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
Electric load (GWh)
Today, fuel storage and dispatch accomodates
variability and unpredictability in electric load
Day 1
Day 3
Day 5
Day 7
GWh
99.9% renewables on Mid-Atlantic grid
Day 1
Day 3
Day 5
Day 7
Budischaka, et al, 2013. J. Power Sources.
GWh
A hard week of all-renewables
Day 1
Day 3
Day 5
Day 7
Budischaka, et al, 2013. 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
1. 190 million. US US Bureau of Transportation, 2013.
2. Shoup, 2005. “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 rate
Miles added per hour*
J1772 “level 1”
4 kW
16
J1772 “Full spec”
19 kW
76
IEC 62196 (3 ph)
44-52 kW†
180
CHAdeMO (DC)
50 kW
200
*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).
One Hour
Two hours of response by balancing reserves in PJM on June 5, 2013
V2G in operations
• With this fast balancing
service, battery stateof-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 2012.
• BMW finalized donation of a fleet of purposebuilt all-electric MINI E’s in early 2012.
• 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
• alevitt@udel.edu