Small wave power plants could be the way forward for wave power


Anyone looking at the ocean can be in awe of the apparent power of each wave. This power has the potential to provide energy to homes and businesses on land, as well as floating facilities and ships at sea. But how do you turn energy from the oceans into usable forms, such as electricity or water? desalinated water?

One way to harness the energy of the ocean is to use a device called a Wave Energy Converter, or WEC. To date, WEC designs have generally centered around large, rigid bodies that float in the water and move relative to each other as the waves roll by. These bodies typically absorb energy from ocean waves and concentrate that energy in a centralized conversion mechanism, such as a rotary generator or hydraulic piston.

Today, the National Renewable Energy Laboratory (NREL) is exploring ways to significantly advance the design and development of wave energy converters. With funding from the Water Power Technologies Office of the United States Department of Energy (DOE), NREL researchers are developing concepts in which many small energy converters can be aggregated to create a single structure. With this new approach to wave energy development, the field of Distributed Embedded Energy Converter (DEEC-Tec) technologies could help the promise of substantial renewable energy production from ocean waves become a reality. .

Figure 1. Stretched and deformed sample volume of a flexWEC structure illustrating the basic use of Distributed Integrated Energy Converters (DEEC) to create energy from wave energy. The sample volume has two sections where material is removed to clarify their respective arrangements: (1) the middle section has the frame of conforming support material removed, and (2) the straight section has both the frame compliant support and the DEECs removed. The illustration shows how the combined semi-continuous nature of DEEC technologies supports the development of materials and structures for ocean wave energy harvesting and conversion devices.

Why distribute and integrate several energy converters?

One of DEEC-Tec’s most innovative elements is its ability to create flexible converters of ocean wave energy, sometimes referred to as flexWEC. These devices inherently have broadband ocean wave energy absorption and conversion characteristics, which means they can pick up energy over a wide range of ocean wave heights and frequencies.

DEEC-Tec offers a new range of possibilities on how ocean wave energy can be harvested and converted and how flexWEC designs could power a variety of end uses both on land (powering homes and businesses) and at sea (supplying navigation buoys and marine vehicles). Some of these uses will support DOE’s Powering the Blue Economy â„¢ initiative, which aims to advance renewable marine energy technologies, such as navigation buoys or autonomous underwater vehicles, to promote economic growth in communities. industries such as aquaculture.

“Our goal with DEEC-Tec is to dramatically expand the way we currently conceptualize and envision the use of ocean wave energy,” said Blake Boren, a researcher at NREL, who studies wave energy converters. for more than 10 years. “There is a wide range of possibilities for developing these wave energy converters based on DEEC-Tec, and we are accelerating this exploration process. “

Figure 2. Three possible flexWEC archetypes showing the undeformed and dynamically deformed states of flexWEC structures based on DEEC-Tec. The yellow flexbodies in each archetype represent the conforming DEEC-based structures shown in Figure 1. (Note: Nothing is to scale; figures and scenes in the flexWEC archetype are illustrative only.)

How DEEC-Tec advances wave energy

DEEC-Tec concepts are assembled from many small energy converters which together form a structure that can wave like a snake, stretch and bend like a sheet of cloth, or expand and contract like a ball. As the overall structure bends, twists, and / or changes shape as ocean waves pass, each built-in energy converter can transform some of that ocean wave energy. in electricity.

A flexWEC has several advantages:

  • A wider spectrum of energy capture. With a wide range of motions and deformations available, DEEC-Tec-based wave energy converters absorb and convert ocean wave energy in a much wider range of wave conditions – both in terms of size and frequency – compared to rigid body converters.
  • Mechanical redundancy. The ability to use several hundred or thousands of on-board distributed energy converters can ensure that ocean energy conversion occurs even if one or more of these converters stop working.
  • Resilience. The flexibility of the wave energy converter based on the DEEC-Tec provides an inherent survival mechanism: the ability to exit and absorb excessive and dangerous surges of energy from large storms and rough seas.
  • Favorable materials. Wave energy converters based on DEEC-Tec could be made from recycled materials or simple polymers. These replace heavier, sometimes more expensive materials that have historically been used for the development of wave energy converters, such as steel or the rare earth elements required for large permanent magnets. In addition, existing mass manufacturing techniques could be used for simple and cost effective manufacture of DEEC-Tec components.
  • Easier installation. DEEC-Tec-based wave energy converters can be folded, deflated or otherwise compacted for transport from a manufacturer to a deployment site. Likewise, for installation, they can be extended to cover large areas as required. This would allow robust energy capture with lower investment costs.
  • Reduced maintenance programs. Monitoring the relative performance of many small devices determines the need for maintenance of the DEEC-Tec-based wave energy converter throughout the structure. The inherent redundancy of the structure potentially results in less frequent inspections and maintenance requirements.
  • Almost continuous structural control. A DEEC-Tec-based wave energy converter is made up of many small transducers – mechanisms that convert one form of energy into another. Some of them can serve as simple electric actuators, which can change the shape and motion of the converter in response to ocean wave conditions. This will allow better recovery of ocean wave energy and better control of the conversion.

Look to the future

While there are many benefits to using DEEC-Tec in the research and development of ocean wave energy converters, there are still unknowns that need to be understood and resolved. To this end, NREL researchers are identifying materials, structural designs, electronic systems, and manufacturing methods that could advance DEEC-Tec concepts for marine renewable energy. NREL’s work also includes validation and coded design of DEEC-Tec subcomponents, computational models to simulate performance, and device proofs of concept for construction and validation.

As part of this research, NREL is collaborating with outside institutions, such as the University of Colorado-Boulder, the Dutch energy company SBM Offshore, the US Naval Research Laboratory and Sandia National Laboratories.

Learn more about the work of NREL at distributed on-board energy converter technologies.

Article and images courtesy of the NREL, the US Department of Energy.

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