Table of Content

25 November 2020, Volume 42 Issue 11

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Smart heat-supply roadmap based on digital twin

ZHONG Wei, ZHENG Lijun, YU Zitao, LIN Xiaojie

2020, 42(11):  1-5. 

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With the economic development and the advancement of energy reform in China，the composition of centralized heating source，heating network scale and heat consumption at user's end encounter a major change.Employment of clean sources and consumption of renewable heating sources are the major trends and challenges to the existing operation control method taken by traditional heat-supply systems. A smart heat-supply technology path was proposed based on digital twin and engineering concept to promote the development of intelligent heat-supply system. Compared with the conventional roadmap，the center of the smart heat-supply system is a framework made up of a physical device layer，a sensing and control layer，a transport layer，and an intelligent decision-making layer. The physical device layer including heating sources，network，load and storage equipment，provides physical basis required by smart heating. The sensing and control layer realizes the comprehensive perception on the entire system，providing data required by the intelligent decision-making layer and carrying out the decision sent downwards. The transport layer connects the physical equipment uploading real-time data and the decision-making layer giving orders. The intelligent decision-making layer can realize fault detection and diagnosis，data-based prediction，optimized dispatching and energy efficiency analysis，based on the digital twin model of the system. A case study made on a smart heating site shows that this roadmap could reduce the energy consumption in the entire system with such a framework.


Study and application of intelligent dispatch technology for steam heating networks in industrial parks

YE Qing, SUN Hailong, KONG Fanqi, WANG Yefei, ZHAO Qiong, ZHONG Wei, Li Fengjun, JU Guoteng

2020, 42(11):  6-13. 

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With the promotion of "retreat from city and move into park" policy and the rapid development of steam heating networks for industrial parks，the complexity of heating network dispatch has exceeded operators' response speed and judgment capability based on their experience.Thus，an optimized dispatch technical framework of an intelligent heating network in an industrial park is proposed.Then，a digital twin topology network model mapping to the actual heating network is established，and a simulation calculation method for the steam heating network is advanced as the prediction and analysis basis of the optimized dispatch. Taking the large-scale steam heating network of a printing and dyeing industrial park in Zhejiang Province as research object，the dispatch results after shutting down the heat sources made by empirical method were compared to that made by intelligent dispatch. The results show that the intelligent heating technology realizes the optimized dispatch of the steam heating network accurately. After the optimization，the maximum deviation between the expected temperature and the actual temperature of the heating network is 2.27%，while the maximum deviation between the expected and the actual pressure is 8.57%.The dispatch made by empirical method results in a 0.14 MPa drop of steam pressure at user end on average，while the average steam pressure at user end only reduces by 0.07 MPa by taking optimized dispatch.The results indicate that the optimized dispatch effectively reduce the adverse effect of dispatch scheme on steam consumption and intelligent heating technology is promising in industrial parks.

Application and optimization of intelligent heating in distribute gas heating systems

ZHANG Yinlu, LI Wenjia, KANG Ligai

2020, 42(11):  14-20. 

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Most heat-supply companies in China have completed their transition from manual operation to automated operation. Yet，their operation is incomplete due to the lack of comprehensive and quantitative understanding on heating information and energy saving potential of intelligent heating. In order to reduce operating costs and energy consumprion，a distributed intelligent heating system with smart operating platform as its core and electromechanical and control systems as its foundation has been built. By getting through all links in the data chain of a heating system and taking big data analysis as well as artificial intelligence algorithm，an intelligent heat-supply upgrading project for Zhuoda Shuxiang Garden in Shijiazhuang City was made. The optimization started from the load demand response on heat source side and the thermodynamic equilibrium on pipeline side. After the updating，the indoor temperature levelled off at 20.2℃ ，and the energy consumption reduced by 28%，compared to the previous year. The updating is of great energy-save effect，and can provide technical support for operation renovations of existing and new heating systems.

Research on comprehensive energy-saving technology based on integration of artificial intelligence into thermal systems

HU Xue, YANG Junhong, LIU Dechao, SHI Xinyu, CUI Mianshan

2020, 42(11):  21-33. 

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To eliminate the energy waste caused by hydraulic imbalance and excessive heating in district heating systems，a source-network systematic energy saving technology integrating pipeline classification and intelligent control was proposed and applied in its demonstration project. The technology is based on the integration of artificial intelligence into thermal systems. Technically，the technology coordinates various heat sources（water，electricity and natural gas）as well as the software and hardware.Practically，application of this technology should be made by hierarchy，grades and stages and take various operable decoupling factors into consideration. Applying LSTM deep neural network in the heat load prediction， combining the twin model equivalent to the actual system with the simulation model，the optimal heating scheme for the system is obtained by taking the optimal indoor temperature as the objective function. In the heating season of 2019—2020， the technology being applied in a power station of a university in Tianjin，has realized intelligent and integrated regulation on its 28 thermal inlets ，and achieved remarkable energy-saving effect.Compared to the last heating season，the gas and electricity consumptions in the heating season of 2019—2020 reduced by 25.66% and 22.87%，respectively.Considering the influence of heating time，weather and uncontrolled thermal inlets，the gas could be saved by 31.07%.Proven by the performance of the demonstration project，the comprehensive energy-saving rate is 20%—30% at the initial stage theocratically.The project laid a foundation for the targeted 60%—70% energy saving based on the simulation model and theoretical calculation，by taking precise control upon different time，zone and temperature with a minimal time and space scale.

Discussion on automation，informatization and intellectualization of heating

FANG Xiumu, YANG Dayi, ZHOU Zhigang, LIU Jing

2020, 42(11):  34-38. 

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Most heating enterprises in China have experienced the process from manual operation to automatic operation. However，they are lack of comprehensive understanding on the difference between heating system informatization and intellectualization，and the energy saving potential in intelligent heating. By expounding the automation，informatization and intellectualization of heating，and discussing on the differences between informatization and intellectualization of heating from capacities in load prediction，operation regulation and hydraulic balance，it is pointed out that intelligent heating can maximize the energy efficiency of a heating system. On the basis of informatization，the operating efficiency of the system and the boiler can be increased by 1 to 2 percent points and 12 to 13 percent points，respectively，and the overall efficiency of the stoker fired boiler heating system using second-class bituminous coal can be increased by 10.00 to 12.68 percent points.

Benefit analysis of hydrothermal geothermal central heating systems based on ejector heat exchangers

SUN Fangtian, HAO Baoru, CHEN Xu, ZHANG Shigang

2020, 42(11):  39-43. 

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To deal with the problems of short economic heating radius，small heating scale and low utilization efficiency of hydrothermal geothermal resources existing in the conventional hydrothermal geothermal heating mode， a new hydrothermal geothermal central heating system based on enhanced ejector heat exchangers is proposed according to the characteristics of both hydrothermal geothermal resources and ejector heat exchangers. The results show that the new heating mode is of a lower primary return water temperature，which facilitates mounting the temperature difference between supply and return water，utilizing hydrothermal geothermal heat and recovering waste heat in flue gas. Comparing with the conventional central heating system based on gas-fired boilers，the new hydrothermal geothermal central heating system can increase the energy efficiency of fossil fuel by about 86.0%，boost the product exergy efficiency（PEE）of the system by about 9.7%，reduce the heating cost by about 32.47 yuan/GJ ，and save natural gas consumption by about 70%.The cost- effective distance of the new hydrothermal geothermal central heating system reaches 55.2 km，which could be used to resolve the space distribution mismatching between the hydrothermal geothermal heat fields and the heating load center.

Study on the performance of a solar seasonal heat-storage and heating system

ZUO Chunshuai, FAN Haiying, WANG Enyu

2020, 42(11):  44-50. 

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A solar seasonal heat storage and heating （SSSH） system for an office building in a severe cold area of Zhangjiakou is studied，to promote the application of SSSH system. The start/stop control conditions of heat collection （heat storage），heating performance and ground temperature variation are analyzed by taking experiments and TRNSYS dynamic simulation. The experiment results show that the heat collection efficiency decreases with the increase of the start/ stop temperature difference，and the heat collection efficiency and storage efficiency decrease with the increase of start-up temperature of heat storage. The simulation results show that with the increase of start-up temperature，stop temperature or start /stop temperature difference of heat collection and the heat collection（heat storage）efficiency will decrease，while energy efficiency ratio of heat collection（heat storage）cycle will increase. Every 1 ℃ increase of heat storage starting temperature will lead to a 0.7% decrease and a 0.3% decrease in heat collection and heat storage efficiencies on average. And every 1 ℃ increase of the start/stop temperature difference will reduce the heat collection efficiency by 1.7%，while increase the energy efficiency ratio of heat collection cycle by 2.0%. The COP of the heat pump and the system are 3.4 and 3.1 in heating seasons，respectively. Completing the cycle of heat storage and heating，the ground temperature rises from 6.12 ℃ to 6.91 ℃，which meets the requirements of long-term stable operation of the system.

Technology and application of solar central heating in extremely cold and high-altitude areas

ZHAO Bin, LU Dawei, LIU Weian, WANG Peng, GAO Feng

2020, 42(11):  51-55. 

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Tibet is located in an extremely cold and high-altitude area with abundant solar energy，dry and cold climate， fragile ecological environment，long winter and large day and night temperature difference. Thus，it is urgent to solve the problem of heating in winter. According to the local resources characteristics，climatic conditions，and heating demand of public and civil buildings，a large-scale solar collecting and heat storage system suitable for high-altitude area has been developed through product and technology innovation. This heating system has been verified by large-scale solar central heating demonstration projects in Nagarzê County of Shannan Region and Zhongba County of Shigatse City at an altitude of 4 700 m. Data from the heating seasons show that the demonstration projects are safe and stable in operation，advanced and reliable in technology，and ecnomic in annual operating cost，which satisfies Tibet's demand for heat supply with clean energy. The research results can provide technical support and solutions for the heat supply with clean energy in extremely cold and high-altitude areas，such as Tibet and Qinghai .

Long-distance heat-supply mode with large temperature difference using waste heat of power plants

FU lin, LI Yonghong

2020, 42(11):  56-61. 

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Targeting at the problems of long-distance heat transportation，low heat grade and high recovery cost existing in waste heat utilization of power plants，a large-temperature difference long-distance heat-supply mode characterized by low return water temperature was proposed. The mode has greatly improved the transmission capacity of the heat-supply network and significantly reduced the cost of waste heat recovery. It made the large-scale waste heat utilization of power plants economic and feasible as well. Considering the potential heating area of cities and towns in northern China which will reach 20 billion square meters，a clean heat-supply scheme was made based on the long-distance heating mode utilizing waste heat from power plants. Compared with the reference scheme replacing coal with gas or electricity，this scheme can save 50% energy consumption，reduce 80% air pollution emission，reduce carbon emission by 200 million tons，and save the comprehensive heating cost by 25%. Since the long-distance heat-supply mode is of large investment and complex relationships with multiple parties，waste heat from power plants should be further stated as the dominant heating source for the clean heating in northern cities and towns in China，and corresponding policies and measures should be carried out to encourage the development of this clean and efficient heating mode.

Time- space analysis of the hydraulic conditions for the whole heating network

ZHENG Zhonghai, ZHANG Wen, KANG Hui, ZHAO Siyuan

2020, 42(11):  62-68. 

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With the development of heating systems in scale，complexity and intelligent level，hydraulic calculation considering multiple time-dynamic conditions and the spatial information of the whole network are used in heating network analysis，which plays a key role in scientific decision-making and operation scheduling for heating companies.Based on the analysis and verification on the hydraulic conditions for the whole network in a heating company，a time-space analysis method adapting to the local condition is proposed.Dealing with a muti-condition operation plan including network-cutting condition，multiple heat source networking and distributed variable frequency transmission，an optimized operation plane is carried out according to the topological structure of the current pipelines. It can improve the safety and economy of the hydraulic operation of the whole network.

Analysis on the superiority of nuclear energy district heating systems

LI Xiaobin, ZHANG Hongna, QU Kaiyang, LI Fengchen

2020, 42(11):  69-82. 

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Vigorously promoting green and low-carbon energy is the energy development strategy in China. As an efficient and clean new energy，nuclear energy has great potential in district heating in China，since it can greatly alleviate current environmental pollution problems caused by coal-fired district heating systems. Analyzing the necessity of nuclear energy district heating systems in China，the time is ripe for developing it. From the viewpoints on the inherent safety of representative nuclear heating reactor designs in China，the economic and social value of nuclear energy district heating systems，the possibility of performance improvement for the system integrated with pipeline flow turbulent drag reduction technology，system optimization based on deep learning，heat supply with multiple heat sources，phase change heat storage and big data smart heat supply technology is expounded.The advantages of nuclear energy district heating system are fully elaborated，which provides support for the promotion of nuclear energy district heating technology.

Discussion on the technical route of energy consumption reduction in clean gas-fired heating

GAO Jun, WANG Xun

2020, 42(11):  83-90. 

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Improving the energy efficiency of natural gas in large scale clean heating，is not only significant for energy
conservation and emission reduction，but also of good social and economic benefits. Taking practical cases in Beijing as an
example，the feasibility and adaptability of gas-fired lithium bromide/ammonia-water absorption heat pumps and PAVE
systems are analyzed based on local natural gas price. The results show that gas-fired lithium bromide absorption heat
pumps are economic with an installation capacity at 60% boiler load，but it is not recommended for the gas-fired boiler
plant with a total capacity ≤28 MW. In order to improve the project economy，small and medium-sized gas-fired boiler
plants are recommended to take the joint operation with gas-fired boilers + small gas-fired ammonia-water absorption heat
pumps/PAVE system. In the practical cases，different technical routes should be selected according to the scale of gas-fired
boiler plants，installation capacity of the heat pump，local climate conditions and gas prices，so as to ensure the project
economy. The optimized route for gas-fired ammonia-water absorption heat pump/PAVE system is also pointed out.

The study on application of phase change energy storage technology in clean heating

WANG Changjun, LIU Shuo, DING Xuefeng

2020, 42(11):  91-96. 

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As an energy storage technology，phase change energy storage is mainly used to adjust the imbalance between energy supply and demand in time and space，so as to shave peak load，relieve energy supply pressure and reduce energy consumption cost.There are various application modes of phase change energy storage in clean heating，and phase change energy storage heating is one of them.In the heating project for an office building，phase change energy storage technology effectively saved the architectural space，reduced the operating cost by about 70%，and shaved the peak load by 1 309.2 kW at least.In extreme weather conditions，it can meet the heating needs of users.Integrating phase change energy storage technology with air source heat pumps can effectively improve the average COP and expand the application scenarios of the pump.Applying phase change energy storage technology in buildings can reduce their heat loss and energy consumption by utilizing solar energy.Phase change energy storage technology is promising in the clean heating industry.

Design of a coal to alcohol-based fuel boiler and analysis on its application cases

ZHANG Song, LIU Jing, HUO Da, ZHU Qiang, MA Chenming, ZHAO Jun

2020, 42(11):  97-105. 

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With advantages of high combustion efficiency，low pollution emission and convenience in storage and transportation，alcohol-based fuel，as an excellent substitute for coal，can reduce the emission in heating seasons. A coal- fired boiler took a burner special for "medium pressure atomization" alcohol-based fuel in its technological transformation. The principle of the transformation，operation modes and security measures were analysed，and six competitive clean fuels on the market were comprehensively evaluated. The results show that the annual costs of methanol heating furnaces and air source heat pumps are similar，keeping at a low level among clean heat sources. Methanol heating furnaces are of no SO2 emission and the lowest NOx emission among clean heat sources. Taking the coal-fired boiler reconstruction project of Fangezhuang Mining Branch of Kailuan Group as an example，the emission，energy consumption and economy before and after the reconstruction are analysed. After the reconstruction，the boiler energy efficiency is increased by 35 percentage points. With the same heating area of 413 000 m2，the annual emission of soot，SO2 and NOx after the reconstruction are 5， 35 and 21 t，respectively. With 5 499 t standard coal reduction in coal consumption，annual cost for desulfurization and dust removal could be saved by 1.8 million yuan，while the cost for heating might have a slight rise. If the price of methanol fuel is lower than 1 900 yuan/t，it will be of better economy. The results provide an important technical basis for the design of alcohol-based fuel burners and the transformation for small and medium-sized coal-fired boilers.

A review on the clean heating technology using biomass briquette fuel for rural areas

LIU Liansheng, WANG Dongji, DUAN Runze,

2020, 42(11):  106-116. 

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Clean heating technology can effectively alleviate environmental pollution caused by direct incineration of agricultural and forestry waste in rural areas of northern China，and facilitate the construction of Green Livable Villages and Towns.At present，the annual production of biomass briquette fuel is about 18 Mt in China，while the development of this industry is relatively slow. Biomass briquette fuel has good ignition and combustion characteristics，and its heat mainly comes from volatile matter combustion.Biomass briquette fuel is of short combustion cycle and its ash is liable to coke.The technologies taken in wood pellet fuel stoves being promoted in China originate from EU.The dust and CO emissions of the stove is relatively low，while its NOx emission exceeds the industry standard. Domestic biomass briquette stoves are unqualified technically，but its automatic feeding device can stabelize the combustion and reduce the pollutant emission. The NOx is mainly from combustion of fuel，and the regular low-nitrogen combustion techniques including air staging and flue gas recirculation are unsuitable for small boilers. Base on the endowment of regional biomass resources and heating demand，providing fuel supply services for farmers in form of fuel processing in energy service stations will promote the low- cost and clean heating in rural areas.