The ultimate goal of renewable energy advocates is to get enough solar and wind energy on the grid to force power plants that spew fossil fuels to power down. Until now, that’s been wishful thinking. But for the first time, there’s evidence that the wish can come true.
Scientists with the US Department of Energy’s National Renewable Energy Laboratory have run complex computer simulations that mimic the operation of the western grid, which encompasses parts of the US, Canada and Mexico. They ran five simulations, ranging from one with no renewable power production to one where solar and wind generated 33% of the grid’s electricity, to determine the impact on coal and natural gas-fired power plants. They were particularly interested in the costs in cash and carbon emissions of firing up those plants when wind and solar generation declined (for instance, because the wind stopped blowing or clouds passed overhead).
The results: Every megawatt-hour (MWh) of electricity produced by solar and wind farms displaces 1 MWh produced by a coal-fired power plant and 3 MWh of natural gas-fired electricity. (A megawatt-hour is the equivalent of 1 million watts produced continuously over an hour’s time by a power plant.)
The study also dispels fears that adding more wind and solar to the grid would actually increase greenhouse gas emissions because coal and natural gas power plants would need to be more frequently fired up to plug any gaps in renewable output.
The scientists found that fossil fuel plant costs did increase when one-third of electricity generated came from solar and wind. But the additional wear and tear—between $35 million and $157 million annually—paled in comparison to the $7 billion saved when solar and wind displaced coal and natural–gas fired power.
Not to mention, of course, that carbon emissions fall dramatically under that scenario. In the western US, computer models showed that such greenhouse gas emissions fell between 24% and 26% when one-third of the electricity came from wind and solar. Harmful pollutants such as nitrogen oxides and sulfur dioxides also fell by similar percentages.