February 27, 2008, was a bad day for renewable energy. A cold front moved through West Texas, and the winds died in the evening just as electricity demand was peaking. Generation from wind power in the region rapidly plummeted from 1.7 gigawatts to only 300 megawatts (1 megawatt is enough to power about 250 average-size houses). The sudden loss of electricity supply forced grid operators to cut power to some offices and factories for several hours to prevent statewide blackouts.
By the next day everything was back to normal, but the Texas event highlights a huge, rarely discussed challenge to the adoption of wind and solar power on a large scale. Unlike fossil fuel plants, wind turbines and photovoltaic cells cannot be switched on and off at will: The wind blows when it blows and the sun shines when it shines, regardless of demand. Even though Texas relies on wind for just over 3 percent of its electricity, that is enough to inject uncertainty into the state’s power supplies. The problem is sure to grow more acute as states and utilities press for the expanded use of zero-carbon energy. Wind is the fastest-growing power source in the United States, solar is small but also building rapidly, and California is gearing up to source 20 percent of its power from renewables by 2017.
Experts reckon that when wind power provides a significant portion of the electricity supply (with “significant” defined as about 10 percent of grid capacity), some form of energy storage will be essential to keeping the grid stable. “Without storage, renewables will find it hard to make it big,” says Imre Gyuk, manager of energy systems research at the U.S. Department of Energy.
Fortunately, there is a promising solution on the horizon: an obscure piece of technology known as the vanadium redox flow battery. This unusual battery was invented more than 20 years ago by Maria Skyllas-Kazacos, a tenacious professor of electrochemistry at the University of New South Wales in Sydney, Australia. The vanadium battery has a marvelous advantage over lithium-ion and most other types of batteries. It can absorb and release huge amounts of electricity at the drop of a hat and do so over and over, making it ideal for smoothing out the flow from wind turbines and solar cells.
Skyllas-Kazacos’s invention, in short, could be the thing that saves renewable energy’s bacon.
