Under what conditions, if any, would it be desirable to install multiple smaller turbines instead of one larger turbine? In particular, I was thinking about two 10 kW units versus one 20 kW unit; and two 50 kW units versus one 100 kW. How far apart should multiple turbines be spaced?
Mark Malcolm • via e-mail
While it is certainly more cost-effective to install one larger turbine instead of several smaller turbines, there are a variety of reasons why someone might want to install multiple turbines. My company has a number of multiple turbine installations in Wisconsin, as well as a variety of reasons why they were installed:
For horizontal spacing, 10 times the rotor diameter is a reasonable distance. The utility wind industry uses 7 to 10 times if the turbines are downwind of each other in the prevailing wind direction, or 3 to 5 times if perpendicular to the prevailing wind direction. These are minimums that allow as many rotors as possible to be located on a piece of land. There may still be significant disruption of wind with these minimum distances, as has been noted recently in several papers on array layout and performance.
Another thing to consider is that wind farms are typically on ridges or locations were there is a predominant prevailing wind direction. It’s not the same with small turbines, which tend to be sited in locales where the wind comes from all directions over the course of the year, even with a prevailing wind direction. Because of this, a minimum spacing of 10 times the rotor diameter is a prudent distance to separate small turbines.
Mick Sagrillo • Sagrillo Power & Light