Comparing Building Surfaces’ Orientations to Optimize Solar Energy Collection

Net-zero and other high performance green buildings normally do or should include optimized solar energy systems. While detailed computer-based energy simulations of buildings’ energy systems are becoming near-commonplace for many projects, simple, easy-to-use data tables are beneficial earlier in the design process to help guide preliminary decisions in all projects. Practical lookup tables, and then comparison of the data they contain, are also very useful for teaching new concepts, in this case for learning about solar orientations in sunny locations.

Engineers, architects, design-build contractors, students, and other designers of green buildings can benefit through knowing, in advance, how exterior surfaces’ orientations increase or decrease the total annual solar energy arriving upon those surfaces. For example, maximizing the incoming energy on a particular roof is advantageous for gathering solar energy for heat or for conversion of that sunlight to electricity, but various requirements often limit designers’ choices for surfaces’ orientations. This paper presents simple tables that form a tool for making initial decisions on surfaces’ directions and slopes; the user can then study various effects further, such as local factors including cloudiness and shading, with detailed software. The classical solar geometry equations utilized are documented here for repeatability of the research, but are not necessary for use of this paper’s tables. Practical examples are given too to help readers use the tables.