Energy futuresSolving the major problem of renewable energy: intermittency

Published 7 March 2012

Intermittency, sometimes called the Achilles’ heel of renewable energy, has so far limited the penetration of renewable sources in most power grids; engineers imagine an energy future where giant transmission grids are backed up by massive energy storage units

William F. Pickard introduces the February 2012 special issue of the Proceedings of the IEEE by quoting the Bible: “The wind bloweth where it listeth.” This, in so many words, describes the major technological issue with renewable sources of energy, such as solar and wind power.

“Wind turbines or solar collectors alone cannot supply baseload power,” Pickard says. “It’s blowing beautifully outside today, and if you had a wind turbine you’d be in fat city. But at sundown the wind could suddenly drop and there’d be no sunshine to replace it. You would freeze in the dark — unless you had stored up energy.”

Intermittency, sometimes called the Achilles’ heel of renewable energy, has so far limited the penetration of renewable sources in most power grids.

A Washington University in St. Louis release reports that Pickard, Ph.D., senior professor of electrical and systems engineering in the School of Engineering & Applied Science at Washington University in St. Louis and a life fellow of the IEEE, co-edited the special issue, “The Intermittency Challenge: Massive Energy Storage in a Sustainable Future,” with Derek Abbott, Ph.D., professor in the School of Electrical and Electronic Engineering at the University of Adelaide and a fellow of the IEEE.

“Most projections show that late in the 21st century, fossil-fuel shortages are going to bite hard,” Pickard says. “If you’re an optimist, you might say 75 years, and we’re going to be in trouble — real trouble. And once economical sources of fossil fuels approach depletion, we have no certain recourse except to renewables.”

What, then, can be done about the problem of intermittency? The Proceedings of the IEEE, a leading journal in electrical engineering and computer science, delves into the problem, focusing on schemes for rendering renewable energy reliable and dispatchable, particularly massive storage facilities for energy.

Transnational power grids
One of the more ambitious articles in the issue describes a giant power grid, to be called the Pan-Asian Energy Infrastructure, that would encompass China, Japan, South Korean, the ten Association of Southeast Asian Nation (ASEAN) states, and Australia.

Wind energy is abundant in China and Mongolia, and solar energy is abundant in Australia’s interior. Together, the authors say, they “represent Asia’s most plentiful renewable energy resources for which capture technology currently exists.”

With a grid this big, the authors say, averaging effects come into play and uncorrelated intermittencies can partially cancel each other out.

“Northern China’s peak electricity demand occurs in winter because of