Thermal-optical-electrical performance of combined photovoltaic-polymer dispersed liquid crystal for switchable BIPV-smart window

: To address the growing energy demands in buildings, particularly from HVAC (Heating, Ventilation, and Air Conditioning) systems, there is an urgent need for technologies that can help achieve the global 2050 building energy targets. Switchable photovoltaics is one such technology that can adjust transparency and simultaneously generate power. While newly investigated materials show potential, their industrial application is still far from realization. In contrast, several existing technologies are already capable of meeting these targets. To explore this, a polymer dispersed liquid crystal (PDLC) smart window with a crystalline structure-based photovoltaic (PV) was sandwiched between one glass sheet and one acrylic sheet and experimentally characterized to evaluate its thermal, optical, and electrical performance using an indoor test cell. The 30.6 cm × 21 cm switchable building integrated PV (BIPV)-PDLC glazing system consisted of six solar cells, three connected in series, with two strings connected in parallel. The system’s total active transmission was 46.5% in the PDLC ON state and 31.5% in the OFF state. Two configurations were developed: one where the PV faced the external ambient (referred to as "PV on the top") and another where the PDLC was positioned on top of the PV. Both PV and PDLC were sandwiched between the glass and one acrylic sheet to keep the system lightweight. The solar heat gain coefficient (SHGC) values for the combined system were 0.54 in the PDLC ON state and 0.43 in the OFF state. The overall heat transfer coefficient ( U -value) in the PDLC ON state was 5.2 W/m 2 ·K, while in the OFF state, the average U -value was 4.7 W/m 2 ·K. It is recommended that although the transmission, U -value, and SHGC are unaffected by the position of the PDLC and PV, for optimal PV performance, it is better to position the PV facing the external ambient. This allows for more incident light, which increases power production, while the cooler ambient conditions improve the PV’s efficiency.