Experiment on active solar heating effect for monomer building in northwest region

Abstract: In the area of northwest China, the coal is the main fuel for heating, and the way for heating in rural area is traditional and backward, which has low energy efficiency and poor indoor thermal comfort. To make a good use of abundant solar energy to meet the requirement of indoor thermal comfort of monomer building in the rural area of northwest China, 2 monomer buildings are taken as the research objects, which are located at Zhangma Village, Minqin County, Gansu Province, and the area of each building is 117 m2. One of them is regarded as the experimental building with the external wall insulation transformation, and the other is regarded as the reference building. The experimental building uses solar powered radiator heating system and solar powered low temperature floor heating system in 2 heating seasons respectively, and both of the 2 systems are driven by a forced circulation. The solar collecting system consists of 6 evacuated tubular solar collectors; the collectors are connected in series, and each one is made up of 40 vaccum tubes. The reference building uses coal-fired boiler powered radiator heating system which is driven by a natural circulation. The stability of energy supply, the indoor thermal comfort and the thermal economic performance are studied by testing for 3 kinds of heating methods. The test has been done from December 1, 2014 to March 31, 2015, and from December 1, 2015 to March 31, 2016. The following parameters are measured: solar radiation on the collection face of solar collectors, hot water temperature in solar collector, indoor temperature and relative humidity, inlet and outlet temperature of heat pipe, ambient temperature, and flow rate of circulating water, which are recorded by the computer automatically. The experiment results indicate that the low-temperature solar floor heating is the best. Firstly, after the floor heating system takes place of the radiator heating, the number of the days with using the solar heating is significantly increased, the number of the days with using the coal-fired boiler is significantly reduced. It shows that the system has a good ability for resisting disturbance from its surroundings, and it is obvious that the stability of energy supply has been improved. Secondly, when the minimum ambient temperature is ?10 ℃, the indoor average temperature of experimental building can achieve 14 ℃, the indoor relative humidity of floor heating is maintained at 51%-60%, while the indoor relative humidity of radiator heating is maintained at 47%-65%. Compared with the radiator heating, the indoor temperature and relative humidity of floor heating are more stable and have smaller fluctuations, so it has better thermal comfort. Finally, the daily average heat-collecting efficiency of solar collector is related to the average daily temperature difference between hot water and ambient air. After taking place of the radiator, the average daily temperature difference of hot water and ambient air is reduced, so the daily average heat-collecting efficiency is improved. In the second heating season, the solar fraction increases from 30.8% to 60.3%, the quality of the saved coal is 2372.4 kg, and the reduction of CO2 emissions is 6.22 t, which show that the solar floor heating has a better energy-saving property; it is also an environment-friendly heating method, and the payback period is about 3.34 years. So this system can basically satisfy the continuous and stable heating demand in winter for the monomer building, which has a broad application prospect and will be worth popularizing in the northwest regions.