BMW and PG&E's smart charging pilot shows that demand management can really flatten out the load curve.
Treehugger has previously written about how Tesla kills the duck with big batteries, describing the “duck curve” where solar panels produce more power than is needed during the day, and standby power is needed in the evening when demand is high and the sun goes down. In California in particular, this creates a situation where there is way more electricity being produced by renewables than can actually be used during the day; but there is still a requirement for peaker power plants to generate power needed at the peak evening times when people come home and crank up the air conditioning.
Some have worried that electric cars might make the problem worse because of the additional demand. As John Higham describes it on Inside EVs,
One criticism about Electric Vehicles is that they will cause grid-instability. All those electric cars plugging in at once on an antiquated grid! Pandemonium will ensue, dogs and cats will be living together and civilization will plunge into darkness.
In fact, the opposite is true. Higham, who drives a BMW I3 electric car, was part of a study (big PDF here) that showed how electric vehicles could actually stabilize the grid. Basically, it was a partnership between BMW and the utility PG&E which gave the power company control over when the car was charged. This is a “Demand Response” program similar to those that control water heaters or air conditioning when loads are really high, to shave off the peaks. According to PG&E:
About 100 BMW i3 drivers located in the San Francisco Bay Area participated in the pilot and earned an incentive by offering flexibility in charging their EV. Participants could choose to opt-out of participating in events based on their charging and personal needs. BMW supplemented the smart charging of these vehicles with a solar-powered energy storage system made from “second life” EV batteries — lithium-ion batteries from old BMW MINI E demonstration EVs — as a back-up to support the grid during these demand response events as necessary.
As this graph shows, that last bit of capacity for peak demand is “expensive, inefficient and environmentally unfriendly.” The study had a “demand response event” target of delivering 100kW back to the grid. But by charging the cars at off-peak times, peak demand was reduced, and combined with the BMW batteries, the targets were met. According to Higham, “PG&E is giddy at the prospect of broadening the program.”
There were significant worries that people would opt out of the program because they needed to charge their cars at peak times. In fact, this was part of the study, where participants had an app that would let them opt out. Almost nobody did.
Phase One of the program only controlled charging at the owner’s home, but Phase 2, which expands to 250 cars, also will include charging at work. Higham writes:
…it was made clear that PG&E wanted to incentivize participants to charge during daytime hours. One glance at the Duck Curve and it is easy to see why. Any utility is hugely incentivized to get EVs to charge during periods of large solar production and to stop charging as that production begins to wane for the day. Phase 2 is designed to learn the behaviors of drivers while they are charging away from home, perhaps with the hope of discovering how to incentive drivers to charge during the day.
The implications of this are significant; imagine if all electric cars were part of a program like this, charging up in the middle of the day when the sun is shining and soaking up all that extra capacity. That will reduce demand on the electrical grid that might occur if they just plugged in when they got home.
Combine that with the big batteries that Tesla and others are installing to shave the peak time, and you have really taken a whack at the duck. And further down the road, imagine that all those cars parked for the evening actually put power back into the grid, with what’s known as Vehicle to Grid or V2G. Then the electric cars are not part of the problem, they are part of the solution; the demand curve can be flattened out, and the duck is well and truly cooked.