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Scotland Builds Power Farms of the Future Under the Sea
HughPickens.com writes "The Pentland Firth is a raw, stormy sound between the Scottish mainland and the Orkney Islands, known for some of the world's fastest flowing marine waters. Daily tides here reach 11 miles per hour, and can go as high as 18 – a breakneck current that's the reason people are describing Scotland as the Saudi Arabia of tidal power. Now Megan Garber reports in The Atlantic that a new tidal power plant, to be installed off the Scottish coast aims to make the Scotland a world leader for turning sea flow into electricity. Underwater windmills, the BBC notes, have the benefit of invisibility—a common objection to wind turbines being how unsightly they are to human eyes. Undersea turbines also benefit from the fact that tides are predictable in ways that winds are not: You know how much power you're generating, basically, on any given day. The tidal currents are also completely carbon-free and since sea water is 832 times denser than air, a 5 knot ocean current has more kinetic energy than a 350 km/h wind.
MeyGen will face a challenge in that work: The turbines are incredibly difficult to install. The Pentland Firth is a harsh environment to begin with; complicating matters is the fact that the turbines can be installed only at the deepest of ocean depths so as not to disrupt the paths of ships on the surface. They also need to be installed in bays or headlands, where tidal flows are at their most intense. It is an unbelievably harsh environment in which to build anything, let alone manage a vast fleet of tidal machines beneath the waves. If each Hammerfest machine delivers its advertised 1MW of power, then you need 1,000 of them to hope to match the output of a typical gas or coal-fired power station. "The real aim," says Keith Anderson, "is to establish the predictability which you get with tidal power, and to feed that into the energy mix which includes the less predictable sources like wind or wave. The whole point of this device is to test that it can produce power, and we believe it can, and to show it's robust and can be maintained."
MeyGen will face a challenge in that work: The turbines are incredibly difficult to install. The Pentland Firth is a harsh environment to begin with; complicating matters is the fact that the turbines can be installed only at the deepest of ocean depths so as not to disrupt the paths of ships on the surface. They also need to be installed in bays or headlands, where tidal flows are at their most intense. It is an unbelievably harsh environment in which to build anything, let alone manage a vast fleet of tidal machines beneath the waves. If each Hammerfest machine delivers its advertised 1MW of power, then you need 1,000 of them to hope to match the output of a typical gas or coal-fired power station. "The real aim," says Keith Anderson, "is to establish the predictability which you get with tidal power, and to feed that into the energy mix which includes the less predictable sources like wind or wave. The whole point of this device is to test that it can produce power, and we believe it can, and to show it's robust and can be maintained."
A typical (500 megawatt) coal plant burns 1.4 million tons of coal each year. As of 2012, there are 572 operational coal plants in the U.S. with an average capacity of 547 megawatts.
http://www.ucsusa.org/clean_energy/coalvswind/c01.html#.VFe77y0wJIo
I don't know where the poster got their numbers from, but an average coal plant is around 500 megawatts not 1000. This would imply that you only need 500 of the hammerfest machines to equal a powerplant. They should probably be more careful in the future to use accurate data.
That would be a neat trick...
“He’s not deformed, he’s just drunk!”
re: "since sea water is 832 times denser than air, a 5 knot ocean current has more kinetic energy than a 350 km/h wind"
Kinetic energy is an integration of the linear mv dv so equals 1/2mv^2 (whereas momentum is the simple product mv.)
So let's set the mass of a volume of wind at 1 and the mass of the same volume of sea water at 832 units.
The kinetic energy of the wind @ 350km/h = 1/2 * 1 * 350^2 = 61,250 units
The kinetic energy of the water @ 5 knots = 1/2 * 832 * (5 * 1.852)^2 = 35,671 units (1 knot = 1.852 km/hr)
-- Insert witty one-liner here. --
With such large amounts of energy why oh why are they pissing about with such tiny turbines? Modern wind turbines are 6MW+, some hydro power turbines are over 700MW each. Are they trying to destroy the financial viability of the project with unimaginative small scale thinking?
Scroll up to the post just above yours, referencing the Bay of Fundy and its failed turbine approach. Big turbines go boom when water move too fast, it turns out. Smaller turbines are made of materials with similar strength, but have much less force exerted on them under extreme tides. And, unlike a hydro power turbine, they can't force the full flow of the water to pass exclusively through the turbine here; a turbine that attempted the same level of energy harvesting would instead build up a head of backpressure, and the water would flow around it. That is, until the tide ripped the thing off the floor of the bay.
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Uh, about that, the Rance tidal plant in France has operated for 40 years with nothing but sacrificial anode protection and it looks pretty good to me (see page 22).
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