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Author Topic: Ridge tile generators  (Read 34454 times)
guydewdney
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« Reply #15 on: November 15, 2012, 10:11:36 PM »

ok- 99% of the time this stuff is laughable - but heres a q


is there any merit in the deflt university 'pinch point' idea? two feet to the left, its obv v poor and behind the building its vvvvvv poor.

discuss
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rhys
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« Reply #16 on: November 15, 2012, 10:28:25 PM »

Not many roofs with a flat bit behind the front ridge. Wonder what it looks like with no flat bit.
How many roofs face directly into the prevailing wind. If not spot on like in a wind tunnel, there would also be turbulence in the third dimension, into the section shown?
dunno what does H Piggot say?
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guydewdney
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« Reply #17 on: November 15, 2012, 10:42:16 PM »

hugh isnt the god of all things wind - hes good, very good, but not the almighty... we should always challenge the accepted, or else fall into a trap of non advance.

I was told catagorically that you cant use a waterwheel for leccy production - yet here I am.
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rhys
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« Reply #18 on: November 15, 2012, 10:51:19 PM »

hugh isnt the god of all things wind - hes good, very good, but not the almighty... we should always challenge the accepted, or else fall into a trap of non advance.

I was told catagorically that you cant use a waterwheel for leccy production - yet here I am.
True  but as always it's for the new science or engineering to disprove the old, not con the gullible or silly investor.
with smoke and mirrors.
Don't know who said water wheels coundn't produce elec. Plenty of engineering and physics always said that was possible. Grin
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biff
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« Reply #19 on: November 15, 2012, 11:19:44 PM »

As far as I can remember,
                          I believe the origional inventer was an aussie and the barrell like structure was capable of putting out 1kw of each power and on one pic someone had his whole ridge lined with these spinning barrells.The guy won some award,,probely for ridge tile decorating and the yoke i things were supposed to sell like ot cakes. I could not help but wonder how one would feel inside the house during a force 6 never mind a proper storm,, hysteria
                                                                   Biff
                                   
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renewablejohn
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« Reply #20 on: November 16, 2012, 01:05:43 PM »

ok- 99% of the time this stuff is laughable - but heres a q


is there any merit in the deflt university 'pinch point' idea? two feet to the left, its obv v poor and behind the building its vvvvvv poor.

discuss

I am sure there is something in this pinch point just from my own observations. We used to have chicken houses on the farm  with a ventilation duct on the ridge every 3 mtrs. Just like a mini dutch barn located located above the ridge with an electric fan on the top. On still days the fan would be turned on to ventilate the chicken shed. All other days the fan would be turned off but it would still rotate  strongly and ventilate the chicken hut.
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camillitech
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« Reply #21 on: November 18, 2012, 01:19:03 PM »

I'm sure that if you had a roof shaped just like that, it was made from smooth material, built half a mile from any obstruction and the building had a good set of yaw rollers it would work just fine. Me I'd stick with Hugh's advice  hysteria  hysteria
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GavinA
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« Reply #22 on: November 24, 2012, 12:37:11 AM »

actually that does look like a design that could produce a fair amount of power. The total swept area is fairly big, and it's obviously designed to work with the roof so that the roof effectively funnels the wind up to the blades at the ridge, and the blades are designed to take the wind coming at them both from below and horizontally.

Whether it'll be cost effective or not is another question, and one that can't be answered without an idea on pricing, and how realistic the 3200kWh a year is.

My main query with it is about the noise level tbh 66db seems pretty loud to me for something that's going to be sat on your roof.
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rogeriko
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« Reply #23 on: November 24, 2012, 06:40:40 AM »

We all know that there are many forms of wind concentrators. How about one of these in your garden.

http://gigaom.com/cleantech/startup-green-energy-tech-installs-first-small-wind-concentrators/



* green-energy-turbine.jpg (19.45 KB, 472x316 - viewed 768 times.)
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martin
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« Reply #24 on: November 24, 2012, 08:47:12 AM »

Ducted and rooftop turbines are a nonsense - have a read of Paul Gipe for chapter and verse -

http://www.wind-works.org/articles/FantasyWindTurbines.html, and this section - "Inventions & Questionable Wind Turbines" on this page  - http://www.wind-works.org/articles/small_turbines.html

In the simplest of terms, there just isn't enough unturbulent wind over a roof to have meaningful amounts of power extracted  - sadly the subject is pretty complex, and it is easy for fantasists to bamboozle the general public with rash claims - every year or two these daft ideas resurface, and often people are potty enough to shell out investment in such scams (anyone remember the "dragon" wasting his investment in a chimney pot generator?")

« Last Edit: November 24, 2012, 08:52:04 AM by martin » Logged

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pdf27
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« Reply #25 on: November 24, 2012, 01:52:29 PM »

OK, let's put some numbers on this. Using the DECC wind speed database my annual wind speed at 10m above ground is ~5 m/sec. Kinetic energy is therefore ~ 0.5 x (1.22 x 1 x 1 x 5) x 5^2 W/m^2 or about 75 Watts per square metre. Being generous and saying that the pinch point effect (which will certainly happen to some extent) compensates for the boundary layer from the roof and you get somewhere near to free stream velocity, and assuming as a perfect turbine it can extract 16/27ths of the wind energy that's 45W/m^2. Throw in the various losses you'll expect and that's about 30 watts per square metre.

From the photos on the site, I'd say it has a swept area of about half a metre above the roof, and for my roof (8m long, facing into the prevailing winds) that's 4 m^2. 120 Watts, before you subtract off the 30% they give for not being steerable, and you get about 80 Watts.

There are 8766 hours in the average year (365.25 days), making predicted annual production where I am about 700 kWh. FIT (assuming they can get it - their website says they're having problems) is 21p/kWh, and being as it's a relatively low, steady production assume you'll use half of it at ~15p/kWh and export the rest at ~5p/kWh. That makes an annual income of 200.

So if they can get the cost below 2000 including installation, can get FITs and keep the noise down to ambient levels then it might actually make some sense - probably more if you can share infrastructure with a PV installation. Having said that, I'm sceptical on both their price and that it would achieve this measured performance - I've got a lot of open space on the upwind side of my house so would probably achieve the rated production. Those immediately downwind of me - or facing away from the prevailing wind - will not.
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martin
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« Reply #26 on: November 24, 2012, 02:09:24 PM »

Cobblers! - as I said "it isn't that simple, and many are bamboozled" - look at the figures on Hugh Piggotts website for actual windspeed over a roof.......... (think 1.5m/s if you're lucky, in an area that is otherwise over 6)
Or just hear it from the horses mouth as to how little power there is.........
<a href="http://www.youtube.com/v/WVo0WvuX7K0?version=3" target="_blank">http://www.youtube.com/v/WVo0WvuX7K0?version=3</a>

If the power ain't there, you can't extract it! facepalm

The only way near a house is to get a turbine up into unturbulent air, which means a really tall mast (think 100')
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biff
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« Reply #27 on: November 24, 2012, 03:03:52 PM »

And the sad thing is,These gimicks disappoint people and put them off any future projects which could be honest and do the business.It gives renewable energy a bad name and that what makes a lot of people in the know so angry.
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martin
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« Reply #28 on: November 24, 2012, 04:49:51 PM »

Nail on the head! The roof mounted chocolate teapot scam (Swindlesave etc.) set the UK wind industry back years, and probably did a lot to encourage the loonie fringe "anti-wind" brigade who are now campaigning against "Big Wind" (which works very well).
As those on this forum who use turbines know, there are no short cuts, no magic bullets, just a good turbine, properly sited -  which sadly precludes a good 99% of UK properties (if for no other reason than it is all but impossible to obtain consent for a decently tall tower, to get it up above the turbulence)

I have watched the UK small wind industry fall apart over the last few years, thanks to a load of crooks, shysters and assorted ne'er-do-wells who have tried to relieve the gullible of their hard-earned cash, leaving us with very few reputable companies (Futurenergy and Marlec being notable exceptions - both of whom had the sense and knowledge not to leap on the "roof-mounted" bandwagon).
When confronted with any "new" form of turbine, my advice is probably to dismiss it out of hand (history shows us there is no such thing), and if still in doubt, heed the wise words of the likes of Paul Gipe and Hugh Piggott who've both really "got the t-shirt" on wind power with many years of hands-on experience.

Sadly, during the last few years we've seen all sorts of potty ideas have been aired on this forum (often from those who's qualifications  would suggest they should really know better!), and a great many have got to the stage of being adopted, and relieving mug punters of their money, and leaving behind a very bad taste in mouths of those who've been bitten  - I would always recommend extreme caution with anything "new" in this field - it is an area that seems to attract chancers.......
« Last Edit: November 24, 2012, 05:14:54 PM by martin » Logged

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Ivan
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« Reply #29 on: December 19, 2012, 12:00:05 AM »

I wouldn't run Hugh down too much. He's the guy that actually put a data logger on a roof in Glasgow (I think) for 12months to prove he was right about the lack of wind speed near houses - take a look at his data, it's freely available. Yes, the wind speed picks up where the greatest restriction is (just the same principle that traffic moves faster in the roadworks rather than in the queue for the roadworks, but by the same token, the traffic flow through the roadworks is still rather slower than on the open road! (In the wind situation, even if the ridge experiences an increase in wind speed compared to the eaves, both are well below what it would be at twice the height of the house or on an open plane with no house).

I think 3200kWh/year is an outrageous claim, even if you had a 12m ridge to mount it on. (An average house would have 6m of ridge). Planning would be a nightmare - you simply wouldn't be allowed to do this in most cases (we can't have PV raised even an inch above ridge level).

The 500,000euro prize sounds like it might be more of an incentive than the actual market potential of this in the UK.
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