Experimental study of the passive and active performance of real-scale composite PCM room in winter

•Real-scale composite PCM room was built to study its passive and active performance.•The composite PCM room can improve indoor thermal environment in passive manner.•Composite PCM room does not save energy for every setting temperature of A/C. Composite phase change material (PCM) room was to place two PCMs with different phase change temperature on different walls of the room. It was proved to be effective in improving the indoor thermal environment of passive small-scale (1 m × 1 m × 1 m) buildings located in hot-summer and cold-winter regions of China. However, thermal performance of the composite PCM room should be deeply studied in passive and active real-scale rooms. Two real-scale (2 m × 1.5 m × 2.7 m) and identical rooms were built in Suzhou China. Three cases of experiment were done. Case 1 was passive experiment. Case 2 represented the condition when the A/C was turn on only during the day. Case 3 was that the A/C was turn on only at night. The results show that the PCM room had a temperature drop of 2.9–7.3 °C during the day and a temperature rise of 0.5–4 °C at night compared to the ordinary room in case 1. When the A/C was set to 17 °C, 19 °C and 21 °C in case 2, after the A/C was turned off, the indoor air temperature of the PCM room was 0.3–2.5 °C, 0.6–2.8 °C and 1.1–5.7 °C higher than that of ordinary room. The values were 0–2.4 °C, 0–3.3 °C and 0.3–2.8 °C in case 3. The energy saving rate was 3.5% when the setting temperature was 17 °C in case 2, the value was 5.2% and 6.4% when the setting temperature was 17 °C and 19 °C in case 3. However, for other setting temperatures in case 2 and case 3, the PCM room consumed more energy than ordinary room. This research will give support to the suitable operation of the A/C system of the PCM room.