Estimates and Averages - ORIGINAL CONTENT

Developers of renewable energy generation installations frequently focus their marketing efforts on estimates of the number of homes the installations would serve. The developers’ estimates are not based on consistent assumptions and cannot be directly compared.

Orsted’s recently approved Ocean Wind 1 development, to be located off the New Jersey coast near Atlantic City and Ocean City, would consist of one hundred 11MW wind turbine generators, for a total capacity of 1,100 MW. This would suggest annual generation, at a 100% capacity factor, of 9,600 GWh. The International Energy Agency uses a capacity factor of 50% for offshore wind. We will use that figure here, since there is no offshore wind capacity factor data for the US East Coast. This suggests annual production of approximately 4,800 GWh for Ocean Wind 1.

Orsted projects that Ocean Wind 1 would serve 500,000 homes. The US Energy Information Administration reports average US residential electricity consumption as 10,600 kWh per year. Based on these numbers, Ocean wind would have to generate 5300 GWh per year, or a capacity factor of approximately 55%.

Dominion Energy’s proposed Coastal Virginia Offshore Wind (CVOW) development, to be located off the Virginia coast near Norfolk, would consist of one hundred seventy-six 15 MW wind turbine generators, for a total capacity of 2,600 MW. This would suggest annual generation, at a 100% capacity factor, of approximately 22,800 GWh, or approximately 11,400 GWh at a 50% capacity factor.

Dominion projects that CVOW would serve 660,000 homes, which would require generation of approximately 6,996 GWh based on the EIA residential consumption figure. That would suggest a capacity factor of approximately 30%, far lower than the IEA figure, and even lower relative to the Orsted estimate for Ocean Wind 1.

The estimates above are based on a number of averages: average wind resource; average capacity factor; average maintenance and repair allowances; and, average residential electricity consumption. The available wind resource varies on time scales from minutes to hours to days to seasons, as does residential energy consumption and demand. The use of averages loses a lot of the detail of the match between customer load and generator output.

Since each of these industrial wind installations would be connected to a grid with a far larger customer base than the claimed number of residential customers served, above average output would be absorbed by other loads on the grids, displacing a portion of the output from some form(s) of conventional generation. Below average generator output would require support from some form(s) of conventional generation.

Arguably, fluctuations in generator output and customer load could also be compensated for by additions to and withdrawals from some type of energy storage capacity. However, there is no energy storage capacity included in either of the wind projects discussed above. The issue of storage can be deferred as long as there is sufficient excess conventional generating capacity available to compensate for the fluctuation of the output of the wind facilities and maintain a capacity reserve margin. However, as conventional generating capacity is retired due to age or regulation, and additional intermittent renewable generating capacity is added, addressing the issue of storage cannot be avoided.