Abstract

To explore the optimized operating strategies coupling floor cooling with cold storage for thermal active systems (TABSs), effects of operating time on indoor thermal environment, cold storage capacity, energy use and running cost were studied. Simulations were conducted based on an actual office building equipped with floor cooling. To take full advantage of the TABS and off−peak electricity, four operating cases with nighttime floor cold storage were proposed, namely C1 (2:00–8:00), which operated only during the off−peak hours, C2 (2:00–10:00), C3 (2:00–12:00), and C4 (2:00–14:00), which operated during the off−peak and flat hours. A simulation case of C0 operating during daytime (7:00–17:00) was also proposed. Simulation results show that the C1 and C2 conditions with shorter operating hours result in higher indoor temperatures, which cannot ensure indoor thermal comfort. The PMV index in C3 and C4 conditions can be kept between −1 and 1, which meets the thermal comfort demand of Grade II. Considering that the operating duration of C3 is the same as the occupied hours, the cold storage capacity, cooling loss, cooling supply and release process, etc., of this case are further analyzed based on data of a typical day. The floor and ceiling slabs store most of the cooling energy (72.7%) during the night; inner walls also store part of the cooling energy (23.3%) and cooling loss during cold storage accounts for approximately 3.1%. During working hours, the cooling energy released is lower than the cooling load, which makes indoor temperatures increase continuously. Compared with case C0, case C3 has same power use while saving 2.8% of running costs. Case C4 provides a higher level of thermal comfort, while saving 0.9% of costs with a 1.5% increment in electricity use. This study provides detailed data about cold storage strategies coupling with floor cooling in TABS, which can be used to save running cost.

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