Experimental study on the effect of the ventilation and operation mode on the thermal efficiency of a full-scale Trombe wall under real operating conditions

Improving energy efficiency and occupant comfort in buildings is essential for reducing resource use and emissions. Trombe walls help achieve this by lowering heating demand through solar gains, though further research is needed to fully harness their potential. This study presents an experimental campaign carried out in winter on three parallel full-scale fan-assisted Trombe wall modules installed in an existing residential building in Turin, northern Italy. The three modules are characterized by different operating modes: a Thermal Buffer (TB) mode (closed cavity), an Indoor Air Curtain (IAC) mode, and a Supply Air Façade (SAF) mode (pre-heating outdoor air). The last two modes make use of a fan, providing a supply air flow rate of approximately 43 m³/h. An in-depth comparative analysis of the modules’ performance and heating efficiency was conducted. The results demonstrate that these systems can be considered sustainable and efficient strategies, pointing out the systems’ ability to effectively heat the air in the cavity in all three operation modes. Indeed, the air in the cavity reaches temperatures between 50 °C and 60 °C in the IAC and the SAF modes, and over 60 °C in the TB mode, while the air entering the building is mostly beyond 30 °C during the fan operation. For the IAC mode, system’s total efficiencies (accounting for gains from heated air and the massive wall) were reported as 12.6 % with partial façade shading and 18.4 % with no shading, while for the SAF mode, the relevant efficiency reaches 15.6 % with partial shading and 23.7 % with no shading.