Experimental evaluation of radiant heat transmitted by light shelves

Light shelves are designed to distribute daylight deeper into the room and reduce energy con-sumption. While many studies have investigated the daylighting performance of light shelves, there are not much work done on the heat reflected by them. This paper aims to experimentally evaluate the radiant heat reflected from light shelves and analyse the trade-off between the trans-mission of heat and light. The study involves an experimental setup with controlled conditions and a novel methodology to quantify the reflected radiation. About 5 million data points for heat flux data were collected from light shelves made of eight different materials. Results showed that the mirror glass surface with high specular reflectivity, has maximum direct heat transmission of 10.4 W/m2 along with maximum illuminance. However, aluminium with lesser illuminance than mirror glass exhibits a maximum overall heat transmission of 35.8 W/m2. Also, polished black granite slab showed negligible reflected heat and moderate illuminance. Thus, this study helps us select materials for light shelves to reduce heat transmission without significantly affecting re-flected light.