Evaluation of the photon contributions to the solar energy conversion for organic luminescent down-shifting liquid beam splitters in hybrid photovoltaic-thermal (PVT) applications using raytracing Monte Carlo simulations

A hybrid photovoltaic-thermal (PVT) system combines photovoltaic (PV) and photo-thermal (PT) energy collection into a single structure, enhancing the potential to achieve greater solar energy conversion efficiencies. Such enhanced efficiencies can result in greater economic returns and could promote a larger uptake of PVT devices in cold and temperate climate countries. Through the utilization of a Monte Carlo ray-tracing model, this work provides new insights into the optical, electrical, and thermal characteristics of PVT devices. In particular, the work focuses on evaluating the behaviour of novel luminescent imidazole-phenanthroline-based working fluids that were previously experimentally investigated as liquid spectral beam splitters (SBS). The modelling procedure outlined here is able of providing an in-depth analysis of various categories of photons undergoing events such as transmission, absorption, parasitic absorption, and luminescent down-shifting (LDS) which, otherwise, are difficult or impossible to detect experimentally. Evaluating such photon characteristics provides the possibility to estimate the direct contribution of the luminophore (embedded within the working fluid) to the enhanced conversion efficiencies reported for PVT systems. In addition, the model can also allow for better tuning of the luminophore properties to match the main factors that are influencing the energy conversion dynamics of these systems. The current results indicate that the embedded luminophore is able of providing direct contributions of up to 91% for thermal power generation and 77% towards electrical power generation for the various concentrations of the liquid filters when compared with the individual performances of the independent PV or PT systems.