2015 Wind Turbine Buyer’s Guide

Why, Where & How to Do Wind Electricity
Intermediate

Inside this Article

Tall tower
Crane and tower
For best performance, wind turbines need to be installed atop tall towers, which gives them access to less-turbulent winds.
Tall Tower
Towers need to be tall, tall, tall.
Tower top maintenance required
Wind power systems require regular maintenance, which usually means routine climbs to the tower top.
Tower in open terrain
In flat, open terrain, a shorter tower can suffice, although it still needs to be high enough to put the turbine in “clean” winds.
Tower in tree-lined terrain
In rugged terrain and/or trees, towers need to be significantly taller than surrounding obstacles.
assembling the tower
The turbine is only part of the system mechanics and cost.
Pouring massive tower footings
The larger the turbine and tower, the more infrastructure involved.
Tall tower
Crane and tower
Tall Tower
Tower top maintenance required
Tower in open terrain
Tower in tree-lined terrain
assembling the tower
Pouring massive tower footings

Making electricity with the wind is not easy. As seasoned wind-energy installers with decades of experience, we—as well as thousands of others who live with home-scale wind turbines—tell a challenging tale. And the small wind industry today reflects those challenges, with long-established companies struggling and going under while the cost of reliable solar-electric modules continues to drop. If you think you want a wind-electric system, first think smart, then realistically.

Done well, residential-scale wind energy can provide clean kilowatt-hours in a very satisfying way. But because of the characteristics of the wind, wind systems have several strikes against them:

  • Tall towers are required for meaningful production
  • Reliability and robustness are hard to come by
  • Compared to solar electricity, the cost per kWh can be high
  • Qualified local installation and maintenance help is difficult to find
  • Hype, misinformation, and outright scams are too common

This article will help you sift through the rhetoric and numbers, and make a wise decision about whether or not to tap local wind energy. If you decide that wind is right for your site, we want to help you understand how to make it work for the long term.

Why Wind?

First, we suggest you get a handle on your motivations, needs, and situation. These will help determine whether a residential wind-electric system makes sense for you. People choose wind energy for several reasons, including:

  • Environmental concerns
  • Decreased cost of energy
  • Desire for independence
  • Fun and interest

Each of these motivations—and combinations of them—will lead to different choices. Be realistic about why you are considering wind energy and make sure the actual results satisfy your expectations and goals.

When installed correctly in the right location, a residential wind-electric system can produce cleaner energy than North America’s utility grid, which is dominated by coal and other dirty energy sources. But a wind system needs to make significant energy (kilowatt-hours) for years or decades to make environmental and financial sense. Otherwise, you could end up spending a pile of money on an unproductive wind energy system—and still be shelling out dollars for that dirty coal energy you’re using now.

Scrutinizing your real cost of wind energy is crucial if your primary goal is to save money. Many wind-electric systems are installed with unrealistic financial and durability projections, and end up generating energy that is more expensive than the local utility grid. A low cost per kWh requires a productive and long-lasting wind-electric system.

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Comments (7)

sinnadurai's picture

For small windturbines what kind of AVR is used.

Jim Norman_2's picture

Good article. Couple of comments from my experience.
As opposed to solar PV, which is a passive system with no moving parts, wind is a mechanical system and so susceptible to wear and tear and mechanical failures. There is no getting away from that fact. It is going to be more expensive to maintain. Plan for that when designing your system and selecting the tower.

The advantage to wind in the past was that the initial capital cost per installed watt could be lower. With the plummeting PV module prices, that advantage is largely gone. Add to that the hype and overstated performance and durability claims you spoke about, and it's been a tough time for small wind.

You are absolutely correct. Knowing the average wind speed (and, to some extent, the distribution) is critical in assessing the viability and payback. Unfortunately, a lot of folks are reluctant to take the time (preferably one year) and expense of conducting a wind study. So decisions are based on personal observations.

The two most consistently common errors I've seen through the years are under-sizing the battery bank in off-grid applications and installing a wind turbine tower that is too short. A long time ago I did a simple cost-benefit analysis based on tower height. Looking solely at wind shear (assuming flat, relatively smooth surface), the optimal tower height was 80 ft. There were still performance gains to be made with taller towers but the associated costs started offsetting a larger percentage of the gains.

As with many suppliers/installers who are in it for the long haul and care about the customers they are serving, I have spent a lot of my own money trying to make lemonade from lemons. So a word of caution - take a hard look at the history of the turbine and the reputation of the mfgr. There are very few turbines that have withstood the test of time. But there are some.

A major issue you want to address regarding the turbine is the method used to control rotational speed. Since the power is the cube of the wind speed, you want the turbine to be able to effectively capture power from wind events, while also protect itself from excessive winds. Not an easy task, and one that turbine manufacturers wrestle with.

There is a place for small wind. In off-grid systems, a combination of wind and solar can produce a more balanced power production mix. With both off and on grid, if you have a viable wind resource, a good turbine, and a well designed (and installed) system, it can make economic sense. And they are fun to watch. I have spent hours watching and studying wind turbine performance.

Ian Woofenden's picture
Thanks for your cogent comments, Jim. Folks should approach small wind with eyes _wide_ open. A couple of cautions: • Comparing PV and wind by rated wattage is not sensible. PV has a predictable output based on rated wattage if you know the peak sun hours and the appropriate factor. Wind rated wattage is at peak, and since wind is a cubic resource, there's no easy way to predict energy (kWh) output from peak wattage of a wind generator. You really need the average wind speed on the site and good data on the specific machine. So comparing "cost per installed watt" just isn't a sound comparison. What's needed is comparing cost per kWh delivered over time. • Short towers are absolutely the most common mistake in small wind. But be careful with statements about "optimal" tower height. It very much depends on the terrain, the machine, and the application. If money isn't an object, higher is always better. And really, instead of talking about optimum total height, it would be wiser to talk about height above nearby obstructions. A common rule of thumb is "at least 30 feet above anything within 500 feet." And I think the "at least" part is the most important part... • I'm actually an advocate of small battery banks for off-grid systems. Batteries have a cost, both financially and in energy losses. A larger bank has larger losses, and takes more energy to keep fully charged. It also presents a temptation to overuse the system, and then has the major drawback of being harder to bring up to full charge. Most off-grid systems have back-up fuel-fired generators, so the significant question becomes, "How often will I need to fire up the generator?" I prefer a modest battery bank, while taking the leftover cash and investing it in more generating capacity. This strategy works at my homestead, where most days I have a surplus, because I have substantial wind and PV capacity, while maybe 15 times a year I need to run the generator. A larger battery bank would not change this scenario. Regards, Ian Woofenden Home Power senior editor
Rick Zuber's picture

I'm not a fan of large battery banks as batteries are a reoccurring expense. I would rather size the system to hold overnight at about a 50% DOD and take the additional money and buy solar panels. On a day of heavy cloud cover panels at this latitude (60.5 N) produce about 10% of rated power between the longer days of the equinox's. I imagine that is much higher as one moves further south. So if I need 2KW to charge a 400AH 48V battery bank at a C/10 rate I will need a current limited 20KW array to be virtually totally free of generator backup. With today's solar prices that is not outrageous. People commonly spend way more on new vehicles that do not have a 25 year warranty.
On another note I have a 2KW WhirlWind turbine on an 85' tower here at our homestead. They are not known for their longevity but I have had this up and running since 1986 with little problems. I made some modifications early on which has contributed greatly to the long life. One of it's greatest design assets is that it turns 90 degrees out of the wind when it exceeds 35 MPH. Sure it will limit output in storms but it survives them. I can leave here on vacation and never worry about a big storm coming through. In this day and age of electronics it is unreasonable to rely on manually shutting down a wind turbine because of a storm, but that is how most small turbines are designed. Also I suspect there is a way to modify these WhirlWinds to govern the RPM's with an electromechanical device that counts the RPM's, (maybe a hall device) feeds that info back to electromagnets that align the yaw drive fan into the wind only enough to produce designed RPM's. I tried to contact Elliot Bayly to discuss this with him and found out he had just passed. This is my project #4,375. Some day

Ian Woofenden's picture
Hi Rick, I'm with you on modest battery banks. It's important to remember that batteries are not a source of energy, but are actually loads (while being storage devices, obviously). And it's great to hear of your long-lived machine. It IS possible, with attention and care. Overspeed control is crucial, and a machine worth buying should have a fool proof system of shedding/controlling high winds. Regards, Ian Woofenden Home Power senior editor.
Rick Zuber's picture

I am glad to see an article on wind power that tells it like it is. Way too many machines were installed in my area on short poles that will never pay themselves off.
One wind machine that shows great promise is the WindSpot, made in Spain. They are very well built and heavy machines and run at very low RPM's. Something like 250 RPM for the 3.5KW. Swept area isn't the greatest but it seems to be adequate. They are pricey.

Ian Woofenden's picture
Thanks for your comments, Rick. There is a general lack of education about the reality of wind energy, so many people are susceptible to hype and worse. While some of us pursue wind energy with money not as our highest value, getting real about the return on investment in advance would eliminate much of the disappointment. One wind wag used to say that "second time wind turbine buyers want the most expensive machine available", which is another way to say that reliability and long-term production will be costly up front. I encourage all readers to not look for an easy answer, and to expect to pay a substantial price for a wind-electric system that will serve well for the long term. Regards, Ian Woofenden Home Power senior editor
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