Abstract:
Pakistan is rapidly 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 because of increase in fossil energy prices, increased energy demand and unstable supply of electricity. Pakistan has great potential for renewable energy. Daily average of received insolation value is 5.3 kWh and solar Photovoltaic technology is used widely for solar renewable energy. Rooftop photovoltaic technology is environmental friendly and can be used 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 using high resolution Digital Surface Model (DSM) prepared from stereo pair satellite imagery, topographic, economic and climatic factors as input for selecting suitable rooftop for photovoltaic system installation. Study area on average receives insolation of 1.65 MWh/m2/year with 4,359 peak solar hours. Correlation coefficient is 0.94 between ground based and derived insolation from solar analyst tool. Our findings suggest that 0.40 km2 rooftop area is suitable for photovoltaic system out of 0.66 km2 built-up area of sector. Most of the buildings are 35-50ft in height and 90% of built-up area received 20- 30 kW/m2/month insoiation in June. Calculation of received solar radiation for complex urban environments is crucial as received amount of radiation varies with shadow by adjacent buildings and trees. So 3D shadow analysis of study area was done using tree growth model in Ecotect Analyst which showed that amount of received solar radiation will reduce 5% in next 10 years and 10% in next 20 years thus will affect the efficiency of installed system. This study used 3D modem technology and can be useful for decision maker, users, and stakeholders of solar energy technologies. The methodology developed is flexible thus can be utilized in same or modified form for building rooftop or facade photovoltaic projects.
