home Business blogs Fuel cells for generating electricity. Using fuel cells to power buildings

Fuel cells for generating electricity. Using fuel cells to power buildings

A fuel cell is a device that efficiently produces heat and direct current through an electrochemical reaction and uses a hydrogen-rich fuel. Its operating principle is similar to that of a battery. Structurally, the fuel cell is represented by an electrolyte. What's so special about it? Unlike batteries, hydrogen fuel cells do not store electrical energy, do not require electricity to recharge, and do not discharge. The cells continue to produce electricity as long as they have a supply of air and fuel.

Peculiarities

The difference between fuel cells and other electricity generators is that they do not burn fuel during operation. Due to this feature, they do not require rotors high pressure, do not emit loud noise or vibrations. Electricity in fuel cells is generated through a silent electrochemical reaction. The chemical energy of the fuel in such devices is converted directly into water, heat and electricity.

Fuel cells are highly efficient and do not produce large amounts of greenhouse gases. The emission product during cell operation is a small amount of water in the form of steam and carbon dioxide, which is not released if pure hydrogen is used as fuel.

History of appearance

In the 1950s and 1960s, NASA's emerging need for energy sources for long-term space missions provoked one of the most critical challenges for fuel cells that existed at that time. Alkaline cells use oxygen and hydrogen as fuel, which are converted through an electrochemical reaction into byproducts useful during space flight - electricity, water and heat.

Fuel cells were first discovered at the beginning of the 19th century - in 1838. At the same time, the first information about their effectiveness appeared.

Work on fuel cells using alkaline electrolytes began in the late 1930s. Cells with nickel-plated electrodes under high pressure were not invented until 1939. During World War II, fuel cells consisting of alkaline cells with a diameter of about 25 centimeters were developed for British submarines.

Interest in them increased in the 1950s-80s, characterized by a shortage petroleum fuel. Countries around the world have begun to address air and environmental pollution issues in an effort to develop environmentally friendly fuel cell production technology is currently undergoing active development.

Principle of operation

Heat and electricity are generated by fuel cells as a result of an electrochemical reaction involving a cathode, anode and an electrolyte.

The cathode and anode are separated by a proton-conducting electrolyte. After oxygen enters the cathode and hydrogen enters the anode, a chemical reaction is started, resulting in heat, current and water.

Dissociates on the anode catalyst, which leads to the loss of electrons. Hydrogen ions enter the cathode through the electrolyte, and at the same time electrons pass through the outer electrical network and create direct current, which is used to power equipment. An oxygen molecule on the cathode catalyst combines with an electron and an incoming proton, ultimately forming water, which is the only product of the reaction.

Types

Choice specific type fuel cell depends on its application. All fuel cells are divided into two main categories - high temperature and low temperature. The latter use pure hydrogen as fuel. Such devices typically require processing of primary fuel into pure hydrogen. The process is carried out using special equipment.

High temperature fuel cells do not need this because they convert the fuel at elevated temperatures, which eliminates the need to create a hydrogen infrastructure.

The operating principle of hydrogen fuel cells is based on the conversion of chemical energy into electrical energy without ineffective combustion processes and the transformation of thermal energy into mechanical energy.

General concepts

Hydrogen fuel cells are electrochemical devices that produce electricity through highly efficient "cold" combustion of fuel. There are several types of such devices. Most promising technology Hydrogen-air fuel cells equipped with a proton exchange membrane PEMFC are considered.

The proton-conducting polymer membrane is designed to separate two electrodes - the cathode and the anode. Each of them is represented by a carbon matrix with a catalyst deposited on it. dissociates on the anode catalyst, donating electrons. Cations are conducted to the cathode through the membrane, but electrons are transferred to the external circuit because the membrane is not designed to transfer electrons.

An oxygen molecule on the cathode catalyst combines with an electron from the electrical circuit and an incoming proton, ultimately forming water, which is the only product of the reaction.

Hydrogen fuel cells are used to manufacture membrane-electrode units, which act as the main generating elements energy system.

Advantages of Hydrogen Fuel Cells

Among them are:

Increased specific heat capacity.
Wide operating temperature range.
No vibration, noise or heat stain.
Cold start reliability.
No self-discharge, which ensures long-term energy storage.
Unlimited autonomy thanks to the ability to adjust energy intensity by changing the number of fuel cartridges.
Providing virtually any energy intensity by changing the hydrogen storage capacity.
Long service life.
Quiet and environmentally friendly operation.
High level of energy intensity.
Tolerance to foreign impurities in hydrogen.

Application area

Due to their high efficiency, hydrogen fuel cells are used in various fields:

Portable chargers.
Power supply systems for UAVs.
Uninterruptible power supplies.
Other devices and equipment.

Prospects for hydrogen energy

The widespread use of hydrogen peroxide fuel cells will only be possible after the creation of effective way obtaining hydrogen. New ideas are required to bring the technology into active use, with high hopes placed on the concept of biofuel cells and nanotechnology. Some companies have relatively recently released effective catalysts based on various metals, at the same time information has appeared about the creation of fuel cells without membranes, which has made it possible to significantly reduce the cost of production and simplify the design of such devices. The advantages and characteristics of hydrogen fuel cells do not outweigh their main disadvantage - high cost, especially in comparison with hydrocarbon devices. The creation of one hydrogen power plant requires a minimum of 500 thousand dollars.

How to assemble a hydrogen fuel cell?

You can create a low-power fuel cell yourself in a regular home or school laboratory. The materials used are an old gas mask, pieces of plexiglass, water solution ethyl alcohol and alkali.

The body of a hydrogen fuel cell is created with your own hands from plexiglass with a thickness of at least five millimeters. The partitions between the compartments can be thinner - about 3 millimeters. Plexiglas is glued together with a special glue made from chloroform or dichloroethane and plexiglass shavings. All work is carried out only with the hood running.

A hole with a diameter of 5-6 centimeters is drilled in the outer wall of the housing, into which a rubber stopper and a glass drain tube are inserted. Activated carbon from the gas mask is poured into the second and fourth compartments of the fuel cell housing - it will be used as an electrode.

Fuel will circulate in the first chamber, while the fifth is filled with air, from which oxygen will be supplied. The electrolyte, poured between the electrodes, is impregnated with a solution of paraffin and gasoline to prevent it from entering the air chamber. Copper plates with wires soldered to them are placed on the layer of coal, through which the current will be drained.

The assembled hydrogen fuel cell is charged with vodka diluted with water in a 1:1 ratio. Caustic potassium is carefully added to the resulting mixture: 70 grams of potassium dissolve in 200 grams of water.

Before testing a hydrogen fuel cell, fuel is poured into the first chamber and electrolyte into the third. The reading of a voltmeter connected to the electrodes should vary from 0.7 to 0.9 volts. To ensure continuous operation of the element, spent fuel must be removed, and new fuel must be poured through a rubber tube. By squeezing the tube, the fuel supply rate is adjusted. Such hydrogen fuel cells, assembled at home, have little power.

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 industrial world experienced a fuel oil shortage. 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

Like existence various types internal combustion engines, there are different types of fuel cells - the choice of the appropriate 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. High operating temperature allows direct use of natural gas without a fuel processor and fuel gas with low fuel calorific value production processes and from 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 high degree Due to the mobility of ions in the electrolyte, the operation of fuel cells with a molten carbonate electrolyte occurs 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, internal reforming occurs natural gas, 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 output electrical power 3.0 MW. 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 orthophosphoric 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. Working 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. She has successfully established herself in the field of nutrition mobile phones, laptops, as well as for creating portable sources of electricity. 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 among the most effective elements, used to generate electricity, the efficiency of electricity generation reaches 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 characteristic features SHTE – 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

Fuel cell battery
Other equipment operating at high temperature(integrated steam generator, combustion chamber, heat balance changer)
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 work for various types hydrocarbon fuels, mainly natural gas
have a longer start-up time and are therefore better suited for long-term action
demonstrate high efficiency electricity generation (up to 70%)
Due to the high operating temperatures, the units can be combined with heat transfer systems, bringing the overall system efficiency up 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 best suited for efficient electricity generation 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 labor-intensive maintenance, and emit 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 more high performance installations. After all, the fuel cell is an environmentally friendly technological solution with minimal impact on environment.

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 level noise
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 bus voltage all the time direct current and smoothly accepts critical loads if the DC bus voltage drops below a user-defined setpoint. 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 widely available, produced in industrial scale a fuel that currently has many uses, among others windshield washers, plastic bottles, engine additives, emulsion paints. 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. 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 communication over IP protocol...)
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:

Liquid fuel technology solves the problem of hydrogen placement and provides virtually unlimited backup power.
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.
Preparations for the use of the system on site are quick and economical, and operating costs are low.
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 get critical important 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 place, and have well-known problems with their reliability and technical maintenance. 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 traditional power transmission networks used in this moment. 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 Utilization of associated petroleum gas has 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.

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.
Flexibility in relation to electrical load consumers, surge, load surge.
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.
High automation and modern remote control do not require permanent presence of personnel at the installation.
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.
Water consumption: none at ambient temperatures up to +30 °C and negligible at higher temperatures.
Water outlet: none.
In addition, thermal power plants using fuel cells do not make noise, do not vibrate, do not produce harmful emissions into the atmosphere

They operate the spacecraft of the US National Aeronautics and Space Administration (NASA). They provide power to the computers of the First National Bank in Omaha. They are used on some public city buses in Chicago.

These are all fuel cells. Fuel cells are electrochemical devices that produce electricity without combustion - chemically, in much the same way as batteries. The only difference is that they use different chemicals, hydrogen and oxygen, and the product of the chemical reaction is water. Natural gas can also be used, but when using hydrocarbon fuels, of course, a certain level of carbon dioxide emissions is inevitable.

Because fuel cells can operate with high efficiency and no harmful emissions, they hold great promise as a sustainable energy source that will help reduce emissions of greenhouse gases and other pollutants. The main obstacle to the widespread use of fuel cells is their high price compared to other devices that generate electricity or drive vehicles.

History of development

The first fuel cells were demonstrated by Sir William Groves in 1839. Groves showed that the process of electrolysis - the splitting of water into hydrogen and oxygen under the influence of an electric current - is reversible. That is, hydrogen and oxygen can be combined chemically to form electricity.

After this was demonstrated, many scientists rushed to study fuel cells with zeal, but the invention of the internal combustion engine and the development of oil reserve infrastructure in the second half of the nineteenth century left the development of fuel cells far behind. The development of fuel cells was further hampered by their high cost.

A surge in the development of fuel cells occurred in the 50s, when NASA turned to them in connection with the need for a compact electric generator for space flights. The investment was made and the Apollo and Gemini flights were powered by fuel cells. Spacecraft also run on fuel cells.

Fuel cells are still largely an experimental technology, but several companies are already selling them on the commercial market. In the last nearly ten years alone, significant advances have been made in commercial fuel cell technology.

How does a fuel cell work?

Fuel cells are similar to batteries - they produce electricity through a chemical reaction. In contrast, internal combustion engines burn fuel and thus produce heat, which is then converted into mechanical energy. Unless the heat from the exhaust gases is used in some way (for example, for heating or air conditioning), then the efficiency of the internal combustion engine can be said to be quite low. For example, the efficiency of fuel cells when used in a vehicle, a project currently under development, is expected to be more than twice the efficiency of today's typical gasoline engines used in automobiles.

Although both batteries and fuel cells produce electricity chemically, they perform two very different functions. Batteries are stored energy devices: the electricity they produce is the result of a chemical reaction of a substance that is already inside them. Fuel cells do not store energy, but rather convert some of the energy from externally supplied fuel into electricity. In this respect, a fuel cell is more like a conventional power plant.

There are several different types of fuel cells. The simplest fuel cell consists of a special membrane known as an electrolyte. Powdered electrodes are applied on both sides of the membrane. This design - an electrolyte surrounded by two electrodes - is a separate element. Hydrogen goes to one side (anode), and oxygen (air) to the other (cathode). Different chemical reactions occur at each electrode.

At the anode, hydrogen breaks down into a mixture of protons and electrons. In some fuel cells, the electrodes are surrounded by a catalyst, usually made of platinum or other noble metals, which promotes the dissociation reaction:

2H2 ==> 4H+ + 4e-.

H2 = diatomic hydrogen molecule, form, in

in which hydrogen is present in the form of a gas;

H+ = ionized hydrogen, i.e. proton;

e- = electron.

The operation of a fuel cell is based on the fact that the electrolyte allows protons to pass through it (towards the cathode), but electrons do not. Electrons move to the cathode along an external conductive circuit. This movement of electrons is an electrical current that can be used to drive an external device connected to the fuel cell, such as an electric motor or light bulb. This device is usually called a "load".

At the cathode side of the fuel cell, protons (that have passed through the electrolyte) and electrons (that have passed through the external load) are “recombined” and react with the oxygen supplied to the cathode to form water, H2O:

4H+ + 4e- + O2 ==> 2H2O.

The total reaction in a fuel cell is written as follows:

2H2 + O2 ==> 2H2O.

In their work, fuel cells use hydrogen fuel and oxygen from the air. Hydrogen can be supplied directly or by separating it from an external fuel source such as natural gas, gasoline or methanol. In the case of an external source, it must be chemically converted to extract the hydrogen. This process is called "reforming". Hydrogen can also be produced from ammonia, alternative resources such as gas from city landfills and wastewater treatment plants, and through water electrolysis, which uses electricity to break water into hydrogen and oxygen. Currently, most fuel cell technologies used in transportation use methanol.

Various means have been developed to reform fuels to produce hydrogen for fuel cells. The US Department of Energy has developed a fuel unit inside a gasoline reformer to supply hydrogen to a self-contained fuel cell. Researchers from the Pacific Northwest National Laboratory in the US have demonstrated a compact fuel reformer one-tenth the size of a power supply. US utility Northwest Power Systems and Sandia National Laboratories have demonstrated a fuel reformer that converts diesel fuel into hydrogen for fuel cells.

Individually, the fuel cells produce about 0.7-1.0V each. To increase the voltage, the elements are assembled into a “cascade”, i.e. serial connection. To create more current, sets of cascaded elements are connected in parallel. If you combine fuel cell cascades with a fuel system, an air supply and cooling system, and a control system, you get a fuel cell engine. This engine can power a vehicle, a stationary power plant, or a portable electric generator6. Fuel cell engines come in different sizes depending on the application, the type of fuel cell and the fuel used. For example, each of the four separate 200 kW stationary power plants installed at a bank in Omaha is approximately the size of a truck trailer.

Applications

Fuel cells can be used in both stationary and mobile devices. In response to tightening emissions regulations in the United States, automakers including DaimlerChrysler, Toyota, Ford, General Motors, Volkswagen, Honda and Nissan began experimenting and demonstrating vehicles powered by fuel cells. The first commercial fuel cell vehicles are expected to hit the road in 2004 or 2005.

A major milestone in the development of fuel cell technology was the June 1993 demonstration of Ballard Power System's experimental 32-foot city bus powered by a 90-kilowatt hydrogen fuel cell engine. Since then, many have been developed and put into operation different types and different generations of fuel cell passenger vehicles running on different types of fuel. Since late 1996, three hydrogen fuel cell golf carts have been in use in Palm Desert, California. On the roads of Chicago, Illinois; Vancouver, British Columbia; and Oslo, Norway, city buses powered by fuel cells are being tested. Taxis powered by alkaline fuel cells are being tested on the streets of London.

Stationary installations using fuel cell technology are also being demonstrated, but they are not yet widely used commercially. First National Bank of Omaha in Nebraska uses a fuel cell system to power its computers because the system is more reliable than the old system, which ran off the main grid with backup battery power. The world's largest commercial fuel cell system, rated at 1.2 MW, will soon be installed at a mail processing center in Alaska. Fuel cell-powered portable laptop computers, control systems used in wastewater treatment plants and vending machines are also being tested and demonstrated.

"Pros and cons"

Fuel cells have a number of advantages. While modern internal combustion engines are only 12-15% efficient, fuel cells are 50% efficient. The efficiency of fuel cells can remain quite high level, even when they are not used at full rated power, which is a serious advantage compared to gasoline engines.

The modular design of fuel cells means that the power of a fuel cell power plant can be increased simply by adding more stages. This ensures that capacity underutilization is minimized, allowing for better matching of supply and demand. Since the efficiency of a fuel cell stack is determined by the performance of the individual cells, small fuel cell power plants operate as efficiently as large ones. Additionally, waste heat from stationary fuel cell systems can be used for water and space heating, further increasing energy efficiency.

There are virtually no harmful emissions when using fuel cells. When an engine runs on pure hydrogen, only heat and pure water vapor are produced as by-products. So on spaceships, astronauts drink water, which is formed as a result of the operation of onboard fuel cells. The composition of emissions depends on the nature of the hydrogen source. Methanol produces zero nitrogen oxide and carbon monoxide emissions and only small hydrocarbon emissions. Emissions increase as you move from hydrogen to methanol and gasoline, although even with gasoline, emissions will remain fairly low. In any case, replacing today's traditional internal combustion engines with fuel cells would lead to an overall reduction in CO2 and nitrogen oxide emissions.

The use of fuel cells provides flexibility to the energy infrastructure, creating additional features for decentralized power generation. The multiplicity of decentralized energy sources makes it possible to reduce losses during electricity transmission and develop energy markets (which is especially important for remote and rural areas with no access to power lines). With the help of fuel cells, individual residents or neighborhoods can become self-sufficient for the most part electricity and thus significantly increase the efficiency of its use.

Fuel cells offer energy High Quality and increased reliability. They are durable, have no moving parts, and produce a constant amount of energy.

However, fuel cell technology needs to be further improved to improve performance, reduce costs, and thus make fuel cells competitive with other energy technologies. It should be noted that when the cost characteristics of energy technologies are considered, comparisons must be made on the basis of all components technological characteristics, including capital operating costs, pollutant emissions, energy quality, durability, decommissioning and flexibility.

Although hydrogen gas is the best fuel, the infrastructure or transport base for it does not yet exist. In the near future, hydrogen sources in the form of gasoline, methanol or natural gas could be used to provide power plants with existing systems fossil fuel supplies (gas stations, etc.). This would eliminate the need for dedicated hydrogen filling stations, but would require each vehicle to have a fossil fuel-to-hydrogen converter ("reformer") installed. The disadvantage of this approach is that it uses fossil fuels and thus results in carbon dioxide emissions. Methanol, the current leading candidate, produces fewer emissions than gasoline, but would require a larger container in the vehicle because it takes up twice the space for the same energy content.

Unlike fossil fuel supply systems, solar and wind systems (using electricity to create hydrogen and oxygen from water) and direct photoconversion systems (using semiconductor materials or enzymes to produce hydrogen) could provide hydrogen supply without a reforming step, and thus Thus, emissions of harmful substances that are observed when using methanol or gasoline fuel cells could be avoided. The hydrogen could be stored and converted into electricity in the fuel cell as needed. Looking ahead, pairing fuel cells with these kinds of renewable energy sources is likely to be an effective strategy for providing a productive, environmentally smart, and versatile source of energy.

IEER's recommendations are that local, federal, and state governments devote a portion of their transportation procurement budgets to fuel cell vehicles, as well as stationary fuel cell systems, to provide heat and power for some of their significant or new buildings. This will contribute to the development of vital important technology and reducing greenhouse gas emissions.

From the point of view of “green” energy, hydrogen fuel cells have an extremely high efficiency of 60%. For comparison: the efficiency of the best internal combustion engines is 35-40%. For solar power plants, the coefficient is only 15-20%, but is highly dependent on weather conditions. The efficiency of the best impeller wind farms reaches 40%, which is comparable to steam generators, but wind turbines also require suitable weather conditions and expensive maintenance.

As we can see, in terms of this parameter, hydrogen energy is the most attractive source of energy, but there are still a number of problems that prevent its mass use. The most important of them is the process of hydrogen production.

Mining problems

Hydrogen energy is environmentally friendly, but not autonomous. To operate, a fuel cell requires hydrogen, which is not found on Earth in its pure form. Hydrogen needs to be produced, but all currently existing methods are either very expensive or ineffective.

The most effective method in terms of the volume of hydrogen produced per unit of energy expended is considered to be the method of steam reforming of natural gas. Methane is combined with water vapor at a pressure of 2 MPa (about 19 atmospheres, i.e. pressure at a depth of about 190 m) and a temperature of about 800 degrees, resulting in a converted gas with a hydrogen content of 55-75%. Steam reforming requires huge installations that can only be used in production.

A tube furnace for steam methane reforming is not the most ergonomic way to produce hydrogen. Source: CTK-Euro

A more convenient and simpler method is water electrolysis. When an electric current passes through the water being treated, a series of electrochemical reactions occur, resulting in the formation of hydrogen. A significant disadvantage of this method is the high energy consumption required to carry out the reaction. That is, a somewhat strange situation arises: to obtain hydrogen energy you need... energy. To avoid unnecessary costs during electrolysis and conserve valuable resources, some companies are striving to develop full cycle “electricity - hydrogen - electricity” systems, in which energy production becomes possible without external recharge. An example of such a system is the development of Toshiba H2One.

Mobile power station Toshiba H2One

We have developed the H2One mobile mini power station that converts water into hydrogen and hydrogen into energy. To maintain electrolysis, it uses solar panels, and excess energy is stored in batteries and ensures the system operates in the absence of sunlight. The resulting hydrogen is either directly supplied to the fuel cells or sent for storage in an integrated tank. In an hour, the H2One electrolyzer generates up to 2 m 3 of hydrogen, and provides output power of up to 55 kW. To produce 1 m 3 of hydrogen, the station requires up to 2.5 m 3 of water.

While the H2One station is not able to provide electricity large enterprise or an entire city, but for the functioning of small areas or organizations its energy will be quite sufficient. Thanks to its portability, it can also be used as a temporary solution during natural disasters or emergency power outages. In addition, unlike a diesel generator, which requires fuel to function properly, a hydrogen power plant only requires water.

Currently, the Toshiba H2One is used in only a few cities in Japan - for example, it supplies electricity and hot water train station in Kawasaki city.

Installation of the H2One system in Kawasaki

Hydrogen future

Now hydrogen fuel cells provide energy for portable power banks, city buses with cars, and railway transport (We will talk more about the use of hydrogen in the auto industry in our next post). Hydrogen fuel cells unexpectedly turned out to be an excellent solution for quadcopters - with a similar mass to the battery, the hydrogen supply provides up to five times longer flight time. However, frost does not affect efficiency in any way. Experimental fuel cell drones produced by the Russian company AT Energy were used for filming at the Sochi Olympics.

It has become known that at the upcoming Olympic Games in Tokyo, hydrogen will be used in cars, in the production of electricity and heat, and will also become the main source of energy for the Olympic village. For this purpose, by order of Toshiba Energy Systems & Solutions Corp. One of the world's largest hydrogen production stations is being built in the Japanese city of Namie. The station will consume up to 10 MW of energy obtained from “green” sources, generating up to 900 tons of hydrogen per year through electrolysis.

Hydrogen energy is our “reserve for the future,” when fossil fuels will have to be completely abandoned, and renewable energy sources will not be able to meet the needs of humanity. According to the Markets&Markets forecast, the volume of global hydrogen production, which currently stands at $115 billion, will grow to $154 billion by 2022. But mass implementation of the technology is unlikely to happen in the near future; a number of problems associated with the production and operation of special power plants still need to be resolved and their cost reduced . When technological barriers are overcome, hydrogen energy will reach a new level and may be as widespread as traditional or hydropower today.

Fuel cell- what it is? When and how did he appear? Why is it needed and why do they talk about them so often nowadays? What are its applications, characteristics and properties? Unstoppable progress requires answers to all these questions!

What is a fuel cell?

Fuel cell- is a chemical current source or electrochemical generator; it is a device for converting chemical energy into electrical energy. In modern life, chemical power sources are used everywhere and are batteries for mobile phones, laptops, PDAs, as well as batteries in cars, uninterruptible power supplies, etc. The next stage in the development of this area will be the widespread distribution of fuel cells and this is an irrefutable fact.

History of fuel cells

The history of fuel cells is another story about how the properties of matter, once discovered on Earth, found wide application far in space, and at the turn of the millennium returned from heaven to Earth.

It all started in 1839, when the German chemist Christian Schönbein published the principles of the fuel cell in the Philosophical Journal. In the same year, an Englishman and Oxford graduate, William Robert Grove, designed a galvanic cell, later called the Grove galvanic cell, which is also recognized as the first fuel cell. The name “fuel cell” was given to the invention in the year of its anniversary - in 1889. Ludwig Mond and Karl Langer are the authors of the term.

A little earlier, in 1874, Jules Verne, in his novel The Mysterious Island, predicted the current energy situation, writing that “Water will one day be used as fuel, the hydrogen and oxygen of which it is composed will be used.”

Meanwhile, new technology power supply was gradually improved, and starting from the 50s of the 20th century, not even a year passed without announcements of the latest inventions in this area. In 1958, the first tractor powered by fuel cells appeared in the United States, in 1959. a 5kW power supply for a welding machine was released, etc. In the 70s, hydrogen technology took off into space: airplanes and rocket engines on hydrogen. In the 60s, RSC Energia developed fuel cells for the Soviet lunar program. The Buran program also could not do without them: alkaline 10 kW fuel cells were developed. And towards the end of the century, fuel cells crossed zero altitude above sea level - based on them, power supply German submarine. Returning to Earth, the first locomotive was put into operation in the United States in 2009. Naturally, on fuel cells.

In all wonderful story What is interesting about fuel cells is that the wheel still remains an invention of mankind that has no analogues in nature. The fact is that in their design and principle of operation, fuel cells are similar to a biological cell, which, in essence, is a miniature hydrogen-oxygen fuel cell. As a result, man once again invented something that nature has been using for millions of years.

Operating principle of fuel cells

The principle of operation of fuel cells is obvious even from school curriculum in chemistry and it was precisely this that was laid down in the experiments of William Grove in 1839. The thing is that the process of water electrolysis (water dissociation) is reversible. Just as it is true that when an electric current is passed through water, the latter is split into hydrogen and oxygen, so the reverse is also true: hydrogen and oxygen can be combined to produce water and electricity. In Grove's experiment, two electrodes were placed in a chamber into which limited portions of pure hydrogen and oxygen were supplied under pressure. Due to the small volumes of gas, as well as due to the chemical properties of the carbon electrodes, a slow reaction occurred in the chamber with the release of heat, water and, most importantly, the formation of a potential difference between the electrodes.

The simplest fuel cell consists of a special membrane used as an electrolyte, on both sides of which powdered electrodes are applied. Hydrogen goes to one side (anode), and oxygen (air) goes to the other (cathode). Different chemical reactions occur at each electrode. At the anode, hydrogen breaks down into a mixture of protons and electrons. In some fuel cells, the electrodes are surrounded by a catalyst, usually made of platinum or other noble metals, that promotes the dissociation reaction:

2H 2 → 4H + + 4e -

where H 2 is a diatomic hydrogen molecule (the form in which hydrogen is present as a gas); H + - ionized hydrogen (proton); e - - electron.

At the cathode side of the fuel cell, protons (that have passed through the electrolyte) and electrons (that have passed through the external load) recombine and react with the oxygen supplied to the cathode to form water:

4H + + 4e - + O 2 → 2H 2 O

Total reaction in a fuel cell it is written like this:

2H 2 + O 2 → 2H 2 O

Fuel cells use hydrogen fuel and oxygen to operate. The easiest way is with oxygen - it is taken from the air. Hydrogen can be supplied directly from a certain container or by isolating it from an external fuel source (natural gas, gasoline or methyl alcohol - methanol). In the case of an external source, it must be chemically converted to extract the hydrogen. Currently, most fuel cell technologies being developed for portable devices use methanol.

Characteristics of fuel cells

Fuel cells are analogous to existing batteries in the sense that in both cases electrical energy is obtained from chemical energy. But there are also fundamental differences:

they only work as long as the fuel and oxidizer are supplied from an external source (i.e. they cannot store electrical energy),
the chemical composition of the electrolyte does not change during operation (the fuel cell does not need to be recharged),
they are completely independent of electricity (while conventional batteries store energy from the mains).

Each fuel cell creates voltage 1V. Higher voltage is achieved by connecting them in series. An increase in power (current) is realized through a parallel connection of cascades of series-connected fuel cells.

In fuel cells there is no strict limitation on efficiency, like that of heat engines (the efficiency of the Carnot cycle is the highest possible efficiency among all heat engines with the same minimum and maximum temperatures).

High efficiency achieved through the direct conversion of fuel energy into electricity. When diesel generator sets burn fuel first, the resulting steam or gas rotates a turbine or internal combustion engine shaft, which in turn rotates an electric generator. The result is an efficiency of a maximum of 42%, but more often it is about 35-38%. Moreover, due to the many links, as well as due to thermodynamic limitations on the maximum efficiency of heat engines, the existing efficiency is unlikely to be raised higher. For existing fuel cells Efficiency is 60-80%,

Efficiency almost does not depend on load factor,

Capacity is several times higher than in existing batteries,

Complete no environmentally harmful emissions. Only pure water vapor and thermal energy are released (unlike diesel generators, which have polluting exhausts and require their removal).

Types of fuel cells

Fuel cells classified according to the following characteristics:

according to the fuel used,

by operating pressure and temperature,

according to the nature of the application.

In general, the following are distinguished: types of fuel cells:

Solid-oxide fuel cells (SOFC);

Fuel cell with a proton-exchange membrane fuel cell (PEMFC);

Reversible Fuel Cell (RFC);

Direct-methanol fuel cell (DMFC);

Molten-carbonate fuel cells (MCFC);

Phosphoric-acid fuel cells (PAFC);

Alkaline fuel cells (AFC).

One type of fuel cell that operates at normal temperatures and pressures using hydrogen and oxygen is the ion exchange membrane cell. The resulting water does not dissolve the solid electrolyte, flows down and is easily removed.

Fuel cell problems

The main problem of fuel cells is related to the need to have “packaged” hydrogen, which could be freely purchased. Obviously, the problem should be solved over time, but for now the situation raises a slight smile: what comes first - the chicken or the egg? Fuel cells are not yet developed enough to build hydrogen factories, but their progress is unthinkable without these factories. Here we note the problem of the hydrogen source. Currently, hydrogen is produced from natural gas, but rising energy costs will also increase the price of hydrogen. At the same time, in hydrogen from natural gas, the presence of CO and H 2 S (hydrogen sulfide) is inevitable, which poison the catalyst.

Common platinum catalysts use a very expensive and irreplaceable metal - platinum. However, this problem is planned to be solved by using catalysts based on enzymes, which are a cheap and easily produced substance.

The heat generated is also a problem. Efficiency will increase sharply if the generated heat is directed into a useful channel - to produce thermal energy for heat supply systems, used as waste heat in absorption refrigeration machines and so on.

Methanol Fuel Cells (DMFC): Real Applications

The greatest practical interest today is direct fuel cells based on methanol (Direct Methanol Fuel Cell, DMFC). The Portege M100 laptop running on a DMFC fuel cell looks like this:

A typical DMFC cell circuit contains, in addition to the anode, cathode and membrane, several additional components: a fuel cartridge, a methanol sensor, a fuel circulation pump, an air pump, a heat exchanger, etc.

The operating time of, for example, a laptop compared to batteries is planned to be increased 4 times (up to 20 hours), a mobile phone - up to 100 hours in active mode and up to six months in standby mode. Recharging will be carried out by adding a portion of liquid methanol.

The main task is to find options for using a methanol solution with its highest concentration. The problem is that methanol is a fairly strong poison, lethal in doses of several tens of grams. But the concentration of methanol directly affects the duration of operation. If previously a 3-10% methanol solution was used, then mobile phones and PDAs using a 50% solution have already appeared, and in 2008, in laboratory conditions, specialists from MTI MicroFuel Cells and, a little later, Toshiba obtained fuel cells operating on pure methanol.

Fuel cells are the future!

Finally, the obvious future of fuel cells is evidenced by the fact that the international organization IEC (International Electrotechnical Commission), which determines industrial standards for electronic devices, has already announced the creation of a working group to develop an international standard for miniature fuel cells.