This piece was originally published in the January 2017 issue of electroindustry.
Charles Botsford, PE, Chemical Engineer, AeroVironment
The electric grid has changed, but the change isn’t finished. With state and federal requirements to incorporate more renewable energy—primarily wind and solar—as part of our power generation mix, the grid must also incorporate a massive amount of energy storage to continue to provide stable and low-cost power. Electric vehicle (EV) charging is an excellent contributor to the suite of energy storage we’ll need for connectivity in the future grid.
The U.S. grid provides electricity with exceptional reliability—notwithstanding sporadic power outages—at a relatively modest price. It balances power generation precisely with a multitude of loads, but has almost no reservoir of energy storage. The grid can do this because of load balancing.
Renewable energy sources such as wind and solar are generally unpredictable and can’t be ramped up (dispatched) if the grid’s load changes. If the grid uses traditional power generation to compensate for the fluctuations of renewable energy, the cost advantages of the renewables is lost.
That’s where energy storage comes in. Grid-scale energy storage techniques include pumped hydro, which uses gravitational potential to pump water from a lower elevation to a higher one to cover peak demand; compressed air, which is similar to pumped hydro; and grid-scale batteries that store electricity at off-peak periods to cover peak demand.
The problem with these technologies is that they are expensive, in terms of capital investment and operating costs. They also have an inherent roundtrip energy efficiency loss. If the grid can use EV charging for energy storage, the cost and roundtrip efficiency loss problems go away. The idea is to charge an EV in a conventional manner, but with grid intelligence to compensate for fluctuations and non-dispatchable renewables.
With EVs as a small percentage of all the vehicles on the road today, the potential for them to provide meaningful grid services just isn’t there. But when EVs reach 10 percent, 25 percent, or even 100 percent, the value of EV charging to the grid may overshadow every other type of grid storage.
Most advantageously, since people will buy EVs to drive anyway, the storage cost is almost nothing.