Plug in electric vehicles and the grid

The US Department of Defense (DoD) plans to install large numbers of plug in electric vehicles on defense installations in the US. To help reach lifetime economic parity with conventional combustion engines, the parked vehicles will be used in vehicle to grid mode for frequency regulation and peak shaving. After termination of vehicle leases, these batteries will be used for second life stationary grid service and energy security operations. One challenge of providing such services is to control the battery operations to achieve revenue and savings without excessive wear on the battery, which would incur high replacement costs. An analysis by MIT Lincoln Laboratory (MITLL) of charging infrastructure and V2G services shows this to be economically feasible in many locations. Software is described to implement peak shaving, including automated adaptation to new installations, and allowing frequency regulation when not shaving, and achieve this desired tradeoff. Frequency regulation is shown to be benign for most batteries due to shallow depth of discharge, when properly limited by inverter ratings and battery thermal characteristics. This software and its related communications equipment have been tested by operation of a modified electric van for peak shaving services at MITLL, and by use of plug in medium duty trucks in the DoD Smart Power Infrastructure Demonstration for Energy Reliability and Security (SPIDERS) microgrid experiment at Ft. Carson, CO. Operations at 16 other installations have been simulated using real site load data. Battery usage characteristics are established for both peak shaving and frequency regulation services, and combined with driving usage over a repeated US06 cycle. The effect of these on battery capacity fade are calculated using a lithium ion battery aging model to assess all life cycle costs and value. The results of simulations and testing are presented, and support the feasibility of the concept.