Concept of an autonomous night cooling system as an alternative to active mechanical cooling

Abstract

Modern building envelopes are largely static systems with limited ability to adapt to changing environmental conditions and occupant needs. While advanced insulation and low-U-value components have significantly reduced heating demand in new buildings, they have also increased cooling demand due to internal heat gains from occupants, lighting, and equipment. In highly insulated office buildings, cooling may be required even when outdoor temperatures are low, often dominating the overall energy balance. Night cooling offers an effective and energy-efficient strategy to maintain indoor air quality and thermal comfort by using cool nighttime air to dissipate stored heat. This paper presents the concept, design, and operation of an autonomous night-cooling system that integrates shape memory alloys as an alternate to active mechanical cooling systems. A prototype system was developed and tested in a climatic chamber under controlled temperature conditions, demonstrating the feasibility of temperature-driven actuation of lamellae. The limitations of the system, including hysteresis effects and environmental influences, are also discussed.