Integrated Thermal Energy Storage System for Air-Conditioners with Phase-Change Composites: Paper No. 2116

Anurag Goyal, Eric Kozubal, Jason Woods

Research output: Contribution to conferencePaper


Thermal energy storage (TES) is a promising solution to store and dispatch energy and shave peak electric load, reducing the operational cost of HVAC systems. We present results of a TES system using phase-change materials (PCM) integrated with an air conditioner. The proposed system uses an organic PCM (tetradecane) encapsulated within compressed expanded natural graphite foams referred to as phase-change composite. The graphite foam encapsulates the PCM eliminating the need for expensive storage vessels, reduces installation costs, and provides higher thermal conductivity that can lead to faster charge/discharge rates. Two serpentines, multi-pass circuits, operating as a heat source and a sink, exchange heat to and from the phase-change composite. These two circuits are embedded in multiple slabs of this material. The "charge" circuit contains the refrigerant that is directly coupled to a vapor compression system, and the "discharge" circuit removes heat from an airstream and releases it into the PCM composite through a water-glycol liquid coupling. This configuration allows for multiple modes of operation depending on the state of charge of the thermal energy storage module, the building air-conditioning load, and the current electricity and demand charges. This flexible operation allows variable air volume capacity control without the need to have a variable capacity refrigeration system. We developed a 21 kW-hr (6 RT-hr) prototype TES system coupled with a commercial air-conditioner to characterize the component-and system-level performance.
Original languageAmerican English
Number of pages10
StatePublished - 2021
Event18th International Refrigeration and Air Conditioning Conference - West Lafayette, Indiana
Duration: 13 Jul 202016 Jul 2020


Conference18th International Refrigeration and Air Conditioning Conference
CityWest Lafayette, Indiana

NREL Publication Number

  • NREL/CP-5500-79605


  • air-conditioning
  • building energy efficiency
  • buildings
  • composite phase-change material
  • system integration
  • thermal energy storage


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