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 power supply technology was gradually improved, and since the 50s of the 20th century, not a year has passed without the announcement 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 powered by hydrogen appeared. 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 - they were used to power the German submarine. Returning to Earth, the first locomotive was put into operation in the United States in 2009. Naturally, on fuel cells.
In all the wonderful history of fuel cells, the interesting thing 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 the school chemistry curriculum, 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
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 (a load, such as a light bulb):
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 at 1IN. 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 useful channels - to produce thermal energy for the heating system, to use it as waste heat in absorption refrigeration machines, etc.
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.
A universal source of energy for all biochemical processes in living organisms, while simultaneously creating an electrical potential difference on its inner membrane. However, copying this process to generate electricity on an industrial scale is difficult, since the proton pumps of mitochondria are of a protein nature.
TE device
Fuel cells are electrochemical devices that can theoretically have a high conversion rate of chemical energy into electrical energy.
The principle of separation of fuel and oxidizer flows
Typically, low temperature fuel cells use: hydrogen on the anode side and oxygen on the cathode side (hydrogen cell) or methanol and atmospheric oxygen. Unlike fuel cells, disposable voltaic cells and batteries contain consumable solid or liquid reagents, the mass of which is limited by the volume of the batteries, and when the electrochemical reaction stops, they must be replaced with new ones or electrically recharged to start the reverse chemical reaction, or at least At least they need to replace spent electrodes and contaminated electrolyte. In a fuel cell, reagents flow in, reaction products flow out, and the reaction can proceed as long as the reagents enter it and the reactivity of the components of the fuel cell itself is maintained, most often determined by their “poisoning” by by-products of insufficiently pure starting substances.
Example of a hydrogen-oxygen fuel cell
A proton exchange membrane (e.g., "polymer electrolyte") hydrogen-oxygen fuel cell contains a proton-conducting polymer membrane that separates two electrodes, the anode and the cathode. Each electrode is usually a carbon plate (matrix) coated with a catalyst - platinum or an alloy of platinum group metals and other compositions.
Fuel cells cannot store electrical energy like galvanic or rechargeable batteries, but for some applications, such as power plants operating isolated from the electrical system using intermittent energy sources (solar, wind), they are combined with electrolysers, compressors and fuel storage tanks ( e.g. hydrogen cylinders) form an energy storage device.
Membrane
The membrane allows the conduction of protons, but not electrons. It can be polymeric (Nafion, polybenzimidazole, etc.) or ceramic (oxide, etc.). However, there are fuel cells without a membrane.
Anodic and cathodic materials and catalysts
The anode and cathode are usually simply a conductive catalyst - platinum deposited on a highly developed carbon surface.
Types of fuel cells
| Fuel cell type | Reaction at the anode | Electrolyte | Reaction at the cathode | Temperature, °C |
|---|---|---|---|---|
| Alkaline TE | 2H 2 + 4OH − → 2H 2 O + 4e − | KOH solution | O 2 + 2H 2 O + 4e − → 4OH − | 200 |
| FC with proton exchange membrane | 2H 2 → 4H + + 4e − | Proton exchange membrane | 80 | |
| Methanol TE | 2CH 3 OH + 2H 2 O → 2CO 2 + 12H + + 12e − | Proton exchange membrane | 3O 2 + 12H + + 12e − → 6H 2 O | 60 |
| FC based on orthophosphoric acid | 2H 2 → 4H + + 4e − | Phosphoric acid solution | O 2 + 4H + + 4e − → 2H 2 O | 200 |
| Fuel cells based on molten carbonate | 2H 2 + 2CO 3 2− → 2H 2 O + 2CO 2 + 4e − | Molten carbonate | O 2 + 2CO 2 + 4e − → 2CO 3 2− | 650 |
| Solid oxide TE | 2H 2 + 2O 2 − → 2H 2 O + 4e − | Mixture of oxides | O 2 + 4e − → 2O 2 − | 1000 |
Air-aluminum electrochemical generator
The aluminum-air electrochemical generator uses the oxidation of aluminum with atmospheric oxygen to produce electricity. The current-generating reaction in it can be represented as
4 Al + 3 O 2 + 6 H 2 O ⟶ 4 Al (OH) 3 , (\displaystyle (\ce (4 Al + 3 O_2 + 6 H_2O -> 4 Al(OH)_3,))) E = 2.71 V , (\displaystyle \quad E=2.71~(\text(V)),)and the corrosion reaction is how
2 Al + 6 H 2 O ⟶ 2 Al (OH) 3 + 3 H 2 ⋅ (\displaystyle (\ce (2 Al + 6 H_2O -> 2 Al(OH)_3 + 3 H_2.)))Serious advantages of the air-aluminum electrochemical generator are: high (up to 50%) efficiency, absence of harmful emissions, ease of maintenance.
Advantages and disadvantages
Advantages of hydrogen fuel cells
Compact dimensionsFuel cells are lighter and smaller than traditional power sources. Fuel cells produce less noise, run less heat, and are more efficient in terms of fuel consumption. This becomes especially relevant in military applications. For example, a US Army soldier carries 22 different types of batteries. [ ] Average battery power is 20 watts. The use of fuel cells will reduce logistics costs, reduce weight, and extend the operating life of devices and equipment.
Fuel cell problems
The introduction of fuel cells in transport is hampered by the lack of hydrogen infrastructure. There is a “chicken and egg” problem - why produce hydrogen cars if there is no infrastructure? Why build hydrogen infrastructure if there is no hydrogen transport?
Most elements emit some amount of heat during operation. This requires the creation of complex technical devices for heat recovery (steam turbines, etc.), as well as the organization of fuel and oxidizer flows, power take-off control systems, membrane durability, poisoning of catalysts by certain by-products of fuel oxidation, and other tasks. But at the same time, the high temperature of the process allows the production of thermal energy, which significantly increases the efficiency of the power plant.
The problem of catalyst poisoning and membrane durability is solved by creating an element with self-healing mechanisms - regeneration of enzyme catalysts [ ] .
Fuel cells, due to the low rate of chemical reactions, have significant [ ] inertia and for operation under conditions of peak or pulsed loads require a certain power reserve or the use of other technical solutions (supercapacitors, batteries).
There is also the problem of obtaining and storing hydrogen. Firstly, it must be clean enough so that rapid poisoning of the catalyst does not occur, and secondly, it must be cheap enough so that its cost is profitable for the end user.
Of the simple chemical elements, hydrogen and carbon are extremes. Hydrogen has the highest specific heat of combustion, but very low density and high chemical reactivity. Carbon has the highest specific heat of combustion among solid elements, a fairly high density, but low chemical activity due to activation energy. The golden mean is a carbohydrate (sugar) or its derivatives (ethanol) or hydrocarbons (liquid and solid). The released carbon dioxide must participate in the general respiration cycle of the planet, without exceeding the maximum permissible concentrations.
There are many ways to produce hydrogen, but currently about 50% of the hydrogen produced worldwide comes from natural gas. All other methods are still very expensive. It is obvious that with a constant balance of primary energy carriers, with the growing demand for hydrogen as a mass fuel and the development of consumer resistance to pollution, production growth will increase precisely due to this share, and with the development of infrastructure that allows it to be available, more expensive (but more convenient in some situations) methods will die out. Other ways in which hydrogen is involved as a secondary energy carrier inevitably level its role from fuel to a kind of chemical battery. There is an opinion that as energy prices rise, the cost of hydrogen also inevitably rises because of this. But the cost of energy produced from renewable sources is constantly decreasing (see Wind energy, Hydrogen production). For example, the average price of electricity in the USA increased to $0.09 per kWh, while the cost of electricity produced from wind is $0.04-$0.07 (see Wind Energy or AWEA). In Japan, a kilowatt-hour of electricity costs about $0.2, which is comparable to the cost of electricity produced by photovoltaic cells. Considering the territorial remoteness of some promising areas (for example, transporting electricity generated by photovoltaic stations from Africa directly, by wire, is clearly futile, despite its enormous energy potential in this regard), even the operation of hydrogen as a “chemical battery” can be quite profitable. As of 2010, the cost of hydrogen fuel cell energy must fall eightfold in order to become competitive with the energy produced by thermal and nuclear power plants.
Unfortunately, hydrogen produced from natural gas will contain CO and hydrogen sulfide, which poison the catalyst. Therefore, to reduce catalyst poisoning, it is necessary to increase the temperature of the fuel cell. Already at a temperature of 160 °C, 1% CO may be present in the fuel.
The disadvantages of fuel cells with platinum catalysts include the high cost of platinum, difficulties in purifying hydrogen from the above-mentioned impurities, and, as a consequence, the high cost of gas, and the limited resource of the element due to poisoning of the catalyst by impurities. In addition, platinum for the catalyst is a non-renewable resource. It is believed that its reserves will be enough for 15-20 years of production of elements.
Enzymes are being explored as an alternative to platinum catalysts. Enzymes are a renewable material, they are cheap, and they are not poisoned by the main impurities in cheap fuel. They have specific advantages. The insensitivity of enzymes to CO and hydrogen sulfide has made it possible to obtain hydrogen from biological sources, for example, during the conversion of organic waste.
Story
First discoveries
The principle of operation of fuel cells was discovered in 1839 by the English scientist W. Grove, who discovered that the electrolysis process is reversible, that is, hydrogen and oxygen can be combined into water molecules without combustion, but with the release of heat and electricity. The scientist called his device, where he was able to carry out this reaction, a “gas battery,” and it was the first fuel cell. However, in the next 100 years this idea did not find practical application.
In 1937, Professor F. Bacon began work on his fuel cell. By the late 1950s, he had developed a battery of 40 fuel cells with a power of 5 kW. Such a battery could be used to provide energy for a welding machine or forklift. The battery operated at high temperatures of the order of 200°C or more and pressures of 20-40 bar. Besides, she was quite massive.
History of research in the USSR and Russia
The first studies began in the 1930s. RSC Energia (since 1966) developed PAFC elements for the Soviet lunar program. From 1987 to 1987, Energia produced about 100 fuel cells, which totaled about 80,000 hours of operation.
During work on the Buran program, alkaline AFC elements were studied. 10 kW fuel cells were installed on Buran.
In 1989, the Institute of High-Temperature Electrochemistry (Ekaterinburg) produced the first SOFC installation with a power of 1 kW.
In 1999, AvtoVAZ began work with fuel cells. By 2003, several prototypes were created based on the VAZ-2131 car. Fuel cell batteries were located in the engine compartment of the car, and tanks with compressed hydrogen were located in the luggage compartment, that is, the classic arrangement of the power unit and fuel tank tanks was used. The development of the hydrogen car was led by G. K. Mirzoev, candidate of technical sciences.
On November 10, 2003, a General Agreement on Cooperation was signed between the Russian Academy of Sciences and the Norilsk Nickel Company in the field of hydrogen energy and fuel cells. This led to the establishment on May 4, 2005 of the National Innovation Company “New Energy Projects” (NIK NEP), which in 2006 produced a backup power plant based on solid polymer electrolyte fuel cells with a capacity of 1 kW. According to the MFD-InfoCenter news agency, MMC Norilsk Nickel is liquidating the New Energy Projects company as part of the decision announced in early 2009 to get rid of non-core and unprofitable assets.
In 2008, the InEnergy company was founded, which is engaged in research and development work in the field of electrochemical technologies and power supply systems. Based on the results of the research, in cooperation with leading institutes of the Russian Academy of Sciences (IPCP, ISTT and IHTT), a number of pilot projects were implemented that showed high efficiency. For the MTS company, a modular backup power system based on hydrogen-air fuel cells was created and put into operation, consisting of a fuel cell, a control system, an electricity storage device and a converter. System power up to 10 kW.
Hydrogen-air energy systems have a number of undeniable advantages, including a wide operating temperature range of the external environment (-40..+60C), high efficiency (up to 60%), absence of noise and vibration, quick start, compactness and environmental friendliness (water, like result of “exhaust”).
The total cost of ownership of hydrogen-air systems is significantly lower than conventional electrochemical batteries. In addition, they have the highest fault tolerance due to the absence of moving parts of the mechanisms, do not require maintenance, and their service life reaches 15 years, exceeding classic electrochemical batteries by up to five times.
Gazprom and the federal nuclear centers of the Russian Federation are working on creating prototypes of fuel cell power plants. Solid oxide fuel cells, the development of which is now actively underway, will appear, apparently, after 2016.
Applications of fuel cells
Fuel cells were initially used only in the space industry, but currently the scope of their application is continuously expanding. They are used in stationary power plants, as autonomous sources of heat and power supply to buildings, in vehicle engines, and as power sources for laptops and mobile phones. Some of these devices have not yet left the walls of laboratories, others are already commercially available and have been in use for a long time.
| Application area | Power | Examples of using |
|---|---|---|
| Stationary installations | 5-250 kW and above | 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 |
| Transport | 25-150 kW | Cars and other vehicles, warships and submarines |
| Portable devices | 1-500 W | Mobile phones, laptops, PDAs, various consumer electronic devices, modern military devices |
High-power power plants based on fuel cells are widely used. Basically, such installations operate on the basis of elements based on molten carbonates, phosphoric acid and solid oxides. As a rule, such installations are used not only to generate electricity, but also to generate heat.
Much effort is being made to develop hybrid plants that combine high-temperature fuel cells with gas turbines. The efficiency of such installations can reach 74.6% with the improvement of gas turbines.
Low-power units based on fuel cells are also being actively produced.
Technical regulation in the field of production and use of fuel cells
On August 19, 2004, the International Electrotechnical Commission (IEC) issued the first international standard, IEC 62282–2 “Fuel Cell Technologies. Part 2, Fuel Cell Modules.” This was the first standard in the IEC 62282 series, developed by the Technical Committee on Fuel Cell Technologies (TC/IEC 105). The Technical Committee TC/IEC 105 includes permanent representatives from 17 countries and observers from 15 countries.
TC/IEC 105 has developed and published 14 international standards in the IEC 62282 series, covering a wide range of topics related to the standardization of fuel cell power plants. The Federal Agency for Technical Regulation and Metrology of the Russian Federation (ROSSTANDART) is a collective member of the Technical Committee TC/IEC 105 as an observer. Coordination activities with the IEC on the part of the Russian Federation are carried out by the secretariat of RosMEK (Rosstandart), and work on the implementation of IEC standards is carried out by the national Technical Committee for Standardization TC 029 “Hydrogen Technologies”, the National Association of Hydrogen Energy (NAVE) and KVT LLC. Currently, ROSSTANDART has adopted the following national and interstate standards, identical to the international IEC standards.
I insert the filler hose fitting into the fuel filler neck and turn it half a turn to seal the connection. A click of the toggle switch - and the blinking LED on the gas pump with a huge inscription h3 indicates that refueling has started. A minute - and the tank is full, you can go!
Elegant body contours, ultra-low suspension, low-profile slicks give off a real racing breed. Through the transparent cover, an intricate network of pipelines and cables is visible. I've already seen a similar solution somewhere... Oh yes, on the Audi R8 the engine is also visible through the rear window. But on Audi it is traditional gasoline, and this car runs on hydrogen. Like the BMW Hydrogen 7, but unlike the latter, there is no internal combustion engine. The only moving parts are the steering gear and the electric motor rotor. And the energy for it is provided by a fuel cell. This car was produced by the Singaporean company Horizon Fuel Cell Technologies, specializing in the development and production of fuel cells. In 2009, the British company Riversimple already introduced an urban hydrogen car powered by Horizon Fuel Cell Technologies fuel cells. It was developed in collaboration with Oxford and Cranfield Universities. But Horizon H-racer 2.0 is a solo development.
The fuel cell consists of two porous electrodes coated with a layer of catalyst and separated by a proton exchange membrane. Hydrogen at the anode catalyst is converted into protons and electrons, which travel through the anode and an external electrical circuit to the cathode, where hydrogen and oxygen recombine to form water.
"Go!" - the editor-in-chief nudges me with his elbow in Gagarin style. But not so fast: first you need to “warm up” the fuel cell at part load. I switch the toggle switch to “warm up” mode and wait for the allotted time. Then, just in case, I top up the tank until it’s full. Now let's go: the car, the engine humming smoothly, moves forward. The dynamics are impressive, although, by the way, what else can you expect from an electric car - the torque is constant at any speed. Although not for long - a full tank of hydrogen lasts only a few minutes (Horizon promises to release a new version in the near future, in which hydrogen is not stored as a gas under pressure, but is retained by a porous material in the adsorber). And, frankly speaking, it is not very controlled - there are only two buttons on the remote control. But in any case, it’s a pity that this is only a radio-controlled toy, which cost us $150. We wouldn't mind driving a real car with fuel cells for power.
The tank, an elastic rubber container inside a rigid casing, stretches when refueling and works as a fuel pump, “squeezing” hydrogen into the fuel cell. In order not to “overfill” the tank, one of the fittings is connected with a plastic tube to the emergency pressure relief valve.
Gas station
Do it yourself
The Horizon H-racer 2.0 machine is supplied as a kit for large-scale assembly (do-it-yourself type), you can buy it, for example, on Amazon. However, assembling it is not difficult - just put the fuel cell in place and secure it with screws, connect the hoses to the hydrogen tank, fuel cell, filler neck and emergency valve, and all that remains is to put the upper part of the body in place, not forgetting the front and rear bumpers. The kit includes a filling station that produces hydrogen by electrolysis of water. It is powered by two AA batteries, and if you want the energy to be completely “clean”, by solar panels (they are also included in the kit).
www.popmech.ru
How to make a fuel cell with your own hands?
Of course, the simplest solution to the problem of ensuring the constant operation of fuel-free systems is to purchase a ready-made secondary energy source on a hydraulic or any other basis, but in this case it will certainly not be possible to avoid additional costs, and in this process it is quite difficult to consider any idea for flight of creative thought. In addition, making a fuel cell with your own hands is not at all as difficult as you might think at first glance, and even the most inexperienced craftsman can cope with the task if desired. In addition, a more than pleasant bonus will be the low cost of creating this element, because despite all its benefits and importance, you can absolutely easily make do with the means you already have at hand.
In this case, the only nuance that must be taken into account before completing the task is that you can make an extremely low-power device with your own hands, and the implementation of more advanced and complex installations should still be left to qualified specialists. As for the order of work and the sequence of actions, the first step is to complete the body, for which it is best to use thick-walled plexiglass (at least 5 centimeters). For gluing the walls of the case and installing internal partitions, for which it is best to use thinner plexiglass (3 millimeters is enough), ideally use two-composite glue, although if you really want, you can do high-quality soldering yourself, using the following proportions: per 100 grams of chloroform - 6 grams shavings from the same plexiglass.
In this case, the process must be carried out exclusively under a hood. In order to equip the case with the so-called drain system, it is necessary to carefully drill a through hole in its front wall, the diameter of which will exactly match the dimensions of the rubber plug, which serves as a kind of gasket between the case and the glass drain tube. As for the size of the tube itself, ideally its width should be five to six millimeters, although it all depends on the type of structure being designed. It is more likely to say that the old gas mask listed in the list of necessary elements for making a fuel cell will cause some surprise among potential readers of this article. Meanwhile, the entire benefit of this device lies in the activated carbon located in the compartments of its respirator, which can later be used as electrodes.
Since we are talking about a powdery consistency, to improve the design you will need nylon stockings, from which you can easily make a bag and put the coal in it, otherwise it will simply spill out of the hole. As for the distribution function, the concentration of fuel occurs in the first chamber, while the oxygen necessary for the normal functioning of the fuel cell, on the contrary, will circulate in the last, fifth compartment. The electrolyte itself, located between the electrodes, should be soaked in a special solution (gasoline with paraffin in a ratio of 125 to 2 milliliters), and this must be done before placing the air electrolyte in the fourth compartment. To ensure proper conductivity, copper plates with pre-soldered wires are laid on top of the coal, through which electricity will be transmitted from the electrodes.
This design stage can be safely considered the final stage, after which the finished device is charged, for which an electrolyte will be needed. In order to prepare it, you need to mix ethyl alcohol with distilled water in equal parts and begin gradually introducing caustic potassium at the rate of 70 grams per glass of liquid. The first test of the manufactured device involves simultaneously filling the first (fuel liquid) and third (electrolyte made from ethyl alcohol and caustic potassium) containers of the plexiglass housing.
uznay-kak.ru
Hydrogen fuel cells | LAVENT
I have long wanted to tell you about another direction of the Alfaintek company. This is the development, sale and service of hydrogen fuel cells. I would like to immediately explain the situation with these fuel cells in Russia.
Due to the fairly high cost and the complete lack of hydrogen stations for charging these fuel cells, their sale in Russia is not expected. Nevertheless, in Europe, especially in Finland, these fuel cells are gaining popularity every year. What's the secret? Let's get a look. This device is environmentally friendly, easy to use and effective. It comes to the aid of a person where he needs electrical energy. You can take it with you on the road, on a hike, or use it in your country house or apartment as an autonomous source of electricity.
Electricity in a fuel cell is generated by a chemical reaction of hydrogen from the tank with metal hydride and oxygen from the air. The cylinder is not explosive and can be stored in your closet for years, waiting in the wings. This is perhaps one of the main advantages of this hydrogen storage technology. It is the storage of hydrogen that is one of the main problems in the development of hydrogen fuel. Unique new lightweight fuel cells that convert hydrogen into conventional electricity safely, quietly and emission-free.
This type of electricity can be used in places where there is no central electricity, or as an emergency power source.
Unlike conventional batteries, which need to be charged and disconnected from the electrical consumer during the charging process, a fuel cell works as a “smart” device. This technology provides uninterrupted power throughout the entire period of use thanks to the unique power saving function when changing the fuel container, which allows the user to never turn off the consumer. In a closed case, fuel cells can be stored for several years without losing the volume of hydrogen and reducing their power.
The fuel cell is designed for scientists and researchers, law enforcement, emergency responders, boat and marina owners, and anyone else who needs a reliable power source in case of emergency. You can get 12 volts or 220 volts and then you will have enough energy to run your TV, stereo, refrigerator, coffee maker, kettle, vacuum cleaner, drill, microstove and other electrical appliances.
Hydrocell fuel cells can be sold as a single unit or in batteries of 2-4 cells. Two or four elements can be combined to either increase power or increase amperage.
OPERATING TIME OF HOUSEHOLD APPLIANCES WITH FUEL CELLS
| Electrical appliances | Operating time per day (min.) | Required power per day (Wh) | Operating time with fuel cells |
|||
| Electric kettle | ||||||
| Coffee maker | ||||||
| Microslab | ||||||
| TV | ||||||
| 1 light bulb 60W | ||||||
| 1 light bulb 75W | ||||||
| 3 bulbs 60W | ||||||
| Computer laptop | ||||||
| Fridge | ||||||
| Energy saving lamp | ||||||
* - continuous operation
Fuel cells are fully charged at special hydrogen stations. But what if you travel far from them and there is no way to recharge? Especially for such cases, Alfaintek specialists have developed cylinders for storing hydrogen, with which fuel cells will work much longer.
Two types of cylinders are available: NS-MN200 and NS-MN1200. The assembled NS-MN200 is slightly larger than a Coca-Cola can, it holds 230 liters of hydrogen, which corresponds to 40Ah (12V), and weighs only 2.5 kg .The metal hydride cylinder NS-MH1200 holds 1200 liters of hydrogen, which corresponds to 220Ah (12V). The weight of the cylinder is 11 kg.
The metal hydride technique is a safe and easy way to store, transport and use hydrogen. When stored as a metal hydride, hydrogen is in the form of a chemical compound rather than a gaseous form. This method makes it possible to obtain a sufficiently high energy density. The advantage of using metal hydride is that the pressure inside the cylinder is only 2-4 bar. The cylinder is not explosive and can be stored for years without reducing the volume of the substance. Since the hydrogen is stored as a metal hydride, the purity of the hydrogen obtained from the cylinder is very high at 99.999%. Metal hydride hydrogen storage cylinders can be used not only with HC 100,200,400 fuel cells, but also in other cases where pure hydrogen is needed. The cylinders can be easily connected to a fuel cell or other device using a quick-connect connector and flexible hose.
It is a pity that these fuel cells are not sold in Russia. But among our population there are so many people who need them. Well, we'll wait and see, and you'll see, we'll have some. In the meantime, we will buy energy-saving light bulbs imposed by the state.
P.S. It looks like the topic has finally faded into oblivion. So many years after this article was written, nothing has come of it. Maybe I’m not looking everywhere, of course, but what catches my eye is not at all pleasing. The technology and idea are good, but they haven’t found any development yet.
lavent.ru
The fuel cell is a future that starts today!
The beginning of the 21st century considers ecology as one of the most important global challenges. And the first thing that should be paid attention to in the current conditions is the search and use of alternative energy sources. They are the ones who are able to prevent pollution of our environment, as well as completely abandon the continuously rising prices of hydrocarbon-based fuels.
Already today, energy sources such as solar cells and wind turbines have found application. But, unfortunately, their disadvantage is associated with dependence on the weather, as well as on the season and time of day. For this reason, their use in astronautics, aircraft and automotive industries is gradually being abandoned, and for stationary use they are equipped with secondary power sources - batteries.
However, the best solution is a fuel cell, since it does not require constant energy recharging. This is a device that is capable of processing and converting various types of fuel (gasoline, alcohol, hydrogen, etc.) directly into electrical energy.
A fuel cell works on the following principle: fuel is supplied from the outside, which is oxidized by oxygen, and the energy released is converted into electricity. This principle of operation ensures almost eternal operation.
Since the end of the 19th century, scientists have studied the fuel cell itself and constantly developed new modifications of it. So, today, depending on operating conditions, there are alkaline or alkaline (AFC), direct borohydrate (DBFC), electro-galvanic (EGFC), direct methanol (DMFC), zinc-air (ZAFC), microbial (MFC), models based on formic acid (DFAFC) and metal hydrides (MHFC) are also known.
One of the most promising is the hydrogen fuel cell. The use of hydrogen in power plants is accompanied by a significant release of energy, and the exhaust from such a device is pure water vapor or drinking water, which does not pose any threat to the environment.
The successful testing of fuel cells of this type on spacecraft has recently aroused considerable interest among manufacturers of electronics and various equipment. Thus, the PolyFuel company presented a miniature hydrogen fuel cell for laptops. But the too high cost of such a device and the difficulties in unhindered refueling limit its industrial production and wide distribution. Honda has also been producing automotive fuel cells for over 10 years. However, this type of transport does not go on sale, but only for the official use of company employees. The cars are under the supervision of engineers.
Many people wonder whether it is possible to assemble a fuel cell with their own hands. After all, a significant advantage of a homemade device will be a minor investment, in contrast to an industrial model. For the miniature model, you will need 30 cm of platinum-coated nickel wire, a small piece of plastic or wood, a 9-volt battery clip and the battery itself, clear adhesive tape, a glass of water and a voltmeter. Such a device will allow you to see and understand the essence of the work, but, of course, it will not be possible to generate electricity for the car.
fb.ru
Hydrogen fuel cells: a little history | Hydrogen
Nowadays, the problem of shortage of traditional energy resources and the deterioration of the planet’s ecology as a whole due to their use is particularly acute. That is why, recently, significant financial resources and intellectual resources have been spent on the development of potentially promising substitutes for hydrocarbon fuels. Hydrogen may become such a substitute in the very near future, since its use in power plants is accompanied by the release of a large amount of energy, and the exhaust is water vapor, that is, it does not pose a danger to the environment.
Despite some technical difficulties that still exist in the implementation of hydrogen-based fuel cells, many car manufacturers have appreciated the promise of the technology and are already actively developing prototypes of production cars capable of using hydrogen as the main fuel. Back in two thousand and eleven, Daimler AG presented conceptual Mercedes-Benz models with hydrogen power plants. In addition, the Korean company Hyndayi has officially announced that it no longer intends to develop electric cars, but will concentrate all its efforts on developing an affordable hydrogen car.
Despite the fact that the very idea of using hydrogen as a fuel is not wild for many, most have no idea how fuel cells using hydrogen work and what is so remarkable about them.
To understand the importance of the technology, we suggest looking at the history of hydrogen fuel cells.
The first person to describe the potential of using hydrogen in a fuel cell was a German, Christian Friedrich. Back in 1838, he published his work in a famous scientific journal of the time.
The very next year, a prototype of a workable hydrogen battery was created by a judge from Uhls, Sir William Robert Grove. However, the power of the device was too small even by the standards of that time, so its practical use was out of the question.
As for the term “fuel cell,” it owes its existence to scientists Ludwig Mond and Charles Langer, who in 1889 attempted to create a fuel cell operating on air and coke oven gas. According to other sources, the term was first used by William White Jaques, who first decided to use phosphoric acid in an electrolyte.
In the 1920s, a number of studies were carried out in Germany, which resulted in the discovery of solid oxide fuel cells and ways to use the carbonate cycle. It is noteworthy that these technologies are effectively used in our time.
In 1932, engineer Francis T Bacon began work on directly researching hydrogen-based fuel cells. Before him, scientists used an established scheme - porous platinum electrodes were placed in sulfuric acid. The obvious disadvantage of such a scheme lies, first of all, in its unjustified high cost due to the use of platinum. In addition, the use of caustic sulfuric acid posed a threat to the health, and sometimes even the life, of researchers. Bacon decided to optimize the circuit and replaced platinum with nickel, and used an alkaline composition as the electrolyte.
Thanks to productive work to improve his technology, Bacon already in 1959 presented to the general public his original hydrogen fuel cell, which produced 5 kW and could power a welding machine. He called the presented device “Bacon Cell”.
In October of the same year, a unique tractor was created that ran on hydrogen and produced twenty horsepower.
In the sixties of the twentieth century, the American company General Electric developed the scheme developed by Bacon and applied it to the Apollo and NASA Gemini space programs. Experts from NASA came to the conclusion that using a nuclear reactor is too expensive, technically difficult and unsafe. In addition, we had to abandon the use of batteries together with solar panels due to their large dimensions. The solution to the problem was hydrogen fuel cells, which are capable of supplying the spacecraft with energy and its crew with clean water.
The first bus using hydrogen as fuel was built back in 1993. And prototypes of passenger cars powered by hydrogen fuel cells were presented already in 1997 by such global automobile brands as Toyota and Daimler Benz.
It’s a little strange that a promising environmentally friendly fuel, sold fifteen years ago in a car, has not yet become widespread. There are many reasons for this, the main ones, perhaps, are political and the demands for creating the appropriate infrastructure. Let's hope that hydrogen will still have its say and become a significant competitor to electric cars.(odnaknopka)
energycraft.org
Created 07/14/2012 20:44 Author: Alexey Norkin
Our material society without energy cannot not only develop, but even exist at all. Where does the energy come from? Until recently, people used only one way to obtain it; we fought with nature, burning the obtained trophies in the furnaces of first home hearths, then steam locomotives and powerful thermal power plants.
There are no labels on the kilowatt-hours consumed by the modern average person that would indicate how many years nature worked so that civilized man could enjoy the benefits of technology, and how many years she still has to work to smooth out the damage caused to her by such a civilization. However, there is a growing understanding in society that sooner or later the illusory idyll will end. Increasingly, people are inventing ways to provide energy for their needs with minimal damage to nature.
Hydrogen fuel cells are the Holy Grail of clean energy. They process hydrogen, one of the common elements of the periodic table, and release only water, the most common substance on the planet. The rosy picture is spoiled by people's lack of access to hydrogen as a substance. There is a lot of it, but only in a bound state, and extracting it is much more difficult than pumping oil out of the depths or digging up coal.
One of the options for clean and environmentally friendly production of hydrogen is microbial fuel cells (MTB), which use microorganisms to decompose water into oxygen and hydrogen. Not everything is smooth here either. Microbes do an excellent job of producing clean fuel, but to achieve the efficiency required in practice, MTB requires a catalyst that accelerates one of the chemical reactions of the process.
This catalyst is the precious metal platinum, the cost of which makes the use of MTB economically unjustified and practically impossible.
Scientists from the University of Wisconsin-Milwaukee have found a replacement for the expensive catalyst. Instead of platinum, they proposed using cheap nanorods made from a combination of carbon, nitrogen and iron. The new catalyst consists of graphite rods with nitrogen embedded in the surface layer and iron carbide cores. During three months of testing the new product, the catalyst demonstrated capabilities higher than those of platinum. The operation of nanorods turned out to be more stable and controllable.
And most importantly, the brainchild of university scientists is much cheaper. Thus, the cost of platinum catalysts is approximately 60% of the cost of MTB, while the cost of nanorods is within 5% of their current price.
According to the creator of catalytic nanorods, Professor Junhong Chen: “Fuel cells can directly convert fuel into electricity. Together, electrical energy from renewable sources can be delivered where it is needed in a clean, efficient and sustainable manner.”
Professor Chen and his team of researchers are now studying the exact characteristics of the catalyst. Their goal is to give their invention a practical focus, to make it suitable for mass production and use.
Based on materials from Gizmag
www.facepla.net
Hydrogen fuel cells and energy systems
A water-powered car may soon become a reality and hydrogen fuel cells will be installed in many homes...
Hydrogen fuel cell technology is not new. It began in 1776, when Henry Cavendish first discovered hydrogen while dissolving metals in dilute acids. The first hydrogen fuel cell was invented already in 1839 by William Grove. Since then, hydrogen fuel cells have been gradually improved and are now installed in space shuttles, supplying them with energy and serving as a source of water. Today, hydrogen fuel cell technology is on the verge of reaching the mass market, in cars, homes and portable devices.
In a hydrogen fuel cell, chemical energy (in the form of hydrogen and oxygen) is converted directly (without combustion) into electrical energy. A fuel cell consists of a cathode, electrodes and an anode. Hydrogen is fed to the anode, where it is separated into protons and electrons. Protons and electrons have different routes to the cathode. Protons move through the electrode to the cathode, and electrons pass around the fuel cells to get to the cathode. This movement creates subsequently usable electrical energy. On the other side, hydrogen protons and electrons combine with oxygen to form water.
Electrolyzers are one way to extract hydrogen from water. The process is basically the opposite of what happens with a hydrogen fuel cell. The electrolyzer consists of an anode, an electrochemical cell and a cathode. Water and voltage are applied to the anode, which splits the water into hydrogen and oxygen. Hydrogen passes through the electrochemical cell to the cathode and oxygen is supplied directly to the cathode. From there, hydrogen and oxygen can be extracted and stored. During times when electricity is not required to be produced, the accumulated gas can be removed from the storage facility and passed back through the fuel cell.
This system uses hydrogen as fuel, which is probably why there are many myths about its safety. After the explosion of the Hindenburg, many people far from science and even some scientists began to believe that the use of hydrogen is very dangerous. However, recent research has shown that the cause of this tragedy was related to the type of material that was used in the construction, and not to the hydrogen that was pumped inside. After testing the safety of hydrogen storage, it was found that storing hydrogen in fuel cells is safer than storing gasoline in a car fuel tank.
How much do modern hydrogen fuel cells cost? Companies currently offer hydrogen fuel systems that produce power for about $3,000 per kilowatt. Marketing research has established that when the cost drops to $1,500 per kilowatt, consumers in the mass energy market will be ready to switch to this type of fuel.
Hydrogen fuel cell vehicles are still more expensive than internal combustion engine vehicles, but manufacturers are exploring ways to bring the price to comparable levels. In some remote areas where there are no power lines, using hydrogen as a fuel or powering the home independently may be more economical right now than, for example, building infrastructure for traditional energy sources.
Why are hydrogen fuel cells still not widely used? At the moment, their high cost is the main problem for the spread of hydrogen fuel cells. Hydrogen fuel systems simply do not have mass demand at the moment. However, science does not stand still and in the near future a car running on water may become a real reality.
www.tesla-tehnika.biz
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.
Rice. 2.
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.
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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.
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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.
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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.
Rice. 6.
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.
Rice. 7.
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.
Rice. 8.
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.
Rice. 9.
9. Comparison of the most important characteristics of fuel cells
Fuel cell type | Operating temperature | Power generation efficiency | Fuel type | Scope of application |
Medium and large installations |
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Pure hydrogen | installations |
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Pure hydrogen | Small installations |
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Most hydrocarbon fuels | Small, medium and large installations |
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Portable installations |
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Pure hydrogen | Space researched |
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Pure hydrogen | Small installations |
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10. Use of fuel cells in cars
Rice. eleven.
Rice. 12.
