The impact of shadow covering on the rooftop solar photovoltaic system for evaluating self-sufficiency rate in the concept of nearly zero energy building

Abstract

In cities seeking energy self-sufficiency, one of the trends is to pursue nearly zero-energy buildings (nZEB). To achieve this target, reducing energy consumption as well as replacing the traditional energy by renewable energy are two major strategies. The former is limited by the difficulty in lowering energy consumption in daily life, so the latter has more potential. Solar photovoltaic systems are a popular means to reach the goal of self-sufficiency in cities, and those on rooftops have the highest efficiency. Shadow from surrounding buildings affects the energy generation but this research found that the impact of shadow is generally limited. Only buildings of less than 3 storeys might suffer serious shadow covering and those higher than this mainly reduce their productivity by only about 1%. However, although lower buildings experience shadow effects, they are the main energy generators due to their low energy self-consumption. For example, the energy shortage of the tallest building in this case study could be covered by a 1-storey building with 10.33 times area. This research indicated that a fully energy self-sufficient environment can be achieved when the city pattern is designed with consideration of a well-balanced building height arrangement.