Solar Energy Laboratory

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SUNgas: Thermochemical gasification of biomass using concentrated solar energy


The goal of this project is to develop and advance technology for the sustainable production of synthesis gas via solar thermochemical gasification of cellulosic biomass and carbonaceous waste materials. Coupling concentrated solar energy with thermochemical conversion of non-food biomass and waste products promises a new path for the production of alternative fuels as well as storage and transport of solar energy. The solar production reduces greenhouse gas emissions—even compared to other biofuels—without requiring carbon capture and sequestration. The process stores solar energy as an easily convertible and transportable fuel.

The solar technology has dramatic advantages over conventional gasification processes. The yield of fuel per acre of cropland is doubled, and the product gas is clean—uncontaminated by the byproducts of combustion. On-going work in at the Solar Energy Laboratory addresses the important scientific, technical and economic challenges of solar reactor design and optimization of fuel production across the U.S. A 10-kW solar reactor/receiver and optical system is being designed and will be on-sun in the California desert. The novel reactor uses molten salt for storage and as a catalyst and heat transfer medium. Viable geographic location and scales of deployment in the United States will be identified based on life cycle and economic analyses.

Fig. 1. The ideal operating condition for the process is based on thermodynamics. Carbon conversion occurs rapidly as temperature is increased from 800 to 1200K. At 1200K, the product is a 1:1 molar ratio of H2 and CO, a suitable composition for producing liquid transportation fuels. This temperature can be achieved readily using modern concentrating solar optics.

Fig. 2. The energetic benefit of solar gasification for production of Fischer-Tropsch fuel (following a water-gas shift reaction to obtain a 2:1 H2 to CO ratio) is shown. The annual energy yield possible from a gasification process using prairie grass blend planted on non-arable lands in barrel of oil equivalents (BOE) is 4.9 BOE/acre compared to 2.6 BOE/acre for conventional gasification. SUNgas has a 17% greater energetic value than the grass feedstock due to the solar input.