Adjustable PV Slats for Energy Efficiency and Comfort Improvement of a Radiantly Cooled Office Room in Tropical Climate

This paper investigated an application of adjustable photovoltaic (PV) slats to improve the thermal performance of an exposed glazing window and sequentially enhance the energy efficiency and thermal comfort of an office room. Solar radiation and longwave heat gains from a window fitted with PV slats were measured through experiments conducted in an outdoor chamber cooled by a radiant ceiling system. The daylight level at the workplane was also measured inside the chamber. A transient thermal model was developed and validated against experimental data. Using the experimental chamber as a demonstration case, the model revealed that adjusting the slats monthly to fully block direct sunlight could reduce the electrical energy use by 67% compared to a typical office with heat reflective glass windows. However, the electricity generated by the PV slats contributed a minor portion of the overall energy savings. To assess the thermal comfort impact of the PV slats in the room with the radiant cooling, this study utilized radiation asymmetry criteria from ASHRAE Standard 55. Simulations showed that the PV slat-shaded glazing window resulted in a lower asymmetric plane radiant temperature than the unshaded window of heat reflective glass. The adjustable slat system reduced the risk of local discomfort for occupants working near the window in the radiantly cooled office room.