Polyols as phase change materials for surplus thermal energy storage

• Storing low-temperature surplus thermal energy from industries, power plants, and the like, using phasechange materials (PCM) is an effective alternative in alleviating the use of fossil based thermal energyprovision. Polyols; of some also known as sugar alcohols, are an emerging PCM category for thermalenergy storage (TES). A review on polyols as PCM for TES shows that polyols have phase change temperaturesin the range of 15 to 245 C, and considerable phase change enthalpies of 100–413 kJ/kg. However,the knowledge on the thermo-physical properties of polyols as desirable PCM for TES design is presentlysparse and rather inconsistent. Moreover, the phase change and state change behaviors of polyols need tobe better-understood in order to use these as PCM; e.g. the state change glass transition which manypolyols at pure state are found to undergo. In this work preliminary material property characterizationwith the use of Temperature-History method of some selected polyols, Erythritol, Xylitol andPolyethylene glycol (PEG) 10,000 were done. Complex behaviors were observed for some of the polyols.These are: two different melting temperatures, 118.5–120 C and 106–108 C at different cycles and anaverage subcooling 18.5 C of for Erythritol, probable glass-transition between 0 and 113 C for Xylitol,as well as a thermally activated change that is likely an oxidation, after three to five heating/coolingcycles for Xylitol and Erythritol. PEG 10,000 had negligible subcooling, no glass-transition nor thermallyactivated oxidation. However a hysteresis of around 10 C was observed for PEG 10,000. Therefore thesematerials require detailed studies to further evaluate their PCM-suitability. This study is expected to be an initiation of an upcoming extensive polyol-blends phase equilibrium evaluation.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Energiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Energy Engineering (hsv//eng)

Nyckelord

Phase change materials (PCM) Polyols

T-history method

Material properties

Glass transition

Thermally activated change

Energy Technology

Energiteknik

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