Ice Ribbon, the National Speed Skating Oval, Takes the Lead to Adopt Qingdao Haier Carrier Transcritical Carbon Dioxide Ice Making Technology
The National Speed Skating Oval is the only new venue built for ice competition. It is surrounded by 22 curved glass curtain walls in the shape of a crystal ribbon, which is why it's been dubbed the “Ice Ribbon”.
The chief engineer of the Bird's Nest and the National Speed Skating Oval, Li Jiulin, introduced that the National Speed Skating Oval boasts a full ice design, with an ice surface area of 12,000 square meters, making it the largest ice surface in Asia so far. The cooling method in the “Ice Ribbon” can improve the efficiency by more than 20% than traditional methods and ensures a reliably uniform ice surface temperature and ice hardness. Those are key factors for high-level competitions timed by 0.001 seconds. Moreover, waste heat generated from ice making in the venue can be used for providing domestic hot water for athletes, snow melt pits, and ice resurfacing, saving about 2 million kilowatts of electricity a year.
It is known that the core equipment of the refrigeration system in the venue is transcritical CO2 racks provided by Haier Carrier.
In order to unveil the venue first adopting the transcritical carbon dioxide (CO2) ice making technology, our reporter made a special visit to Qingdao Haier Carrier Refrigeration Equipment Co., Ltd. in the Qingdao West Coast New Area.
More than a Decade of Technology Reserve Towards a Refrigeration Technology Breakthrough
Haier Carrier participated in the detailed design of the ice making system scheme, installation and commissioning of the system, and the first ice making task.
“Although carbon dioxide is more stable in nature and related ice making technology is more environmentally-responsible, fluorine refrigeration units are more commonly seen in China because of lower technology and development costs,” said Jiang Dianju, Director of Engineering and Development, Haier Carrier Refrigeration Equipment Co., Ltd. “The International Skating Union (ISU) stipulates that the ice surface temperature variances should be within 0.5 degree Celsius, and the ice surface must be level. Their requirements are very stringent. They place heavy demands on the integration including the control of ice making racks, intelligent refrigeration, refrigerant transfer and heat exchange. So choosing the right ice making method became the key to the problem. After many rounds of technical consultation and expert review, the National Speed Skating Oval selected the trans-critical refrigeration system with CO2 as a refrigerant.”
The construction of the entire venue is responsible by a consortium. Haier Carrier is responsible for providing core equipment - transcritical CO2 racks including commissioning.
“To meet the technical standards, the key is to have a very accurate grasp of the changes of CO2 in three forms, the design of valves, the application of compressors and a perfectly integrated terminal control system,” Dianju said. “Haier Carrier developed this world-class technology through over a decade of equipment and technology upgrades.”
Haier Carrier has many overseas clients. Around 2010, its European clients put forward rigorous environmental requirements, so Haier Carrier began the research and development of the transcritical CO2 refrigeration technology very early. The technology was also running in Metro’s cold storage warehouse and cold chain logistics.
Standing Out in Tests After Rounds of Specialized Commissioning
The first ice making task was completed in January 2021. Six transcritical CO2 racks, with a cooling capacity of 600 kilowatts (kW) each and 3,600 kW in total, have been working on ice making in the venue.
During the early stage of project design, Haier Carrier's technicians fully cooperated with the design institute to complete the optimized design of the system. During the system installation process, the company also assigned special personnel to provide on-site installation guidance. Engineering, R&D, application, and service personnel successively came to Beijing to optimize and debug the equipment. Sometimes there were more than a dozen people working on site at the same time.
The construction of the venue and essential equipment were inevitably affected by the coronavirus. It took less than one month from completing system installation to making the first ice, to the final task of ice making commissioning. The on-site commissioning team had to work against time. Finally, they overcame all difficulties and completed the commissioning of the ice making system at the end of December 2020 and completed the first ice making task at the beginning of January 2021.
Wang Xiaolin, site coordinator of Haier Carrier, said that the committee requires the venue to go through a trial period to test whether all the facilities meet the requirements before it is handed over to them. The “Ice Ribbon” has gone through two “tests” - the “Experience Beijing” ice sports testing program in April 2021 and the “Experience Beijing” Speed Skating China Open in October 2021. The IOC did not require extensive changes to the operating mechanism, design or system equipment. Now the entire venue has been completely handed over to the committee.
A Post-80s Young Man Safeguards the Core Equipment
Xiaolin faced a challenge with vacuumizing during the commissioning process prior to the first ice making task. The entire ice surface system is very large in scale, the coils are about 120 kilometers long. In addition, this is the first large-scale transcritical carbon dioxide system in China, so there is no case reference about vacuumizing.
According to domestic practice, a vacuum degree of 200 pascal (Pa) is the requirement of CO2 cascade refrigeration. So whether this parameter is applicable to the “Ice Ribbon” with 12,000 km of pipelines and more than 8,900 welds on the ice surface? After discussion and communication, Xiaolin still insisted that the vacuum degree must reach 60 Pa to ensure the best effect of CO2, which is much more demanding than using Freon and ammonia. But how to vacuumize such a large system to reach the 60 Pa requirement?
The team adopted a zoning vacuumizing method after many discussions with the design institute, construction company and experts. They divided the large system into small systems and units to vacuumize in batches, and then integrated the small systems and units into the large system. In this way, the vacuum degree in the final acceptance reached 45 Pa, which means the vacuumizing problem was solved without precedent and experience. More importantly, it only took about 20 days to successfully complete the first ice making task.
Xiaolin has once again returned to the “Ice Ribbon” and he will remain in Beijing until the competition conclude.
Ice making work for the competition began in January 2022. The surface will be open to athletes from all over the world for adaptation training. Xiaolin arrived at the “Ice Ribbon” to begin the ice making work in the central control room of the refrigeration plant. In addition to on-site coordination, he is also responsible for creating a 24-hour schedule for the technical team to perform safeguarding work during the competiton, to guarantee the ice making system working at high quality, high efficiency and a high level during the competition.
The core equipment must be safeguarded 24/7 until all competitions conclude. During the Games, the external network of the core equipment will be disconnected, so there is no way to know the operation status of the equipment through remote monitoring, we rely on the on-site personnel to ensure normal operation.
Xiaolin and the team feel very proud to do their part to honor China’s commitment to deliver environmentally-responsible and safe competition.
Nearly 12,000 square meters of the ice surface in the National Speed Skating Oval adopts the zoning refrigeration technology. The venue will be open to the public for ice sports such as ice hockey, speed skating, figure skating and curling to achieve sustainable venue operation.
