The Truth About Small Wind Turbines

[Rob Beckers]

I've written a Web article that tries to inform those new to wind energy about the realities of small wind turbines (mostly the store-bought variety used for grid-tie, though some of the info applies to home made turbines too). It is meant to be neither a cheerleader for small wind, nor overly antagonistic, it simply describes the reality as I've observed it over the past years. The people reading this forum are likely much better informed than the average home owner that's considering a small wind turbine, so this may not be all that useful for readers here. It should help those in the market for a turbine to make a much more informed decision though.

Many of the readers here are also on the S-W-H list, I've posted the link on there before. It created quite a bit of discussion, and suggestions from people that helped improve the article. I am hoping this forum's audience will similarly help me improve the information presented in there. To cut a long story short, here is the link:

http://www.solacity.com/SmallWindTruth.htm

As mentioned, I very much welcome constructive feedback and suggestions on how to improve the article! Thank you in advance!

-RoB-

[bj]

   Definitely worth the read.

[Flux]

I haven't read it in detail but from first impressions it is spot on.Well done Rob.

[zap]

Nicely written article, very informative... and a "spot on" from  Sir Flux... what more could you ask for?!?

Proof reading:
"Since you are working hard to read this rather lengthy article, here is some entertainment. The 'intermission' if you like. So, put your feed up and enjoy the next picture..."

"There is very little power in low speed winds. The blade of a vertical or horizontal type turbine is equally good at extracting that power, thought with the vertical type the blades move against the wind..."
I think you meant "though", correct?

Nitpicking:
Consider adding a margin to the right side to make for a more comfortable read.

[electrondady1]

best to bear in mind that the author makes his living from selling and installing solar panels.
has designated anything under 30 ft. dia . as small wind .
(sorry danb , that 20 ft mill of yours is just a waste of time.)
the drag verticals i like to construct are  set aside as worthless "art" as they are only 20% efficient.
( here i was thinking 20% of an infinite resource was worth tapping into.)
silly me!

[gotwind2]

I have to agree, a very good and accurate read, I'm going to print it out (sorry environment) and re-read.
The 20% figure for sav VAWTs compared to HAWTs surprised me also, I knew they were poor but not that poor.

Well done to the author (Rob).

[SparWeb]

( here i was thinking 20% of an infinite resource was worth tapping into.)
silly me!

There are two audiences, and the article is only intended for one.  Rob's making the case for having realistic economic objectives when purchasing a wind turbine.  Rob doesn't mean to denegrate anybody's DIY project.  I think he deliberately avoids discussing DIY projects, too - it's not relevant to the point he is making.

[Flux]

With all these things there is more than one way to look at it.

If you are off grid then any power is a blessing. When you start to look at grid tie and other factors you can look at it from an environmental point of view, in which your ideas can be very different depending your take on green energy. You can look at it from a commercial view in which case it all comes down to whether you get a payback on your investment in a finite time.

The commercial take again depends on too many factors for there to be a definite answer. If you can get some form of hand out it may be very viable in circumstances where otherwise it would be totally useless. I suppose in this case it is someone Else's take on green energy and their interpretation of it.

The factors will also change depending on the competing forms of energy and how their cost and environmental impact is viewed.

A few years ago we shouldn't even be having this discussion, commercially small wind didn't exist and those who lived off grid just didn't have it either, wind power just got forgotten about when the grid got to most places.

I think much the same argument applies to solar, to some it is going to solve the world's problems, to others it is tinkering on the fringe of power generation. Ideas will change over the years.

The logic as I see it is that in a sunny area solar is worth investigating, in less sunny areas it depends on tariffs and hand outs and the seen to be green factor. Exactly the same is true of wind. In good wind areas it is worth considering but commercially it is happening on non viable sites even at the big level here in the UK because of the incentives, not because it is likely to produce much useful power. In areas where large machines are not viable then a few watts from small wind into the grid may or may not be useful or cost effective.

What does seem to be at stake in all these cases is people trying to sell schemes that will not deliver what they claim so it is not a bad idea to have the real facts before you are sold something.

If you live off grid and can get power from something 20% efficient then it will serve you well. If you could get the same from something 50% efficient then it all comes down to the cost of each way and whether you have to buy the beast or can build something. Investing large money into something inherently inefficient for commercial payback is another matter.

flux

[Bruce S]

RoB;
I think this line may need to be changed too. "By now you are probably thinking "why would these guys tell me the truth? They sell small wind turbines!"
Shouldn't it say something like why wouldn't they.....

Still reading, but I agree with Flux's last post.
Bruce S

[Rob Beckers]

Thank you everyone for the feedback! Some answers/responses:

Zap: Fixed the typos. Thank you! In defense; English is not my first language. Not even my second actually...  

Electrondady1: Actually most of my business' income is from wind and PV inverter sales. Both wind turbines and solar PV make up a tiny part of overall revenue. I didn't call drag-type verticals worthless, please don't put words into my mouth. I said they get about 20% of energy production of a HAWT for the same swept area. That statement is accurate, and if you are buying a wind turbine, and paying someone good money to install it, you better be aware of that number as it will make payback for grid-tie impossible (and use for battery charging difficult). They make fine projects for DIY where your objectives are entirely different.

Gotwind2: Yeah, I was surprised too when researching this. My strength is in HAWTs, I knew little about VAWTs. That 20% seems to be a realistic number for the better Savonius turbines (in comparison to a good HAWT).

SparWeb/Flux: As the very first lines of the article state it is intended for those interested in buying a wind turbine (and for most of those, paying someone to install it), and within that group, mainly for grid-tie use (though there is some info about battery charging as well). The purpose of the article is to provide counterbalance to the glossy sales brochures and installers with unrealistic promises.

For those building their own turbines the conditions and expectations are entirely different. Your cost basis is very different. You can fix problems yourself, and won't have to call in the installer every time it breaks. Maybe most importantly, for DIY there is no glossy brochure that makes idiotic promises such as "will provide 80% of your electricity bill" on top of a 40 foot tower.

-Rob-

[Antero]

This writing has some realistic and good points about windpower, but it gives wrong impression about windpower.

Where there is sun power and not good winds, sunpower is better.
But, if you have good winds, windpower is much better and cheaper than sunpower.

You can get a robust and reliable 2kw 3,8m windgenerator 575$ and 5kw 6m windgenerator 2052$.

These machines produce energy 24h day and night.

My energy diary 2kw 3,8m windgenerator;

http://fieldlines.com/board/index.php/topic,145065.0.html

But before all, the questionis is about human nature and energy politics in this matter.

If we really want something, we in Finland call this attitude in one word;  sisu = that means attitude, to not give up in any situation.

Its very odd, that there is no commercial and cheap and good windgenerator producers in Western or European world ?
Nothing to compare with Chinece Exmork with price and etc.

We have big companies and products.. millions, but not a good and cheap windgenerator, to average people to use ?  


Antero

[cardamon]

Antero,

You can get a robust and reliable 2kw 3,8m windgenerator 575$ and 5kw 6m windgenerator 2052$.

Just curious which machines are these you are referring to?  Homebuilt or commercial? and what currency are are using?

thanks

[electrondady1]

"Leaving the Savonius type VAWTs out (the type that looks like an oil drum cut in half - they have very poor efficiency anyway),"

not sure why the  need to leave them out since  it's one of the most celebrated configurations.
but it's your ramble so what ever.
it's quite possible to use things other than dirty stinking rotten dented  filthy and rusty old  oil drums,
 but have it your way,




you have this filed under idiotinstall  but i ask you, if installing a windmill of any type next to an ocean bluff, how else would one go about placement of the mill?
 one side is the ocean and there are small trees downwind of the mill.
if the thing is so bad why are the home owners allowing four more to be built on the same site?

 "The reality at this time is that if you want to produce energy, get a HAWT, if you want really good looking yard-art,that also makes energy get a VAWT."

it's been established the a drag mill produces something like 20% of betz
a Darius, something a little over 30% and a horizontal perhaps mid 40's

but 20% of 40%?
 i think they can do better than 8% of betz

[SnowGhost]

Antero,

You can get a robust and reliable 2kw 3,8m windgenerator 575$ and 5kw 6m windgenerator 2052$.

Just curious which machines are these you are referring to?  Homebuilt or commercial? and what currency are are using?

thanks

They are Exmork turbines. http://www.exmork.com/5kw-wind-turbine.htm
And the quoted price is USD.  Shipping is not included, but it's pretty damn cheap.

[Rob Beckers]

Antero: Yes, those are pretty cheap turbines. They are regular Chinese fare though, and my general experience with them (not Exmork in particular) has been very poor. Hopefully yours will do better. You are not the typical home owner that installs a wind turbine and that I target with my article though; you already rebuilt the machine, something the vast majority can't do themselves. You installed it yourself, and if I understand your diary correctly you got the tower really cheap. All those things are very expensive over here, making payback difficult.

More in general, and that is where my article is coming from, I would not know of any small wind turbine (commercial model, installed by a business, where the home owner is not taking it down themselves for 'maintenance' every year or so) that has been running for 10 years or more without major repairs. In fact, I would be hard-pressed to come up with examples of turbines that did 5 years without repairs. The money payed to an installer for a single repair will generally wipe out multiple years of energy production revenue. If there are turbines out there doing more than 10 years without major expenses they are very much the exception at this point.

electrondady1: Thank you for your feedback. Maybe I'm too harsh on the energy production of Savonius' turbines, I'll change it to "take 60% off, leaving just 40%". That makes for an overall efficiency of around 12%. I know the very best of Savonius turbines do 20% aerodynamic efficiency, however, my article is about efficiency of the wind to the grid. For a very good HAWT that is around 30% (despite their 40+% aerodynamic efficiency), and the experts believe my 30% is too optimistic, that 25% is closer to the truth.

Nicely painted oil drum halves can look quite spiffy! I'm sorry to see you believe them to be dirty/stinking/rotten/dented. 

I'm not sure why you feel the need to defend that WindSpire installation. Were you involved in that? In any event, it really is an excellent illustration of much that is wrong with the world of commercial small wind installations. I couldn't make this any better if I had made it up: Even if we correct for the camera angle, it is clear that those trees reach up to at least the bottom section of the turbine. Turbulence around that turbine will be atrocious, as will energy production. The statement in the article "that he's a little disappointed with the way it has been working" is telling in that regard (and it shows the owner is still in the denial phase).  That mast plus turbine is 23 feet high!! Hopefully I don't have to explain to you why that will work very, very poorly under the best of circumstances. The statement by the manufacture/installer that it will provide "up to 30% of the electrical needs of a single family home" is very misleading. The average US family uses around 900 kWh per month. Any idea what wind speed you would need to make this turbine produce 30% of that? The turbine is 80 sq. ft., even if everything works perfectly it will take nearly 6 m/s annual average wind speed through the rotor to produce that much. Do you really believe that will happen on a 10' tower? To get even 5.5 m/s at 10' height (not taking turbulence into account) you would need to live in a class 6 wind site! That just disqualified over 95% of the USA! The "no maintenance in 20 years" promise would kill me laughing if it wasn't just too sad for words. The way the article was written, the statements in there and the sheer innocence of the writer and turbine owners expressed, are prototypical of the state of affairs we got into with small wind turbines in North America.

As to my statement regarding VAWTs; unless I see proof to the contrary I will unfortunately have to stick with that (and I would really like to see commercially available small verticals that perform well, I think they look great!). Unfortunately, as an industry sector, the VAWT world has so far chosen to produce products that are very much overhyped and that greatly underperform.

-Rob-

[electrondady1]

i think your intentions are good rob and i don't have a problem with 95% of what you have said .
perhaps it's the nature of all new industries to take on a wild west, medicine show, aspect.
it's unfortunate that the general puplic can be hood winked into wishfull thinking and over spending.

i was just having some fun in describing those "old oil barrels".
poor mr. savonius ,
he used  barrels back in the 20's to show how easy wind energy could be harnessed and they have stuck to him like glue ever since.
i have no association with wind-spire product. or the installation in question.
i do  think the photo is misleading .
i have never lived near the ocean but those little trees at the base of buddy's windmill wouldn't stop the wind coming off lake Huron.

good luck

[ChrisOlson]

The statement by the manufacture/installer that it will provide "up to 30% of the electrical needs of a single family home" is very misleading.

Rob, I've found solar installers to be just as misleading.  I got 1,230 watts of Sharp panels on my roof.  If I would've believed what the solar installers tried to tell me I could've gotten way over rated power out of those panels.  On a good sunny day they'll make about 75% of their rated power averaged out over the hours of daylight.  They wanted to sell me a MPPT controller for $400+.  That will increase the output by 30% they said.  So my 1,230 watt panels would now average 1,200 watts for every hour of sunlight instead of only 920.

Oh, but put a tracker on the system and increase your output by another 30% they said.  Cool - so if I spent all this money on a tracker and a MPPT controller, now I'll be getting 1,560 watts average for every hour of sunlight out of a 1,230 watt array!

This magical 30% seems to be thrown around on a regular basis in the renewable energy business as a whole.

BTW - before I'll spend $480 or whatever it was on a MPPT controller, or several thousand on a tracker, I'll just spend $700 and screw a couple more solar panels to the roof.  That I KNOW will increase my output by 20%
--
Chris

[Rob Beckers]

Rob, I've found solar installers to be just as misleading.  I got 1,230 watts of Sharp panels on my roof.  If I would've believed what the solar installers tried to tell me I could've gotten way over rated power out of those panels.  On a good sunny day they'll make about 75% of their rated power averaged out over the hours of daylight.  They wanted to sell me a MPPT controller for $400+.  That will increase the output by 30% they said.  So my 1,230 watt panels would now average 1,200 watts for every hour of sunlight instead of only 920.

Amen to that Chris!
I've gotten into verbal arguments with PV installers here in Ottawa, at events where they have a stand, because they were promising double-digit returns on MicroFIT systems (we have a feed-in-tariff for solar here in Ontario). They work from dubious energy production numbers for PV, and obfuscate numbers to arrive at their returns. Needless to say I do not subscribe to that model of marketing; I've been telling people exactly what they can expect, with conservative production numbers. You can check my Web site, the numbers are right there, I'm not just bul$%$ing you for the sake of this forum. I'm sure it has cost me customers, because the competition makes it look so much more appealing, but I would rather have happy customers in the long run, that provide a good reference for my business.

The article in question here is about small wind though, and the big, big difference between solar and wind is that for those with some background the output from solar PV is entirely predictable for a given location (sure, installers can lie about it, but I can easily show they are lying). Solar modules have a rated power that is very, very narrowly defined by a standard. There is little or no wiggle room. Solar radiation for just about any spot on this planet is also very well defined for the long term (annual average). Barring the next explosion of Yellowstone volcano that makes predicting energy yield of solar a simple engineering exercise, and nothing like doing the same for small wind turbines. I know many PV installations that have worked reliably for 10+ years. Not so for small wind. There is no maintenance for solar PV, other than cleaning panels if you live in a dusty place with little rain. Very different from the reality for small wind.

I know people on this forum are small wind enthusiasts, and I am too (despite what some may think). The article is meant to provide realism to those considering investing a sizable sum of money into a small wind turbine installation. It counterbalances the marketing hype so common in the industry. It does not address DIY.

-Rob-

[dnix71]

An excellent read. I saved your page for reference.

I agree with ChrisOlson about solar panel ratings being fudged, too. The best I've ever gotten from my panels is about 2/3's of rated (with an MPPT). I consider 1/2 of rated power in direct sun about right.  The very standard by which the panels are rated is a known fraud. Direct tropical sun at 70F doesn't exist. With intense sun you get heat which lowers output. A real number would be direct tropical sun intensity at 160F. I you think 160F is too high, take a non-contact IR thermometer and go check some panels in direct sun and see what you get.

As for overrated wind http://www.ecrater.com/p/10347918/8-blade-250-watt-wind-turbine-generator  I won't even comment on this listing. "Otter" is a former eBay seller, that how bad his stuff is.  If you click on the full description link you will get some hilarious text about the so-called mill.

 

[ChrisOlson]

I agree with ChrisOlson about solar panel ratings being fudged, too. The best I've ever gotten from my panels is about 2/3's of rated (with an MPPT). I consider 1/2 of rated power in direct sun about right

I do get full rated power in direct sun - in fact, I've gotten over rated power at some times.  It depends on how clear the day is and how much of the solar radiance is blocked by dust in the air, moisture, or whatever.

But the point I was trying to make was that some solar installers have a line of BS that defies all logic.  While they were standing there telling me these "facts" I'm doing the math in my head and going, "What?"

There was only one solar installer that I dealt with that gave it to me straight and he told me that even though he'd like to sell me a $7,000 tracker, that I could spend that same $7,000 on extra solar panels and get way more power for the dollar than spending it on a tracker.  That's the guy I bought my panels from - with a non-tracking roof mount UniRack mounting system.  And the panels have performed just like he said they would.

The small wind turbine industry, like Rob points out, needs the same type of people as that guy I bought my solar array from.
--
Chris

[Rob Beckers]

I agree with ChrisOlson about solar panel ratings being fudged, too. The best I've ever gotten from my panels is about 2/3's of rated (with an MPPT). I consider 1/2 of rated power in direct sun about right.  The very standard by which the panels are rated is a known fraud. Direct tropical sun at 70F doesn't exist. With intense sun you get heat which lowers output. A real number would be direct tropical sun intensity at 160F. I you think 160F is too high, take a non-contact IR thermometer and go check some panels in direct sun and see what you get.

Dnix71, this is getting a bit off-topic, but it is important: Yes, PV module output is very dependent on temperature. That does not make the standard for PV output any less valid though; it states that the output power is measured at 25C with a radiation of 1000 W/m^2. All the PV module spec sheets have coefficients on them for derating power output vs. temperature, and the PTC vs. STC numbers try to account for that too. To predict energy production for a location vs. panel orientation and tilt, the 'trick' is in how one derates the full output numbers to account for the local climate. This will be different for different locations, for our area (Ottawa) the right number happens to be 0.75 (to be on the conservative side). If you live in a warmer climate than ours, that factor will likely be smaller.

For example, we have 4.17 average annual solar hours per day of 1000 W/m^2. The optimal fixed tilt for our climate (taking cloud cover into account) is around 37 degrees. For 1 kW of PV modules facing exactly south, at 37 degrees tilt, theoretical energy production would be 4.17 * 365.25 = 1,523 kWh per average year. Because of losses due to inverter, wiring, dust, and especially temperature in the summer months when most energy is produced, the actual energy production is much closer to 0.75 * 1523 = 1,142 kWh per year, and that is for the average poly or mono silicon module. Most are close to this, some do better (such as Sanyo modules). I myself use the number 1,140 kWh/yr/kW. That has then to be corrected for the actual angle and orientation of the modules, and the effects of shading (if present), I do that too before telling customers what to expect.

What I'm saying is that this is not guesswork, but utterly predictable. That factor or 0.75 is not a magic number either; it could be measured through datalogging, it can also be calculated by running a computer simulation that takes actual climatology (cloud cover and temperatures etc.) into account, with a model of a PV module. For Canada this has been done already by National Resources Canada (NRCan), and they publish the data online: https://glfc.cfsnet.nfis.org/mapserver/pv/municip.php?n=1408&NEK=e

To tie this back to wind: Right now manufacturers don't even agree on the wind speed for "rated output". On top of that, many of the published rated output numbers for wind turbines are outright lies or educated guesses by those manufacturers. For solar PV the rated output is actually measured very carefully for each individual PV module (they get flash tested and sorted according to output). A world of difference.

By the way, I have a IR-thermometer and usually measure a temperature differential of 35 degrees Centigrade (almost 70F) between air and module temperature for roof-mounted modules (with a 5" gap for air movement underneath), at 25C air they measure in at 60C. Works both ways though, right now it is -10C outside (about 10F), blue sky, and boy are my panels cranking out power! 

-Rob-

[ChrisOlson]

What I'm saying is that this is not guesswork, but utterly predictable.

Rob, It's actually utterly predictable for wind systems too.  It's just that turbines are rated wrong.  The whole system of rating wind turbines by watt output @ 28 mph (or whatever) should be abolished, and rate all turbines by kWh output instead, at real wind speeds like 12 mph.  Or at least provide a chart like Jacobs does that shows what the turbine can develop under ideal conditions on an annual basis at various wind speeds:
http://www.windturbine.net/products.htm

WTIC has a note down below that says the values in the chart are based on a theoretically perfect installation.  But even so, the output for a 31-20 is conservative because I've seen 31-20's make 34,300 kWh/year in Class 2 wind zone installations if the installer does his homework and puts the turbine on a 120 foot tower that takes maximum advantage of prevailing wind.

Your article applies to all wind turbines, just not small wind.  Few large utility-scale turbines develop their full "rated" power more than 5% of the time.  It's all in how the machine is marketed to the people who don't know any better.  An example is the Vestas V82 installed at St. Olaf College in Northfield, MN.  That turbine is rated at 1.65 MW but the day my wife and I toured the turbine installation it was only putting out 640 kW because the wind wasn't blowing at 27 mph that day.  And the wind rarely blows at 27 mph thru that turbine's rotor.  That turbine hasn't developed anything close to the power that the people at St. Olaf College thought they were going to get out of it, since it was installed, because Vestas over-rated it for that wind site.

You can read here about all the hype on that turbine and how it puts out 1.65 million watts peak and how it was expected to develop 5-6 million kWh per year at that site.
http://libmanwind.com/files/41178183.pdf

They've only gotten half of that out of it because the average wind speed where that turbine is installed is 12.6 mph, not 17 as was "estimated" when it was installed.

Your article on the truth about small wind power applies to ALL wind power machines, from the smallest to the largest.  Taking it to an extreme, manufacturers could rate a 3 foot turbine at 10 kW in a 100 mph wind, market it that way, and don't you know some people would buy that turbine then wonder why it don't put out 10 kw.

And none of this makes a wind turbine any less useful to generate power than a solar array.  It's just that a wind turbine has to be represented by what kind of power you're going to get out of it on a more realistic level.  Here where I live, dollars are much better spent on a wind power installation than solar for somebody who wants to generate their own power.  It's all about cost/kWh.
--
Chris

[dnix71]

This is a little bit off-topic, but what is 'Exmork' in Chinese? When I see the name that's not what I think of.



Fly and Be Free!

[ChrisOlson]

This is a little bit off-topic, but what is 'Exmork' in Chinese?

Ask Mindy.  She might know.
--
Chris

[Rob Beckers]

ROFL! 

[fabricator]

Mindy was hot! Nano, nano.

[ChrisOlson]

Mindy was hot! Nano, nano.

Space Aliens, being so much more advanced, don't hang out with ugly babes.
--
Chris

[GoVertical]

Greetings, does the article mention that wind blows at night? . Being to negative may be a disadvantage.  May be the article should include a large section how the technologies working together can create a better system at a lower cost.     

[ChrisOlson]

Greetings, does the article mention that wind blows at night?

I never read that in it, but speaking of that, my wind turbine generated 4.3 kWh last night in total darkness.  It made another 4.6 kWh today in a snow storm during daylight.  The solar panels generated a grand total of .01 kWh.

I got a lot less money in that wind turbine than I got in them solar panels.
--
Chris

[GoVertical]

Is that 20% or 30% better? Sorry, cabin fever has set in.
 

[fabricator]

you have this filed under idiotinstall  but i ask you, if installing a windmill of any type next to an ocean bluff, how else would one go about placement of the mill?
 one side is the ocean and there are small trees downwind of the mill.
if the thing is so bad why are the home owners allowing four more to be built on the same site?

Because as the owner states, "Performance has been dis sappointing" So they need three more of the twenty thousand dollar units to do what one HAWT on a properly sized tower would do.

[ChrisOlson]

Is that 20% or 30% better? Sorry, cabin fever has set in.

I don't have one of them fancy data loggers so percentage is whatever I want it to be   

I only know that if I had to depend solely on them confounded solar panels for power, it wouldn't be good.  There's very few days in the year that the wind turbine don't run and make power.  Them solar panels, OTOH, for about half the year, are only good to help keep snow and ice off the shingles on the roof.

--
Chris

[Antero]

The headline of this writing;   "Truth about windpower..

That tells a lot.

The truth in my case is, that, I get all my energy need, with windpower.
2kw dia 3,8m / 12,4ft windgenerator. Price 575$.
You can get 9-18m / 30-60ft tower complete with wires and all mounting materials under 500- 1000$.

Rob Becker; "you already rebuilt the machine, something the vast majority can't do themselves. You installed it yourself, and if I understand your diary correctly you got the tower really cheap. All those things are very expensive over here, making payback difficult"

Did you read my story ?
Read it again !

I have not rebuilt this machine ?

I have dismantled it to get pictures about the inner structure and allso practised same time how this machine is built and how can you
service it and how for example to change the bearings, which was no needed etc
I have shared these pictures and knowledge about the structure etc to many forums after that.

 
The truth ?

Antero