Simulation Study on the Influence of Greenhouse Azimuth on the Thermal Environment of Solar Greenhouses

The azimuth of a solar greenhouse affects the lighting and the amount of solar radiation received. To investigate the influence of greenhouse azimuth angles on the thermal environment and to ensure an optimal temperature for the growth of warm-season crops such as tomatoes and cucumbers, a naturally ventilated solar greenhouse in Urumqi, Xinjiang was examined. Using computational fluid dynamics (CFD) software (ANSYS 2020), a model of the greenhouse under natural ventilation was constructed. Taking the indoor temperature as the evaluation index, the temperature field inside the greenhouse was simulated at two time points (11:00 and 17:00) during the daytime in spring, under different azimuths (8° west of south, 4° west of south, due south, 4° east of south, and 8° east of south). The indoor measured point temperatures at 11:00 and 17:00 over four consecutive days were compared with the simulated results. The MaxRE, ARE, RMSE, and MAE were all remained within a low range, verifying the accuracy of the constructed CFD greenhouse model. The temperature contour maps of different sections, as well as the indoor average temperature and temperature uniformity in each case, were compared and analyzed. The results indicated that, at 11:00, the greenhouses with azimuths of 8° and 4° east of south exhibited higher average indoor temperatures than those with azimuths of due south and west of south. At 17:00, however, the highest average indoor temperatures occurred in the greenhouses with azimuths of 8° and 4° west of south, exceeding those with azimuths of due south and east of south. The differences in temperature uniformity among different azimuths at the same time were small, but there were significant differences in the temperature uniformity at different times for the same azimuth. According to the climatic characteristics and the temperature requirements of crops of Urumqi, Xinjiang, an azimuth of 4–8° west of south is recommended for solar greenhouses in this region.