Solar heat recovery system using CO2 as working fluid

This article proposes a solar water heater system induced by natural convective flow using supercritical CO2 as a working fluid. The proposed solar water heater can produce thermal energy as hot water from solar thermal energy without any electric power consumption. In order to investigate the characteristics of the system, the dynamic characteristics and heat transfer property of the supercritical CO2 flow are measured when the inclination angles of the solar collector are changed. The current results indicate that the circulation of CO2 flow in this solar heater system can be easily induced by natural convection even if the solar collector angles are changed from 30° to vertical against gravity direction. The heat recovery efficiencies of this system are 86.5%, 68.5%, and 58.8% at the collector inclination angles of 30°, 60°, and 90°, respectively. Keywords: Carbon Dioxide, Water Heater, Natural Circulation, Solar Radiation, Solar Heat Recovery.