What are fuel cells?

Fuel cells are electrochemical devices that convert a fuel, most commonly hydrogen, into electricity and heat. It is similar to a battery in that it contains a cathode, anode and electrolyte that releases hydrogen ions and electrons when an external electrical circuit to be attached between the anode and cathode.

The fundamental difference is that a battery has to be either recharged (reversing the reaction) or replaced. A fuel cell has a continuous supply of fuel that replenishes the source of hydrogen ions. It chemically combines hydrogen and oxygen to produce water, electricity and heat without combustion or pollution.

A fuel cell system may include a fuel reformer to generate hydrogen from any hydrocarbon fuel. However, high temperature fuel cells do not even need a fuel reformer and can use fuels such as natural gas, coal gas and methanol that have been generated from fossil fuels, waste streams or biological sources. Since the fuel cell uses electrochemistry rather than combustion, emissions are much lower than from the cleanest combustion processes.

What are the current developments in the fuel cell technology? The cost of fuel cells is currently too high to put them general use, but some commercial applications are beginning to appear. It is an emerging technology with a potential in a range of industry, transport and household applications. A non-pollutant power generator could be the engine of a future passenger car or as an energy storage and electricity production station.

Hydrogen is the most favoured energy carrier for fuel cell systems. It is a very plentiful element, but to achieve the ambitious goal of the hydrogen economy often mentioned by politicians, technologies for safe and cost-effective production, distribution and storage of hydrogen still need to be developed. However, once the hydrogen is available the only by-product of the operating cell is water.

The US and Japan currently lead the world in developing the technology, but the EU has recently mobilised substantial resources to catch up. The diagram below shows a simple schematic diagram of a proton exchange membrane (PEM) fuel cell. This type of cell is most favoured for automotive applications.