Study on the effect of inter-cellular gaps on the thermal profile of solar photovoltaic systems

Solar photovoltaics (PV) is a leading means of renewable power generation. One of the biggest challenges PV systems faces is the increase in cell temperature in the real field which leads to a reduction in its efficiency and lifetime. To propose a viable cooling method, it is imperative to study the thermal behaviour of PV systems using CFD modelling. Most of the researchers have modelled a PV module as a single or multi-layered cuboidal body, ignoring its internal geometrical complexities. This study implements an improved geometric model of a PV module that rightfully considers PV cells as different individual domains with encapsulant-filled intercellular gaps and investigates its effect in the obtained temperature profile vis a vis a conventional geometrical model. Conjugate heat transfer analysis is performed using an experimentally validated CFD model under three different wind speeds. K-ω SST and Surface to surface were used as turbulence and radiation models, respectively. The results reveal that the improved geometrical model consistently predicts higher cell temperature than the conventional model. For a PV module of 88% packing fraction and at a wind speed of 1m/s, the maximum and mean differences are 3.52ᴼC (or 6.52%) and 2.42ᴼC (or 4.65%), respectively. The values of these percentage differences remain approximately constant even at higher wind speeds. The incorporation of intercellular gaps also impacts the nature of the thermal profile by producing a greater difference of 3.35ᴼC (or 6.18%) in the prediction of the temperature of hotter cells compared to only 1.15ᴼC (or 2.31%) in the case of colder cells. This study suggests that the encapsulant-filled poorly conducting intercellular gaps have a considerable effect on the thermal characteristics of a PV system at all wind speeds and hence, should be incorporated into the geometry for more accurate and reliable results.