Last, week, I had a noteworthy exchange with an engineer from a European carmaker who works on electric cars. Without naming him or revealing what he does, I'll just refer to him as my friend. I'm happy to report his thoughts about vehicle-to-grid technologies (V2G), because the matter is not sensitive and pretty straight-forward: His company has no plans to offer V2G anytime.
My friend told me that he doesn't like the idea because cars are made for driving—not as energy-storage devices designed to give electricity back to the grid. Of course, the idea makes no sense with gas cars. It happens that a gas station runs out of fuel, but nobody has ever brought some gas back to the station to help the other drivers. Actually, it's quite the opposite that happens when there's rumor of a shortage. You see people rushing to gas stations to grab as much as they can. A V2G scheme is in the remote realm of feasibility, but it would bring so many technological changes that may also induce legal changes.
The big issue with V2G is that car manufacturers can't precisely size its effects. Everything's built to a specification in a car. Parts should last a given mileage or a given time, then everything starts to fall apart. An engineer can predict the state of decay of an electric car battery after five years or 75,000 miles, but what if the car has also been used in a V2G application? There's no clear answer, nor a single answer because a V2G system might only ask for short bursts of power once in a while, or it may be used daily to soften the peak that happens in the afternoon—making it difficult for car manufacturers to estimate how much "wear" V2G will add to the battery. Car buyers who chose the V2G option would probably see their battery's warranty reduced—maybe down to six years instead of eight. More than that, the marketplace would learn that cars using V2G will have a battery with more utilization and wear than you would think based on mileage. This would mean a lower resale value. Maybe this would be offset by money coming from the electricity company which bought the electricity from the car. The V2G option shall also require a significant premium when buying the car, but my friend would speculate on the amount. He has never worked on that.
As you can imagine, after this 10 minute chat, my early enthusiasm for V2G started to fade. But not totally, because V2G could still be made to work safely and advantageously—given some strong restrictions. The idea is not to stress the battery in any way. The power allowed for a V2G application would have to be very limited. Imagine that maximum power available could be as low as 5 kW, and the battery would not be drained below 75% SOC. Of course, those numbers are highly hypothetical, since they would have to match the bi-directional home charger, which at this time only exists at the experimental level. The only sure thing is that it will be a long time before cars become parts of a smart grid network.
Or maybe one of you have ideas to make car companies more confident about vehicle-to-grid technology? My friend would like to hear them.
I think V2G will eventually happen in the longer term, as the number of cars increase and people will demand the choice of having the V2G option. In the shorter term, V2H (vehicle to home) makes a lot of sense having the vehicle available as a back-up power provider in case of prolonged power outages. V2H can also be utilized during peak periods when prices are higher with TOU rates.