Space cooling energy consumption in residential buildings has tripled globally over the past three decades, leading to a significant increase in greenhouse gas (GHG) emissions and building operating costs. To reduce building cooling energy consumption, cooling energy can be recovered from domestic cold water (DCW) for space cooling by circulating DCW through thermally massive walls (herein “DCW-wall”) before regular household consumption (e.g., showers). This approach is more effective in cold climate regions since the DCW is cooler in these regions, yet its engineering design and effectiveness have not been evaluated previously. This study evaluated the cooling potential of DCW-walls in different operation scenarios (e.g., inlet temperatures, zone temperatures, and piping configurations). A typical DCW usage pattern and a daily amount of 1200 L were selected for evaluation. Three-dimensional transient thermal simulations were used to obtain the water outlet temperatures, average wall surface temperatures, and cooling potentials. The results showed that a DCW wall with a spiral piping configuration and DCW inlet at 12 °C can deliver 21.92 MJ of cooling energy daily to a zone at 25 °C. This amount of free energy can cover up to approximately 11% of the annual cooling energy demand of a four-person dwelling in Toronto, Canada, which has a warm and humid summer.
Space heating and cooling of buildings is a major contributor to the ascending trend of global energy consumption and greenhouse gas (GHG) emissions. A potential solution to reduce the space heating and cooling is to use buildings’ mass for active thermal energy storage (TES). Having air circulation between an active TES and its associated zones can significantly enhance their thermal coupling; however, reported research studies have not focused on this kind of active TES. To that end, this study aimed to evaluate the thermal performance of a ventilated block wall (VBW) in reducing space heating and cooling loads in cold-climate buildings. In this system, air is circulated between a zone and the voided cores of a VBW, where the air exchanges heat with the wall before returning to the zone. To have a generalizable assessment of the system’s performance, typical-day and annual energy analyses were conducted under various boundary conditions and air circulation speeds. The study found that for a typical day with significant temperature fluctuation, a VBW with a 2 m/s air circulation speed throughout the day can lead to 67% more net energy exchange (the sum of thermal energy storage and release) when compared to having no air circulation. The annual analysis compared the energy performance between a VBW and a traditional wood-frame wall in three different cold climates. The results showed that substituting a wood-frame wall with a VBW can reduce space heating and cooling loads by 35.1 kWh/m2 (wall surface area) for a mixed dry–cold climate throughout the year. Having cement plaster as interior finishing can lead to 9% more net energy exchange than having drywall, on average, for all zone air temperature profiles.
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