Recently, the fifteenth academic week of Tsinghua University's Building Energy Conservation was undertaken by Tsinghua University's Building Energy Conservation Research Center.
How to scientifically plan a clean heating path in northern China? How to integrate adjustment and transformation of urban energy system? During the academic week with the theme of "Low-carbon Energy and Clean Heating in Future Cities", there were several special seminars such as "electric heating development", "urban clean energy planning and technical approach", "thermoelectric and coordinated energy system model" and other seminars. Attract experts and representatives from related fields to discuss.
"Clean heating requires that we further understand electric heating, whether coal is converted to electricity, whether electric heating conversion efficiency is high or not, and whether it is flexible on the grid side or at the end of heating." Academician of the Chinese Academy of Engineering 2. Jiang Yi, a member of the National Energy Expert Advisory Committee and director of the Tsinghua University Building Energy Conservation Research Center, said in an interview with China Electric Power News that electricity is a high-grade energy source. How to make good use of it is an important issue that must be solved to promote clean winter heating in northern regions.
The key is not how much clean energy is consumed, but how much coal is replaced
How to correctly understand electric heating? At the seminar on “Promoting the Healthy Development of Electricity Heating” in Academic Week, Jiang Yi put forward three evaluation criteria.
"One is to look at the efficiency of electrothermal conversion. What we are pursuing is to replace as much fossil energy per unit of electricity as possible, so the key is not how much clean energy is consumed, but how much coal is replaced. The second is to be flexible on the grid side. The ability to adjust depends on whether it can provide space for the further development of renewable energy and respond to changes in the peak and valley of the power grid. The third is to look at the ability to adjust the heating end, and it needs to establish an operating mode that can support 'partial time and part space.'
At the end of 2017, the ten ministries and commissions jointly released the "Clean Heating in Winter in the Northern Region (2017-2021)". For the choice of clean heating methods, the principles of gas should be gas, electricity should be electricity, and coal should be coal. Among them, electric heating must be fully developed in accordance with local conditions in combination with factors such as the heat load characteristics of the heating area, environmental protection and ecological requirements, power resources, and grid support capabilities.
In fact, the initial stage of clean heating in northern China has shown its effectiveness. Electric heating has become one of the means for cities to reduce heating and air pollution. In recent years, natural gas prices and other factors have made the economic cost of electric heating prominent, and have developed rapidly. .
"Using electricity for heating, you should let one electricity generate three heat, or even six heat." Jiang Yi said that in recent years, a new generation of electric power represented by various high-efficiency electric drive heat pumps and electric heat storage heating The rapid development of thermal technology has gradually replaced the conventional heat pump technology and direct electric heating technology such as electric heating film and electric boiler, which are not efficient in actual engineering.
Based on the continuous development and maturity of related technologies, the "2019 China Building Energy Efficiency Development Research Report" publicly released this academic week suggests that except for cold regions where heat and gas networks cannot reach, other conditions are met when buildings meet low energy consumption standards. Regions should promote electric heat pumps on the user side, making full use of low-temperature heat sources such as geothermal, sewage, air, and low-grade industrial waste heat. In addition, it can combine the heat storage to meet the flexibility of grid adjustment, and at the same time use the urban heat network to promote the cogeneration mode on the side of the cogeneration heat source, to solve the problems of insufficient heat supply and power peak regulation.
Combined heat and power and industrial waste heat supply should be the first choice for clean heating in urban China
As with last year, in terms of attitude towards natural gas cogeneration, the "2019 China Building Energy Efficiency Development Research Report" still suggests that it is not appropriate to promote natural gas cogeneration in cities in China. For gas-fired thermal power plants that have been launched, the ability to flexibly adjust the power grid's peak capacity should be enhanced, while deep recovery of flue gas and exhaust steam waste heat.
"On the one hand, natural gas combined heat and power generation consumes a huge amount of gas, while China's natural gas resources are scarce, and gas supply safety and security issues are becoming increasingly serious. The reporter explained that building heating requires room temperature to be around 20 ° C. In principle, any heat source that can release heat at 20 ° C can be used as a heating heat source.
The "2019 China Building Energy Efficiency Development Research Report" states that building heating should be dominated by low-grade energy, while coal-fired boilers, gas boilers, and electric boilers all convert high-grade energy into low-grade heat, causing serious waste, and should be tried as much as possible Not as a building heating source. The data in the report shows that at present, more than half of China's urban heating sources are still boilers of various types, which is not in line with the concept of energy-saving and low-carbon development.
"Regardless of economy, energy utilization efficiency, or environmental emissions, the combined heat and power and industrial waste heat supply methods should be the preferred heating method for clean heating in cities and towns in China." Jiang Yi said that the northern region is currently facing insufficient urban heating heat sources. Problems such as insufficient pipeline network transmission capacity and reduced peak power generation capacity of the thermal power plant during the heating season. At the same time, a large amount of low-temperature waste heat in the power plant is not effectively used for heating. Natural gas heating has high costs and winter gas supply guarantees. Important reasons for energy and environmental problems in cities.
Jiang Yi suggested that comprehensive energy planning from the top-level design and coordination of the three will eventually lead to further adjustment of the urban energy structure. "The urban energy system in the northern region mainly involves electricity, gas and heating. The three Seemingly independent systems are actually interconnected, coupled, and constrained. "(Reporter Zhitong)
(Editor-in-chief: Wang Shaosha, He Yingchun)
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