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New Marine Energy Harvesting Devices Are (Finally) Heaving Into View – Renewable Energy

New Marine Energy Harvesting Devices Are (Finally) Heaving Into View


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When the topic turns to marine energy, building a better mousetrap is the name of the game. Wind, waves, and tides all combine to provide a practically limitless source of renewable energy. That’s an alluring target for innovators. The challenge is to engineer marine energy conversion systems that can withstand the constant pressure of wind, waves, and tides while warding off saltwater corrosion, and the victors are beginning to emerge.

Marine Energy Rising In Europe

CleanTechnica will be reporting from The Hague next week for the 2023 Ocean Energy Europe Conference and Exhibition. It’s the 10th anniversary of the annual event and we’re looking forward to seeing how far the marine energy field has come in ten years.

Meanwhile, let’s take a look at the goings-on over at the Dutch Marine Energy Centre, which has earned the post of Platinum Sponsor at the event.

DMEC is highlighting five marine energy companies at the exhibition hall. None of them have crossed the CleanTechnica radar yet, so it’s time to play catchup.

1. Ocean Grazer is an underwater pumped hydropower energy storage system. The concept is similar to the familiar above-ground pumped hydro systems, but different.

During periods of low electricity demand, energy from offshore wind turbines is deployed to pump water into flexible bladders, where it is held under pressure. When the grid needs more electricity, the pressure forces water from the bladders to a rigid reservoir. Along the way are turbines that generate electricity.

2. SeaQurrent has developed TidalKite, a kite-like device designed to harvest the low-velocity motion of tides and ocean currents. “The kite wings capture the water flow, accelerating the kite through the water,” SeaQurrent explains. “The kite creates a huge lift force that is transferred via the tether to the power take-off.”

3. REDstack harvests the electricity that happens when fresh water meets seawater. The RED in REDstack stands for reverse electrodialysis, with electrodialysis referring to the action that happens when electricity is applied to a membrane. In reverse, the system generates electricity.

“From the mixing of 1 m³ of river water with 1 m³ of sea water, 0.5 kilowatt hours of electricity can theoretically be obtained at 25 oC. This corresponds to a power of 1.8 MW from a flow rate of 1 m³/s fresh and 1 m³/s salt water,” REDstack explains.

4. Water2Energy leverages docks, locks, and other existing infrastructure to harvest tidal energy with vertical axis turbines. The turbines can also be installed in open water. At locations where fish mortality is a concern, the company notes that its new turbine design is much more fish-friendly than conventional designs.

5. Speaking of fish, the fifth company showcased by DMEC is FishFlow Innovations. As the name suggests, FishFlow specializes in devices that enable fish to navigate in and around marine infrastructure.

“All our products have been developed with particular attention for the natural preference and behaviour of fish,” the company explains. “We develop products with key features: fish friendly, energy efficient and silent, e.g. pumps, turbines, pump impellers, ship propellers, water sieves and siphon fish ladders.”

More Marine Energy From DMEC

The exhibition is just the tip of the marine energy iceberg supported by DMEC. The organization also leads the Ocean Energy Scale-Up Alliance, aiming to corral 300 gigawatts of seagoing renewable energy.

In a policy paper issued last year, OESA draws attention to a piggyback approach that integrates marine energy harvesting devices with offshore wind farms in both the North Sea and Baltic Sea.

“Multi-use is a way of using available space efficiently. Joint supervision and maintenance are also possible, to lower overall costs which is beneficial for emerging technologie[s] like marine energy,” OESA North Sea region recommended last year. “The synergy and system benefits for local ecosystems are abundant.”

“The Dutch government would like to implement a nature inclusive multi-use park filled with innovative technologies, such as marine energy, in a current wind park optimising the used space,” they added. “The Dutch approach to multi-use could set the norm for other countries.”

The idea of combining wave energy converters with offshore wind farms has already begun to bubble up. The piggyback approach could also include offshore green hydrogen production.

Activity in the green hydrogen field is beginning to surface in the Baltic Sea, where six EU states are exploring the idea of using offshore wind turbines to run electrolyzer systems for producing hydrogen from water.

Too bad Russia is going to miss the Baltic Sea marine energy boat. Russia has all-season access to the copious offshore energy resources of the Baltic Sea through its ownership of Kaliningrad Oblast, a sliver of land between Poland and Lithuania. However, Russia’s murderous rampage through Ukraine has shut the door that opportunity, among many others.

More Marine Energy For The US

Meanwhile, over here in the US, the profile of marine energy is slowly beginning to rise. In addition to a smattering of commercial projects under way, the US Energy Department of Energy and its partners are building an elaborate new wave energy test site off the Oregon coast. The new site complements an existing near-shore wave energy testing facility in Hawaii.

The Energy Department has also expressed an interest in taking the marine energy field to the next level of sustainability, by incorporating more recycled and recyclable materials into underwater systems.

One area of focus is a new thermoplastic resin for tidal energy turbine blades, as a more recycling-friendly alternative to conventional epoxy blades. Back in 2021, the new blades outperformed their epoxy counterparts in a six-month trial on the East River in New York City, where the company Verdant Power has been running the first tidal energy operation licensed in the US.

The NREL team is currently conducting a series of tests on pieces of the thermoplastic resin blades to assess how they survive stress and saltwater over the long term (the East River is not a normal freshwater river, it’s a salty tidal waterway).

Another workaround is also emerging in the form of a plant-based epoxy formula that could be applied to underwater turbine blades.

NREL researchers are currently working on recycling hard-to-recycle carbon fibers with the help of a biobased epoxy binder. The idea is to take advantage of the higher levels of oxygen and nitrogen in biomass, compared to petroleum-based materials.

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Image: Ocean energy potential in Europe courtesy of DMEC.


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