My local bike shop used to be Ben Cooper's Kinetics near Glasgow. They sell a lot of electric-assist bicycles, mostly with Heinzmann motors.
For a while they stocked cheaper units, but started getting them back really quickly. Ben showed me the drive gears from these Chinese motors; they were soft metal, and had worn out in a couple of hundred miles.
Heinzmann make a range of motors, from low power, long range to high performance short duration units. Check which of these (if any) are road legal in your area.
I don't know of any windfarms that are 'dispatchable' -- in other words, can get turned on or off by central grid control. Since you can never predict when that power would be there, we always just feed into the grid when we can. Someone can use it, even if it's just reducing the output of a peaking generator, such as coal.
Why are wind turbines dangerous to speed boats? If you can't navigate around them, you shouldn't be out there.
If the wind's above 8m/s, you'll hear wind noise, rather than turbine noise. And speed boats are hardly concomitant to "a quiet time out on the water".
While your analysis of the bird situation's pretty good, we don't ever "drop the clutch" on a grid-connected wind turbine. If there's enough wind for it to be running in, it runs, as there's always someone on the grid who can use the power.
So the trick is not to build wind turbines in migration routes. It's not rocket science, and is something that's required to be checked when you plan a wind farm now.
Altamont's an old design, using old turbines that we wouldn't use now, which have lattice towers that birds can perch on.
Short answer: You should be able to live 500m away, and it shouldn't disturb you. You might hear it, but it wouldn't keep you awake.
Long answer: Assuming a sound power level of 104dBA (wait, don't freak out yet; it's not what you're probably thinking) at a wind speed of 6m/s, and hemispherical propagation of sound, with a sound absorption coefficient of 0.005dBA/m, the sound pressure level at 480m from the turbine would be 40dBA.
RePower haven't published noise specifications yet. I'm guessing that it would be around that level, which is at the upper end of the wind turbine noise field. You don't need to be particularly quiet for an offshore turbine. You do if you're siting turbines in populated rural areas, as I am.
You've probably heard that the noise level of a pneumatic hammer is about 100dB. So does this machine make the same level of noise as a jackhammer? No, for what we hear is the sound pressure level, and the sound power level is a theoretical level that extrapolates the measured sound pressure level back to the source, as if it were a point source.
40dBA is about the noise level in a quiet living room. In Ontario, we design wind farms such that the noise level at 6m/s never exceeds 40dBA, at 7m.s 43dBA, and at 8m.s, 45dBA. Above 8m/s, the noise of the wind is over 45dBA, so the turbine is less noticeable. But at 6m/s, there is little wind noise, but the turbine is running, so it's kind of a critical value. In rural areas, the background noise level can be very low, too, so we have to be extra careful.
There's a good paper, Wind Turbine Noise Issues, that explains the issues very well. I still hate doing decibel mathematics, though.
(The A at the end of measured dB values just indicates what weighted scale has been used. There are A, B, C and G scales, with A being the one most suited to human annoyance noise level monitoring. The human ear doesn't react to all frequencies identically, so the A-weighted scale is a fair approximation of how we experience sound.)
There's a problem with having a streamlined tower: the nacelle and blades yaw around the tower as they follow the wind. So the best tower design is round, as the wind can come from anywhere.
Part of the problem of earlier designs was that they had blades downwind of the tower. That meant that the blades were operating in turbulent air, which tends to be noisier.
(That's not to say that downwind designs are totally without merit. The designs from Proven Engineering in Scotland are remarkable.)
The wake of a wind turbine is mostly dissipated 8 diameters downwind of a wind turbine; that's the parameter I use in designing wind farms. Betz's law says that you can only convert less than 16/27 (or 59%) of the kinetic energy in the wind to mechanical energy using a wind turbine. So, at most, a sailing boat near a wind turbine might notice the wind slightly reduced in the area, but not a dead calm.
(Oh, and before anyone pipes up with the "wind turbines aren't efficient" thing, I'd refer you to the Carnot Efficiency of a heat engine. The typical thermal efficiency of a steam plant is around 40%, the total efficiency of a typical wind turbine about 35%. They're comparable, especially when you consider you don't have to go digging for wind's fuel.)
The typical domestic installation tends to use a 1-1.5kW rated turbine, perhaps in addition to some solar panels. To get an idea of the scale of such a machine, please see the pictures of Steve Mann's Urbine, also featured in the Wikipedia entry for "wind turbine". (Pay no attention to the guy in the back of the photo in the dark blue shirt, for it is I.)
Your wind resource depends a lot on where you are. Roofs of buildings tend to be very sheltered, and not quite the most efficient place to put a wind turbine. Solar -- in both its photovoltaic and hot-water-heating modes -- is probably a better bet for most domestic roof installations.
If you want to find out more about this, I can't recommend Home Power magazine highly enough. There's also a good crowd on energy nerds who hang out at Talk Energy who might be able to help.
The way to make wind turbines safer for birds is -- to study where migration paths are, and not to put wind turbines there.
Any kind of cage around the blades wouldn't be very feasible. This machine is 126m in diameter, so the structure would have to be massive, and would seriously impede the wind flow.
WindShare did a bird study for their turbine on the Toronto lakeshore. It seems that the 750kW, 52m diameter machine there might kill two birds per year. The front window of my house does about that, too, and it's an unremarkable suburban semi.
Reharding energy payback, the Danish Wind Energy association says: "Under normal wind conditions it takes between two and three months for a turbine to recover all of the energy involved". There's more information on their Energy Payback Period for Wind Turbines FAQ page.
As regards taking energy out of the wind, the atmosphere's about 11km high, and the wind profile goes up from zero at ground level to pretty fast up in the jetstream. A turbine's wake is mostly dissipated at about 8 turbine diameters downwind, too. So even a wind turbine of this size might only affect less than 1% of the total atmosphere's height, for less than a kilometre horizontally.
'sokay, I've got family there. Shall I order a few to resell here in Canada?
Eee, I remember listening to the original series on BBC Radio4 *long wave*.
I didn't quote, 'cos I'm old fashioned, and kind of expect interested parties to follow links. Since wind energy's my profession, I try not to do dumb links about it.
I'd be happy to forward anyone the file I just got from Al from Gmail: scruss is my addy there.
Plus I've mirrored it here, with the author's permission: http://s108450040.onlinehome.us/savingenergy.pdf.z ip. Al asks that I should "let your mirror users know that substantive comments (that is,
science based as opposed to political ranting) also welcomed."
Places don't have to be very windy to make wind energy viable. Here in Ontario, we have investors falling over themselves to bid for wind energy electrical supply contracts. And we have some of the lowest electricity prices in North America, coupled with only marginal winds.
Designing wind farms is what I do. Call me biased, but I may also know what I'm talking about.
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For a while they stocked cheaper units, but started getting them back really quickly. Ben showed me the drive gears from these Chinese motors; they were soft metal, and had worn out in a couple of hundred miles.
Heinzmann make a range of motors, from low power, long range to high performance short duration units. Check which of these (if any) are road legal in your area.
Oops; should have said: we design wind farms such that the noise level at 6m/s never exceeds 40dBA at nearby houses .
I don't know of any windfarms that are 'dispatchable' -- in other words, can get turned on or off by central grid control. Since you can never predict when that power would be there, we always just feed into the grid when we can. Someone can use it, even if it's just reducing the output of a peaking generator, such as coal.
If the wind's above 8m/s, you'll hear wind noise, rather than turbine noise. And speed boats are hardly concomitant to "a quiet time out on the water".
I would say that at least two thirds of the results returned by googling those words are sensationalist rehashes of the same misinformation. Well-researched sources of information include: Advice from an Expert - Putting Wind's Impact on Birds in Perspective, What Kills Birds?, and the single-site-specific Impact of the CNE Wind Turbine on Bird Populations.
While your analysis of the bird situation's pretty good, we don't ever "drop the clutch" on a grid-connected wind turbine. If there's enough wind for it to be running in, it runs, as there's always someone on the grid who can use the power.
Altamont's an old design, using old turbines that we wouldn't use now, which have lattice towers that birds can perch on.
Short answer: You should be able to live 500m away, and it shouldn't disturb you. You might hear it, but it wouldn't keep you awake.
Long answer: Assuming a sound power level of 104dBA (wait, don't freak out yet; it's not what you're probably thinking) at a wind speed of 6m/s, and hemispherical propagation of sound, with a sound absorption coefficient of 0.005dBA/m, the sound pressure level at 480m from the turbine would be 40dBA.
RePower haven't published noise specifications yet. I'm guessing that it would be around that level, which is at the upper end of the wind turbine noise field. You don't need to be particularly quiet for an offshore turbine. You do if you're siting turbines in populated rural areas, as I am.
You've probably heard that the noise level of a pneumatic hammer is about 100dB. So does this machine make the same level of noise as a jackhammer? No, for what we hear is the sound pressure level, and the sound power level is a theoretical level that extrapolates the measured sound pressure level back to the source, as if it were a point source.
40dBA is about the noise level in a quiet living room. In Ontario, we design wind farms such that the noise level at 6m/s never exceeds 40dBA, at 7m.s 43dBA, and at 8m.s, 45dBA. Above 8m/s, the noise of the wind is over 45dBA, so the turbine is less noticeable. But at 6m/s, there is little wind noise, but the turbine is running, so it's kind of a critical value. In rural areas, the background noise level can be very low, too, so we have to be extra careful.
There's a good paper, Wind Turbine Noise Issues, that explains the issues very well. I still hate doing decibel mathematics, though.
(The A at the end of measured dB values just indicates what weighted scale has been used. There are A, B, C and G scales, with A being the one most suited to human annoyance noise level monitoring. The human ear doesn't react to all frequencies identically, so the A-weighted scale is a fair approximation of how we experience sound.)
Part of the problem of earlier designs was that they had blades downwind of the tower. That meant that the blades were operating in turbulent air, which tends to be noisier.
(That's not to say that downwind designs are totally without merit. The designs from Proven Engineering in Scotland are remarkable.)
Ten years ago, we weren't as good at the acoustic design of wind farms. Mistakes, I'm afraid, were made, and turbines were put too close to houses.
Audible, yes; annoying? Depends. What is it like in residential areas? This movie was recorded in the middle of a corn field.
No, that's about what I'd expect. Wind turbines tend to have a coefficient of performance around 33-35%.
(Oh, and before anyone pipes up with the "wind turbines aren't efficient" thing, I'd refer you to the Carnot Efficiency of a heat engine. The typical thermal efficiency of a steam plant is around 40%, the total efficiency of a typical wind turbine about 35%. They're comparable, especially when you consider you don't have to go digging for wind's fuel.)
Your wind resource depends a lot on where you are. Roofs of buildings tend to be very sheltered, and not quite the most efficient place to put a wind turbine. Solar -- in both its photovoltaic and hot-water-heating modes -- is probably a better bet for most domestic roof installations.
If you want to find out more about this, I can't recommend Home Power magazine highly enough. There's also a good crowd on energy nerds who hang out at Talk Energy who might be able to help.
Any kind of cage around the blades wouldn't be very feasible. This machine is 126m in diameter, so the structure would have to be massive, and would seriously impede the wind flow.
WindShare did a bird study for their turbine on the Toronto lakeshore. It seems that the 750kW, 52m diameter machine there might kill two birds per year. The front window of my house does about that, too, and it's an unremarkable suburban semi.
Buildings, cars and cats kill more than wind turbines. The unfortunate case of Altamont is not representative of the industry.
As regards taking energy out of the wind, the atmosphere's about 11km high, and the wind profile goes up from zero at ground level to pretty fast up in the jetstream. A turbine's wake is mostly dissipated at about 8 turbine diameters downwind, too. So even a wind turbine of this size might only affect less than 1% of the total atmosphere's height, for less than a kilometre horizontally.
'sokay, I've got family there. Shall I order a few to resell here in Canada? Eee, I remember listening to the original series on BBC Radio4 *long wave*.
BBCShop only ships to the UK and EU; elsewhere, we're SOL. The site does offer the usual raft of countries, though, which is dumb.
http://talkenergy.com/ is a Slash-based forum dedicated to energy and environment issues. It really could use more posters right now ...
What for they name it after Scotland's longest and most dangerous major road, the A9, which stretches from Perth to Scrabster?
"Atomkraft? Nej Tak", as they used to say in Denmark.
I didn't quote, 'cos I'm old fashioned, and kind of expect interested parties to follow links. Since wind energy's my profession, I try not to do dumb links about it.
Plus I've mirrored it here, with the author's permission: http://s108450040.onlinehome.us/savingenergy.pdf.z ip. Al asks that I should "let your mirror users know that substantive comments (that is,
science based as opposed to political ranting) also welcomed."
Designing wind farms is what I do. Call me biased, but I may also know what I'm talking about.
No, it doesn't. Buildings, cars and cats kill more than wind turbines. The unfortunate case of Altamont is not representative of the industry.