The pitfalls of building-integrated wind power

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What are the pitfalls and problems with building integrated wind power? Why is it that throwing a turbine on the top of a 50 M building doesn’t produce the output that the manufacturers state? Well, according to a recent article from Windpower Engineering Analyzing Building-Integrated Wind Power the problem is siting analysis, or the lack thereof.

Part of the problem is that urban and suburban areas include considerable turbulence and turbines mounted there have simply not been capturing enough laminar wind. Predicting wind energy quality and density is more complicated in built up areas, such as cities, than in rural plains where there are few obstacles upwind of the turbine.

As with any sort of wind turbine installation, siting for building integrated wind is absolutely essential to attaining the output expected by the turbine owner. If this is the case, and everybody knows it, then why isn’t wind turbine siting more prevalent in the small wind power arena? As with most things, it comes down to cost. Anemometer systems from companies like NRG Systems, or AWS Truewind are really quite expensive. It’s not uncommon for these testing systems to cost several thousands of dollars. Not only that, but along with the extra thousands of dollars one would invest in a datalogging system, there is also a considerable time commitment to throw into the mix.

The minimum time required for proper siting for wind turbines is three months. During this period of time the data loggers will capture and store information about a wind resource. How strong is your average wind, how rough (or turbulent) is the wind in that area, at what height can you achieve a maximum ROI? These are all answers your turbine site analysis can provide, but it takes time. However, the time and money that is required for proper wind turbine siting is more than worth it.

Recall in a previous post How High Should a Wind Turbine be, as the wind resource increases by a given increment, your power output increases by three times a given increment. So, if you have 12 mph winds in one area, but 15 mph winds in another, your power output will be drastically higher in the 15 mph winds.

Additionally, if you choose not to perform a site evaluation there are a number of items you will want to pay attention to before placing a turbine on your rooftop. Perhaps most important is the need to consider local effects, factoring for the size, shape, height, and distance of various obstructions. This incorporates the wind energy impacts of nearby trees, buildings, and other structures to understand how much the wind is blocked, what turbulence is created, and in some cases, how much the wind speed is increased. Further, if mounting on a building, it is critical to account for effects from the building, details such as its surface, roof edge, and roof features such as towers or chillers. For example, when wind hits any obstruction, it creates a separation zone arching out from the top of its vertical face. Above this point, the air remains smooth, but below, it becomes quite turbulent. This behavior must be considered in every rooftop-wind project to figure out how much higher the turbine must be mounted to capture energy from the smooth airflow.