Fuel cells make it possible to efficiently convert the energy stored in several kinds of gases, among which hydrogen and methane, into electricity. Although the concept, according to which fuel cells operate, was already discovered in 1839 by William Grove, the first development only started in 1932 through Francis Bacon’s exploratory work. It was only in the early 1960s that significant efforts were put into fuel cell development, when NASA decided that fuel cells were to become the principal replacement for batteries in spacecraft (Bacon, 1969 and Schoots et al., 2010). Today, different kind of fuel cells are available in the market, although none of them are fully commercial technologies, yet. Other types of fuel cells are still in the R&D stage. Fuel cells can be used in stationary applications to generate electricity, or electricity and heat. Phosphoric Acid Fuel Cells (PAFC), Alkaline Fuel Cells (AFC), Solid Oxide Fuel Cells (SOFC) and Molten Carbonate Fuel Cells (MCFC) are the most common types of fuel cells for stationary applications. Proton Exchange Membrane (PEM) Fuel Cells, which are mainly used in vehicles, are described in the technology description ‘Fuel cells (mobile applications)’.
Fuel cells are used to produce electricity and are more advanced and energy-efficient technologies than combustion engines, which burn the fuel. Fuel cells operate according to the principle of electrochemical reactions and therefore they function completely different than combustion engines. Figure 1 shows the basic principal of the electrochemical reaction. [media:image:1] In a fuel cell, the fuel, either hydrogen or an organic gas like methane or natural gas, is introduced into a chamber with an electrode, the anode. The anode is connected to another electrode, the cathode, with which it forms a closed electric circuit. An air stream supplying oxygen required for the electrochemical reaction is introduced into a second chamber where the cathode is installed. In the anode, the fuel is decomposed into a positively charged ion of the fuel and a negatively charged electron by an oxidation process. The ion, for example H+, migrates to the cathode chamber through a solid matrix called electrolyte. The electron runs through the circuit from the anode to the cathode. In the cathode, the ions combine with the electrons again and react with the oxygen stream to create water (when hydrogen is used as fuel) or carbon dioxide (when an organic gas is used as fuel). Electricity is generated by the migration of electrons through the electric circuit.
The two main components of a fuel cell power system are the fuel cells, which are ordered in stacks, and the so called “balance of plant, which is composed of all the tubes, pumps, compressors, and electronic systems needed to support the stack of fuel cells and to supply them with fuel at suitable operating conditions (Rivera et al., 2010).
Fuel cells may be used in stationary applications to generate electricity, e.g. for distributed generation or auxiliary power. Some fuel cells can also generate electricity and heat and may be used as co-generation systems in residential buildings, hospitals, swimming pools and other buildings. Figure 2 shows typical applications and characteristics of different types of fuel cells.[media:image:2]
The feasibility of fuel cell use depends on the type of fuel cell.
Alkaline and Phosphoric Acid Fuel Cells (AFC and PAFC) need a stream of hydrogen as fuel. Very few countries have the infrastructure to produce and transport hydrogen in large quantities to end-users. This means that in most cases hydrogen has to be produced and stored on-site. Power systems with high capacity would demand larger amounts of hydrogen which might be unavailable because of limited storage capacity.
Molten Carbonate and Solid Oxide Fuel Cells (MCFC and SOFC) can use either hydrogen or an organic gas (methane, LGP, etc). MCFC and SOFC based fuel cell systems are frequently built together with a reformer that cracks the organic molecules of the gas into hydrogen and carbon dioxide just before they are introduced into the fuel cells. Fuel cells operating on natural gas require the infrastructure to deliver natural gas to end-users.
Maintenance of fuel cell technologies requires a highly qualified workforce. However, generally fuel cells require less maintenance than traditional combustion engines. Fuel cell systems need to be placed in dry, closed rooms in order to protect the electronic components.
Worldwide PAFC, MCFC and SOFC technologies represent more than 75% of the installed capacity of stationary fuel cell systems (see Figure 3) (Adamson K., 2008). These three technologies are in the early commercialization phase. AFC are still under development with some prototypes available in the market. [media:image:3]
The International Energy Agency (IEA) launched an Implementating Agreement on Advanced Fuel Cells in 1990, in which 19 countries are participating today: Australia, Austria, Belgium, Canada, Denmark, Finland, France, Germany, Italy, Japan, Korea, Mexico, Netherlands, Norway, Sweden, Switzerland, Turkey, UK and USA. In addition to R&D and information exchange on stationary fuel cell applications, this implementing agreement targets the following commercialization activities (Williams M., 2009):
- Perform market assessment and monitoring,
- Identify and lower barriers to implementation,
- Develop technical and economically viable stacks and systems,
- Stimulate tools for, and knowledge of, balance of plant,
- Increase the value of demonstration programmes by evaluating test data,
- Contribute to feasibility studies of deployment of FC technologies.
Fuel cell systems are more efficient than combustion engines used to generate electricity. A fuel cell system with cogeneration can achieve more than 60% of efficiency.
A fuel cell running on hydrogen does not cause any CO2 emissions. However, the overall GHG emissions of the system depend on the GHG emissions intensity of the hydrogen production. Fuel cells running on natural gas do produce CO2, but emissions are lower than for combustion engines due to the higher efficiency of fuel cells.
Fuel cells cause less noise during operation than a conventional engine.
Figure 4 shows an estimate of the range of investment costs per type of fuel cell technology for stationary applications. For hydrogen-based fuel cells, hydrogen costs also play an important role to determine total system costs.[media:image:4]
Before fuel cells become competitive with conventional technologies, the costs of fuel cell systems must be further reduced. According to the US Department of Energy (US DOE, 2008), stationary fuel cell systems need to cost no more than $400–$750/kW to be viable for widespread commercialization. Initial commercial applications are expected at about $1000/kW.
[this information is kindly provided by the UNEP Risoe Centre Carbon Markets Group ]
Project developers of fuel cell projects under the CDM would apply the following CDM methdology: AMS-III.AC.: Electricity and/or heat generation using fuel cell . However, as of April 2011, there are no fuel cell projects under the CDM.
Adamson K. (2008). 2008 Large Stationary Survey. In Fuel Cell Today. Available at http://www.fuelcelltoday.com/media/pdf/surveys/2008-LS-Free.pdf 
Bacon, F.T. (1969). Fuel cells, Past, Present and Future. In Electrochimica Acta 14:569-585.
Business Insights (2009). Leading fuel cell technologies. Available at http://www.technologytransfertactics.com/content/wp-content/uploads/2009/07/leading-fuel-cell-technologies-brochure.pdf 
National Institute of Standards and Technology. Website. Available at http://physics.nist.gov/MajResFac/NIF/pemFuelCells.html 
Rivera, R. et al. (2010). Learning curves for Solid Oxide Fuel Cells. World Hydrogen Energy Conference 2010. Essen, Germany.
Schoots K, G.J. Kramer, B.C.C. van der Zwaan (2010). Technology Learning for Fuel Cells: an assessment of past and potential cost reductions. In Energy Policy, 38 (2010) 6:2887-2897
US DOE (2008). Fuel Cell Technology Challenges. Available at http://www1.eere.energy.gov/hydrogenandfuelcells/fuelcells/fc_challenges.html 
US DOE (2010). Fuel Cell Factsheet. Available at http://www1.eere.energy.gov/hydrogenandfuelcells/fuelcells/fc_challenges.html 
Williams, M. (2009). IEA Advanced Fuel Cells Implementing Agreement (IA). US Senate 2009