Scottish Wave Energy Plans Move Forward 100
It's been a long time coming (2007, 2005, and 2002 respectively), but the project to harness wave energy off the Scots coast is finally coming together. Reader krou writes: "The BBC is reporting that ten sites on the seabed off Scotland in Pentland Firth and around Orkney have been leased to energy companies with the hopes of generating wave and tidal energy. 'Six sites have been allocated for wave energy developments potentially generating 600 megawatts of power and four for tidal projects, also generating 600 MW.' The leases were awarded to SSE Renewables Developments, Aquamarine Power, ScottishPower Renewables, E.ON, Pelamis Wave Power, OpenHydro Site Developments, and Marine Current Turbines. Scotland's First Minister Alex Salmond said that 'These waters have been described as the Saudi Arabia of marine power and the wave and tidal projects unveiled today — exceeding the initial 700MW target capacity — underline the rich natural resources of the waters off Scotland.'"
Re:The big question (Score:3, Informative)
The force of gravity between the earth and the moon is roughly 2*10^20 newtons. Moving the moon 10 meters further from the earth would take over 10^13 Joules of energy (and that only accounts for the change in gravitational potential).
Furthermore, the rotation of the earth is already causing us to loose the moon at a rate of about 3 cm per year. If we were to reduce tide to the point where the ocean did not fluctuate at all, perhaps we wouldn't loose the moon in 1000000 years.
Re:They're missing some.... (Score:2, Informative)
The aim is to generate 1.2 gigawatts
I think they'll find they need another 10MW to achieve what they're really after....
Nah - We only need to wait 6 more years and surely the likely invention of "Mr. Fusion" will negate the need for that power and should help us clean up some of our household refuse at the same time!
Re:The big question (Score:2, Informative)
The moon is moving away. We only have 600 million more years before there will be no more total solar eclipses.
Re:The trouble with Scotland (Score:2, Informative)
Troll??!!
Yeah maybe.. It was said by an Irishman [imdb.com]. I really doubt he was serious. In fact, I think he was just reading a quote. I think you people should lighten up a bit.
Re:The big question (Score:4, Informative)
We sometimes forget just how heavy water is, or how much energy ocean waves carry.
Some time ago, I did some statistical analysis of wave heights in Scapa Flow, not far away from the site proposed here in northern Scottish waters. It has very steady, large swells.
Imagine a wave (or swell) of 10m peak height, extending 2 km across, and 50m front-to-back. That's a nice 0.3 * 10^6 kg of water ... move it forward at 30kph ... repeat every 10 or 20 seconds, and you've got 10^9 Joules/second, about 1GW. For the surface wave. (More energy is transferred more steadily by sub-surface currents.)
Lunar tidal flows are so much larger than these that the prospect of drawing enough energy from open waters to do anything to earth - moon movements seem to be off by many orders of magnitude.
Full disclosure: I used to be a pretty good physicist, but that was a long time ago.
Re:The big question (Score:2, Informative)
Temporarily, yes. But once the earth-moon system is tidally-locked, it will come back. Extracting tidal energy slows the earth's rotation and hastens the process.
Of course, a million years is slightly exaggerated. It's probably more than 30 billion years, without help, and of course the sun would vaporize us all long before then. We would have to build a lot of tidal generators to actually speed it up.
Re:The big question (Score:5, Informative)
You calculated the kinetic energy of a mass of water moving forward at 30kph. In a wave water is not moving forward at the wave speed, but rather gently in an elliptic trajectory. I gather you used 10m as amplitude and not crest to through height.
The energy flux of waves is given by the formula which you can find on this wikipedia page [wikipedia.org]. A 20m (crest to through) wave with a period of 10s over a lenght of 50m gives you 20MW of wave energy. Still a lot, but almost 2 orders of magnitude less than 1GW.
Re:Transmission (Score:1, Informative)
Dounreay nuclear power station is just across the water.
Re:The big question (Score:1, Informative)
You used 50m of coastline. He used 2000. 40 times 20 MW is 800MW which isn't that far from 1 GW.
Re:Tsunamis! (Score:3, Informative)
Tidal generators don't create 'calm' zones, because tides aren't driven by a pushing force, rather by a pulling force (lunar gravitational pull), so water is merely dragged across/through a generator and continues to be dragged after it has passed the 'obstacle'.
Wave powered generators such as the Salter Duck did leave calm zones behind them as they absorbed the waves' vertical kinetic energy in long arrays strung out perpendicular to the direction of the waves' travel. However, these designs were dropped a long time ago in favour of 'snake' designs which harness as much energy but without causing these calm areas behind them.
Sea Snake on YouTube [youtube.com]