Synthesis and evaluation of green phase change materials for efficient air conditioning by tetrabutylphosphonium phosphate ionic semiclathrate hydrate

Taro Iwai, Takashi Miyamoto, Naruki Kurokawa, Atsushi Hotta, Ryo Ohmura

Research output: Contribution to journalArticlepeer-review

Abstract

A tetrabutylammonium bromide (TBAB) hydrate is the only ionic semiclathrate hydrate that has been commercialized as a medium for efficient thermal energy storage targeting general air conditioning. However, TBAB is an environmental pollutant, while liquid water and ice that have been widely used as conventional media, also have difficulty in increasing the thermal energy storage density as well as the coefficient of performance (COP) of a refrigerator to form solid. In this study, a tetrabutylphosphonium phosphate ((TBP)3PO4) hydrate was proposed as an alternative green medium. The dissociation heat and the phase equilibrium temperature, which were both crucial factors to evaluate the thermal energy storage density, and COP was experimentally determined. It was found that the maximum dissociation heat was 154.1 ± 2.0 kJ・kg−1 at the mass fraction of 0.309. The highest phase equilibrium temperature was 10.0 °C at the mass fractions of 0.290, 0.299, and 0.309. The thermal energy storage density of (TBP)3PO4 hydrates was 3.7 times larger than that of water. (TBP)3PO4 hydrates increased the COP of a refrigerator to form solid by 42% as compared with ice, indicating the potential size-reduction of conventional devices with the decrease in the power consumption of a refrigerator. The effective balance between environmental protection and the system performance through (TBP)3PO4 hydrates was also discussed.

Original languageEnglish
Article number104801
JournalJournal of Energy Storage
Volume52
DOIs
Publication statusPublished - 2022 Aug 1

Keywords

  • Ionic semiclathrate hydrate
  • Phase change materials
  • Tetrabutylphosphonium phosphate ((TBP)PO)
  • Thermal energy storage
  • Thermophysical property

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering

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