Recently, New England came close to having an electricity supply crises. On December 14 2013 the electric power grid was pushed to its max. Electricity was bid up to nearly $1.00 / kWhr. I wondered whether, in the future, electric vehicles could be utilized to avert this type of situation if they were designed to source power to the grid. This concept is called V2G which stands for Vehicle to Grid.
It appears that it could work quite well with moderate penetration of electric vehicles.
As reported recently in theEnergyCollective, Massachusetts recently “Made the Smart Grid Mandatory“. In light of that I decided to explore the impact a mature V2G infrastructure would have have had on the December 14th event. The calculation is relatively straight forward and allows us to work the problem backwards and see if the result makes sense.
Looking at the ISO New England report, one can readily see that the problems started at about 5:00pm and went through 7:00pm. During this time the price spiked to $810 / MWhr and demand peaked at about 20,200 MW. Things settled back down when the demand dropped to 19,400 MW. If we assume that 19,400 is the floor above which transient marginal reserves were required (EV battery power) then we can integrate the demand over the two hour period to find the total energy needed. The result is 1225 MWhr. The peak power required is 20,200 – 19,400 = 0.8GW.
So our assumptions are as follows:
Energy required = 1225 MWhr
Peak Power = 800 MW
Average EV Backfeed = 2.5 kW Power that they can feed back to the grid
Average EV Energy = 10 kWhr Energy that they are willing to give up with strong price incentive.
Using those assumptions it would require about 122,500 EVs to provide the energy. However to provide the power it would require 320,000 EVs. If the standard became to wire EVs into 240V circuits then we could modify our assumption for the backfeed to 5kW and then the power and energy would be close. A reasonable estimate is 160,000 EVs.
As of 2003 MA had about 3.6 million registered cars. So if 5% of cars in MA were EVs configured to backfeed the grid, V2G could have rendered this a non-incident.
There are a lot of what-ifs and the point of this was not to be a rigorous analysis. Rather it was to be a sanity check, showing that for modest penetration of EVs this is technically doable. If we had come up with more cars required than there are in New England, then we would have been able to cross V2G off of the list. However, using modest assumptions, we see that the technical numbers work.
For perspective, Teslas come with 60kWhr batteries standard and 85 kWhr batteries optional. With EV battery prices expected to continue to plummet and with a seeming conscensus in the blogosphere that 200 miles is the minimum, it seems a pretty safe bet that the sweet spot as EVs mainstream will be batteries in the 50 kWhr – 100 kWhr range. So the calculations above use 10% – 20% of the car’s charge.