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| comparing the performance of small wind turbines |
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How much power might a wind turbine produce? The graph below compares the published power outputs of a selection of small wind turbines available in the UK. The data shown here is drawn from the power curves published by the manufacturers. When we are able, we aim to carry out our own tests. If you have collected any calibrated output data, let us know!
The outputs towards the right of the graph represent gale force wind speeds, so the importance lies with the outputs around the much lower windspeeds you are likely typically experience at your potential site. This graph can't be used to predict actual annual outputs, since many other local factors will affect the performance of a turbine. See also:
comments (23)
Dorian Jones
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| I am looking for a wind turbine to run my small holding i have limited funds can anybody give me any suggestions. Cheers. |
Bob Mc Gregor
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| Is it true that you can get grants for seting up wind turbines from the goverment? |
Pete Shaw
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I have a Widsave turbine that took ages to get from Windsave and afetr loadsof modifications it was hit and miss, basically because it was not high enough. I have removed it from the building and mounted it i=on a free standing pole. It works a lot better. I also got one from Ebay! complete demo set inverter and turbine. Mounted this on apole too but cant get it to work, it should but does not, any one have any ideas or know anyone who can look (i can py of course) Pete |
steve
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| conventional wind turbines struggle with turbulent wind conditions described above, try looking at savonius wind turbines hope this helps |
Andrew Clark
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I am intrigued by the comments relating to assessing a site for windiness. I am glad to see I am not the only one who thinks average wind speed is not the be all and end all! I have had a Davis weather station with a roof-mounted anemometer at my house for about 5 years now (www.davisnet.com) . The wind data is logged according to a user-defined interval; it used to be every 10 minutes, but I recently changed this to 30 minutes as I was generating a huge amount of essentially useless data. The data is then downloaded to my PC, where it can be exported into a txt file. I get, for each interval period, average wind speed, high wind speed and "wind run". According to Davis, "Wind run is measurement of the "amount" of wind passing the station during a given period of time, expressed in either "miles of wind" or "kilometers of wind". WeatherLink calculates wind run by multiplying the average wind speed for each archive record by the archive interval. For Example: Average Wind Speed = 5 mph Archive Interval = 30 minutes (0.5 hours) Wind Run = 5 mph x 0.5 hours = 2.5 miles of wind Does anyone have any suggestions on how I can use this data to predict turbine output or even basic information such as the percentage of time spent above different threshold wind speeds eg 5m/s, 10m/s? I know I should be able to analyse this data in a way to get usefuk information from is - it's just knowing what information is the most useful! Thanks. |
toby @ better generation
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Hello Jon, Thanks for the note re: getting planning permission in an AONB. Planning aside, it sounds like a great spot for the turbine! I've emailed you separately about this, but in the meantime: RE: which model - some planning authorities make stipulations about colour (for example David Cameron's somewhat infamous rooftop wind turbine had to have grey blades), and acceptable noise levels (data on which is available from the manufacturers). In my view the most important first step is likely to be getting buy-in/support from local neighbours, village parish council etc. Its also helpful to prepare photo mock-ups of the likely visual impact, etc. We may be able to help you with some of this - please don't hesitate to drop me a line on the number below if you would like to discuss further. Cheers Toby @ better generation |
Jon
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| I have the perfect house for a wind turbine.... It faces due west, out to sea up on a hill with nothing in between but fields. There is, of course, a problem - the local council. North Cornnwall is an Area of Outstanding Natural Beauty. They don't think turbines are as beautiful as I do. Anyone have any comments as to how they would approach the planners? - and which model they would recommend for such a location? |
toby @ bettergeneration
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Hello Jackie, I'm afraid the yawing around that you describe is a common problem with any building-mounted turbine. The turbulence associated with being so close to any building means the wind swings around unpredictably - meaning the turbine spends a lot of its time searching for the wind rather than facing into it and spinning up, which is the only time any useful power is going to be generated. You are not alone in experiencing this problem, check out our reviews at ../wind-turbine-models/the-windsave-ws1000.html Some dissatified Windsave customers we've spoken to are considering moving their machines to a free standing tower to improve performance and getting into 'cleaner' air (Windsave Ltd will void your warranty if you do this, but in my opinion you've not got a lot to lose). If you're interested in this, drop us a line - we may be able to help. Meanwhile, we've heard that Windsave are working on a Mk2 version of their system. There's certainly a lot of room for improvement - but in our opinion any building-mounted turbine is asking for trouble (and reduced performance). Watch this space for updates. Cheers Toby @ better generation |
Jackie Smith
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| We purchased a Windsave domestic turbine in April 07. It is attached to the side of our detached house which is quite tall and set in 3/4 of an acre. Although there was not a lot of wind the first two weeks its a pretty windy area and has been reasonable windy since verying from 7 miles per hour to 17 miles per hour which is todays forecast. Our power level is only at 00006.4 today and seems to be going up at the rate of 00000.1 a day. We think either it is not working properly, or it is quite near to a chimney and slightly lower that the chimney. The windmill often just spins round and round and the fins remain still, with an occasional burst of activity. Would this posistion affect the performance that much? Windsave seem very slow in responding to the problem. |
Michael Taylor
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| I own a business here in Flint, MI USA and want to use a wind turbine to supply energy needs for outside security lighting and surveillance cameras. From my initial readings, small turbines like the Ampair 300 (?) or along those lines, would be suffice. Again, I'm a novice looking for energy supplement at this time. We are thinking a small turbing on a pole should be suffice. Any comments, suggestions, direction is welcomed on here or to our company e-mail at recoveryamerica@aol.com. We are always looking at nominal cost cutting options with one time "x" dollars cost up front. Thank you in advance. Michael Taylor, Recovery America, Inc. Flint, MI USA |
toby @ better generation
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Hi Jenks, Thanks for the note. Turbines mounted close to, or particularly on buildings will suffer much reduced performance because of the turbulence and interference to the flow of the wind. B&Q are rightly criticised on this site and elsewhere for their publicity showing a Windsave turbine seemingly mounted even below a house roof line - where it will be next to useless. Pole mounting in clean air away from obstructions is the way to go. In general, the Dti data will significantly over-estimate average wind speeds for urban areas, but is more closer to the truth in open, rural areas. The only real way to know is to take your own wind speed measurements - we sell low cost anemometers for that reason! We are also working on wind turbine comparison and payback function for this site which we will be releasing soon (free of course!) |
jenks
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I'm an MSc student, and I've been doing a bit of literature research on this subject in connection with my thesis. I'm a little dubious of some of the claims made by the manufacturers of these turbines. I''ve contacted several of the manufacturers listed here to get details of their power curves, and have been told they're not available / commercially sensitive - so I'm pleasantly surprised to see them in your graph. Funnily enough, the manufacturers of larger turbines, that operate in a more competitive market, are more than happy to give me their power curve figures. A lot of the advertising for these things shows them mounted quite close to the roof of the building they are attached to. Does anyone know how the wind speeds at this level compare to the listed wind speeds on the dti website that most firms use to estimate site suitability? |
Phil
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The amount of power that can be extracted from the wind varies as the cube of the windspeed. Hence a wind turbine capable of producing 1 kW a 12m/s will only produce about 70 a 5 m/s (i.e. 5*5*5/12*12*12 = 125/1728 * 1 kw). Your graphs illustrate this relationship very well. It does also follow that one cannot calculate the amount of energy one can 'harvest' from the wind by using the average wind speed for a particular location. One really needs a wind distribution so one can appley the 'cube rule' to it. Most of the wind turbines have a 'brake' on them to limit the maxixmum speed so one would have to take that factor into account as well. Another factor affecting the ampount of wind power harvested is the area of the wind 'captured'. This varies as the square of the lenght of the rotor blade. (pi R squared is the area of the circle.) So very large turbines in very windy places would seem to be the best bet. |
skoff
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Scratch that last grumble - the site loads fine now. Great idea - I'd been looking around to compare turbines in the uk (along with other alternative sources) and it's useful to have this on the one site. |
toby @ better generation
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Matt, Thanks for the comment. The information below comes directly from the designer of the FuturEnergy turbines, in response to your post: The rotor diameter is 1.8m, which has considerably more swept area than a 5 foot one [we will add better specs soon to the website] The PMG (or alternator as you refer to it as) is a bespoke 3-phase low RPM design, manufactured uniquely for FuturEnergy turbines. FuturEnergy do not intend to release any technical data (since the only people who'd want it would be the competition!). If you do the calculations, at 14m/s, these turbines are producing much less power than the Betz limit allows, so are able to operate at lower RPMs while still achieving good efficiency and performance. The furling mechanism uses a gravity activated pivoted tail fin, which simply turns the turbine "out of" the wind in speeds above 14m/s. Off load, the turbine spins up to 1000RPM before furling, so can be operated in this mode if required during fault conditions of attached equipment. Even the smallest of turbines can produce massive power levels in very high wind speeds, since the power available is related to the cube of the wind speed. The designers have tested one of these turbines to 2.8KW in much higher wind speeds, by changing the point at which the turbine furls out of the wind. The absolute maximum power extracted from an FuturEnergy 48V has been 3.2KW during early testing by the designers, very high wind speeds, at which point the PMG blew - so your assumptions of a 1.5KW maximum limit is incorrect. |
Matt Tritt
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Of course it's difficult to say from the photograph on your site, and since I cannot find any reference to actual technical specifications of the rotor and alternator, I'm going to take a wild guess and comment that the diameter of your machine appers to be about 5 feet; is that correct? Assuming that it is substantially the case, how can you squeek so much power from such a small rotor without an extremely high speed, say around 1200 RPM? Or even higher? I'm also assuming that you are governing the rotor speed much in the same way the Kestrel 600 and The AmpAir do, by using the "wake effect" of the accumulated blades to lessen the potential lift from the individual blades. What other methods are employed (besides loading of course) to ensure that the turbine doesn't run away in extreme winds and under no load? I think I'll go one further and say that I find it highly unlikely that extracting 1.5 kW from this machine is probable under virtually any conditions. I'm guessing that this is more likely a 500 to 700 Watt machine under real world conditions. Do you agree or disagree? (I also will add that I've been in the wind turbine business for 27 years here in the States, so feel free to point out the error in my thinking) |
toby @ better generation
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Nick, Agreed that at the moment, there is certainly a real lack of real-life performance data. Hopefully this will change over the next year, with projects such as http://www.warwickwindtrials.org.uk/ getting underway... |
nick
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| Has ANYONE got ANY reliable and independant data for the outputs of these turbines? Exprapolation from manufacturers spec is speculation -not real. Bench outputs have no bearing on system delivery. I have been told by the operators of several systems featuring different turbines that they have virtually zero useful outputs, I would really like to hear about about a well fuctioning system that has been monitored properly and has accurate data! |
toby @ better generation
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| Mike - the FuturEnergy output graph is correct for a 48V battery-charging setup. However, as you say, using two of the 500W windmaster grid tie inverters would cap the output at 1kW. However, whilst you could connect a third inverter, you would only be using it very occasionally, perhaps 1-2% of the time, in high winds, so buying a third one doesn't make sense financially. |
Mike
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| How can Futureenergy claim an output of more than 1.4kW when only 2 0.5kW inverters can be fitted? Is this statement from bettergeneration incorrect and you can fit 3 taking the inverter capability up to 1.5kW? I am on a very windy rural site so this increased output is of interest. |
David Hill (MHT)
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We are increasingly worried about the performance of small WT. As part of a Low carbon development (345 homes) in Upton Northampton we are testing 5 small VAWT and HAWT turbines from Japan, China and Britian. We will be publishing our results in May 2007. We will then purchase 58 WT for installation and offer more for purchase to our other on site residents and staff. |
Henry Hall
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Steve, I was referring only to the efficiency of conversion of wind energy to electrical energy. I agree with your second paragraph, but energy efficiency is not entirely irrelevant because an inefficient turbine has to be bigger and heavier for a given electrical output. |
Steve Macken
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Henry - don't confuse Betz limit with capacity factor, nor capacity factor with efficiency. Betz limit relates to the conversion of kinetic energy of air to electrical or mechanical output of a wind turbine, whereas capacity factor is the average of the actual output expressed as a fraction of the rated potential output. Efficiency is a term used to express the energy output of a conversion system (eg internal combustion engine) as a fraction of the energy input (eg calorific value of gasoline). Where wind turbines are concerned, the efficiency is arguably irrelevant as the fuel is free and non-polluting. The key factor in assessing wind turbines is their energy performance on a given site per unit cost of installation and operating. For domestic turbines this is a useful factor as it allows comparisons to be made with other micro-renewables such as solar PV. |
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