Non-convective roof pond with movable insulation for passive solar space heating in cold climates

Abstract

A roof pond may be rendered non-convective by increasing the viscosity of its water with suitable thickeners like natural gums or polymers. The thermal performance of such a non-convective roof pond system covered by movable insulation during the night is investigated for passive solar space heating in cold climates. The analysis is based on the solution of the heat conduction equation for temperature distribution in the roof pond system subjected to periodic solar radiation and atmospheric air on one side and in contact with room air at constant temperature (corresponding to air-conditioned rooms) on the other side. The day-to-night change of insulation has been represented by a rectangular step function variation of the heat transfer coefficient at the pond surface. An explicit solution for the temperature distribution satisfying appropriate boundary conditions has been derived to obtain the heat flux entering the room. It is found that the proposed system is quite suitable to provide the heating need in cold climates, and the thermal storage behaviour of this system is much better than a convective roof pond system with movable insulation.