Anyone who has installed solar panels on a roof and had to take into account and engineer for the potential of a panel to act as a wing knows rooftops are windy places. A 2005 analysis, “The Feasibility of Building Mounted/Integrated Wind Turbines”, funded in part by the Carbon Trust of the UK, confirms a 180% velocity increase as wind tumbles over a rooftop or hillside. Even a modest 8mph breeze becomes a brisk 14mph wind on top of a roof, so it is no wonder more companies are developing rooftop turbines.
Commercial and industrial locations, big box stores, shopping centers, schools, hospitals all consume huge amounts of power and possess acres and acres of wind-swept rooftop. As with solar, generating energy at the point of power consumption is the most efficient. No remote, long range, expensive, lossy utility distribution system is required nor the corresponding environmental footprint.
Commercial and residential buildings and structures have long been the largest consumers of energy resources in the world. The City of Chicago estimates 70% of emissions are the result of the energy consumed in buildings. As population and concomitant energy usage increases, the relative carbon impact of the total production and delivery of energy becomes a more significant problem.
Historically the early industrial and residential power production and distribution models were not large scale, and did not require or envision state wide or regional private monopolies delivering essential energy services. Nor is it sustainable to do so. A March 2009, National Geographic article notes that 2.2kwh are lost for every single kilowatt/hour used.
Clean alternative energy technologies, such as wind power and solar, and in fact all energy production systems are capable of manufacture and delivery on small local scales. Commercial, industrial and residential building structures provide ideal site locations for correctly designed ducted fan type wind turbines, and/or for photovoltaic arrays. Unlike solar, wind has the potential, depending upon local wind resource, to produce power 24 hours a day.
The American Wind Energy Association 2010 report on the small wind market projects an installed capacity of 1GW by 2015. According to the report, “…At least 17 companies worldwide manufacture or plan to manufacture building-mounted models…”
Retailers are starting to recognize the benefits of on site wind power. JC Penney is considering rooftop wind turbines and Sam’s Club boasts seventeen light pole mounted wind turbines at its facility in Palmdale, California, enough to cover 5% of its energy use.
The Carbon Trust indicated that rooftop wind turbines are not only viable but concentrated installations in areas with just 4 or 5 m/s wind speeds can significantly reduce carbon emissions by 2020. Measuring potential in the UK the report claims “…these installations could be achieving an annual energy production in the range of 1.5 -5 TWh”, and up to 2.2 metric tons of annual carbon reductions.
Aerodynamically, buildings function as concentrating collectors for wind. Wind cannot flow through the building but must move over and around it in higher velocity turbulent flows. As the AWEA study points out there are challenges to building mounted turbines, “…due mainly to the turbulent and unpredictable nature of winds around buildings”.
If an aerodynamically correct ducted fan wind turbine is located in these velocity-accelerated flows electric power production is higher than for remote open fans associated with an electric grid. The TOTAL system efficiency, from both an integrated construction and instant point power delivery perspective is the highest possible.
