Water Curtain Fresh Air Energy-Saving Retrofit Project for a Communication Building in Weifang

Project Overview
A communication equipment room of Weifang Mobile has a high internal heat load. Located on the rooftop, the room also experiences significant heat transfer through its building envelope, leading to high air conditioning energy consumption and a consistently elevated PUE value. To accelerate progress towards this year's energy consumption control targets, this retrofit involved installing two sets of water curtain fresh air systems. This reduces the room's energy consumption and enhances energy efficiency, while also providing air filtration to effectively maintain air cleanliness within the communication room.

The retrofitted equipment room covers an area of approximately 123 m², with an IT power load of about 24.3kW. It was originally equipped with four 5-horsepower cabinet air conditioners and two 3-horsepower cabinet air conditioners, with a total rated cooling capacity of 63.5kW. Two of the 5-horsepower units were only operated during summer. After the retrofit, two water curtain fresh air systems were installed. During certain periods of transitional seasons and throughout the winter, these new systems provide cooling instead of the original air conditioning system. During summer, operation switches back to the original air conditioning system.

Solution Application
This project utilizes Aolan's Water Curtain Fresh Air Energy-Saving Retrofit System. The system includes an evaporative air cooler supply system, a centrifugal fan exhaust system, and an intelligent control system.

Outdoor fresh air is filtered and cooled via evaporative cooling by the evaporative air cooler before being supplied indoors. Hot and humid air from the equipment room is forcibly exhausted outdoors by the centrifugal exhaust fans. The intelligent control system collects indoor and outdoor temperature and humidity parameters via sensors. Based on these parameters, it controls the operation of the water curtain fresh air system and the original room's precision air conditioners. When conditions allow to meet the room's temperature and humidity requirements, the system prioritizes operating the water curtain fresh air system to maximize the utilization time of external natural cooling sources and reduce the runtime of the precision air conditioners, there by achieving energy saving and consumption reduction.

The cooling system for this equipment room includes three operational modes: Dry Mode Fresh Air, Wet Mode Evaporative Cooled Fresh Air, and Coordinated Precision Air Conditioning Mode.

(1) Dry Mode Fresh Air: Under low-temperature conditions, the evaporative air cooler and exhaust fans operate, intake and exhaust dampers open. Outdoor low-temperature fresh air is filtered and supplied into the equipment room, while hot, humid air is expelled by the exhaust fans. The fans operate at low frequency based on indoor temperature conditions.

(2) Wet Mode Evaporative Cooled Fresh Air: Under suitable climate conditions, the evaporative air cooler and exhaust fans operate, intake and exhaust dampers open. Outdoor fresh air is filtered, cooled via evaporative cooling, and then supplied into the equipment room, while hot, humid air is expelled by the exhaust fans. The fans operate with variable frequency based on indoor temperature conditions.

(3) Coordinated Precision Air Conditioning Mode: When outdoor conditions are hot and humid, and the water curtain fresh air system cannot meet the indoor temperature and humidity requirements, the water curtain system stops, and the intake/exhaust dampers close. The original precision air conditioning system is activated in coordination, operating according to its original design parameters to cool the indoor air via internal circulation.

Results Presentation
The project was commissioned in 2024. After debugging, it has been operating in good condition, maintaining a stable temperature and humidity environment in the equipment room. The annual electricity consumption of the room's air conditioning system decreased from 126,000 kWh to 56,000 kWh, achieving a significant energy saving rate of 55.5%.