Over the years, many substances have been proposed as "hydrogen carriers,"such as methanol, ethanol, hydrocarbons, or ammonia -- all of which require special storage and distribution. Also, the thermochemical reforming systems require high temperatures and are complicated and bulky. Starch, on the other hand, can be distributed by grocery stores, Zhang points out.
"So it is environmentally friendly, energy efficient, requires no special infrastructure, and is extremely safe. We have killed three birds with one stone,"he said. "We have hydrogen production with a mild reaction and low cost. We have hydrogen storage and transport in the form of starch or syrups. And no special infrastructure is needed."
"The next R&D step will be to increase reaction rates and reduce enzyme costs," Zhang said. "We envision that in the future we will drive vehicles powered by carbohydrate, or energy stored in solid carbohydrate form, with hydrogen production from carbohydrate and water, and electricity production via hydrogen-fuel cells.
"What is more important, the energy conversion efficiency from the sugar-hydrogen-fuel cell system is extremely high -- greater than three times higher than a sugar-ethanol-internal combustion engine,"Zhang said. "It means that if about 30 percent of transportation fuel can be replaced by ethanol from biomass as the DOE proposed, the same amount of biomass will be sufficient to provide 100 percent of vehicle transportation fuel through this technology."
In addition, the use of carbohydrates from biomass as transportation fuels will produce zero net carbon dioxide emissions and bring benefits to national energy security and the economy, Zhang said.
Thursday, May 24, 2007
Another Hydrogen Possibility
In this one the real fuel is starch. Add the appropriate enzymes and you have a hydrogen-producing reaction. By-products are water and CO2.