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The Heavyweight Sea Snail
Roland Piquepaille writes "Scotland, like many European countries, must comply with regulations requiring that a mandatory percentage of the energy it uses comes from renewable sources. For Scotland, this percentage will be 18% in 2010 and 40% by 2020. One of the programs in development is Ian Bryden's sea 'Snail' program. The Snail is a 30-ton anchoring device which uses hydrofoils -- wings that 'fly' in the water -- to generate enough power from tidal waves to service 10,000 homes by 2007. This overview contains more details and a picture of a prototype of the Snail with its six wings." There are several mentions of this in UK newspapers and the Scottish government webpages.
According to this site:
"Currently, although the technology required to harness tidal energy is well established, tidal power is expensive, and there is only one major tidal generating station in operation. This is a 240 megawatt (1 megawatt = 1 MW = 1 million watts) at the mouth of the La Rance river estuary on the northern coast of France (a large coal or nuclear power plant generates about 1,000 MW of electricity). The La Rance generating station has been in operation since 1966 and has been a very reliable source of electricity for France. La Rance was supposed to be one of many tidal power plants in France, until their nuclear program was greatly expanded in the late 1960's. Elsewhere there is a 20 MW experimental facility at Annapolis Royal in Nova Scotia, and a 0.4 MW tidal power plant near Murmansk in Russia. "
I also recall having seen articles talking about attempts in Norway to capture wave/tidal energy for electricity generation.
I'm always a fan of renewable energy. I just wanted to point out that this is more an attempt to do something in a new way than to do something new.
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YES; BUY DANISH WINDMILLS. There, did my part for the Danish windmill industry :-)
Last year more than 25% of the electricity in Denmark was produced by windpower, that's pretty good.
I heard the secondary articles too, and it seems that this device uses down downward force exerted on the "wings" to power a turbine of some sort.
It seems pretty logical, and it makes me think - Most of the water generators I've read about seem to be tide based - where this is more using the force of the incomng water laterally. I wonder how practical it would be to set up these devices inside of the oceans currents, or fast flowing channels. Using these 'wings' to generate force that way seems to me like it could be pretty effective. Of course - IANAPhysicist - I'm just a network geek... but it seems pretty practical to me.
The hydrofoils aren't generating power they merely provide a cheap way of holding a turbine down on the seabed.
Ups, always check you facts before posting, it should only be 20%... Damn
http://www.windpower.org/
Over what period of time?
You're (at least in the US) usually billed in kilowatt-hours (kWh). I'm no expert, but I doubt most homes use more than 0.5kWh at anything other than peak times (weekday evenings and weekend afternoons).
Appliances (again, in the US) all come with a sticker saying how many kWh they use in a year. A refrigerator is usually around 1000. That's a little less than 3 kWh a day, or 0.125 kWh (period... in an hour). That's only 1/4th of your constant usage allowance. How many other household appliances run 24/7? Probably none.
A good storage mechanism would store that unused energy for use at peak times. A poorly designed system would just fail over to a traditional power grid at peak times. In any event, it still reduces the load on the main grid.
Of course, my experiences are from my house in the USA... maybe Scotland is full of wasteful, electricity-hungry, even-worse-than-American people... but I doubt it.
This link explans better how the sea snail works. http://www.friendsofscotland.gov.uk/education/rene wable.html
Basically, the foils are to keep the snail anchored while the turbine is moved by the water.
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This is all part of an alien conspiracy to bring the moon crashing down on us! Awaken to the truth before it's too late!
Actually, tidal friction slows the rotation of the earth and raises the orbit of the moon. Extracting tidal power will increase the friction and thus the rate at which this happens.
(Of course if there WAS a chance of bringing down the moon that would make for QUITE the "environmental impact".)
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
In this case it's not oil that we are dependent on but COAL. Now while we mine coal right here in the US remember that coal mining is by far the most dangerous occupation in the US, for each coal plant in the US one coal-miner is killed each year in an accident. This doesn't count the long term healt and psychological effects that mining has on a person. Nor does it take into effects the polution generated by a coal plant. Sorry, but oil fuels some of our energy needs (heating and automobiles) but very little oil is used in electrical power generation.
That's almost exactly our average consumption in my house (3BR, 4 people) here in the U.S.
I use mostly CF light bulbs, but do have an electric range and clothes dryer that runs pretty often (2 of the 4 occupants are small and generally muddy).
(I also buy a good portion of my electricity from a small local hydro plant for a small surcharge, thanks to my friendly municipal utility).
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Considering the god-knows how many tonnes of water already being supported by the sea-floor - i cant see that 200 extra tonnes will make that much difference to the N/m2
While it is true that coal mining is still a rather dangerous occupation, the polution generated by coal-fired power stations isn't as bad as many people belive. In the last few decades, coal has come quite a long way in reducing toxic emmisions. Modern coal plants combust the fuel much more completly, and are outfitted with high-tech (and very expensive) scrubbers to remove the really toxic byproducts (especially sulfer).
Considering that our coal supplies will long outlast our oil supplies, I think that its still a good idea to invest in cleaner coal technologies. Linky.
The problem with weights, is they have to be able to hold it in place under the maximum force of water. By making the pressure down relative to the force of water the installation / choice of locations is easier. As the force of water grows, the 'snail' is held tighter to the ground.
Not to nitpick, but coal mining is the number 2 most dangerous occupation in the world IIRC. Commercial fishing is substantially more dangerous.
The fact is that private companies do not have the long-term interests of society in mind. They have a mandate to increase profits.
Socialism is bad when it causes the state to interfere in short-term market issues (ie, price fixing), because no single entity can affectively micromange such a complex system. But applying broad long-term pressures to the market is not socialism, its a smart policy that recognizes the deep complexity of the market system.
An article in the Scottish press has more useful info.
It only generates 150KW. That's not much. Typical wind turbines generate 200KW to 700KW each, on windy days. (Average values are much lower.) Typical nuclear power plants generate 1,000,000KW. Powering a home takes about 1-2KW on average, so 10,000 homes require perhaps 15,000KW.
The SNAIL people want to move up to the 750KW range or so. That's more reasonable. As wind power people have discovered, having huge numbers of little turbines isn't cost effective. But somewhere around a few hundred KW per turbine, the economics start to work. If you can find a good site with steady wind. As with dams, there aren't that many good sites.
It will probably take several decades of operating experience to turn this into a reliable technology, just as it did with windpower. It's been half a century since the Grandpa's Knob loss of blade accident. The first big power-generating wind turbine oversped and threw a blade several hundred feet. For many years, nobody built one that big again. Gradually, the aerodynamics and control problems were figured out. It's taken that long to make large wind turbines work reliably and profitably.
Anything with moving parts in the ocean is likely to be high-maintenance. Making one of these things work reliably for decades will be tough. Maintenance will be costly. There's no guarantee of success.
In short, there's no breakthrough here until it's been running for a few years without breaking.
I wholeheartedly agree.
The production tax credit (PTC) for wind in the US was 1.5c per kilowatt-hour because that was needed to have a level playing field with the heavily subsidized fossil fuel industry.
So instead of cutting the subsidies to polluting tech, we increase it for the next generation. Fusion and fission are both heavily subsidized as well. Meanwhile the PTC for wind has expired, and it is competing against unfairly subsidized incumbents.
Besides the obvious tax burden, this has a nasty counter-productive effect: cheaper energy makes it harder for energy-efficiency to be taken as seriously as it should. Subsidizing production makes us all wasteful.
Better we stop subsidizing all this energy production and let the markets take care of it. We might find that under a truly capitalist system we waste less and produce what we need far more efficiently than we do under our current socialist system- something the Russians learned after the fall of the Berlin wall.
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My bad, the formula in paragraph 2 should have read:
E=(1/2)(1000kg*100)(10m/s)^2 = 5e6 joules
The answer is the same; just a typo.
for each coal plant in the US one coal-miner is killed each year in an accident
Only 30 people died in Coal Mining Accidents last year. There are 1586 Electrical plants that use coal. That's one death for every 53 plants.
It only took about 1 min using google to find this data, next time please research your fantastic claims.
http://www.msha.gov/stats/charts/coaldaily.asp
A refrigerator is usually around 1000. That's a little less than 3 kWh a day, or 0.125 kWh (period... in an hour).
0.125 kWh per hour is equal to 0.125 kilowatts, or 12.5 Watts.
Over what period of time?
Oh my. "Watts" don't go over a period of time; the OP was perfectly fine.
zach
He's talking about the payback for his solar thermal system ( ~ 2,500) not a photovoltaic installation ( ~ 20,000).
Most of the electricity consumed by a UK house goes to heat the hot water tank and provide central heating so the biggest bang for buck is to do that using a solar/thermal system. The thermal vacuum tube systems are far more efficient at extracting energy from the sun than photovoltaics, up to 80% efficient and they are far far cheaper, nearly 1/10th the price.
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