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Abstract
Nearly 50% of global energy consumption is associated with meeting thermal requirements. Whilst some of this is heat goes to low temperature applications like hot water supply, there is also a huge demand for the supply of 100-250oC thermal energy for industrial and commercial applications which is currently met by gas and electricity. However, using innovative optical and thermal technologies, it can also (potentially) be met by concentrated sunlight from urban rooftop collectors, eliminating billions of kg of CO2 emissions per year. Hence, it may be possible to develop new, advanced collectors to substantially increase the amount of commercial rooftop solar energy harvesting.
At present, though, there are still some barriers to overcome to successfully collect large scale of 100-250oC thermal energy from rooftops. One key barrier for most concentrated solar systems is that integration with rooftops is relatively complex and cumbersome in comparison with photovoltaic (PV) panels. This requires a new type of concentrator which is efficient, low-cost and has a low-wind/aesthetic profile. These criteria point to thin concentrators that can be rack-mounted or laid flat on the roof with minimal balance of system requirements. The system should have similar geometrical features and appearance to PV panels and non-concentrating solar hot water collection panels, which are by far the most widely deployed solar collection systems to date. Such a concentrating collector has yet to be demonstrated.
As such, this study aims to advancing rooftop solar concentrating technology for commercial and industrial applications via the development of thin optical elements which avoid rotational tracking. During the course of the research, several innovative low-profile optical concentrators (<15cm in height) were designed, developed and systematically investigated to demonstrate their potential to deliver heat energy in the 100-250oC range. A series of experiments were conducted to validate these compact optical concentrator concepts and to demonstrate their performance as semi-passive, internal tracking and concentrating. An economic analysis was also performed to evaluate the feasibility of the final, optimized design proposed in this thesis. Overall, this study offers new optical platforms to advance the utilization of solar energy in urban areas.