Performance of multi-surface concentrator applied in solar assembled mongolian yurt for energy supply

Assembled yurt has the characteristics of easy construction, convenient relocation and transportation, and can dynamically adapt to the changing climate of the grassland, actively adapt to the climate change, and more suitable for the modern grassland living environment, so it has become a residential type suitable for the grassland lifestyle. But the winter energy suppling of assembled yurts in cold regions mostly adopts biomass combustion and electric heating, which cannot meet the requirements of energy distributed utilization and green low-carbon sustainability. In order to solve the above problems, this paper proposes a novel solar multi-surface concentrated heating technology applied in solar assembled yurt energy suppling. It has several characteristics such as the solar thermal energy 'relay' transport, small heat transfer resistance, solar heating collection system integrated with enclosure of yurt and positive buoyancy gradient heat transfer. The technical operation principle and the structural curve of the multi-surface concentrator are introduced. The optical performance of the concentrator with time is analyzed with the optical simulation software TracePro. Under actual weather conditions, the effects of positive buoyancy gradient heat transfer and negative buoyancy gradient heat transfer on the thermal performance of the outlet temperature and heating collection in the concentrator are compared and studied. The results show that with the increase of the radial incidence angle, most of the incident and reflected light is received by the receiver, and less light escapes. When incidence angle is 0, the light receiving rate and concentrating efficiency of the concentrator are 95.00% and 76.96%, respectively. When the radial incidence increases to 15°, the light receiving rate and concentrating efficiency of the concentrator are 89.50% and 72.14%, respectively, and when the axial incidence angle increases to 30°, the light receiving rate and concentrating efficiency of the concentrator are 83.47% and 67.99%, respectively. In addition, the concentrating efficiency of adjacent concentrators with different orientations is superimposed at about 10:30 and 13:30, so these two moments can be used as three groups of concentrators start switching time, achieving energy supply of system stably and continuously. In winter sunny days, the outlet temperature of the concentrator with positive buoyancy gradient heat transfer and negative buoyancy gradient heat transfer has the same variation trend, which increases first and then decreases with the test time. However, due to the combined influence of the axial incidence angle and the heat transfer mode, the time of the concentrator with positive buoyancy gradient heat transfer and negative buoyancy gradient heat transfer to reach the maximum outlet temperature is inconsistent. The maximum outlet temperature and heating collection of the concentrator with positive buoyancy gradient heat transfer is about 21.3 ℃ and 787.29 W, which is 9.3℃ and 59.30% higher than that of the concentrator with positive buoyancy gradient heat transfer, and the total heating collection of the concentrator with positive buoyancy gradient heat transfer is about 5.46 MJ, 31.10% higher than that of the concentrator with negative buoyancy gradient heat transfer. In addition, the photothermal conversion efficiencies of the concentrator with positive buoyancy gradient heat transfer and negative buoyancy gradient heat transfer are 46.81% and 35.71%, respectively. This provides a reference for the matching of assembled yurt and energy supplying concentrator.