Heating performance of an experimental passive solar house in Tunisia

Abstract

In Tunisia, heating requirements in winter are not very high; solar radiation is abundant and offers a high potential of energy for heating. Passive conversion seems suitable due to the low associated extra costs. Moreover, the high thermal capacity required for solar buildings is usually present in single family houses. The National School for Engineers of Tunis has built a solar passive pavilion which has been carefully instrumented. We present, in this paper, an analysis of the recorded measurements. One important question to investigate is whether, in our climate, passive solar energy can totally fulfil the heating requirements. Another interesting aspect is the simultaneous presence of Trombe wall and object gain elements, which are complementary in many respects. It is found that direct gain element shows a higher efficiency, but Trombe wall supplies energy gains, which are very appreciable at evening. Thermal circulation in its air gap has shown to be useless in our climate. The combined effect of the two elements results in autonomy in heating requirements. Experimental testing has been completed by computer simulations, which have indicated that thermal insulation is decisive for the average room temperature, but thermal capacity results in high temperature stability. Simulations have also shown that the constructed Trombe wall is too thick, and that double glazing is more efficient than night insulation to protect this element; whereas for the direct gain element, double glazing is hardly justified in our climate. Experimental and simulation results demonstrate that in Tunisian conditions, proper design of passive components can guarantee heating autonomy at low cost.