Development of synthetic hemispheric projections suitable for assessing the sky view factor on horizontal planes.pdfVIP

Energy and Buildings 82 (2014) 696–702 Contents lists available at ScienceDirect Energy and Buildings journal homepage: /locate/enbuild Development of synthetic hemispheric projections suitable for assessing the sky view factor on horizontal planes F.J. Casares, J. Ramírez-Faz ?, R. López-Luque Research Group of Physics for Renewable Energies and Resources. University of Córdoba. Edi?cio Albert Einstein. Campus de Rabanales, 14071 Córdoba, Spain article info Article history: Received 28 March 2014 Received in revised form 28 May 2014 Accepted 14 June 2014 Available online 29 July 2014 Keywords: Sky view factor Hemispherical projection Daylight abstract The solar radiation balance in buildings has a signi?cant impact on their energy needs, as well as on their potential for buildings-integrated photovoltaics (BIPV) energy production. It also in?uences the potentials of daylight, its healthiness and sustainability. Solar radiation models for urban environments require the characterization of the obstruction degree to which each point is subjected due to other buildings, topography, vegetation, etc. This characterization is carried out with the parameter known as sky view factor (SVF). In this paper, we check that signi?cant disagreements exist in the literature with respect to the de?nition of SVF. Most published methods show that SVF admits a geometric interpretation as a ratio of projected sky surface versus the global surface of the sky vault projected on the same system. Nevertheless, the type of projection depends only on the authors’ considerations. The geometric comparison of the methods opens a new way to explain their differences. This paper presents a general mathematical method to obtain projection equations, which allows the interpretation of SVF as a surface ratio. It is also proposed the adequate projection for horizontal surfaces under the hypothesis of angular distribution of diffuse radiance based on Moon–Spencer’s model. ? 2014 Elsevier B.V. All right