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In this report, we present a process design for the storage of electricity using solid oxide fuel cell (SOFC) technology to convert electrical energy to chemical fuel via the reduction of carbon dioxide. The goal of this project was to design a system that could alleviate the issues around the intermittent nature of renewable energy production, which must phase out the use of fossil fuels in the future. The overall process was developed for two storage strategies, and the economics feasibility of the design is considered and reported. The key aspect of this process is its reversible nature. Both the production and consumption of the chemical fuel are achieved in the same plant, both with the SOFC technology.
Two cases are presented. In both, carbon monoxide is produced via electrolysis during high-production hours for solar and wind power. Carbon dioxide is renewably sourced from fermentation plants. In the first case, the carbon monoxide is pressurized for storage at 2,000 psig. In the second case, the carbon monoxide is minimally compressed to 5 psig and stored at near atmospheric conditions. It was found that for the high-pressure storage case, the efficiency of the process was 53.5%, and in the low-pressure storage case, the efficiency was 54.6%.
Two pricing strategies were considered. The first assigned an opportunity cost of electricity storage to the off-peak electricity price. In this scenario, the high- and low-pressure cases had negative ROI’s of -32.5% and -29.4%, respectively. In the second pricing strategy, we consider the eventuality of overproduction of solar and wind energy, when renewable energy sources comprise a majority of the supply. In this scenario, the opportunity cost of the excess electricity production would be zero, and the ROI of the high- and low-pressure cases are then positive at 29.9% and 31.8%, respectively. Though the latter is not reflective of the current economic reality, in the future it may become more relevant, and a design such as the one presented here should be considered as a potentially profitable solution.
Date Posted: 11 May 2020