Environmental and policy analysis of renewable energy enabling technologies.

摘要

For intermittent electricity generation sources such as wind and solar energy to meet a large fraction (>20%) of the nation's electricity supply, two enabling technologies, energy storage and long distance transmission, will need to be deployed on a large scale. A life-cycle study was performed to evaluate the environmental performance of energy storage and transmission technologies in terms of compatibility with the goals of deploying renewable energy systems. Metrics were developed to evaluate net efficiency, fossil fuel use, and greenhouse gas emissions that result from the use of enabling technologies with conventional and renewable energy sources.; Storage technologies evaluated in this study include pumped hydro storage, compressed air energy storage, and battery energy storage. Three combinations of renewable energy generation and storage were evaluated. Wind/CAES is a likely candidate for large scale deployment, and delivers more than 5 times the amount of electrical energy from a unit of fossil fuel than the most efficient combustion system available, with about 20% of GHG emissions. Both wind/PHS and Solar PVBES also demonstrate superior performance to fossil energy systems in terms of energy sustainability and GHG emissions.; Near term deployment of energy storage will likely take advantage of low cost off-peak energy from existing coal plants, which can result in increases in harmful air emissions. The "grandfathering" provisions of the U.S. Clean Air Act allow for increased output from these older plants that produce high levels of emissions. Energy storage provides a loophole that could be used to increase output from these plants, instead of building cleaner alternatives. The unique hybrid-CAES system has lower life-cycle emissions than any other storage technologies when coupled to coal, but effectively produces emissions that far exceed standards for any new source. A new CAES plant in the Midwestern U.S. will effectively produce SO2 at a rate more than 10 times the amount legally allowed from a new power plant. This loophole has been largely overlooked, and should be examined critically if energy storage is to be compared equally to other electricity generation technologies.