Renewable Energy Could Supply 99 Percent of U.S., Study Finds

A renewable grid by 2030? | Photo: Michael Kappel/Flickr/Creative Commons License

A combination of solar power, wind, and currently available storage technologies could fill 99.9 percent of a large power grid's needs by 2030, according to a new study out of the University of Delaware and Delaware Technical Community College. The researchers found that a very large power grid could conceivably be run almost entirely on renewable energy, with fossil fuel backup for about a tenth of a percent of the power consumed in total.

"For example, using hydrogen for storage, we can run an electric system that today would meet a need of 72 gigawatts, 99.9 percent of the time, using 17 gigawatts of solar, 68 gigawatts of offshore wind, and 115 gigawatts of inland wind," co-author Cory Budischak, instructor in the Energy Management Department at Delaware Technical Community College, said in a University of Delaware press release.

The study used computer models based on the PJM Interconnection, a regional grid covering 13 northeastern states which delivers a fifth of the United States' power. The authors based their models on projected capital costs per kilowatt-hour of renewable energy sources -- assumed to be about half what they are today -- and built in currently available battery and hydrogen fuel cell technology for their models' storage component. The researchers found that grid operators would be able to provide power reliably and at moderate cost by relying on capacity rather than more-expensive storage to cover peak periods whenever possible.

"These results break the conventional wisdom that renewable energy is too unreliable and expensive," said co-author Willett Kempton, professor in the School of Marine Science and Policy in the University of Delaware's College of Earth, Ocean, and Environment. "The key is to get the right combination of electricity sources and storage -- which we did by an exhaustive search -- and to calculate costs correctly."

For California, a totally renewable system relying on wind on the model of the Delaware study may cause more trouble than it's worth. Wind slackens for entire seasons here, to the point where entire days in December go by with wind power contributions to the California grid hovering around 200 megawatts, or even below (Today, for example, December 11, statewide wind output has only started to climb toward 200 megawatts in mid-afternoon. At 4,287 megawatts in installed wind capacity as of March 2012, 200 megawatts of output is 4 percent of the state's installed capacity. Building out wind turbines to cover the state's peak demands, which range from 35-55 gigawatts, would mean that we'd need almost 900 times as much wind capacity to cover calm winter days. That's unlikely to fly as more and more people develop concern over the turbines' impacts on wildlife.

All's not lost, though: what California lacks in a dependable wind resource it more than makes up for in sunshine. The same figures today that show wind at a paltry one percent or so of the state's current demand show solar peaking at just below 900 megawatts -- and it's December. That's about five times the output of this time last year. A combination of solar and storage might just be the best lead renewables strategy for California as we approach that theoretical 2030.

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