A North America-wide grid with 12 hours of back-up storage could supply 80% of the continent’s electricity with wind and solar, based on a review of 36 years of weather data by the Carnegie Institution’s Ken Caldeira and three other authors.
“Assuming minimal excess generation, lossless transmission, and no other generation sources, the analysis indicates that wind-heavy or solar-heavy U.S.-scale power generation portfolios could in principle provide ∼80% of recent total annual U.S. electricity demand,” the study abstract states.
“However, to reliably meet 100% of total annual electricity demand, seasonal cycles and unpredictable weather events require several weeks’ worth of energy storage and/or the installation of much more capacity of solar and wind power than is routinely necessary to meet peak demand.”
The reference to “no other generation sources” suggests the study made no allowance for some of the emerging solutions to grid reliability, like using already-installed hydroelectric capacity to back up wind. Hydro currently accounts for 7% of total electricity generation in the U.S.—and 58.9% in Canada, where some utilities have been avidly exploring new import-export deals with utilities to the south.
“Our team took a simplified approach aimed at understanding fundamental geophysical constraints on wind and solar power,” said lead author Matthew Shaner of University of California Irvine. “We looked at solar and wind power availability on an hourly basis across the U.S. and determined how much of current electricity demand could be met by varying amounts of solar panels, wind turbines, and energy storage, in addition to changes in the electricity grid.”
“Our work indicates that wind and solar would need to be supplemented by some kind of dispatchable power like natural gas or huge amounts of storage,” Caldeira said. “The natural gas emits greenhouse gases and the storage is super expensive, so we need a search for better ways of supplying electricity when the sun is not shining, and the wind is not blowing.”