Phase change materials (PCMs) are substances that absorb, store, and release large amounts of thermal energy during solid-liquid phase transitions, typically melting at specific temperatures between 15-35°C. PCMs provide compact thermal storage, moderating temperature swings and reducing peak HVAC loads more effectively than sensible heat storage materials like concrete.
Properties and Applications
Common PCMs include paraffin waxes, salt hydrates, and fatty acids with latent heat values of 150-250 kJ/kg. Paraffin melts at 18-28°C with latent heat of 200 kJ/kg. PCMs can be integrated into wallboard, ceiling tiles, or gypsum boards for passive temperature moderation. Material cost ranges from $10-50 per kilogram, with building integration costs of $5-15 per square foot.
Performance and Limitations
PCM-enhanced building materials reduce peak room temperatures by 2-5°C and lower daily temperature swings by 30-50 percent. Effectiveness requires appropriate phase transition temperatures matched to building use patterns. PCMs reduce cooling energy by 10-20 percent in buildings with significant daily temperature variations. Main limitations include material cost, encapsulation durability, and degradation after 1,000-2,000 phase cycles over 10-20 years.