Low-energy resilient cooling through geothermal heat dissipation and latent heat storage

Abstract

Conventional passive cooling techniques provide limited benefits in extremely hot climates in southern Asia, characterised by high daytime and night temperatures and frequent climate-related disruptions, such as power cuts. This study proposes and demonstrates a novel low-energy and resilient cooling solution for extremely hot regions in southern Asia. The novelty lies in the combination of geothermal heat dissipation and latent heat storage, specifically designed for the particular conditions of extremely hot climates in Southern Asia; considering the influence of climate-related disruptions such as power cuts, whose frequency is increasing in the region; and using discomfort hours as an indicator to measure the passive survivability of buildings in the absence of air-conditioning (following the adaptive comfort model). A numerical model was developed in TRNSYS for optimal sizing and configuration of the phase change material (PCM) integrated into a ceiling panel using a typical multi-family building archetype in three climatic regions of Pakistan. A parametric numerical analysis was performed concerning different PCM melting temperatures, amount of PCM, convective heat transfer capacity, and equivalent thermal conductivity. Moreover, daytime was considered the period with a higher probability of power cuts. The results showed how integrating PCM-based ceiling panels with geothermal heat dissipation can mitigate discomfort hours by 28 % in extremely hot climates, 55 % in very hot climates, and 91 % in hot climate areas with intermittent access to electricity. Latent heat storage maximised the benefits of geothermal heat dissipation by extending thermal comfort periods by 13 % and 18 % in extremely hot and very hot climates compared to the scenario without PCM. This low-energy resilient cooling solution, integrating PCM as a cool battery, can keep the home cool for longer when electricity is unavailable. This study demonstrates the importance of considering the specific climate-related disruptions from these extremely hot regions in building design, such as extreme heat events or power cuts, to enhance the heat resilience capacity of cities.