A Low-Temperature Phase Change Material Based on Capric-Stearic Acid/Expanded Graphite for Thermal Energy Storage

Area of Science:

• Materials Science
• Chemical Engineering
• Energy Storage

Background:

• Phase change materials (PCMs) are crucial for thermal energy storage.
• Fatty acid-based PCMs offer good thermal properties but suffer from low thermal conductivity and leakage.
• Composite PCMs can overcome these limitations by incorporating thermally conductive additives.

Purpose of the Study:

• To prepare and characterize a composite phase change material (PCM) using capric acid (CA) and stearic acid (SA) integrated with expanded graphite (EG).
• To evaluate the thermal properties, compatibility, and long-term stability of the developed composite PCM for low-temperature thermal energy storage applications.

Main Methods:

• Preparation of a composite PCM with an optimal capric acid-stearic acid mass ratio (0.84:0.16) and 10 wt% expanded graphite.
• Characterization using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD).
• Evaluation of thermal conductivity enhancement, thermal stability, leakage prevention, and thermal reliability over 500 thermal cycles.

Main Results:

• The optimal mass ratio for the capric acid-stearic acid mixture was determined to be 0.84:0.16.
• The capric acid-stearic acid mixture exhibited good compatibility with expanded graphite.
• The thermal conductivity of the composite PCM (CA-SA/10 wt% EG) was 3.28 times higher than that of the pure CA-SA mixture.
• The composite PCM demonstrated satisfactory thermal stability, with no leakage observed.
• Excellent thermal reliability was confirmed after 500 thermal cycles.

Conclusions:

• The developed capric acid-stearic acid/expanded graphite composite PCM exhibits significantly enhanced thermal conductivity and excellent thermal stability.
• The composite PCM effectively prevents leakage and maintains its performance over numerous thermal cycles.
• This composite PCM shows great potential for efficient low-temperature thermal energy storage applications.