Optimal design of photovoltaic energy collectors with mutual shading for pre-existing building roofs

Technological advances in photovoltaic energy and reductions in the costs of photovoltaic (PV) cells make it likely that the roofs and faces of buildings will in the near future be clad with PV materials. These materials will act as insulation (passive efficiency), as a heat source (hot water) and as a source of electricity (active efficiency). This paper proposes a method for determining the most suitable orientation for the location of PV modules with a view to making optimal use of the solar irradiance available. The method can be extrapolated to all types of flat building shell, all orientations and slope angles, all geographical locations and all module sizes and performance efficiencies. It enables best-performing plant to be designed according to the needs of each user (maximum number of hours-equivalent or maximum output). The method is based on an algorithm that calculates the optimum tilt and azimuth angles of PV modules on the basis of estimated data for solar irradiance, PV module shading times and roof characteristics. The results are checked against the outputs of various PV installations currently up and running. This method is a highly useful tool for working towards building-integrated photovoltaic (BIPV) systems in urban settings.