Boiler-free winter operation of semiconductor cleanroom HVAC systems using cooling water waste heat recovery

This study proposed and validated the boiler-free winter operation of semiconductor cleanroom heating, ventilation, and air conditioning (HVAC) systems using cooling water waste heat recovery. The proposed system reduced LNG consumption for the boiler by lowering steam demand. Unused thermal energy from chiller cooling water is repurposed for heating and humidification in the out air conditioner (OAC), thereby maintaining fresh air (FA) quality while minimizing energy use. A full-scale demonstration was conducted from December 2023 to January 2024 at a semiconductor fabrication (FAB) plant. During this period, boiler steam was entirely replaced by recovered heat without compromising cleanroom air temperature, humidity, or supply pressure, even under extreme winter conditions (−17.5 °C). Despite a slight decrease in chiller coefficient of performance (COP: 8.1 → 7.2) and an increase in pump current (158A → 183A), these were offset by reduced LNG consumption and the complete shutdown of cooling tower fans. As a result, the system achieved a 16.8% reduction in total energy consumption and an 8.6% reduction in CO₂ emissions. Additionally, stable system operation was verified through continuous infra equipment engineering system (I-EES) data monitoring under dynamic environmental conditions. This study demonstrates the technical feasibility and energy-saving potential of a closed-loop heat recovery strategy for HVAC systems in high-load industrial. This analysis also highlights operational trade-offs and lays the foundation for further optimization, including enhanced flow control and integrated multi-source heating. The findings suggest that the proposed system can serve as a scalable and practical model for carbon–neutral HVAC operation in semiconductor manufacturing facilities.