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CVOW & Storage

Ed Reid's picture
Vice President, Marketing (Retired) / Executive Director (Retired) / President (Retired), Columbia Gas Distribution Companies / American Gas Cooling Center / Fire to Ice, Inc.

Industry Participation: Natural Gas Industry Research, Development and Demonstration Initiative Chair, Cooling Committee (1996-1999)   American Gas Association Marketing Section...

  • Member since 2003
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  • Nov 8, 2022
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Originally posted here. 

Dominion Energy has proposed to build Coastal Virginia Offshore Wind (CVOW) a 176 wind turbine farm off the Virginia coast. The Virginia Legislature had predetermined that such a project was in the public interest. The Virginia State Corporation Commission (VSCC) has approved a rate increase related to funding of CVOW, though many project details remain to be finalized and many environmental approvals are outstanding.

The rating plate generating capacity of CVOW is 2.6 GW. Project output would be expected to range from 0 GW to 2.6 GW. The International Energy Agency estimates an annual capacity factor of 50% for offshore wind turbines. I will use that estimate here, since there is no significant US experience with wind farms off the US East coast. Therefore, CVOW would be expected to generate an annual average of ~1.3 GW, ranging from ~1.6 GW in Winter to ~0.8 GW in Summer.

The daily and seasonal output variations would require significant long-duration storage to allow the output of CVOW to be dispatchable. For example, the stored electricity required to make up the difference between annual average capacity and average summer capacity (1.3 GW – 0.8 GW = 0.5 GW) for a single Summer month would be approximately 372 GWh (0.5 GW * 24 hours/day * 31 days), while the capacity required to make up the difference between average winter capacity and average summer capacity would be approximately 595 GWh (0.8 GW * 24 * 31).

Dominion Energy is the majority owner of the Bath County Pumped Storage Station (BCPSS), which was frequently described as “the largest storage battery in the world”. BCPSS has a generating capacity of 3 GW and a total storage capacity of 24 GWh. Therefore, BCPSS could replace the full capacity of CVOW for approximately 9 hours (24 GWh / 2.6 GW). It would require 15-25 storage stations like BCPSS to render CVOW dispatchable seasonally based on storage capacity.

Construction of a pumped storage facility with the capacity of BCPSS would cost approximately $4 billion, or approximately $160 per kWh ($4,000,000,000 / 24,000,000 kWh), or approximately half the NREL estimated cost of battery storage. The cost of each new storage station would be approximately 40% of the estimated cost of CVOW.

Of course, the above calculations are all estimates since all of the inputs to the calculations are estimates. However, the largest uncertainty regarding the overall project is the amount of storage capacity which would be required in the Dominion Energy grid to maximize the value of the contribution of CVOW on an annual basis. Determining the optimal storage capacity would require a detailed analysis of the generating capacity mix planned for the future Dominion Energy renewable plus storage grid, including allowances for load growth resulting from population increases and from accommodating the federal goal of Net Zero by 2050.

The 2050 Net Zero Dominion Energy grid would be expected to exhibit annual electricity demand and consumption approximately 4 times current demand and consumption. That would be a massive technical and economic challenge.   

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