Fuel cell

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Direct-methanol fuel cell. The actual fuel cell stack is the layered bi-cubic structure in the center of the image

A fuel cell is an electrochemical conversion device. It produces electricity from fuel (on the anode side) and an oxidant (on the cathode side), which react in the presence of an electrolyte. The reactants flow into the cell, and the reaction products flow out of it, while the electrolyte remains within it. Fuel cells can operate virtually continuously as long as the necessary flows are maintained.

Fuel cells are different from electrochemical cell batteries in that they consume reactant, which must be replenished[citation needed], whereas batteries store electrical energy chemically in a closed system. Additionally, while the electrodes within a battery react and change as a battery is charged or discharged, a fuel cell's electrodes are catalytic and relatively stable.

Many combinations of fuel and oxidant are possible. A hydrogen cell uses hydrogen as fuel and oxygen (usually from air) as oxidant. Other fuels include hydrocarbons and alcohols. Other oxidants include chlorine and chlorine dioxide.[1]

Contents

[edit] Fuel cell design

A fuel cell works by catalysis, separating the component electrons and protons of the reactant fuel, and forcing the electrons to travel though a circuit, hence converting them to electrical power. The catalyst typically comprises a platinum group metal or alloy. Another catalytic process takes the electrons back in, combining them with the protons and oxidant to form waste products (typically simple compounds like water and carbon dioxide).

In the archetypal hydrogen–oxygen proton exchange membrane fuel cell (PEMFC) design, a proton-conducting polymer membrane, (the electrolyte), separates the anode and cathode sides. This was called a "solid polymer electrolyte fuel cell" (SPEFC) in the early 1970s, before the proton exchange mechanism was well-understood. (Notice that "polymer electrolyte membrane" and "proton exchange membrane" result in the same acronym.)

On the anode side, hydrogen diffuses to the anode catalyst where it later dissociates into protons and electrons. These protons often react with oxidants causing them to become what is commonly referred to as multi-facilitated proton membranes (MFPM). The protons are conducted through the membrane to the cathode, but the electrons are forced to travel in an external circuit (supplying power) because the membrane is electrically insulating. On the cathode catalyst, oxygen molecules react with the electrons (which have traveled through the external circuit) and protons to form water — in this example, the only waste product, either liquid or vapor.

In addition to this pure hydrogen type, there are hydrocarbon fuels for fuel cells, including diesel, methanol (see: direct-methanol fuel cells and indirect methanol fuel cells) and chemical hydrides. The waste products with these types of fuel are carbon dioxide and water.

Construction of a high temperature PEMFC: Bipolar plate as electrode with in-milled gas channel structure, fabricated from conductive plastics (enhanced with carbon nanotubes for more conductivity); Porous carbon papers; reactive layer, usually on the polymer membrane applied; polymer membrane.
Condensation of water produced by a PEMFC on the air channel wall. The gold wire around the cell ensures the collection of electric current.[2]

The materials used in fuel cells differ by type. In a typical membrane electrode assembly (MEA), the electrode–bipolar plates are usually made of metal, nickel or carbon nanotubes, and are coated with a catalyst (like platinum, nano iron powders or palladium) for higher efficiency. Carbon paper separates them from the electrolyte. The electrolyte could be ceramic or a membrane.

A typical PEM fuel cell produces a voltage from 0.6 V to 0.7 V at full rated load. Voltage decreases as current increases, due to several factors:

  • Activation loss
  • Ohmic loss (voltage drop due to resistance of the cell components and interconnects)
  • Mass transport loss (depletion of reactants at catalyst sites under high loads, causing rapid loss of voltage)[3]

To deliver the desired amount of energy, the fuel cells can be combined in series and parallel circuits, where series yield higher voltage, and parallel allows a stronger current to be drawn. Such a design is called a fuel cell stack. Further, the cell surface area can be increased, to allow stronger current from each cell.

[edit] Fuel cell design issues

  • Costs. In 2002, typical cells had a catalyst content of US$1000 per kilowatt of electric power output. In 2008 UTC Power has 400kw Fuel cells for $1,000,000 per 400kW installed costs. The goal is to reduce the cost in order to compete with current market technologies including gasoline internal combustion engines. Many companies are working on techniques to reduce cost in a variety of ways including reducing the amount of platinum needed in each individual cell. Ballard Power Systems have experiments with a catalyst enhanced with carbon silk which allows a 30% reduction (1 mg/cm² to 0.7 mg/cm²) in platinum usage without reduction in performance.[4]. Monash University, Melbourne uses PEDOT instead of platinum.[5]
  • The production costs of the PEM (proton exchange membrane). The Nafion membrane currently costs €400/m². In 2005 Ballard Power Systems announced that its fuel cells will use Solupor, a porous polyethylene film patented by DSM.[6][7]
  • Water and air management[8] (in PEMFCs). In this type of fuel cell, the membrane must be hydrated, requiring water to be evaporated at precisely the same rate that it is produced. If water is evaporated too quickly, the membrane dries, resistance across it increases, and eventually it will crack, creating a gas "short circuit" where hydrogen and oxygen combine directly, generating heat that will damage the fuel cell. If the water is evaporated too slowly, the electrodes will flood, preventing the reactants from reaching the catalyst and stopping the reaction. Methods to manage water in cells are being developed like electroosmotic pumps focusing on flow control. Just as in a combustion engine, a steady ratio between the reactant and oxygen is necessary to keep the fuel cell operating efficiently.
  • Temperature management. The same temperature must be maintained throughout the cell in order to prevent destruction of the cell through thermal loading. This is particularly challenging as the 2H2 + O2 -> 2H2O reaction is highly exothermic, so a large quantity of heat is generated within the fuel cell.
  • Durability, service life, and special requirements for some type of cells. Stationary fuel cell applications typically require more than 40,000 hours of reliable operation at a temperature of -35 °C to 40 °C (-31 °F to 104 °F), while automotive fuel cells require a 5,000 hour lifespan (the equivalent of 150,000 miles) under extreme temperatures. Automotive engines must also be able to start reliably at -30 °C (-22 °F) and have a high power to volume ratio (typically 2.5 kW per liter).
  • Limited carbon monoxide tolerance of the anode.

[edit] History

Sketch of William Grove's 1839 fuel cell

The principle of the fuel cell was discovered by German scientist Christian Friedrich Schönbein in 1838 and published in one of the scientific magazines of the time.[9] Based on this work, the first fuel cell was demonstrated by Welsh scientist Sir William Robert Grove in the February 1839 edition of the Philosophical Magazine and Journal of Science[10] and later sketched, in 1842, in the same journal.[11] The fuel cell he made used similar materials to today's phosphoric-acid fuel cell.

In 1955, W. Thomas Grubb, a chemist working for the General Electric Company (GE), further modified the original fuel cell design by using a sulphonated polystyrene ion-exchange membrane as the electrolyte. Three years later another GE chemist, Leonard Niedrach, devised a way of depositing platinum onto the membrane, which served as catalyst for the necessary hydrogen oxidation and oxygen reduction reactions. This became known as the 'Grubb-Niedrach fuel cell'. GE went on to develop this technology with NASA and McDonnell Aircraft, leading to its use during Project Gemini. This was the first commercial use of a fuel cell. It wasn't until 1959 that British engineer Francis Thomas Bacon successfully developed a 5 kW stationary fuel cell. In 1959, a team led by Harry Ihrig built a 15 kW fuel cell tractor for Allis-Chalmers which was demonstrated across the US at state fairs. This system used potassium hydroxide as the electrolyte and compressed hydrogen and oxygen as the reactants. Later in 1959, Bacon and his colleagues demonstrated a practical five-kilowatt unit capable of powering a welding machine. In the 1960s, Pratt and Whitney licensed Bacon's U.S. patents for use in the U.S. space program to supply electricity and drinking water (hydrogen and oxygen being readily available from the spacecraft tanks).

United Technologies Corporation's UTC Power subsidiary was the first company to manufacture and commercialize a large, stationary fuel cell system for use as a co-generation power plant in hospitals, universities and large office buildings. UTC Power continues to market this fuel cell as the PureCell 200, a 200 kW system.[12] UTC Power continues to be the sole supplier of fuel cells to NASA for use in space vehicles, having supplied the Apollo missions,[13] and currently the Space Shuttle program, and is developing fuel cells for automobiles, buses, and cell phone towers; the company has demonstrated the first fuel cell capable of starting under freezing conditions with its proton exchange membrane automotive fuel cell.

[edit] Types of fuel cells

Fuel Cell Name Electrolyte Qualified Power (W) Working Temperature (°C) Electrical efficiency Status Cost per Watt
Metal hydride fuel cell Aqueous alkaline solution (e.g.potassium hydroxide)
above -20
(50% Ppeak @ 0°C)

Commercial/Research
Electro-galvanic fuel cell Aqueous alkaline solution (e.g., potassium hydroxide)
under 40
Commercial/Research
Direct formic acid fuel cell (DFAFC) Polymer membrane (ionomer) to 50 W under 40
Commercial/Research
Zinc-air battery Aqueous alkaline solution (e.g., potassium hydroxide)
under 40
Mass production
Microbial fuel cell Polymer membrane or humic acid
under 40
Research
Upflow microbial fuel cell (UMFC)
under 40
Research
Regenerative fuel cell Polymer membrane (ionomer)
under 50
Commercial/Research
Direct borohydride fuel cell Aqueous alkaline solution (e.g., sodium hydroxide)
70
Commercial
Alkaline fuel cell Aqueous alkaline solution (e.g., potassium hydroxide) 10 kW to 100 kW under 80 Cell: 60–70%
System: 62%
Commercial/Research
Direct methanol fuel cell Polymer membrane (ionomer) 100 kW to 1 MW 90–120 Cell: 20–30%
System: 10–20%
Commercial/Research
Reformed methanol fuel cell Polymer membrane (ionomer) 5 W to 100 kW (Reformer)250–300
(PBI)125–200
Cell: 50–60%
System: 25–40%
Commercial/Research
Direct-ethanol fuel cell Polymer membrane (ionomer) up to 140 mW/cm² above 25
? 90–120

Research
Direct formic acid fuel cell Polymer membrane (ionomer)
25+
Research
Proton exchange membrane fuel cell Polymer membrane (ionomer) (e.g., Nafion or Polybenzimidazole fiber) 100 W to 500 kW (Nafion)50–120
(PBI)125–220
Cell: 50–70%
System: 30–50%
Commercial/Research
RFC - Redox Liquid electrolytes with redox shuttle & polymer membrane (Ionomer) 1 kW to 10 MW

Research
Phosphoric acid fuel cell Molten phosphoric acid (H3PO4) up to 10 MW 150-200 Cell: 55%
System: 40%
Co-Gen: 90%
Commercial/Research $4-$4.50 per watt
Molten carbonate fuel cell Molten alkaline carbonate (e.g., sodium bicarbonate NaHCO3) 100 MW 600-650 Cell: 55%
System: 47%
Commercial/Research
Tubular solid oxide fuel cell (TSOFC) O2--conducting ceramic oxide (e.g., zirconium dioxide, ZrO2) up to 100 MW 850-1100 Cell: 60–65%
System: 55–60%
Commercial/Research
Protonic ceramic fuel cell H+-conducting ceramic oxide
700
Research
Direct carbon fuel cell Several different
700-850 Cell: 80%
System: 70%
Commercial/Research
Planar Solid oxide fuel cell O2--conducting ceramic oxide (e.g., zirconium dioxide, ZrO2 Lanthanum Nickel Oxide La2XO4,X= Ni,Co, Cu.) up to 100 MW 850-1100 Cell: 60–65%
System: 55–60%
Commercial/Research

[edit] Efficiency

[edit] Fuel cell efficiency

The efficiency of a fuel cell is dependent on the amount of power drawn from it. Drawing more power means drawing more current, which increases the losses in the fuel cell. As a general rule, the more power (current) drawn, the lower the efficiency. Most losses manifest themselves as a voltage drop in the cell, so the efficiency of a cell is almost proportional to its voltage. For this reason, it is common to show graphs of voltage versus current (so-called polarization curves) for fuel cells. A typical cell running at 0.7 V has an efficiency of about 50%, meaning that 50% of the energy content of the hydrogen is converted into electrical energy; the remaining 50% will be converted into heat. (Depending on the fuel cell system design, some fuel might leave the system unreacted, constituting an additional loss.)

For a hydrogen cell operating at standard conditions with no reactant leaks, the efficiency is equal to the cell voltage divided by 1.48 V, based on the enthalpy, or heating value, of the reaction. For the same cell, the second law efficiency is equal to cell voltage divided by 1.23 V. (This voltage varies with fuel used, and quality and temperature of the cell.) The difference between these numbers represents the difference between the reaction's enthalpy and Gibbs free energy. This difference always appears as heat, along with any losses in electrical conversion efficiency.

Fuel cells do not operate on a thermal cycle. As such, they are not constrained, as combustion engines are, in the same way by thermodynamic limits, such as Carnot cycle efficiency. At times this is misrepresented by saying that fuel cells are exempt from the laws of thermodynamics, because most people think of thermodynamics in terms of combustion processes (enthalpy of formation). The laws of thermodynamics also hold for chemical processes (Gibbs free energy) like fuel cells, but the maximum theoretical efficiency is higher (83% efficient at 298K [14]) than the Otto cycle thermal efficiency (60% for compression ratio of 10 and specific heat ratio of 1.4). Comparing limits imposed by thermodynamics is not a good predictor of practically achievable efficiencies. Also, if propulsion is the goal, electrical output of the fuel cell has to still be converted into mechanical power with the corresponding inefficiency. In reference to the exemption claim, the correct claim is that the "limitations imposed by the second law of thermodynamics on the operation of fuel cells are much less severe than the limitations imposed on conventional energy conversion systems".[15] Consequently, they can have very high efficiencies in converting chemical energy to electrical energy, especially when they are operated at low power density, and using pure hydrogen and oxygen as reactants.

[edit] In practice

For a fuel cell operating on air (rather than bottled oxygen), losses due to the air supply system must also be taken into account. This refers to the pressurization of the air and dehumidifying it. This reduces the efficiency significantly and brings it near to that of a compression ignition engine. Furthermore fuel cell efficiency decreases as load increases.

The tank-to-wheel efficiency of a fuel cell vehicle is about 45% at low loads and shows average values of about 36% when a driving cycle like the NEDC (New European Driving Cycle) is used as test procedure.[16] The comparable NEDC value for a Diesel vehicle is 22%. In 2008 Honda released a car with fuel stack claiming a 60% tank-to-wheel efficiency [17].

It is also important to take losses due to fuel production, transportation, and storage into account. Fuel cell vehicles running on compressed hydrogen may have a power-plant-to-wheel efficiency of 22% if the hydrogen is stored as high-pressure gas, and 17% if it is stored as liquid hydrogen.[18] In addition to the production losses, over 70% of US' electricity, used for hydrogen production, comes from thermal power, which only has an efficiency of 33% to 48% resulting in a net increase in carbon dioxide production by using hydrogen in vehicles[citation needed].

Fuel cells cannot store energy like a battery, but in some applications, such as stand-alone power plants based on discontinuous sources such as solar or wind power, they are combined with electrolyzers and storage systems to form an energy storage system. The overall efficiency (electricity to hydrogen and back to electricity) of such plants (known as round-trip efficiency) is between 30 and 50%, depending on conditions.[19] While a much cheaper lead-acid battery might return about 90%, the electrolyzer/fuel cell system can store indefinite quantities of hydrogen, and is therefore better suited for long-term storage.

Solid-oxide fuel cells produce exothermic heat from the recombination of the oxygen and hydrogen. The ceramic can run as hot as 800 degrees Celsius. This heat can be captured and used to heat water in a micro combined heat and power (m-CHP) application. When the heat is captured, total efficiency can reach 80-90% at the unit, but does not consider production and distribution losses. CHP units are being developed today for the European home market.

[edit] Fuel cell applications

Further information: Fuel cell vehicleStationary fuel cell applications, and Portable fuel cell applications
Type 212 submarine with fuel cell propulsion of the German Navy in dry dock

Fuel cells are very useful as power sources in remote locations, such as spacecraft, remote weather stations, large parks, rural locations, and in certain military applications. A fuel cell system running on hydrogen can be compact and lightweight, and have no major moving parts. Because fuel cells have no moving parts and do not involve combustion, in ideal conditions they can achieve up to 99.9999% reliability.[20] This equates to around one minute of down time in a two year period.

Micro combined heat and power systems such as home fuel cells and cogeneration for office buildings and factories are in mass production phase. The stationary fuel cell application generates constant electric power (selling excess power back to the grid when it is not consumed), and at the same time produces hot air and water from the waste heat. A lower fuel-to-electricity conversion efficiency is tolerated (typically 15-20%), because most of the energy not converted into electricity is utilized as heat. Some heat is lost with the exhaust gas just as in a normal furnace, so the combined heat and power efficiency is still lower than 100%, typically around 80%. In terms of exergy however, the process is inefficient, and one could do better by maximizing the electricity generated and then using the electricity to drive a heat pump. Phosphoric-acid fuel cells (PAFC) comprise the largest segment of existing CHP products worldwide and can provide combined efficiencies close to 90%[21] (35-50% electric + remainder as thermal) Molten-carbonate fuel cells have also been installed in these applications, and solid-oxide fuel cell prototypes exist.

The world's first certified Fuel Cell Boat (HYDRA), in Leipzig/Germany

Since electrolyzer systems do not store fuel in themselves, but rather rely on external storage units, they can be successfully applied in large-scale energy storage, rural areas being one example. In this application, batteries would have to be largely oversized to meet the storage demand, but fuel cells only need a larger storage unit (typically cheaper than an electrochemical device).

One such pilot program is operating on Stuart Island in Washington State. There the Stuart Island Energy Initiative[22] has built a complete, closed-loop system: Solar panels power an electrolyzer which makes hydrogen. The hydrogen is stored in a 500 gallon tank at 200 PSI, and runs a ReliOn fuel cell to provide full electric back-up to the off-the-grid residence. The SIEI website gives extensive technical details.

The world's first Fuel Cell Boat HYDRA used an AFC system with 6.5 kW net output.

[edit] Suggested applications

[edit] Hydrogen transportation and refueling

Toyota FCHV PEM FC fuel cell vehicle

The first public hydrogen refueling station was opened in Reykjavík, Iceland in April 2003. This station serves three buses built by DaimlerChrysler that are in service in the public transport net of Reykjavík. The station produces the hydrogen it needs by itself, with an electrolyzing unit (produced by Norsk Hydro), and does not need refilling: all that enters is electricity and water. Royal Dutch Shell is also a partner in the project. The station has no roof, in order to allow any leaked hydrogen to escape to the atmosphere.

The GM 1966 Electrovan was the automotive industry's first attempt at an automobile powered by a hydrogen fuel cell. The Electrovan, which weighed more than twice as much as a normal van, could travel up to 70mph for 30 seconds.[16][23]

The 2001 Chrysler Natrium used its own on-board hydrogen processor. It produces hydrogen for the fuel cell by reacting sodium borohydride fuel with Borax, both of which Chrysler claimed were naturally occurring in great quantity in the United States.[24] The hydrogen produces electric power in the fuel cell for near-silent operation and a range of 300 miles without impinging on passenger space. Chrysler also developed vehicles which separated hydrogen from gasoline in the vehicle, the purpose being to reduce emissions without relying on a nonexistent hydrogen infrastructure and to avoid large storage tanks.[25]

In 2003 President George Bush proposed what is called the Hydrogen Fuel Initiative (HFI), which was later implemented by legislation through the 2005 Energy Policy Act and the 2006 Advanced Energy Initiative. These aim at further developing hydrogen fuel cells and its infrastructure technologies with the ultimate goal to produce fuel cell vehicles that are both practical and cost-effective by 2020. Thus far the United States has contributed 1 billion dollars to this project.[26]

In 2005 the British firm Intelligent Energy produced the first ever working hydrogen run motorcycle called the ENV (Emission Neutral Vehicle). The motorcycle holds enough fuel to run for four hours, and to travel 100 miles in an urban area, at a top speed of 50 miles per hour.[27] In 2004 Honda developed a fuel-cell motorcycle which utilized the Honda FC Stack.[28][29]

A hydrogen fuel cell public bus accelerating at traffic lights in Perth, Western Australia

There are numerous prototype or production cars and buses based on fuel cell technology being researched or manufactured. Research is ongoing at a variety of motor car manufacturers. Honda has released a hydrogen vehicle, the FCX Verity earlier in 2008.[30] Meanwhile there exist also other examples of bikes[31] and bicycles[32] with a hydrogen fuel cell engine.

Type 212 submarines use fuel cells to remain submerged for weeks without the need to surface.

Boeing researchers and industry partners throughout Europe are planning to conduct experimental flight tests in 2007 of a manned airplane powered only by a fuel cell and lightweight batteries. The Fuel Cell Demonstrator Airplane research project was completed recently and thorough systems integration testing is now under way in preparation for upcoming ground and flight testing. The Boeing demonstrator uses a Proton Exchange Membrane (PEM) fuel cell/lithium-ion battery hybrid system to power an electric motor, which is coupled to a conventional propeller.

Fuel cell powered race vehicles, designed and built by university students from around the world, competed in the world's first hydrogen race series called the 2008 Formula Zero Championship, which began on August 22nd, 2008 in Rotterdam, the Netherlands. The next race is in South Carolina in March 2009.

[edit] Market structure

Not all geographic markets are ready for SOFC powered m-CHP appliances. Currently, the regions that lead the race in Distributed Generation and deployment of fuel cell m-CHP units are the EU and Japan.[33]

[edit] Hydrogen economy

Main article: Hydrogen economy

Electrochemical extraction of energy from hydrogen via fuel cells is an especially clean method of meeting power requirements, but not an efficient one, due to the necessity of adding large amounts of energy to either water or hydrocarbon fuels in order to produce the hydrogen. Additionally, during the extraction of hydrogen from hydrocarbons, carbon monoxide is released. Although this gas is artificially converted into carbon dioxide, such a method of extracting hydrogen remains environmentally injurious. It must however be noted that regarding the concept of the hydrogen vehicle, burning/combustion of hydrogen in an internal combustion engine (IC/ICE) is often confused with the electrochemical process of generating electricity via fuel cells (FC) in which there is no combustion (though there is a small byproduct of heat in the reaction). Both processes require the establishment of a hydrogen economy before they may be considered commercially viable, and even then, the aforementioned energy costs make a hydrogen economy of questionable environmental value. Hydrogen combustion is similar to petroleum combustion, and like petroleum combustion, still results in nitrogen oxides as a by-product of the combustion, which lead to smog. Hydrogen combustion, like that of petroleum, is limited by the Carnot efficiency, but is completely different from the hydrogen fuel cell's chemical conversion process of hydrogen to electricity and water without combustion. Hydrogen fuel cells emit only water during use, while producing carbon dioxide emissions during the majority of hydrogen production, which comes from natural gas. Direct methane or natural gas conversion (whether IC or FC) also generate carbon dioxide emissions, but direct hydrocarbon conversion in high-temperature fuel cells produces lower carbon dioxide emissions than either combustion of the same fuel (due to the higher efficiency of the fuel cell process compared to combustion), and also lower carbon dioxide emissions than hydrogen fuel cells, which use methane less efficiently than high-temperature fuel cells by first converting it to high purity hydrogen by steam reforming. Although hydrogen can also be produced by electrolysis of water using renewable energy, at present less than 3% of hydrogen is produced in this way.

Hydrogen is an energy carrier, and not an energy source, because it is usually produced from other energy sources via petroleum combustion, wind power, or solar photovoltaic cells. Hydrogen may be produced from subsurface reservoirs of methane and natural gas by a combination of steam reforming with the water gas shift reaction, from coal by coal gasification, or from oil shale by oil shale gasification.[citation needed] low pressure electrolysis of water or high pressure electrolysis, which requires electricity, and high-temperature electrolysis/thermochemical production, which requires low temperatures (ideal the for expected Generation IV reactors), are two primary methods for the extraction of hydrogen from water.

As of 2006, 49.0% of the electricity produced in the United States comes from coal, 19.4% comes from nuclear, 20.0% comes from natural gas, 7.0% from hydroelectricity, 1.6% from petroleum and the remaining 3.1% mostly coming from geothermal, solar and biomass.[34] When hydrogen is produced through electrolysis, the energy comes from these sources. Though the fuel cell itself will only emit heat and water as waste, pollution is often caused when generating the electricity required to produce the hydrogen that the fuel cell uses as its power source (for example, when coal, oil, or natural gas-generated electricity is used). This will be the case unless the hydrogen is produced using electricity generated by hydroelectric, geothermal, solar, wind or other clean power sources (which may or may not include nuclear power, depending on one's attitude to the nuclear waste byproducts); hydrogen is only as clean as the energy sources used to produce it. A holistic approach has to take into consideration the impacts of an extended hydrogen scenario, including the production, the use and the disposal of infrastructure and energy converters.

Nowadays low temperature fuel cell stacks proton exchange membrane fuel cell (PEMFC), direct methanol fuel cell (DMFC) and phosphoric acid fuel cell (PAFC) make extensive use of catalysts. Impurities create catalyst poisoning (reducing activity and efficiency), thus high hydrogen purity or higher catalyst densities are required.[35] Limited reserves of platinum quicken the synthesis of an inorganic complex. Although platinum is seen by some as one of the major "showstoppers" to mass market fuel cell commercialization companies, most predictions of platinum running out and/or platinum prices soaring do not take into account effects of thrifting (reduction in catalyst loading) and recycling. Recent research at Brookhaven National Laboratory could lead to the replacement of platinum by a gold-palladium coating which may be less susceptible to poisoning and thereby improve fuel cell lifetime considerably.[36] Current targets for a transport PEM fuel cells are 0.2 g/kW Pt – which is a factor of 5 decrease over current loadings – and recent comments from major original equipment manufacturers (OEMs) indicate that this is possible. Also it is fully anticipated that recycling of fuel cells components, including platinum, will kick-in. High-temperature fuel cells, including molten carbonate fuel cells (MCFC's) and solid oxide fuel cells (SOFC's), do not use platinum as catalysts, but instead use cheaper materials such as nickel and nickel oxide, which are considerably more abundant (for example, nickel is used in fairly large quantities in common stainless steel).

[edit] Research and development

  • August 2005: Georgia Institute of Technology researchers use triazole to raise the operating temperature of PEM fuel cells from below 100 °C to over 125 °C, claiming this will require less carbon-monoxide purification of the hydrogen fuel.[37]
  • 2006: Staxon introduced an inexpensive OEM fuel cell module for system integration. In 2006 Angstrom Power, a British Columbia based company, began commercial sales of portable devices using proprietary hydrogen fuel cell technology, trademarked as "micro hydrogen."[38][39]

[edit] See also

[edit] References

  1. ^ S. G. Meibuhr, Electrochim. Acta, 11, 1301 (1966)
  2. ^ LEMTA - Our fuel cells
  3. ^ Larminie, James (1 May 2003). Fuel Cell Systems Explained, Second Edition. SAE International. ISBN 0768012597. 
  4. ^ "Ballard Power Systems: Commercially Viable Fuel Cell Stack Technology Ready by 2010" (2005-03-29). Retrieved on 27 May 2007. 
  5. ^ 2008 - Cathodes in fuel cells
  6. ^ EP patent 0950075, "Electrolytic Membrane, Method of Manufacturing it and Use", granted 2003-02-12, assigned to DSM 
  7. ^ "Ballard Uses Solupor" (2005-09-13). Retrieved on 2007-05-27.
  8. ^ Water_and_Air_Management
  9. ^ George Wand. "Fuel Cells History, part 1" (pdf) 14. Johnson Matthey plc. Retrieved on 2008-10-06. "In January of 1839 the German/Swiss chemist Christian Friedrich Schönbein wrote an article in one of the scientific magazines of the time about his discovery of ozone and about the reaction of hydrogen and oxygen. But it was no other than William Grove to document just one month later, in February of 1839, his observations in the "Philosophical Magazine". He had conducted a series of experiments with his second invention which he termed a “gas voltaic battery”."
  10. ^ Grove, William Robert "On Voltaic Series and the Combination of Gases by Platinum", Philosophical Magazine and Journal of Science vol. XIV (1839), pp 127-130.
  11. ^ Grove, William Robert "On a Gaseous Voltaic Battery", Philosophical Magazine and Journal of Science vol. XXI (1842), pp 417-420.
  12. ^ "The PureCell 200 - Product Overview". UTC Power. Retrieved on 2007-05-27.
  13. ^ Apollo Space Program Hydrogen Fuel Cells
  14. ^ Fuel Cell efficiency
  15. ^ "About Fuel Cells". MIT / NASA. Retrieved on 2007-05-27.
  16. ^ a b "Fuel Cell Vehicles:Status 2007". Journal of Power Sources. 2007-03-20. doi:10.1016/j.jpowsour.2006.12.073. 
  17. ^ "Honda FCX Clarity - Fuel cell comparison". Retrieved on 2009-01-02.
  18. ^ "Efficiency of Hydrogen PEFC, Diesel-SOFC-Hybrid and Battery Electric Vehicles" (PDF) (2003-07-15). Retrieved on 2007-05-23.
  19. ^ Round Trip Energy Efficiency of NASA Glenn Regenerative Fuel Cell System. Preprint. January 2006. http://hdl.handle.net/2060/20060008706. Retrieved on 27 May 2007. 
  20. ^ "Fuel Cell Basics: Benefits". Fuel Cells 2000. Retrieved on 2007-05-27.
  21. ^ "Fuel Cell Efficiency". UTC Power. Retrieved on 2007-11-16.
  22. ^ Stuart Island Energy Initiative
  23. ^ "An Electrovan, Not an Edsel" by Danny Hakim. New York Times. New York, N.Y.: November 17, 2002. pg. 3.2
  24. ^ natrium
  25. ^ "Chrysler Fuel Cell Vehicles". allpar.com. Retrieved on 2007-05-27.
  26. ^ Nice, Karim, and Jonathan Strickland. "How Fuel Cells Work." How Stuff Works. 30 Oct. 2008. 3 Nov. 2008 <http://www.howstuffworks.com/fuel-cell.htm>.
  27. ^ "The ENV Bike". Intelligent Energy. Retrieved on 2007-05-27.
  28. ^ "Honda Develops Fuel Cell Scooter Equipped with Honda FC Stack", Honda Motor Co. (2004-08-24). Retrieved on 27 May 2007. 
  29. ^ Bryant, Eric (2005-07-21). "Honda to offer fuel-cell motorcycle". autoblog.com. Retrieved on 2007-05-27.
  30. ^ "Honda readies fuel-cell car for 2008 launch", CBC News (2006-09-25). Retrieved on 27 May 2007. 
  31. ^ http://de.youtube.com/watch?v=B_Whbb_hlPs Hydrogen Fuel Cell electric bike
  32. ^ http://www.horizonfuelcell.com/ Horizon fuel cell vehicles
  33. ^ m-CHP
  34. ^ EIA - Electricity Data, Analysis, Surveys
  35. ^ Faur-Ghenciu, Anca (April/May 2003) (PDF). Fuel Processing Catalysts for Hydrogen Reformate Generation for PEM Fuel Cells. FuelCell Magazine. http://www.fuelcell-magazine.com/eprints/free/johnsonmattheyapril03.pdf. Retrieved on 27 May 2007. 
  36. ^ Johnson, R. Colin (2007-01-22). "Gold is key to ending platinum dissolution in fuel cells", EETimes.com. Retrieved on 27 May 2007. 
  37. ^ "Chemical Could Revolutionize Polymer Fuel Cells", Georgia Institute of Technology (2005-08-24). Retrieved on 27 May 2007. 
  38. ^ "Angstrom Power products". Retrieved on 2007-07-03.
  39. ^ "Micro-Fuel Cell Blog". Retrieved on 2007-07-03.

[edit] External links

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