Pore structure modified diatomite-supported PEG composites for thermal energy storage

Area of Science:

• Materials Science
• Chemical Engineering

Background:

• Phase Change Materials (PCMs) are crucial for thermal energy storage.
• Polyethylene glycol (PEG) is a common PCM, but its application is limited by low loading capacity and leakage.
• Diatomite offers a porous structure suitable for encapsulating PCMs.

Purpose of the Study:

• To develop novel composite phase change materials (PCMs) by combining PEG with modified diatomite.
• To enhance the properties of diatomite as a carrier for PEG through various microstructural modifications.
• To evaluate the performance and stability of the developed composite PCMs for building applications.

Main Methods:

• Composite PCMs were prepared using a vacuum impregnation method with PEG and five types of diatomite.
• Diatomite microstructure was modified via calcination, acid treatment, alkali leaching, and nano-silica decoration.
• Alkali treatment (5 wt% NaOH at 70°C for 8 min) was identified as the most effective modification method.
• PEG loading capacity, thermal properties, apparent activation energy, and cycling stability were analyzed.

Main Results:

• The alkali-treated diatomite significantly increased PEG loading capacity to 70 wt%, a 46% improvement over raw diatomite.
• Nano-silica decorated diatomite achieved a maximum PEG load of 66 wt%.
• The apparent activation energy of PEG in the composite material was significantly increased.
• The composite PCMs demonstrated excellent thermal and chemical stability over 200 melting-freezing cycles.

Conclusions:

• The developed composite PCMs exhibit high latent heat, suitable phase change temperature, and good chemical compatibility.
• Modified diatomite carriers effectively enhance PEG loading and thermal stability.
• These composite PCMs show great potential for thermal energy storage in building applications due to their long-term reliability.