Beam splitting filters applied to thermally de-coupled solar photovoltaic/thermal (PV/T) collectors

摘要

This investigation was focussed on the implementation of spectrally selective beam splitting filters in hybrid concentrating solar PV/T collectors. The main aim of this thesis was to systematically conduct an investigation using fundamental thermal, optical and experimental engineering techniques to overcome some of the long-standing challenges of thermally de-coupled PV/T technologies.To efficiently utilise the entire spectrum, a general methodology for the solar spectrum partition in hybrid PV/T collectors was developed herein. To validate the results of the methodology, two different approaches have been investigated: (1) dichroic mirrors as reflective band-stop filters and, (2) nanofluids as band-pass filters. The design of (1) was addressed by using two different multilayers structures: SiNx/SiO2 and TiO2/SiO2. For (2), Ag/Si core/shell nano-discs were suspended in water creating a spectrally selective absorbing fluid. These methods were chosen because they have potential to ultimately be mass produced at low fabrication cost.A detailed optical and heat transfer model was developed for both approaches. Additionally, indoor and outdoor testing was carried out to validate the modelling results. Finally, a comparative economic model was presented to quantify the savings that could be achieved from different PV/T collectors using the methods detailed above. The experimental results were used as input in the economic analysis revealing that the hybridisation of a concentrated PV system using nanofluids as selective absorbing fluids could be an economically viable option.Overall, the author hopes that this study will enable further commercial development of PV/T collectors using beam splitting. In particular, nanofluids as selective absorbing fluids seems to be a promising approach to be investigated further as they are relatively inexpensive (as compared to thin film filters) and could be incorporated as the thermal receiver of high concentration solar PV/T technologies.