Energy saving potential in buildings for Karachi climate using daylight

Pakistan consumes 50% of its total primary energy and 46.5% of electricity in residential sector. Furthermore, the primary energy and electric energy rates of consumption in residential sector are increasing by 4.5% and 1.3% respectively, because of the increase of population and rise of the standard of living. As Pakistan is short of energy resources, it imports expensive oil that underlines the need for energy conservation. Buildings have the largest potential for energy saving especially for lighting by using more efficient Light emitting diodes (LEDs), Compact fluorescent light (CFLs) and by using daylight as 38% of the residential electricity is consumed for lighting only. This study investigates the potential of reducing energy consumption by using daylight through domes in roofs. Roof domes affect the energy required for lighting, heating and cooling. As EnergyPlus software has the capability to analyze daylight and energy flow in buildings, it is used for this study. Typical Meteorological Year (TMY) hourly data for Karachi is used as input to the EnergyPlus program for the calculation. Simulations show that the optimal dome area is 0.155% of the floor area to have the minimum total energy consumption in Karachi. By using the optimal dome area, reasonable illuminance distribution are obtained in the building even during the month of December. Calculation result also show that the optimal area of the dome saves Rs3651/- per year in electricity bills for the house hold. The use of roof dome of optimal size therefore saves electricity bills of the building owner as well as helps to overcome energy crisis in the country. Also a planned location of the dome in the roof will achieve a desired lux level at any location inside the building.