Solar energy potential estimation by calculating sun illumination hours and sky view factor on building rooftops using digital elevation model

Abstract

The detailed and precise estimation of solar energy is a major requirement for solar applications on building roof tops. These estimations help in sustainable development, energy policy making, and renewable energy consumption. In this paper, a methodology was devised to estimate the solar radiation components. This methodology is easily accessible using a simple measuring tape to form a digital elevation model with a cell size of 1 × 1 sq. ft. Liu and Jordan's model [Liu and Jordan, “The interrelationship and characteristic distribution of direct, diffuse and total solar radiation,” Sol. Energy. 4(3), 1–19 (1960)] was modified for the urban environment and programmed in MATLAB to estimate solar potential. To validate the developed algorithm and modified model, the roof-top area of the postgraduate laboratories of the Mechanical Engineering Department (NED University) was selected as a case study. Measurements were carried out on different days, which showed good agreement with the proposed work. Within the study area, the maximum sunshine hours is 3285 annually, while the site selected has at least 1502 sunshine hours irrespective of elevations. Similarly, the sky view factor has a maximum value of 1 exposed to open plain and a minimum value of 0.4143. Radiation maps were generated for the installation of solar applications. The results showed that the average beam radiation was 4.908 kWh/m2, with May and December having the maximum and minimum beam intensities of 6.679 kWh/m2 and 3.815 kWh/m2, respectively. Similarly, the average diffuse radiation was 2.289 kWh/m2, with maximum and minimum values, occurring in July and October, of 3.611 kWh/m2 and 1.299 kWh/m2, respectively. This work will help energy consultants and households in determining the solar energy potential of the existing flat rooftops and for future construction, thereby cutting energy bills and producing long-term monetary incentives from generating their own energy.