Wind-Electric History & Home-Scale System Design: Page 5 of 5


Inside this Article

The world’s first automatically operated wind turbine was built in 1888 by Charles F. Brush. It was 60 feet tall with a diameter of 56 feet, weighed 80,000 pounds, and had a 12 kW generator.
Two wrongs don’t make a right. Here, a Savonius rotor is placed at the center of a Darrieus to make it self-starting. But Darrieus turbines are inefficient and structurally flawed.
For overspeed protection, Bergey’s Excel 10 kW turbine features a pivoting tail and flexible blades, which twist to allow furling under excessive wind load.
A 41% increase in radius/diameter results in a doubling of swept area, and thus twice as much energy potential.
This Renewtech turbine is a tailless upwind turbine that uses electronics to yaw. Larger turbines are often better at obtaining both efficiency and durability, but that can challenge the budget of a homeowner.
This Pika Energy turbine is a classic three-bladed, tail-yawing, upwind turbine.
The Kingspan Environmental KW6, 6 kW turbine is a downwind turbine. Speed control is provided by a unique pitch-control system that relies on a string and two hinges at the blade root.
Wind power may seem like an easy solution, but adopters need to be ready for the logistics, infrastructure, and costs of both installation and maintenance.

Certification lends credibility to a turbine, showing that it has gone through a standardized testing process that documented the performance or ability to survive sustained high winds. Without the discipline of independent testing, manufacturers are prone to inflate predictions of energy output. Some manufacturers choose to avoid the expense and time of certification, and certification is not a direct measure of longevity in the field, which is more important than peak performance, and even energy output estimates.

The following organizations have been qualified by the Small Wind Certification Council: High Plains Small Wind Test Center; National Renewable Energy Laboratory; UL/WTAMU Advanced Wind Turbine Test Facility; Windward Engineering; and The Wind Energy Institute of Canada.

Rated power at 11 meters per second (m/s, 25 mph) is a standardized power rating that may be handy for comparison, but is not particularly useful beyond that, and can be deceptive.

Rated AEO (annual energy output) at 5 m/s (11 mph)  average wind speed is a standardized energy rating, and can be cautiously used to compare turbines—but won’t relate to your site unless you also happen to have a 5 m/s average wind speed.

Estimated AEO at 8 through 14 mph average wind speed is predicted energy production at wind speeds most common at residential sites. (Wind speeds of 14 mph and above are rare.) These are important specs because they relate to your specific site. Find out where these numbers come from for any machine you are looking at, and try to confirm them via multiple sources. The only energy production numbers worth dwelling on are the predicted energy for your site’s average wind speed. This specification also demonstrates the need for good average wind-speed measurement or calculations for your site.

Rpm at rated power identifies the turbine’s rotational speed and is a useful comparative number between machines of about the same rotor diameter. In general, lower rpm turbines are longer-lived, with less wear and tear and lower noise levels.

Governing system specifies the method of controlling overspeed, a crucial design factor for all turbines. High winds pack a punch that needs to be avoided—not absorbed. Without a reliable governing system, your turbine will sooner or later break—with it, it will continue to make energy during and after high-wind events.

Governing wind speed is the speed at which a machine is fully governed—protected from high winds and the overspeed conditions they can cause. A low governing wind speed is more likely to indicate a long-lasting machine. The “lost” energy of not capturing high winds is minor because high winds are a very small fraction of the wind energy distribution curve.

Cost typically includes turbine and controls, but look carefully at exactly what is included in each package—and what else you will need to make a complete system (review the “Total System” list).

Make a Sensible Purchase

Those with solid experience in the wind business look at “new” inventions that constantly reappear in the media and on the Internet, and shake their heads. Wind is a diffuse and elusive source of energy that can work well in very specific conditions. Most notably, you need winds that are strong and steady. To find them, you will have to put your turbine well above any obstacles in an open landscape.

Be realistic about size (see the “Wind Reality Check” sidebar). Choose a reliable, efficient design. This usually means a three-bladed horizontal-axis turbine—after a hundred years of trial and error, this design has been the most successful. New inventions that claim to work where there is very little wind are simply toys. If you expect them to defy the laws of physics and produce useful amounts of energy, get ready for disappointment.

Small wind turbines have many handicaps in comparison to the huge ones that are becoming commonplace. They do not have access to the strong, steady winds that are available up high where utility-scale machines run. Unlike PV systems, which can be scaled, wind turbines have an economy of scale. What small wind turbines do have in their favor is that they produce energy locally—at the site—and are useful on a residential scale. They also produce energy that complements solar-electric systems. It’s unlikely that they will provide competitively priced electricity other than in an off-grid situation. But for those of us who take pleasure in producing our own energy, they can be very satisfying.

Web Extras

“2015 Wind Turbine Buyer’s Guide” by Ian Woofenden & Roy Butler in HP167

“Ask the Experts: Measuring Wind Energy Potential with an Anemometer” by Brent Summerville in HP175

“Wind Energy Physics” by David Laino in HP161

“How a Wind Turbine Works” by Ian Woofenden in HP148

“Back Page Basics: Understanding Wind Speed” by Ian Woofenden in HP173

“Wind Power Curves” by Ian Woofenden in HP127

Comments (8)

mberdan's picture

Brandon, thanks for the insight, I hope I understand you correctly, when you say small, you are right this is a relative term. I hope my analogy is correct when I remember what my parents taught me. Save a penny every day, it may not look like much now, but 20 years from now it can be allot.
I am not really aware of any dedicated sites to what you may consider small wind. To me small wind is under 10kw, but others have posted under 100kw is considered small wind.
Other than what is available thru search engines and standard sites, such as SWCC, AWEA, CANWEA and European market or those companies selling small wind technology. It is hard to find, good data.
This is true for both Vertical and horizontal turbines.
Our process was many years of research collecting documents from hundreds of different university publications and then putting them together. Once we had that, the rest was developing a structure to be
structurally strong and support the loads as well as have redundancy.
Then years of testing and refining.
Many people who are working on this technology, tend to keep it to themselves. Why? many reasons I assume. I know we too kept our project in the dark for many years. Maybe it is my background in R&D
for Aerospace projects. Or just staying away from the negativity in bringing new technology to the market, especially if it can be disruptive. If you are very interested in Vertical systems. I believe in transparency and sharing where it can do the best for all. I have years of university data from many of the top research labs working on small wind. I would be happy to point you in that direction.
you can contact me thru our website.
Not sure if this answers your question.
Thanks Mike Berdan

Brandon2's picture

First-time poster here (I think!), and not nearly knowledgeable enough to offer much to the discussion. But I do have an observation that I hope others find useful, and a related question.

Every time I read about smallish-scale wind, vertical-axis, etc., it seems that it is said to not be viable. I get that. BUT, this conclusion always seems to be followed/backed-up by "large-scale" reasoning, such that there ends up being a disconnect between the topic itself ("small") and the reasoning that follows ("big").

It's as if, every time I "tune in" to learn real information and experience about someone using *small* scale wind to consistently/reliably do *small* things (charge a tablet for an hour's worth of use, charge a non-smart phone for a couple days of use) and live *small* for those days/weeks when the sun isn't's only a few sentences before the discussion diverges hopelessly into *big* ideas about *broad* viability and the *bigger* picture, etc.

A possible, sad irony here is that the heavy focus on the *grand* scheme and the vacuum of discussion it creates regarding truly small-scale, actionable / applicable light uses may actually in turn have a self-defeating effect on the *big* picture itself. It's as if the old adage has been flipped: we can't see the trees through the forest.

What I mean to say is, experts and experienced people seem to start by talking about "small scale" and, as I listen attentively, within only a few words begin talking about "big" concepts such as viability on a national scale, 10/20 year ROIs, carbon/energy input/output ratio efficiency, and getting a pole 500 ft in the air.

I'm interested in small scale wind, and vertical-axis. So, let's say this is my hobby. That is, I'm not so concerned about those aforementioned things as I am the joy of learning, exploring, and producing my own energy (a cell phone for a few days, maybe) without the utility company and in a manner that won't drive my neighbors next door to declare war between our households (noise in an urban-ish environment). I'm interested in sharing my *small* bit of what I learn with others, perhaps the kids around that might be inspired to later become part of a team that helps solve things on a *big* scale (but wouldn't have happened if we didn't value the *small*).

This isn't a criticism I suppose, but an observation. I value the various perspectives, especially those of experts and people with lots of experience. Perhaps it has to do, in part, with different opinion of how small is small.

It would be great to get more interviews and more real, in depth discussions and examples of truly *small* wind applications as I mentioned. Which leads to my question: is there a source I can turn to for good, consistent, accessible, in-depth and analytical-but-not-too-big-picturey information about truly small-scale wind?

mberdan's picture

Thanks to everyone for the response. I understand your opinions and agree in many ways. But as an engineer, the words spoken in the early 60's from JFK still linger in my mind.
"We chose to do this not because they are easy, but because they are hard" thanks Mike Berdan.

mansberger's picture

Great quote Mike!

mberdan's picture

Todd thanks for the reply. nonsense, I do not think so. I just witnessed
a university competition from AWEA last summer. 10 universities who are all testing new ideas, blade design, performance enhancements in both Vertical and horizontal. top winner Vertical axis turbine.
Yes as I mentioned there is a long way to go and improvements are moving forward. Materials and technology are letting the new breed of engineers explore both sides. I am not against Horizontal, as I agree they are the main standard and work well. Lets look at some aspects.
horizontal systems work well, they must be placed high off the ground to capture strong winds. RPM's tend to be higher , fatigue is greater at higher RPM, tip speed higher , noise level higher , so they tend to be placed further away from source, longer cable runs, bigger foundations. Great if you are a farmer or rancher. what about the Urban environment, people want to go green there as well. solar has made it's way in the Urban because of that. Vertical systems are a way to give alternative or hybrid solution in a more Urban environment.
As you have seen , yes there is still a ways to go to make Vertical systems work efficiently and produce power as defined. But it is those challenges that will eventually give us a break thru. We are all part of making this world a little greener, so lets work together before we just Bash ideas with out supporting the technology. I have been working on our technology for 10 years, testing , redesigning, testing , looking for new products and ways to improve performance. From this we developed the system we currently have. Our systems are in the market and working for many years. yes power production is not fully there but some of that is the Inverter / controller side. Try and find a high tech wind inverter, good luck. We have a dual Vertical system, which we try to combine the 3phase AC to DC output for the inverter to convert back to single phase AC. Solar has expanded to micro inverters and more advanced controllers. wind needs the same, but yet not available, so most wind companies have to develop and sell their own. we try to use off the shelf technology. so in short, Yes we have a ways to go, but we should not push the Vertical technology aside. As I still say, it has far more consumer growth options than Horizontal.

Todd Cory_2's picture
Todd Cory_2 (not verified)

"The vertical systems have allot more promise than the horizontal and the major down falls of horizontal systems that exist are lending the way to Vertical systems."

you might want to reconsider that nonsense:

mberdan's picture

I remember many years ago when hybrid and electric cars where just a twinkle and everyone said that it will never take off. small wind has been developed mostly by individuals and hobbyist. but those who seek to bring new technology to small wind, are on the up-rise. New technology and computer aided design with CFD capabilities are moving into the small wind industry. and Vertical axis systems are tacking hold.
Yes we still have allot of work to do, but the discussion of horizontal being the safe decision maker is irrelevant. The vertical systems have allot more promise than the horizontal and the major down falls of horizontal systems that exist are lending the way to Vertical systems.
my opinion anyway.

Michael Welch's picture
I don't think anyone with any knowledge said that about EVs. It's always been clear that we needed a better battery, and that those batteries were on the horizon -- but even with old battery technologies EVs made sense for a lot of us.

Much different with VAWT wind generators. As far as I can see, the only promise VAWTs hold is with **marketers** who eye the problems with horizontal axis turbines (viewed as cost, tower, birds, need for strong wind, and hassle); and want to be able to sell a machine because, after all, it is attractive for all the right marketing reasons. That's what marketers do -- create need to make sales, regardless of viability.

And engineers new to the industry jump on board because that's what engineers do: they believe they can find a technical fix for any problem. Even if there isn't one, it's their job to try and to make it seem possible. And, as long as there's a paycheck, to keep trying, no matter how fruitless the same efforts have been in the past.

VAWTs are not taking hold. They just haven't worked out, none of them. They sure look interesting, though.
Show or Hide All Comments