Hydrogen as Potential Fuel

Hydrogen is the most plentiful element on Earth and is found in combination with oxygen in water, and in organic matter including living plants, petroleum, coal, natural gas and other hydrocarbon compounds. The great attraction of hydrogen is that, once isolated, it is a clean burning fuel that produces neither carbon dioxide (a greenhouse gas) nor toxic emissions and can be used for electricity production, transportation, and other energy needs.

Many see a movement to a hydrogen economy as the long-run solution to the environmental and security problems associated with fossil fuels. However, before hydrogen can be used as fuel it must first be extracted from hydrogen-bearing compounds either through electrolysis or high temperature reformation of organic compounds like coal. Many of the extraction processes can create substantial pollution and so for hydrogen to be truly pollution free the extraction process must be pollution free.

If the problems of extracting hydrogen can be solved in a pollution free, cost effective manner and if technologies such as fuel cells can be made cost effective, then hydrogen has the potential to provide clean, alternative energy for a number of uses, including lighting, heating, cooling, and transportation.

What is Fuel Cell

Practical fuel cells were first developed in the 1960s for the U.S. space program. A fuel cell is a device that converts a chemical fuel (generally pure hydrogen) directly into electricity. A fuel cell is like a battery that never runs down. The chemicals that are consumed (hydrogen & oxygen) are continually fed into the cell, rather than being a component that is used up. Fuel cells may also be thought of as "reverse electrolysers". When two electrodes are put into a salty water solution and a current is passed, water is broken down into hydrogen and oxygen. This process is called electrolysis. Fuel cells perform the reverse action – they combine hydrogen & oxygen to form electricity and water.

Economy

Internal combustion engines are limited by the laws of thermodynamics to a maximum efficiency (the mechanical work output divided by the chemical energy in) of about
30%.Fuel cells are not limited by the thermodynamic Carnot cycle, and can convert fuel to electricity at up to 80% efficiency. This means that you can go three times as far in a fuel cell car as in a gasoline car, on the same amount of fuel. There are two ways of storing the hydrogen needed to run a fuel cell car. Either pure hydrogen can be stored in gas, liquid, or "metal hydride" form, or hydrogen can be generated onboard from hydrocarbon fuels such as compressed natural gas or methanol.
The "reforming" of methanol or other hydrocarbons to produce hydrogen and carbon dioxide has the advantage of easy fuel storage but the disadvantages of needing a small, onboard chemical processing plant, and still polluting the atmosphere with carbon dioxide. Storage of pure hydrogen in cryogenic liquid or high pressure gaseous forms poses safety hazards that are unacceptable for general transportation. Storage in metal hydrides, where hydrogen atoms lodge in the atomic lattice of metals such as magnesium and titanium, offers safety and ease of use, but carries the penalty of high costs and much added weight (only 2-5% of the weight of the storage system is actually hydrogen). When the system is looked at as a whole, however, this extra weight is compensated by the reduced weight of the drive system (the fuel cell, electric motor and motor controller) when compared to a gasoline engine and transmission, and reduced fuel requirements. Fuel cells capable of 10 kW continuous output and electric motors rated at up to 100 HP should be available at weights of less than 50 lbs apiece.

Safety

The safety of hydrogen as a fuel is often questioned. In fact, hydrogen is in many ways far safer than gasoline – it is non-toxic and disperses quickly. So little gaseous hydrogen is available in a hydride storage system (and heat is needed to liberate gas from the metal matrix) that such systems are inherently far safer than gasoline storage in today's cars.
A hydrogen powered car needs a means to refuel. This could take the form of hydrogen refilling stations where hydrogen is piped or trucked from central generating sites. These "gas" stations will be worthy of their name.

Production

Hydrogen is produced in large quantities today from natural gas via a reforming process. This is the cheapest source at present. Hydrogen can also be produced from water and electricity via electrolysis. This could be done actually at the "gas" stations, or alternately, small electrolysers could be installed in cars, or in home garages, to provide a means of refueling from grid electric power. In the short term, home or onboard electrolysers are the only alternative, despite higher fuel costs, as a network of hydrogen gas stations will take some time to evolve.