Microtech2010 2010

Repurposing of PEV Batteries for Storage Applications

S. DasGupta
Electrovaya, CA

Keywords: energy storage, PEV, lithium ion, battery, modules


Case Study – Repurposing of PEV Batteries for Storage Applications Electricity Storage Electricity storage is becoming increasingly recognized as a technology that will emerge as an essential component of the future electrical energy grid. Efficient electricity storage will play a key role in helping to manage the fluctuations and intermittency issues of renewable energy sources such as wind and solar power, and will thus enable the integration of substantially more renewable energy into the electrical grid. Additionally, storage will allowexcess renewable energy generated at times of low demand to be held, and effectively shifted to times when it can best be used. At the same time, storage systems have the potential to offer many other benefits – various studies have identified numerous ‘value propositions’ from the implementation of storage, including benefits that can accrue to renewable power producers, grid system operators and utilities, electricity customers and society in general. Electrovaya has recently entered into the Electricity Storage market in Japan where it will develop and sell integrated advanced battery storage systems for both stationary power and smart grid applications for Nippon Kouatsu Electric Co. Ltd. (NKE). Repurposing of Automotive Batteries An important recent development in electricity storage is the rapidly growing interest in PEVs. Electric utilities have a keen interest in this development because of the obvious links to, and potential impacts on, the electricity grid. Consideration is still being given to the “vehicle-to-grid” (V2G) concept of using PEV batteries to supply electricity to the grid at times of peak demand. However, perhaps a more compelling business approach for utilities, battery manufactures and vehicle integrators is to avoid the complexities of discharging expensive mobile storage to the grid, but rather extend PEV battery life by “repurposing”, ie once battery performance degrades to below the demanding requirements for powering vehicles, convert these into stationary battery power units that can be used in grid energy storage applications that require less stringent performance levels. Automotive defines end of life at 80% of the original capacity (USABC 2009) so the batteries will need to be recycled at this point anyway unless they can be repurposed. By creating a secondary market for PEV batteries, this concept of repurposing can effectively reduce the cost of both PEVs and grid electricity storage. Demonstration of a Repurposed Battery System for Electric Bus Recharging: Electrovaya has recently received funding to develop electricity storage systems. Electrovaya will assemble a battery module, populated with repurposed lithium ion batteries obtained from electric vehicle demonstrations. Initially, the module will contain ~150 kWh of repurposed batteries, with space for additional batteries as they become available. This storage module will be integrated into a grid connectable system, where a DC-to-DC link and appropriate controllers will be added to achieve and maintain the required grid voltage by monitoring and adjusting for battery performance variation due to degradation. The repurposed battery storage system will be incorporated into a high power electric bus charger, where it will be grid connected and used to offset electrical loads occurring when charging an electric bus. Testing will closely examine the impact of charging/discharging cycles on the repurposed battery system, and will provide a clearer understanding of how well repurposed batteries will perform over time
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