by Jim Kerr
Fuel cells have been proclaimed as the technology that will enable us to drive our cars and power our homes in the future. Even with all the news on fuel cells, very few really know what they are. Here is a little primer to help understand what fuel cell technology is and how we will use it.
Fuel cells are not new. Sir William Grove first demonstrated the technology in 1839. He used a reverse electrolysis to generate electricity. Without a practical application, the discovery went unused until NASA began looking for a power supply for space vehicles in the 1960’s. Research since that time has progressed continuously, but we are still at the beginning of fuel cell development.
Not all fuel cells are the same. The four main types are the polymer electrolyte membrane (PEM), molten carbonate (MCFC), phosphoric acid (PAFC), and solid oxide fuel cell (SOFC). The different fuel cells use a different electrolyte, but each generates electricity through an electrochemical reaction. In simple terms, hydrogen and oxygen are combined to produce electricity. The only by-products are heat and water vapour. PEM fuel cell technology has received the most promotion, but there is no clear winner in fuel cell technology yet.
Hydrogen, the fuel used by fuel cells can be obtained from a wide variety of sources. It can be extracted from coal, natural gas, methanol, and other fossil fuels. It can also be generated from water using electricity. Solar power, wind power, or hydro-electric power could provide a continuously renewable source of hydrogen fuel. Pure hydrogen is the fuel of choice for current fuel cells, although reformulators can be added to the fuel cell package that will use a conventional fuel and break it down into hydrogen as needed. The advantage of using hydrogen directly is that bulk and weight of reformulators are not needed as part of the package.
Oxygen is another requirement for fuel cell operation. Some fuel cell technologies work best with pure oxygen. Another set of pressure tanks must added to the fuel cell package. Some fuel cells work on air, extracting the oxygen as needed; an advantage because oxygen storage tanks are not needed. As for hydrogen, technology is improving and currently General Motors has licensed tank technology that holds hydrogen at 10,000 psi. This is double the 5000 psi maximum just a few months ago. With more hydrogen on board, vehicle range has improved to about the same as gasoline powered vehicles.
Hydrogen has had a bad rap for safety ever since the Hindenberg airship disaster in 1937. It is volatile, but if stored properly it is safer than gasoline. Hydrogen storage tanks in vehicles are capable of stopping a 45 Magnum handgun bullet at close range. The outlets have internal automatic shutoff valves to prevent fuel escaping if external piping is damaged. If hydrogen does manage to escape, it dissipates almost immediately in the air.
Another advantage of hydrogen over other fuels is that it is non-toxic. If released, all that may remain behind is a little water. When gasoline and oil spill, there can be serious environmental damages.
While fuel cell cars are getting the limelight, it may be residential fuel cells that will be in popular use first. Power shortages in many areas of the world could be alleviated with fuel cell generating plants. Small units can be used for individual homes, while larger units are suitable for small businesses. Currently, General Motors is marketing 1000 watt portable generators but the cost is about $5000 US. Prices will drop as mass production and technology improves.
Changing the output capacity of fuel cells is relatively easy. A practical fuel cell is really a stack of plates or cells, similar to stacking flashlight batteries together to get more power. The more cells stacked together, the more power output of the package. Fuel cells operate quietly, and continuously, with zero to low emissions. They are comparable to battery power, but without the environmental hazards found in batteries.
Currently, fuel cell vehicles are sluggish, take a while to warm up before they operate, and are expensive to build. All these shortcomings will be overcome with research, and yes, the future for the fuel cell does look bright.