BS: Wind turbine efficiency

Subject: BS: Wind turbine efficiency
From: Grab
Date: 01 Dec 06 - 09:11 AM

For those of you wanting to be more energy-efficient, some interesting results on those "micropower" (home-sized) wind turbines they're selling in hardware stores (such as B&Q in the UK).

BBC article
Tim Hunkin article

Obviously if you're somewhere with no power at all, then anything you can get is good. But if you're trying to improve your energy efficiency, it looks like the way to be most efficient is not to waste resources on a wind turbine. Or if you are going to do it, then build your own from existing scrap materials.

But to be honest, if even Tim Hunkin can't make it work, what hope for the rest of us...?

Graham.

Subject: RE: BS: Wind turbine efficiency
From: GUEST,MarkS
Date: 01 Dec 06 - 11:08 AM

Best ways of all are still improving insulation, eliminating air infiltration, and using passive solar whenever possible.

Subject: RE: BS: Wind turbine efficiency
From: Amos
Date: 01 Dec 06 - 12:28 PM

There are commercial home wind towers you can buy, rather than build yourself, for local wind generation. It requires an average annual wind speed of 4-6 mph or higher to be effective. (I don't have that requirement in place, here.)

You can lay out enough solar panels, using today's efficiencies, on an 1800 square foot house, to completely supply all lighting, appliances and heating requirements for a small family, at least in the Southwest region. All it would need (going through a commercial contractor) is about 2% of the market value of the house!!!

The least costly benefit available imemdiately as MarkS says above is sensible conservation and passive means.

A

Subject: RE: BS: Wind turbine efficiency
From: Paul Burke
Date: 01 Dec 06 - 12:30 PM

It looks as though this small scale wind power will not only not generate much electricity, but will never pay back the energy costs of its own production. To add to which, a nice drag like that attached to your house in a gale will sooner or later cost you a new chimney stack and roof.

Direct solar water heating- low tech, unobtrusive, cheap and easy to make at home- is one of the better ways to "make a contribution". But like most of these things, you only really get much hot water when it's a bright sunny day, which is when you least need it.

It's a bit like growing beans or tomatoes: when yours are ready, they are practically free in the shops.

You can use low energy light bulbs- OK in many cases, we can put up with the weird light and the warm-up time- but the typical saving not overwhelming. If you have 3 rooms, 3 60W lights in each, on for an average 5 hours a day 365 days a year, that's 800kWHr saved by replacing them with 11W low energy bulbs. According to this web page, each kWHr gives about 170g CO2, that's a saving of 136kg CO2.

Assuming petrol's chemical formula approximates to -CH2-, burning petrol produces 3.142 (*) times its weight of CO2. The density of petrol is about 0.8 times that of water, so each (UK) gallon of petrol produces about 11kg of CO2. Your 136kg saving could be as well produced by using 12 gallons less petrol, or driving just 8.5 miles a week less at 35mpg.

I don't know where the big savings are to come, and rather despairingly think it may be only by people becoming gooder, in which case it won't happen.

Subject: RE: BS: Wind turbine efficiency
From: Paul Burke
Date: 01 Dec 06 - 12:31 PM

(*) That's very close to pi! Is someone trying to tell us something?

Subject: RE: BS: Wind turbine efficiency
From: Bunnahabhain
Date: 01 Dec 06 - 01:25 PM

A family member is installing a decent sized wind turbine, and it's one of the few practical uses of the things I have seen. They're on an upland hill farm, in a notoriously windy and exposed area, and are looking to install a 5 kW turbine, to run lighting in greenhouses during the winter.

But mostly the thing are an utter waste. At a national level (UK), the only sites which are anywhere near reliable enough are a long way from where the power is needed, and are beautiful...

Subject: RE: BS: Wind turbine efficiency
From: Donuel
Date: 01 Dec 06 - 11:34 PM

An efficient Euro wind mill is the turby but it costs $14,000 US each plus the battery banks... and might take two of them to handle large appliances.

Subject: RE: BS: Wind turbine efficiency
From: GUEST,Boab
Date: 02 Dec 06 - 02:47 AM

Good luck to those who support the idea of windmill power generation;any pollution-free device for power generation is better than nothing. But --"efficiency"? I can't imagine anything less efficient than a machine which uses as its primary power source a moving gas. Which is exactly what a windmill is. You could take any industrialised country in the world, build so many windmills that it took on the look of a porcupine, and there still would be a shortfall in power generation. Does anybody seriously believe that "Big Oil" would have been so serenely quiet about the proliferation of wind generation if the contents of their deep pockets had been to any extent threatened by wind power? I will back windmills any day in preference to fossil fuel power stations, or the supposed pollution-free nuke stations [ask the hill farmers in Scotland and Wales if they are yet free of fallout from Chernobyl--], but the day governments turn at last to the oceans for power generation, that'll be the day that the oil barons will sit up and take note---for any engineer [not employed in the oil industry!] will vouch for the fact that a water-driven turbine will hammer a wind-driven device out of sight in the efficiency stakes. Someday a combination of renewable energy devices MUST come through. Otherwise the future is frighteningly bleak.

Subject: RE: BS: Wind turbine efficiency
From: JohnInKansas
Date: 02 Dec 06 - 06:16 AM

A minor quibble over the use of "efficiency" in the thread title, and in a couple of comments.

When there's a lot of something available, and immediate purposes only need a little of it, efficiency isn't too important. You can take a lot, even if you only manage to use a little, with efficiency being the ratio of what you use to what you destroy to get it.

What's really being discussed is just usefulness, and as has been pointed out individual wind turbines are only useful to a few who happen to be living where conditions are peculiarly suitable.

For individual wind power applications there is also the consideration that your wind turbine may interfere with the one on your neighbor's roof, by deflecting or otherwise modifying the local circulation, so while a few people can have them, they can't possibly be a generally useful solution for "the masses."

It's also fine to push for one scheme over another, and water power, whether using streams and dams or tidal sources is a good one, and has been for centuries. The "efficiency" claims for water vs wind are not really much of an argument. An air-extractor can be just as efficient (arguably more efficient) as a water kind. The efficiency is the ratio of the usable power obtained to the reduction in "power" in the environment. Unless one speaks of extracting all the power of the tides, or bringing all the winds to a halt, it's not an appropriate term.

It is encouraging to see recognition that regardless of how "clean" a novel source is there are limits on how suitable it is for use by most individuals, or even for large numbers of individuals.

That point is frequently ignored.

John

Subject: RE: BS: Wind turbine efficiency
From: JohnInKansas
Date: 02 Dec 06 - 06:40 AM

Many people are working on alternative power resources, but most of the "buzz" is being directed at methods that have limited long-term prospects.

Water power, as suggested as a "best solution," is of little use to those of us in Kansas. It's 900 miles to the nearest water resources that haven't already been depleted below needs for sanitation and drinking by Colorado irrigation.

(My neighbors all have lawn sprinklers, so we're not huring too much, but I think the waste is unnecessary so mine ceased functioning more than 10 years ago. My neighbors don't like me much, but I've got more wildlife in my yard than they have .....)

Kansas has numerous suitable sites for windpower farms, but thus far the NIMBY concept has blocked development almost completely.

A current "biz-world buzz word" locally is "ethanol." Installation of new ethanol refining plants has been rapid and prolific in Kansas, but few people seem to have noticed that existing ethanol refineries demand slightly more than 40% of the total Kansas corn crop. They're still planning new capacity, and lots of people are throwing money at them. Lots of them will lose their asses, or we'll all subsidize them by paying a lot more for farm products. (Not necessarily a bad thing?).

Willie is selling lots of bio-diesel. The truckers (his main customers) do like it and many are using it when possible to some extent because they think it's the "socially right thing" to do; and the know-nots are citing him as "helping the environment." They are WRONG. Willie is helping the farmers (and he knows what he's doing, and why), by giving them an additional market for their products, but already is using most of the product that's suitable and available.

Every new idea has problems and limitations. It is necessary that we press for "better" than what we have; but it must be done intelligently, and with recognition that "different folks need different strokes."

John

Subject: RE: BS: Wind turbine efficiency
From: JohnInKansas
Date: 02 Dec 06 - 07:05 AM

A suit currently before the US Supreme court asks for (actually demands) regulation of CO₂ emissions by the EPA. The current administration is claiming that they "don't have the authority," although existing Federal regulations do appear to give them that authority. The current administration has also said that "even if we have the authority we won't." (Because global warming is a myth.)

At this point, the Court is examining whether any of the parties to the suit can prove they suffer damage due to the lack of regulation, and the real questions may get tossed on that basis - especially if the administration lawyers' contention that "CO₂ is good for you" are accepted by the Court.

The Kansas Legislature has a request for approval for three new coal-fired generating plants that are currently being "studied by the Legislature." This "study phase" will likely continue until all their buddies who can absorb study money are stuffed, and can't think of anything else to study (a feature of the Kansas Legislature); but the proposal has attracted a lot of opposition from the public.

Unfortunately, most of the public opposition seems based on the incidental fact that the market for the generating capacity is Colorado, and Kansans are extremely resistant to "being used" in this way.

The real objection to these plants is that they propose to meet the minimum existing standards for emmisions and other environmental damage. In the absence of Federal regulation of emissions (including CO₂ but also several other nasties), there is no way to predict "how to build" now, to meet possible new regulations over the 30+ year life of a new power generating plant. The plans for these three generators are "betting on" the Fed granting "grandfathering exemptions" to existing plants, and are being rushed to "beat the rules."

Bet Me? As soon as the Legislature runs out of "study money" they'll get their permit. Current legislators will get all the "study money" back as campaign donations.

The cynic from Kansas now yields the floor. (With apologies for the rants.)

But with the added congratulations for the prior recognition in this thread that "individual solutions" only work for the lucky individuals.

John

Subject: RE: BS: Wind turbine efficiency
From: The Fooles Troupe
Date: 02 Dec 06 - 07:37 AM

John, you've been listening to GUEST too much, methinks....

:-)

Subject: RE: BS: Wind turbine efficiency
From: JohnInKansas
Date: 02 Dec 06 - 07:55 AM

Hey Robin. I did apologize, although I'll concede that I got a little off topic.

John

Subject: RE: BS: Wind turbine efficiency
From: Mr Red
Date: 02 Dec 06 - 12:51 PM

Well folks - wind power has one big advantage - it is available wherever the windmill is. If that is on a narrowboat then at least you get to top-up the battery and probably cover the residual on the TV or satellite reciever. Which could be switched off rather than hitting the remote but then non-techies mostly wouldn't.

The other top-ups are going to be mains (longgggggggggggggggg leads?) or engine. It is not a case of overall CO2 budget always, availability is sometimes paramount.

Repair instead of replace is a cheaper CO2 solution.

But if you really want to ballance the books think on this. All energy is solar (including wind) except nuclear! And if we insist on spending millions of years of insolation trapped in fossil fuels in a few hundred years, we is going to exhaust the bank ballance.

If solar energy falling on the earth NOW (of whatever kind) cannot supply all our needs then we, as a world, are most definitely raiding limited reserves. 50 years of oil is a mere blink in the history of just Homo Sapiens. It ain't rocket science - but it is communal responsibility - and we ain't got that much that these days.

Subject: RE: BS: Wind turbine efficiency
From: Donuel
Date: 02 Dec 06 - 12:57 PM

The turby wind mill looks much like a double helix.

Subject: RE: BS: Wind turbine efficiency
From: Bert
Date: 02 Dec 06 - 01:12 PM

The turby wind mill looks much like a double helix.

Oh Gawd! do you think they'll come to life and take over???

Subject: RE: BS: Wind turbine efficiency
From: Schantieman
Date: 02 Dec 06 - 05:01 PM

As far as reducing carbon dioxide concentration is concerned, what we ought to do is make things - houses, furniture, ships - out of wood. This will stop (or at least greatly delay) it decaying and its carbon being respired by the decomposing microorganisms.

Or even just grow a lot more of it and then store it somewhere it won't rot. Like shrink-wrapped in plastic, down an empty coal mine.   

Has nobody thought of this?

S

Subject: RE: BS: Wind turbine efficiency
From: Grab
Date: 02 Dec 06 - 05:13 PM

Fair point on the quibble. I was thinking more in terms of efficiency as energy produced versus energy to make the thing in the first place.

Sadly photovoltaic is only a worthwhile option in places with lots of guaranteed sunlight. The Mediterranean or southwest US might quality - the UK certainly doesn't. "Which?" magazine calculated a 20-year payback term on photovoltaic in the UK, assuming that it runs for 20 years without needing any servicing.

Solar heating is a much better bet though. You just need to be somewhere where installing it doesn't mess anyone else up. Detached houses in the country and most US houses (again mostly detached) are fair game. Houses in cities or on estates might be more of a problem.

Graham.

Subject: RE: BS: Wind turbine efficiency
From: GUEST,windy miller
Date: 02 Dec 06 - 05:36 PM

I think wind turbines are amazingly efficient - have you not noticed how windy it gets when they are all switched on?

Subject: RE: BS: Wind turbine efficiency
From: The Fooles Troupe
Date: 02 Dec 06 - 08:01 PM

You can buy in Australia hot water heaters that are 'energy pump' devices that extract heat from the surrounding air to heat the water. they have a small electric pump that uses far less energy than heating the water with electricity.

I remember a big fuss many years ago about 'thermal pump' air-conditioners that sourced/sinked heat from a huge web of pipes buried in the earth nearby.

Subject: RE: BS: Wind turbine efficiency
From: GUEST
Date: 03 Dec 06 - 12:41 PM

In the US, at least, fossil fuel costs are still so low that solar or wind energy approaches aren't economically feasible---unless they're subsidised by the government.
In New Jersey, f'rinstance, about half the cost of a photovoltaic installation is provided by the state government, and the local power companies (who don't want to have to build more generating capacity) have agreed to buy any excess generated at the current maeket price. This provides a roughly 9-10 year payback, which would be drastically reduced if fuel prices rose during that period.

Heat pump water heaters work, but they draw their heat from air which may have to be heated by other, less efficient means. Ground- or water-sourced heat pumps are an excellent solution if a)you live in a temperate climate and b) if you can live with a rather high initial cost. one of their major benefits is the low operating cost for either heating or cooling.

Subject: RE: BS: Wind turbine efficiency
From: The Fooles Troupe
Date: 03 Dec 06 - 07:26 PM

With winter temps of 20 deg C to nealy 30 deg C in daytime in some parts of Australia, there's no need to heat the external air...

Subject: RE: BS: Wind turbine efficiency
From: s&r
Date: 04 Dec 06 - 03:36 AM

We've just had cavity wall insulation installed for £200 and reinsulated the loft with 200mm insulation. The difference (subjectively till we've had time to compare figures from last year) is phenomenal. The house heats in a fraction of the time it used to, and the timer is set to not turn on a.m. because the house remains warm.

we use mostly low energy bulbs but I'm not convinced they make much difference in energy usage because the wasted energy in producing heat of the incandescent lamp is just added to the house heating. Street lamps I suppose are all low energy.

I think there's still room for reducing our consumption before we go down the road of Wind Turbines and PV panels.

Stu

Subject: RE: BS: Wind turbine efficiency
From: GUEST,Jim and the whippets
Date: 04 Dec 06 - 04:07 AM

If you live in UK uplands outside national park boundaries (as we do) watch out for mass landscape despoilation by ugly useless and subsidised (by you and me) wind turbines. This feelgood nonsense is very likely to happen in the near future under tory or labour governments, and will ruin the aesthetic and ecological value of huge tracts of land.

You've been warned. Fight now or lose it all.

Jim and the whippets

Subject: RE: BS: Wind turbine efficiency
From: Mr Yellow
Date: 04 Dec 06 - 08:03 AM

Under soil heat collection -

Apparently, at the depth of water supply pipes the temperature remains fairly constant at 6 deg C in the UK. Hence the depth of supply pipes - never freezes.

I would have thought summer cooling would be more efficient winter heat collection but I have seen TV programmes where they install the garden pipes.

Mind you sub-soil windage is not that great...............

Subject: RE: BS: Wind turbine efficiency
From: Paul Burke
Date: 04 Dec 06 - 09:17 AM

Large wind turbines can make a worthwhile contribution. The generating power increases with the square of the blade length, and the wind speed is also higher further from the ground. Also the electrical and mechanical efficiency increase with size.

I personally don't find them visually unpleasant, and their effect on migrating birds has been exaggerated. After all, birds learned to live with windmills from the middle ages to the nineteenth century.

Subject: RE: BS: Wind turbine efficiency
From: Gervase
Date: 04 Dec 06 - 09:39 AM

I've got three quite near me, and when I first read the claims about bird carnage I thought I'd go and have a look. I've now been several times at various times of the day and seasons of the year.
Believe me, when those blades hit a bird they must do a darned good job, because I was unable to find a feather, let alone any recogniseable part of a mangled fowl.
Or do you think perhaps someone was scaremongering.
It's the same with the noise. I read a letter in a newspaper from someone saying that the low frequency noise made by the turbines was intrusive.
I think I must be deaf. Standing within 50 metres I only heard a mild sussuration as the blades went round, but no low frequency hums.
Or was it scaremongering again?

As these arguments are routinely trotted out by people opposed to wind turbines and are demonstrably wrong, it does make me suspect the other arguments they use.

Subject: RE: BS: Wind turbine efficiency
From: Bunnahabhain
Date: 04 Dec 06 - 10:26 AM

Bird strikes vary vastly, within in a small area. SNH ( Scottish Natural Heritage, the Govt busibodies with noses in this area) have been collecting data, and have opposed several schemes as their siting would cause excess bird strikes, and proposed acceptable alternatives, often only half a mile or so away.

This is a body renowed for paying very little attention to the wishes of people, especially locals.

Subject: RE: BS: Wind turbine efficiency
From: GUEST,Jim and the whippets
Date: 04 Dec 06 - 10:44 AM

The ecological damage isn't confined to bird strike. Wind farms need access roads and these also need drainage. Putting in new roads and drains on moorland is disruptive (proof: a local estate was prosecuted by the EA and heavily fined for putting in new moorland roads for shooting purposes).

Most of the people who profess a liking for large wind turbines sound like suburbanites who want to keep the heating on and feel good at the same time. Their idea of environment is the small shrubbery at the entrance to their local Tesco. Those of us who live and work in the hill country are daily affronted by the steady encroachment of these unsightly and usustainable contraptions.

Is it a coincidence that a windmill was a big part of the plot in Animal Farm?

As someone said earlier here, why don't people look at water? There's lots of it in our hills and it drove the first industrial revolution. Nottingham Trent Uni has done some great work with re-used and modified AC motors to create small cheap and truly sustainable power generators.

Subject: RE: BS: Wind turbine efficiency
From: Paul Burke
Date: 04 Dec 06 - 11:24 AM

Is it a coincidence that a windmill was a big part of the plot in Animal Farm?

He's rumbled us! The alternative energy eco-fascist-commies, suburbanites and townies, whose only plan is to dominate the world by installing wind turbines and thus destroying rurally idyllic Archerland!

Why not water? Because to get significant generation from hydroelectricity, you need massive amounts of water. Dams, which swallow up millions of tones of concrete, destroy whole ecosystems not to mention communities (Ladybower near me), and oops need access roads.

We had a look at one for our village. A nice little brook, good head but not much volume. Estimated cost £8000. Estimated output 160W.

Come and live up in't country wi' us northern folk, where we either heat our homes and feel bad, or don't heat our homes and feel good, or don't heat our homes and feel bad. Ever seen a Yokshireman smile?

Subject: RE: BS: Wind turbine efficiency
From: Gervase
Date: 04 Dec 06 - 11:47 AM

Townies? *snort* Try telling that to my sheep!
An here in West Wales there are still rather bitter memories about flooding valleys.

Subject: RE: BS: Wind turbine efficiency
From: Donuel
Date: 04 Dec 06 - 11:57 AM

A wind turbine is super if used only to run a heat pump (two Saline heat exchanger tanks) that is buried 20 ft. down where it is always 52 degrees F.

That way you gets lots of heat in the winter when it is always fairly windy.

Add a solar panel to the system and it all flows together to make a nice off the grid Heating and AC unit.

It is my design but I have never built it. It seems elegant enough on paper.

Subject: RE: BS: Wind turbine efficiency
From: Donuel
Date: 04 Dec 06 - 12:03 PM

But on a dark windless frigid day you need a wood stove.

Some of those wood furnaces you put outside look mighty nice.

meanwhile r&d is right about insulation.

Subject: RE: BS: Wind turbine efficiency
From: Bunnahabhain
Date: 04 Dec 06 - 12:23 PM

There is considerable scope for medium scale Hydro-power schemes. Germany does it, and we could, using the same kind of sites. The sites used a few centuries ago, to grind cereals, run forges, etc.

They are costly at the moment, but they would become much cheaper if they were more common. The small ponds assciated with this don't displace people, and are positivly good for the enviroment in their own right. Mill ponds are prettier than turbines as well.

Subject: RE: BS: Wind turbine efficiency
From: GUEST
Date: 04 Dec 06 - 05:06 PM

I've long fancied building a vertical wind turbine, which is a 44gal/200l drum split vertically, offset and mounted on a shaft. They work like the Castrol signs did, whirling around in any wind at all, and not directional. Rig a 12v car generator to that, and it might produce enough power to charge a battery of batteries.

Subject: RE: BS: Wind turbine efficiency
From: MaineDog
Date: 04 Dec 06 - 05:14 PM

A major problem with heat pumps is that you must not freeze the heat source exchanger. This will happen if you try to get too much heat out of it: You'll get a nice insulating sheath of ice around it, and then, no more heat will flow!
MD

Subject: RE: BS: Wind turbine efficiency
From: GUEST,petr
Date: 04 Dec 06 - 08:41 PM

re; solar - germany and austria have installed over several hundred thousand solar roof systems, more than anywhere else in the world.
And they arent in particularly sunny latitude.

also an Interesting bit of info (from Mark Jaccards book - Unusual Suspects - Sustainable Fossil Fuels)
not counting the 30% of the solar energy that is reflected back into space the amount of solar energy that hits the earth is 390,000 Exojoules.
The total worldwide energy usage is 400 Exojoules (ie. 1/10,000th)
Of course it doesnt mean all that energy is usable, as most of it goes the latent heat, evaporation of water etc. (only less than 1% goes to support life on earth) but its an interesting fact.

- regarding ghg reduction (a U. Cal physicist did a study that the US could actually meet its Kyoto co2 reduction requirements by dumping farmwaste into the oceans at a fairly small cost of $3billion US
- (which would not totally get rid of the co2) rather it would take 1000s of years to breakdown) but it would sequester the co2 long enough to do something about the problem.

- this same physicist also proposed using fine diatomaceous dust (released from planes) to block particular wavelengths of solar radiation - in such a way to reduce the heating (we already know that global dimming - due to pollution and jet trails from planes -has a cooling effect).

- regarding excess energy storage from say windpower, rather than batteries, why not a flywheel (which is 90% efficient) or compressed air (around 60% efficient) as opposed to hydrogen electrolysis which is fairly inefficient (I believe around 30%).

Subject: RE: BS: Wind turbine efficiency
From: GUEST,Jim and the whippets
Date: 05 Dec 06 - 03:40 AM

You dinner party greens can't read either.

The style of hydro I'm talking about works on small steep streams with no need for damming - single property installations, based (as I said) on converted AC electric motors (typically 5hp size).

Just to square the record I'm actually a fiancial industry worker living in East London and the whippets are imaginary.

Sorry, Yorkies everywhere.

Jim

Subject: RE: BS: Wind turbine efficiency
From: Paul Burke
Date: 05 Dec 06 - 03:41 AM

Sounds like a rather dumb solution. We've messed up the atmosphere, let's try to cure it by messing up the sea as well.

As for global dimming, that's already been implicated in the desertification of sub- Saharan Africa. The big problems with such schemes are that once you put it in, it's a devil of a job to get the stuff out again when you need to; and that you can't tell what it's going to do in enough detail to be sure whether it will make the problem better or worse.

Flywheels are big and very heavy, and need a lot of maintenence around the bearings. And if they crack up, it's like a bomb going off. Compressed looks a good solution, and you could probably replace the electric generators by compressors directly at the turbine shaft, though the pressure required to store a lot of energy sounds a bit frightening. Hydrogen is of course dangerous to storeas a gas, but I expect some clever scientists can work out a chemical way to store it if they haven't already.

There is another solution, currently used by nuclear power stations. These can't be turned on and off quickly to meet demand, and are kept on more-or-less constant (thermal) output. At times of low demand, the energy produced is usually just dumped. But in some cases, in the UK notably Wylfa power station in Anglesey, they have been combined with pumped- storage hydro- electric schemes. Water is pumped uphill at times of low demand, and can then be released to meet short- term peaks like when everybody puts the kettle on at the end of the Queen's Speech. This kind of scheme could be used to store energy from intermittent wind power.

They have of course all the disadvanages of hydroelectric schemes.

Subject: RE: BS: Wind turbine efficiency
From: Paul Burke
Date: 05 Dec 06 - 04:59 AM

Well, Jim. The water has to come from somewhere. If there's a big head of water, it needs to be taken from a good way above the site of the generator. The smaller the flow, the bigger the head needed for a useful output. So either the user of the power needs to own all the land from the water take off point to the generator, or he needs to have kind neighbours who will let him cross their land with his pipe. They also need to be forebearing about the loss of water in their bit of the stream, which might also damage local woldlife (stet, I like that word).

It was in fact such a scheme that we looked at for our village, and the stream is just too small for worthwhile power, even if we could get everyone to agree. And this stream ran at least 4 mills in the 18th century, which just goes to show how our demand for power has changed. The mills can't have been more than a few hundred watts each (though perhaps mining and opencast working has disrupted the water flows so the stream is smaller).

Subject: RE: BS: Wind turbine efficiency
From: Gervase
Date: 05 Dec 06 - 05:49 AM

A neighbour of mine has been trying for the past two years to do just that - he lives in an old mill which has a leet, with a working water head of around three feet (albeit a slow flow), powering an enclosed Pelton wheel coupled to the working parts of an old two-stroke generator.
He's chuffed to bits because he can light a 60 watt bulb in his shed/office. Somehow I don't think it's going to remove his dependency on the grid!

Subject: RE: BS: Wind turbine efficiency
From: Paul Burke
Date: 05 Dec 06 - 06:27 AM

The Pelton wheel is for high- head applications, so he's using it very inefficiently. A Kaplan turbine is usually used for small heads, it's basically a propellor. He might be able to make one out of an old boat propellor and fabricate a chamber for it.

Subject: RE: BS: Wind turbine efficiency
From: Paul Burke
Date: 05 Dec 06 - 06:39 AM

But this study suggests that the old- fashioned waterwheel, properly constructed, may be as good as anything for a site like your mates. He can have it both ways- effiecient AND romantic!

Subject: RE: BS: Wind turbine efficiency
From: The Fooles Troupe
Date: 05 Dec 06 - 06:56 AM

Incidentally, if you have a lot of water flow and a small head (?!) you can use a Ram Pump to lift a percentage of it up higher than teh stream.

Subject: RE: BS: Wind turbine efficiency
From: JohnInKansas
Date: 05 Dec 06 - 07:10 AM

Grab's original post linked two different pages. I did look at the first one immediately to get an idea of where he was going, but only glanced at the second. I just got around to taking a closer look at the second (Tim Hunkin) link.

In Hunkin's first picture it looks like he's attempted to use an automotive "radiator fan." I can't tell from later pictures whether he got something much better for later trials, but the auto fan is one of the worst possible "randomly selected" propellers one might choose for a wind turbine project. It's designed to push a lot of air at low speed (low rpm), but doesn't derive much torque from air flowing through it. The thin flexible blades, in fact, are intentionally designed to "bend out of the way" when ram air due to vehicle motion is sufficient for engine cooling, and to "flatten" and pump nothing at high engine rpm (where it's assumed the vehicle's moving and the fan isn't needed).

If one must use a fan of this kind, he's got it mounted backward to what is needed to get best (which won't be much) result from this kind of fan.

A fixed, stiff-bladed fan from an older automobile (pre-1950s emission regulations and the push for efficiency?) would be a slightly better choice. A blade salvaged from a "shop fan" would also be a possibility, and you might find one up to about 30" diameter if you look around a bit. But for an effective "propeller" generator, I'd suggest visiting the nearest model airplane shop and asking for "the biggest ya' got." That probably won't be quite as big as you'd want for a practical generator, but would give you a starting point for trying out things.

An "airplane propeller" actually is "built backwards" for use as a generator driver, but the efficiency with a true airfoil will be very much higher even "running in reverse." For an airplane prop, the "angle of attack" is off the plane of rotation of the prop, so that rotation produces lift in the airplane forward direction. For a turbine-generator prop, the angle of attack needs to be off the perpendicular to that (from the plane of the blade and direction of flow) to produce lift in the direction of rotation of the prop. Approximately, the prop blade needs to be rotated 90 degrees on the hub, and the propeller ¹allowed to rotate in the opposite direction - not an exact description but close enough.

¹ If you want to keep the same direction of rotation, you have to reverse the twist of the blades.

For a starting point for developing your propeller turbine, a full airfoil blade section probably isn't necessary. You'll need it when you start to work up the efficiency, but a proper "lifting line" in a flat (metal?) blade would give reasonable performance for a start.

The classic reference is Abbott and Doenhoff, Theory of Wing Sections, from NACA wind tunnel research ca. 1949, republished 1958 by Dover and probably still easily available since it's a "classic." My copy was $4.50 but that was in 1970, so it's probably a bit more now.

I won't attempt to estimate how many draughts you'll need to buy for your neighborhood aerodynamicist for assistance with the calculations, but they're not really all that difficult once you get the definitions straight. (Although getting the "twist" right, so the angle of attack varies with distance from the hub can be tricky.) Just be sure to design so that tip speed doesn't exceet about 0.7M at your max design wind speed, for the airfoils in the book.

If you prefer to work with the "vertical" turbine, considerable information on the design was published when one of the ocean research vessels tried using one as a sail. The generic search term "Darius sail" or "Darius turbine" should get some info, although the sail application may be a bit old to find much of the technical stuff via Google.

I will suggest that although technology has advanced somewhat, and the requirements are better known, it's not likely that you'll get much better results with a "home built" than was available when an uncle tried a commercial wind generator ca. 1950.

Results were:

In Kansas wind with avg wind velocity 27 mph (approximately),

on a 40' windmill tower on top of a hill,

with 2-bladed prop direct coupled via a step-up gearbox (unknown ratio, probably 4:1 but maybe 7:1?),

running 24 hours per day, 7 days per week,

he was able to keep a bank of 6 or 8 auto batteries sufficiently charged to listen to the radio for about 2 hours at a stretch - usually on at least 3 days per week.

You can do much better with commercially available hardware now; but location and weather are critical to whether you'll get useful results, relative to what you hope for.

John

Subject: RE: BS: Wind turbine efficiency
From: JohnInKansas
Date: 05 Dec 06 - 10:04 PM

So Go Fly a Kite?

John

Subject: RE: BS: Wind turbine efficiency
From: Grab
Date: 06 Dec 06 - 07:16 AM

Hunkin says that the fan is actually from a blower (presumably leaf blower or similar). So I doubt it would have the problems with flexibility and stuff that you mention, John. Granted, it's still not the most efficient turbine in the world! :-) But as he said, even improving blade efficiency wasn't going to cut it. As you say, the critical part is whether you get enough wind over it, day in, day out, for it to cut the mustard.

Graham.

Subject: RE: BS: Wind turbine efficiency
From: The Fooles Troupe
Date: 06 Dec 06 - 07:27 AM

He should put it in a Mudcat BS thread...

Subject: RE: BS: Wind turbine efficiency
From: dick greenhaus
Date: 06 Dec 06 - 12:07 PM

the key word in "appropriate technology" is "appropriate" (though "technology counts, too). Wind energy is most suitable for (surprise!) windy areas; solar, either passive or active, works best in sunny areas.
What's needed in the US are things like solar-powered air conditioners and irrigation pumps.

Subject: RE: BS: Wind turbine efficiency
From: GUEST,petr
Date: 06 Dec 06 - 08:49 PM

Paul, I would be so dismissive of Benfords ideas,
here is the link Gregory Benford

Regarding your point on flywheels - it is true they are dangerous
but one idea being developed is to make flywheels from compressed composite material that would disintegrate into dust. (Already in 1890
when the InterUrban railway was being built in Vancouver, the design incorporated energy storage in a flywheel)

ALso your point on pumping water uphill, is another good energy storage solution, (one example in the US being Raccoon Mountain )

it is interesting to see how efficient small wind turbine might be. In Ontario the Bruce peninsula which gets a lot of wind from the lakes there is a large wind turbine which generates enough power for 500 homes (about a 1/4 of the inhabitants of the peninsula).

ONly a few months ago, I noticed Canadian tire selling small wind turbines as well as solar roof top systems. Since our house gets alot of
the southern sun - its too hot to even sit on the deck in the summer.
I had been considering trying out a system. Now ideally if the govt gets its act together and comes up with a carbon trading system, homeowners with such systems should get some credits..