High-Efficiency Hybrid PV and Solar-Thermal Combined Cooling and Power Technologies

Abstract

Solar energy can be used to provide heat or to generate electricity (many land areas in the world have sufficient solar irradiance based on Figure 1). Most solar panels designed for one of these purposes, with electrical photovoltaic (PV) panels being typically less than 20% efficient. PV cells experience a deterioration in efficiency when operated at high temperatures, which occurs when the solar irradiance and generation from such systems are at their highest. Hybrid PV-thermal (PVT) solar collector technology combines PV modules with the contacting flow of a cooling fluid in a number of configurations, and offers advantages when space is at a premium and there is demand for both heat and power [1,2]. By far the most common use of the thermal-energy output from PVT systems is to provide hot water at 50-60 °C for households or commercial use, however, a much wider range of opportunities arises at higher temperatures (typically above 60 °C) where refrigeration cycles can be used. Meanwhile, non-concentrating solar thermal (ST) collectors, such as evacuated tube collectors (ETC), can be designed to operate with a high thermal efficiency in the range 80-200 °C, making them suitable for a wider range of thermodynamic power and cooling cycles, such as the organic Rankine cycle (ORC) and the diffusion absorption refrigeration cycle (DAR), which can be tailored to a particular solar heat source though careful selection of an appropriate working fluid [3,4]. In this work, we investigate two alternative system configurations for the provision of solar combined cooling and power (S-CCP) in a distributed domestic application. Both systems use the same reference household energy demand for cooling and power and are constrained by the same total available solar collection area.