Solar heat gain coefficient measurement of semi-transparent photovoltaic modules with indoor calorimetric hot box and solar simulator

Abstract

In tropical Singapore, buildings receive a high amount of solar radiation. Windows should therefore consist of solar control glazing with a low solar heat gain coefficient (SHGC) and high visible light transmittance to reduce the energy consumption for air-conditioning and electrical lighting respectively. Due to the rising demand for on-site electricity generation, photovoltaic modules are increasingly used in buildings, initially as roof-top systems, but in recent years there are also semi-transparent photovoltaic (STPV) being integrated into the façade or overhead glazing. However, their SHGC is usually not reported, potentially preventing STPV from widespread adoption. The paper presents measurements and novel presentations of SHGC for selected thin-film STPV glazing. It introduces SERIS’ indoor calorimetric hot box and solar simulator including a documentation of environmental conditions and calibrations. A sensitivity analysis concluded that the SHGC measurement is mainly sensitive to the spectrum of the solar simulator and reflection properties of the absorber plate. A correction factor was introduced and the measured results compare well with simulations. In addition, SHGC values for selected STPV are presented as (a) angular dependent and (b) load dependent. The results show that the SHGC is sensitive to the incident angle of solar radiation. Particularly for incident angles above 45°, which would be typical for facades in the tropics, the SHGC reduces significantly, compared to the default at 0°. The SHGC reduces only marginally when an electrical load is connected. Higher PV efficiencies would result in more energy being converted into electricity and not into re-radiating heat and therefore producing a lower SHGC.