A Commercial Building Lighting Demand-Side Management through Passive Solar Design

Abstract

The commercial sector that comprises of schools, libraries, public and private offices is the third largest energy-consuming sector in South Africa. Lighting is a significant contributor to the overall energy consumption in this sector. The aim of this study is to analyse the indoor daylight illuminance of a passive solar office building and the potential demand-side management. A passive solar building in SolarWatt Park, Alice South Africa was used as a case study. The indoor illuminance that includes electric and day lightings were monitored by two sets of Li-210R photometric sensors. Four cool white fluorescent fittings with each containing two 58W lamps served as the electric lights of the office inner space. The average illuminance of the office space with all electric lights on and without daylight was found to be 460 lux. The indoor average daylighting illuminance was 910 and 170 lux on a typical clear sky and overcast days, respectively. A daily cumulative energy savings of 11.14 kWh on a clear sky day and 0.47 kWh on an overcast day was achieved, assuming the office inner space illuminance was maintained at 300 lux. The monetary savings due to the energy saved was estimated at 1285.36 USD per annum. Based on the findings of the study, daylighting through passive solar design reduces energy consumption without compromising the visual comfort of the occupants. Integration of passive solar design for daylighting with indoor daylight switch controller is recommended for optimum energy savings.