ABSTRACT
The effective thermal mass of a room can be increased by incorporating phase-change material (PCM) in the floor, walls and /or ceiling. A higher thermal mass involves a better utilization of solar and internal heat gains and therefore reduces the energy required for heating. Similarly, the storage of coolth in PCM during summer may reduce the energy demand for cooling. In this paper the influence of the PCM properties and building characteristics on the energy use for heating and cooling in a Dutch climate is studied. The energy saving found with a numerical model is compared with 1) a lumped-parameter analytical model according to prEN 13790, and 2) the same, but linear, numerical model without PCM where the sensible heat capacity has been increased to simulate the effect of latent heat. Results show that the analytical model does not yield a reasonable estimate for the energy saving. Although the prediction of the linear dynamic model is also rather poor for heating, it is very satisfying for cooling. The effect of PCM is maximized when the phase-change takes place just above the thermostat temperature during heating, whereas during cooling the phase transition must occur just below the desired temperature.
