FIAT, Ford, General Motors, Honda, Hyundai, Nissan, Toyota, Volkswagen, VAZ), buses ( e.g. "MAN", "Neoplan", "Renault") and other vehicles, warships and submarines Microdevices 1–500 W Mobile phones, laptops, personal digital assistants (PDAs), various consumer electronic devices, modern military devices

In some types of fuel cells, the chemical process can be reversed: by applying a potential difference to the electrodes, water can be broken down into hydrogen and oxygen, which collect on the porous electrodes. When a load is connected, such a regenerative fuel cell will begin to produce electrical energy.

A promising direction for the use of fuel cells is their use in conjunction with renewable energy sources, for example, photovoltaic panels or wind power plants. This technology allows us to completely avoid air pollution. A similar system is planned to be created, for example, at the Adam Joseph Lewis Training Center in Oberlin (see ABOK, 2002, No. 5, p. 10). Currently, solar panels are used as one of the energy sources in this building. Together with NASA specialists, a project has been developed for using photovoltaic panels to produce hydrogen and oxygen from water by electrolysis. The hydrogen is then used in fuel cells to produce electrical energy and. This will allow the building to maintain the functionality of all systems during cloudy days and at night.

Operating principle of fuel cells

Let's consider the principle of operation of a fuel cell using the example of a simple element with a proton exchange membrane (Proton Exchange Membrane, PEM). Such a cell consists of a polymer membrane placed between an anode (positive electrode) and a cathode (negative electrode) along with anode and cathode catalysts. The polymer membrane is used as an electrolyte. The diagram of the PEM element is shown in Fig. 5.

A proton exchange membrane (PEM) is a thin (about 2-7 sheets of paper thick) solid organic compound. This membrane functions as an electrolyte: it separates a substance into positively and negatively charged ions in the presence of water.

An oxidation process occurs at the anode, and a reduction process occurs at the cathode. The anode and cathode in a PEM cell are made of a porous material, which is a mixture of carbon and platinum particles. Platinum acts as a catalyst that promotes the dissociation reaction. The anode and cathode are made porous for the free passage of hydrogen and oxygen through them, respectively.

The anode and cathode are placed between two metal plates, which supply hydrogen and oxygen to the anode and cathode, and remove heat and water, as well as electrical energy.

Hydrogen molecules pass through channels in the plate to the anode, where the molecules are decomposed into individual atoms (Fig. 6).

	Figure 5. () Schematic of a fuel cell with a proton exchange membrane (PEM cell)
	Figure 6. () Hydrogen molecules pass through channels in the plate to the anode, where the molecules decompose into individual atoms
	Figure 7. () As a result of chemisorption in the presence of a catalyst, hydrogen atoms are converted into protons
	Figure 8. () Positively charged hydrogen ions diffuse through the membrane to the cathode, and a flow of electrons is directed to the cathode through an external electrical circuit to which the load is connected
	Figure 9. () Oxygen supplied to the cathode, in the presence of a catalyst, enters into a chemical reaction with hydrogen ions from the proton exchange membrane and electrons from the external electrical circuit. As a result of a chemical reaction, water is formed

Then, as a result of chemisorption in the presence of a catalyst, hydrogen atoms, each giving up one electron e –, are converted into positively charged hydrogen ions H +, i.e. protons (Fig. 7).

Positively charged hydrogen ions (protons) diffuse through the membrane to the cathode, and the flow of electrons is directed to the cathode through an external electrical circuit to which the load (consumer of electrical energy) is connected (Fig. 8).

Oxygen supplied to the cathode, in the presence of a catalyst, enters into a chemical reaction with hydrogen ions (protons) from the proton exchange membrane and electrons from the external electrical circuit (Fig. 9). As a result of a chemical reaction, water is formed.

The chemical reaction in other types of fuel cells (for example, with an acid electrolyte, which uses a solution of orthophosphoric acid H 3 PO 4) is absolutely identical to the chemical reaction in a fuel cell with a proton exchange membrane.

In any fuel cell, some of the energy from a chemical reaction is released as heat.

The flow of electrons in an external circuit is a direct current that is used to do work. Opening the external circuit or stopping the movement of hydrogen ions stops the chemical reaction.

The amount of electrical energy produced by a fuel cell depends on the type of fuel cell, geometric dimensions, temperature, gas pressure. A separate fuel cell provides an EMF of less than 1.16 V. The size of fuel cells can be increased, but in practice several elements connected into batteries are used (Fig. 10).

Fuel cell design

Let's look at the design of a fuel cell using the PC25 Model C as an example. The fuel cell diagram is shown in Fig. eleven.

The PC25 Model C fuel cell consists of three main parts: the fuel processor, the actual power generation section and the voltage converter.

The main part of the fuel cell, the power generation section, is a battery composed of 256 individual fuel cells. The fuel cell electrodes contain a platinum catalyst. These cells produce a constant electrical current of 1,400 amperes at 155 volts. The battery dimensions are approximately 2.9 m in length and 0.9 m in width and height.

Since the electrochemical process takes place at a temperature of 177 °C, it is necessary to heat the battery at the time of start-up and remove heat from it during operation. To achieve this, the fuel cell includes a separate water circuit, and the battery is equipped with special cooling plates.

The fuel processor converts natural gas into hydrogen needed for an electrochemical reaction. This process is called reforming. The main element of the fuel processor is the reformer. In the reformer, natural gas (or other hydrogen-containing fuel) reacts with water vapor at high temperature (900 °C) and high pressure in the presence of a nickel catalyst. In this case, the following chemical reactions occur:

CH 4 (methane) + H 2 O 3H 2 + CO

(the reaction is endothermic, with heat absorption);

CO + H 2 O H 2 + CO 2

(the reaction is exothermic, releasing heat).

The overall reaction is expressed by the equation:

CH 4 (methane) + 2H 2 O 4H 2 + CO 2

(the reaction is endothermic, with heat absorption).

To provide the high temperature required to convert natural gas, a portion of the spent fuel from the fuel cell stack is directed to a burner, which maintains the required reformer temperature.

The steam required for reforming is generated from condensate generated during operation of the fuel cell. This uses the heat removed from the battery of fuel cells (Fig. 12).

The fuel cell stack produces an intermittent direct current that is low voltage and high current. A voltage converter is used to convert it to industrial standard AC current. In addition, the voltage converter unit includes various control devices and safety interlock circuits that allow the fuel cell to be turned off in the event of various failures.

In such a fuel cell, approximately 40% of the fuel energy can be converted into electrical energy. Approximately the same amount, about 40% of the fuel energy, can be converted into thermal energy, which is then used as a heat source for heating, hot water supply and similar purposes. Thus, the total efficiency of such an installation can reach 80%.

An important advantage of such a source of heat and electricity is the possibility of its automatic operation. For maintenance, the owners of the facility where the fuel cell is installed do not need to maintain specially trained personnel - periodic maintenance can be carried out by employees of the operating organization.

Types of fuel cells

Currently, several types of fuel cells are known, differing in the composition of the electrolyte used. The following four types are most widespread (Table 2):

1. Fuel cells with a proton exchange membrane (Proton Exchange Membrane Fuel Cells, PEMFC).

2. Fuel cells based on orthophosphoric acid (Phosphoric Acid Fuel Cells, PAFC).

3. Fuel cells based on molten carbonate (Molten Carbonate Fuel Cells, MCFC).

4. Solid Oxide Fuel Cells (SOFC). Currently, the largest fleet of fuel cells is based on PAFC technology.

One of the key characteristics of different types of fuel cells is operating temperature. In many ways, it is the temperature that determines the area of ​​application of fuel cells. For example, high temperatures are critical for laptops, so proton exchange membrane fuel cells with low operating temperatures are being developed for this market segment.

For autonomous power supply of buildings, fuel cells of high installed power are required, and at the same time there is the possibility of using thermal energy, so other types of fuel cells can be used for these purposes.

Proton exchange membrane fuel cells (PEMFC)

These fuel cells operate at relatively low operating temperatures (60-160 °C). They have a high power density, allow you to quickly adjust the output power, and can be turned on quickly. The disadvantage of this type of element is the high requirements for fuel quality, since contaminated fuel can damage the membrane. The rated power of this type of fuel cells is 1-100 kW.

Proton exchange membrane fuel cells were originally developed by General Electric in the 1960s for NASA. This type of fuel cell uses a solid-state polymer electrolyte called a Proton Exchange Membrane (PEM). Protons can move through the proton exchange membrane, but electrons cannot pass through it, resulting in a potential difference between the cathode and anode. Because of their simplicity and reliability, such fuel cells were used as a power source on the manned Gemini spacecraft.

This type of fuel cell is used as a power source for a wide range of different devices, including prototypes and prototypes, from mobile phones to buses and stationary power systems. The low operating temperature allows such cells to be used to power various types of complex electronic devices. Their use is less effective as a source of heat and electricity supply to public and industrial buildings, where large volumes of thermal energy are required. At the same time, such elements are promising as an autonomous source of power supply for small residential buildings such as cottages built in regions with a hot climate.

table 2 Types of fuel cells

Item type Workers temperature, °C Efficiency output electrical energy),% Total Efficiency, % Fuel cells with proton exchange membrane (PEMFC) 60–160 30–35 50–70 Fuel cells based on phosphorus (phosphoric) acid (PAFC) 150–200 35 70–80 Fuel cells based molten carbonate (MCFC) 600–700 45–50 70–80 Solid oxide fuel cells (SOFC) 700–1 000 50–60 70–80

Phosphoric Acid Fuel Cells (PAFC)

Tests of fuel cells of this type were carried out already in the early 1970s. Operating temperature range - 150-200 °C. The main area of ​​application is autonomous sources of heat and electricity supply of medium power (about 200 kW).

These fuel cells use a phosphoric acid solution as the electrolyte. The electrodes are made of paper coated with carbon in which a platinum catalyst is dispersed.

The electrical efficiency of PAFC fuel cells is 37-42%. However, since these fuel cells operate at a fairly high temperature, it is possible to use the steam generated as a result of operation. In this case, the overall efficiency can reach 80%.

To produce energy, hydrogen-containing feedstock must be converted into pure hydrogen through a reforming process. For example, if gasoline is used as fuel, it is necessary to remove sulfur-containing compounds, since sulfur can damage the platinum catalyst.

PAFC fuel cells were the first commercial fuel cells to be used economically. The most common model was the 200 kW PC25 fuel cell manufactured by ONSI Corporation (now United Technologies, Inc.) (Fig. 13). For example, these elements are used as a source of thermal and electrical energy in the police station in Central Park in New York or as an additional source of energy in the Conde Nast Building & Four Times Square. The largest installation of this type is being tested as an 11 MW power plant located in Japan.

Phosphoric acid fuel cells are also used as an energy source in vehicles. For example, in 1994, H-Power Corp., Georgetown University and the US Department of Energy equipped a bus with a 50 kW power plant.

Molten Carbonate Fuel Cells (MCFC)

Fuel cells of this type operate at very high temperatures - 600-700 °C. These operating temperatures allow the fuel to be used directly in the cell itself, without the use of a separate reformer. This process was called “internal reform”. It makes it possible to significantly simplify the design of the fuel cell.

Fuel cells based on molten carbonate require a significant start-up time and do not allow for prompt adjustment of output power, so their main area of ​​application is large stationary sources of thermal and electrical energy. However, they are characterized by high fuel conversion efficiency - 60% electrical efficiency and up to 85% overall efficiency.

In this type of fuel cell, the electrolyte consists of potassium carbonate and lithium carbonate salts heated to approximately 650 °C. Under these conditions, the salts are in a molten state, forming an electrolyte. At the anode, hydrogen reacts with CO 3 ions, forming water, carbon dioxide and releasing electrons, which are sent to the external circuit, and at the cathode, oxygen interacts with carbon dioxide and electrons from the external circuit, again forming CO 3 ions.

Laboratory samples of fuel cells of this type were created in the late 1950s by Dutch scientists G. H. J. Broers and J. A. A. Ketelaar. In the 1960s, engineer Francis T. Bacon, a descendant of the famous English writer and scientist of the 17th century, worked with these cells, which is why MCFC fuel cells are sometimes called Bacon cells. In NASA's Apollo, Apollo-Soyuz and Scylab programs, these fuel cells were used as a source of energy supply (Fig. 14). During these same years, the US military department tested several samples of MCFC fuel cells produced by Texas Instruments, which used military grade gasoline as fuel. In the mid-1970s, the US Department of Energy began research to create a stationary molten carbonate fuel cell suitable for practical applications. In the 1990s, a number of commercial installations with rated power up to 250 kW were introduced, for example at the US Naval Air Station Miramar in California. In 1996, FuelCell Energy, Inc. launched a pre-production 2 MW plant in Santa Clara, California.

Solid-state oxide fuel cells (SOFC)

Solid-state oxide fuel cells are simple in design and operate at very high temperatures - 700-1,000 °C. Such high temperatures allow the use of relatively “dirty”, unrefined fuel. The same features as those of fuel cells based on molten carbonate determine a similar field of application - large stationary sources of thermal and electrical energy.

Solid oxide fuel cells are structurally different from fuel cells based on PAFC and MCFC technologies. The anode, cathode and electrolyte are made of special grades of ceramics. The most commonly used electrolyte is a mixture of zirconium oxide and calcium oxide, but other oxides can also be used. The electrolyte forms a crystal lattice coated on both sides with porous electrode material. Structurally, such elements are made in the form of tubes or flat boards, which makes it possible to use technologies widely used in the electronics industry in their production. As a result, solid-state oxide fuel cells can operate at very high temperatures, making them advantageous for producing both electrical and thermal energy.

At high operating temperatures, oxygen ions are formed at the cathode, which migrate through the crystal lattice to the anode, where they interact with hydrogen ions, forming water and releasing free electrons. In this case, hydrogen is separated from natural gas directly in the cell, i.e. there is no need for a separate reformer.

The theoretical foundations for the creation of solid-state oxide fuel cells were laid in the late 1930s, when Swiss scientists Emil Bauer and H. Preis experimented with zirconium, yttrium, cerium, lanthanum and tungsten, using them as electrolytes.

The first prototypes of such fuel cells were created in the late 1950s by a number of American and Dutch companies. Most of these companies soon abandoned further research due to technological difficulties, but one of them, Westinghouse Electric Corp. (now Siemens Westinghouse Power Corporation), continued work. The company is currently accepting pre-orders for a commercial model of a tubular solid-state oxide fuel cell, expected to be available this year (Figure 15). The market segment of such elements is stationary installations for the production of thermal and electrical energy with a capacity of 250 kW to 5 MW.

SOFC fuel cells have demonstrated very high reliability. For example, a prototype fuel cell manufactured by Siemens Westinghouse has achieved 16,600 hours of operation and continues to operate, making it the longest continuous fuel cell life in the world.

The high-temperature, high-pressure operating mode of SOFC fuel cells allows for the creation of hybrid plants in which fuel cell emissions drive gas turbines used to generate electrical power. The first such hybrid installation is operating in Irvine, California. The rated power of this installation is 220 kW, of which 200 kW from the fuel cell and 20 kW from the microturbine generator.

Fuel cell is an electrochemical device similar to a galvanic cell, but differs from it in that the substances for the electrochemical reaction are supplied to it from the outside - in contrast to the limited amount of energy stored in a galvanic cell or battery.

Rice. 1. Some fuel cells

Fuel cells convert the chemical energy of fuel into electricity, bypassing ineffective combustion processes that occur with large losses. They convert hydrogen and oxygen into electricity through a chemical reaction. As a result of this process, water is formed and a large amount of heat is released. A fuel cell is very similar to a battery that can be charged and then use the stored electrical energy. The inventor of the fuel cell is considered to be William R. Grove, who invented it back in 1839. This fuel cell used a sulfuric acid solution as an electrolyte and hydrogen as a fuel, which was combined with oxygen in an oxidizing agent. Until recently, fuel cells were used only in laboratories and on spacecraft.

Unlike other power generators, such as internal combustion engines or turbines powered by gas, coal, fuel oil, etc., fuel cells do not burn fuel. This means no noisy high-pressure rotors, no loud exhaust noise, no vibrations. Fuel cells produce electricity through a silent electrochemical reaction. Another feature of fuel cells is that they convert the chemical energy of the fuel directly into electricity, heat and water.

Fuel cells are highly efficient and do not produce large amounts of greenhouse gases such as carbon dioxide, methane and nitrous oxide. The only emissions from fuel cells are water in the form of steam and a small amount of carbon dioxide, which is not released at all if pure hydrogen is used as fuel. Fuel cells are assembled into assemblies and then into individual functional modules.

Fuel cells have no moving parts (at least not within the cell itself) and therefore do not obey Carnot's law. That is, they will have greater than 50% efficiency and are especially effective at low loads. Thus, fuel cell vehicles can become (and have already proven to be) more fuel efficient than conventional vehicles in real-world driving conditions.

The fuel cell produces a constant voltage electric current that can be used to drive the electric motor, lighting, and other electrical systems in the vehicle.

There are several types of fuel cells, differing in the chemical processes used. Fuel cells are usually classified by the type of electrolyte they use.

Some types of fuel cells are promising for power plant propulsion, while others are promising for portable devices or to drive cars.

1. Alkaline fuel cells (ALFC)

Alkaline fuel cell- This is one of the very first elements developed. Alkaline fuel cells (AFC) are one of the most studied technologies, used since the mid-60s of the twentieth century by NASA in the Apollo and Space Shuttle programs. On board these spacecraft, fuel cells produce electrical energy and potable water.

Alkaline fuel cells are one of the most efficient elements used to generate electricity, with power generation efficiency reaching up to 70%.

Alkaline fuel cells use an electrolyte, an aqueous solution of potassium hydroxide, contained in a porous, stabilized matrix. The potassium hydroxide concentration may vary depending on the operating temperature of the fuel cell, which ranges from 65°C to 220°C. The charge carrier in SHTE is the hydroxyl ion (OH-), moving from the cathode to the anode, where it reacts with hydrogen, producing water and electrons. The water produced at the anode moves back to the cathode, again generating hydroxyl ions there. As a result of this series of reactions taking place in the fuel cell, electricity and, as a by-product, heat are produced:

Reaction at the anode: 2H2 + 4OH- => 4H2O + 4e

Reaction at the cathode: O2 + 2H2O + 4e- => 4OH

General reaction of the system: 2H2 + O2 => 2H2O

The advantage of SHTE is that these fuel cells are the cheapest to produce, since the catalyst needed on the electrodes can be any of the substances that are cheaper than those used as catalysts for other fuel cells. In addition, SHTEs operate at relatively low temperatures and are among the most efficient.

One of the characteristic features of SHTE is its high sensitivity to CO2, which may be contained in fuel or air. CO2 reacts with the electrolyte, quickly poisons it, and greatly reduces the efficiency of the fuel cell. Therefore, the use of SHTE is limited to enclosed spaces, such as space and underwater vehicles; they operate on pure hydrogen and oxygen.

2. Molten carbonate fuel cells (MCFC)

Fuel cells with molten carbonate electrolyte are high temperature fuel cells. The high operating temperature allows the direct use of natural gas without a fuel processor and low calorific value fuel gas from industrial processes and other sources. This process was developed in the mid-60s of the twentieth century. Since then, production technology, performance and reliability have been improved.

The operation of RCFC differs from other fuel cells. These cells use an electrolyte made from a mixture of molten carbonate salts. Currently, two types of mixtures are used: lithium carbonate and potassium carbonate or lithium carbonate and sodium carbonate. To melt carbonate salts and achieve a high degree of ion mobility in the electrolyte, fuel cells with molten carbonate electrolyte operate at high temperatures (650°C). Efficiency varies between 60-80%.

When heated to a temperature of 650°C, the salts become a conductor for carbonate ions (CO32-). These ions pass from the cathode to the anode, where they combine with hydrogen to form water, carbon dioxide and free electrons. These electrons are sent through an external electrical circuit back to the cathode, generating electric current and heat as a by-product.

Reaction at the anode: CO32- + H2 => H2O + CO2 + 2e

Reaction at the cathode: CO2 + 1/2O2 + 2e- => CO32-

General reaction of the element: H2(g) + 1/2O2(g) + CO2(cathode) => H2O(g) + CO2(anode)

The high operating temperatures of molten carbonate electrolyte fuel cells have certain advantages. The advantage is the ability to use standard materials (stainless steel sheets and nickel catalyst on the electrodes). The waste heat can be used to produce high pressure steam. High reaction temperatures in the electrolyte also have their advantages. The use of high temperatures requires a long time to achieve optimal operating conditions, and the system responds more slowly to changes in energy consumption. These characteristics allow the use of fuel cell installations with molten carbonate electrolyte under constant power conditions. High temperatures prevent damage to the fuel cell by carbon monoxide, “poisoning,” etc.

Fuel cells with molten carbonate electrolyte are suitable for use in large stationary installations. Thermal power plants with an electrical output power of 2.8 MW are commercially produced. Installations with output power up to 100 MW are being developed.

3. Phosphoric acid fuel cells (PAFC)

Fuel cells based on phosphoric (orthophosphoric) acid became the first fuel cells for commercial use. This process was developed in the mid-60s of the twentieth century, tests have been carried out since the 70s of the twentieth century. The result was increased stability and performance and reduced cost.

Phosphoric (orthophosphoric) acid fuel cells use an electrolyte based on orthophosphoric acid (H3PO4) at concentrations up to 100%. The ionic conductivity of phosphoric acid is low at low temperatures, so these fuel cells are used at temperatures up to 150-220 °C.

The charge carrier in fuel cells of this type is hydrogen (H+, proton). A similar process occurs in proton exchange membrane fuel cells (PEMFCs), in which hydrogen supplied to the anode is split into protons and electrons. Protons travel through the electrolyte and combine with oxygen from the air at the cathode to form water. The electrons are sent through an external electrical circuit, thereby generating an electric current. Below are reactions that generate electric current and heat.

Reaction at the anode: 2H2 => 4H+ + 4e

Reaction at the cathode: O2(g) + 4H+ + 4e- => 2H2O

General reaction of the element: 2H2 + O2 => 2H2O

The efficiency of fuel cells based on phosphoric (orthophosphoric) acid is more than 40% when generating electrical energy. With combined production of heat and electricity, the overall efficiency is about 85%. In addition, given operating temperatures, waste heat can be used to heat water and generate atmospheric pressure steam.

The high performance of thermal power plants using fuel cells based on phosphoric (orthophosphoric) acid in the combined production of thermal and electrical energy is one of the advantages of this type of fuel cells. The units use carbon monoxide with a concentration of about 1.5%, which significantly expands the choice of fuel. Simple design, low degree of electrolyte volatility and increased stability are also advantages of such fuel cells.

Thermal power plants with electrical output power of up to 400 kW are commercially produced. Installations with a capacity of 11 MW have passed appropriate tests. Installations with output power up to 100 MW are being developed.

4. Proton exchange membrane fuel cells (PEMFC)

Proton exchange membrane fuel cells are considered the best type of fuel cells for generating power for vehicles, which can replace gasoline and diesel internal combustion engines. These fuel cells were first used by NASA for the Gemini program. Installations based on MOPFC with power from 1 W to 2 kW have been developed and demonstrated.

The electrolyte in these fuel cells is a solid polymer membrane (a thin film of plastic). When saturated with water, this polymer allows protons to pass through but does not conduct electrons.

The fuel is hydrogen, and the charge carrier is a hydrogen ion (proton). At the anode, the hydrogen molecule is split into a hydrogen ion (proton) and electrons. Hydrogen ions pass through the electrolyte to the cathode, and electrons move around the outer circle and produce electrical energy. Oxygen, which is taken from the air, is supplied to the cathode and combines with electrons and hydrogen ions to form water. The following reactions occur at the electrodes: Reaction at the anode: 2H2 + 4OH- => 4H2O + 4eReaction at the cathode: O2 + 2H2O + 4e- => 4OH Overall cell reaction: 2H2 + O2 => 2H2O Compared to other types of fuel cells, fuel cells with a proton exchange membrane produce more energy for a given volume or weight of the fuel cell. This feature allows them to be compact and lightweight. In addition, the operating temperature is less than 100°C, which allows you to quickly start operation. These characteristics, as well as the ability to quickly change energy output, are just a few that make these fuel cells a prime candidate for use in vehicles.

Another advantage is that the electrolyte is a solid rather than a liquid. It is easier to retain gases at the cathode and anode using a solid electrolyte, so such fuel cells are cheaper to produce. With a solid electrolyte, there are no orientation issues and fewer corrosion problems, increasing the longevity of the cell and its components.

5. Solid oxide fuel cells (SOFC)

Solid oxide fuel cells are the highest operating temperature fuel cells. The operating temperature can vary from 600°C to 1000°C, allowing the use of different types of fuel without special pre-treatment. To handle such high temperatures, the electrolyte used is a thin solid metal oxide on a ceramic base, often an alloy of yttrium and zirconium, which is a conductor of oxygen ions (O2-). The technology of using solid oxide fuel cells has been developing since the late 50s of the twentieth century and has two configurations: planar and tubular.

The solid electrolyte provides a sealed transition of gas from one electrode to another, while liquid electrolytes are located in a porous substrate. The charge carrier in fuel cells of this type is the oxygen ion (O2-). At the cathode, oxygen molecules from the air are separated into an oxygen ion and four electrons. Oxygen ions pass through the electrolyte and combine with hydrogen, creating four free electrons. The electrons are sent through an external electrical circuit, generating electric current and waste heat.

Reaction at the anode: 2H2 + 2O2- => 2H2O + 4e

Reaction at the cathode: O2 + 4e- => 2O2-

General reaction of the element: 2H2 + O2 => 2H2O

The efficiency of electrical energy production is the highest of all fuel cells - about 60%. In addition, high operating temperatures allow for the combined production of thermal and electrical energy to generate high-pressure steam. Combining a high-temperature fuel cell with a turbine makes it possible to create a hybrid fuel cell to increase the efficiency of generating electrical energy by up to 70%.

Solid oxide fuel cells operate at very high temperatures (600°C-1000°C), resulting in significant time required to reach optimal operating conditions and a slower system response to changes in energy consumption. At such high operating temperatures, no converter is required to recover hydrogen from the fuel, allowing the thermal power plant to operate with relatively impure fuels resulting from gasification of coal or waste gases, etc. The fuel cell is also excellent for high power applications, including industrial and large central power plants. Modules with an electrical output power of 100 kW are commercially produced.

6. Direct methanol oxidation fuel cells (DOMFC)

Direct methanol oxidation fuel cells They are successfully used in the field of powering mobile phones, laptops, as well as to create portable power sources, which is what the future use of such elements is aimed at.

The design of fuel cells with direct oxidation of methanol is similar to the design of fuel cells with a proton exchange membrane (MEPFC), i.e. A polymer is used as an electrolyte, and a hydrogen ion (proton) is used as a charge carrier. But liquid methanol (CH3OH) oxidizes in the presence of water at the anode, releasing CO2, hydrogen ions and electrons, which are sent through an external electrical circuit, thereby generating an electric current. Hydrogen ions pass through the electrolyte and react with oxygen from the air and electrons from the external circuit to form water at the anode.

Reaction at the anode: CH3OH + H2O => CO2 + 6H+ + 6eReaction at the cathode: 3/2O2 + 6H+ + 6e- => 3H2O General reaction of the element: CH3OH + 3/2O2 => CO2 + 2H2O The development of such fuel cells has been carried out since the beginning of the 90s s of the twentieth century and their specific power and efficiency were increased to 40%.

These elements were tested in the temperature range of 50-120°C. Because of their low operating temperatures and the absence of the need for a converter, such fuel cells are a prime candidate for use in mobile phones and other consumer products, as well as in car engines. Their advantage is also their small size.

7. Polymer electrolyte fuel cells (PEFC)

In the case of polymer electrolyte fuel cells, the polymer membrane consists of polymer fibers with water regions in which conduction water ions H2O+ (proton, red) attaches to a water molecule. Water molecules pose a problem due to slow ion exchange. Therefore, a high concentration of water is required both in the fuel and at the outlet electrodes, which limits the operating temperature to 100°C.

8. Solid acid fuel cells (SFC)

In solid acid fuel cells, the electrolyte (CsHSO4) does not contain water. The operating temperature is therefore 100-300°C. The rotation of the SO42 oxyanions allows the protons (red) to move as shown in the figure. Typically, a solid acid fuel cell is a sandwich in which a very thin layer of solid acid compound is sandwiched between two electrodes that are tightly pressed together to ensure good contact. When heated, the organic component evaporates, exiting through the pores in the electrodes, maintaining the ability of multiple contacts between the fuel (or oxygen at the other end of the element), the electrolyte and the electrodes.

9. Comparison of the most important characteristics of fuel cells

Characteristics of fuel cells

Fuel cell type	Operating temperature	Power generation efficiency	Fuel type	Scope of application
				Medium and large installations
			Pure hydrogen	installations
			Pure hydrogen	Small installations
			Most hydrocarbon fuels	Small, medium and large installations
				Portable installations
			Pure hydrogen	Space researched
			Pure hydrogen	Small installations

10. Use of fuel cells in cars