Parametric analysis and optimization of an underfloor solar assisted heating system with phase change materials

In the present work, an underfloor solar assisted heating system with and without phase change materials (PCMs) in the floor is simulated and evaluated during the winter for a building of 100m(2) area in Athens (Greece). The analysis is conducted with TRNSYS software and the results are presented in energy and financial terms. Flat plate collectors coupled to a storage tank are used while there is an auxiliary energy system for supplying the extra heating demand when there is not adequate solar potential. The PCM-layer is used on the floor in order to increase the storage capacity and to avoid the operation of the auxiliary heating during the peak electricity demand period. Furthermore, this work presents the auxiliary loads, the indoor temperature and the total cost by changing the situation of the PCM, the volume of the storage tank, the area of the collectors and the thickness of the insulation. The results prove that the PCM-layer under the underfloor tubes reduces the auxiliary load by about 65%. Moreover, a multi-objective procedure proves that the PCM-layer under the underfloor tubes seems to be the most appropriate case due to the low heating consumption and the low total cost. Furthermore, it is found that during the cold winter days, the use of PCM is able to increase the indoor air temperature level about 0.8 degrees C. In the global optimum case, the collecting area is selected at 20m(2) and the storage tank volume at 1m(3).