PNAS Article Argues Renewable Energy Cannot Fully Replace Traditional Energy by 2050

(p. B1) Democrats in both the United States Senate and in the California Assembly have proposed legislation this year calling for a full transition to renewable energy sources.
They are relying on what looks like a watertight scholarly analysis to support their call: the work of a prominent energy systems engineer from Stanford University, Mark Z. Jacobson. With three co-authors, he published a widely heralded article two years ago asserting that it would be eminently feasible to power the American economy by midcentury almost entirely with energy from the wind, the sun and water. What’s more, it would be cheaper than running it on fossil fuels.
And yet the proposition is hardly as solid as Professor Jacobson asserts.
In a long-awaited article published this week in The Proceedings of the National Academy of Sciences — the same journal in which Professor Jacobson’s manifesto appeared — a group of 21 prominent scholars, including physicists and engineers, climate scientists and sociologists, took a fine comb to the Jacobson paper and dismantled its conclusions bit by bit.
. . .
(p. B5) The conclusion of the critique is damning: Professor Jacobson relied on “invalid modeling tools,” committed “modeling errors” and made “implausible and inadequately supported assumptions,” the scholars wrote. “Our paper is pretty devastating,” said Varun Sivaram from the Council on Foreign Relations, a co-author of the new critique.
. . .
The weakness of energy systems powered by the sun and the wind is their intermittency. Where will the energy come from when the sun isn’t shining and the wind isn’t blowing? Professor Jacobson addresses this in two ways, vastly increasing the nation’s peak hydroelectricity capacity and deploying energy storage at a vast scale.
“To repower the world, we need to expand a lot of things to a large scale,” Professor Jacobson told me. “But there is no reason we can’t scale up.”
Actually, there are reasons. The main energy storage technologies he proposes — hydrogen and heat stored in rocks buried underground — have never been put in place at anywhere near the scale required to power a nation, or even a large city.
His system requires storing seven weeks’ worth of energy consumption. Today, the 10 biggest storage systems in the United States combined store some 43 minutes. Hydrogen production would have to be scaled up by a factor of 100,000 or more to meet the requirements in Professor Jacobson’s analysis, according to his critics.

For the full commentary, see:
Eduardo Porter. “ECONOMIC SCENE; Traditional Sources of Energy Have Role in Renewable Future.” The New York Times (Tuesday, June 21, 2017): B1.
(Note: ellipses added.)
(Note: the online version of the commentary has the date June 20, 2017, and has the title “ECONOMIC SCENE; Fisticuffs Over the Route to a Clean-Energy Future.”)

The PNAS “devastating” critique of a total switch to renewable energy, is:
Clack, Christopher T. M., Staffan A. Qvist, Jay Apt, Morgan Bazilian, Adam R. Brandt, Ken Caldeira, Steven J. Davis, Victor Diakov, Mark A. Handschy, Paul D. H. Hines, Paulina Jaramillo, Daniel M. Kammen, Jane C. S. Long, M. Granger Morgan, Adam Reed, Varun Sivaram, James Sweeney, George R. Tynan, David G. Victor, John P. Weyant, and Jay F. Whitacre. “Evaluation of a Proposal for Reliable Low-Cost Grid Power with 100% Wind, Water, and Solar.” Proceedings of the National Academy of Sciences 114, no. 26 (June 27, 2017): 6722-27.

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