Performance Study On Active Solar Heating System In Northwest China

With the process of low-carbon urbanization construction, the new rural residential buildings spring up, but these new rural constructions with poor indoor thermal comfort consume a large amount of commercial energy in heating season in cold regions especially in Northwest China, though a comfortable indoor environment is at the cost of massive energy. It is the poor envelops and backward heating methods that consume much energy to heat buildings. To meet the demands of improving thermal enviroment and decreasing energy consumption for heat simultaneously, the application of exterior wall insulation and active solar water heating system is proposed and the influences on thermal enviroment and energy consumption are studied through filed comperative experiment under the condition of abundant solar energy in local regions. The main study and conclusions are as follows:(1) Comperative experiment to research t he thermal enviroment difference between active solar water heating system with three op erations and coal-fired boiler with traditional method reveals that thermal environment in experimental building is better than that in reference building. Daily average temperature in experimental building is about 14.5℃, which is higher than that in reference building by 5.4℃ and the mean radiant temperature in experimental building is higher than that in reference building by 3.3 ℃ when the outdoor lowest temperature is-16.2 ℃. The indoor relative humidity is about 58%, which is suitable for residents and the average indoor air velocity is about 0.28m/s. The vertical temperature at daytime is stable and the maximum vertical temperature difference is 0.5℃ between the points at 1m and 2m.(2) The relation of indoor temperature, inlet water temperature of radiator and outdoor temperature is formulated by binary linear regression equation analysis under the condition of some postulates in this paper. Indoor temperature raises 0.15℃ with the increasement of water temperature in heater by 1℃, while indoor temperature decreases 0.04℃ with the drop of outdoor temperature by 1 ℃. More efficient use of available heat in storage tank is very important in the condition of good envelop insulation.(3) Higher water temperature in storage tank after heating than the initial temperature for collecting solar energy on the next day is essential to normal operation of solar water heating system because of limited solar intensity in winter and the solar collection area. While the temperature difference results in large night heat loss which is releated to the temperature difference between hot water in storage tank and outdoor temperature. Taking into account of transferring storage tank from outside to indoor is helpful to minimiz e night heat loss and prolong the heating period relatively, so the indoor temperature may rise further by reusing the night heat loss.(4) By exterior wall insulation only, the energy saving fraction of experiment residence is about 58.7% during heating period and the payback period of the additional cost of exterior wall insulation is about 2.5 years, not mentioning the social and environmental benefits.(5) The energy saving fraction of experiment residence was about 78.0% in heating period and the payback period of the additional cost of the solar water heating system and exterior wall insulation was about 4.4 years, not mentioning the social and environmental benefits.The innovation of this paper: The paper proposes a practical solar heating system to improve indoor thermal environment and reduce building energy consumption for heating and analyzes the performance of this system experimentally.