Full-spectrum solar energy harvesting for power and heat production using dichroic mirror

Solar energy has the potential to fulfil the world’s energy needs if it is exploited efficiently. Energy from the sun can be converted directly to electricity by photovoltaic cells (PV) or it can be converted thermally by concentrated solar power. In recent years, PV technology has become more attractive thanks to the considerable reduction in its costs. However, PV cells cannot convert all of the energy in the solar spectrum, due to their inability to utilise low energy photons and the thermal energy produced through thermalization by high-energy photons. This leads to lower harvesting of the full solar spectrum energy. Under continuous illumination, the temperature of PV cells can increase up to 40°C above ambient, which affects their performance and durability. Therefore, integrating a PV cell with a thermal collector in a PV/Thermal hybrid system that can supply both electrical and thermal energy is an attractive solution. Over the past few decades, research has focused on coupling photovoltaic systems with solar concentrators, such as parabolic trough and parabolic dish systems. Effective thermal management of photovoltaic cells will enhance their conversion efficiency and prevent material deterioration. Given that commercial PV cells have an efficiency of 15–20%, a large proportion of solar energy dissipates as heat in the cells, which can be collected by a thermal receiver. The overall performance of these cells can be enhanced using a thermoelectric generator (TE) to capture waste heat that cannot be utilised by the PV cells. In this study, new designs of hybrid PV-TE systems based on spectral beam splitting and solar concentration are proposed. Experimental investigations using the beam splitting technique show that there is an improvement in the overall power generation of the PV-TE hybrid systems compared to the bare cell. Two designs were investigated and compared in terms of their design, performance, and economic viability. The comparison reveals that the dish hybrid system is better than the trough system because it facilitates the use of a smaller thermal absorber. Insulating the thermal absorber of the hybrid system was also investigated to examine the effect of reducing heat loss to the surroundings on the thermoelectric power generation. The results show that a 13.3% improvement in the thermoelectric power generation can be achieved. A theoretical model was developed to optimize the geometry of the thermoelectric generator to maximise the power output of the PV-TE hybrid systems. The results of the model calculation show that a significant improvement of the thermoelectric performance can be achieved under a vacuum environment. Finally, recommendations based on the outcomes of this research to improve the performance of these hybrid systems are presente