The Potential Of Ocean Energy Technologies
The ocean covers more than 70% of the Earth’s surface and contains an enormous amount of energy. Both tidal flows and waves can be used to produce renewable electricity, with enough sites available to theoretically meet all of the world’s current electricity demand. Wave energy’s power density (the amount of electricity that can be generated from a given area) is more than four times that of solar and wind energy. Ocean energy converters are also much less visually intrusive than offshore wind turbines. However, despite its immense potential, the operational capacity of wave energy currently stands at less than 13 MW. In contrast, solar and wind energy provide more than 150,000 MW of electricity generation. To further put it in perspective, the amount of solar energy deployed back in 1996 surpasses today’s combined capacity of wave and tidal power.
Solar and wind power grew rapidly over the last three decades driven initially by government incentives, but also because of rapid innovation and economies of scale driving down cost. Ocean power could be starting down a similar path.
A variety of innovators have made fast progress toward commercializing ocean energy technologies attracting more than $950M in investments. Access to testing facilities has been a bottleneck in the past, but the US DOE recently awarded $25M for eight projects that will test at PacWave (a new wave energy test facility being developed off the Oregon Coast). Momentum is building and many experts now predict gigawatts of capacity to be deployed by 2030.
This blog will take a closer look at ocean energy technologies, including the opportunities and challenges associated with the ocean energy industry, how the technologies can complement solar and wind energy, and whether now might be a good time to invest.
Ocean Energy Technologies Are Improving
There are two major types of ocean energy being pursued today: tidal and wave. Tidal generation is more mature and simpler from an engineering perspective. A turbine similar to what is used in a hydroelectric power plant is placed in an area of strong tidal flows.
The most commonly developed tidal turbine is called a horizontal-axis tidal turbine. Orbital Marine Power and Verdant Power are two tidal energy companies currently developing such technology, but their mounting systems differ. Orbital Marine Power’s turbines (shown in Figure 1) are attached to a moored floating platform, whereas Verdant Power’s turbines (shown in Figure 2) are mounted to the floor of a body of water. One of Orbital Marine Power’s tidal turbines is a multi-MW scale system and has been operating in Orkney since 2021.
The best tidal locations are where you have a large bay and the generator can be placed at the mouth. This limits the number of high-quality deployment locations. Wave energy can be deployed in most coastal areas, however, some locations (such as off the coast of the Pacific Northwest) have more available energy. In the United States, the available wave energy is more than six times that of tidal energy. However, converting the oscillating motion of waves into a smooth power output can be challenging.
The most commonly developed Wave Energy Converter (WEC) is called a point absorber WEC. CalWave, Oscilla Power, and CorPower are wave energy companies currently developing such technology. CalWave’s xWaveTM Series WEC (shown in Figure 3) generates electricity from the relative motion between a float submerged below the ocean’s surface and the ocean floor. Oscilla Power’s Triton-C WEC (shown in Figure 4) operates similarly, however, its float is only partially submerged and reacts against a ring-shaped reaction structure to generate electricity. Most designs primarily use vertical motion to produce power, but Wavepiston’s WEC is an alternative design that captures the horizontal motion of waves. As well as the devices mentioned, there are also many other configurations.
The goal is to develop an efficient device that can operate in a variety of wave conditions (e.g. various wave heights and frequencies), while still outputting smooth power. Some use direct drive while others push hydraulic fluid through a turbine. Hydraulic reservoirs, power electronics, batteries, and/or ultracapacitor energy storage are used to smooth and provide stable power output.
Another challenge is designing a WEC that can function in harsh ocean conditions, such as extreme waves that can have a wave height over 30 feet. Extreme waves are a major design challenge because they can damage devices and add cost for reinforcing structures. Calwave and Oscilla Power overcame this challenge by designing their respective WECs to submerge below a certain depth in order to reduce damage. CorPower developed a phase control technology that can detune the buoy in extreme waves. Wavepiston has flaps that are designed to release and provide a bypass for larger waves if the force is too great.
In all of these systems, there are tradeoffs for cost and complexity while improving efficiency and allowing operation across a wider range of conditions. Routine planned maintenance is much more challenging while operating at sea and needing to work within favorable weather windows. In order to demonstrate and improve reliability, companies are conducting tests before deploying their devices in the ocean. For example, CorPower designed and built a dry test facility (rated at 7.2 MW) to test the robustness and reliability of their systems. They also operated a half-scale prototype for six months off the coast of Portugal.
Diversified renewables
Perhaps the most exciting benefit of ocean energy is its potential to complement intermittent power from solar and wind. As the sun sets each day and air slows down, waves continue to move. With the rapid installation of solar and wind energy technologies, the grid is struggling more to deal with intermittency. Waves are more predictable than solar and wind, and individual devices that use ocean energy have, on average, a larger capacity factor (the ratio of produced to potential electrical power production). WEC capacity factors are typically ~25–35% vs. ~18% for utility-scale PV systems. This will become even more important as the share of intermittent renewables like solar and wind continues to increase. The potential complement between wave, wind, and solar is shown in Figure 4, which shows plots of energy potential for wave, wind, and solar at one location in California. Co-locating wave and offshore wind technologies could decrease power intermittency (and could also share transmission infrastructure). In this way, ocean energy can be considered a competitor to battery energy storage rather than wind and solar.
Reducing cost and scaling up
Both wave and tidal technologies are too expensive today for widespread adoption. The current average LCOEs are about $0.43/kWh and $0.33/kWh, respectively, while solar and wind LCOEs can range from about $0.05/kWh to $0.10/kWh. However, with incentives like the Renewable Electricity Production Tax Credit and the Business Energy Investment Tax Credit, many are predicting that these technologies can gain traction and begin moving down the cost curve. The cost of utility-scale PV projects and onshore wind decreased by 88% and 68%, respectively, in this same way, driven by early incentives/subsidies (such as the Energy Policy Act of 2005 and the Investment Tax Credit). Based on a report by IRENA, there are almost 3 GW of wave and tidal projects in the pipeline, and by 2030, there could be 10 GW of commercially deployed projects and the LCOE could decrease below $0.15/kWh. Detailed bottom-up techno-economic models developed by the WEC companies themselves generally line up with these projections and have identified specific opportunities for cost reduction through some combination of economies of scale and continued design improvements. Island communities could be good early customers because they have limited land area and some communities often pay over $0.3/kWh for electricity mainly generated from fossil fuels.
Perhaps now is the time a diversified portfolio of new renewables, such as ocean energy, will begin to emerge as cost-effective (other contenders include enhanced geothermal and small modular reactors). There are over 25 tidal stream energy developers and more than 30 wave energy developers with a Technology Readiness Level (TRL) greater than 6. By continuing to invest resources into improving ocean energy technologies, the ocean could soon provide a significant and reliable source of energy to communities all around the world.
If you want to learn even more about ocean energy, we will be hosting an Ocean Energy webinar on Thursday, May 25 at 3:00 PM ET.
Prime Movers Lab invests in breakthrough scientific startups founded by Prime Movers, the inventors who transform billions of lives. We invest in companies reinventing energy, transportation, infrastructure, manufacturing, human augmentation, and agriculture.
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