A novel approach to clean polygeneration using a triple-function compound parabolic solar collector

Progressive enhancements in the efficiency of solar collectors are a key concept for mainstream integrations in commercial and residential applications. While many research efforts have been directed towards enhanced heat transfer, multi-functional designs are mainly limited to photovoltaic-thermal collectors. This work explores the feasibility of producing hot water and air streams, as well as electricity, from a novel design of a triple-function collector (TFC). The CPC-shaped collector is integrated with photovoltaic (PV) cells above the absorber plate and copper tubes below it. A highly insulating and transparent aerogel cover forms a duct path for an air stream that helps cool down the PV cells. Using a validated numerical model, the TFC performance is mapped under different operating conditions with respect to three reference designs of single- and dual-function collectors. The results show that the PV cells decrease the optical efficiency by 9.8%, yet the heat gain in the air stream and the high-quality electricity output overcome this limitation, resulting in maximum overall energy and exergy efficiencies of 89.1% and 14.2%, respectively. The overall energy efficiency is enhanced at lower and higher inlet water and air temperatures, respectively, as well as higher airflow rates. Under all examined operating conditions, the proposed design was superior to water and water–air heaters by up to 21.1% in terms of energy efficiency. It also surpassed PV-integrated water-based CPCs by a maximum of 2.05% and was inferior at special settings of high air flow rates and high water-to-air temperature differences. However, drastic improvements in the exergy efficiency by more than 3.16 folds were noticed, compared to the three reference designs.