Agenda - Planning Commission - 08/06/2009

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Abundant Renewable Energy ARE 110 2.5kW and ARE 442 10kW turbines Proven Energy 2.5kW turbine rooftop array 8. Multiple Turbines: Though rare, some small wind systems come in "arrays" of multiple turbines, each of which is usually very small. However, regulations should treat additional turbines no differently than the first. So long as each turbine, or the resulting aggregate instal1ation, meets the sound, setback, and safety requirements as exist for other structures, there should be no need for further or special considerations. When determining height limits (if any - see "Setback Distances and Height," p. 8), keep in mind that rarely are multiple units equal economic substitutes for one larger, taller turbine. Therefore to meet restrictive height Iimitationsr multiple small turbines are not an equal substitution. See the payback period table in the "Height" (p. 7) section of this guide for an ill ustration. 9. Rooftop Turbines and Urban Environments: In very rare instances turbines are installed directly onto building rooftops or even designed as part of the building itself (known as "architecturally integrated"). These installations appear mostly in urban or densely-built areas where small property sizes may prevent the use of towers elsewhere on a property. These types of installations currently account for less than 1 % of all applications, but interest is increasing rapidly and zoning officials may receive permit applications for urban or rooftop installations. Siting becomes especiaJ.ly important for turbines in urban settings. Wind patterns behave very differently around buildings and in densely-built areas, so a turbine must be sited very precisely in order to gain access to wind of sufficient quality. Height, for example, becomes increasingly important in order for the turbine to rise above aerodynamic obstaclesand turbulencer as depicted in' the graphic below. Regardless of these unusu131 physical conditions, as long as other sound and setback requirements are met, no additional or unusual standards should be imposed for architecturally- integrated turbines and/or those in dense environments. AeroVironment rooftop array Source: Watson, SJ. "Predicting the Yield of Micro-Turbines in the Urban Roof-Top Environment." Centre for Renewable Energy Systems Technology, Loughborough University, U.K. Presentation, March 2008.