Fuel Cells

Fuel cells are an electrochemical energy conversion device. Fuel cells are similar to batteries except that the chemicals they require can be replenished. In effect, fuel cells do not have a finite life (like batteries) and will continue to produce energy unless the device breaks down or the chemicals required are no longer available.

How Fuel Cells Work

The most promising model of fuel cell technology is called the proton exchange membrane fuel cell (PEMFC) which uses hydrogen and oxygen to produce electrical energy and water. It has four main parts: an anode (a negatively charged material through which hydrogen gas is pumped); a cathode (a positively-charged material through which oxygen gas is pushed); a catalyst (situated between the cathode and anode and facilitates the reaction of oxygen and hydrogen); and the proton exchange member (conducts positively charged ions and blocks negatively charged ions).

Pressurized hydrogen (H2) enters the fuel cell through the anode side and is pushed through the catalyst which forms two positively charged hydrogen ions (H+) and two negatively charged electrons. The anode 'transfers' the electrons through an external circuit (this forms an electrical charge) which then transfers it back to the cathode side, where they interact with negatively-charged oxygen atoms.

The oxygen atoms are formed when oxygen gas (O2) is pushed through the cathode and catalyst, where they are 'split' to form two negatively-charged oxygen atoms. They will attract two positively charged hydrogen ions (H2) and they will combine to form water (H2O).

The reaction in a single fuel cell produces around 0.7 volts of electricity. A combination of PEMFCs (called a fuel-cell stack) combines the output of several PEMFCs to produce useful electricity.

Upsides and Downsides of Fuel Cells

PEMFCs have the advantage of working at low temperatures (about 80 Celsius or 176 Fahrenheit) which means they don't require expensive or large containment structures to operate. Technological advancements have also led to devices as small as a suitcase that can power up a car. Fuel cells are also very sustainable in the long term.

There are still obstacles to overcome, though, before they can become commercially viable. One of these is the problem of the fuel; while oxygen is readily available (and can, in fact, be pumped in from the air), hydrogen is difficult to distribute and store (especially as it is a volatile and flammable gas).

One approach is to use other fuels to produce hydrogen within the cell, using another device called a reformer. Among the fuels being tested are methanol (a liquid fuel similar to gasoline) and propane (currently used for gas-fired stoves among others). Unfortunately, using a reformer to convert these fuels into hydrogen to power the fuel cell is inefficient; the hydrogen is often impure and requires another device to clean it up.

Still the obstacles are, as many scientists point out, a matter of engineering and technology. Fuel cells hold the promise of better energy producing efficiency with minimal pollution - which is one of the goals in developing it.