Hydropower Generation by Solar Thermosyphon

摘要

Solar thermosyphon (TS) consists of thermal collector, condenser (recuperater), reservoir, and heat exchanger. The TS collects solar heat at the roof and carries it to the downstairs 4 m below the collector without using pumps. The working medium of the TS is water. Temperature of the collected heat ranges 70 to 80°C at the highest (low temperature heat). Hydropower generation using the TS was attempted for the first time. At present, the observed power output was 10~(-6) W in the order of magnitude for the solar irradiation of 500 to 1400 W and the thermal coefficient was in 10~(-9) level, very low. Since Carnot’s coefficient is 0.13 for the present heat sources, there is a great margin for the future improvement. The main reasons of such low efficiency were considered to be due to 1) lack of stability of the TS circulating flow, 2) losses of heat and fluid flow, and 3) improper design of impellors. A mathematical model of the TS performance was given. In the model main driving force of the TS is assumed to be the buoyancy force by the steam bubbles. Verification of the model is under study.