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Energy shortage and environmental pollution have led to the wide use of clean and renewable energy. A ground source heat pump (GSHP) is extensively utilized in the new building of various renewable energy, because of its energy saving, high efficiency and environmental friendliness. However, the current GSHP development is limited to a certain extent, due mainly to its high cost, and large land areas resulting from drilling boreholes. Alternatively, the concept of an energy pile was proposed to combine the GSHP exchanger of ground heat with the pile foundation of a building. However, the temperature change of pile body can result in the thermal expansion and contraction of an energy pile, thereby to induce the pile deformation in the actual operation of energy piles. This variation of temperature has endangered the structural safety of energy piles, particularly on the thermal performance and bearing capacity. Therefore, a feasible energy pile with phase change concrete has been selected, where a type of phase change material (PCM) can serve as a part of filling material in a traditional energy pile. The thermal performance of the energy pile with phase change concrete was greatly enhanced, indicating the weak temperature variation and deformation during the heat exchange, due largely to the invariable temperature and the latent heat release during the phase change of PCM. In this study, a 3D numerical model of energy piles with phase change concrete was established to evaluate the thermo-mechanical characteristics of a whole energy pile under thermal-mechanical coupling loads. A systematic analysis was made to compare the thermo-mechanical characteristics of traditional energy pile and the new one with phase change concrete. An experiment was conducted to explore the effects of the distance between two legs of U-tube, and the ratio of length to diameter of pile body on the thermo-mechanical behavior of an energy pile with phase change concrete. The results showed that the solid-liquid phase change of PCM increased the heat exchange rate at the per unit depth of pile by 10.3%, while reduced the changes in the temperature of pile body. There was a reduced changes in the displacement, axial force, and side friction resistance of pile body that caused by the temperature change. With the increase of distance between two legs of U-tube, the heat transfer rate and heat influence range of soil increased in the energy pile, while the axial force of the pile decreased, as well as the pile displacement first increased and then decreased. An increase in the ratio of length to diameter improved the total heat exchange rate of energy piles, but reduced the heat exchange rate at the per unit depth of pile, while increased the pile top displacement, which was not conducive to the stability of the energy pile. The experimental validation showed that the predicted relative errors of middle temperature in the pile wall and displacement at the pile top were within 5.1% and 12%, respectively, and the average relative errors were 4.2% and 9.9%, respectively. Therefore, the developed numerical model of an energy pile can be used to simulate the thermo-mechanical characteristics of an energy pile with phase change concrete. [ABSTRACT FROM AUTHOR]

In this study, we analyzed the effects of different drip irrigation regimes under plastic film on sugar beet yield and water use efficiency in Xinjiang of China. Drip irrigation under plastic film had been widely used in the arid areas of northwest China, especially in Xinjiang for saving water and fertilizer, increasing temperature of soil and preservation of soil moisture. The drip irrigation regimes of sugar beet under plastic film had a significant effect on increasing sugar beet root yield compared with traditional irrigation regimes. Two irrigation water quota (45 mm, 60 mm) and three irrigation frequency (eight, nine, ten) were combined to six treatments based on traditional drip irrigation regimes of sugar beet under plastic film in Xinjiang for suitable drip irrigation regimes under plastic film. The experiment was conducted during 2016 and 2017 at the Sugar Beet Improvement Center in Manasi, Xinjiang. The effects of different irrigation treatments on height and weight of sugar beet, leaf area index, root yield, sugar yield, percentage of sugar content, soil water content, evapotranspiration and water use efficiency were investigated. The water consumption of sugar beet was indicated combined with the soil water content and the suitable drip irrigation regimes under plastic film was proposed. The results showed that the increase of irrigation frequency could increase leaf area index, weight of sugar beet root and root yield, decreased percentage of sugar content and had no significant (P> 0.05) effect on evapotranspiration and sugar beet water use efficiency. The increase of irrigation water quota were not significant effect on leaf area index and percentage of sugar content, increased weight of sugar beet root and evapotranspiration and decreased water use efficiency of sugar beet. In addition, The SPAD value was decreased as the increase of irrigation water quota and irrigation frequency. By irrigation frequency and water quota interaction, the root yield of 45 mm and 60 mm irrigation water quota at frequency of eight were significant decreased, and percentage of sugar content and water use efficiency of 45 mm and 60 mm irrigation water quota at frequency of eight were decreased for the soil relative water content were under 50%. The soil relative water content was under 50% for 45 mm irrigation water quota at frequency of nine, and was more than 50% when 45 mm irrigation water quota at frequency of nine increased 15 mm. The weight of root yield was increased and root yield was increased by 7.4%-7.7% with the sugar yield increased by 9.4%-9.7% as the increase of 15 mm of 45 mm irrigation water quota at frequency of nine. The height of sugar beet, leaf area index were significant (P<0.05) higher than other irrigation frequencies for ten irritation frequency which the soil relative water content was more than 50%. The ten irrigation frequency was not significant (P>0.05) compared with nine irrigation frequency at 60 mm irrigation water quota, but the sugar yield of sugar beet was significant (P<0.05) less than nine irrigation frequency for 60 mm irrigation water quota. As increased 15 mm irrigation water quota for ten irrigation frequency at 45 mm irrigation water quota, the evapotranspiration was increased, the water use efficiency was decrease and root yield, percentage of sugar content and sugar yield of sugar beet had no significant difference. The results indicated that the nine irrigation frequency at 60 mm water quota was the suitable irrigation regimes of sugar beet under plastic film in Xinjiang for the lack of rain and sufficient sunshine, which saving 10% irrigation water compared with traditional irrigation regimes of sugar beet under plastic film. [ABSTRACT FROM AUTHOR]