Wave power has been grabbing the spotlight lately, but the US also has vast tidal power potential and the race is on to engineer a tidal energy device that can overcome some serious obstacles, namely interference with shipping, aquatic life, and recreation. It looks like a research team at Brown University is on to a solution, so let’s take a look and see what they’re up to.
Ocean Power Potential In The US
Just last August, the Energy Department announced $16 million in funding for cutting edge ocean energy projects, and the company Verdant Power has already begun operating a hydrokinetic tidal energy turbine right in the heart of New York City.
Speaking of East Coast energy potential, the offshore wind sector is also coming on strong. The massive Cape Wind project in Massachusetts has just won out against a Koch-supported legal challenge, and another utility scale offshore wind power project is under way in Rhode Island.
Getting back to tidal energy, despite the obstacles to shallow water deployment there is one key advantage that tides have over wave or wind power, and that is their unerring around-the-clock reliability.
Reliability is becoming a moot point as next-generation energy storage technology begins to mainstream, but given the localized nature of the emerging renewable energy economy, tidal energy could still provide the most cost-effective resource for some regions.
The Brown University Tidal Energy Solution
Brown University has focused its tidal energy project on the juiciest locations, which also happen to present the greatest challenges.
According to an Energy Department report cited by Brown, the most effective locations are in shallow bays and inlets, typically no deeper than ten meters, where the narrowness of the channel speeds up the pace of tidewater both coming and going.
That basically cuts out conventional underwater turbines, which rely on a windmill style configuration. The blades would be too short to be effective, but long enough to create potential hazards for wildlife, shipping, and recreation.
The solution is a hydrofoil configuration. Based on the same principle behind the design of airplane wings, a hydrofoil is oriented so that it is pushed up a pole by incoming water, then pushed back down.
Writer Kevin Stacey of Brown recaps the advantages of the hydrofoil design compared to turbines:
A single wing can span an area that would require a series of several turbines placed side-by-side — an expensive and inefficient arrangement. Gaps between the turbines would allow water to slip through untouched, which is a waste of potential power. A wide wing, on the other hand, could generate power from the entire span.
Since the project is supported by ARPA-E, the Energy Department’s cutting edge research funding agency, you can expect some extra bells and whistles.
One is a collapsible design, when enables the devices to duck under passing ships.
Another is a self-teaching computer algorithm that monitors the wing and fine-tunes its motion to maximize efficiency as tidal conditions change, testing out different strokes to decide which is the most efficient.
The project is still in the prototype stage, with a 16″ wide model undergoing tests in the lab, and the outlook is promising.
So far the device has been gathering power up to four times more efficiently than conventional hydrokinetic systems, and the lab expects even better results in the field, where flows will be faster.
The team is currently seeking additional federal funding and an industry partner to launch a new prototype at a testing facility in New Hampshire, so stay tuned.
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