Theoretical and experimental analysis of a novel low emissivity water pond in summer

The present study focuses on the research of a new passive roof cooling technique, based on the combination of low emissivity materials and water. A novel roof pond is chosen as the most advantageous in terms of both energy efficiency and less maintenance or functional demands. The pond – referred as “Roof Pond with Gunny Bag” (RPWGB) – is covered by a cloth floating on water level, encouraging evaporative heat losses. A mathematical model describing the energy flux through the RPWGB is developed. The following sensitivity analysis marks the parameters that reduce bottom pond temperature thus improving the efficiency of the system. The experimental study analyses alternative ways to reduce bottom pond temperature. For this purpose, the low emissivity material is placed in different positions, above, below and floating on water level. Heat dissipation occurs by means of radiation losses and water evaporation.

► The emissivity of the cloth floating on water surface strongly affects the bottom pond temperature. ► Low emissivity materials that encourage evaporation can reduce pond temperature. ► An innovated passive roof cooling technique is tested and proposed. ► A low emissivity layer below or above water surface results a high temperature reduction.