【作者】 赵洋；

【导师】 高丹；

【作者基本信息】 华北电力大学(北京) ， 动力工程及工程热物理， 2022， 硕士

【摘要】 作为太阳能综合利用的方式,太阳能光伏光热(PV/T)技术通过回收太阳能电池发电时产生的余热,可降低太阳能电池温度而提高其效率,并实现热电联产,在节约用地的同时实现对传统太阳能热水器及太阳能电池板的部分替换,促进分布式太阳能利用的高质量发展。聚光光伏光热(CPV/T)作为一种光伏光热一体化技术,利用聚光镜结构来显著增加太阳能电池表面接收到的太阳能能量密度,配合有效的冷却措施,在节约太阳能电池的同时,能够提高太阳能电池效率,并提供更高品质的热能。本文通过对原设计的CPV/T组件进行数值模拟,考虑改善原设计缺陷,提出了一种较紧凑的换热结构。具体研究内容如下:首先,根据对原设计CPV/T组件物理模型的分析,建立了一种光电热耦合的模拟流程。对比实验数据,出口水温、输出电流和输出功率值的计算误差均在5%以下,验证了该模拟流程可用于后续研究。通过该模拟流程,发现以导热流体冷却为基础的原设计组件由于流体温度从流道入口处开始逐渐提高,换热效率会逐渐下降,太阳能电池组件的温度也因此逐渐上升。因此,可通过相变材料吸收大量热量而温升不高的特性,在无需额外水泵耗功的情况下,利用导热流体与相变材料的传热温差逐渐升高带来的导热量增加,实现回收热量效果的互补。接着,根据分析采用相变材料层设计取代原组件玻璃流道底,实现与导热流体的直接热量交换,进一步提高整体性能。通过所建立的模拟流程,选取相变材料高度、导热流体中纳米流体的质量分数、相变材料中纳米颗粒的质量分数和导热流体流速作为独立自变量,采用响应面法对该相变材料辅助的CPV/T组件性能进行拟合。拟合所得的各多项式的显著性水平P小于0.05,平均误差小于2.5%,残差均落在红线内且分布随机,具有统计学意义并可以很好地预测结果。与原设计的比较表明相变材料层的加入进一步回收了太阳能电池散失的热量,提高了电效率,并可减少组件向环境散失的热量,验证了相变材料在CPV/T中的可用性。最后,以特斯拉阀型流道对对流换热的强化作用为基础,结合相变材料与特斯拉阀型流道设计了一种更为紧凑的换热结构,并对关键的换热性能进行了模拟分析。结果表明该结构相较于原设计可有效降低最高温度,并提高温度分布的均匀度,有利于太阳能电池性能的提升及消除组件运行时的热应力。同时,变热流密度的模拟结果表明该结构可用于中/低倍聚光技术在标准电池板上的应用。更多还原

【Abstract】 As a way of comprehensive solar energy utilization,solar photovoltaic/thermal(PV/T)technology can reduce the temperature of solar cells and improve their efficiency by recovering the waste heat generated during solar cell power generation,and realize cogeneration,which can save land while achieving partial replacement of traditional solar water heaters and solar panels,and promote the high-quality development of distributed solar energy utilization.Concentrated photovoltaic/hermal(CPV/T),as a photovoltaic/thermal technology,uses a concentrating mirror structure to significantly increase the solar energy density received on the surface of solar cells,and with effective cooling measures,it can improve solar cell efficiency and provide higher quality thermal energy while saving solar cells.In this paper,a more compact heat transfer structure is proposed by numerically simulating the original design of CPV/T module and considering the improvement of the original design defects.The details of the study are as follows.First,based on the analysis of the physical model of the original design CPV/T module,a simulation process coupling optical,electrical and thermal models is established.Comparing the experimental data,the calculated errors of outlet water temperature,output current and output power values are below 5%,which verifies that the simulation flow can be used for subsequent research.Through this simulation flow,it is found that the original design module based on thermal conductive fluid cooling will gradually decrease the heat transfer efficiency due to the fluid temperature gradually increasing from the inlet of the flow channel,and the temperature of the solar cell module will gradually increase as a result.Therefore,it is possible to achieve a complementary heat recovery effect by using the heat transfer temperature difference between the heat transfer fluid and the phase change material,which increases gradually,without additional pumping power consumption,because the phase change material absorbs a large amount of heat without a high temperature rise.Then,according to the analysis,a phase change material layer design is adopted to replace the original component glass runner bottom to achieve direct heat exchange with the heat-conducting fluid and further improve the overall performance.Through the established simulation flow,the phase change material height,the mass fraction of nanofluid in the heat-conducting fluid,the mass fraction of nanoparticles in the phase change material and the flow rate of the heat-conducting fluid are selected as independent independent variables,and the response surface method is used to fit the performance of this phase change material-assisted CPV/T assembly.The significance level of the fitted polynomials is less than 0.05,the mean error is less than 2.5%,and the residuals fall within the red line with random distribution,which is statistically significant and can predict the results well.The comparison with the original design shows that the addition of the phase change material layer further recovers the heat dissipated from the solar cell,improves the electrical efficiency,and reduces the heat dissipated from the module to the environment,which verifies the usability of the phase change material in CPV/T.Finally,a more compact heat transfer structure is designed by combining phase change materials and Tesla valve-type flow channel based on the enhanced effect of Tesla valve-type flow channel on convective heat transfer,and the key heat transfer performance is simulated and analyzed.The results show that the structure can effectively reduce the maximum temperature and improve the uniformity of temperature distribution compared with the original design,which is beneficial to the improvement of solar cell performance and the elimination of thermal stress during module operation.Simulation results of the variable heat flow density also show that the structure can be used for medium/low concentration technology on standard solar panels.更多还原