Development of Solar Thermal Harvesting Technology Which Meets the Needs of Industry

Abstract

Rooftop integrated solar thermal systems can potentially supply medium to high temperature (100-400 Degree Celsius) heat to industrial and commercial applications. A key barrier for conventional concentrated solar systems is that integration with rooftops is relatively complex and cumbersome. To avoid wind loading issues and for ease of installation, low-profile collectors with form factors similar to photovoltaic panels were examined in the present study. In order to advance the field of solar thermal technology for commercial and industrial applications, this study investigated the potential for utilizing compact optical and thermal concentrators. As a major aspect of this study, an innovative low-profile optical concentrator (<10 cm in height) was designed, developed and systematically analysed. As another potential path for innovation, thermal concentrators (e.g. passive solar receivers consisting of heat pipes and highly conductive fins or solar receivers integrated with active thermoelectric heat pump elements) were explored in this study. Also within this research, the effect of modifying the absorber from a standard selective surface (black chrome-coated copper tube) to a selective volumetric absorber (nanofluid contained within ITO-coated glass tube) was investigated. Several avenues for improvement for both receivers and the entire design were identified from these analyses. Due to the fact industrial demand may not match the transient operation time of concentrating thermal collectors, the integration of latent thermal storage in its limited free space was also investigated. To minimize the cost, shell-and-tube storage units were analysed for their technical feasibility in a characteristic industrial application. The optimum configuration was found to provide a solar fraction of ~60% and an annual charging efficiency of ~100%, indicating technical feasibility for this integrated collector/storage (ICS) system. Lastly, the techno-economic feasibility of these innovations for air-conditioning application was investigated. Overall, this study reveals that the proposed low-profile collector with/without an integrated storage could meet the needs of industrial and commercial heating applications. Due to the fact that solar-derived industrial heat production is an emerging market, it was ultimately found that a nominal amount of further research and manufacturing cost reductions could potentially help these types of systems to realize unsubsidized economic viability going forward.