Re: Repurposing of LEAF batteries in stationary applications
Posted: Wed Jun 24, 2015 7:09 pm
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Identifying and Overcoming Critical Barriers to Widespread Second Use of PEV Batteries
J. Neubauer, K. Smith, E. Wood, and A. Pesaran
Market penetration of plug-in electric vehicles (PEVs), which could significantly decrease the nation’s dependence on foreign oil and emissions of greenhouse gases, is presently restricted by the high cost of batteries. Deployment of grid-connected energy storage systems, which could increase the reliability, efficiency, and cleanliness of the grid, is similarly inhibited by the cost of batteries. Battery second use (B2U) strategies—in which a single battery first serves an automotive application, then once deemed appropriate is redeployed into a secondary market—could help address both issues. By extracting additional services and revenue from the battery in a post-vehicle application, the total lifetime value of the battery is increased, and the cost of the battery can be reduced to both the primary and secondary users.
Recognizing this potential, the U.S. Department of Energy’s (DOE’s) Vehicle Technologies Office has funded the National Renewable Energy Laboratory (NREL) to investigate the feasibility of and major barriers to the second use of modern lithium-ion PEV batteries. The resultant research identified and answered three high-level questions critical to understanding the viability of B2U:
1. When will used automotive batteries become available, and how healthy will they be?
A detailed analysis was conducted of battery degradation in automotive service, of the economics of battery replacement in automotive service, and of battery degradation in a second use. It was found that there is little to no economic incentive to replace a PEV battery prior to the end of the original vehicle’s service life (approximately 15 years), at which point the battery will have approximately 70% of its initial capacity remaining. The subsequent second use service life is highly sensitive to the second life duty cycle, climate, battery thermal management, and other factors, but could potentially exceed 10 years under favorable conditions.
2. What is required to repurpose used automotive batteries, and how much will it cost?
Application of a battery repurposer business model found that repurposing facilities can likely be dedicated to batteries from a single model of PEV, avoiding the complexities of repurposing heterogeneous batteries, and efficiently operate on a regional scale, avoiding the added costs of nationwide battery collection. Technician labor is a major cost element of repurposing operations that must be minimized. As such, it is economically impractical to replace faulty cells within modules, and thus minimizing purchases of modules containing faulty cells is critical. Use of vehicle diagnostics data to support used battery purchases is therefore of great value to repurposers. When such data is available, repurposing costs can be as low as $20/kWh-nameplate.
3. How will repurposed automotive batteries be used, how long will they last, and what is their value?
Both economic (cost of repurposed batteries, value of service provided) and market size (supply of repurposed batteries, demand for service) factors were addressed to identify suitable applications. It was found that the potential supply of second use batteries can overwhelm the depth of many markets for second use batteries (often by an order of magnitude or more). The most promising application identified for second use batteries is to replace grid-connected combustion turbine peaker plants and provide peak-shaving services. In comparison to automotive service, use in this application will entail relatively benign duty cycles, generally much less than one cycle per day with discharge durations of greater than one hour. Under these conditions, it is anticipated that second use battery lifetimes will be on the order of 10 years. While the value to the original automotive battery owner is restricted primarily to the elimination of end of service costs (battery extraction, disposal, recycling, etc.), the value to the broader community could be significant: decreased cost of peaker plant operation on the order of 10% to 20%, reduction of greenhouse gas emissions and fossil fuel consumption, and deferral of battery recycling...