The Truth About Small Wind Turbines

[Rob Beckers]

I've written a (rather lengthy) Web page that tries to inform people who are considering a small wind turbine in their backyard. (http://www.solacity.com/SmallWindTruth.htm)

It dispels the manufacturer's hype; gives reasonable numbers for expected energy production, and explains why some of the things that manufacturers seem to emphasize (such as cut-in wind speed) are meaningless. Maybe most importantly, the article cites real-world performance, with links to various studies done on this, that show most don't even make half the expected energy production. In my opinion, anyone considering a small wind turbine (20 kW and less) should read this.

The article is meant to be an honest overview of the reality of a small wind turbine, based on my own experience and reports by others. My hope is that it will dissuade those that just do not have the site or stamina for a small wind turbine, while giving those that go ahead a reality check.

If anyone has comments or suggestions, especially anything that can help improve this article, please post! I welcome all feedback.

-RoB-

[Dale Sheler]

That should be required reading for anybody looking into small wind, very nice job, there is one sentence that needs some help though.
"Wind turbines do work; put them in nice, smooth air and they will energy production is quite predictable"
Maybe a comma between will and energy?

[Rob Beckers]

Thanks Dale!
That sentence was the result of partial editing (it read differently before), and my proof-reading didn't catch the mistake. I've fixed it. If you see any more errors let me know.

-RoB-

[Chris Olson]

In yesterday's Wind Energy Smart Brief from the AWEA there was an article about some installer putting Windspire turbines up in MA.
http://www.wickedlocal.com/truro/topstories/x163795272/Small-wind-turbines-catching-on

I got somewhat of a kick out of some parts of that article:

As for the Moore’s wind turbine, Robinson told the commissioners that he’s a little disappointed with the way it has been working, but said he hopes to improve its performance by raising it from 23 to 30 feet.

Hillary Greenberg, health and conservation agent said if a turbine fell down, it might slide down the coastal bank.

And the final sentence, which tops them all:
The commission approved all four Windspires, with the condition that Robinson monitors them for negative impact to birds and bats.

They got a picture there of one of these Windspire machines and it looks to me like it has to grind some tree branches off so it can start to turn. There's a phrase we use up here in the Wisconsin North Woods to describe these people: "The blind leading the blind".
--
Chris

[Russ Bailey]

Excellent document Rob!

I posted a link to it over at Solar Panel Talk. We don't talk about wind much but anyone thinking of a small turbine would benefit by reading your post.

Thanks and well done!

Russ

[Rob Beckers]

Chris, I got a kick out of that picture in the news article! In fact, I am sorely tempted to steal it and put it in my Web article as an example (a rather obvious one I'd think) of how *not* to place a turbine. I recently saw a Web site that collected the "top 10 poorly placed turbines". This one would vie for honors in there.

Sad to see though that if Mr. Robinson is telling the truth there are over 6000 of these Windspires sold. An unfortunate example of the power of marketing, with no basis in reality.

Hopefully someone will point the people involved in that story to my Web article. They would benefit from some basic wind turbine education.

-RoB-

[Chris Olson]

Hopefully someone will point the people involved in that story to my Web article. They would benefit from some basic wind turbine education.


I thought that story was an excellent example of what your article points out as all the WRONG ways to install a wind turbine, and why most of them don't work, or only work marginally.

Wind turbines are machines with moving parts and you can't tell somebody it'll require no service for 20 years "because it only has two bearings in it". That's one of the most ludicrous things I've ever heard or read. I'd like to tell Mr. Robinson in person that if he put that turbine in a place where the wind actually blows it'll be needing maintenance in two weeks because it will more than likely be busted. You think the stresses on a HAWT are high in high winds? They don't hold a candle to the stresses on a VAWT and its tower because of the rotating mass and amount of swept area that has to absorb huge amounts of energy contained in powerful gusts. Even the drag side of a VAWT rotor becomes nothing but wind frontal area in powerful winds, for pete's sake.

That being said, small wind turbines installed even in poor locations can generate a lot of usable power if it wasn't for the maintenance bill making the investment in the turbine not worthwhile. As an example, my turbines ran here most of the winter in temps down to 37 below and the first thing I do on a good day when it's in the low 30's is lower the towers and change oil in the gearboxes from the diesel fuel/oil mix that I use in extreme cold, to straight oil for warmer weather so the thin stuff doesn't start weeping out past seals and sling oil all over the place. Then go over all the bolts and nuts - there's always a few that need to be torqued. Shoot a couple pumps of grease in the yaw bearings. By the time I get done servicing one turbine I got 3 hours in it by the time I get the tower back up.

One whole day shot servicing my own turbines to keep them running at peak efficiency and with zero downtime. I was still outside servicing the last one at 9:00 at night the other day, and when I didn't come in for supper my wife came out and took a picture so she could remember what her husband looks like. LOL!

The point being, I know of few people capable of keeping a turbine running, and when they have to hire somebody like me to do it for them, that turbine had better work to make it pay off.
--
Chris

[Dale Sheler]

OMG, you read an article like that and it's about enough to make your head blow clean off, there are SO many people out there getting taken to the cleaners so badly.

[Rob Beckers]

I couldn't resist. I know, I'm weak in the face of temptation! :embarrassedt: . I've added that atrocious picture of the VAWT in the trees to the article. To be nice, I've also linked to the source; since that's a prime example of wind turbine ignorance it fits nicely to my article. I never seize to be amazed...

On an entirely off-topic note: My PV array here on the house made 28 kWh today :cheer2:. The most ever, since coming online late November (snow almost every day since). It's 6,460 Watt total, split in 1/3 facing south-east, 2/3 facing west. Several modules are still snow covered, so it could have done more, but I'm climbing on the roof in winter. Today started out -20C with clear blue skies, that's what did the trick.

-RoB-

[Chris Olson]

On an entirely off-topic note: My PV array here on the house made 28 kWh today :cheer2:. The most ever, since coming online late November (snow almost every day since). It's 6,460 Watt total, split in 1/3 facing south-east, 2/3 facing west.

I assume you have about 10 hours of daylight this time of year. So 28,000 watts for ~10 hours is an average output of 2.8 kW during the day. Or about 43% of the rated output capacity of the array for every hour of daylight.

That's better than mine did yesterday, although my panels are only 1,230 watts and we didn't get any sun until after lunch time. I got 3.46 kWh from mine, or 346 watts/hour, which is 28% of their rated output capacity for every hour of daylight.

I got 37.8 kWh from my turbines in the same previous 24 hours, however we had winds up to 32 mph for part of that time. Today, the sun is supposed to shine in the morning, then cloud over and the wind pick up this afternoon at 5-10 mph, then increase to 15-25 mph tonight. If it does that a single 1,200 watt turbine will beat the solar in output again by a pretty hefty margin.

Even with the hours of daylight increasing now, this is pretty much the story in this part of the country in winter time. You can spend thousands on solar panels and a single wind turbine will make more power in a day at a fraction of the cost per watt output. As the length of days increase towards summer that begins to reverse.

The radio station said we had a total of 7 hours of sunshine here for the entire month of January, and during those 7 hours my panels were buried under snow so deep it wasn't even worthwhile to dig them out.

There's some truth's about solar power too.
--
Chris

[Ralph Day]

Ok, I have to. My 10kw microFIT produced 79kwhr yesterday. Cold, clear with a breeze to keep the panels cool. Maxed out at about 9:45am until 2:45pm. No clouds to interrupt the power curve. Not so today.

[Rob Beckers]

79 kWh... Dang!!! That is pretty huge for a 10kW array. Bet you won't see that happen in summer.

I'm hoping the coming high temperatures will melt off the remaining snow of my array. There are still a few panels covered, and they're dragging down the rest. I'd like to know what the array can do on a really cold sunny day (looks like we'll have a few more of those coming).

-RoB-

[Ralph Day]

Rob,
The highest days so far were in July and August. They didn't peak above 10 kw but the solar day is so much longer. Just need a -15C day in July:D

You can see past production on the graphs portion of the Enphase visitors page...click on 12 months to see year to date production.

Are your panels compeletly inaccessible? Are poles not made long enough to reach them from the ground?

Ralph

[Rob Beckers]

I'm stoked! Paul Gipe sent me a message after reading the "truth about small wind turbines (http://www.solacity.com/SmallWindTruth.htm)" article that I wrote. He told me I could quote him, so here it is:

"I wish I'd written it!"

--Paul Gipe, author, renewable energy advocate, and industry analyst


Paul is one of my heros. For those that don't know him, he has been a small wind advocate (in the good sense, promoting realistic information) for decades. He has also written a number of books about wind turbines, small and large. Check him out at Amazon, if you want to learn about wind turbines his books are excellent.

Ralph, most of the panels are almost inaccessible; they're up on the second floor roof, pretty high up on that roof too since there are dormers sticking out below them. A third of the modules is on the garage roof, and they would be accessible. That section actually sheds snow quite well all by itself, because there's nothing holding the snow back (the dormers on the upper section do that). They're all at a 33-degree pitch. I'm philosophical about it; the winter is not going to contribute a whole lot to annual energy production. In particular December and January, when the days are so short anyway. At least in February we get enough warm days to clean off the panels every now and then, limiting the losses.

-RoB-

[Dale Sheler]

Wow! Kudos Rob! That is high praise from a heavy hitter like Paul Gipe!

[Paul Bailey]

Good job Rob: I keep telling people what I know on renewables if they ask, I hope I'm not being too negative here on certain subjects, as I definately do not profess to know it all, but I've studied renewables for close to 30 yrs. An off gridder will know it best and also know there system capability real well of course, especially getting thru the winter. Lets just say theres alot of Dealer deception ,way to much of this, intent here is not to pounce on all RE dealers, but some skimp on things that would be a couple thousand dollar differance to do it right on a 60K dollar install then they call me since I hate people being ripped off, and I'm interested that people have invested in being sustainable so I'll help for free.( no I'm not in business or Off grid).
Rob speaks the truth here and I appreciate that, and Paul Gipe has been professing Small wind truths for along time. Marketing keeps pushing a hole lot of crap ,(miracle turbine for your roof that will power your house that starts at 3 mph), Also seen a few sneaky Fit installs but thats another story... Sorry for the rant Guys. I'm somewhat off topic again for this thread. . :(

[Ralph Day]

Sneaky FIT's Paul?

Is that people who are hoping for no audits?

Ralph

[Ken Hall]

Rob,

I wish I had read your article 2 years and $$$$ ago. My SWG 5Kw will never generate enough to to pay off its cost. I'm now hoping it will generate enough to pay its maintenance.

Too low of tower, too close to buildings, trees...

I'd add power yawing instead of tails/auto furling as another thing to stay away from.

Wiser but poorer,

Ken

[Ken Fields]

I've worked on the solar side installations for a couple years, and really love the idea of small wind, but have had trouble wrapping my head around the realities of wind turbines and their production... obviously the manufacturers I've spoken with all claim that wind power is great, and they haven't been too eager to reply when I ask them what's the down side... definitely bookmarking your article and will keep it handy for when I talk to clients. Thanks...

Ken
__________
Lime Light Power (http://www.limelightpower.net)

[Rob Beckers]

Thanks Ken!
As pointed out in another thread, my estimated production numbers may still be on the high side (even if the actually attempted to lower the bubbly projections of manufacturers).

-RoB-

P.S. As you probably noticed, and stated in the rules and sign-up instructions, we use our real names for the account names on this forum. I believe it has helped to keep things friendly over the years, where other forums regularly erupt in flame wars since people can hide behind 'handles'. If you would be so kind to send me a Private Message with your name I will change the account to reflect this.

[Chris Olson]

Thanks Ken!
As pointed out in another thread, my estimated production numbers may still be on the high side (even if the actually attempted to lower the bubbly projections of manufacturers).

I have to say, Rob, I don't care for the method you used at all to calculate output. LOL!

On Hugh's website there's a little chart he has there that shows estimated output of various size machines. The chart is on this page if you scroll down a bit:
http://www.scoraigwind.com/axialplans/index.htm

He's got m/sec there, and I think 12 mph is about 5.4 m/sec. If you sort of extrapolate in there and use 240 kWh/month for a 12 footer @ 5.4 m/sec that's about 2880 kWh per year. Which is my experience is pretty close to what they actually make.

Sure, I know a grid tied machine can make more power because of not being "clamped" by the battery bank and some slight losses in battery charging. But I still don't think that would make up the difference to 4300 kWh/year.

And I think that brings up a good point; a lot of these output figures from manufacturers are not from actual testing and data logging like mine and Hugh's numbers are. They're calculated.
--
Chris

[Ken Fields]

P.S. As you probably noticed, and stated in the rules and sign-up instructions, we use our real names for the account names on this forum. I believe it has helped to keep things friendly over the years, where other forums regularly erupt in flame wars since people can hide behind 'handles'. If you would be so kind to send me a Private Message with your name I will change the account to reflect this.

My bad. I'm a little new to forums in general, have obviously read them thousands of times, but never really participated until recently so I apologize for any breach in etiquette. Will PM you now.

[Rob Beckers]

I have to say, Rob, I don't care for the method you used at all to calculate output. LOL!

I'm sorry to hear you put so little stock in physics and engineering Chris...


On Hugh's website there's a little chart he has there that shows estimated output of various size machines. The chart is on this page if you scroll down a bit:
http://www.scoraigwind.com/axialplans/index.htm

He's got m/sec there, and I think 12 mph is about 5.4 m/sec. If you sort of extrapolate in there and use 240 kWh/month for a 12 footer @ 5.4 m/sec that's about 2880 kWh per year. Which is my experience is pretty close to what they actually make.

Looks like Hugh and I are in exact agreement: Let's take the middle of his table, 3 meter diameter (10') and 5 m/s annual average wind speed. Hugh predicts 146 kWh/month, or 1752 kWh/year. Look in my table, 3 meters and 5 m/s. I predict 2351 kWh/year for an MPPT loaded machine for grid-tie. Take 20 - 30% off this result for direct battery charging and you'll get 1645 - 1880 kWh/year. Hugh's number is smack in the middle of that! So your point is again?....


Sure, I know a grid tied machine can make more power because of not being "clamped" by the battery bank and some slight losses in battery charging. But I still don't think that would make up the difference to 4300 kWh/year.

Not following where you're getting this from...


And I think that brings up a good point; a lot of these output figures from manufacturers are not from actual testing and data logging like mine and Hugh's numbers are. They're calculated.
--
Chris

The point is that those calculations are based on physics. Pretty solid physics actually. The trouble with real-world installations (while very valuable) is that they are generally hard to compare one to the other. Each has different factors for turbulence to deal with, heck, their wind distributions may be very different. Realistic calculations based on site measurements and physics are still the best way to go IMO

More in general though, I can't seem to win... :pout:
I get hate-mail from those peddling wind turbines, that do not want their customers educated, claim my article is too negative, and I cost them business. Then there's the other camp, such as you, that claim my numbers still exaggerate production, and give people an overly optimistic picture.

Such is life I suppose. No good deed goes unpunished!

-RoB-

[Chris Olson]

I'm sorry to hear you put so little stock in physics and engineering Chris...


LOL! A long time ago when I went to work for Cummins as an apprentice engineer I was going to conquer the world. There was nothing I couldn't solve with math and physics and calculations. The first week I was there a grizzled old engineer sat me down and told me, "Look son - there's all sorts of theories and calculations that say how it SHOULD be done. And there's the real world where reality says how it CAN be done. The two are rarely the same."

I never forgot that lesson. And it applies to wind turbines. They rarely, if ever, perform in the real world to the level that calculations and engineering and physics say they will.


Not following where you're getting this from...


If you look in your article where it says "For the metrically challenged, here is the same table using imperial numbers:"

OK, so I follow the columns there and I was looking specifically at 12 foot machines because that's what I build. It looks to me like the table indicates that a 12 foot machine is going to make 4316 kWh/year @ 12 mph average.

To look at this from a different standpoint, that means that machine has to develop an average of almost 500 watts per hour, 24 hours a day, 365 days a year. I know of no 12 foot turbine ever built that has logged that kind of power output, MPPT, grid-tied or not, on a site with a 12 mph average wind speed.

Hugh's chart says that 12 footer will make approximately 2,800 kWh/year, which is more realistic. And my own testing on my own machines comes up with about the same.

So here's what happens. A customer is interested in a 12 foot wind turbine. So he spends a year logging wind data with a MET pole and finds his site average is 12 mph. So he looks at the chart and sees that he's going to get 4316 kWh/year out of this 12 foot turbine he might buy. So he buys it and puts it up. Then finds out it only makes 2800 kWh/year. This is repeated over and over and over again in the wind power business with just about EVERY single person that invests in a wind power system.

It is NOT a flaw in wind power. It does NOT make solar "better". It does NOT make wind power systems not worth looking at or installing. The basic problem is that methods used to estimate power output are based on theory and physics and calculations that do NOT work out in the real world. Just like that old project engineer told me - there's theory and there's reality. The two are rarely the same.

I think I told you when I signed up on this forum that has been one of my pet peeves for as long as I can remember in the wind power business. Turbines are over-rated because the ratings are NOT based on real-world testing and data. And until that problem gets fixed in the wind power business, there's just going to be people claiming that wind turbines don't work, or aren't worthwhile.

I look at posts here from Ken Hall who says he has a 5kW wind turbine. And he should've read this article you wrote before he bought it. Ken should've consulted with me and I would've told him his so-called 5 kW wind turbine is NOT a 5 kW turbine. It's probably more like a 500 WATT turbine day in and day out, 24 hours a day, 365 days a year. All because real world reality with wind power is thrown right out the window with engineering and physics being used to claim that turbine is a 5 kW machine.

I'm not picking on you or your article - it's a good article. I'm just pointing out that it still does not address the real problem in the wind power business. That problem is the same as an auto manufacturer building a car and marketing it, claiming it gets 30 mpg. But in the real world it only gets 20, and you have to be rolling downhill with your foot off the throttle with a tailwind to get 30.

And the other thing that irks me in the renewable energy business is hearing solar installers try to claim that your money is better spent on solar than wind. This is also bogus. There's truths and realities with solar PV too, in that it does not perform as advertised and deceptive ratings are used on panels. You meet very few solar installers who will address reality and actually show what you're going to get out of that PV array in the real world with the average hours of sunlight you get per day thruout the year at your site, and factor in less performance in hot weather when the days are longer, etc.. People put in a 5 kW solar array and it's just like a wind turbine - it makes 5 kW on one day in the middle of the winter when it's colder than hell, the air is clear and the sun is shining directly on the panels.

I always tell anybody who thinks solar or wind power is going to save them big money that they're way better off to spend their money on energy efficiency improvements in their home before putting in, or even considering, either solar or wind power. Do that first - THEN come and talk to me about a wind turbine - if you have any money left. When all is said and done, there are very, very few homeowners who have grid power who can justify a single penny spent on screwing even a single solar panel to their roof much less putting in a wind turbine, when they can buy cheap grid power.

And that's the realities and truth about either solar or wind.
--
Chris

[Ralph Day]

Chris has hit the nail on the head. I found almost all the things he's said to be true.

''When all is said and done, there are very, very few homeowners who have grid power who can justify a single penny spent on screwing even a single solar panel to their roof much less putting in a wind turbine, when they can buy cheap grid power.''

But trying to convince someone that their grid power is cheap is another story. No one thinks their utility bill is too low...yet. In 5-10 year's time they might think back to 2011 and wish for the bill they had then.

I have found the 1200kwhr per 1kw of pv a very close mark to aim for in pv. My microFIT 10kw system is producing right along that line so far. A full year or several will truly tell if that NRCAN number is factual. It's also really close for my house system. 2.1kw pv and we generally get from 2100-2400kwhr in a year. That's with batteries, so not all the available energy is harvested as would be done with a net meter/grid tied system.

So, if someone is considering pv then the 1200kwhr/yr per 1kw of pv is how to estimate production. Wind, another kettle of fish.

Ralph

[Chris Olson]

But trying to convince someone that their grid power is cheap is another story. No one thinks their utility bill is too low...yet. In 5-10 year's time they might think back to 2011 and wish for the bill they had then.


I didn't mention that specifically because it borders on conjecture. Some people have different perceptions of the cost of their utility bills. But for anybody who is thinking about solar or wind power, I tell them that chances are their grid power is cheaper than putting in either one.

BUT - if that person is like me and believes that energy is going to get more expensive, and/or would like to move off-grid and/or reduce their dependence on grid power by installing a backup battery system so they have power when the grid goes down - that person will then become my customer because he/she is spending the money for a different reason than saving money.

Any installers who try to sell systems, whatever it is, based on the customer getting a financial return by saving money on their electric bill is barking up the wrong tree at today's costs. Like I always tell them, you can just pay your electric bill, take the money you think you want to spend on solar panels, stick it in the bank and collect interest on it, and come out WAY money ahead in the end.
--
Chris

[Dan Lenox]

that person will then become my customer because he/she is spending the money for a different reason than saving money.

Well I think that there are *many* good vendors/installers out there that are trustworthy and honest, granted there are always those that are in it for a buck - but that happens in every category of consumer services.

I personally have dealt with our hosts here (Rob Beckers - Solacity) and I can say he is more than willing to discuss a persons needs/wants and give you a fair evaluation.

People 'go green' for many reasons, not just for the potential of saving money.

Dan Lenox

[Chris Olson]

I have found the 1200kwhr per 1kw of pv a very close mark to aim for in pv.


Ralph, it's very interesting that you mentioned the above. We have ten 123 watt Sharp panels on our house, which our solar installer told us should be considered a 1 kW array for battery charging, and they have averaged 3.24 kWh/day. Which is about 1,180 kWh per year. They have worked really good to fill in the gaps left by the wind turbines on days when the wind turbines don't make enough power to carry the loads.

I have three 3.7 meter turbines and those have averaged 8.05 kWh per day apiece. But like you say, wind power is another kettle of fish. With the wind turbines, if the wind blows hard I have to shut some of them down because I simply can't use all the power. Increasing my battery bank size to 4,360 amp-hours has helped to store some of it. But the 1 kW of solar power fills in nicely on those lax days. When we get a high pressure area that sets in the wind normally won't blow much for a few days while the sun shines.

As soon as we get a changing weather pattern the wind picks up out of the east or west and we get clouds so the solar doesn't work as good but the turbines are running nicely.

Putting in the solar has reduced my emergency generator run time to almost zero. I now only run the generator pretty much when I need to equalize the cells and desulfate my bank. Except for a few times in the winter when our power usage is really high and the output from the turbines and solar doesn't meet our needs. I'd like to reduce that to zero too because it's the worst time of the year to have to run the generator. But it would take a LOT of money - far more than it takes to run the generator - to do that.

At any rate, it's refreshing to see someone who has a realistic output expectation for a kW of solar power. We paid, IIRC, about $5,000 for our one kW of solar power with the panels and the Unirac mounting system that came with them. That doesn't include the breakers and panels and wiring. At the price of grid power around here they make about $126 worth of electricity per year. So if we had grid power the payback time on those panels would be about 40 years. We bought them from a dealer who's numbers on them made sense. Before that we talked to two different dealers that tried to convince us that those panels would make way more power than they actually do.
--
Chris

[Dave Turpin]

Increasing my battery bank size to 4,360 amp-hours has helped to store some of it.
Chris

Do you realize your battery bank is as big as many Diesel submarines'?

[Chris Olson]

Do you realize your battery bank is as big as many Diesel submarines'?

No, I didn't realize that, but it stores 29 kWh of power from full charge down to 50%. That's only enough power to run the average home for one day. It runs our home for three days with no input from wind or solar.

Dave, my battery bank arrangement is also rather strange. My incoming power is 24 volt while my inverters (8 kW total capacity) are 12 volt, with two of them running off a slightly larger half of the bank that carries the heavier loads, and the third one running off a slightly smaller half of the bank. I have a rather elaborate controller system that keeps the bank balanced.

So at 12 volt out, my bank capacity is 4,360 ah. At 24 volt in, the bank has a capacity of 2,180 amp-hours. However, the kWh capacity is the same no matter the voltage. I generally just float them during the day and dig into the bank at night or times of low generating system output to minimize charging losses, since hungry batteries waste very little power. I boil them once a week at 29-30 volts and desulfate and equalize them at 32.4 volts when required - usually about once every 4-6 weeks.

I don't know the voltage of diesel submarine battery systems. But I'm suspecting it's higher than 12 or 24 volt. So the amp-hour capacity might be the same, but with higher voltage the kWh capacity increases at the same ah capacity.

I guess I haven't "met" a lot of other off-grid folks on this forum. We live in a whole different world, with a totally different outlook on how things are done, than people who have grid power. I think for the most part, us off-grid folks tend to spend money on things that grid powered folks would find totally not cost-effective. But we don't live in a cave, cook over an open fire, carry a bone club over our shoulder and drag our women around by the hair.
--
Chris