Thermal modeling of hybrid concentrating PV/T collectors with tree-shaped channel networks cooling system

Excess temperatures in concentrating photovoltaic (PV) modules can lead to electrical efficiency loss and irreversible structural damage. Therefore, designing an appropriate cooling system is necessary to increase the lifetime and performance of concentrating PV modules. The basic design considerations for cooling systems include low and uniform cell temperature, minimal pumping power, high PV electrical efficiency and system reliability. In this paper, a 3D multi-physics computational model for a hybrid concentrating photovoltaic/thermal (HCPV/T) water collector is developed and implemented using the commercial FEA software COMSOL™. The collector consists of a solar concentrator, 40 silicon cells connected in series, and a tree-shaped channel cooling system with heat-recovery capability. Laminar flow and conjugate heat transfer through the tree-shaped branching channel cooling networks is investigated. The temperature profile along the cells is determined for different cooling strategies. Comparisons are made of the thermal and electrical operating conditions, such as the silicon cell temperature, electrical efficiency, and total pressure drop in the collector incorporating a tree-shaped channel network with a collector having a straight parallel channel cooling array. For the same total convective surface area and pressure drop (15Pa) in both configurations, the tree-shaped channel cooling networks yield a 10°C lower maximum cell temperature and a more uniform temperature distribution between the cells. In addition, the temperature distribution obtained in the collector with the tree-shaped channel cooling system reduces the `current matching problem' between the cells along the flow direction and reduces the thermal stresses significantly, thus increasing the reliability of the system.

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