Pore-scale analysis on selection of composite phase change materials for photovoltaic thermal management

Composite Phase Change Materials (CPCMs) using metal foam as core material are highly promising for thermal management of photovoltaics. Selecting a proper CPCM for a given application is challenging. To address this, we developed a pore-scale lattice Boltzmann model based on X-ray micro-Computed Tomography to describe the complicated microstructures of the metal foam and computed the dynamic temperature and flow fields in representative applications. Two important parameters for the design of PCMs, melting temperature and latent heat, are discussed in this work by comparing the melting fraction, energy density, and power density for different CPCMs. Further, we demonstrate a CPCM choice for thermal management of a tilted photovoltaic panel. By comparing the thermal behavior of four different paraffin based CPCMs having similar thermophysical properties but different melting temperatures and latent heats, the effects of melting temperature and latent heat are illustrated for a practical application. Compared with the highest latent heat (Stefan number Ste = 0.1), energy density is reduced by 31.8%, 52.0%, and 63.5% for the other three cases with Ste of 0.15, 0.22, and 0.3, respectively, while the melting time is extended, with the reverse order. Besides, a lower melting temperature leads to a quicker response at the early melting stage, while this quick response is short-lived. Thus, the choice of melting temperature should balance the benefits of excellent initial thermal control against the risks of loss of control later. The results of this work help establish an effective strategy toward material selection of CPCMs.