Brian Antonich

Minneapolis, MN

Hi Trudy. When determining if you have enough wind to put up a small wind turbine, how much and what types of wind data are most useful?  Do you know where one can find useful wind resource data with out spending a lot of money?  How much wind is not enough, just enough, or more than enough to have a successful small wind project?

Brian,

If you can find it, time series data from a location near you is the most useful.  However for small wind turbines (10 kW or less) you can get by with the on-line wind maps.   When using the wind maps, be advised that they assume a well-exposed site.

I recommend starting with the on-line wind maps available at:

http://www.eere.energy.gov/windandhydro/windpoweringamerica/wind_maps.asp

There is also an interactive zoom wind atlas of the western U.S. at:

http://www.energyatlas.org/

A number of other websites provide wind speed data:

The US Renewable Resource Data Center provides information on wind data at http://rredc.nrel.gov/wind.

The University of North Dakota Energy & Environmental Research Center (EERC) has time series data for the upper Midwest and the northern & central plains. 

http://www.undeerc.org/wind/

The website www.weatherbase.com provides monthly average wind speed data for many cities around the world.

The Windustry website maintains a list of US wind data resources at www.windustry.com/resources/windmaps.htm.

The US National Climatic Data Center provides monthly average wind speed data for many US cities at www.ncdc.noaa.gov/ol/climate/online/ccd/avgwind.html. To convert from mph to m/s, divide by 2.25.

A handful of states have databases of time series data.

You can also check with the nearest airport.  Due to their location in sheltered areas and to generally poor anemometer placement, airport data generally gives a low-ball estimate of the wind resource.

Finally, Mick Sagrillo has written an excellent article on site analysis that includes home brew methods for estimating the wind resource at a specific site.  The article is at

www.homepower.com/files/windsiteanalysis.pdf

As to how much wind is necessary for a small wind project that depends mainly on the type of project, and how important financial performance is to you.  What follows are some very rough rules of thumb. 

For off-grid projects, where your alternative is a grid extension, a wind turbine could be economically added to a hybrid renewable energy system in areas with average wind speeds as low as 8.5 mph @ 20 meters above ground level (AGL) (High Class 1).

For an on-grid system, a site with a minimum average wind speed of ~10 mph at 20 meters AGL (Class 2 or better) is worth further study.  If financial performance is important, you probably want a minimum average wind speed of 12 mph at 20 meters AGL. (Class 3 or better)

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Michael Weber

Minneapolis, MN

Could you define what "small wind " means in terms of kW capacity? Also, how would a small school board or rural county in MN get started on developing a wind project--please address financing issues as well.

Michael,

Small wind turbines are defined, somewhat arbitrarily to be turbines equal to 100 kW or less.

My recommendation for getting school board or rural county to consider using a turbine for their school would be to research what has already been done.  Through our Wind Powering America projects, we think that working with schools is an ideal way to get information out within rural communities.  We have worked with Michael Arquin www.kidwind.org to develop standards based science curriculum for middle and high school science teachers.

We have seen several schools in Iowa use wind energy to help displace the use of electricity and in one case provide an opportunity to fund classroom computers. 

The best source for you would be to work with Windustry, they have been working on the use of turbines in a ‘community wind’ model that has specific financing strategies and since they are located in Minnesota they will be very knowledgeable about existing policy and strategies.   I would defer to them and ask them about specific financing opportunities.  They are holding their next Community Wind Conference in Iowa the beginning of March, which would present you another opportunity to learn about wind and schools.  To find out more about the conference and to register visit http://www.windustry.org/conferences/march2006/default.htm

You can find an article on the Spirit Lake school project at: http://www.eere.energy.gov/windandhydro/windpoweringamerica/docs/schools.doc. 

Here is a link to a presentation given by Tom Wind of Iowa at last year’s Wind Powering America state summit meeting.

http://www.eere.energy.gov/windandhydro/windpoweringamerica/pdfs/workshops/2005_summit/wind.pdf

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Mike Jacobs

West Concord, MA

Over the years, there have been a couple small wind turbine manufacturers that have stayed visible and active in the market, and many more that have made an attempt to sell small (under 12 KW) wind turbines but not made a successful business.  In your view, is the challenge one of engineering and production, or of adapting to the business conditions?

Mike,

The small wind business is fraught with business and technical challenges.  One example would be the Carter administration tax credits that did a lot to stimulate the use of consumer-owned renewables.  While these tax credits were in place there were about 35 small turbine manufacturers in business but once the tax credit policy expired, it created a very challenging business environment for small turbine manufacturers and consequently only about 3 companies are in business today, Bergey Windpower, Wind Turbine Industries (Jacob’s turbines) and then Southwest Windpower (This was a company that started in the early 90s and so they weren’t around during the Carter tax credits.).

So policies dramatically effect the small wind business and when they decline the US market nearly vaporizes.  Starting in 1998 in California, there began to again be good incentive policies for small wind turbines and now there are numerous states and utilities that offer compelling incentives for small wind.

At the same time, the small wind manufacturers have the challenges that all small businesses have, making payroll.  It is very, very difficult if you are manufacturing any product and from month to month you may sell no products or many products. With that type of business environment, how do you stay in business?  The answer for Bergey Windpower was to sell their turbines outside the US after the expiration of the federal tax credits.  The other part of the equation is to continue to improve your product through incremental engineering, while this is possible on some levels, when cash flow is a problem you can only do low risk, low cost improvements.

At this point, there are a number of small turbine designers who have good designs and are trying to get into the marketplace.  The Department of Energy has helped them through their cost-shared competitive procurements.  Those companies selected have worked to develop their designs and move toward the market by manufacturing turbines.  Bringing a small turbine to market is a huge financial, engineering, and manufacturing challenge.  There are other inventers who have been trying to do this on their own without government funding or assistance, creating even more of a challenge.

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Nick Nichols
La Crosse, WI 

Even though plug-ins are not quite here yet, it's my understanding that they will be soon. My wife and I like to be on the cutting edge of sustainability.  How big of a turbine do I need to recharge a plug-in hybrid overnight?

Facts & Assumptions 

Size of battery bank (2004 Prius): 1.3 kWh  (6.5 Ahrs @ 201.6 volts)

Assume 30 miles per day

Assume 0.3 kWh/mile

(from Calcars fact sheet www.calcars.org/priusplusfactsheet-v1.12.pdf)

Wind Resource at/near La Crosse: 10 –12 mph @ 30 meters (Wisconsin Wind Map)

Assuming you could plug in a standard Prius (you can’t), and assuming the car is plugged in overnight for 12 hours per day, you would need your wind turbine to generate 1.3 kWh while the car is plugged in, which is equivalent to 2.6 kWh per day.  (This implicitly assumes that the wind resource is constant over the day.  This is usually a bad assumption, but I make it so that I can continue the analysis).  Given the wind resource at La Crosse, a small wind turbine in a well-exposed location will have a capacity factor on the order of 15%.  This means that the wind turbine average production will be (very) approximately equal to 15% of its rated power.  So, your desired wind turbine size is: 

          2.6 kWh/day / 24 hrs/day / 0.15 = ~ 0.7 kW.

So you would want a 0.7 kW wind turbine.  Of course due to fluctuating winds, some nights the turbine would produce more energy than is needed, other nights, less.  The turbine would also produce an average of 0.7 kWh electricity during times the car is not plugged in for use for other purposes.

To continue the analysis, lets assume you drive 30 miles per day.  To go all-electric you would need a battery bank storage capacity of 9 kWh (0.3 kWh/mile x 30 miles).  In this scenario you would need a wind turbine to produce 18 kWh/day, leading to a turbine size of:

          18 kWh/day/24 hrs/day/0.15 = ~ 5 kW.

There are aftermarket kits in development for the Prius that include an external plug and a larger capacity battery bank.

One last note.  It would be wise to ensure that the wind turbine electricity could be used by another load, such as your house.  This gives you a use for the electricity produced by the turbine while the car is not plugged in or after the car’s battery bank has been fully charged.

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Phil Schmidt

Trinity Products, Inc.

Ofallon, MO

I am a monopole fabricator for small wind.  I have heard the word "harmonics" a few times in regards to monopoles.  Can you explain what it is and how to prevent it? Also, I have programs designed for fabricating billboards, sign poles, and cell towers.  They take in account for the square foot area of the face of the signage which then sizes the tower.  How can I use this program to size the towers for turbines?  Or, turbine blades vs. a fixed 10' x 10' billboard lets say.

         Thank you.

Phil,

Small turbines operate in a variable speed mode and through their normal operation they may hit resonances or vibrations that can cause problems for the structural support including the tower and foundation.  Your monopole tower would need to avoid the resonant frequencies that turbines operate through and those frequencies will vary from turbine to turbine.

I’m not sure how to relate a sign and it’s size to the operation of small turbines, I’m sorry I can’t help you further.  If you are interested in working with a specific turbine, I’d advise that you contact the manufacturer and see if they are interested in working with you as a tower fabricator.