Comparison study of thermoclinic heat storage tanks using different liquid metals for concentrated solar power

Abstract

Liquid metals are good potential heat transfer materials for thermoclinic heat storage (THS) systems and will play an important role in the next generation solar thermal power system with higher operating temperature. This paper presents a comparative research work on the charging, discharging and mechanical performances of THS tanks based on four different liquid metal materials, which are lead (Pb), lead-bismuth alloy (PbBi), sodium (Na) and sodium-potassium alloy (NaK). The analysis results indicate that for both the charging and discharging processes, the lead-based THS tank can have the shortest operating duration, largest charging and discharging quantities (9.78 × 109 J and 9.21 × 109 J) as well as the highest discharging efficiency (94.17%), revealing its best operating performance. Relatively acceptable operating performances of lead-bismuth-based and sodium-based THS tanks are also demonstrated. Furthermore, in contrast with other three liquid metals, the lead-based THS tank also has the best mechanical performance. It has the smallest peak maximum mechanical stress of the steel wall (58.6 MPa). In summary, the lead-based THS tank has both the best heat storage and mechanical performances.