We Have Solar Power and Wind Power, Here Comes Moon Power

May 14, 2014

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When Mark Baker looks up at the moon at night, he does not see magic or mystery. He ponders megawatts.

Twice a day, like clockwork, the moon’s gravity makes the seas ebb and flow. For Baker, a marine renewables business manager at GE Power Conversion, the tides are the perfect source of energy, more predictable and reliable than wind or solar power. “Some U.K. locations have significant tidal head ranges,” he says. “They offer a tantalizing energy generation potential.”

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The moon could join the sun as a source of renewable energy.

GE Power Conversion is testing tidal turbine generators and other underwater technology in turbines standing on the sea floor near the Orkneys in Scotland and at Ramsey Sound in Pembrokeshire, Wales.

Baker says that GE is ready to scale up the power system to a large array of tidal turbines planned for the bottom of the Pentland Firth, a narrow channel that separates the Orkneys from the northern tip of Scotland. The channel has some of the fastest moving currents in the U.K. (see video).

People tried to capture tidal and wave energy since the Middle Ages when  they used “tide mills” to grind grain. Ideas Lab reported that the first tidal power station was the Rance tidal power plant built between 1960 and 1966 in La Rance, France. But the technology did not catch on because of its high capital cost and the limited availability of sites with sufficient tidal flows.  

Although innovations in turbine technology and design have begun to lower those costs and make deployment possible in more areas, the technology is “decades behind other forms of renewables and will likely need significant government support and research to become a true clean energy player,” according Ideas Lab.

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The Orkneys’ rugged coast has some of the strongest tides.

The U.S. is currently underwriting development of 17 tidal and wave energy demonstration projects. The U.S. Department of Energy’s latest assessment identified up to 1,400 terawatt hours of potential tidal energy generation per year—one terawatt-hour of electricity is enough to power about 85,000 homes. Developing just a small fraction of the wave and tidal energy available in the U.S. could power millions of American homes.

“Wave and tidal energy represent a large, untapped resource for the United States and responsible development of this clean, renewable energy source is an important part of our all-of-the-above energy strategy,” said Assistant Secretary for Energy Efficiency and Renewable Energy David Danielson in a statement last year.

BBC recently described Scotland as “a Saudi Arabia of renewable energy potential.” The Pentland Firth project alone could supply almost half of Scotland’s electricity needs - as much as 1.9 gigawatts.

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The turbines resemble large aircraft propellers submerged in 180 to 240 feet of water. They stand in strategic “pinch points” of the firth, where the tides rush in and out at the highest speeds.

Engineers can capture energy from the vertical and horizontal movements of the tides. Some teams have also used buoys that generate electricity from the up and down movement of the waves. But “it happens to be roughly an order of magnitude more difficult to mount and maintain equipment on the surface of the sea,” Baker says. “Companies have put in wave systems only to find them dashed upon the rocks.”

Baker believes that tidal power generation arrays will start popping up in the U.K. and elsewhere in the world. “Tidal lagoon power stations could soon also become a reality in the U.K.,” he says. “They are capable of utility-scale power generation.”