A fuel cell is an electrochemical device that produces electricity without combustion by combining hydrogen and oxygen to produce water and heat.

What Are the Different Types of Fuel Cells and How Do They Work?

A fuel cell chemically combines hydrogen and oxygen to produce water, heat, and electricity. There are many different types of fuel cells each with their own specific operating principles. A few of the different types of fuel cells include:
1) Alkaline fuel cells (AFC);
2) Direct methanol fuel cells (DMFC);
3) Phosphoric acid fuel cells (PAFC);
4) Proton/polymer exchange membrane fuel cells (PEMFC);
5) Molten carbonate fuel cells (MCFC); and
6) Solid oxide fuel cells (SOFC).

For more information on the specific operating principles of these fuel cells, please visit any of the following Fuel Cells Canada member companies' Web sites:

Direct Methanol:
www.methanex.com

Proton/Polymer Exchange Membrane:
www.ballard.com
www.hpower.com
www.hydrogenics.com
www.palcan.com

Solid Oxide:
www.fuelcelltechnologies.ca
www.globalte.com

What is the History of Fuel Cells?

The Fuel Cell was first developed by William Grove, a Welsh judge with intense scientific curiosity. In 1839 Grove was experimenting with electrolysis (the process by which water is split into hydrogen and oxygen by an electric current), when he observed that combining the same elements could also produce an electric current. Other scientists paid sporadic attention to fuel cells throughout the 19th century. From the 1930s through 1950s Francis Thomas Bacon, a British scientist, worked on developing alkali fuel cells. He demonstrated a working stack in 1958. This technology was licensed to Pratt and Whitney where it was utilized for the Apollo spacecraft fuel cells.

In Canada, early research into the development of fuel cells was carried out at the University of Toronto, the Defense Research Establishment in Ottawa, and at the National Research Council - also in Ottawa. Most of this early work concentrated on alkaline and phosphoric acid fuel cells. In 1983, Ballard Research began development of a Polymer Electrolyte Membrane fuel cell under a contract with the Defense Research Establishment in Ottawa. Over the past twenty years Canadian companies, with some government support, have developed a world-leading position in the development and commercialization of fuel cells and related products.

What is the difference between a fuel cell and a battery?

Fuel cells and batteries are both electrochemical devices that produce electricity, however the fundamental distinction between them is that batteries store "fuel" (the chemicals that react to produce electricity) internally, whereas fuel cells use external fuel storage. The implication of this difference is that when a battery's "fuel" is spent, the battery must either be disposed or recharged whereas with a fuel cell, one can simply refill its storage tank and go, without having to replace the entire cell or wait for it to "recharge" (i.e. restore the chemicals to their original state).

What are the possible uses of fuel cells?

he possible uses for fuel cells are boundless. A fuel cell is simply a device that takes a fuel and, in combining it with oxygen (air), produces electricity. Therefore it can be used in virtually any application requiring electrical power. Fuel cells can be used instead of internal combustion engines or batteries to power vehicles ranging in size from small mopeds to large transit buses and transport vehicles, or in small consumer devices such as laptops and wireless phones. Large fuel cells can replace existing power plants to provide electricity for a large number of users, or in smaller, distributed power generation plants to supply the electrical needs of a factory, a neighbourhood, or an individual home. Basically, a fuel cell can supply clean (low or no emissions), quiet, vibration-free electricity without the need to frequently dispose of the cell when its fuel is spent or wait long periods of time for recharging.

What fuels can be used in a fuel cell?

operates on the simple reaction of hydrogen (H2) and oxygen (O2) to produce water (H2O). The oxygen may be taken directly from air, while the hydrogen may be delivered either in pure form, from liquid or gaseous storage tanks, or extracted from hydrocarbon fuels including methanol (CH3OH), gasoline (a mix of various hydrocarbons), natural gas (CH4), propane (C3H8), and others through the use of a reformer. Much research and development is currently focused on developing either standalone or integrated reformers for extracting hydrogen from hydrocarbon fuels or fuel cells that can be powered directly by fuels such as methanol.

Can landfill or biogas be used to power fuel cells?

Yes. Landfill or biogas (among other fuels - see previous question) may potentially be used either directly or indirectly (after undergoing reformation) in fuel cells.

How does a fuel cell generate heat?

In any process, there are inefficiencies and/or losses. In a fuel cell, the useful work is electricity; however, not all of the energy contained in the hydrogen and oxygen can be turned into electricity. Inefficiencies in the fuel cell turn some of the available energy into heat. In a fuel cell, the inefficiencies are associated with four distinct processes:
- Activation Losses;
- Fuel Crossover Losses;
- Ohmic or Resistance Losses;
- Mass Transport Losses

Activation losses are associated with the activity of the fuel cell - i.e. its ability to dissociate hydrogen and drive the chemical reaction at low temperatures. Activation losses are governed by the temperature and pressure of the reactants, the construction of the cell, and the type and amount of catalyst used.

Fuel crossover losses are caused by leakage or diffusion of fuel between the fuel cell anode and cathode. Essentially the fuel is "short-circuiting" its normal reaction path and reacting with oxygen directly at the cathode. As the electrons participating in the reaction have not been forced to travel through an electrical circuit to complete this reaction (and do useful work), the only energy produced is in the form of heat.

Ohmic or resistance losses are the result of the electrical resistance of the cell to current.

Mass transport losses occur when the ability to maintain adequate concentrations of hydrogen and oxygen in the fuel cell is limited by high demand.

All of these losses combine to produce heat in the fuel cell.

How big can a fuel cell be?

Fuel cells can be manufactured as large or small as necessary for the particular power application. Presently, there are micro fuel cells that are the size of a pencil eraser and generate only a few milliwatts of power while there are others large enough to provide the electrical needs of hundreds of homes. Since an individual fuel cell may theoretically produce an open circuit voltage of approximately 1 V, their power output is fully scalable by varying the cross-sectional area of each cell to obtain the desired current and by stacking multiple cells in series to obtain desired voltage.

What are the advantages of using fuel cells?

Fuel cells are clean, highly efficient, scalable power generators that are compatible with a variety of fuel feed stocks and can therefore be used in an assortment of power generation applications. In particular, they offer several advantages over other technologies:

Fuel cells produce electricity without combustion, which means that, unlike internal combustion engines, they generate little (if any) noise, vibration, air pollution, or greenhouse gases and operate at high efficiencies over a wide range of loads.

In small consumer devices and for powering zero emission vehicles, fuel cells, unlike batteries, avoid the need to replace the cell or undergo a lengthy recharging cycle when its fuel is "spent". Additionally, since fuel cells store their fuel in external storage tanks, the maximum operating range of a fuel cell-powered device is limited only by the amount of fuel that can be carried.

In distributed power generation applications, fuel cells reduce the load on the grid and also eliminate (or reduce) the need for overhead or underground transmission lines, which are expensive to install and maintain, and result in power losses/efficiency reductions. Since fuel cells are scalable and can be installed on site, they reduce the need for large power generation plants (and the environmental impacts of such large scale plants).

Are there any safety issues with fuel cells or their fuels?

Fuel cells are equally safe as existing technologies. For a discussion of the safety aspects related to fuels for fuel cells please refer to any of the following web sites:

Canadian Hydrogen Association: www.h2.ca

International Association for Hydrogen Energy: www.iahe.org

Natural Resources Canada: www.nrcan.ca

When will fuel cell-powered products be available?

Fuel cells will be available in commercial quantities in the very near future. While several companies do currently sell fuel cell power generation units, they are primarily used in pre-commercial field trial and demonstration installations.

From Fuel Cells Canada's "Fuel Cell Technology: FAQ" at www.fuelcellscanada.ca ET