no21_kv_pc.png no21_kv_pc.png

Published on MHI Graph (October 2012 Issue)

White Text Half

Meeting Complex Requests with Technological Excellence: the Centrifugal Chiller Elites

For the Marina Bay Area Cooling System

The task of district heating and cooling systems is a big one: to supply both hot and chilled water to office buildings and hotels in order to heat or cool them accordingly. One system has the capacity of several thousand residential-use air-conditioning units and uses far less energy than what would be required if multiple individual heat sources were installed. Because of their benefits, these systems are currently being introduced around the world. MHI received its first order for a large district cooling plant at Singapore's New Downtown at Marina Bay, then under development, in 2002. At present, there are a total of 14 of the plant's main engines, centrifugal chillers (Note 1), in operation, and the plant provides air conditioning for the whole Marina Bay area, including its resort facilities and business center. In 2012, MHI received its third order from the city. On this project, the customer had a new request: they required a single unit that could run as both a conventional cooler and a thermal storage system. One group stepped up to answer the call: MHI engineers who had invested tireless enthusiasm in these centrifugal chillers.

  • 1The centrifugal chillers used as the main engines for district heating and cooling systems. Refrigerant is evaporated, compressed, condensed and expanded inside the machine, in a cycle that produces chilled water for use in cooling.
  • Photo Top: Marina Bay, Singapore's New Downtown, where international resort facilities are springing up

A Leader's Job: Discovering and Fulfilling Requests

Photo:Members of the Centrifugal & Absorption Chiller Department who build chillers boasting world-class cooling efficiency
(Left) Akihiro Takemoto, Senior Engineer, Engineering Section
(Center) Yasuhiro Ikeno, Electrical Team, Engineering Section
(Right) Yoshinori Shirakata, Engineering Manager, Engineering Section
Air-Conditioning & Refrigeration Systems, Centrifugal & Absorption Chiller Department

Singapore's level of environmental awareness is one of the highest in the world. In recent years, environmental performance assessment criteria have been established for buildings as well, and tenants who occupy buildings that meet these strict low-energy standards consider it an honor. District cooling systems handle the air conditioning for these buildings and, as you can imagine, they are expected to be extremely energy efficient. Marina Bay symbolizes the remarkable growth of Singapore's economy, and it's this area that Yoshinori Shirakata oversees, as the current project leader. He serves as an intermediary between MHI and the customer, unearthing customer needs and proposing technologies to fill them. When a customer is very concerned about performance, in addition to the regular sales department, engineers like Shirakata meet with them. Shirakata describes the weight of this particular responsibility: "The results earlier engineers produced in the first and second projects won the customer's trust for us. Their demands are quite strict, but I think it's because they have high expectations of our technology. We have to respond to those demands and create fertile ground for the next project." In fact, the requirements on the second project were stricter than those on the first, and that isn't all: on this third project, Shirakata ran up against a new problem.

The electricity market in Singapore is becoming progressively liberalized; the price of electricity changes every thirty minutes, and on occasion, it‘s so cheap it’s very nearly free. Creating an ice thermal storage tank during this time slot and using it in the cooling process facilitates huge energy savings. Understandably, then, the client requested a single-unit centrifugal chiller that can operate in two ways: in chilled water mode, in which ordinary chilled water does the cooling, and in ice-making mode, where antifreeze cooled below freezing is used to produce ice in an ice thermal storage tank. The unit also had to be compact, and to have a capacity of about 3,700RT (Note 2). To Shirakata, the double evaporator method - in which the unit is equipped with separate evaporators for chilled water mode and ice-making mode - seemed the best path to efficient operation. "It was technologically possible, but we'd never done it for such a high-capacity unit. The installation space was also a problem," Shirakata remembers. "For those reasons, when we met with the customer during the design stage, we drew layout diagrams and offered proposals for designing in limited spaces." The result: Through its technology and ingenuity, MHI fended off other companies and was awarded its third order.

  • 2RT=Refrigeration ton: a unit of refrigeration capacity for centrifugal chillers. One RT is roughly the capacity of a single residential air conditioning unit.

Constructing Complexity

When forming his project team, Shirakata put Akihiro Takemoto in charge of designing the machinery and Yasuhiro Ikeno in charge of controls. Takemoto was a specialist who had supervised the centrifugal chillers at the Yokohama Minato Mirai 21 District and Narita Airport. Ikeno was constantly designing products under development and products on order, and he always responded quickly. Shirakata felt no hesitation in choosing either of them. 

Takemoto had previously worked on a small capacity double evaporator chiller for a different client, and he says the experience came in handy on this project. "Last time, we ran into a problem where the chilled water devices were accidentally frozen during icemaking operation, damaging the machine. This time, we kept the pipe layout simple and carefully isolated the evaporators for ice-making operation and chilled water operation." Its large capacity meant the size of the machine itself became a source of headaches for the team. "The machine's total height is over 6 meters, but during assembly, we had to be accurate to within less than 1 millimeter. We had been careful when designing it, but at the site, its size often meant we needed to change the design, and that meant making adjustments. Every single time, we redesigned and made adjustments. The staff members on location joined in during the assembly and helped us resolve the issues."

Photo:Members of the Centrifugal & Absorption Chiller Department who build chillers boasting world-class cooling efficiency
Members of the Centrifugal & Absorption Chiller Department who build chillers boasting world-class cooling efficiency

The double evaporator method used on the project involved many heat exchangers, which multiplied Ikeno's problems. "The diagrams for the controls alone covered 600 pages: that's how complex the program was. As the person in charge of the controls, what I dreaded most was making a mistake there that could end up damaging the machine itself. This particular structure was difficult in that, if some issue during ice-making operation caused the water for chilled water operation to freeze, it could very well damage the machine. We had to design a program that would prevent damage even if a mechanical issue like that came up; it was really nerve-wracking."

Shirakata, Takemoto, Ikeno, and the other engineers' efforts took shape, and finally, the day of the performance test arrived. Representatives from the customer had come to Japan to witness the test, and under their watchful eyes, the machine performed brilliantly. The customer said that "MHI always creates products that deliver the performance we're looking for, but this time, they really nailed it." They even approached MHI with an inquiry about the next project. Remembering the delight he felt, Shirakata says, "Of course we want it to perform well during the trial operation. Then we want the customer to be satisfied when it's in operation. For that very reason, the trust we earned with this project has led to another order, and that really felt like the best thing that could have happened for us, the engineers."

Supplying the Products People Need

The engineers put their experience to work and made the customer's requests a reality. Takemoto describes his interest in the job: "We're able to take charge of the whole production cycle, from product design until the finished product performs. It's a big responsibility, but it's very satisfying work."
"Our products aren't just used for cooling: they're also used in air conditioning for factories, which require strict humidity and temperature controls. The idea that our 'monozukuri' (manufacturing) has laid the foundation for the next round of 'monozukuri' really makes it feel worthwhile." Ikeno adds, "The world needs chillers. In that sense, fulfilling each customer request and creating products leads to being useful to people and helping the environment. MHI does all the work on the control infrastructure as well as on the mechanical components, so we're often able to respond to a wide range of customer requests. That's what creates opportunities for us to acquire more customers."
Finally, their leader, Shirakata comments: "There will always be a need for air conditioners. Always. That's why we want to propose our highly reliable centrifugal chillers to customers and facilitate future projects. We also want to pass our generation's experience on to the younger workers, give them a chance to be active overseas and increase the number of people to work alongside us." Shirakata's eyes are on the future. With Marina Bay as a foothold, MHI plans to expand its centrifugal chillers into neighboring countries and new markets. These engineers will generate trust on the global stage, which will no doubt lead to further recognition and increasing popularity.

Photo: Marina Bay, Singapore's New Downtown
Centrifugal Chillers