Slashdot Mirror
Underwater Ocean Currents Used to Power Bermuda
Saevio writes to tell us The Royal Gazette is reporting that Bermuda is planning to sink a power generator off the coast to take advantage of ocean currents. The company providing the service, Belco predicts that they will be able to provide approximately 10 percent of the island's energy needs. From the article: "The 150ft long deep sea generator with a four-blade turbine inside would cut Belco's dependency on oil and also benefit the environment by cutting future fuel emissions, he added, stating that the company needed to increase its generating capacity before 2010. Mr. Madeiros, who hailed the technology 'mind-boggling', said: 'This is cutting edge technology, not used anywhere else. One can't help but get excited by this technology.'"
Belco's original press release.
It's 150 feet long. I'm sure that there's nothing to worry about in that respect. If you're talking something the size of the State of Florida or the entire size of the UK, then maybe you'll have something to think about.
"If all the world's a stage, I want to operate the trap door." - Paul Beatty
Er, I meant RPS, not RPM, but whatever.
You can't change that... by gettin' all... bendy.
As a matter of fact, yachts these days fairly often have immersed generators. As the yacht gets hauled along by wind power, the generator trails and spins in the water.
They generate quite impressive amounts of electricity at the cost of a knot or two in speed.
Mind you, the water speed of those trailing generators is considerably higher, quite often, than the gulf stream, but it's quite enough for some impressive juice.
However it doesn't work so great in context of the Gulf Stream.
The Gulf Stream is not some huge tide-like current hundreds of kilometers wide, instead it's typically only a kilometer or two wide. Indeed if you fly over it (I have a number of times) it appears as a clearly defined 'river', of a much different color then it's surrounding waters, with large swirls & eddies sometimes breaking off of it, cutting through the otherwise featureless ocean.
So while Bermuda may be a crumb the Gulf Stream is a spider strand.
That said I don't think putting a few turbines, or even 'a lot' will have significant effect on it. The total energy in it is incredible and it's an ongoing process, there's not some hose at one end that can be cut off stopping it all, but rather a push & pull process that keeps the whole thing going. Even if Bermuda were able to pull out 1% of the energy in it that would be less then the effect of a slightly windier or cloudier day in the Gulf on it, completely lost in the noise level.
By the way, if you're ever on the East Coast of the US & have some friends who fly ask them to take a gander next time they're over the seashore for any eddies off of the Gulf Stream that are close to the shore. They're much lighter colored then the usual cold dark blue Atlantic waters, easy to spot. If there are any by a beach then take the opportunity to go swimming in it - it's amazing. Cold cold cold Atlantic waters then suddenly bathwater warm, often with tropical fish trapped inside the thermocline. I've enjoyed a few off of Provincetown, Mass. (tip of Cape Cod) and they're times I treasure , and friends who were along retell of the experience over & over.
I don't read ACs: If a post isn't worth so much as a nom de plume to its author then I wont bother either.
What happens when you start extracting mega watts out of the wind pattern? What about changes to the micro climate just down wind from the wind farm?
The latter is irrelevant to all but the people who live there, in the same way the shadow effects of any industrial plant are irrelevant to any but the people who live there. It is not an environmental issue as normally understood--it is a land use or zoning issue. This is not to say it isn't important--it is--but we have centuries of law dealing with things like this, so there are really no signficant unknows with regard to wind farms except for the possibility that they do not have any significant negative downstream effects. That's a pretty good kind of uncertainty to have: "Nothing bad might happen! We just don't know!"
With regard to the question of what happens when we start extracting megawatts from the wind, this is a question that can be answered on the back of an envelope, which I will now proceed to do. Air has a density (rho) of about 1 kg/m**3. Consider wind at 10 kn, which is about 5 m/s. The power per square meter is 0.5*rho*v**3, or about 60 W, of which about half is available to windmills. Wind power has an energy density of about 30 W/m**2, maybe as high at 100 W/m**2 in windy areas. The Canadian province of Ontario has a winter load of about 20 GW and a summer load of about 25 GW. So we're talking about at least 200 million square meters of swept area to accomodate all of it, and maybe over three times this much. This is equivalent to a line of windmills with 100 meter span, 2000 km long removing half the kinetic energy from all the air that passes through them. This is not a small environmental influence. It is hard to imagine that this would not quite fundamentally change energy transport and therefore weather patterns over hundreds of kilometers.
I didn't expect that result when I started writing the paragraph above, but since I'm a scientific rather than a religious environmentalist, I can't simply ignore it. Wind power is still worth pursuing, but it is very clear that it is never going to be more than one element in a mix of alternatives, and is very unlikely to ever generate more than 10% of our power if its environmental impact is to be kept moderate.
Blasphemy is a human right. Blasphemophobia kills.
Um, no, temperature changes will not eliminate the Gulf Stream entirely. The northern split-off extension of the Gulf Stream called the North Atlantic Drift is thermocline-driven, but the rest of the Gulf Stream is just the inevitable effect of the Earth's rotation -- the Coriolis effect on the current-driving winds.
Wind power has an energy density of about 30 W/m**2, maybe as high at 100 W/m**2 in windy areas.
Reviewing my own estimate, this number is obviously very sensitive to the average wind velocity, which comes in as the cube. It turns out that average wind speed data for Ontario are available, and my estimate of 5 m/s is on the low side for coastal regions. But even with a more optimistic 8 m/s we are still talking 125 W/m**2 after efficiency considerations, which is only a little higher than my 100 W/m**2 high-end value.
It is also clear that placing wind turbines along the shore will have the lowest environmental impact, because the wind is giving up a lot of energy there in any case.
Blasphemy is a human right. Blasphemophobia kills.