Fuel cells utilize the chemical energy of hydrogen to produce electricity and thermal energy. A fuel cell is a quiet, clean source of energy. Fuel cells operate without combustion, so they are virtually pollution free. Water is the only by-product a fuel cell emits if it uses hydrogen directly. Since electrochemical reactions generate energy more efficiently than combustion, fuel cells can achieve higher efficiencies than internal combustion engines, extracting more electricity from the same amount of fuel. Current fuel cell efficiencies are in the 40 to 50 percent range, with up to 80 percent efficiency reported when used in combined heat and power applications. The fuel cell itself has no moving parts - making it a quiet and reliable source of power.
Fuel cells are similar to batteries in that they are composed of positive and negative electrodes with an electrolyte or membrane. The difference between fuel cells and batteries is that energy is not recharged and stored in fuel cells as it is in batteries. Fuel cells receive their energy from the hydrogen or similar fuel that is supplied to them. No charge is thereby necessary.
Fuel cell types include proton exchange membrane (PEM), alkaline, phosphoric acid, molten carbonate, and solid oxide fuel cells. Each of these fuel cell types has its own set of technical challenges, which fuel cell suppliers are working diligently to overcome. PEM fuel cells are compact and efficient, but use membranes that are presently very expensive and require extremely high purity hydrogen. Alkaline and phosphoric acid fuel cells have high sensitivities to carbon dioxide, and molten carbonate and solid oxide fuel cells require exotic processes and extremely high temperature operation.
A PEM fuel cell is composed of an anode (a negative electrode that repels electrons), an electrolyte in the center, and a cathode (a positive electrode that attracts electrons). As hydrogen flows into the fuel cell anode, a platinum catalyst on the anode helps to separate the gas into protons (hydrogen ions) and electrons. The electrolyte in the center allows only the protons to pass through the electrolyte to the cathode side of the fuel cell. The electrons cannot pass through this electrolyte and flow through an external circuit in the form of electric current. This current can power an electric load, such as the electric motor that propels a fuel cell-powered vehicle. As oxygen flows into the fuel cell cathode, another platinum catalyst helps the oxygen, protons, and electrons combine to produce pure water and heat. Individual fuel cells can be combined into a fuel cell "stack." The number of fuel cells in the stack determines the total voltage, and the surface area of each cell determines the total current. Multiplying the voltage by the current yields the total electrical power generated.
In the near term, PEM fuel cells appear to offer the most promising alternative for powering fuel cell vehicles. In addition to being compact, they use a relatively simple process to extract power from hydrogen. Most major automakers and fuel cell-based transportation suppliers are focusing their efforts on development and commercialization of drive systems using PEM fuel cells.
TransPower offers expertise and access to the leading suppliers of PEM fuel cells. In addition to providing fuel cell-related expertise and products, TransPower can assist client-partners in selecting or designing the right fuel cell technology for their vehicle fleets. TransPower can also assist fuel cell suppliers in integrating their products into vehicles, by providing technical expertise, access to fuel cell integrators, and assistance in acquiring funding. TransPower’s Preferred Supplier Network includes the leading suppliers of hydrogen fuel cells.