Vehicle to Grid Electric Vehicles as Grid Storage Andrew Levitt Project Manager for Vehicle-to-Grid project sponsored by NRG Energy and University of Delaware

Transition to Carbon-free Power Those most concerned with climate change envision a world with very limited carbon emissions This would entail a radical increase in use of variable electricity generation from wind and solar

Grid storage

Today, fuel storage and dispatch accomodates variability and unpredictability in electric load Day 1Day 3 Day 5 Day 7 Electric load (GWh)

99.9% renewables on Mid-Atlantic grid Day 1Day 3 Day 5 Day 7 GWh Budischaka, et al, J. Power Sources.

A hard week of all-renewables Day 1Day 3 Day 5 Day 7 GWh Budischaka, et al, J. Power Sources.

Electric energy storage allows avoidance of fuel storage

Electric vehicles

Electric Vehicles. Consider: 1.There are about 200 million light vehicles in the United States. 2.In low-carbon world, most would (debatably) be electric vehicles. 3.An electric vehicle is necessarily a substantial investment in: – Energy storage – 100 kilowatts of two-way power conversion from battery to electricity 4.Cars are unused for about 23 hours per day million. US US Bureau of Transportation, Shoup, “The High Cost of Free Parking”.

If half of US cars were electric: Electric vehicle power capacity – 100 million x 100 kW = 10,000 gigawatts – ~10x the peak capacity of the US grid Electric vehicle storage capacity – 100 million x 40 kWh = 4,000 gigawatt-hours – Enough to run the US grid (at average load of 500GW) for 8 hours Of course cars need to drive…

Maximize Value Bidirectional power flow: enable multiple electric services, and allow continuous participation Use motor drive electronics for charging/ discharging -- negative cost, high power High power (e.g. push to J1772 limit of 19 kW)

User conveinence of high charge rate Charge rateMiles added per hour* J1772 “level 1”4 kW16 J1772 “Full spec”19 kW76 IEC (3 ph)44-52 kW†180 CHAdeMO (DC)50 kW200  *4 mi/kWh. † IEC62196 in EU=44kW, in US=52kW Photo credit: Tim Shaffer, NY Times

Costs of using electric vehicle as grid storage Control electronics on car and charging station (currently ~$400 each) Battery wear Administrative and scheduling time Cost per kilowatt: $27/kW Cost per kilowatt-hour: $13/kWh Compare to purpose-built storage…

Battery wear Depending on chemistry, decrease of battery life may be expected when exercised under certain conditions: – Very high or low state of charge – Very high sustained charge or discharge current – More full-charge cycles Determining what and how much impact V2G has on batteries is a goal of current research.

Vehicles comprise a mostly-idle capital investment in enormous power production and energy storage. It is low cost to harness this resource for grid-connected energy storage.

Grid services

V2G value Grid balancing services (grid operators) Defer distribution investment (utilities) Arbitrage (energy markets) Limit demand charge (commercial consumer) Firming and leveling renewables (wind operator or grid operator) Etc..

Grid has to balance supply and demand at each moment Scheduling of generation and load accomodates almost all of this. Unpredictable, instantaneous inaccuracies are compensated by fast balancing reserves (below). Two hours of response by balancing reserves in PJM on June 5, 2013 One Hour

V2G in operations With this fast balancing service, battery state- of-charge stays between 50% and 75% It does not drain the battery A trip scheduler triggers charging of car to full capacity when needed.

Balancing reserves market 2013 average price of 3.0¢ per kilowatt-hour Corresponding revenue is $320 per month with 18kW charging at home and work, accounting for charge time for driving.

Fast grid balancing provides several hundred dollars in gross revenue per car per month. Fast grid balancing does not drain the battery of an electric car.

V2G Project Photo credit: Tim Shaffer, NY Times

Project Collaborators

History Preliminary V2G system developed by University of Delaware in 2007 and launched with 3 vehicles in 2008 NRG Energy bought a stake in the technology in 2011 Milbank Manufacturing licensed the V2G charging station in early BMW finalized donation of a fleet of purpose- built all-electric MINI E’s in early Also engaging several major japanese carmakers and domestic electric truck manufacturers.

Status First ever payment by a grid to a car was for services on February 27 of this year Operating with a stationary test bed plus 3 fleet cars since February Generating up to $5 per car per day providing balancing reserves Continuing to refine technology for release to small number of test drivers. Still open for fleet participation. UD-developed, V2G-enabled Milbank charging station soon to be commercially released Currently looking to expand to other grid operator territories Photo credit: Tim Shaffer, NY Times

END Andrew Levitt