Comparative study of the efficiency of earth/air heat-exchangers versus direct solar floors systems for residential buildings in Belgium

Net-zero-energy building concept is a solution for high-performance buildings that integrates passive design and energy efficiency measures with renewable energy systems. Given the specific technical characteristics of net-zero energy buildings, two technological solutions are investigated, in this experimental study: Earth/Air Heat-Exchangers and Direct Solar Floors. To carry out this study, an experimental cell composed of two rooms equipped with two energy systems was constructed. One room is coupled to a solar thermal collector with a surface area of 4.60 m2 and the second room is coupled to an air ground heat exchanger (with a 20m conduct length, 0.012 m diameter and 2 m burial depth). A data acquisition system was set up to measure the air temperature at the inlet-outlet of the air/ground heat exchanger, solar thermal collector and indoor air temperature. The obtained experimental results were compared with those resulting from the simulation under the TRNSYS building performance simulation environment. Good agreement between the simulated results and the experimental data was achieved through model calibration. After the validation of the models, a parametric study was conducted to identify the energy contribution of each system under Belgian climate conditions. A control strategy i proposed to improve the performance of each system. The results of this study help building designers to better dimension and control the operation of renewable systems to ensure higher building energy autonomy.