Daytime radiative cooling

Abstract

Daytime radiative cooling (DRC) is a very novel passive cooling method for buildings that utilises the recent technological advance in wavelength selective-emittance material research and takes advantage of a transparency window that exists in the atmosphere between 8 and 13 μm. Application of DRC in locations where warm weather prevails for most of the year and cooling requirements of dwellings outweigh the respective heating ones could result in saving significant amounts of energy. Such a location is the small Mediterranean island of Cyprus. Designing an ideal radiative cooler is a challenging task and so it is to design an appropriate system that exploits the benefits of DRC. In such a design, a stratified thermal storage water tank can have a detrimental role. To identify whether it is possible to apply such a system in Cyprus, this project exploits the use of Matlab Simulink which has been used to run more than 6000 simulations, for a sensitivity and a varied analysis, taking into consideration different parameters with particular emphasis on the physical properties of the radiative cooling apparatus According to the data obtained, for the efficiency of a daytime radiative system to be maximized, the longwave transmission and emissivity coefficients of the cooler should be maximal while the shortwave transmission coefficient and the effective heat transfer coefficient to the environment should be minimal. Additionally, larger volumes of storage tanks achieve better results.