http://scruss.com/blog/2004/05/09/windsave-again/

Windsave, again
Anent my previous rant about Windsave claiming impossible efficiencies, they’ve made some changes to their website. The machines now have larger diameters (1250 and 1750 mm — up from 1000 and 1400mm), and much lower rated power (500W and 1000W at 27mph — down from 750 and 1200).

Plugging in those numbers to Cp = P / ( 0.48106 d2 v3 ), we get more realistic efficiencies of 0.378 and 0.386 (for the small and large machines, respectively).

The Lakota turbine we installed last week has a nominal rated power of 900W at 28.8 mph for a 2.09m diameter rotor. It has a very conservative Cp = 0.20, although David Cooke says that typically they see 1,000 Watts at around 25mph (a Cp of around 0.34).

At the other end of the scale, the Lagerwey LW52 is a 51.5m diameter machine rated at 750kW at 12ms-1. This advanced utility scale, variable pitch machine has a Cp = 0.34.

Windsave’s revised figures are much more credible, but until we have real figures backed by a few years of installations, there’s little more we can say about them. I’m a little concerned that, although there are claims that 1000s of these machines have been sold, there’s not a single real photo of one on the web.

I’m going to enjoy putting up an anemometer and logging system alongside the urbine downtown. We’ll see how it runs.


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Tags: betz, lagerwey, lakota, rant, urbine, wind, windsave

This entry was posted on Sunday, May 9th, 2004 at 21:33 and is filed under Wind Things. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

114 Responses to “Windsave, again”
« Older Comments Clivey says:
3 Nov 02007 at 16:00
Hi – although I’m now aiming to sell small wind generators online for such things as canal boats I think to compete with the national grid, consider solar electric or better still, solar hot water – still very expensive (solar PV that is), my Windsave is still going, but it hasn’t done anything as much as our solar heating and solar electric.

Best form of domestic renewable energy is solar hot water I think.

Cheers, Clive

CG says:
9 Nov 02007 at 07:15
Would you buy a wind turbine from somebody who was a mug enough to buy a Windsave turbine?
clett says:
12 Nov 02007 at 13:06
I see that the Swift turbines are back in action on the roof of the Wick Tesco. Outward appearances suggest they are going around at least! Any ideas who we can ask to find out if they’re making any power?
RalphVanF says:
24 Dec 02007 at 13:24
Scruss

I was particularly interested in Audrey’s comment of 9 Jan 07 and your reply to that post. I have been taking anemometer readings at the top of my block of flats for a couple of weeks now (a site strongly recommended as “ideal” by the Windsave survey man). It is roughly 15m high, some way higher than any neighbouring buildings/trees etc., clear facing views in every direction and particularly the South West, with a solid brick “shed” on top to mount a potential turbine – the anemometer is currently attached to it, recording roughly 1m or so above the top.

The readings indicate that the windspeed varies between 0 and 14m/s, frequently over 5m/s on certain days although very rarely averaging over 5m/s over any 10 minute interval. Does this wide variation indicate the gusting and/or turbulence that is referred to by detractors here (or am I conflating two dinstinct issues)? If this is indicative of turbulent wind, is it in fact a problem for horizontal axis machines – you state on your post re VAWTs that “While it’s true that vertical axis wind turbines can capture energy from the wind in any direction, this is less of an issue in reality than you might think.” In any case, the readings do seem too low to bother putting an expensive, dysfunctional turbine up.

Based on feedback on this blog, there seem to be plenty of reasons not to buy a Windsave even if there is such a thing as a suitable urban location for it: cheap materials prone to breaking down, unresponsive company etc. It also seems reasonable to infer that any alternative roof-mounted horizontal axis devices – if any is even available in the UK – is unlikely to be any better in any sub-/urban location (I find it hard to believe there would be many better sites than where I live). And VAWTs don’t seem to cut the mustard either for reasons of poor efficiency. In summary, there really is no suitable urban roof-mounted location for any device, and is unlikely to be: is that a fair appraisal?

Clive says:
18 Jan 02008 at 14:37
Yes it does ‘wobble and sway a lot’ so I’ve made a few mods, I’ve made a simple ‘friction brake’ to the yaw bearing by wrapping cloth around the rotating stem, and Gaffer taping it in place, this has made a huge difference! I’ve also put a back stop on the tali so it can only swing the correct direction when it furls, yes the tail is too small for turbulent ‘roof top’ conditions on its own. Yes it spins around at a rate of knots at times, but alas the generator has to reach 200 volts before the electronics kick in, so in the last year, it has only produced about £10 worth of power, my solar hot water system (2 x 20 tube Navitron solar collectors) has been MUCH more successful. I believe that domestid wind power can work, but I wouldn’t reccommend it unless you are well exposed to the wind. If you like wind power, invest in a community owned turbine! check out the Westmill and energy4all websites. Clive )
CG says:
21 Jan 02008 at 05:09
Clive, thanks for the update, I only wish more Windsave owners would do the same. I reckon you have probably broken your maintainance contract with Windsave by playing about with the yaw bearing, but you only have about one more free year to go on it. If you can find someone to maintain it for about £9-50p when it runs out you will show a little profit.

We have a Windsave turbine here in Cromer on the coastal road, and it spins around the yaw bearing almost as much as the blades go round, and the tail wags like a happy puppy. It’s on a garage, which is probalby the safest place out of its box you can put one.

The reason Windsave will not correct these faults is the same as why we haven’t seen a house save 30% of its electricity bill yet; the whole Windsave system is so cheap, that prolonged generating in a high wind would cut the life of it to almost a few weeks. This is why the company will not sell it as a battery charging system. If they did that, then people in, say, the Falkland islands or Orkney would buy them and burn them out in a couple of months.

To think Gordon the Incredible Sulk Brown is still giving money to people buying these crappy things. What a way to spend the country’s money on renewable energy.

And has anyone noticed the the new Windsay 1200 is really the Windsave 1000 without its rate wind speed published? It has the same size blades on the same size generator, with only the cut off windspeed, which is higher than the rated wind speed, being published. I really think there is a case of mis-selling to be answered here. It costs about £500 more – some of that will be your taxes.

steve says:
26 Feb 02008 at 16:10
well i do know quite a bit about the windsave system. the motor is efficient but there grid inverter is about 46% efficient last time i checked, i have a similar motor 6 blades bought from ebay, i mounted the turbine on a recycled lamp post, the motor (same as windsave but with six blades) generates between 100v to 560v no load, i am ordering a windy boy inverter as they are 92% efficient . lasted through the gales so far defo would not want it on side of house ! as i say the motor is the same as windsaves so if you want any other readings let me know
clett says:
4 Apr 02008 at 10:58
Any updates Steve? How many kWh per month?
Rogerborg says:
3 Jun 02008 at 07:43
Hang on, he needs another few months to charge his laptop battery up so that he can reply.
CG says:
13 Oct 02008 at 05:19
Scruss,

We are still here, just waiting for the Windsave users to tell us how much money they are saving with their green toy.

Dave says:
14 Dec 02008 at 13:26
Hi, I have a windsave system which is now exactly 2 years old.
To date it has had 4 inverters and worked itself loose from the
house once. From the day of installation the system has been
fitted with a northern design class one energy measuring meter.
Readings taken are as follows for the two year period.
Power taken by inverter 10.26watts, total=104.82kwhrs,
Power produced by inverter, 446.96kvahrs—249.17kwhrs,
This works out @ a power factor of PF 0.5575 poor to say the
least. So if we take the power produced minus the power
consumed we get 144.35kwhrs nett for the two years the turbine
has been in use. Divide this by 2 we have the average for one year
72.175kwhrs,with the cost of electrcity about 10p per unit this works
out to be a saving of £7.22 a year.
At to days prices pay back should take, wait for it
£1500 divided by £7.22=208YEARS.
Does it work ,is it worth the money? Make your own mind up,
Maybe a turbine in the North sea with a long cable back to your land
based home might be a better setup!
CG says:
17 Dec 02008 at 05:40
Dave,

Thanks for the info, I wish we could get more of it from other users. Has your maintainance guaranty with Windsave run out yet? It shouldn’t have, considering the problems you have had with the machine, but if it has, have you bothered to get a price for a new one?

martin smith says:
27 Jan 02009 at 07:59
Do you have enough wind on site for a generator? An easy way to check is to look at the trees on a quiet day. If they are not leaning permanently away from the prevailing wind, forget it.
Girona Airport says:
8 Aug 02009 at 08:12
i think , turbine in the North sea with a long cable back home is not a viable solution beacuse of two reason who will take care of the setup at sea ,anyone can finger it and what will be the solution if a fault occurs in the long cable and as far as wind generation is concerned then i think you should get help from your local weather department in order to get the conditions of whole year or coming years.its quite possible that for certain season wind can be a good option but for other season it may not be.So a Hybrid approach can be a solution but it will mainly depend upon your budget.So put more effort in planning it will help u at later stages.
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