Cogeneration Heat Sink for a Photovoltaic System

Abstract

The University of Arizona is heavily invested in transforming itself into a leader in sustainable practices. Among these efforts are the establishments of the “Practice School of Sustainability” and the SAGE Fund, both housed at the University of Arizona College of Engineering. This design report is an exhaustive analysis of designing and constructing a lowcost solar cogeneration system. Cogeneration refers to two-tiered energy output in the form of electricity and hot water. Benefits of capturing and utilizing waste heat from the photovoltaic panels are a more efficient electricity production capacity in combination to hot water generation. The aim of these efforts is to have a direct impact on campus utility costs, and to serve as a template for implementing future systems on a larger scale. The selected building to install the pilot system is the Optical Sciences West building because it has a high constant hot water demand for proper air handling. The design coconsists of 16 photovoltaic panels with a heat sink attached to the back of each panel, with a water and propylene glycol mixture flowing in a closed loop throughout each heat sink. If installation is approvedand the system performs as predicted, there will be an average output of 89.19 kWh per day in thermal energy. At a flowrate of 600 gallons of water per day, hot water will exit the system at 58.8 ?C. This translates to a savings of $1,391 per year in natural gas costs. The cogeneration system is also expected to have an electrical output of 33 kWh per day, translating to a $762 savings per year. Combined, the Cogeneration Heat Sink for Photovoltaic Panels 2 system is expected to save $2,153 per year and offset CO2 emissions by 10,938 kg per year. With a system cost of $18,490, the payback period for this pilot system is a mere 4.8 years. For scaling purposes in future installations, the design in its current form costs $2.35 per watt. Based on these favorable economic and environmental benefits, combined with minimal risks to safety or cost mitigation capability, it is highly recommended that more heat sinks be manufactured to facilitate this installation in the near future. If the system performs as predicted, future installations should take place on other campus buildings that use a variable air volume air handling system with terminal reheat.