Sizing and Modeling of Daytime Radiative Coolers coupled to a Heat Pump System

The demand for cooling in buildings is persistently escalating and is estimated to reach a relevant share of overall building energy consumption in the coming years. This increase, accompanied by a corresponding rise in greenhouse gas emissions, is leading to an active investigation of novel passive cooling technologies, such as Daytime Radiative Coolers (DRCs). Regrettably, a universally accepted sizing methodology for DRCs is presently lacking, with only a limited number of simulation models having been developed thus far. This thesis work endeavors to formulate a comprehensive sizing procedure for DRCs, tailored to real-world conditions, with the ultimate aim of ensuring their effective operation during the cooling season. DRCs, as radiating surfaces capable of dissipating heat to outer space even under direct solar exposure, offer valuable integration with conventional heat pump systems. The model developed in this work encompasses a three-room building interacting with fan-coils, responsible for delivering the cooling effect. These devices are connected via a closed-loop water circuit to an air-water heat pump, with radiative coolers supplying additional cooling to the refrigerant fluid exiting the heat pump condenser. The incorporation of DRCs downstream the condenser has the potential to lower the refrigerant temperature to sub-ambient levels, resulting in a reduction of heat pump compressor work and an improved thermodynamic cycle coefficient of performance (COP). As the optimal system design depends on the installation site and specific operating conditions, the sizing procedures outlined in this thesis may ultimately contribute to pave the way to the optimization of DRC systems and the development of more sustainable cooling technologies for the building sector.