Tuesday, December 23, 2008

Solar Gasification of Biomass and Coal and more

The largest problem with large scale use of solar energy is the intermittent nature of solar, with a capacity factor of only 0.2 to 0.25. When large scale baseload energy is needed, solar doesn't fit the bill. Biomass is one form of long-term solar storage. And what more economical way to release the solar energy from biomass, than -- SOLAR gasification?
One of the drawbacks of biomass gasification systems is that the energy to power these reactors is typically drawn from coal-fired power plants. To produce a truly carbon-neutral, or even better, a carbon-negative fuel, the electricity to turn waste biomass feedstocks into a syngas, which can be further processed into fuels, must come from a renewable energy source.

To that end, a team of scientists including engineers and horticulturists from the University of Colorado in Boulder, Colorado State University in Fort Collins and the National Renewable Energy Laboratory in Golden, Colo., have embarked on a project to develop rapid solar-thermal reactor systems for the conversion of biomass to syngas. _BiomassMag
Coal is another form of stored solar energy which might be more cleanly released using solar gasification.
The steam-gasification of coal (peat, lignite, bituminous, and anthracite) into syngas is investigated using concentrated solar energy as the source of high-temperature process heat. The advantages of the solar-driven process are threefold: (1) the discharge of pollutants is avoided; (2) the gaseous products are not contaminated by combustion byproducts; and (3) the calorific value of the fuel is upgraded. _Source
Coal gasification of low quality coal is far superior to simple combustion, in terms of the sequestration of pollutants. Using solar energy to perform the gasification should be more economical, once the processes are worked out and scaled.

Australian researchers have devised an ammonia to hydrogen / nitrogen reversible process powered by solar, as a means of storing solar energy and releasing it on demand (see illustration at top).
The basic idea is that ammonia is pumped into the focus of a large solar collector where temperatures reach several hundreds of degrees. At these temperature the ammonia dissociates into hydrogen and nitrogen. _ANU Sciencewise
The article at the link above explains how the process works. Following the illustration at the top of the post will provide a thumbnail understanding of the reversible process of solar energy storage and use.

Another way that solar energy can be used to facilitate biomass energy is by using solar powered robotic machinery on the farms and in the forests, to collect, densify, and pre-process the biomass for transportation and further processing. Much of this robotic equipment will eventually be largely autonomous, operating during daylight hours to provide a nearly steady stream of biomass feedstock for conversion into useful energy.

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