Thermal performance analysis of an existing building heating based on a novel active phase change heater

An active phase change heater is configurated to transform excess electricity at off-peak tariff periods into thermal energy, store and release it at the electricity on-peak tariff periods in order to accomplish heating demand towards an existing building with marine climate. Reliable numerical model is developed based on phase change heat transfer and convective heat transfer between phase change material (PCM) and indoor air. Objective temperature zone (18–24 °C) is achieved by means of an event control that is coupled with heat transfer model. Performance of indoor temperature, phase change characteristics and operating model of active phase change heaters during the building heating period are comprehensively evaluated. Results indicate that indoor temperatures are generally within thermal comfort range under various initial temperatures and air inlet velocities. Start-stop frequencies of PCM system increase while total working times decrease with the augment of air velocity. Liquid fractions of PCM decrease as studied time elapses and several parallel stages occur owing to intermittent operation of active phase change heaters. Parametric analysis reveals that thermal resistance is determined as the most decisive factor, followed by ambient temperature, PCM melting point and PCM thermal conductivity. Liquid fraction of PCMs declines to merely 0.074 when thermal resistance increases to 0.4 (m²·^oC)/W. In conclusion, studied results highlight correlation between building thermal performance and specific heat transfer characteristics of PCM, with substantial benefits to development of latent heat thermal energy storage available to building energy conservation.