Waves off the California coast could provide as much as 140 TWh of electricity a year with today’s technology, but the state faces several obstacles to achieving that potential, according to a new report.
The California Energy Commission report, released in draft form Nov. 26, said that wave and tidal energy could diversify the state’s electricity portfolio, complementing intermittent renewable resources such as solar and wind, and help California meet its renewable energy targets.
Wave energy systems could be deployed as distributed energy resources to serve local demand, such as at ports, remote communities, military installations or marine research stations, the report said.
Wave energy systems also could be located with floating offshore wind.
“Colocation of wave energy and offshore wind energy can reduce project development costs through shared expenses of infrastructure, operations and maintenance, and licensing, and could provide enhanced energy yield and better predictability,” the CEC said in its draft report.
But barriers to wave energy projects are many, the report noted. Because the industry is at an early stage, a single technology or device has yet to emerge as the preferred solution. Costs remain high, and environmental impacts may vary depending on the technology type and location.
There are also grid integration challenges, including connection costs, grid stability and regulatory frameworks.
The report recommends promoting further research on the potential value of wave and tidal energy devices as clean, firm resources as well as the devices’ environmental impacts.
Exploring market incentives to support investment in wave and tidal energy technology is another recommendation, as is developing a clear regulatory process for projects.
The report on wave and tidal energy resources is included in the CEC’s 2024 Integrated Energy Policy Report (IEPR) update.
The evaluation is the result of California Senate Bill 605 of 2023, which directed the CEC to evaluate the feasibility, costs, and benefits of wave and tidal energy and to submit a report to the legislature by Jan. 1, 2025.
CEC said it will follow up with a report on suitable sea space for offshore wave and tidal energy — another requirement of SB 605.
Resource Size
The CEC report assesses both wave and tidal energy — two types of marine energy resources.
It cites the findings of a 2021 report from the National Renewable Energy Laboratory (NREL) that looked at the size of marine energy resources across the U.S. NREL focused on the size of the “technical resource,” which is the amount of energy that could potentially be harnessed using existing technology.
The technical resource is a portion of the total energy resource that’s theoretically available; NREL also noted that the technical resource is greater than the “practical resource,” which considers environmental and regulatory constraints and other barriers.
The wave energy technical resource off California’s coast is 140 TWh/year, NREL said, which equals 69% of the state’s 2019 net electricity generation and is enough to power 13 million homes.
The state’s technical resource for tidal energy is comparatively small, at 0.89 TWh/year, and is concentrated at the entrance to San Francisco Bay, where the resource is 0.78 TWh/year.
“Commercial-scale marine energy projects in California would likely use wave energy instead of tidal energy because of more abundant wave energy resources,” the CEC said in its report.
Elsewhere on the West Coast, Oregon’s wave resource is 93 TWh/year. That’s 1.5 times the state’s 2019 net electricity generation and “could allow Oregon to be a net exporter of wave-powered electricity,” NREL said in its report.
Technology Types
Many different types of technology have been developed to convert wave energy to electricity.
One type of system is an overtopping converter, in which waves spill over the crest of the device and into an above-sea-level reservoir. The controlled release of water from the reservoir drives turbines to generate energy.
A Danish company called Wave Dragon makes one well-known overtopping device. The company says its platform “is highly suitable as a floating foundation for wind turbines.”
Point absorbers are a type of wave energy converter that uses a floating buoy or platform that moves up and down or back and forth as waves pass by. The movement, relative to a fixed object such as an anchor, is converted into mechanical energy and then into electricity.
The advantages of point absorbers are that they are small and easy to move, and can be deployed individually or assembled in arrays, according to Aspen Environmental Group, which performed an analysis of wave and tidal energy for the CEC.
A California-based company, CalWave, completed a 10-month demonstration of its xWave point absorber technology off the coast of San Diego in July 2022. The power and data generated by the x1 pilot device was exported via subsea cable to the Scripps Institute of Oceanography research pier.
“As offshore wind development is growing rapidly in the U.S. and globally, we recognize the significant opportunities for wind and wave farm co-location,” CalWave CEO Marcus Lehmann said in a statement upon completion of the pilot project.
CalWave has now been contracted by the Department of Energy to deploy its first utility grid-connected system at the 20 MW PacWave test site off the central Oregon coast. The test site is expected to be in operation in mid-2025.
CalWave submitted its own recommendations to the CEC on how to move forward with marine energy.
Those include setting statewide marine energy deployment targets of 100 MW by 2030, 500 MW by 2035 and 2,500 MW by 2040.
The company also recommended the CEC consider providing matching funds for DOE awards, clarify state regulatory processes and quantify potential savings to ratepayers from integrating marine energy into the grid.