B&Q to stock chocolate teapots!

[Stonehead]

Vibration - Is an issue but I think that this can be got around with good mechanical design of the mount which I assume Windsave have done.

I'm not convinced!

If FuturEnergy says of its 1kw Upwind turbine "We don’t recommend, nor will we authorise the installation of any of our turbines in ‘building-mounted’ installations, other than for steel-framed and other industrial buildings. These turbines are tower-top ready...", then how can Windsave be the only company with miracle mounts?

As for the rest, I completely agree.

I would advise Martin not to waste any more time posting on this subject (as I have done writing this post).

That's why I've refrained from posting again, too. I've made my views clear, am happy to provide more detail via PMs, but to post more publicly only encourages the marketeers and salesmen to deluge forums like this with their propaganda.

[nathanbriggs]

In regards to the inverter, can you please tell me what its cut is. If the turbine is generating 1 kw at 12.5 m/s, is that what goes into the inverter or what comes out?

On other boards it seems like the inverter is the most interesting thing, certainly not the bog-standard-over-hyped-turbine.

At 12.5m/s the inverter is over 92% efficient (again commercially sensitive) but it's the output which is 1kW at 12.5m/s. However since I am truthful I will say that I have seen 980W at 12.5m/s in a windtunnel and this has been rounded up by the marketeers.

Part of the problem here is that "12.5m/s" is all very well in a wind tunnel where speed can be made (reasonably) constant but that is nothing like the real wind which is sampled over time. The only current "standard" sampling technique is over 1 minute (for big turbines) and 12.5m/s for one minute would either be (a) freakishly consistent wind or (b) a series of VERY big custs probably up to 30m/s and back down to 8 or 10m/s

Sometimes I look at our competitors numbers and think where can they get that power it's more than the betz limit? But the answer is that pretty much anyone can use what measurement technique suits them, and very few small companies can afford to hire a huge wind tunnel even for a day.

To be fair I know a number of our competitors say the same thing about Windsave's numbers. Which is why we've had them independantly verified by TUVNEL the National Engineering Laboratory.

[nathanbriggs]

LASTLY

It appears I am guilty of propoganda, which I was trying to avoid, I apologise if anyone feels I was selling a product. I came here to defend a project I have worked on for 2 years and I leave it up to you to decide wether you're convinced.

I too have NO problems with Martin or any of the other naysayers, what I've been trying to say is, nobody KNOWS everyone has an opinion.

Windsave does have data for the windspeed/turbulence at roof top level but it is our own, what we need is external verification, would you really believe our numbers??

I am sure I will be around in selfsufficientish, it's a good forum and I've learnt a lot, but from now on I will try and restrict myself to direct answers to questions

[welshphil]

Hi Nathan and others on the forum,

So your turbines power curve is based upon wind tunnel testing.........????

I think this is another example of the naivety and / ignorance of windsave. Nathan, with all due respect, I am sure that your inverters and electrics are top notch, but your company should have invested more money on mechanical engineering rather than the marketing hype.

Wind tunnel testing of wind turbines is useless. It is like saying ' my car will do 100 miles per gallon...........on a treadmill'.
It bears no resemblance or relevance to the real world application of the product.

Wind tunnels by very definition are pressurised systems. The real world is not.
For the benefit of others here, the betz limit means that you can only extract 59% of the kinetic energy from the wind. To extract 100% of the kinetic energy you would have to reduce the wind speed to zero as it travels through the turbine rotor. Of course, if you do that, no more wind can pass through the rotor because you have this big bubble of stationary air in the way!

In a wind tunnel, a great big fan sucks the air through the turbine so the betz limit is negated. In the real world, the airflow takes the path of least resistance, which is frequently around the turbine - and not through it. Its a little more detailed than that, but its a brief explanation. The key thing is that a turbine will perform up to 60% better in a wind tunnel, than it will in the real world.

Wind tunnel testing of reputable turbines has not been done for many many years now as it has been well proven to be incorrect. I have a copy of British Standard 61400-12: Performance Testing of small wind turbines. No where does the approved british standard mention wind tunnels!

I am not a naysayer. I would love something like this to work, so I could wholeheartedly recommend it to people. Unfortunately the concept is fundamentally flawed, and it is more and more obvious that Windsave's engineering theories are also incorrect.

We can argue about turbine theory until the cows come home. The proof is in the pudding, so I ask again, please can you show me 10 case studies of successful Windsave installations (that meet your claims). Surely this can't be so hard, you are obviously really confident in your product and a recent interview with David Gordon said that you have 1000's of units in the field.
I'm only asking you to prove that your product works. I don't want your roof-top windspeed data or anything like that, please just give me 10 installations, their date of installation and how many Kwh's have been generated by at each installation. I will verify it simply by going and looking at the Kwh meters on the windsave inverters at each installation.

Phil

[welshphil]

.........and of course I will verify on the electricity bill.

[CG]

Nathan, you still haven't said if the turbine furls, and you should know you work for the company. If it doesn't furl, that tail will throw that half hundredweight generator and blades back in to the wind, cause it to swing from side to side. At a wind speed of 30m/s you will have over 50 hp blowing through it, would you really have something like this bolted to your house?

I know you are trying to be honest (keep you CV up to date, that is not a the Windsave ethic) but all inverter companies exaggerate, so I would recon we are looking at an average of less than 900watts at rated speed, even in the wind tunnel.

None of us anti-Windavers are nimbys, we would all love roof top turbines to be practical, but they a just not suitable. It is far better to have one 250kilowatt turbine on an industrial estate than to have 250 one kilowatt turbines on housing estates. Most people like the idea of electric cars but storage is the problem, and it was a bigger problem years ago when Clive Sinclair brought out the C5. Do you remember those silly sods sitting in those electric coffins with their heads level with the axles of heavy goods lorries? Well this is what the Windsave turbine is - a C5 up a pole, and people who buy it will be the laughing stock of their street when the truth about these turbines finally comes from the complaining mouths of those Windsave customers. You can't just hide this turbine in a draw and put it all down to experience, it's up a pole on your house for all to see, you might just as well walk around with "I'm an idiot" tattooed on you forehead.

This product is going to do the wind energy cause a lot of harm, it's just what the nimbys wanted.

[Stonehead]

It is far better to have one 250kilowatt turbine on an industrial estate than to have 250 one kilowatt turbines on housing estates.

Not to mention the materials used.

It would make more sense to have small wind farms just outside towns and villages to provide sufficient energy to make a reasonable contribution to local power consumption.

Obviously, if you scale up too far then you get the equally daft situation of huge wind farms in northern Scotland (or Wales etc) sending power south to England with all the losses along the way, plus the sizeable use of resources and energy to build the things and their distribution networks.

I suspect the real contribution to be made from micro-generation will come from some combination of solar and biomass CHP in colder countries (it makes sense to use household heating for power generation), and solar in hotter countries. People and communities that are lucky enough to have good water flows may also benefit from micro-hydro. That's not to say small-scale wind power won't be useful, especially outside built-up areas and provided the turbines are big enough, but it has its limits.

Oh, and on wind power has anyone heard anything about wind crofting, as being touted by Proven? I'd find it interesting to see their contracts and see if they're as open-ended as the ones used by the mobile phone companies, which allow unrestricted access across your land, future up-sizing without consultation or objections from the landowner, etc.

[Martin]

I agree about local turbines/wind farms - the transmission distance is less, and the economies of scale mean that medium to large turbines have the swiftest payback times. I'd heard of Proven's scheme before - there are many companies and private individuals who will pay farmers handsomely for the privilege of erecting a turbine on their land - I've seen realistic "pay back" calculations of 6-7 years for the larger turbines - it is incredibly attractive for investors!
I sell the things, and obviously am in business for profit, but especially in a low wind speed area like Sussex, there are very few suitable sites for domestic turbines - I've visited several large country properties recently, none of which were suitable (too many trees closeby). I too wish teapots worked, but in the meantime, we advise strongly against ANY urban wind turbines (unless you can get consent for about 100' of mast) - whether house or mast mounted! - if in doubt, invest about 150 quid in a good wireless weather station, and collect some data first!

[nathanbriggs]

To answer several posts
Yes the Windsave progressively furls from around 13m/s to around 22m/s
As previously stated the number of installs is one thing but the number of "household" installs and in particular urban rooftops is very small and very recent, so we don't have data to share.

The Wind tunnel testing was done in conjunction with NEL and pressure readings were taken to normalise back to the standard. Just FYI the 60% figure is for high pressure wind tunnels which this was not, the pressure was just a little higher than atmospheric so the "adjustment" was circa 5%.

I love the windcrofting idea, Proven's a great company with a proven track record their new 5kw(ish??) downwind design looks the business but seems a little noisy to me (I'm used to smaller turbines!)

I hope Windsave will do more good than you seem to think, only time will tell. I think the wind resource in the UK is good enough the the landscape should be dotted with windmills, but as one of the first very public windmill companies part of Windsave's main pourpose in my view is to change public perception. It is amazing how people's view of power changes when they start to measure it.

[welshphil]

Hi Nathan,

Thanks for your reply - You have been most gracious. Please understand that I am not targeting you personally and I totally understand your defence of the company.

My experience tells me that your wind tunnel tests are still inappropriate even if you have compensated, but I guess we will have to agree to disagree. Time will tell.

Do you have ANY casestudies of successful windsave installations (meeting the claims)?
They do not necesarily have to be residential (although that would be good as that is what you are currently aiming your marketing at).

Cheers,
Phill

[CG]

Nathan,

You're a bit vague on the furling, how does the turbine furl, does it use springs or gravity or something else? I can't see any furling mechanism on the turbine.

Yes, the UK has a lot of wind resourses, and tapping into it with your turbine is like getting oil out of a well with a teaspoon.

I think Proven will use their 15kw machine for wind crofting - more energy from a singe mast.

Windsave will certainly not further the cause of wind energy; it will do the opposite when the horror stories start coming in.

For those interested in urban turbines of a larger size, you might like to consider the Windstor project. I had hoped this turbine would be just right for urban power, but it has almost ended in farce. The first commercial installation at Ishpeming, Michigan, is back on course, but I have doubts of its success. The company behind it (Mckenzie Bay) are trying something like Proven's Windcrofting. But the whole project is being run with insuffient funds, which for US company is quite unusual.

[nathanbriggs]

The furl is achieved by using a tailfin offset from the centre line and with a slanting hinge, it's not my area of expertise but as I understand it it "balances" the force on the blades until above 13m/s and then the force on the blades is stronger turnong it out of the wind progressively.

I have a video of it in action I will ask if it can be released

[CG]

Nathan,

Many thanks, I would very much like to see the video of Windsave's furling action. I have to repeat that on their site they make no mention of furling to control the turbine; they only cite your inverter and some mechanical switch.

[CG]

Well, it's been a while and still no furling video from Nathan, not even a couple of still pictures. I really think that the Windsave turbine on sale at B&Q does not furl; go down to B&Q a give the tail a push, see if it folds bach - don't bother to ask the salesperson, they won't have a clue what you are talking about.

I would like to give my impressions a what this means for any buyer of this turbine.

The method of control stated on the Windsave site is through the inverter, and a mechanical switch ( whatever this second means may intail by way of operation I do not know ). In the case of the inverter I can speculate and Nathan can correct.

Windsave uses the term cut out, when the windspeed reaches 14m/s - not cut back or stabilisation, so I can only reason that tis means that the turbine stops generating electricity. Perhaps is uses the electricity to brake the turbine - driving with your foot on the eccellerator and brake at the same time. But it is more likely that the inverter just cuts out the generator, which is ok for stopping the generator burning out But it doesn't do much good for the bearings of the generator, as the braking effect of the act of generation is taken away and the blades will just go faster. This method of controlling a wind turbine is called a shut-down, and I would like to quote from Hugh Piggott's book, Windpower Workshop, on what he thinks of this method.

"Shut-down systems are comforting to have, but their use is an addmission of defeat, because a shut down windmill is a missed opportunity. It is bad enough that windmills will not work in calm weather; they ought to work full time in windy weather!"

If it is the case that this turbine stops generating useful power at 14m/s that is a mere 1.5m/s above its operating speed. So you wait ages for the windspeed to get up to high operating speed and 1.5m/s higher the system shuts down - and this system is going to cut your electric bill by 30%? I don't think so.

But if the turbine furled in increasing windspeeds the energy output could be controlled. As the blades yawed out of the ncreasing wind the variables in the Betz theorem would change; the second variable, the windspeed, would be increaing, but the first variable, the area swept by the blades would be decreasing, as the shape of the area swept would change from a circle to a decreasing ellipse. This method of control has been in use for years, and it works. So why haven't Windsave employed it?

I think cost is the answer, they had to get this product in under £1500 and every little helps. If they could control the turbine just by the inverter that is ok by them, because only the customer pays in lost energy production. Also springs and such used in furling need maintaining, and Windsave didn't want this added cost on their plate.

The deeper one looks into this product the shallower the promisses of its manfacturers appear.

[Martin]

a real turbine manufacturer will spend a considerable amount of time matching all the components, and designing for the best performance at all wind speeds - they will then test them to destruction in the real world to ensure that they can achieve what they claim.........
If you have the slightest doubt, I'd suggest hanging fire and watching the results from here - http://www.warwickwindtrials.org.uk/ - it's early days yet, but the first results published (from an anemometer placed on the roof of one of the properties in the test) - for two months the average speed was 1m/sec, for one month it was 1.9m/s - 4mph! At those speeds we are talking zero generation, and probably a net deficit, as the inverter draws a constant current, amounting to 53kw/h per annum!