Fuel Cells - A brief review

When making a decision to purchase a diesel generator the manner in which the diesel fuel is converted to electricity is seldom considered, it is just accepted that we pour diesel in one end and electricity comes out the other.

However, when describing and considering fuel cells, it is too easy to slip into overly technical and complex jargon, the way in which the cell works distracts from the benefits of selecting the technology.

But ultimately, as with the diesel generator, fuel goes in one end, useful energy comes out the other.

Why consider using fuel cells.

Fuel cells are far more efficient at converting the base fuel to useful energy and should be considered not so much as an electric generator but as a very efficient source of combined heat and power.

A fuel cell is an electrochemical energy converter. When it is fed a fuel and an oxidant it will produce:

• electricity
• heat
• reaction products i.e. waste.

So how is this different from a regular diesel generator?

Rather than igniting the fuel and oxidiser as you would in an internal combustion engine you react them in an electrolyte with positive (anode) and negative (cathode) electrodes suspended in it.

The advantages are immediate in that unlike a traditional generator:

• there are far fewer moving parts in the system, making it more reliable;
• you are taking out the intermediate process of converting kinetic energy into electricity so you have a more efficient system (each conversion process means a loss of efficiency).
• In not running an engine, you avoid the additional wasted energy inherent in making the engine run. (what do you mean by this?)

So the basic action of any non-regenerative fuel cell can be summarised in this diagram:

The difference between the fuel cell and the internal combustion engine you can see here is that a large proportion of the waste from a fuel cell is water.

The waste gases depend upon the fuel and oxidant that you are using but typically contain very low levels of CO2, NOx and SO2. If you are using pure Hydrogen and Oxygen as your fuel you will produce only water as a waste product, if you are using bio-fuels then you will be effectively carbon neutral as the carbon has not been removed from long term storage as it has been for coal or oil.

Environmental benefits of Fuel Cells

A very technical description of fuel cells

The inefficiency of running a diesel engine can be largely summed up as the energy required to:

• Pump the coolant
• Circulate the oil
• Drive the cooling fan
• Lift the valves
• Turn the dynamo
• Spin the flywheel
• Overcome friction