Experiment on heating system combined shallow geothermal energy with solar wall in winter

Abstract: Passive solar energy heating technology of the solar wall using air as heat-conducting medium for heating has been widely applied, with the advantages of simple structure, low cost and high heat collecting efficiency, and is suitable for non centralized heating of the rural residence in the severe cold area of Xinjiang, China. However, due to the instability and dispersion of solar energy, some problems of poor stability and comfortlessness gradually occurred in the application of the passive solar house. Therefore, we should consider the rational design of the basement and compensate for the instability of solar energy by using the relatively stable characteristics of the temperature of surrounding shallow soil. Combined with the solar heat collecting wall, the indoor temperature at night in winter or on rainy days would be enhanced, and the heating effect of the solar house in winter would be improved. A system of shallow geothermal energy combined with the solar collecting wall was proposed, and a solid model of 1:1 in Shihezi area was built in this paper. On the sunny day in winter, the glass cover-plate and the heat collecting plate of the solar wall system absorbed the solar radiation to heat internal air of the air bay layer. When it reached a certain temperature, the ventilation scoop of solar collecting wall made hot air into the interior, which would then make the indoor convection. Then the control valve of the basement vents was opened to store redundant heat there. At night, the wall was closed and the air vent was opened in the basement. The heat stored in the basement and accumulated in the shallow soil was transported to the upper space so as to heighten the indoor air temperature. Heating test was carried out in passive solar house in Shihezi with the system, and the indoor thermal environment was comparatively analyzed under different heating modes (C1, C2, C3) and different weather conditions (sunny, cloudy). Among them, C1 was the control room without any heating measure; C2 was the test room with closed roof vents of basement, only considering the heating effect of south heat collecting wall; C3 was the test room using the heating mode of combining the shallow geothermal energy with solar wall. The experiment results showed that the average temperature in the house with the C3 heating mode was higher than that in the contrast house, and daily range of temperature was 3.5 ℃; on sunny day, the test room had 5 hours in which the temperature was over 12 ℃; when it was cloudy, the temperature difference between the indoor and outdoor of the solar room remained 9.52 ℃; when the outdoor weather condition was sunny and the AQI (air quality index) was within the limits of the secondary standard, the requirements of the indoor temperature in the test room could be met only relying on the system combining shallow geothermal energy with solar wall in October, November, and March and April next year that were within the heating period, and the energy-saving effect was remarkable.