With the continuous development and utilization of clean energy, the thermal utilization of solar energy is an important research direction. In view of the problems of the low utilization rate of solar heat in alpine regions of solar energy, an air-type vacuum-tube solar collector (AVSC) with air as the heat-exchange medium was designed. The vacuum tube of the solar heat collector adopted a double-pass spiral direct-current structure, and the vacuum tube had a built-in heat-storage rod. In order to test the heat collection performance of the designed air evacuated-tube solar collector, a heat collection performance test of the collector was conducted. The results showed that the average heat collection efficiency of the vacuum tube solar collector without phase-change heat-storage rods was 38%. The evacuated-tube solar collector using water as the heat transfer medium had an average heat collection efficiency of 58%. The average equivalent heat collection efficiency of the AVSC with a built-in phase-change heat-storage rod was 61%.

With the rapid development of industrialization, the excessive use of fossil fuels has caused problems such as increased greenhouse gas emissions and energy shortages. The development and use of renewable energy has attracted increased attention. In recent years, solar heat pump heating technology that uses clean solar energy combined with high-efficiency heat pump units is the development direction of clean heating in winter in northern regions. However, the use of solar energy is intermittent and unstable. The low-valley electricity policy is a night-time electricity price policy. Heat pump heating has problems such as frosting and low efficiencies in cold northern regions. To solve these problems, an exergy analysis model of each component of a phase-change heat-storage coupled solar heat pump heating system was established. Exergy analysis was performed on each component of the system to determine the direction of optimization and improvement of the phase-change heat-storage coupled solar heat pump heating system. The results showed that optimizing the heating-end heat exchanger of the system can reduce the exergy loss of the system. When the phase-change heat-storage tank meets the heating demand, its volume should be reduced to lower the exergy loss of the tank heat dissipation. Air-type solar collectors can increase the income exergies of solar collectors.

In this paper, we have overviewed the research conducted to date on phase change materials (PCMs) for photothermal power collection and storage, especially their applications as building materials. In order to facilitate their melting/curing heat transfer process in solar thermal utilization, the design of a latent heat storage system and related facilities is critical. A comprehensive comparison between organic and inorganic PCMs is made to help choose suitable materials for specific applications. Various technologies to enhance heat storage, such as fins, packaging, and multiple (cascaded) PCMs, are discussed in depth. In the end, the current existing problems are summarized, and promising research directions are proposed. This brief review could provide a clear guideline for the future development of PCM utilization in solar energy and related fields.

Thermal storage technology has received increasing attention under the policy of encouraging the development of renewable energy and new clean energy. Optimizing the heat exchange system of phase change thermal storage heat exchangers to obtain better performance has become increasingly urgent. This study comprehensively investigated the actual process of heat transfer and assessed the heat transfer correlation laws between the heat transfer fluids, heat exchange tubes, fins, and phase change materials. Taking the heat exchange efficiency of the heat exchanger as a guide, a simulation was conducted on the effect of the presence and quantity of fins as well as the flow rate of the cooling liquid on the heat exchange efficiency of the heat exchanger. The simulation results showed that too many or too few fins were not conducive to improving heat transfer efficiency. In addition, no positive correlation was observed between the flow rate of the cooling liquid in the heat exchanger and the heat transfer efficiency of the heat exchanger. Specifically, models with slightly slower cooling liquid flow rates had a higher heat transfer efficiency. After a sensitivity analysis, it was found that the number of fins had a more significant effect on the heat transfer efficiency of the heat exchanger than the flow rate of the cooling liquid. The heat exchanger with five fins and a cooling liquid flow rate of 0.1 m/s demonstrated the best heat transfer effect, achieving a temperature drop of 14.76% within 5 min.

With the adoption of "Carbon peak and carbon neutrality" in China, parabolic trough solar collectors have attracted considerable research attention. This study proposed an experimental system scheme based on a system to test the thermal performance of PTSHCS s in Lhasa. Furthermore, a series of experimental studies were conducted on the system which is used to test the collectors' thermal performance in the plateau environment. The actual operation data of the collector under typical weather conditions was collected, and the collector's thermal performance in plateau environment was analyzed. The results revealed that the solar radiation intensity, the temperature of the oil at the inlet of metal collector tube, and the flow rate of the oil to transfer heat were closely related to the heat collection efficiency of PTSHCS. A strong positive correlation exists between the solar radiation intensity and the thermal efficiency of the collector. When the rate of the fluid to transfer heat increased from 5m ଷ /h to 7m ଷ /h, the thermal efficiency of the collector increased significantly, and the maximum instantaneous thermal efficiency reached 66%. When the inlet temperature of the oil used to transfer heat increased from 80°C to 170°C, the thermal performance exhibited a general downward trend.