Energy conservation improvement and ON–OFF switch times reduction for an existing VFD-fan-based cooling tower. (15th September 2015)

• Record Type: Journal Article
• Authors: Chang, Chun-Cheng; Shieh, Shyan-Shu; Jang, Shi-Shang; Wu, Chan-Wei; Tsou, Ying
• Is Part Of: Applied energy. Volume 154(2015:Sep. 15)
• Page Start: 491
• Page End: 499
• Publication Date: 2015-09-15
• Subjects: Cooling tower -- Energy conservation -- Variable-frequency drive -- Zone control -- Approach; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2015.05.025
• Languages: English
• ISSNs: 0306-2619

Abstract

Highlights: Achieve energy saving and reduce the ON/OFF switching frequency at the same time. Propose a PI feedback controller with a temperature zone setting. Implement hybrid operations of rule-based and equation-based feedback control. Introduce larger approach for the setting of the outlet cooling water temperature. Abstract: The increasing economic advantage of replacing traditional two-speed fans with variable-frequency drive (VFD) fans has been gaining popularity in the industry. However, concerns regarding frequent ON/OFF switching and the lack of a well-devised controller have discouraged widespread adoption. In this study, a temperature zone method is proposed to replace the set-point method of fan control. Additionally, the highest output water temperature allowed in the process is set as the upper limit of a zone in order to further conserve energy. Both strategies are comprehensively analyzed for a virtual cooling tower that uses operational data from an existing VFD-fan-based cooling tower system in Taiwan. The results show energy savings of 38% for a 0.75 °C zone without increasing the ON/OFF switching frequency. The proposed strategies were further verified via an on-line field experiment. The proposed methods can be universally and easily applied to any existing cooling tower, and have significant implications for energy conservation if adopted globally.