Oxygen may be necessary for life, but it sure gets in the way of making hydrogen fuel cheaply and abundantly from a family of enzymes present in many microorganisms. Blocking oxygen's path to an enzyme's production machinery could lead to a renewable energy source that would generate only water as its waste product.
Water fuel systems are different from electrochemical cell batteries in that they consume reactant, which must be refurbished, whereas batteries store electrical energy chemically in a closed system. Additionally, while the electrodes inside a battery react and change as a battery is charged or discharged, a fuel cell's electrodes are catalytic and reliably stable.
Hydrogen fuel cells cost more: Hydrogen fuel cells in vehicles are about twice as efficient as internal-combustion engines; however, hydrogen fuel cell costs are approximately 100 times as much per unit of power produced. Hydrogen is a fuel carrier, and should not be viewed as a source of energy.
When used in a fuel cell, hydrogen produces electricity without any harmful emissions; its byproduct is a small amount of water vapor. This is in sharp contrast to today's conventional vehicles which fueled by petroleum and powered by internal combustion engines contribute significantly to the greenhouse gases and other noxious substances being emitted into the atmosphere daily. As such, hydrogen is an ideal renewable energy source, answering today's complex energy problems with its ability to power cars, trucks, homes and business with no pollution or greenhouse gases.
The hydrogen atoms are separated from the oxygen atoms through a process called "electrolysis" and then compressed into fuel tanks. When the hydrogen atoms are temporarily burned as fuel, they recombine with oxygen atoms and turn back into water. Electricity can make hydrogen, and hydrogen can also make electricity. Hydrogen fuel cells are actually hydrogen batteries that generate electricity.
Hydrogen flows into the anode, where in the presence of the catalyst, the hydrogen molecules dissociate into electrons and protons. The hydrogen protons are able to pass through the membrane into the cathode. The electrons flow through an external circuit which produces electricity to power the vehicle. The electrons rejoin the protons in the cathode, and combine with oxygen to form water and heat.
Fuel cells provide high quality DC power, perfect for modern electrical applications such as sensitive electronics or hospital equipment. National electrical grids typically suffer from power fluctuations, black outs and brown outs (where the electricity does not fail completely, but does fall below critical parameters), which can be avoided or mitigated by using a fuel cells-powered distributed generation energy network.
An alternative is taking electricity from a nonpolluting source like solar, wind, or hydro power and using it to split water into its hydrogen and oxygen components.
The problem here is that it takes more electricity to make the hydrogen than the hydrogen can generate in a fuel cell. Even if hydrogen fuel is relatively expensive, it could be the best alternative for making pollution-free vehicles.