Document
Cohen testimony: Building America’s clean future
Armond Cohen|Jul 24, 2019
This congressional testimony presented by Armond Cohen, Executive Director for the Clean Air Task Force, provides helpful insight into the costs of using batteries exclusively to provide instantaneous capacity during periods when wind and solar resources are insufficient. His testimony also discusses the cost of a renewable energy-only solution in California. A portion of his testimony is provided below. The full testimony can be downloaded from the document links on this page.
This congressional testimony presented by Armond Cohen, Executive Director for the Clean Air Task Force, provides helpful insight into the costs of using batteries exclusively to provide instantaneous capacity during periods when wind and solar resources are insufficient. His testimony also discusses the cost of a renewable energy-only solution in California. A portion of his testimony is provided below. The full testimony can be downloaded from the document links on this page.
Cohen Testimony Excerpt:
To further illustrate the cost advantages of a full portfolio of wind, solar, and firm resources, I will consider data for California. I have chosen California because it is a state rich in wind and solar resources, a state committed to eliminating carbon emission from its power grid by 2045, but also a state that adopted technology-inclusive portfolio approach: its new law, SB 100,17 requires 60% of the state’s electricity to come from renewable sources but allows for other technology families to comprise the balance.
The fundamental dynamic driving the need for firm energy is seasonal variability. It is commonplace to say that “the wind doesn’t always blow and the sun doesn’t always shine.” But this statement does not capture the real challenge of a wind- and sun-dominated electric system. Wind and sun do not just vary on daily cycles; they vary substantially over weekly and monthly periods.
As you can see, there are multiple weeks of average surplus above demand during the summer months but substantial deficits September through February.
The consequence of this seasonal variation is that, even when California procures enough wind and solar output to meet total electricity demand on an annual average basis, roughly 27% of hours of the year cannot be served by wind and sun.
In theory, we could use battery storage to harvest surpluses and use them in deficit periods. But this is where cost comes in. The sheer amount of storage that must be built to capture maximum surplus, and then utilized infrequently, becomes cost prohibitive, even at very low storage costs.
In Figure 14, we see that the accumulated surplus during the year equals 35,946,633 MWh, or roughly 14% of the California’s annual electric usage. To contain that much energy at peak storage time, you would need a storage system equivalent in instantaneous capacity larger than the generating capacity of the entire US electric grid.
