The opening of the Beijing Winter Olympics has entered the countdown, and the major venues have successively completed the ice and snow making. This is the first time that the mainland has hosted the Winter Olympic Games, and there is no experience and cases of ice and snow making that meet the Olympic standards. As the "blood" of the Winter Olympic venues, where does the ice and snow come from, and can it meet the requirements of the Winter Olympic Games?
As a major landmark event held after the mainland put forward the "double carbon" goal, the Beijing Winter Olympics will implement the concept of "green Olympics" in the whole process of preparation, showing the world the responsibility and responsibility of major countries. How to develop a green and low-carbon ice and snow making system and produce efficient domestic ice and snow falls on the shoulders of the refrigeration "national team" - COFCO Engineering Beijing Division.
COFCO Engineering Beijing Division (Huashang International Engineering Co., Ltd.), its predecessor, the Design Institute of the Ministry of Commerce, is a leading design unit for industrial and commercial refrigeration technology in mainland China. In preparation for the Beijing Winter Olympics, COFCO Engineering Beijing Division specially set up an ice and snow team to undertake the design of the ice and snow making system of the five core venues of the Winter Olympics, represented by the National Speed Skating Hall, the National Bobsleigh Center and the National Alpine Ski Center.
"In order to implement the concept of 'green Olympic Games', when we design the refrigeration system of the Winter Olympic venues, in addition to considering the green environmental protection of the refrigerant, we also need to consider the low energy consumption requirements for the long-term operation of the refrigeration system, that is, to take into account environmental friendliness, low carbon energy saving and stability and reliability." Wang Bin, founder of the ice and snow team of COFCO Engineering and head of the Winter Olympics project, said that at present, the ice and snow making of the venues responsible for COFCO Engineering has been delivered through actual measurement and inspection, contributing a green, low-carbon and efficient "China plan" for the ice and snow of the Winter Olympics.
Apply natural refrigerants to create green ice technology
Unlike outdoor ice rinks, which rely on natural cooling, all ice events at the Winter Olympics are held indoors. The indoor ice rink adopts artificial ice making methods, which can strictly control the temperature and humidity of the ice surface, creating a fair competition environment for athletes and a basis for challenging the limits.
National Speed Skating Hall Ice Making. Courtesy of COFCO Engineering Beijing Division
The National Speed Skating Hall is the main venue of the Beijing Winter Olympics and hosts speed skating competitions. Wang Bin said that in the holding of international top winter events, if there is the slightest flaw on the ice, it may affect the athletes' performance. Every inch of ice should be smooth and flat, and the temperature should be balanced, and the ice making system hidden under the ice surface is particularly critical.
In 2017, the ICE and Snow Team of COFCO Engineering began to participate in the pre-technical exchange and post-design of the ice making system of the National Speed Skating Hall. The principle of the ice making system is similar to the home "geothermal heating", in which several refrigeration pipes are placed under the ice surface, and the ice surface is cooled by the flow of refrigerant in it. Refrigerants play an important role in ice making, and what kind of refrigerant is used and what kind of system is used to make ice has become the key to the green construction of the National Speed Skating Hall.
When the national speed skating hall ice making scheme was first discussed, the conventional ice-making technology scheme of Freon refrigeration + glycol colding, which was commonly used in the venues of the previous Winter Olympic Games, was very popular. "This solution has no problems in terms of technical maturity or difficulty of implementation. However, the flaw is the use of Freon refrigerant, which has a large global warming potential, poor environmental protection, and the energy consumption caused by the secondary heat exchange of the refrigerant refrigeration is also large, and these flaws also make the scheme not perfect. Wang Bin said.
Under the guidance of the concept of "green Olympic Games", the determination of the refrigerant of the National Speed Skating Hall lasted 18 months, and after dozens of rounds of technical exchanges and demonstrations, the owners, experts and designers finally chose a different plan from the previous Winter Olympics, adopting a technical route with the best environmental protection and greatly improved energy efficiency, that is, the carbon dioxide transcritical direct cold ice system.
In the selection process, the first step is to select environmentally friendly natural refrigeration working fluids, that is, pure natural refrigerants. In the development of the refrigeration industry in the past 200 years, the selection of refrigerants always faces the contradiction between refrigeration efficiency, safety and environmental protection. Wang Bin introduced that in the current industrial and commercial refrigeration, the most widely used pure natural refrigerant, one is ammonia, the other is carbon dioxide.
Wang Bin said that carbon dioxide in nature is already a large amount of existence, cheap and easy to obtain, and carbon dioxide as a refrigerant its ozone depletion potential value of zero, global warming potential value of 1, to avoid the current widely used high global warming potential of Freon refrigerants brought about by the greenhouse effect. The use of natural working fluid carbon dioxide as the refrigerant of the National Speed Skating Hall has improved the green quality of the Winter Olympic venues and helped achieve the goal of "carbon neutrality".
In the design, in addition to considering the refrigerant to be green and environmentally friendly, it is also necessary to consider the long-term operation of the refrigeration system and the low energy consumption requirements to create a low-carbon energy-saving venue. "Carbon dioxide refrigeration system refrigeration will take away the heat under the ice, to achieve rapid cooling of the ice rink, this part of the waste heat in the conventional system is generally directly discharged into the outdoor environment, if we can use it, it will greatly improve the energy efficiency of the entire refrigeration system." Wang Bin said that the national speed skating hall refrigeration system design team applied the integration technology of cold and heat combined supply to store the high-quality heat energy generated by carbon dioxide refrigeration in the water tank for ice surface maintenance and pouring, domestic hot water of the venue, etc., which greatly reduced the energy consumption of the stadium operation.
In addition to low-carbon environmental protection, engineers should also consider the quality of ice making. The temperature and uniformity of the ice surface will directly affect the quality of the ice surface, and the large temperature difference on the ice surface will cause the ice surface to be soft and hard uneven. The use of carbon dioxide direct cold ice technology can minimize the temperature difference between the Xiaoice surface, ensure uniform ice temperature, and improve the quality of the ice surface.
The National Speed Skating Hall finalizes the carbon dioxide refrigerant and adopts transcritical carbon dioxide direct cooling ice making technology, which is considered to be one of the most environmentally friendly and advanced ice making technologies. The carbon dioxide direct cooling ice making system avoids the secondary heat exchange of the traditional refrigerant ice making system, and its comprehensive energy consumption is reduced by more than 30% compared with the traditional technology, and the venue can save about 2 million kWh of electricity a year.
Due to the high technical requirements and difficult control problems, in the world, in recent years, there have been cases of using carbon dioxide transcritical ice making in relatively small 1800 square meters of standard ice rinks. The application of this technology on the 12,000-square-meter super ice surface, and in the Winter Olympics, there is no precedent in the world. With the unremitting efforts of the ICE and Snow Team of COFCO Engineering, the ice temperature difference of the National Speed Skating Hall was finally controlled within 0.5 degrees Celsius, lower than the 1.5 degrees Celsius required by the Beijing Winter Olympic Organizing Committee, so that the venue has the hardware conditions to become the fastest ice.
"The innovative application of carbon dioxide transcritical direct cold ice making technology in the National Speed Skating Hall is of greater significance to the demonstration effect of promoting the low-carbon development of the ice and snow industry." Wang Bin said that many other Winter Olympic venues have also learned from the experience of the national speed skating hall to adopt carbon dioxide ice making systems. According to statistics, there are a total of 9 ice surfaces in the new construction and reconstruction of the Beijing Competition Area, of which 5 use green and low-carbon carbon dioxide transcritical direct cold ice making technology, practicing the concept of "green Olympic Games".
Innovative research and development of combined cold and heat technology to recover waste heat
Known as the Winter Olympics " Ice F1 " , bobsleigh bobsleigh races glide at a top speed of more than 130 km/h. The National Bobsleigh Center Track in Yanqing is nearly two kilometers long, with a maximum gradient of 18 degrees and a height difference of 121 meters. With 16 corners, the main circuit is the only track in Asia with a 360-degree slalom. The entire main track is composed of 54 track segments of different shapes, with a total ice surface of more than 10,000 square meters.
Bobsleigh track design is the most difficult individual event in the Winter Olympic Games, and the shape and speed curve of the track and the track cooling ice system bring great challenges to the design. The ice surface of the National Bobsleigh Center circuit is white and shiny, and its ice-making principle is to cool the surface of the track through the refrigeration system to cool and heat exchange the water into ice. However, unlike the indoor ice rink, the bobsleigh track has a large height difference, a long distance, and the shape of each section of the track, which tests the cooling stability.
The ICE and Snow Team of COFCO Engineering selected ammonia as the refrigerant of the ice making system of the National Bobsleigh Center from the perspective of green, energy saving and stability. Wang Bin said that ammonia is a natural refrigeration working fluid, with green, efficient and other advantages. Like the National Speed Skating Hall, the National Bobsleigh Center also adopts direct evaporative refrigeration technology to minimize energy losses caused by secondary heat transfers. Since the track is set outdoors, the track refrigeration load is greatly affected by the temperature and humidity of the outdoor environment, considering the energy saving and stability of the system, the refrigeration equipment in the refrigeration system of the bobsleigh center adopts frequency conversion technology to ensure the efficient operation of the refrigeration system under part of the refrigeration load. The refrigeration system also applies a number of energy-saving technologies, such as ammonia heat pump system, plate and shell type high efficiency heat exchange technology, high automation intelligent control system, etc.
In the National Bobsleigh Center Project, the ICE and Snow Team of COFCO Engineering and enterprises within the United Nations innovated the application of cold and heat cogeneration technology, and designed a set of ammonia high-efficiency heat pump unit on the basis of the refrigeration system, which will recover the refrigeration waste heat generated by ice making and improve the energy level for the winter heating of the venue and supplement the thermal energy demand of the venue. This is the first time that the ammonia heat pump system has been used in the Winter Olympic snowmobile ski project, and the combined cooling and heating technology greatly saves the energy required on the heating system side compared to a single electric heating.
Technicians monitor the condition of the track at the National Bobsleigh Center. Courtesy of COFCO Engineering Beijing Division
Considering the refrigeration ice load in the outdoor 20 degrees Celsius environment, each track section is equipped with temperature remote sensing equipment to monitor the concrete temperature of the track in real time, Wang Bin said: "When the outdoor temperature exceeds 25 degrees Celsius in the summer of 2021, we conducted a full-track frost and full-load operation test to ensure the stable operation of this refrigeration ice system. ”
The surface temperature balance of the track is the premise of ensuring high-quality ice making, and during the race, the technical personnel of the COFCO Engineering team will guarantee the refrigeration system around the clock, detect the temperature of the track in real time, and ensure the stable operation of the track.
Snowmaking water sources give priority to natural precipitation
Alpine skiing is known as the "jewel in the crown of the Winter Olympics", located in the Yanqing Division of the National Alpine Ski Center with a maximum altitude of 2198 meters, a total of 7 ski tracks, the longest track length of about 3 kilometers, a vertical drop of about 900 meters, is the highest level of alpine skiing in China, and the only track in China that meets the standards of the Winter Olympics.
Previously, there was no experience in the design and construction of alpine skiing projects for the Winter Olympics in China, and the slopes of the National Alpine Ski Center were large, the drop was large, and the working surface in some areas was extremely narrow and the geological structure was complex, making the construction difficulty quite high. Sun Tianhui, founding member of the ICE and Snow Team of COFCO Engineering and head of the snowmaking system design of the National Alpine Ski Center, said: "Snowmaking needs to fully consider the height difference, temperature, humidity, water and other factors of the site, under the premise of meeting the requirements of the International Snow Federation for the track, the location of the snowmaking machine room, snowmaking equipment and pipeline layout have fully considered the ecological protection factors, and made the greatest efforts to reduce the impact on the ecology." ”
The National Alpine Ski Center has an area of 800,000 square meters, how to create 1.2 million cubic meters of snow with water? Sun Tianhui said that in order to ensure the safety, economy and efficiency of snowmaking, the National Alpine Ski Center adopts the world's most advanced snowmaking system, giving priority to the use of natural precipitation collected and stored, surface runoff and so on as water sources. Snowmaking water mainly comes from the Foyukou Reservoir in Yanqing, and through the underground comprehensive pipe gallery, the snowmaking water is transported to the reservoir in the competition area, and then the water is injected into the snowmaking system by the three-stage pumping station.
The National Alpine Ski Center has also built a perfect snowmelt water and rainwater recycling system, after the snow melts, it collects and conflues through drainage channels, and then flows into the downstream of foyukou Reservoir to achieve water recycling; and sets up windproof fences in local areas to improve the utilization rate of snowmaking water and snowmaking efficiency, and save water resources to the greatest extent.
Complete snowmaking at the National Alpine Ski Center. Courtesy of COFCO Engineering Beijing Division
According to the forecast of the meteorological department this winter, the temperature at the top of Haituo Mountain in Yanqing Racing Area will reach minus 40 degrees Celsius, the highest wind is 12 degrees, and the maximum slope of the slope is 68 degrees, how to achieve quality and quantity snowmaking? Sun Tianhui introduced that the National Alpine Ski Center adopts an intelligent snowmaking system, and 170 snow machines and 30 snow guns are arranged on the wind outlet of the snow slope according to different needs. The intelligent system located in the control center is remotely controlled like a "brain", accurately "controlling" the snowmaking height, direction, etc. of each snow machine to adapt to changes in climatic conditions.
Artificial snowmaking process and natural snowfall principle is similar, snowmaking water supply system provides pressure of about 2MPa of high-pressure water to snowmaking equipment, water through the snow machine nozzle atomization, snow machine core spewed out of the compressed air and atomized water condensation as snow core, when the outside temperature reaches the snow conditions, snow core and sprayed water mist in the air combined, forming snowflakes, relying on the power provided by the snow machine to float on the snow track, snow roller will be soft snow compaction, creating a total area of more than 800,000 square meters of competition snow.
The race pistes are icy snow, similar to the ice surface, you need to pour water on the pistes first, then quickly flatten the track, and then manually and repeatedly trim and shape the pistes until they reach a smooth state, to ensure that the surface of the pistes is smooth and smooth when the athletes turn at high speed, and to ensure that the ski trails are in a relatively perfect state regardless of the first few appearances of the players.
During the Winter Olympic Games, the ice and snow support team will be stationed in the National Speed Skating Hall, the National Bobsleigh Center and other Winter Olympic venues to provide technical support for the adjustment of the ice surface during the competition. Wang Bin said that the COFCO Engineering Support Team will do its best to provide technical support for the Winter Olympics, and expects athletes from all over the world to play the highest level of competition on green, low-carbon, stable and reliable ice and snow.
"Green has become the brightest background color of the Beijing Winter Olympics, painting a beautiful picture of the construction of ecological civilization and sustainable development on the mainland." We believe that the Winter Olympics, like the Summer Olympics, will dedicate a wonderful and unforgettable Olympic event to the world. Wang Bin said.