California Institute for Energy and Environment (CIEE)

In this exploratory investigation, UC Berkeley researchers examined battery, hydrogen, and other advanced energy storage technologies that can potentially help to enhance the operation of renewable wind power and other intermittent renewable energy systems. The researchers identified four sites in California that are likely to experience significant growth in renewable wind power generation under the statewide renewable portfolio standard (RPS) and performed economic and environmental analyses of energy storage in the context of those sites for both 2010 and 2020 timeframes. To perform the analysis, researchers used the Hybrid Optimization Model for Electric Renewables (HOMER) developed by the National Renewable Energy Laboratory (NREL). The model was modified to include hour-by-hour characterizations of the four California wind sites and near and long-term technical and economic performance of lead acid battery, and zinc-bromine flow battery energy storage systems and hydrogen electrolyzer, fuel cell, and storage systems. Key project findings include the following: 1) energy storage systems are not highly utilized in most cases examined but are estimated to become more heavily utilized by 2020; 2) with projected cost decreases by 2020, electrolyzer/fuel cell systems become more economically attractive than the competing battery storage systems, particularly at the Southern California wind sites where high levels of wind penetration make them reasonably well-utilized; 3) use of hydrogen produced from wind power to refuel hydrogen-powered vehicles is more economically attractive than re-using the hydrogen in fuel cell systems to produce electricity (at assumed hydrogen prices of $5.00 per kilogram in 2010 and $2.50 per kilogram in 2020); 4) based on an initial qualitative assessment, the various advanced energy storage systems examined are found to be relatively environmentally benign, with the exception of pollution from the production of some conventional and advanced battery materials; and 5) the overall value proposition for energy storage systems used in conjunction with intermittent renewable energy systems depends on multiple factors including the interaction of generation and storage system characteristics and grid and energy resource conditions at a particular location, the potential use of energy storage for multiple purposes in addition to improving the dependability of intermittent renewables (e.g. peak/off-peak power price arbitrage, helping to optimize the transmission and distribution infrastructure, and helping to mitigate power quality issues), the degree of future progress in improving forecasting techniques for intermittent renewable energy systems, and electricity market design and rules for compensating renewable energy systems for their output.