Small-scale experiments on the operational performance of a lightweight thermally active building system

Abstract

Thermally active building systems (TABS), which are integrated with the structure of a building, provide a robust approach for utilising renewable energy. However, reinforced concrete, where TABS are typically placed, is responsible for a significant proportion of initial embodied energy and related greenhouse gas emissions. Therefore, combining lightweight structural elements and thermal systems reduces initial embodied energy usage while retaining the active material’s thermal storage and heat transport benefits. The present experimental work explores the operational performance of a prototype of a lightweight TABS at ceiling level. A small-scale climate chamber was constructed and equipped to evaluate the prototype in the key operating modes. The study investigated the relationship between the supply temperature of the lightweight TABS and the climate chamber’s internal air temperature for active heating, active cooling and natural ventilation modes. The experiments compared the reaction time in active heating mode for a range of supply temperatures. In addition, we examined the dynamic characteristics of the thermal mass of the lightweight TABS in passive natural ventilation mode and passive cooling mode in the presence of an internal thermal load. The results provide insights into the dynamic performance in operation. In heating mode, we identified the time lag between the radiant surface achieving a steady state and the conditioned air reaching its target temperature. This feature emphasises the significance of refining control strategies when designing comfortable environments with low-temperature heating systems at ceiling level. Further, we highlighted the importance of balancing decisions on minimising embodied energy with the suitability of the selected material to leverage renewable energy sources. The experimental data can be used for validating high-resolution numerical models, which support the development of multifunctional elements with renewable energy sources for building heating and cooling.