Vehicle to Grid

learnedbawledElectronics - Devices

Nov 24, 2013 (3 years and 11 months ago)

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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 1





Day 3




Day 5


Day 7

Electric load (GWh)

99.9% renewables on Mid
-
Atlantic grid

Day 1





Day 3




Day 5


Day 7

GWh

Budischaka, et al, 2013. J. Power Sources.

A hard week of all
-
renewables

Day 1





Day 3




Day 5


Day 7

GWh

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).


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 2012.


BMW finalized donation of a fleet of purpose
-
built 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