"The ice stadiums of Beijing Winter Olympic Games adopt energy-saving refrigeration system and environment-friendly refrigerant, which has actively promoted the sustainable development strategy of the IOC. Among them, the use of carbon dioxide refrigeration system takes the lead in making environmental protection and sustainable demonstration for the world. The selection of r449a refrigerant will make Beijing Winter Olympic Games the refrigerant GWP of ice stadiums in the history of Winter Olympic Games The lowest (global warming potential) Winter Olympics. " Recently, relevant IOC officials praised the environmental protection choice in the construction of venues for the Beijing Winter Olympic Games. It is understood that seven ice stadiums and nine ice surfaces have been newly built and reconstructed for the Beijing 2022 Winter Olympic Games, all of which use environment-friendly refrigeration systems and refrigerants, of which five use carbon dioxide (R744) transcritical direct refrigeration systems and four use r449a refrigerants. After a series of testing activities and competitions, the high-quality ice surface of the ice venues of the Beijing 2022 Winter Olympic Games has been highly praised by the players of various events at home and abroad. In addition, the ice surface of the seven ice venues also has the characteristics of environmental protection and sustainability. The concept of "Green Olympics" runs through the ice making scheme from design to implementation. It is understood that at the beginning of the design of the ice making scheme for ice venues, r507 refrigerant was originally planned to be used. This refrigerant is widely used all over the world and meets the requirements of the Montreal Protocol for developing countries, but its GWP value is 3985, which is relatively high. In order to make the venues of the Beijing Winter Olympic Games more environmentally friendly and sustainable, with the support of the IOC and international experts, the Beijing 2022 Winter Olympic Games actively studied the international development trend and current practical technology of refrigerants, held discussions with well-known experts in the refrigeration industry at home and abroad for many times, and confirmed that two refrigeration systems can be selected: one is the carbon dioxide transcritical direct refrigeration system, Venues suitable for perennial ice making, such as the national speed skating hall; Second, the traditional refrigeration system is suitable for venues that do not need to make ice all year round, such as water cube, National Stadium, etc. Zhang Xinrong, a professor of Peking University and a well-known expert in the field of international natural working medium research, believes that the carbon dioxide transcritical direct refrigeration system has the advantages of high safety, low energy consumption and operation cost, environmental friendliness, and all heat can be recycled. It is one of the most promising working medium in the energy system of ice venues, which can make the cold and heat integration and efficient operation of the energy system of venues, It has broad application prospects all over the world. The ice making technical scheme of the national speed skating hall was repeatedly demonstrated by more than 10 academicians, top experts of domestic industry associations and construction representatives. In the discussion with ice making experts of the Beijing Winter Olympic Organizing Committee and the International Olympic Committee, the carbon dioxide transcritical direct cooling ice making technology was proposed. "The experts of the international individual sports organization once said that the national speed skating hall can meet the Winter Olympic competition standards by using the internationally used environmental protection ice making technology. However, after 18 months of exploration, the Chinese team turned over the refrigeration system data of the speed skating Hall of the previous winter Olympic Games, analyzed the advantages and disadvantages of all refrigerants in the world one by one, and finally came up with more advanced ice making technology." Said Song Jiafeng, an engineer involved in the construction of the national speed skating hall. Environmental considerations are the most important factor behind innovation. According to song Jiafeng, before the Beijing Winter Olympics, carbon dioxide transcritical direct refrigeration system had never been used in large ice venues all over the world. The ODP (ozone destruction potential) value of carbon dioxide refrigerant is 0 and the GWP value is only 1, while the carbon emission of traditional refrigerant is 3985 times that of the same amount of carbon dioxide refrigerant. After the waste heat generated by carbon dioxide refrigeration is recovered, 70 ℃ hot water can be provided for domestic hot water and dehumidification regeneration. Compared with the traditional refrigeration method, the national speed skating hall adopts carbon dioxide ice making, which can improve the energy efficiency by 30% and save about 2 million kwh of electricity a year. In terms of traditional refrigerant selection, relevant international organizations, such as the American air conditioning and Refrigeration Institute (AHRI), have determined that the alternative refrigerant corresponding to r507 at this stage can be r449a, and the GWP value of r449a is 1282, which is 68% lower than that of r507. Beijing National Swimming Center, National Stadium and Wukesong Sports Center are the main venues of the 2008 Summer Olympic Games, and will host curling and hockey competitions during the 2022 Winter Olympic Games. In response to the concept of "green, shared, open and clean", r449a refrigerant was selected after investigating equipment suppliers, design engineers and service providers. Experts in the refrigeration industry said that the use of r449a refrigerant is an example of taking positive measures to move towards the goal of environmental sustainable development without affecting the system performance and economic sustainability. (Xinhua News Agency)