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Reducing the heating and cooling system's impact on the environment meant boosting the energy efficiency of the chiller. To start, the team decided to update to an electric-driven system, and have it supply its own power through a gas cogeneration system*1.
Like the inverter found in most air conditioners today, we wanted this system to be electric-powered, so that it could adjust the motor speed according to load. This would improve energy efficiency.
Yasuo Uraki, General Manager, Large Tonnage Chiller Operation Division, Air Conditioning System Group, Hitachi Appliances, Inc.
Above all, we wanted to make it more efficient and also easy for the customer (Shinjuku District Heating and Cooling Center) to use. The answer we came up with was a new design with an inverter-driven centrifugal chiller.
Yasushi Nakamura, Senior Engineer, Large Tonnage Chiller Operation Division, Air Conditioning System Group, Hitachi Appliances, Inc.
Electric-driven systems offer advantages over conventional steam-driven systems that include easier control of refrigerating capacity and shorter system start-up time.
The project team's next task was to improve the heat exchanger. Through numerous revisions of the structure, certain points became clear: improvement would come by "rearranging" and "splitting" the chiller.
In this video: The improvements made in the chiller's heat exchanger are explained.
Mr. Nakamura and his team reduced power use by 8%, then achieved better efficiency by splitting the main chiller units. But when he set out to achieve even greater efficiency, he asked his elder, Mr. Uraki, for some advice. The response: a higher-precision compressor.
In this video: Mr. Yasuo Uraki of Hitachi Appliances describes how the team achieved its goal of greater efficiency.
The team also worked carefully to validate the compatibility of the inverter control. Finally, after many months of dedication, their inverter-controlled, high-efficiency turbo chiller was complete.