While scientists agree that widespread deployment of solar and wind generation could substantially reduce U.S. greenhouse gas emissions, a study led by Christopher Clack and published in the Proceedings of the National Academy of Sciences last week demonstrates that exactly how that increased deployment will be achieved is still a hotly debated subject. Clack et al.’s study challenges a 2015 study led by Mark Jacobson, of Stanford University’s Atmosphere / Energy Program, that was also published in same journal. While Jacobson’s study concluded that the United States could transition to 100% renewable power by 2050, Clack’s study concludes that “[r]elying on 100% wind, solar, and hydroelectric power could make climate mitigation more difficult and more expensive than it needs to be,” and points out that previous analyses have found that the most feasible route to a low-carbon energy future is one that adopts a diverse portfolio of technologies.
Clack et al. argue that shortcomings and errors in Jacobson’s study render it unreliable as a guide about the likely cost, technical reliability, and feasibility of a 100% wind, solar, and hydroelectric power system. Among these errors, according to the Clack study, was the Jacobson study’s conclusion that hydropower facilities would increase generation by over 30%. The Clack study argues that “this explanation shows a fundamental misunderstanding of the operation of electricity markets and the factors determining hydroelectric supply,” and failed to take into account that the primary factors limiting hydroelectric capacity are water supply and environmental constraints. The Clack study also criticizes the Jacobson study for modeling errors, a lack of modeling for electric power transmission, reserve margins, and frequency response, and inadequate scrutiny of the climate models used to generate weather data.
While Clack et al. conclude that moving to 100% renewable generation is unrealistic, they point out that a number of other studies have concluded that that 80% decarbonization of the US economy could be achieved at reasonable cost. For reference, the EIA reports that in 2016, wind accounted for 5.6% of the total U.S. electricity generation, solar for 0.9%, and hydro for 6.5%.