As we move to higher levels of renewable generation, electric generation becomes much less controllable. We need to find new ways to provide control, and energy storage plays a part in many electricity systems to help with matching supply to demand. Large-scale energy storage has a potential role in helping to integrate higher levels of renewable energy.
Wherever there are mountains, there is an opportunity to store energy by pumping water. That’s pumped storage hydroelectricity. As naturally endowed as Texas is, the state is relatively flat and dry. We don’t have the option to store energy via pumped storage hydroelectricity.
In a recent blogpost for Scientific American, UT PhD student Robert Fares outlines alternative storage scenarios to help smooth fluctuations in supply and demand. Fares gives a good run-down of the emerging alternatives, including compressed air energy storage, flywheels, and batteries. While technological development and manufacturing economies may one day bring the prices of the emerging technologies down, storage costs are not yet competitive, in most cases.
One area where storage may be relatively cheap is in end-use. Unlike large-scale storage, where the electricity is converted from and to electricity using a purpose-built device, end-use storage typically makes use of natural capacity to flexibly vary the timing of the use of electricity. For example, water heating, air-conditioning, and electric vehicle charging are all end-uses where the exact timing of consumption is flexible, due to the storage capacity of the water, the building, and the electric vehicle battery. Such end-use flexibility is an alternative approach to storage and is likely to be considerably cheaper than compressed air, flywheels, and batteries, at least in the foreseeable future.
At the Center for Electric Vehicles (www.ev-tec.org) we are collaborating with the Electric Reliability Council of Texas (ERCOT) on a testbed for electric vehicle charging. One of our key goals is to control charge rates to help with matching overall supply and demand, anticipating the challenges that will come with high levels of renewable generation. Because wind blows strongest in Texas at night, controlled night-time charging has the greatest potential to help with renewable integration. At the end of the day, we want to make it easy for owners of cars to get their car charged overnight–and contribute to integrating wind into the electricity system.