太阳集热和辐射制冷复合系统中的关键问题研究

A combined solar heating and radiative cooling system can gain heat energy during the day via photothermal conversion and cooling energy at night by radiating heat into outer space through the atmospheric window. This combined system exhibits better performance in terms of integrated utilization efficiency and multi-functionality. The spectral property requirements for the physical processes of solar heating and radiative cooling are different, and thus, enabling a conventional solar collector or radiative cooler to achieve the opposite function is impossible unless the spectral properties of some key components, such as the coating or the cover, are modified. Accordingly, this project proposes the principle of spectral distribution, which obtains the functions of both solar heating and radiative cooling in one module as well as explores optimization methods for the film and the optical structures. The project team attempts to manufacture the coating and the cover by applying the latest developments in micro/nanostructure materials. The manufactured components exhibit spectral selectivity close to that of the designed models. The heat transfer modeling based on the spectral distribution and the experimental setups will be built to study the optimization principles of the optical and thermal structures of the combined system, as well as to investigate the mechanism behind the coupling effect of the structures and the environmental parameters on system performances. The project team aims to simulate the annual performance of the combined system in different climate zones in China using the validated heat transfer modeling. The results of this study can provide guidance for the application conditions and the optimum parameters of the novel combined solar heating and radiative cooling system.

太阳能集热-辐射制冷复合系统可分别在白天进行光热转换获得热能，在晚上通过“大气窗口”向外太空辐射热量获得冷能，可明显提升单一系统的综合利用效率和功能。由于集热和制冷两种物理过程不同的光谱特性要求，如果不对涂层、盖板等关键部件的光谱选择性做出改变，现有的常规集热或者制冷模块都不可能同时实现另外一种功能。针对上述问题，本项目提出了同时满足集热和制冷功能的光谱分布原则，研究相应膜系和光学结构的优化设计方法，结合当前微纳材料科学的最新进展，试制可满足集热和制冷两种功能需求的光谱选择性涂层和盖板材料。建立基于光谱分布参数的传热学模型，搭建集热-制冷复合系统的实验平台，研究复合系统的光学、热学结构优化原则以及各种结构参数、环境参数对系统性能的耦合影响。利用验证后的传热学模型，对复合系统在我国不同气候条件下的年性能进行模拟分析，为新型集热-制冷复合系统的优化设计和适用范围提供参考。

平板太阳能集热模块和平板辐射制冷模块在结构上具有高度相似性，同时二者的功能和工作时间段具有充分互补性，这为二者结合于同一套模块提供了可能性。太阳能集热-辐射制冷复合系统分别在白天进行光热转换获得热能，在晚上通过“大气窗口”向外太空辐射热量获得冷能，可明显提升单一系统的综合利用效率和功能。针对太阳能集热与辐射制冷综合高效利用，项目组设计太阳能集热-辐射制冷复合系统，建立复合系统传热学理论模型，对复合系统在不同系统结构、模块倾角、天空条件、环境温湿度、季节等工况下进行了参数分析与综合性能研究，并且搭建了复合系统测试平台与研究平台，优化设计并组装构建了真空条件复合系统，还对集热-制冷复合系统与建筑一体化进行了研究。项目组探索了集热-制冷涂层和盖板光谱特征分布规律，对各种材料光谱特性做了模拟优化且依此制备出具有集热-制冷功能的多膜系结构，而且对静态光谱材料在集热-制冷复合系统中的协同管理策略上做了进一步研究。通过模拟，项目组对不同材料的集热-制冷复合系统在不同地区的复杂气候条件下的年性能进行了分析。项目组还对耦合太阳能光伏发电的集热-制冷系统开展了实验研究。