3D Rooftop Photovoltaic Potential Calculation Using GIS Techniques: A Case Study of F-11 Sector Islamabad

Abstract

Pakistan is swiftly growing household electricity consumption country. There is approximately 9% increase in domestic consumption while the country is presently facing energy shortfalls. There is a need of considering energy mix due to increase in fossil energy prices, increased energy demand and unstable supply of electricity. Pakistan has great potential for solar renewable energy. Daily average value of received insolation is 5.4 kWh/m²/day. Rooftop photovoltaic technology is environment friendly and can be implemented by utilizing building rooftops without reserving any open space. F-11 sector of Islamabad, capital territory of Pakistan, was selected as study area for rooftop photovoltaic energy calculations. A GIS overlay analysis based methodology was developed for selecting suitable rooftops for photovoltaic system installation using high resolution Digital Surface Model (DSM), topographic factors and climate factors as input. Calculation of received solar radiation for complex urban environments is crucial as received amount of radiation varies with shadow by adjacent builds and trees so 3D shadow analysis of study area was done using tree growth model in Ecotect Analyst. Results showed, average received insolation is 1.65 MWh/m 2 /year with 4,359 annual peak solar hours and correlation coefficient is 0.94 between Marksim model base insolation and derived insolation from solar analyst tool. There is 0.4 km 2 rooftops are suitable for photovoltaic system out of 0.6 km 2 built-up area of sector and 90% of built-up area received 20-30 kW/m 2 /month insolation in June. Shadow analysis showed that amount of received solar radiation will reduce 5% in next 10 years and 10% in next 20 years.

Trends and Evolution of the GIS-Based Photovoltaic Potential Calculation

“…Just as in city models, DSMs can be produced from imagery through collimation. This is the case in [40], whose DSM was realized by LMKR (a Pakistan company) from stereo paired satellite imagery, and [42], whose pictures were acquired with a UAV. Both Teofilo et al [81] and Achbab et al [12] mention their use of stereo imagery for the realization of the products for the calculations, but they do not describe whether the dataset was acquired using a plane or from a satellite.…”

“…A total of seven parametersshown in Figure 9-was considered, with most studies defining the suitability based on at least two parameters. In one case only [40], the elevation is taken into account, setting a threshold at 3 m. Despite not being justified in the paper, it can be assumed that this is meant to remove the areas below the first floors, thus the most shadowed ones.…”

“…Shadowing is another parameter for the pre-filtering. In Hafeez et al [40], only the shadows deriving from the vegetation are considered. They are calculated through Ecotect software, inputting a 3D model realized with Google Sketchup according to an unsupervised classification of aerial pictures, for 10:30 AM and 3:30 PM of the solstices.…”

Incidence of Photovoltaics in Cities Based on Indicators of Occupancy and Urban Sustainability

“…Three-dimensional (3D) analyses have evolved to a state where they can be used to evaluate urban solar potential. Using 3D analysis methods, the effects of shadows and the surface layout of facades and roofs can be included [15,16], along with the urban density and surface orientation [17]. However, extensive human and computational resources are required to process geometrical information [16].…”

The Role of Renewable Energy in the Promotion of Circular Urban Metabolism

“…Analysis using 3D for assessing solar potential in cities is becoming common since it allows the consideration of the effects of shade (trees, buildings), facade and roof surfaces [95,96], and urban density and orientation [54]. However, computational efforts and prior rendering of the urban environment to be evaluated is required [96].…”