Is this the largest rooftop wind installation in the world?

A newly opened wind farm on the roof of the Oklahoma Medical Research Foundation is claimed by turbine suppliers Venger to be the largest building-integrated wind farm in the US. But might it be the largest in the world?

On June 22, 2012, wind turbine manufacturer put out a nondescript press release with the headline "Venger Wind Farm Installed on Roof of Oklahoma Medical Research Foundation (OMRF)." Welcome, but at first glance, not particularly ground-breaking news. Rooftop wind installations of significant capacity are relatively rare, but not so rare that a new one is likely to grab many headlines beyond local news coverage.

But a second look reveals, four sentences into a lengthy opening first paragraph, the following nugget of information: "the project is the largest building integrated wind energy system in the US." Yes, this appeared in the first paragraph, but with the sheer volume of press releases put out on a daily basis, this may as well have been written in Hittite. Talk about burying the lede. Credit must go to Inhabitat's Timon Singh for spotting this significant detail (assuming that's where he saw the story).

But enough about the subtleties of press release writing. Just how large is "large?" One hopes and assumes that by size, Venger is referring to installed capacity: the power the farm is capable of producing at peak output. The roof of the OMRF is now graced with 18 of Venger's 18.5-ft (5.6-m) V2 vertical-axis wind turbines. Each has a capacity of 4.5 kW, giving the installation a theoretical capacity of 81 kW overall. As rooftop installations go, that's certainly nothing to be sniffed at. As a basis for comparison, the three turbines integrated into London's Strata residential block have a combined capacity of 57 kW.

The wind farm is built on the roof of the 130 ft-tall Oklahoma Medical Research Foundation

The cut-in speed of the turbines is 8.9 mph (or 4 m/s). That's the wind speed required for the turbines to even begin generating power, and is quite high compared to other wind turbines designed for urban conditions. The McCamley turbine we looked at recently begins to be productive in winds as weak as 4 mph (1.8 m/s). In Venger's favor is that they are sited on the 130-foot (40-m) tall OMRF, where wind speeds are certain to be higher.

An OMRF press release says that the turbines are projected to produce 85,500 kWh of energy per year, equivalent to seven average-sized American homes (and the amount of energy generated were the turbines to run under ideal conditions for 1000 hours.) Refreshingly, the release also points out this will not be enough energy to meet the OMRF's needs, but doesn't let us know what proportion of its demand that would cover. Strata's turbines (to use them as a yardstick again) were only expected to meet 8 percent of the building's energy needs, and you can bet that the OMRF houses more power-hungry gear than a mere tower block.

Interestingly, Venger isn't merely claiming this as the largest rooftop installation in the US, but the largest building-integrated installation. As most building-integrated installations will be on the roof, this isn't a huge distinction, but it's a slightly larger subset of wind turbines all the same. Turbines can also be mounted on building facades.

Inhabitat in its coverage calls this the largest rooftop installation in the world. We're happy to go along with that, unless anyone out there can point us to anything bigger still.

Sources: Venger and OMRF, via Inhabitat