Analyzing the angles of building orientation for solar energy use (Case study: Tehran city)

Introduction and Background: One of the approaches to reduce fossil fuel consumption and their pollution in cities, is to pay attention to the climatic conditions and ecosystems of the region and to use renewable energy in architecture and the design of buildings; This subject in the case for Tehran metropolis is more important, due to the high concentration of population and the activity and, consequently, the great amount of constructions. Aims: The aim of this research is to determine the optimal building orientations through surveying the amount of direct radiation energy, received by vertical surfaces of buildings in Tehran city. Methodology: In order to achieve this goal, taking into account the azimuth and the height of the sun at different times of the year, the “Law of cosines” computational method and Q-BASIC software were applied to compute and analyze the amount of received direct energy on vertical surfaces of buildings in all months of the year and in 24 geographic directions. The most suitable direction for building orientation is determined through the maximum difference between the amount of energy in cold and hot periods or the highest percentage of radiation received in the cold period. Conclusion: Based on the results of the research, the maximum annual amount of received solar energy in the city of Tehran belongs to the 150 degree South-East and West, and the lowest annual amount of energy is related to the walls facing the North; In order to get optimal solar energy, the directions of 150 degrees South-East to 210 degrees South-West are among the acceptable orientations (first to third priority). The best orientation for one-way buildings in Tehran is 180 degrees South; Also the best orientation for two-way buildings is the North-South direction and for four-sided buildings are (0, 180, 90 and -90) degrees.