Looking Before Leaping: The Debate over 100% Renewables

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In early May 2017, California Senate President Pro Tem Kevin de Leon introduced S.B. 100, the California Clean Energy Act of 2017, which seeks to put the state on a path to 100 percent clean, renewable energy by 2045. In a press conference supporting the bill, Sen. de Leon cited clean energy’s job creation and economy-boosting properties. Other California Senate leaders analogized this bill to the Kennedy Administration’s drive to place a man on the moon and said that California would continue to be the model for energy policy.

Intrigued by S.B. 100, I began to wonder about the economic and engineering research supporting this drive in California and elsewhere to accelerate already aggressive renewable targets. I was intrigued by an academic debate which came to the attention of some PACE partners and online followers in late June, and thought it useful to share it here and recommend that others in the energy policy space delve into the two papers described below.

On June 27 2017, twenty-one researchers released a report in the Proceedings of the National Academies of Science (PNAS). Assembled from institutions including NOAA, Stanford, Carnegie Mellon, and Columbia University, their purpose was to evaluate “a proposal for reliable low-cost grid power with 100 percent wind, water and solar.” The “Group of 21” (my label for them) includes voices and institutions that have studied energy issues and contributed to studies finding paths forward to significant de-carbonization of the U.S. electric grid. So what led them to combine efforts and take on this topic?

The Group of 21’s report aims directly at a 2015 study, also published in the PNAS, and explains why it failed to make the case that a 100 percent renewable future is assured by 2050. The 2017 report concluded that “[p]olicy makers should treat with caution any visions of a rapid, reliable, and low-cost transition to entire energy systems that [rely] almost exclusively on wind, solar and hydroelectric power.”

In November 2015, four researchers from Stanford and Berkeley published a study in the PNAS intended to show that the “greatest concern” expressed by the traditional utility sector of load loss due to renewable energy variability could be overcome by “low-cost, no-load-loss, non-unique solutions.” They provided an overview of models and technology they believed could propel the entire American economy (electricity, transport, heating/cooling, and industry) to a future, estimated as approximately years 2050 – 2055, where “no natural gas, biofuels, nuclear power, or stationary batteries are needed.”

How would we achieve the “100 percent vision” (also my term)? The 2015 paper makes some key assumptions, including that:

  • geothermal storage is nearly universally available, to the extent that “all building air and water heating is “coupled with storage using underground thermal energy storage”
  • 85 percent of the transportation load and 70 percent of the loads for industrial high temperature, chemical and electrical processes are flexible or produced from hydrogen.

The Group of 21 agreed with the premise that it’s “theoretically possible to build a reliable energy system excluding all bioenergy, nuclear energy, and fossil fuel sources … [g]iven unlimited resources to build variable energy production facilities, while expanding the transmission grid and accompanying energy storage capacity enormously.”

The Group of 21 then laid out a series of statements in response to the 100 percent vision as expressed by the 2015 study:

  • “includes a wide range of currently un-costed innovations” such as “widespread use of hydrogen to fuel airplanes, rail, shipping, and most energy-intensive industrial processes”
  • “assumes the availability of multi-week energy storage systems that are not yet proven at scale” and
  • “deploys them at a capacity twice that of the entire U.S. generating and storage capacity today”
  • relies “heavily on … hydroelectric capacity expansion … at current reservoirs without consideration of hydrological constraints or the need for additional supporting infrastructure”

Both studies contain additional information and citations and I encourage you to make your own assessments. While an academic debate of this nature might seem far-removed from policymaking circles, it is it. There are important lessons here that can help inform policymakers on substance and process. When we leap forward without looking closely and asking tough questions, or let banner slogans stand in for rigorous analysis, consumers and industries get left behind and progress actually slows down.

We can and should point toward an energy future, but we are all responsible for doing so in a manner that accepts the realities of technology, economics, and politics and unfolds based on sound science and due diligence. This hard work often isn’t exciting enough to support a press conference, but it’s exactly what’s needed to assure affordable, reliable power in 2017 on to 2045 and beyond.