OPTIMISATION OF THERMAL LOAD OF PHC UNIT, KARACHI-PAKISTAN, BY OPTIMIZATION USING ORIENTATION, ENERGY SIMULATION IN AUTODESK ECOTECT & PVSYST SOFTWARE

Abstract

In hot areas, buildings consume significant amounts of electricity on cooling, which puts additional strain on the power system in Pakistan. This study investigates if the building orientation alone has a cooling load reducing effect. A primary health care unit of the area of 500 m² was modelled in Autodesk Ecotect for Karachi (24.86° N, 66.99° E). The model was then rotated around from 0 degree to 360 degree in 10 degree increments and the cooling requirement was noted for each angle. Load increased from 38.20 tons of refrigeration (TR) for the building oriented North (0°/360°) to 38.62 TR at 230°. The alignment with the north thus reduced the heat gain by approximately 5,070 BTU/h or a saving of 561.9 kWh per month (PKR 33,713 at PKR 60 per kWh) compared to the baseline of 34,765.9 kWh. The optimised load is 38.2 TR (approx. 133 kW) and PVSyst was used to design a solar supply system of 532 modules of 400 W and an inverter of 150-200 kW and 98.2% efficiency, for the daytime operation. The orientation gain is relatively small (e.g., 1.1% of the peak cooling load), but it is free at design time and can be used in conjunction with other envelope measures like reflective roofs, insulation and thermal mass. The outcomes provide an easy, inexpensive design guideline for new health facilities and housing scheme in Karachi and other hot coastal cities.