Study Of The Direct-gain Solar Heating In Remote Southwest Tibet

The space heating energy supply for the houses located in remote southwest Tibet such as frontier stations, civilian houses and so on, is difficult because of the backward economy, poor transport condition and sadly lack of conventional fossil energy such as petroleum and natural gas. And the development of conventional space heating will be certain to bring enormous pressure on the fragile ecological environment. But Tibet is the richest in solar energy resource because of the high altitude and high visibility in China. So passive solar heating without auxiliary heating source is proposed to be applied due to the low cost and easy maintainability. Steady state thermal analysis and numerical simulation were combined to study how to reach space heating demand without auxiliary heating source from the two respects: average and minimum indoor air temperature.Firstly, the passive solar house design method without auxiliary heating source was proposed. Cauchy-inequality was used to optimize the allocation of each envelope thermal resistance. The optimized relationship of the thermal resistance is: The heat transfer coefficient correction factorε_i of non-transparent envelope was calculated. Under the impact of intense long-wave radiation and the solar radiation, the heat transfer of the building envelope with different orientation shows a strong non-uniform characteristic. The heat loss of the north wall is about 60% bigger than that of south wall when the solar radiant surface absorptivity is 0.7 for the same thermal resistance.Secondly, the simulation program for the passive solar house with movable insulation layer for windows on the plateau was established based on the enthalpy model. And the optimized guideline to open or close the insulation layer was put forward. The program was verified by the experimental data. The simulation results show that: (1) double clear glazing with movable insulation layer is the suitable choice for the south direct-gain window. The insulation layer should be closed just at sunset and be opened at sunrise; (2) as the inner surface convective heat transfer coefficient hin on the plateau is smaller than that on the plain, the passive solar house has bigger indoor air temperature fluctuation.Thirdly, the optimization for the application of the shape-stabilized phase change material (SSPCM) floor in passive solar house was conducted for the goal of raising the minimum indoor air temperature Tin,min. The optimization algorithm is making the SSPCM just solidifies completely when the room is coldest through adjusting the melting temperature.Finally, the expanded graphite was added into the SSPCM to enhance the thermal conductivity because the tiny graphite nodule can be connected with one another to form high thermal conductivity path in the SSPCM. And the mass production process of the SSPCM with high conductivity was developed.