Experimental and numerical investigation of combined sensible–latent heat for thermal energy storage at 575 °C and above. (April 2015)

• Record Type: Journal Article
• Authors: Zanganeh, G.; Khanna, R.; Walser, C.; Pedretti, A.; Haselbacher, A.; Steinfeld, A.
• Is Part Of: Solar energy. Volume 114(2015)
• Page Start: 77
• Page End: 90
• Publication Date: 2015-04
• Subjects: Thermal energy storage -- Phase change material -- Packed bed -- Concentrated solar power; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2015.01.022
• Languages: English
• ISSNs: 0038-092X

Abstract

Highlights: A packed bed of phase change material (PCM) and rocks is used for heat storage. Air is used as the heat-transfer fluid. The concept stabilizes the outflow temperature for approximately 90 min. The stabilization is achieved with less than 5 vol.% of PCM. Abstract: The design, testing, and modelling of a high-temperature thermocline-type thermal energy storage (TES) are presented. The TES concept uses air as the heat-transfer fluid and combines sensible and latent heat for stabilizing the discharging outflow air temperature. A 42 kWhth lab-scale prototype of 40 cm diameter was fabricated, containing a 9 cm high layer of encapsulated phase change material (AlSi12 ) on top of a 127 cm high packed bed of sedimentary rocks with a mean diameter of about 3 cm. A two-phase transient heat transfer model of the thermal storage cycle was numerically formulated and experimentally validated with measured thermoclines during charging and discharging obtained with the lab-scale prototype. The thermal inertia of the experimental setup and the radial variation of void fraction due to the small tank-to-particle diameter ratio affected the validation process. The outflow air temperature during discharging was stabilized around the melting temperature of AlSi12 of 575 °C. The thermal losses stayed below 3.5% of the input energy for all the experimental runs.