Semi-3D transient simulation of a nanofluid-base photovoltaic thermal system integrated with a thermoelectric generator

Thermoelectric generators (TEGs) can produce electricity from the temperature gradients. A combination of TEG with photovoltaic thermal (PVT) systems can be a possible solution for the improvement of their electrical performance. To evaluate the feasibility of using TEG in PVT systems, a comparison between only the PVT system and PVT system integrated with TEG (PVT-TEG) is conducted using numerical simulation. A semitransient numerical code is developed by FORTRAN software to simulate both PVT and PVT-TEG systems. The governing equations are solved by Tridiagonal Matrix Algorithm (TDMA) using an implicit formulation discretizing by a center-differencing scheme. In this study, aluminum-oxide/water (Al2O3/water) nanofluid is selected as working fluid due to the performance improvement of the systems. Both energy and exergy analysis are conducted to estimate the performance of the nanofluid based PVT-TEG system. The results indicate that the PV unit in both PVT and PVT-TEG systems can generate nearly the same electrical power. However, the PVT-TEG system has 2.5%-4% higher overall electrical energy efficiency compared to only the PVT system. It has been found, in all considered parameters, the PVT-TEG system compared to the PVT system in terms of overall exergy efficiency shows a better performance, while in terms of overall energy efficiency shows poor performance. Furthermore, according to the parametric analysis, there is a direct relation between inlet temperature and photovoltaic (PV) plate temperature, whereas there is an indirect correlation between the inlet temperature and TEG sides difference temperatures.