site assessment

[Ethan Brush]

A two part question here: First I am looking for some recommendations on a wind speed data recorder/anemometer for site analysis. Also, I would love to hear others' opinions and philosophies on site analysis. Obviously there are several different ways to evaluate a site, i.e. common sense, wind maps, looking for signs on site, but in practice how long do you record the wind speed for? In theory a year would be good, but in reality I dont think anybody has dozens of anemometers to put in the field and super patient customers. Curious what other have to say.

[Rob Beckers]

Hi Ethan,

It is unusual for prospective small wind turbine sites (10kW and under) to install an anemometer and data logger. The main reason is cost, it can be close to the price of just installing the wind turbine. Secondary is what you point out: To get remotely useful data you would have to leave it up and logging for at least a year. Seasonal variability is such that summer data is not going to tell you a whole lot about winter winds and vice versa. Even year to year variability is such that a single year's data can only go so far in predicting average wind speed. When an anemometer is installed is is normally just a single one, at proposed hub height, so it only tells you what to expect at that exact place.

Wind maps have gotten better, and they are based on multi-year data (in essence they use the same software that is used for weather prediction and climate modeling, by ingesting 're-analysis' large-scale data and running the model to generate winds at multiple levels). Spatial resolution is not great, especially for contoured sites. Still, it is a useful guide of what to expect. With most small wind turbines so close to the ground (100 feet up is really not very high as far as wind is concerned) much comes down to following proper siting rules, and even then studies have shown it is a good idea to underestimate production. If anyone is interested, I've written a bit about wind turbine site and height selection (http://www.solacity.com/SiteSelection.htm).

-RoB-

[Paul Bailey]

See attached Mick Sagrillo site analysis for wind.

Paul:oh:

[Brian McGowan]

For what it's worth, I went through the same debate with myself. In the end I got a small 5' windturbine for only slightly more than the price of a weather station that would record data. I put it up as a test and have since decided it was worth doing and should be up twice as high as I have it. I won it on ebay for $355.00 so it was cheap enough for my test. I could not build one this inexpensively. It is made out of a GM alternator with a permanent magnet rotor and 6 blades. I consider it to be the sledgehammer of windturbines. Maybe not the most efficient unit but if the wind blows and it spins it will make good power.
Here is what I got. If it works it is cheap enough to replace with a good one. If it doesn't work you didn't lose very much and you can get the pully and fan arrangement and use it as a PMA hooked to an engine or something or just sell it used on ebay.
Item number: 260393908876
http://cgi.ebay.com/BREEZE-LOW-WIND-12-24-48-VOLT-TURBINE-GENERATOR-400W_W0QQitemZ260393908876QQihZ016QQcategoryZ12183 7QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Here are pictures of the installation on the home page and if you go to the windturbine page you can see my buildup.
http://home.comcast.net/~bigvid

Once again I only put this up as a test. Mostly a test of the neighbors and the township but also to see if it's worth doing for real.
Good luck,
Brian

[Ethan Brush]

Good info, thanks for the replies and links guys. I had considered the cost of installing a monitoring station and yes it is certainly a concern. A friend of mine has a large silo on his site and I had thought about installing a few sections of tv antenna mast to the side and putting an anemometer on that. A few keystrokes in google could confirm this, but I recall seeing a monitoring station/recorder for around $200, so in this case the cost would be low. There are those nice sites where you know the wind will be good and others that seem iffy, despite the client's opinion that "it always blows like a bastard here....."

[Rob Beckers]

... despite the client's opinion that "it always blows like a bastard here....."

To add to that: Every single (potential) customer I have ever met would be convinced of the above. They all claim the wind is always blowing where they live. Then you look it up in the wind atlas, nearby airports and such, and it turns out they have less than 4 m/s (meaning, next to no wind). Now, the wind atlas may be wrong in places, but it won't be off by by that much. Humans are very good at remembering the stormy days, and forget all about the many days without wind. Human nature...

-RoB-

[Ethan Brush]

Ok so let me be the devil's advocate here. Installing a wind speed recorder need not be expensive, I would say not even close to the cost of installing the turbine. At the two sites I am looking at now, I could intall a anemometer in two hours with $40 in materials. One has a silo, and the other has tall spruce trees than could both have a few lengths of radio shack tv mast bolted to them with an amemometer on top. And to continue with my devil's advocacy, couldn't recording for less then a year still be valuable? It seems than rough approximations for seasonal variablity could be established that are typical of most sites, for example something like "during summer months X% of sites will have average wind speeds Y% lower than in the winter months". Then the values obtained could be corrected for a annual average. I suppose that could easily be proven or disproven by looking at the records for some sites that have been monitored for several years. I guess my point is that often more data is needed to evaluate a site - the articles you guys posted are great, but they mostly just deal with obstructions and there are many sites that dont have any obstruction issues but are not on a mountain top, but not in a valley either......