May 20, 2007

Tidal Power

Tidal power is one of the few of the renewable sources of energy that is also reliable (along with hydro, geo-thermal, and nuclear). The tides run like clockwork and can be reliably predicted years, even centuries, in advance. The UK is uniquely positioned to be able to take advantage of tidal power like no other county, thanks to both our long coastline and some of the strongest tidal currents in the world.

One method of harnessing this power would be to build a barrage across the bristol channel forcing all the water to flow though a set of turbines. This has some significant problems. One is the fact that the area around Bristol is still a major shipping destination and so the barrage (a huge, and hugely expensive, feat of engineering in itself) would need lock gates in it capable of taking a container ship. Another is that by the way it would distort the tides cause a large environmental impact on an already sensitive region. Which is why the EU has banned it.

Luckily a barrage is not needed. Turbines powered by the enormous tidal currents available would work almost as well, there is currently a tidal generator of this type already in operation at Lynmouth built by Bristol based Marine Current Turbines, without the environmental impact. Also since tidal turbines are more scaleable than a barrage. With a barrage you have to build the entire thing before you can get any power out. With an array of turbines you get power as soon as the first turbine is in operation. Should it then look like you chose the wrong spot for whatever reason you can stop at that point and choose another one, saving massive amounts in money and environmental damage. SeaGen the next the prototype that is scheduled to flow the SeaFow device at Lynmouth is already in construction and planned to be installed this summer. The one megawatt of power that this machine will generate will be feed into the grid.


Anonymous Anonymous said...

Is tidal 24/7 like hydro, geothermal, nuclear, coal, oil? How many gigawatts can it push (not piffly little megawatts)?

2:49 am  
Blogger chris said...

Tide levels follow a sinusoidal pattern repeating over 12 and a bit hours. To give continous power you would need an additional pumped hydo system to smooth this out, filling the resevoir during maximum power and emptying it during minimum. With that proviso yes tidal is 24 hours a day, 7 days a week, 52 weeks a year. It is extremely reliable and predictable, just the kind of thing that can be used for an electrcity grid's base load. A tidal barrage, like the one now not going to happen, would produce a 1 and 2 gigawatts continous power, with a peak production of around 8 gigawatts. These numbers depend on where it is sited, the further along the bristol chanel you go the more water would be behind it, so the more energy you can get out of it. Geothermal isn't really an option in the UK, but tidal is comparable to fossil fuels, hydro or nukes. A barrage also has the advantage of producing less CO2 over the entire life cycle than fossil fuels, about the same as hydro, but more than nukes. Tidal turbines will not produce as much power as a barrage, but will require far less concrete putting them closer to nukes in terms of carbon.

[numbers from Wikipedia]

3:27 pm  

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