"They are Skystream 3.7 models built by Southwest Windpower in Flagstaff, Ariz. The blades are 12 feet in diameter, and they are 'downstream' type turbines, in that they turn their backs on the prevailing wind. 'Upstream turbines have tails that turn them to face into the wind.
"The turbines start producing power at wind speeds of eight mph. They are fairly unusual in that they have a transformer built into the turbine that converts the DC power turbines produce into AC power that can be used. Most turbines require a separate transformer.
"The top of the blades are 97 feet above the ground. At the school's location, anything under 100 feet does not need FAA review and approval. These are 'grid-connected' turbines and do not have batteries.
"The power they produce feeds back into the stadium's electrical system and helps provide whatever power the stadium is using at that time. If the stadium is not using power, the electricity produced by the turbines feeds backwards through the school's electric meter into the AEP grid for use by other customers.
"Roanoke City Public Schools' electric bill is credited for the amount of power returned to the American Electric Power grid. The turbines won't produce enough power to run the stadium during a night football game (unless it's really windy), but during the winter months when the stadium is not in use and the wind is pretty strong, the stadium should be a net exporter of power. That is, it will produce more power than it consumes keeping the toilet plumbing from freezing.
"I can't really project payback too accurately, as it is dependent on how much wind we get and how much rates continue to rise. Ideally, we should have done a year long wind study placing a wind speed monitor 100 feet in the air and taking recordings, but this would have cost more than the turbines, which run about $6,000 each, material only."