Fuel Cells
What are fuel cells?
Fuel cells are devices for generating electric power. They share many of the characteristics of a battery - silent operation, no moving parts and an electrochemical reaction to generate power. However, unlike a battery, fuel cells need no recharging and will run indefinitely when supplied with fuel. The cells produce electricity by combining hydrogen (the fuel) and oxygen (from air) over a catalyst such as platinum.
There are several different types of fuel cell but the most researched type is the proton exchange membrane (PEM) fuel cell, which contains platinum catalysts. PEM fuel cells are capable of being used in power generation for buildings, instead of batteries or generators in portable equipment and as replacements for the internal combustion engine in a vehicle.
Fuel cells for transport
In 1997, Daimler-Chrysler, Ford and Ballard Power Systems joined together in a consortium to build fuel cell engines and drive trains for cars. DaimlerChrysler, Ford, Honda and Toyota now have small demonstration fleets of cars in operation. A total of 30 fuel cell buses built by DaimlerChrysler and Ballard went into service around Europe in 2004. This project will demonstrate the technology and increase public awareness of fuel cells.
Why fuel cells for vehicles?
The advantages of fuel cells for transport are both environmental and economic. The only emissions from a fuel cell vehicle come from the generation of hydrogen. These emissions are hardly measurable, making fuel cell vehicles virtually equivalent to zero-emission vehicles.
Fuel cell cars will have similar range and performance to cars with internal combustion engines, but the superior energy efficiency of fuel cell engines will bring a significant reduction in carbon dioxide, a greenhouse gas, for every mile travelled. If fuelled directly by hydrogen, there will be no carbon dioxide emissions at all.
Fuel cells for stationary power
Fuel cells can also provide electric power for homes and offices. In these applications, heat produced by the cell can be circulated like the heat from a conventional boiler. Using the combined heat and power in this way considerably raises the efficiency of the system. A small number of such units are already in use in the USA, Europe and Japan to power hospitals and industrial plant and to provide grid-independent, uninterrupted power supply.
Portable fuel cells
Fuel cells can compete with batteries and generators for portable use, from a few kilowatts to power a mobile home down to a few watts to power a laptop computer. Prototypes have been publicly shown of this type of technology and fuel cell powered mobile phones and laptops are being exhibited at the World Expo 2005 in Japan.
Fuels for fuel cells
Hydrogen to run the fuel cell can be stored as a compressed gas, as a liquid or in a chemically-combined form, such as a metal hydride. It can also be produced by reforming a hydrocarbon such as gasoline, methanol or natural gas. For transport, fuel processors are being developed to allow fuel cell cars to refuel with a liquid fuel at a conventional filling station.
Barriers to fuel cells
Today the biggest obstacle to fuel cell commercialisation is cost. Research is being focused on improving cell performance and developing low cost materials which will enable fuel cells to compete on price first against batteries and later against conventional engines and generating plant.