Techno-economic analysis of centralized and decentralized HVAC systems for cleanrooms

Sammanfattning

Cleanrooms in the pharmaceutical industry are energy-intensive environments where HVAC systems account for roughly 50-75% of energy use due to high air changes per hour and strict conditioning requirements for indoor humidity and temperature. This thesis presents a techno-economic analysis comparing two of the most common HVAC system types. These systems are centralized, using one large AHU to provide airflow and conditioning, while the other, decentralized system with filter fan units, provides per-room airflow and air conditioning. This thesis uses a quantitative approach to study fluid dynamics in cleanrooms, validating pressure cascades, temperatures, and variables such as age of air, and includes a detailed technical design for a centralized system. The findings reveal a significant difference in energy performance: the decentralized system uses 218 MWh annually, whereas the centralized system requires 1 607 MWh annually. This discrepancy is primarily driven by the decentralized system’s ability to provide per-room conditioning and its significantly lower ductwork resistance, leading to a superior Specific Fan Power. CFD simulations further highlighted that while both systems maintained the required pressure levels, internal heat gains from packaging machinery in cleanroom 1 raised the temperature to 21.3 °C, near the design limit of 19 °C ±3 °C. This suggests that high Air Change Rates alone cannot compensate for insufficient localized cooling capacity. This study concludes that while a centralized system requires a lower initial investment, it quickly catches up to the decentralized system due to significantly higher operating costs.