No abstract

In this paper, the experiment simulates the salt gradient solar pond with heat extraction and that without heat extraction, setting temperature sensors in the solar pond to monitor the temperature change of each measuring point in real time, extracting heat in the low convective zone and nonconvective zone at the same time. The experimental results show that heat extraction can improve the heat storage capacity of solar pond. The heat storage of solar pond with heat extraction is 40.3% more than that without heat extraction according to the experimental results. The heat extraction can increase the overall thermal efficiency of the solar pond; the efficiency of solar pond with heat extraction and that without heat extraction is 22.2 and 28.7%, respectively.

Solar oven based on sunlight condensation is a promising energy conservation and sustainable solar thermal utility way. However, the temperature of solar oven is greatly affected by the sunshine conditions. In this research, adding phase-change heat storage layer in the solar vacuum tubular collector has been proposed, and the thermal performance has been numerically studied. The influence of the food initial temperature on the temperature distribution of the heat storage layer has been investigated. The results show that adding phase-change heat storage layer (u40 mm/80 mm  770 mm) makes the oven inner wall temperature 30 C-80 C higher than that without phase-change heat storage layer when the oven cavity temperature is at a constant of 100 C; and the oven inner wall temperature fluctuation caused by sunshine is obviously reduced from 100 C to 18 C-35 C. It indicates that the food initial temperature has little effect on the temperature field of the heat storage layer with the food initial temperature being 10 C-50 C. The analysis of the heat storage performance shows that the heat storage layer has a certain heat storage capacity in all seasons, and the daily heat storage is up to 2718 kJ.

A novel straight through vacuum solar energy collector with molten salt phase change thermal storage layer was proposed. Solar salt (60% NaNO3-40% KNO3) was used as phase change materials (PCMs), and the effect of phase change material layer on the thermal performance of straight-through type vacuum solar energy collector has been studied numerically. The results show that: A 13 mm thick phase change material layer was added to the collector tube with an outer diameter of 17 mm, and the heat storage was increased by 53.57%; when the solar radiation is stopped, a constant temperature of 4min-16min is maintained, and then the temperature drops more slowly than that without addition. Molten salt phase change layer can significantly reduce the influence of solar cycle and instability on the straight-through solar vacuum collector tube.