Artificial island could store offshore wind energy

Artificial island could store offshore wind energy

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News & Events - Engineering News

February 7, 2013

Offshore wind has been struggling in recent years to bring costs down low enough to compete with onshore installations, much less the more established technologies like natural gas and coal. The small European nation of Belgium thinks it might have found one of the keys to bringing down these expenses, and it turns out it may involve building a new shore a bit closer to these distant turbines.

MIT's Technology Review reports that Belgian legislator Johan Vande Lanotte, the country's deputy prime minister as well as minister of economy consumer affairs and North Sea, has introduced a new concept for offshore wind power using entirely familiar technology. Under Lanotte's plan, the country will construct a man-made island for the sole purpose of storing seawater for a pumped-storage hydroelectric plant.

Filling in the gaps
Over the past few years, the costs of wind power have fallen dramatically, allowing it to legitimately compete on price in some parts of the world. OpenEnergyInfo reports that the levelized cost of energy from onshore wind has fallen to a median of as little as 6 cents per kilowatt-hour, compared to 5 cents per kilowatt-hour for both pulverized coal and combined cycle natural gas.

Offshore has been slower to catch up, with a median price of 10 cents per kilowatt-hour and a peak price nearly double that of onshore wind, but the improvement even over the past few years has been impressive enough to draw renewed investment interest.

As many engineering innovations as the technology has seen, however, it's hard to ignore the fact that wind power still comes up lacking in some key categories - namely providing power on demand.

The two solutions to intermittent power generation are either providing highly responsive peak power generation or cost efficient storage. Unfortunately, most companies have found that the newest storage technologies - from flywheels to batteries - do not quite measure up in terms of value, making it more cost effective to simply shut down wind turbines when production outstrips demand.

Proven technologies
The one counterexample is the long-established pumped-storage hydroelectric plant. Common particularly in the U.S. Northeast, these plants pump water from one reservoir into a higher one when power prices are low, often at night, and then release it through a hydroelectric turbine when demand spikes, providing a clean source of low-cost electricity.

For many onshore wind farms this approach is impractical, since many turbines are located in areas without access to sufficient water reserves.

As Belgian officials realized, however, offshore wind turbines are surrounded by water on all sides, all they lack is the reservoir.

To fix this problem, Belgium proposes to construct an artificial atoll - a type of island that features a lagoon entirely encircled by land - more than two kilometers across and roughly three kilometers off the coast. The island would feature its own hydroelectric plant and pumps, like any other pumped-storage plant, but would draw upon the vast reserve of the ocean.

"It's not totally crazy—it's within the realm of reason. The question isn't whether we can do it," Haresh Kamath, program manager for energy storage at the Electric Power Research Institute, told TR. "It's whether it makes sense and that's the thing that needs further studies and understanding."

Unusual circumstances
This "energy atoll" would pose its own unique problems compared to traditional pumped-storage plants. In particular, using salt water in place of fresh water is bound to contribute to greater wear and tear on equipment, raising maintenance costs. In addition, while hydroelectric plants generally suffer from high initial capital costs, building an island three kilometers off the coast will push the initial price even higher.

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