The sun is the prime source of energy

 Solar Passive   

The sun is the prime source of energy. Passive solar design refers to design that uses solar energy to attain thermal and visual comfort. It encompasses a wide range of strategies and options used in buildings to reduce energy consumption and increase occupant comfort. Passive solar design emphasizes architectural design approaches that minimize the demand for energy by measures such as appropriate building siting, efficient envelopes, appropriate fenestration, daylighting design, and thermal mass. The basic intent of a passive design is to allow daylight, heat and airflow into a building whenever beneficial, store and distribute the heat and cool by natural means.