Photovoltaic module shading: Smart Grid impacts

In the design of a solar photovoltaic system, one criterion that continues to receive low priority is the provision of minimum inter row spacing for photovoltaic modules. Consumers and installers alike strive to maximize area usage for systems such that they achieve the highest amount of annual energy output. This, in turn, leads to module rows being designed very close to each other; with array tilt lowered in an attempt to reduce inter row shading. This design practice fails to take into consideration many effects that close row spacing can have on system output. When designing a photovoltaic array to optimize its performance as a power generator and its contribution to the electric grid during peak demand periods - shading concerns become a key consideration. This paper describes a process developed at Rowan University´s Center for Sustainable Design to test the impact that inter row shading can have on power output and performance across the day. A test rig and protocol were created which tested module´s output given various depths of shading from one row of modules upon another. The exclusion of bypass diodes in the system was also tested to view the most extreme possible cases of power loss induced by shading. The results of this experimentation showed that even very small amounts of shading upon solar photovoltaic modules can lead to significant loss in power generation. As more PV systems are installed on the utility system their availability during peak times becomes an ever increasing requirement for Smart Grid success. This paper also explores the ramifications that proper inter row spacing design guidelines could have on reinforcing some of the fundamental principles of Smart Grid.