A fuel cell is an electrochemical energy conversion device which has the ability to produce direct current electricity by combining both fuel and an oxidant in a chemical reaction to produce a waste by-product, typically an oxide of the fuel.
Every fuel cell has two electrodes, one positive (cathode) and one negative (anode). The reaction that produces the electricity takes place at the electrodes in the presence of an electrolyte, which carries the charged particles from one electrode to another, while the electrons flow through external wires between the electrodes, creating electricity.
Fuel cells can produce electricity continuously as long as the supply of fuel and oxidant are maintained at the necessary flow rates.
Some fuel cells produce as small as a few watts and as large as a few hundred kilowatts and the smaller ones will likely be used in lap tops and cell phones. However, they are still too expensive for use as small generators in the production of electricity for homes and commercial businesses.
We continue to screen various types of fuel cells for potential grid electricity production or for back-up power supply to such devices as our telecommunication repeater stations.
Economics of fuel cells
Using hydrogen as a fuel source has significant expenses associated with it. Therefore, it is uneconomic in Manitoba at this time, especially with other, less expensive sources available.
Production costs for hydrogen are subject to fluctuation, with the costs reflective of the commodities they came from (e.g. crude oil).
Fuel cell sources
Fuel cells are generally categorized by fuel sources such as hydrogen, organic, metal and redox-flow.
When hydrogen is used as the fuel source, chemical energy is converted to electricity (during the process of reverse hydrolysis), leaving only water and heat as by-products. This means polluting emissions are very low at the fuel cell, but may or may not be high where the hydrogen is produced, particularly when manufactured from fossil fuels, which is a common practice.
The hydrogen fuel cells are further divided into low and high temperature categories, with the high temperature fuel cells also capable of directly using organic fuels. Organic fuels are made up of hydrocarbons such as oil or gasoline, alcohols, or biomass.
Other fuels sources include, but are not limited to alcohols, zinc, aluminum, magnesium, ionic solutions, and numerous hydrocarbons. Other oxidants include but are not limited to air, chlorine, and chlorine dioxide.
Types of fuel cells
Several types of fuel cells currently exist:
- proton exchange membrane (PEM)*;
- regenerative (usually a reversible PEM);
- molten carbonate*;
- phosphoric acid*;
- protonic ceramic*;
- solid oxide*;
- direct methanol;
- metal-air (such as zinc);
* These fuel cells are sub-types of a hydrogen fuel cell, classified by the type of electrolyte used between the anode and cathode terminals.
PEM fuel cell
Hydrogen cells, in particular the low temperature proton exchange membrane (PEM), has been the fuel cell type most widely publicized.
Even though the PEM fuel cell offers some advantages such as low pollution and reasonable electrical cell efficiencies, the disadvantages are far more prominent:
- The cost of the PEM versus a conventional internal combustion engine is roughly 100 times higher.
- It will not perform all of the engine's functions, such as running on a primary fuel and rotating wheels, without additional equipment and energy losses.
- A PEM will generally not operate below 3°C and the exhaust water must not be allowed to freeze in the cell or it will be damaged.
- A PEM fuel cell cannot yet operate in a typical Manitoba winter.
- Energy losses from generation, storage and transportation can exceed 50 per cent.