California offshore wind could help flatten duck curve, study finds

September 10, 2020

by Peter Maloney
APPA News
September 10, 2020

Offshore wind resources along the central California Coast are well suited to meet demand when it is most needed, according to a new study by researchers at California Polytechnic State University in San Luis Obispo.

California leads the nation in solar power with over 28 gigawatts (GW), but as the sun sets, consumer demand rises, creating a sudden need for other forms of energy to meet daily peak needs, a phenomena that has come to be known as the “duck curve.”

“The alignment between potential offshore wind power production and demand highlights the important role that offshore wind energy could play in meeting California’s ambitious renewable energy goals,” Yi-Hui Wang, the research scientist who led the Cal Poly team, said in a statement.

Instead of taking a conventional approach to identifying areas with promising wind resources by using mean wind speeds, the researchers said they compared the diurnal and seasonal patterns of offshore wind power production to diurnal and seasonal patterns of power demand across California and to power production from other renewable resources, such as solar and land-based wind power.

They then used the relative alignment between the power production of the various renewables and demand to calculate a demand-based value and, looking at the daily and seasonal fluctuations in recent wholesale power prices, they generated an estimate of the wholesale dollar value of power produced.

Solar power generation in California peaks in June at noon while the peak in the value of power demand occurs in July and August at about 4:00 pm, the researchers noted, adding that land-based wind power generation peaks in June at midnight while the value of power demand peaks in August at about 10:00 pm.

Offshore wind power generation, on the other hand, aligns well with daily peak demand, which occurs between 7:00 pm and 8:00 pm, depending on the month, the researchers said.

Regarding the wholesale value of offshore wind, the researchers report that due to strong variations in pricing, these values show more extreme daily and seasonal changes than power production. The wholesale value of power is close to zero on a typical spring noon because of the solar overgeneration and peaks during evening hours when solar generation is low and demand is high.

“The framework by which we assess spatial and temporal patterns in offshore wind energy production and its value can be applied to other regions where offshore wind is being considered,” the researchers wrote.

The federal Bureau of Ocean Energy Management, which funded the study, is considering California’s central coast region for the location of the state’s first offshore wind farm and has proposed priority areas for leasing by energy companies.

“Looking at this wind data in relation to maps of fisheries, whale and seabird activity will help identify locations where offshore wind farms could add the most value and yet have the least impact on local economies and marine wildlife,” biology professor Crow White, a member of the Cal Poly research team, said in a statement.

The researchers noted that the greatest wind speeds, which would produce the most energy, are found farther from the coast. And while most existing offshore wind farms are installed close to shore in waters less than 160 feet deep, floating wind farms in deeper waters have begun operation in Europe.

“Floating offshore wind farms are now a proven technology and game-changer in many respects,” physics professor and team member Ryan Walter said in a statement.

The Cal Poly study did not include a full economic analysis because of a lack of data on the costs of building and operating offshore wind farms and the losses associated with transmitting the power back to shore.

“Ultimately, we hope this information and our ongoing work will inform the conversation, helping the policymakers and citizens of California decide if, how and where to prioritize renewable offshore wind energy,” biology professor and team member Ben Ruttenberg, said in a statement.

As a next step, the Cal Poly team is looking at a study that would estimate the total amount of electricity wind farms in the area could produce and how those wind farms might affect the broader economy of San Luis Obispo County.

The study is available here.

Redwood Coast Energy Authority taps consortium for offshore wind partnership

The Redwood Coast Energy Authority, a California local government Joint Powers Agency, in 2018 selected a consortium of companies to enter into a public-private partnership to pursue the development of an offshore wind energy project off the Northern California coast.

In 2019, Monterey Bay Community Power, a California community choice aggregator, and Castle Wind LLC said that they signed a memorandum of understanding that outlines the mutual interests and intent of both parties to enter into future long-term power purchase agreements for approximately 1,000 megawatts of energy from an offshore wind project being developed by Castle Wind.

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