Performance analysis and multi-objective optimization of a hybrid photovoltaic/thermal collector for domestic hot water application

Highlights: • 3-D dynamic thermal-electrical models are developed and validated for PV/T. • 2-D temperature distributions of PV/T collector are illustrated and compared. • The dynamic response characteristics of different collectors are analyzed. • The comprehensive performances are studied under various operating conditions. • A multi-objective optimization is carried out for the design of PV/T DHW system. PV/T collector turns out to be a promising alternative for the traditional solar thermal collector for domestic hot water (DHW) application. In this paper, four comprehensive thermal and electrical models including unglazed PV/T, glazed PV/T, PV and flat plate thermal collector are established for the purpose of accurate long-term simulation and optimization. The detailed 2-D temperature distributions of the glazed and unglazed PV/T collector are illustrated and compared for the first time. Besides, the dynamic response characteristics of different collectors are discussed and compared. By running the models under a broad combination of the operating conditions, the comprehensive performances are obtained and found to be significantly influenced by flow rate, temperatures, radiation and wind speed. A multi-objective optimization model coupling TRNSYS and NSGA-II tool is established to study and optimize the PV/T DHW system for a complete year. The Pareto frontier of conflicting objectives (life cycle savings and prime energy saving efficiency) is obtained for the optimal system design. The mass flow rate on the Pareto frontier is between 0.0085 kg/s and 0.011 kg/s in this study. The optimal value of tank volume on Pareto frontier shows an equally scattering distribution between 99.5 L and 218.6Lfor a 2 m² glazed PV/T collector.