Phase change with inner ventilation for energy management: roofs buildings in hot & dry climates case

Abstract

Demand for cooling in hot and dry climactic regions of the world is expected to increase rapidly, while the cost of cooling relative to household incomes and the associated environmental impact are relatively high. Previous studies have shown that the incorporation of phase-change materials (PCM) with active and/ or passive ventilation of the roof slab decrease the cooling energy demand on building interiors. However, the benefits of these technologies used separately and in combination have not been quantified for hot and dry climate. Using numerically validated dynamic thermal model that incorporates realistic local hourly weather data, this work for the first time quantifies the effect of introduction of PCM in combination with active ventilation inside the roof slab on the time-shifting and damping of thermal energy ingress into buildings for a typical city with hot and dry climate in Western India. We explored parameters such as the phase-change temperature, ventilation rate and relative mass of the PCM to understand the effect of these design interventions on energy ingress and temperatures. This paper presents the used model, its validation, and model predictions. The promising results indicate that the introduction of phase-change materials with a phase-change temperature below 36 °C with (or without) active ventilation can significantly reduce energy ingress by up to 75 %. These results are expected to inform designers of low-cost housing and other such buildings in similar climates.