利用热力学模型研究光伏—热电复合系统效率提升机制

Thermodynamic Analysis of the Efficiency Improvement of a Photovoltaic-thermoelectric Hybrid System

太阳能电池和热电模块组成的复合系统有望获得较高的太阳能到电能的转换效率。本文利用热力学方法分析了由商业化太阳能电池构成的复合系统,并根据一维模型下能流输运特性计算了系统内各模块温度及其对转换效率的影响,发现低温度系数和低效率的太阳能电池可以通过构建复合系统获得更大的性能提升。同时,由于太阳辐照的有限性导致流经热电模块的热流受到限制,因此热电模块效率无法达到理想条件下的最优值。这表明复合系统的优化并非各个模块优化后结果的简单线性叠加,而需要考虑构成复合系统的各个模块间的约束条件进行整体计算和优化,即复合系统效率不仅与材料本征特性(如电导率、热导率等)有关,也和其工作状态(如入射太阳辐照强度、热电模块构成及几何尺寸、模块之间热学特性等)有关。上述模型与结果对于类似复合系统的设计有着指导作用。

A hybrid system formed by a photovoltaic module and a thermoelectric module has a great potential to enhance the solar-to- electricity efficiency. A mathematical model based on the first law of thermodynamics and the heat transfer analyses of the hybrid system is built, where the overall efficiency of the system is enhanced by optimizing the system as a whole. The model is used to study hybrid systems formed by commercially available photovoltaic modules and thermoelectric modules. It is found that, due to a limited incoming heat flux for the thermoelectric module, the overall performance of the hybrid system depends not only on the intrinsic properties of the materials forming such a hybrid system, but also on their working conditions, such as incoming solar radiation, geometry of each module, and interracial properties. The results indicate that only photovoltaie modules with low temperature coefficient and low efficiency can truly benefit from forming such hybrid system, and the optimization of a hybrid system must be done as a whole.