Science and Technology Daily reporter Chen Xi intern Lai Yanshu
“In 2022, after the implementation of the waste heat utilization and energy supply project of the data center of Qingshu science and Technology Park in Gaocun, Beijing and Tianjin (hereinafter referred to as Qingshu science and Technology Park), if the waste heat generated by the operation of the data center is collected and provided with winter heating, summer cooling and domestic hot water supply for Qingshu science and technology park through the chilled water heat extraction technology of the cooling system, the energy consumption efficiency of the data center will be greatly improved.” On December 31, 2021, Yang Yanchun, account manager of State Grid (Tianjin) comprehensive energy service Co., Ltd. (hereinafter referred to as Tianjin energy), said that the project is expected to save 633.3 tons of standard coal, reduce 1659 tons of carbon dioxide, 5.4 tons of sulfur dioxide and 4.6 tons of nitrogen dioxide every year, providing a reproducible and popularized comprehensive energy solution for achieving the “double carbon” goal.
In the recently released action plan for carbon peak before 2030, the word “waste heat” appears five times in different chapters. It can be seen that China has paid attention to the great value of waste heat utilization at the strategic level.
Low grade waste heat still has energy and value
Waste heat plays an important role in the energy industry. Waste heat resources generally exist in iron and steel, chemical industry, light industry, food production and other industrial fields. It is the usable heat released in the production process. According to the statistics of foreign research institutions, in the process of utilizing fossil energy, only 40% of the energy is effectively utilized by the industrial sector, and the remaining 60% is finally converted into waste heat.
Waste heat is divided into high-grade, medium grade and low-grade according to grade. Most of the medium and high-grade waste heat is recycled through waste heat power generation projects. Han shenchao, deputy manager of Tianjin energy market operation Department, for example, the high-temperature and high-pressure steam of Bohua Yongli chemical plant needs to be reduced into medium pressure and low-pressure steam by using temperature and pressure reducing valve before it can be further utilized. In this case, add a steam turbine in the middle, use the high-pressure steam to push the steam turbine to do work, convert the pressure into kinetic energy, and drive the generator to generate electricity. At the same time, high-pressure steam is also converted into low-pressure and medium pressure steam, which will continue to be used in the process.
Low grade waste heat, including low concentration combustibles with a calorific value of less than 600 kcal / standard cubic meter, sensible heat objects with a temperature of less than 800 ° C, and low-temperature tail gas and flue gas with a temperature of less than 400 ° C, is regarded as waste heat and is mostly discharged or directly discharged in the form of cooling due to low temperature, low concentration and low energy.
“Although the grade of waste heat is low, it still has energy.” Han shenchao introduced that, for example, low-temperature hot water or cooling water can be reused in industry after being raised to 80 ℃ by heat pump. In addition, low-grade industrial waste heat can be used as an important heat source supplement for urban central heating together with thermal power plants and boiler rooms, which is of great significance to solve the shortage of heating heat sources in northern cities in winter, reduce the energy consumption of central heating in northern China, improve the atmospheric environment in winter, and further improve the energy utilization efficiency of industrial enterprises.
It can be said that the utilization of low-grade waste heat is a means of energy cascade utilization and overall energy efficiency improvement.
With technological progress, making full use of low-carbon energy such as low-grade industrial waste heat to supply low-grade thermal demand has become a necessary path for energy conservation and carbon reduction, and will also become an important breakthrough for China to achieve the goal of carbon peak and carbon neutralization.
The utilization of waste heat needs to be effectively coordinated by all parties
“China’s energy consumption in the industrial field accounts for 60% of the total energy consumption, but the waste heat utilization efficiency in the industrial field is low, and the preliminary statistics are less than 50%.” Xia Jianjun, associate professor of the school of architecture of Tsinghua University, once said at a seminar on the utilization of low-grade industrial waste heat.
At present, coal and natural gas account for more than 90% of the heat supply. Because a large number of low-grade industrial heat energy has not been paid attention to for a long time, it has caused a large waste of energy resources and high carbon and high pollutant emissions, increasing the cost of environmental treatment.
However, with the attention of the whole society to the utilization of waste heat, low-grade waste heat also began to enter people’s vision. Han shenchao said: “the Bohai petrochemical project we did before has the utilization of low-grade waste heat. Originally, the flue gas was directly discharged through the chimney. Later, we used the low-temperature waste heat generator set to extract the heat and convert it into kinetic energy, and then promote the generator to generate electricity for enterprises.”
“A major difficulty in developing waste heat utilization is that many enterprises lack attention to it.” Han shenchao said that some enterprises feel that waste heat extraction saves less energy, which is not very helpful to improve efficiency; Or although the overall amount of waste heat extraction is large, it is very limited for an enterprise, which makes the enterprise pay less attention to this work.
Han shenchao said that the concept of waste heat utilization must be deeply rooted in the hearts of the people to make people realize that waste heat was thrown away in the past. Now if it is used well, it can greatly reduce the consumption of fossil energy and has great economic value.
It is understood that at present, some energy enterprises have begun to try to utilize low-grade waste heat by providing technical support and investment support to enterprises generating waste heat. After generating energy-saving economic benefits, the two sides will share the economic benefits, which can guide enterprises generating waste heat to accept the “energy-saving benefit sharing” model. For example, the data center does not have much heating demand, but it will produce a large amount of cooling water containing waste heat. The extracted heat can heat the surrounding office buildings and other commercial facilities, which makes the waste heat produce economic benefits.
Experts said that generally speaking, the scale of low-grade waste heat utilization in China is still relatively small. At present, the landing projects are basically single enterprise projects, lacking systematic overall planning and planning. Although all parts of the country are actively achieving the goals of carbon peaking and carbon neutralization, and there are no technical obstacles to waste heat utilization, effective coordination of all parties is needed to truly realize extensive waste heat utilization.
Data center becomes a new growth point of waste heat utilization
“The data center is a new growth point of waste heat utilization, and the waste heat utilization in Tianjin is growing rapidly.” Yang Yanchun introduced that at present, there are thirty or forty data centers in Tianjin, and the energy consumption density of the data center is very high. Although the grade of waste heat generated is lower, unlike industrial waste heat, which can reach 80-90 degrees Celsius, and the waste heat of the data center also needs heat pump to improve the temperature, the amount of waste heat generated is very large and stable because the data center server operates continuously 365 days a year, It belongs to relatively high-quality low-grade waste heat.
It is reported that the data center generally adopts central air conditioning for heat dissipation, and the indoor temperature is cooled through cooling water circulation. The water of 15 ° c enters the end fan coil and becomes more than 20 ° C after absorbing the heat of the data center. “Tianjin energy adopts advanced magnetic levitation water source heat pump technology to use these waste heat to heat and supply hot water to the complex, office buildings, shopping malls, restaurants and other facilities next to the data center, and change the hot water supply to 15 degrees Celsius before end medium circulation.” Yang Yanchun said.
Taking the waste heat utilization and energy supply project of the data center of Qingshu science and Technology Park as an example, Tianjin energy has established a waste heat utilization cooperation relationship with the data center. In the later stage, other heat users in the park will extract waste heat from the data center and provide heating services to heat users. According to the plan, the whole Qingshu science and technology park will have nearly 100000 rack servers, which can theoretically meet the heating of 45 million square meters of buildings.
Yang Yanchun’s analysis: “According to the calculation of Qingshu science and Technology Park project, through domestic hot water plus cooling and heating, the data center can reduce the power consumption of 1.6 million kwh a year and save about 1 million yuan of energy cost; Tianjin energy charges Qingshu science and technology park for cooling and heating, which is lower than the price of traditional centralized cooling and heating; the cooling and heating cost from residual heat utilization minus the operating electricity cost, labor cost, etc., Tianjin energy still has Partial difference income. In fact, this model is a win-win situation for the three parties. The data center is energy-saving. The building of Qingshu science and Technology Park reduces the cost of cooling and heating. Tianjin energy can still make a profit. This model is also the first in China. ”
Under the background of “double carbon” goal, Tianjin has explored a new path for urban energy revolution through regional energy solutions, and finally realized the comprehensive and reasonable matching of low-grade waste heat resources. The exploration of low-grade waste heat utilization in Tianjin not only realizes energy conservation and emission reduction, but also is of great significance to improve the environment.
(Science and technology daily)
