17 research outputs found
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Systems and economic analysis of microalgae ponds for conversion of CO{sub 2} to biomass. 4th Quarterly technical progress report
Microalgae cultivation in large open ponds is the only photosynthetic process likely to directly utilize power plant flue gas CO{sub 2} for production of biomass. The algal biomass can be converted into substitutes for fossil fuels, in particular liquid fuels such as biodiesel (vegetable oil methyl or ethyl esters), thus reducing atmospheric CO{sub 2} levels and the potential for global warming. This concept is being investigated, among others, at the National Renewable Energy Laboratory at Golden, Colorado, with support from PETC
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Process analysis and economics of biophotolysis of water. IEA technical report from the IEA Agreement on the Production and Utilization of Hydrogen
This report is a preliminary cost analysis of the biophotolysis of water and was prepared as part of the work of Annex 10 of the IEA Hydrogen agreement. Biophotolysis is the conversion of water and solar energy to hydrogen and oxygen using microalgae. In laboratory experiments at low light intensities, algal photosynthesis and some biophotolysis reactions exhibit highlight conversion efficiencies that could be extrapolated to about 10% solar efficiencies if photosynthesis were to saturate at full sunlight intensities. The most promising approach to achieving the critical goal of high conversion efficiencies at full sunlight intensities, one that appears within the capabilities of modern biotechnology, is to genetically control the pigment content of algal cells such that the photosynthetic apparatus does not capture more photons than it can utilize. A two-stage indirect biophotolysis system was conceptualized and general design parameters extrapolated. The process comprises open ponds for the CO{sub 2}fixation stage, an algal concentration step, a dark adaptation and fermentation stage, and a closed tubular photobioreactor in which hydrogen production would take place. A preliminary cost analysis for a 200 hectare (ha) system, including 140 ha of open algal ponds and 14 ha of photobioreactors was carried out. The cost analysis was based on prior studies for algal mass cultures for fuels production and a conceptual analysis of a hypothetical photochemical processes, as well as the assumption that the photobioreactors would cost about 10/gigajoule (GJ) is projected. Of this, almost half is due to the photobioreactors, one fourth to the open pond system, and the remainder to the H{sub 2} handling and general support systems. It must be cautioned that these are highly preliminary, incomplete, and optimistic estimates. Biophotolysis processes, indirect or direct, clearly require considerable basic and applied R and D before a more detailed evaluation of their potential and plausible economics can be carried out. For example, it is not yet clear which type of algae, green algae, or cyanobacteria, would be preferred in biophotolysis. If lower-cost photobioreactors can be developed, then small-scale (<1 ha) single-stage biophotolysis processes may become economically feasible. A major basic and applied R and D effort will be required to develop such biophotolysis processes