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URBAN WIND ENERGY, WE JUST START
Sander MERTENS Ph.D M.Sc B.Eng
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Ingreenious B.V. , Voorburg, The Netherlands, [email protected]
Keywords: wind, energy, urban, turbines
Abstract For some years now, harvesting wind energy with small wind turbines in the built environment plays an increasing role in “renewable energy production” . Until now the success of these so-called “urban wind turbines” is not as expected. This is mainly due to lack of knowledge. An evaluation of test results from an open air test facility in Zeeland shows part of the problem. In this test the energy yield of 11 small wind turbines was measured together with the wind speed at the site. Only three wind turbines out of 11 achieved good efficiencies, while the total investments for installing the wind turbines varied a factor 7. Manufacturers complained about the wind speed that was measured to be 3.8 m/s, somewhat higher than the average wind speed at roofs in the built environment, which is about 2-4 m/s. But not only manufacturers of urban wind turbines lack knowledge of urban wind. Architects should also spend more hours on studying urban wind, as designs of building integrated wind turbines are often contra-intuitive. Such is clearly shown by the design of the Bahrain World Trade Center that should be rotated 180 degrees in order to profit from accelerated wind speeds. This all shows that “urban wind turbines” are hard to find yet and that manufacturers or architects have little knowledge of wind energy in the built environment. We should therefore spend more time on research, measure wind speeds in the built environment before installing a wind turbine and measure the performance of so-called urban wind turbines. We just start to understand “urban wind” and “urban wind turbines”.
1. Wind speed in the built environment The built environment wind is defined as wind influenced by buildings or significant obstacles like trees such that the roughness length z0 is at least 0.4. 1.1 Wind speed distribution An analysis of the wind speed statistics for three sites in the built environment reveals the following hourly averaged wind speeds u0 and shape factors k of the two parameter Weibull distribution.
Table 1 Measured wind speed statistics according to Mertens (2009), Staelens (2009) and Brown (2009) Location Schoondijke, The Netherlands The Hague, The Netherlands Kortrijk, Belgium 18 sites out of 24 sites in the UK Average
Hourly average wind speed u0 3.8 2.3 2.8 ?
Shape factor k 1.6 1.6 1.7
Sander MERTENS Ph.D M.Sc B.Eng
1
1
Ingreenious B.V. , Voorburg, The Netherlands, [email protected]
Keywords: wind, energy, urban, turbines
Abstract For some years now, harvesting wind energy with small wind turbines in the built environment plays an increasing role in “renewable energy production” . Until now the success of these so-called “urban wind turbines” is not as expected. This is mainly due to lack of knowledge. An evaluation of test results from an open air test facility in Zeeland shows part of the problem. In this test the energy yield of 11 small wind turbines was measured together with the wind speed at the site. Only three wind turbines out of 11 achieved good efficiencies, while the total investments for installing the wind turbines varied a factor 7. Manufacturers complained about the wind speed that was measured to be 3.8 m/s, somewhat higher than the average wind speed at roofs in the built environment, which is about 2-4 m/s. But not only manufacturers of urban wind turbines lack knowledge of urban wind. Architects should also spend more hours on studying urban wind, as designs of building integrated wind turbines are often contra-intuitive. Such is clearly shown by the design of the Bahrain World Trade Center that should be rotated 180 degrees in order to profit from accelerated wind speeds. This all shows that “urban wind turbines” are hard to find yet and that manufacturers or architects have little knowledge of wind energy in the built environment. We should therefore spend more time on research, measure wind speeds in the built environment before installing a wind turbine and measure the performance of so-called urban wind turbines. We just start to understand “urban wind” and “urban wind turbines”.
1. Wind speed in the built environment The built environment wind is defined as wind influenced by buildings or significant obstacles like trees such that the roughness length z0 is at least 0.4. 1.1 Wind speed distribution An analysis of the wind speed statistics for three sites in the built environment reveals the following hourly averaged wind speeds u0 and shape factors k of the two parameter Weibull distribution.
Table 1 Measured wind speed statistics according to Mertens (2009), Staelens (2009) and Brown (2009) Location Schoondijke, The Netherlands The Hague, The Netherlands Kortrijk, Belgium 18 sites out of 24 sites in the UK Average
Hourly average wind speed u0 3.8 2.3 2.8 ?
Shape factor k 1.6 1.6 1.7
