Thermal monitoring and indoor temperature predictions in a passive solar building in an arid environment

In this paper, results of a long-term temperature monitoring in a passive solar house, located at the Sede-Boqer Campus of the Ben-Gurion University, in the Negev region of Israel are presented. Local latitude is 30.8°N and the elevation is approximately 480 m above sea level. The climate of the region is characterized by strong daily and seasonal thermal fluctuations, dry air and clear skies with intense solar radiation. The monitored building consists of a two storey, passive solar house and belongs to a student dormitory complex located at the Sede-Boqer Campus. Formulae were developed, based on part of the whole monitoring period, representing the measured daily indoor maximum, average and minimum temperatures. The formulae were then validated against measurements taken independently in different time periods. In managing the building, the main objective in the winter was to bring up the indoor temperature by direct and indirect solar gains while in the summer it was to keep the temperature down. Therefore, analysis of the data and development of predictive formulas of the indoor temperatures were done separately for the winter and for the summer. Measured data of each season were then divided into two sub-periods, the first one used to generate formulas based on measured data (generation) and the second for testing the predictability of the formulas by independent data (validation). In general, a fairly good agreement was verified between onsite measurements and results of the formulae, with regard to daily indoor maximum, average and minimum temperatures. The issue of using outdoor temperatures measured in the adjacent street canyon instead of those registered at the local meteorological site for evaluating the buildingʹs cooling demand is also addressed in the paper. The developed formulae were here used for estimating the buildingʹs thermal and energy performance in summer, taking into account: (1) solely climatic data from the meteorological station; (2) climatic data from the meteorological station, except for outdoor ambient temperature, which was monitored adjacent to building. Results indicated that the calculation of the buildingʹs energy demand for air-conditioning based on temperature data collected at the meteorological station would yield half of the cooling degree-days externally and about two-thirds of that internally, as compared to adopting measured canyon temperatures for such calculations.