相变储热型光伏自驱动集热器运行特性

为了克服自驱动型太阳能空气集热器间歇运行和温度波动大的缺点，该研究提出了一种相变储热型自驱动集热器，并利用试验方法探讨了其运行特性。此外，并通过与无储热单元的集热器进行对比，分析了储热单元的引入对集热器热性能的影响。结果表明，该集热器实现了24 h连续运行，其在光伏-蓄电池供电模式下可以根据太阳辐射照度自适应调节气流量，全天热效率达46.92%。对比试验结果表明，储热单元的引入可降低集热器出口温度峰值，峰值滞后时间约3 h。结果可为开发适用于农业干燥领域的集热器提供新思路。

Operation characteristics of photovoltaic self-driven solar air collector with phase change material

In the field of agricultural drying, solar air collectors (SACs) can supply hot air to the drying chamber. There is a need for temperature control and continuous drying in agricultural drying processes. In practice, SACs have the disadvantage that the output temperature tends to fluctuate and fails to work at night because solar irradiation fluctuates during the day and is interrupted during the night. This makes it difficult to guarantee the drying quality of the crop without continuous drying. In addition, it is inconvenient for farmers in remote areas that the operation of SACs relies on the grid. Therefore, in this paper, a photovoltaic self-driven solar air collector (SDSAC) with phase change material (PCM) that can output heat throughout the day was set up, and the operating characteristics of it was investigated experimentally. This system used the electricity generated by the photovoltaic effect as the power for the fan of the collector. Furthermore, the collector operated in the absence of sunlight by storing the electricity generated by the photovoltaic panels on both sides of the device in a battery to drive the fan at night. At the same time, the integration of PCM achieved long-term heat supply and mitigated temperature fluctuations by transferring part of the daytime heat to the nighttime. In this paper, the temperature characteristics of the collector were discussed, including the temperature of the PCM, the plate and the internal air. Where, the temperature of the PCM away from the inlet rose more quickly and gradually released heat from 13:30 onwards. The temperature of the upper plate of the thermal storage container varied similarly to solar radiation during the day and decreased slowly at night due to the heat released from the PCM. The temperature of the internal air rose according to the flow after 14:00, reflecting the double-sided heating of the air by the thermal storage container. The experimental results showed that the operation characteristics of the collector was adaptable to the solar irradiation in the Photovoltaic-Battery mode, with a full-day thermal efficiency was 46.92%. The collector in the Photovoltaic-Battery mode run at a higher flow rate during the day, which provided timely heat output and avoided heat accumulation. Moreover, the collector maintained a lower flow rate when there was no energy input at night to avoid a rapid drop in output temperature. Finally, the thermal performance of the SDSAC with and without PCM was analysed. The available experimental data showed that the introduction of PCM could effectively mitigate peak outlet temperature and maintained a temperature difference of 5 K even at night. It was worth noting that the SDSAC with PCM had a 24-hour heat loss. In practice, it is recommended that insulation measures should be taken at night for the SDSAC with PCM to improve thermal efficiency. The operating features of this novel SAC make it suitable for agricultural drying.