Polymer dispersed liquid crystal retrofitted smart switchable glazing: Energy saving, diurnal illumination, and CO2 mitigation prospective

Abstract

Smart switchable glazing provides better thermal control and daylighting performance in building compared to conventional glazing. The polymer dispersed liquid crystals (PDLC) glazing can switch translucent to transparent when an active electric field is applied. Solar and visible light properties were measured experimentally for four different colored PDLC film glazing (pink, yellow, blue, and white) in transparent (on) and translucent states (off). The PDLC glazing unsteady-state thermal transmittance (U-value) and solar heat gain coefficient (g-value) were computed to analyze heat gain/loss through glazing. The measured solar optical properties were used to compute the solar heat gains and cost savings when existing glazing in a library building was replaced with different PDLC glazing systems. The PDLC glazing has shown substantial reductions in building cooling loads which correspond to cooling cost savings. Different colored PDLC glazing systems (on/off-states) were studied for cooling cost savings to replace tinted bronze glazing (TBG) in an existing building in a cooling-dominant climate. In on-state, white PDLC glazing (PDLCW-on) had concluded the highest mean air-conditioning cost savings (5.76 $/m2) and total air-conditioning cost savings of 8286.6 $ with the lowest payback time of 8.92 years (on-state) compared to other studied PDLC glazing in on-state mode. PDLC glazing systems have also shown substantial mitigations in CO2 emissions. The white PDLCs in on-state (PDLCW-on) had reported the highest CO2 savings of 101.5 tCO2/year among all PDLC glazing studied in on-state mode. Daylighting analysis was performed to know the daylight accession and distribution inside the building interiors with Design-Builder (V 6.1.8.021). The average daylight factor (DF) metric of PDLC glazing was well above the minimum recommended level for library interiors as per Indian codes. The color rendering properties of PDLC glazing systems were also investigated for interior visual acceptability.