What new technology will supply the energy required by an increasingly power-hungry industry and the projected world population of 10 billion? What technology can do this in a way that will not increase carbon emissions and global warming? Currently, the most popular answer to both these questions is: fuel cells. Fuel cells will power vehicles and generate power for homes and industry. See Fuel Cell and Hydrogen News for more information on fuel cells. The more difficult question is where will we get the fuel to run the fuel cells?
Fuels cells run on hydrogen. Hydrogen gas (H2) is passed through a catalyst which separates the hydrogen into two electrons and two hydrogen molecules. The positively charged hydrogen molecules are able to pass through a special membrane. The electrons can't so they create an electrical current on their path to the other side of the membrane where they are reunited with the hydrogen molecules and an input of oxygen. Pure water (H20) is the only emission.
Hydrogen is very energy dense - even more so than carbon - so it is an excellent fuel. In fact the energy in fossil fuels (hydrocarbons) is derived from the hydrogen in the fuels in a combustion reaction (as opposed to an electro-chemical reaction in fuel cells). Unfortunately, hydrogen naturally occurs as a very low density gas requiring high pressure, volume, or low temperature to store in a practical manner, especially given the limitations onboard a vehicle. Present methods of producing it also present problems. One method involves a relatively expensive electorlyser which uses electricity to separate hydrogen from water. The other method reforms hydrogen from hydrocarbons such as gasoline or methane. This also requires prohibitively expensive equipment and results in emissions of carbon and other air pollutants.
The problem of how to create an economical supply of hydrogen has not been solved. But recent technical advances make it likely that industry will soon be able to cost-effectively mass produce fuel cells, a lot of attention is being focused on the hydrogen supply problem. How is hydrogen supposed to be produced? How will it be stored and transported? New technology and infrastructure systems must be created, along with ways to economically transition to them from our present distribution systems for vehicle fuel and power.
Researchers are pursuing several potential technical breakthroughs, such as carbon nano-tubes or metal hydrides for storing hydrogen in solid form. Advanced hydrogen reformer technologies are being developed which convert gasoline or methanol into hydrogen. Reformers have the advantage of enabling fuel cell vehicles to utilize the existing distribution and storage infrastructure for vehicles.
Much of the thinking on hydrogen infrastructure is based on the assumption that it must be produced in bulk and delivered through extensive distribution systems similar to those in place for fossil fuels. The enormous sums of money required is obviously a potential obstacle. But another approach has been suggested by
Amory Lovins, director of research at the Rocky Mountain Institute (RMI) in Golden, Colorado. Lovins' hydrogen infrastructure transition scenario involves integrating the fueling systems for fuel cells in buildings and vehicles. SeeA Strategy for the Hydrogen Transition, an RMI position paper.
In the first phase of Lovins' proposed transition, fuel cells would be used in buildings where they are cost-effective now, especially when the thermal energy is utilized and "distributed" benefits (quality, reliability, transmission cost-avoidance, load management) are considered. Hydrogen would be supplied by appliances - either off peak electrolysers or nat gas reformers using the buildings existing electricity or natural gas supplies. Mass production of fuels cells for buildings will lower their cost making them feasible for use in transit, fleet, and specialized vehicles.
This would lead to a second phase where fuel cells are produced in quantities that make them economical for general vehicles. Fuel cell vehicles could also produce electricity while parked in buildings as plug-in 20 kW power plants. This would defray part of their lease cost. This building/vehicle integration eliminates the need for upstream bulk production and distribution infrastructure. It is also cheaper than onboard reforming of fuels and creates 3 TW of production capacity - more than all existing cental thermal power stations.
In a third phase, the cost of hydrogen appliances goes down, and they are installed as freestanding refueling stations. The increasing volume of this decentalized hydrogen production would make bulk production competitive. Two options exist for bulk production:
a) Using hydroelectric dams to generate hydrogen;
b) Wellhead reforming of natural gas with CO2 reinjection.
Wellhead reforming creates three profit streams: 1) hydrogen fuel; 2) enhanced hydrocarbon production?; 3) carbon sequestration credits. Large energy companies are already studying this alternative.
As Mechanical Engineering Magazine points out ". . . the real gestalt shift occurs when you stop looking at the hydrogen infrastructure needed to support fuel-cell vehicles as an isolated issue." See Fueling the Cells. Buildings consume two-thirds of the energy in this country. Lovins' makes a strong argument that if we start by putting fuel cells in buildings, hydrogen-powered cars will follow.