Exergy-based optimization constraints for solar PVT panels and district energy systems with onboard green hydrogen production by solar prosumers

This paper highlights the significance of optimizing district energy systems with solar prosumers from an exergy-based perspective to minimize carbon dioxide emission responsibilities. As a case study, the Dezonnet solar district energy project in Haarlem, the Netherlands, which incorporates solar prosumers with traditional rooftop photovoltaic-thermal panels, and heat pumps, integrated with a district heating network featuring a seasonal central thermal storage aquifer, is critically examined. This paper shows that the project has carbon dioxide emission responsibilities that can only be revealed by the Second Law of Thermodynamics. A novel extension of this law relates carbon dioxide emission responsibilities with major exergy destructions. As an alternative solution, a solar/green hydrogen house concept is presented, which encompasses advanced, pumpless photovoltaic-thermal panels with heat pipes, solar flat-plate panels, and thermo-electric generator layers in a sandwiched construction with phase-change thermal storage blocks. On-site seasonal thermal storage systems utilizing phase change material and biogas generation replace the large-scale district aquifer. New optimization constraints as well as the objective function of minimum exergy destruction and corresponding emission responsibility equations are presented. Sample studies indicate that the alternative solution may reduce carbon dioxide emissions responsibility by up to 95%. This paper concludes that smaller districts or individual solar homes with advanced technologies are preferable.