《1 Engineering research fronts》

1 Engineering research fronts

《1.1 Development trends in the top 13 engineering research fronts》

1.1 Development trends in the top 13 engineering research fronts

The top 13 engineering research fronts assessed by the Field Group of Energy & Mining Engineering are shown in Table 1.1.1. These fronts include the fields of energy and electrical science, technology, and engineering; nuclear science, technology, and engineering; geology resources science, technology, and engineering; mining science, technology, and engineering.

Among these top 13 research fronts, “renewable energy power generation and energy storage: energy-saving and environment-friendly technologies,” “microgrids and smart distribution systems,” “critical technical issues in advanced high-performance fuel cells,” “in situ upgrading mechanism and key technologies for large-scale development of shale oil,” “seepage mechanism and efficient development of unconventional oil and gas,” and “deep space and deep sea nuclear reactors and power supply technology” are emerging ones. “Efficient and clean processing and transformation of coal,” “3D seismic data analysis and reconstruction technology,” and “fully intelligent integrated small modular reactor technology” are further developments of traditional research fields. “New-generation solar cells, including perovskite, perovskite/Si heterojunction tandem, Cu2ZnSnSe4 thin film, polymer, and quantum dot sensitized solar cells” is the subversive front. “Advanced nuclear energy technology: fusion-fission hybrid reactor technology,” “key engineering technologies, equipment, and materials for the intelligentization of coal, oil, and gas exploitation,” and “spatial distribution prediction of residual oil and gas resources based on big data and cognitive theory” are the fronts of interdisciplinary integration. The numbers of core papers published each year from 2012 to 2017 for each of the top 13 engineering research fronts are listed in Table 1.1.2.

(1)  Advanced nuclear energy technology: fusion-fission hybrid reactor technology

The fusion-fission hybrid reactor (referred to as the hybrid reactor) is a nuclear energy technology that combines the advantages of, and overcomes the shortcomings of, fusion and fission. The main difference between a hybrid reactor and a pure fusion reactor is that the cladding contains fissile fuel. The fission fuel has better neutron proliferation ability and energy amplification capability than Be or Pb, which helps reduce the difficulty of fusion engineering. From the perspective of the enthalpy cycle, it is conducive to the achievement of self-sustainability and reduction of the initial amount of investment; from the perspective of energy balance, it can reduce the fusion power and reduce the radiation damage of high-energy neutrons on materials. Compared with a fission reactor, a hybrid reactor is a deep subcritical system driven by a fusion neutron source, which has outstanding safety performance, and can solve the problem of proliferation of fission fuel and metamorphism of transuranic element at the time of energy output. The main research directions of hybrid reactor include driver technology (including tokamak, laser inertial confinement fusion, and Z-pinch inertial confinement fusion), subcritical reactor technology (including pupa, proliferation, transmutation, and energy supply), and high-gain fusion target design technology (for inertial confinement fusion). The development trend of hybrid reactors is based on the recently achieved fusion parameters and draws on mature fission reactor technology to promote the early application of fusion energy and explore ways to solve the sustainable development of fissile energy.

(2)  Renewable energy power generation and energy storage: energy-saving and environment-friendly technologies

As an effective way to solve the problems of energy utilization and environmental pollution in the world, a power generation system based on renewable energy is an inevitable choice and an effective measure for the sustainable development of energy utilization. Focusing on the efficient and clean utilization of renewable energy, technologies for renewable energy generation and energy storage are rapidly developing and attracting increasing attention worldwide.

Based on the current resource status and technological development level of renewable energy sources, the utilization of wind, solar, and hydropower is considered the most realistic and promising method to generate electricity.

《Table 1.1.1》

Table 1.1.1 Top 13 engineering research fronts in energy and mining engineering

《Table 1.1.2》

Table 1.1.2 Annual number of core papers published for each of the top 13 engineering research fronts in energy and mining engineering

Renewable energy generation technologies can be classified into two types: single and hybrid energy generation systems. A single renewable energy system is relatively independent of other power systems and is susceptible to the limitations of the renewable energy source itself. Hybrid renewable energy systems are mainly classified into two categories: the first one is a combination of several renewable energy sources such as wind, solar, and hydropower to complement each other, which can overcome the discontinuous and unstable supply of a single type of renewable source; the second one is a combination of renewable energy with existing fossil fuels in a hybrid power generation system.

Energy storage is a kind of technology that stores electricity when electricity demand is low and discharges it when electricity demand is high to enable better integration of wind power, hydro, solar, and other renewable energy sources with the grid. From the perspective of storage media, there are some energy storage technologies, including mechanical, electrical, electrochemical, thermal, and chemical energy storage.

Current studies are mainly focused on renewable energy materials, components and thermal cycle characteristics of new energy systems, maximum use of renewable energy and minimum use of natural gas in the region, balance between multi-energy supply and demand across a full range, planning of large-scale energy storage facility and coordination with renewable energy systems, and optimization of energy flow based on energy storage and management.

(3)  Key engineering technologies, equipment, and materials for the intelligentization of coal, oil, and gas exploitation

The intelligent extraction of coal, oil, and gas is based on massive data collection, and integrates intelligent environmental perception, intelligent equipment control, self-sustaining operation, intelligent analysis and feedback, etc. Its objective is to achieve unmanned coal mining operation and self-adjustment of oil and gas production. The intelligent extraction of coal, oil, and gas is an integration of environmental perception, intelligent decision, and automatic control. The related five sub-disciplines are engineering perception, digital mine, mine Internet of Things, big data and cloud computing, and equipment automation. The future developments of coal mining intelligentization are: ① Intelligent exploration, which refers to the automatic search and measurement of unknown mining spaces—e.g., coal-rock boundary location, coal gangue detection, and advanced detection; ② Intelligent navigation, which refers to the utilization of computer technology, photoelectric technology, and navigation technology for the automatic positioning of equipment and operator; ③ Intelligent manipulation, which refers to the integration of intelligent equipment and automatic scheduling; it features multiple technologies including longwall shearer memory cutting, hydraulic support automation, coal flow balance of conveying system, hydraulic system generalization, coal mining face visualization, remote control, 3D virtual reality, and one-key start and stop. Intelligentization of oil and gas exploitation involves intelligent well drilling, intelligent well completion, and intelligent production. Intelligent well drilling is essential for well completion and production. The active involvement of multiple technologies such as big data, artificial intelligence, closed loop control, and precise guidance will effectively avoid drilling risk and increase drilling rate. Intelligent well completion requires real-time monitoring and control, which can be achieved through advanced sensing technology, communication technology, equipment automation, big data, and artificial intelligence. Intelligent production is the big-data-based management and optimization of an oil and gas field during its life period. Intelligentization of oil and gas exploitation can be primarily approached through the cooperative work between multiple sub-disciplines, and requires the integration of data, equipment, and operation. The intelligentization of oil and gas field requires considering big data as the foundation. The development plan must be determined using intelligent analysis. The real-time optimization requires intelligent adjustment. Therefore, the integration of intelligent data collection, communication, analysis, and equipment manipulation is necessary and is the direction of future development. Moreover, the deep integration of equipment and material with artificial intelligence can monitor the real-time state of an oil and gas field, thereby enhancing recovery and supporting the data collection, staged fracturing, layered production, and data mining.

(4)  Microgrids and smart distribution systems

Microgrids and smart distribution systems are composed of distributed generation units, energy storage system, energy conversion equipment, monitoring and protection devices, and loads. They are autonomous systems with self-control and energy management. They are flexible in operation and control, and can seamlessly access various AC and DC equipment and can work in multiple modes such as grid- tied and off-grid. Therefore, it greatly improves the power system capability to integrate distributed energy sources, improves system operation efficiency, and ensures continuous and reliable power supply of critical loads. In recent years, comprehensive planning and design, multi-time scale energy management, optimized operation, high-performance hybrid simulation, and new power electronic equipment and control have gradually attracted significant attention. In addition, with the continuous improvement of technologies such as big data, artificial intelligence, and new energy storage, the future microgrids and smart distribution systems will be more open and flexible to achieve integration and interaction with other types of energy systems such as cold, heat, and transportation systems.

(5)  Critical technical issues in advanced high-performance fuel cells

A fuel cell directly converts the chemical energy in fuels and oxidants into electrical energy via an electrochemical reaction, and possesses the advantages of being high- efficiency, and pollution- and noise-free, etc. Very recently, significant improvements have been achieved in hydrogen proton-exchange membrane fuel cell (PEMFC) technologies, thus greatly promoting the global industrialization of fuel cell electric vehicles. So far, the specific power, efficiency, and cold start of automotive fuel cells have already technically satisfied commercialized requirements. However, there remains an urgent need to further improve the service life and greatly lower the cost of fuel cell stacks. Correspondingly, four key research interests should be pursued, including the synthesis of highly active and stable ultra-low/low platinum oxygen reduction reaction electrocatalysts and their mass production; fabrication of high-performance and durable ultra-low/low platinum membrane electrode assemblies and their mass production; development of high-performance anti-corrosion coatings for metallic bipolar plates; improvement of mass transport and water management in the cathodes. When breakthroughs are obtained in the aforementioned aspects, it is expected that the cell performance of PEMFCs will be greatly enhanced, the cost will be significantly reduced, and independent intellectual property rights on these key materials and components will also be attained.

(6)  Efficient and clean processing and conversion of coal

The efficient utilization of coal is based on the needs of the end-user. Clean processed coal can be used as a fuel or a raw material. Efficient utilization of coal includes efficient combustion and efficient conversion. The cleaning of coal is designed to improve the quality of raw coal in order to fulfill the needs of users, so as to provide efficient matching and stable coal products for their efficient utilization. The clean transformation of coal is the use of coal as a raw material. It can be classified into gaseous, liquid, and solid fuels, or into chemical products and carbon materials with special uses.

The main task for the efficient utilization of coal is to improve its consumption structure. At present, scientific research is focused on the in situ conversion of coal, which is beneficial to cleaning secondary energy sources (electricity, fuel gas, and fuel oil). This includes the strengthening of deep processing to obtain chemical raw materials or products (gaseous, liquid, or solid). The main task of clean coal processing is to improve the quality of merchantable coal. The current research focuses on the development of new coal dressing technologies, especially for high-efficiency ash reduction, desulphurization, and dry coal preparation technology, focusing on the washing of steam coal. Coal conversion technology includes all kinds of chemical transformations of coal besides combustion. Scientific research focuses on five coal conversion technologies: coal gasification, coal liquefaction, coal-to- natural gas, coal-to-chemicals, and the pyrolysis of low-rank coal.

Considering the current situation of coal utilization technology and the rising requirements of environment, future coal- efficient processes, with clean processing and transformation, will involve the combination of high-efficiency combustion of coal, power generation technology, coal-fired pollutant control technology, high-efficiency coal-fired generator set and circulating fluidized bed combustion technology, and integrated coal gasification technology, based on coal gasification technology. The development of capture and seal-up technology for the safekeeping of CO2, and oxygen- enriched combustion separation of CO2, will be emphasized.

(7)   In situ upgrading mechanism and key technologies for large-scale development of shale oil

In situ transformation of shale oil is a physical and chemical process of transforming unconverted organic matter and retained hydrocarbon in organic-rich shale into light hydrocarbon by using in situ heating technology, which can be referred to as “underground refinery.” The basic principle of the technology is to heat the shale formation to generate high-quality petroleum and natural gas, which exists in a gaseous state under high-temperature conditions in the underground, thus greatly improving the fluidity. The shale will produce micro-fractures and high pressure during the in situ transformation process, and form an artificial seepage system to increase the seepage capacity. The high- quality petroleum produced via the in situ transformation of shale oil can reach the aviation kerosene level after simple processing, which significantly saves the cost of crude- oil refining, and the residues are stored underground, which can reduce environmental pollution, eliminate hydrofracture, save water resources, and reduce carbon dioxide emissions by comprehensively utilizing new energy sources such as wind and solar energy. At present, the technology is potentially feasible for industrial application, but it has not yet reached the industrialization level. Therefore, we should increase the support and investment for the technology, and develop in situ transformation technology suitable for continental organic-rich shale oil in China. Promoting the industrialization process of this technology is crucial for significantly reducing the external dependence of national crude oil and guaranteeing energy security.

(8)  3D seismic data analysis and reconstruction technology

In seismic data acquisition, owing to the influence of actual environment (such as mountains, rivers, and buildings) and financial constraints, the collected original data are often irregular, and consequently, the effect of subsequent processing (such as offset, multiple wave suppression, and seismic imaging) is not ideal. As an important step in seismic data processing, 3D seismic data analysis and reconstruction can effectively solve this problem. The main research direction of this technology is how to improve the regularity of field-derived data to enhance noise immunity and imaging accuracy. At present, the main research trends focus on the seismic channel interpolation method of F-K domain for sparse seismic data and the unsteady seismic data reconstruction method for irregular missing data, including data reconstructions based on predictive filtering, mathematical transformation, and wave equations. The current development trend is to apply these core technologies to the detection of weak microseismic signals, improvement of the signal-to-noise ratio, oil and gas detection, high- precision hydraulic fracturing monitoring, and full-waveform inversion of logging constraints.

(9)   Spatial distribution prediction of residual oil and gas resources based on big data and cognitive theory

Technologies for predicting remaining hydrocarbon resources aim to satisfy the following two characteristics. First, the distribution of the remaining conventional hydrocarbon resources is disperse and subtle. Second, the distribution of unconventional hydrocarbon resources is heterogeneous. They are important supplements and extensions of traditional resource assessment methods. The traditional studies on the distribution of remaining resources have been conducted from the perspective of resource management, i.e., the systematic management of hydrocarbon resource-play-target. The new technologies for predicting remaining hydrocarbon resources can realize the space localization of remaining resources and visualization of exploration risks. Big data and cognitive theory offer conditions for these technologies. Big data refer to the collection of data that cannot be captured, managed, and processed with conventional software and tools within a certain period of time. They are massive, high-growing, and diversified information assets, which require new processing modes to achieve stronger decision-making power, insight ability, and process optimization. Cognitive theory is related to the internal processing of organism learning, such as the acquisition and memory of information, knowledge, and experience, the realization of insight, the interrelation of concepts and terms, and the various psychological theories of resolving problems. With the deepening of hydrocarbon exploration and development, petroleum industry accumulates data related to mass hydrocarbon production, such as statistical data of exploration and development, geophysical data of earthquakes and well-logging, wireline-log and well-testing data, and lab data related to geology research. Based on the quantitative evaluation of hydrocarbon resources through traditional methods such as genetic method, statistical method, and analogy method, the development trends of future technologies for the prediction of hydrocarbon resources include the prediction of distribution of hydrocarbon resources, clarification of resource distribution law, and determination of favorable hydrocarbon accumulation zones or specific locations. All these actions should be undertaken according to cognitive theory during the exploration geological processing and development geological processing of big data.

(10)    Seepage mechanism and efficient development of unconventional oil and gas

The seepage mechanism of unconventional oil and gas mainly involves the flow characteristics of oil and gas in nanoscale pores and micro cracks. It can be used to analyze the production dynamics in the reservoir and provide important support for the accurate description and evaluation of the unconventional oil and gas reservoirs. However, the geological characteristics of unconventional oil and gas reservoirs are complex, and the development of nanoscale pore oil and gas is difficult. There is an urgent need to improve the development efficiency of unconventional oil and gas, and realize major breakthroughs in the field of unconventional oil and gas. This mainly involves the research direction of reservoir reconstruction, production control, and automation exploitation.

China’s shale gas, shale oil, tight gas, tight oil, coal-bed methane, heavy oil, and other unconventional oil and gas resources are abundant, which are important strategic replacement resources. However, as the reservoirs are complex and the related theory and technology are not mature, it is difficult to realize economic and effective exploitation through conventional means. There is an urgent need to study the seepage mechanism and provide a scientific basis for the regulation and real-time optimization of the unconventional oil and gas production. Therefore, regarding the microscopic percolation characteristics of unconventional oil and gas, the attention degree of non-Darcy percolation, multiphase seepage, and multi-scale percolation will be hot topics in the future. Furthermore, the research on high- efficiency technology, such as waterless fracturing, multilevel fracturing, synchronous fracturing, partial fracturing and combined exploitation, “multi-layer and multi well type” mixed well network mining, and “factory” exploitation, has become the future development trend. It can significantly reduce the cost of mining and improve the recovery of oil and gas.

(11)    Fully intelligent integrated small modular reactor technology

Since the International Atomic Energy Agency (IAEA) announced in June 2004 that it has launched an innovative small- and medium-sized reactor (SMR) development program featuring integrated technology and modular technology, the total number of participating member states has reached 30. More than 45 innovative SMR concepts have become hotspots in international research and development. Small nuclear reactors generally refer to reactors with a single stack of thermal power below 1000 MW (300 MW), with carbon-free emissions, small capacity, flexible site selection, low construction investment, short construction period, and system equipment that can be assembled at the factory. It is easy to transport and can be upgraded and economically improved through modular design. From the perspective of the modular small-stack technical solutions that have been proposed at home and abroad, there are various types of reactors such as pressurized water reactors (PWRs), high-temperature gas-cooled heat reactors, high- temperature gas-cooled fast reactors, lead-bismuth-cooled fast reactors, and molten salt reactors. The modular small reactor that can be deployed in the short-term, without exception, follows the integrated PWR route, and its design and development progress far exceeds those of other reactor types, which is mainly due to the good PWR technology and industrial foundation built over several decades. Research and development features of international main small-sized reactor models are that based on the recently promoted integrated PWR model, design measures to eliminate large loss-of-coolant accidents or projectile accidents are adopted, and design optimization is adopted to improve economy; marine modularity or circuit type of PWR adopts inherent safety features and passive safety system, draws on the experience of nuclear icebreakers and submarines, and adopts standardized design, and batch production and loading to enhance market competitiveness. The small-sized reactor belongs to military and civilian dual-use technology, which can be used as military power, applied to ship power and border defense construction, and can also be used in national economic construction fields (such as residential power supply, icebreaker, urban heating, industrial process heating, and seawater desalination). It has broad application prospects in the military and civilian fields.

(12)   Deep space and deep sea nuclear reactors and power supply technology

Deep space and deep sea contain rich strategic resources.

They are new and valuable territories for the sustainable development of human beings in the 21st century. Their strategic position in national development and international competition is becoming increasingly prominent. Along with the continuous improvement of various deep-space and deep-sea technological capabilities, the issue of energy and power has gradually become a bottleneck for the further improvement of the performance of various deep-sea equipment, and must be rectified. Compared with conventional energy sources, nuclear reactor power sources have the natural advantages of high energy density, no air requirement, and long running time. They can fundamentally solve the shortcomings of deep-sea equipment and become the best choice for future deep- sea energy. The main technologies include: ① Heat-pipe- cooled reactor technology: In contrast to the traditional loop cooling reactor, the heat of this reactor is removed through the heat pipe, which has the advantages of being simple, safe, and reliable, and avoiding single point failure. It is very suitable as the preferred stack type for the power supply unit of a deep-sea small nuclear reactor; ② Free piston Stirling generator technology: regenerative thermal power generation technology, through the linear motor to output electrical energy. It has many advantages such as long life, high reliability, high conversion efficiency, no pollution, and low noise. It is widely used in space power, solar thermal power generation, small-scale cogeneration, portable power supply, biomass power generation system, etc.; ③ Reactor fully autonomous operation technology: the fully autonomous operation of a reactor indicates that it relies on its own physical thermal feedback and instrument control system to adjust and realize automatic operation. It does not require personnel to monitor and intervene online, and can automatically respond to fluctuations in working conditions. It has the advantage of long-term stable maintenance-free operation; ④ Reactor safety technology: special research on the safety technology of deep-sea nuclear reactors, focusing on the safety features, accident mechanisms, and threats of nuclear proliferation that are unique to deep-sea nuclear reactors.

(13)    New-generation solar cells, including perovskite, perovskite/Si heterojunction tandem, Cu2ZnSnSe4 thin film, polymer, and quantum dot sensitized solar cells

Perovskite materials are a class of compounds that have a special molecular structure (ABX3) and originate from calcium titanium oxide mineral (CaTiO3). Perovskite materials have the advantages of high absorption coefficient, sharp absorption edge, and large adjustable bandgap, and hence, the efficiency of perovskite solar cells has been enhanced from 3.8% to 22.7% in only seven years. At present, scientific research in this regard mainly focuses on efficiency, stability, and large- scale industrialization. Among the research topics, inorganic substitution of organic and tin elements to replace lead elements is the most effective method to solve the stability and toxicity problems of perovskites, and has gradually become a new research trend. Furthermore, the unique crystal structure and photoelectric properties of perovskite materials are very suitable for monolithic solar cells. Perovskite/silicon monolithic solar cell technology utilizes different bandgap materials to absorb photons of different energies, thus fully utilizing sunlight, and is expected to become an emerging technology that breaks the efficiency limit of silicon solar cells. The current research and development of this technology focuses on optimizing material preparation processes and reducing parasitic absorption and reflection losses. In only three years, the efficiency of perovskite/silicon monolithic solar cells has increased from 13.7% to 25.2%, which is close to the highest efficiency of silicon cells. Perovskite/silicon monolithic solar cell technology will become a research hotspot in both academia and industry.

Cu2ZnSnSe4 thin film, polymer, and quantum dot sensitized solar cells are other types of novel solar cells studied in recent years. Compared with the CuInGaSe thin film, Cu2ZnSnSe4 has an energy gap closer to the ideal bandgap for solar cells. Moreover, it has abundant sources, is non-toxic and inexpensive, and is expected to achieve higher conversion efficiency. The main focus of related research is to raise its efficiency by improving the fabrication method and application of doping. The representative advances include achieving efficiency of 12.3% using metal precursors and 8.7% using a co-evaporation method (reached 10.4% subsequently, certified). The polymer solar cell is a type of solar cell based on organic semiconductors. It can be easily fabricated as large-area flexible solar cells via a spray method. So far, it could achieve efficiency higher than 13% (single junction) and close to 15% (tandem cell). The typical functional layers are a polymer electron donor layer and a fullerene electron acceptor layer. The recent research hotspots include the development of non-fullerene acceptor-based solar cells, optimization of the electron donor via chemical treatment (for instance, chlorization), and fabrication of tandem solar cells by combining different electron donor layers so as to increase the full spectrum absorption. A quantum dot sensitized solar cell is a type of photo-electrochemical solar cell not based on junction structures such as p-n junction and heterojunction. It uses semiconductor quantum dots (can be compound semiconductors such as PbS and CdSe or single semiconductors such as Si) adsorbed on photo-anodes (normally nanostructured oxide semiconductors such as porous TiO2 and nanowire arrays of ZnO) as a light absorber and realizes electron–hole separation through carrier exchange between them and the oxidation/reduction ion pair in the solid or liquid electrolyte in contact with them. Bandgap modulation can be easily realized through the content and size control of the quantum dot to create spectrum-matched solar cells. Furthermore, it does not require good interfacial condition and very high purity of precursors, which are important to achieve high efficiency with low cost. Recently, a record efficiency of 4.72% has been achieved in the PbS/TiO2 system doped with Hg, whereas an efficiency of 8.0% has been realized in the In2S3+CuInS2/TiO2 system.

《1.2 Interpretations for three key engineering research fronts》

1.2 Interpretations for three key engineering research fronts

1.2.1 Advanced nuclear energy technology: fusion-fission hybrid reactor technology

(1)  Conceptual explanation and key technologies

The fusion-fission hybrid reactor (referred to as the hybrid reactor) is a nuclear energy technology that combines the advantages of, and overcomes the shortcomings of, fusion and fission. The main difference between a hybrid reactor and a pure fusion reactor is that the cladding contains fissile fuel. The fission fuel has better neutron proliferation ability and energy amplification capability than Be or Pb, which helps reduce the difficulty of fusion engineering. From the perspective of the enthalpy cycle, it is conducive to the achievement of self-sustainability and reduction of the initial amount of investment; from the perspective of energy balance, it can reduce the fusion power and reduce the radiation damage of high-energy neutrons on materials.

Compared with a fission reactor, a hybrid reactor is a deep subcritical system driven by a fusion neutron source, which has outstanding safety performance, and can solve the problem of proliferation of fission fuel and metamorphism of transuranic element at the time of energy output. The main research directions of hybrid reactor include driver technology (including tokamak, laser inertial confinement fusion, and Z-pinch inertial confinement fusion), subcritical reactor technology (including pupa, proliferation, transmutation, and energy supply), and high-gain fusion target design technology (for inertial confinement fusion). The development trend of hybrid reactors is based on the recently achieved fusion parameters and draws on mature fission reactor technology to promote the early application of fusion energy and explore ways to solve the sustainable development of fissile energy.

(2)  Development status and future development trend

The research on hybrid reactors involves two major nuclear energy fields: fusion and fission. Based on the recently realized fusion technology and mature fission technology, the application of fusion energy and the sustainable development of fission energy are promoted.

The fusion field is divided into magnetic confinement fusion and inertial confinement fusion. In terms of magnetic confinement fusion, Tokamak research is in a leading position. China officially participated in the construction and research of the international thermonuclear experimental reactor (ITER) project; simultaneously, as a bridge between the ITER device and the fusion demonstration reactor (DEMO), China is independently designing and developing the China Fusion Engineering Experimental Reactor (CFETR) project. In terms of inertial confinement fusion, Z-pinch has more potential as an energy source and is likely to develop into a competitive fusion-fission hybrid energy (Z-FFR) scheme. The Z-FFR consists of a Z-pinch drive, energy target, and sub- critical energy cladding. The following focuses on the key technologies to be addressed by Z-FFR.

Z- pinch inertial confinement fusion covers multiple physical processes and complex physical effects such as magnetohydrodynamics, radiation transport, atomic physics, plasma microscopic instability, and transport mechanisms under strong pulsed magnetic fields. China has focused on the research of Z-pinch plasma implosion kinetics and its radiation source physics, and has obtained a wealth of research results. The research on the overall conceptual design of Z-FFR has made significant progress. However, there are few studies on key issues such as the relationship between current front and Z-pinch load parameters and implosion dynamics, Z-pinch plasma source calibration law and Z-pinch dynamic black cavity radiation field (temperature) calibration law, and Z-pinch inertia, and the energy conversion efficiency of several important physical processes in the process of constrained fusion.

The super-pulsed magnetic field is the most prominent feature of the Z-pinch process. Under this condition, plasma formation and magnetic Rayleigh–Taylor instability development have a decisive influence on the implosion process and implosion quality. Owing to the strong nonlinearity, the energy exchange between the electromagnetic energy of the load zone, the internal energy of the Z-pinch plasma, and the radiant energy is very complicated. The Spitzer resistivity does not accurately describe the characteristics of Z-pinch plasma resistivity, and its anomalous mechanism is unclear. The description and explanation of the generation process and physical mechanism of the radiation source are extremely important. A high-current device can provide a wider range of parameters for conducting Z-pinch plasma physics experiments.

The typical Z-pinch process has a cylindrical implosion feature, whereas the fusion target is a spherical implosion, and a suitable black cavity configuration is designed to effectively separate the loaded plasma Z-pinch process from the target implosion in time and space. This is the core issue of Z-pinch drive inertial confinement fusion. It is not feasible to carry out this experimental study on the existing devices in China. Compared with laser fusion, Z-pinch radiation source has a long time scale and large spatial scale, which makes it difficult to finely adjust the waveform. A new fusion target design is required to effectively compress the fuel and obtain higher energy gain.

The construction of a new-generation high-current pulse power experimental platform is beneficial to the experimental research and verification of the key physical problems of Z-pinch radiation source, black cavity, and target implosion, and other Z-pinch drive inertial confinement fusion processes. It is recommended to have national-level support for the construction of a Z-pinch drive with a peak current of 50–70 MA in 2018–2025 to achieve fusion ignition as soon as possible. Once the ignition target is achieved, the subsequent step is to start building Z-FFR. Z-FFR is equipped with a large ultra-high-power repetitive frequency driver, the preferred fast pulse linear transformer driver, with capacitor nominal energy storage ≤ 100 MJ, peak current 60–70 MA, rising edge 150–300 ns, and operating frequency 0.1 Hz; adopts the concept of “local overall ignition,” and designs high- gain fusion target pellets with energy gain Q ≥ 100; and designs natural uranium fission cladding to achieve self- sustaining energy amplification of 10–20 times and fission fuel proliferation.

(3)    Analysis of comparisons and cooperation between countries/regions and institutions

According to Table 1.2.1, the countries with the largest number of core papers in this research direction are the USA, Germany, the UK, France, Japan, Italy, and China. Among them, the USA holds the first place, with more than 50% of core papers, and the proportion of core papers from Germany, the UK, France, Japan, Italy, and China exceeds 10%.

As evident from Table 1.2.2, the most core papers in this research direction are from Lawrence Livermore National Laboratory, University of Rochester, Los Alamos National Laboratory, Massachusetts Institute of Technology (MIT), General Atomics, Istituto Nazionale di Fisica Nucleare, Sandia National Laboratories, University of Oxford, and Chinese Academy of Sciences, with at least 20 papers each.

According to Figure 1.2.1, the USA, Japan, Germany, the UK, France, and China are more concerned about the cooperation between countries or regions in this field. China has published numerous papers, mainly in cooperation with USA, Japan, Germany, France, the UK, and Russia.

According to Figure 1.2.2, there is cooperation among Lawrence Livermore National Laboratory, MIT, General Atomics, Los Alamos National Laboratory, and University of Rochester.

In Table 1.2.3, the percentage of citing papers from the USA has reached 29.75%; the percentage of citing papers from China has reached 16.81%; and the percentage of citing paper from Germany exceeds 10%.

In Table 1.2.4, the institution that accounts for the highest output of core papers is Chinese Academy of Sciences, with nearly 20%. Lawrence Livermore National Laboratory accounts for more than 16% of the core papers.

According to the analysis of the above data, the core paper output and the number of quotations regarding fusion-fission hybrid reactors in the USA and China are among the highest in the world, and the number of core papers cited by Chinese institutions is large.

1.2.2 Renewable energy power generation and energy storage: energy-saving and environment-friendly technologies

(1)  Concept description

As an effective way to solve the problems of energy utilization and environmental pollution in the world, an energy system based on renewable energy is an inevitable choice and an effective measure for the sustainable development of energy utilization. Focusing on the efficient and clean utilization of renewable energy, technologies for renewable energy generation and energy storage are rapidly developing and attracting increasing attention worldwide.

• Renewable energy generation system

Based on the current resource status and technological development level of renewable energy sources, the utilization of wind, solar, and hydropower is considered the most realistic and promising method to generate electricity.

《Table 1.2.1》

Table 1.2.1 Countries or regions with the greatest output of core papers on the “advanced nuclear energy technology: fusion-fission hybrid reactor technology”

《Table 1.2.2》

Table 1.2.2 Institutions with the greatest output of core papers on the “advanced nuclear energy technology: fusion-fission hybrid reactor technology”

Figure 1.2.1 Collaboration network among major countries or regions in the engineering research front of “advanced nuclear energy technology: fusion-fission hybrid reactor technology”

Figure 1.2.2 Collaboration network among major institutions  in the engineering research front of “advanced nuclear energy technology: fusion-fission hybrid reactor technology”

《Table 1.2.3》

Table 1.2.3 Countries or regions with the greatest output of citing papers on the “advanced nuclear energy technology: fusion-fission hybrid reactor technology”

《Table 1.2.4》

Table 1.2.4 Institutions with the greatest output of citing papers on the “advanced nuclear energy technology: fusion-fission hybrid reactor technology”

Renewable energy generation technologies can be classified into two types: single and hybrid energy generation systems. A single energy generation system is relatively independent of other power systems and is susceptible to the limitations of the renewable energy source itself. Hybrid renewable energy power generation systems are mainly classified into two categories: the first one is a combination of several renewable energy sources such as wind, solar, and hydropower to complement each other, which can overcome the discontinuous and unstable supply of a single type of renewable source; the second one is a combination of renewable energy with existing fossil fuels (natural gas, biogas, biomass, geothermal, etc.) in a hybrid power generation system.

Guaranteeing a continuous, stable, and qualified power output is the key aspect of renewable energy generation. Current studies are focused on dynamic modeling and thermal cycle characteristics of energy system, maximum use of renewable energy and minimum use of natural gas in the region, balance between multi-energy supply and demand across a full range, and controlling system of energy storage and management.

The future development direction of renewable energy is a multi-energy complementary system composed of wind, solar, hydro, heat, and storage through a distributed renewable energy system and intelligent microgrid. Terminal integrated systems designed for multiple user-side needs such as electricity, heat, cold, and gas will be rapidly developed in China. Hybrid renewable energy power generation systems have been used in developed countries such as the United States and Europe.

• Advanced energy storage technology

An energy storage system operates by storing electricity when electricity demand is low and discharging when electricity demand is high to enable better integration of wind power, hydro, solar, and other renewable energy sources with the grid. The general concept of energy storage technology can be defined as a one-way or bi-direction storage between electricity and other types of energy such as heat, chemical, and mechanical energy.

From the perspective of storage media, energy storage technology includes mechanical, electrical, electrochemical, thermal, and chemical energy storage. Pump water storage, compressed air, and flywheel belong to the category of mechanical energy storage. Electric energy storage mainly includes supercapacitor and superconducting energy storage. Electrochemical energy storage mainly refers to batteries, such as lead-acid battery, lithium-ion battery, sodium sulfur battery, and liquid flow battery. Thermal energy could be stored through special media (such as phase change material) in a heat insulation container. The thermal energy can be converted into electricity when required or directly used. Chemical energy storage technology refers to the second utilization of hydrogen or natural gas from the electrolysis of water.

Pumped water storage is currently the most installed energy storage technology in the world, accounting for 98% of the total energy storage capacity. Moreover, compressed air energy storage, lead-acid, and lithium batteries have been developed rapidly in recent years, and have been the most competitive energy storage technologies in the world.

The key technologies of energy storage include planning of large-capacity energy storage and coordination with renewable energy systems, energy system optimization and management based on energy storage, and integrated design and coordination of energy storage and conversion devices.

(2)  Development status and future development trend

•   Renewable energy generation technologies

According to “Renewable 2018 Global Status Report,” published by Renewable Energy Policy Network for the 21st Century (REN21), renewable energy generation accounted for 70% of the net increase in global power generation in 2017, which is the largest increase in renewable energy generation in modern history.

At present, the increase in the global investment in renewable energy has exceeded two times the total investment in both fossil fuels and nuclear power generation. Owing to the increase in cost competitiveness, the proportion of renewable energy investment in the power industry in 2017 is more than 2/3, and the percentage of renewable energy in the power industry will continue to rise.

According to the statistics provided by the National Energy Administration, in 2017, the renewable energy power generation capacity of China was 1.7 trillion kWh, with a year-on-year increase of 150 billion kWh; renewable energy has accounted for 26.4% of the total power generation, with a year-on-year increase of 0.7%. Among various renewable power sources, hydropower generation capacity was 1,194.5 billion kWh, with a year-on-year increase of 7%; wind power generation capacity was 305.7 billion kWh, with a year-on-year increase of 26.3%; photovoltaic power generation was 118.20 billion kWh, with a year-on-year increase of 78.6%; biomass power generation was 79.4 billion kWh, with a year-on-year increase of 22.7%. The annual abandonment of hydropower was 51.5 billion kWh. As the amount of incoming water was greater than that in the last year, the water utilization rate reached 96%; the amount of abandoned wind power was 41.9 billion kWh, and the abandoned wind rate was 12%, with a year- on-year decrease of 5.2%; the abandoned solar power was 7.3 billion kWh, and the abandoned rate was 6%, which is 4.3% lower than that in 2016. Thus, the proportion of renewable energy power generation in China has steadily increased.

At present, the research on renewable energy technologies mainly includes the following three aspects: advanced power generation technology, grid connection technology, and multi-energy complementary system of renewable energy.

For the advanced power generation technology of renewable energy, as the most important output characteristic of photovoltaic power generation is randomicity, tracking the maximum active output power point of photovoltaic power generation is one of the research priorities. As the maximum power point tracking requires high accuracy, rapidity, and stability, effective adjustment of active output is the key aspect of photovoltaic power generation. Wind power generation technologies are mainly classified into two categories: the first employs constant speed and constant frequency, mainly adopting active stall regulation or capable generator equipment; the second employs variable speed and constant frequency, mainly equipped with an asynchronous induction generator. Of the two categories, variable-speed and constant-frequency power generation can capture and utilize wind energy to the utmost extent, and the speed running range is relatively loose with the adjustment system more flexible.

In terms of grid connection technologies for renewable energy generation, renewable resources are affected by ambient temperature and weather factors, which result in relatively large fluctuations and intermittence. This characteristic could easily cause flashover or fluctuations in the grid voltage. Therefore, grid connection and consumption of renewable energy are key aspects for access to existing energy systems. ① Advanced inverter technology: Considering photovoltaic energy as an example, power grids and photovoltaic power plants are mainly connected by inverters. Therefore, inverters are required to be capable of expandable communication functions, controlling reactive power and active power, reducing active power rate, and achieving harmonic compensation. The inverters should guarantee the stability of power output quality and anti-interference ability. Moreover, the interaction between grid and energy sources should satisfy the requirements of the smart grid. ② Accurate and fast grid voltage signal locking technology is required for grid connection of renewable energy, which could accurately lock the phase of voltage under high-power asymmetric operation and voltage sampling fluctuations of grid. ③ System anti- interference technology: The island detection technology requires reliable anti-interference ability from the renewable energy system. Moreover, the low-voltage ride-through (LVRT) performance has become a necessary index for ensuring the safe and stable operation of a power system under the condition of large-scale new energy access. For a centralized wind power and photovoltaic station, LVRT is realized based on inverter control, and the command of island detection can be realized by using the energy from the transmission and transformation of electricity system. For a distributed wind power and photovoltaic station, island detection should be achieved through the control system, and signal command is given based on the energy management platform of the power distribution system.

As for a multi-energy complementary system of renewable energy, compared with traditional power grids, this kind of hybrid system typically has system complexity and uncertainty. ① Planning of system integration, including deterministic and uncertainty analysis: The deterministic analysis indicates that the wind, light, and other resource conditions and load requirements are derived from historical record data. Uncertainty analysis mainly refers to modeling of renewable energy and load variations based on probability statistics, considering several factors such as natural conditions and cold and heat loads of users. ② Comprehensive system modeling: Notably, the time scales and dynamic characteristics of the subsystems in the renewable energy complementary system are different. For example, grid power should be instantaneously balanced, and its dynamic characteristics should be described using differential-algebraic equations. Cold and heat conversion processes are the slowest and are usually expressed in dynamic processes by minute and hour. ③ Optimizations of system design: At present, the calculating methods used by researchers include power flow calculation based on Newton–Raphson method, lowest cost optimization of life cycle analysis, and multi-objective chaotic quantum genetic algorithm. To achieve the optimal use of energy and long-term economic operation, a renewable energy complementary system requires scientific system integration and energy management.

• Advanced energy storage technology

By the end of 2017, the cumulative installed capacity of energy storage projects in the world reached 175.4 GW, a year-on-year increase of 4%. The cumulative installed capacity of pumped water storage still accounted for the largest proportion, i.e., 96%, but with a decrease of 1 percentage point from the previous year. The cumulative installed capacity of electrochemical energy storage was the second largest, with a scale of 2926.6 MW, an increase of 45% from the previous year. The proportion of electrochemical energy storage was 1.7%, an increase of 0.5 percentage points over the previous year. Among the various types of electrochemical energy storage technologies, the cumulative installed capacity of lithium-ion batteries had the largest proportion, accounting for more than 75%.

In 2017, the installed capacity of newly added chemical storage projects in the world was 914.1 MW, a year-on- year increase of 23%. The planned installed capacity of the electrochemical energy storage project under construction is 3063.7 MW. It is expected that the global installed capacity of electrochemical energy storage will experience rapid growth in the short term.

By the end of 2017, the cumulative installed capacity of the energy storage projects of China has reached 28.9 GW, a year-on-year increase of 19%. In 2017, the total capacity of newly invested energy storage projects in China was 121 MW, involving three areas: centralized renewable energy grid connection, auxiliary services, and user-side projects. In the field of centralized renewable energy integration in 2017, the projects undertaken include Qinghai DC photovoltaic and energy storage demonstration project and Jilin wind thermoelectric hybrid energy storage project. The commercialization of solar energy storage is accelerated, and the application of combined electricity and heat storage has become a new research direction to reduce the electricity peaking of power systems and increase the consumption of renewable energy.

Although there are many different types of energy storage technologies, only pumped storage is relatively widely used in large-scale energy storage devices. However, owing to geographical constraints, the usage of pumped storage is very limited. Moreover, other energy storage methods are still in experimental or initial research stages, and the reliability, service life, manufacturing cost, and application capability of these energy storage devices must be improved. In general, the research on energy storage technology in China is still in its initial period and it is not suitable for comprehensive application to the power grid. Moreover, there are still several problems such as incomplete research institutions, uncertain economic benefits, and the lack of operational data support. At present, the key technical fields of energy storage technology research are mainly distributed in the following aspects.

The planning of energy storage systems includes the following fields: ① The wide-area layout of energy storage systems and cogeneration method for conventional power supply and renewable energy; the integration of an energy storage device of hundreds of megawatts in the power transmission and distribution processes of the new energy generation system; ② Research on the selection and configuration method of energy storage in new technology and power supply business mode; the convergence effect, operation mode, and controlling strategy of a distributed energy storage system in the power grid; ③ The policy requirements to realize market application of energy storage technology, including electricity price, market access institution, and electricity market mechanism, which could promote energy storage development; the coordinated operation mechanism of energy storage and other energy resources under various types of electricity market transactions.

As for the technologies of energy storage devices, current research mainly includes: ① The key material modification, low-cost preparation, energy density improvement, and industrialization technology of lithium ion, lead carbon, liquid flow, and other types of energy storage batteries under the current power system; high-security battery materials based on ionic liquid and solid electrolyte; low-cost and high-reliability membrane production technology of liquid flow battery; ② Development of supercapacitor, including porous graphene electrode and high-pressure electrolyte salt, electrolyte, and cellulose separator; ③ Research on air compressor and expander technology; study of high-efficiency and low-cost cold and heat storage technology; 4Research on next-generation energy storage technology, including high-specific-energy-density battery technology such as lithium sulfur and lithium air batteries; research on hydrogen production and storage equipment, and technologies of large- scale hydrogen energy storage device with low cost and high efficiency; research and development of heat and cold storage devices with high capacity and energy density; key materials of thermal phase change energy storage.

In terms of integration and applications of energy storage systems, studies in this field mainly include: ① System integration, controlling technology, and engineering demonstration of an energy storage and power station of hundreds of megawatts; ② Architecture of battery energy storage system including energy storage battery pack, battery management system, power conversion system, microgrid control center, and energy management system; research on cascade utilization and safety management techniques such as battery reorganization, integration, and heat grooming; ③ Development of energy storage converter based on new device, topology, and control method; control of energy storage converter, energy storage battery management, and energy monitoring and scheduling system; ④ System integration and engineering application technologies of hydrogen, phase change, and flywheel energy storage; integration and test technology of seawater pumped storage and cryogenic energy storage system.

Physical energy storage will still be dominant. According to China’s National 13th Five-Year Plan, by the end of 2020, the cumulative installed capacity of pumped storage in China will be 40 GW. By the end of 2017, 28.49 GW has been completed, and the scale of projects under construction is 38.71 GW. It is expected that this target will be achieved by 2020.

Electrochemical energy storage will maintain steady growth. High-density distributed energy storage systems such as electric vehicles will fundamentally change the structure of the power grid. With the promotion and application of new energy vehicles, the performance and cost of battery systems have gradually become the main bottleneck delaying their rapid development. Future electrochemical energy storage will focus on battery systems with higher energy density, lower cost, better security, and longer lifetime.

Energy storage technology will be deeply integrated with renewable energy systems. Energy storage technology can achieve smooth power fluctuation, reduction of electric peaking, frequency modulation, and voltage regulation, and is considered an important means to achieve the large-scale integration of renewable energy systems to the power grid. With the development of smart microgrid and energy Internet, more flexible power-peaking resources will be developed to satisfy urgent demand, and the promotion of renewable energy grid connection will increase in the market.

(3)   Comparison and cooperation analysis based on key countries/regions and institutions

According to Table 1.2.5, the countries with the largest output of core papers in this research direction are the USA, China, Iran, and India. Among them, the core papers from USA and China account for 26.78% and 19.51% respectively, and the core papers from India and Iran account for more than 6%.

As evident from Table 1.2.6, the organizations with the largest output of core papers in this research direction are MIT, Imperial College of Science, Technology and Medicine, University of Malaya, Chinese Academy of Sciences, and Huazhong University of Science and Technology—each of them with more than 10 core papers.

According to Figure 1.2.3, China, the USA, Australia, the UK, and Germany are more concerned about the cooperation between countries or regions in this field. Among them, China has a large number of published papers, mainly in cooperation with the USA, Australia, and the UK.

According to Figure 1.2.4, Imperial College of Science, Technology and Medicine has a cooperative relationship with University of Malaya in certain areas.

In Table 1.2.7, among the countries that cite the most core papers, China accounts for more than 33%, and the USA accounts for nearly 20%. The percentages of cited core papers from India, the UK, Iran, Spain, Australia, Germany, and Italy all exceed 5%.

In Table 1.2.8, the institution that cites the most core papers is the Chinese Academy of Sciences, whose citing proportion is nearly 25%. The proportion of cited core papers from Tsinghua University and North China Electric Power University is more than 10%.

According to the analysis of the above data, the USA and China are at the forefront of the world’s core output and quotation for renewable power generation, and Chinese institutions have cited numerous core papers in recent years.

1.2.3 Key engineering technologies, equipment, and materials for the intelligentization of coal, oil, and gas exploitation

(1)  Concepts of research fronts

Intelligent mining began in the 1980s with automated mining and telemining/distance mining. In 1992, Finland proposed the Intellimine program, and the concept of intelligent coal mining was introduced. At present, oil and gas exploitation in China urgently requires intelligent dynamic control using intelligent equipment and technology to reduce production costs and improve the production and recovery of oil and gas. Intelligent mining refers to the mining operation process without manual intervention, independently completed using

《Table 1.2.5》

Table 1.2.5 Countries or regions with the greatest output of core papers on the “renewable energy power generation and energy storage: energy-saving and environment-friendly technologies”

《Table 1.2.6》

Table 1.2.6 Institutions with the greatest output of core papers on the “renewable energy power generation and energy storage: energy- saving and environment-friendly technologies”

《Figure 1.2.3》

Figure 1.2.3 Collaboration network among major countries in the engineering research front of “renewable energy power generation and energy storage: energy-saving and environment- friendly technologies”

mining equipment through intelligent perception of mining environment, intelligent control of mining equipment, and autonomous cruising of mining operations. The intelligent mining of coal, oil, and gas is a revolutionary technology based on mechanized mining and automated mining, through the deep integration of informatization and industrialization to improve production efficiency and economic benefits.

(2)  Fronts of engineering science branches

Key engineering technologies, equipment, and materials for intelligent coal mining. They are the deep integration of three technical units: environmental perception, intelligent decision, and automatic control, involving five branches of engineering science: engineering environmental perception, digital mining, mine Internet of things, big data and cloud computing, and automatic control. Engineering environment

《Figure 1.2.4》

Figure 1.2.4 Collaboration network among major institutions in the engineering research front of “renewable energy power generation and energy storage: energy-saving and environment-friendly technologies”

《Table 1.2.7》

Table 1.2.7 Countries or regions with the greatest output of citing papers on the “renewable energy power generation and energy storage: energy-saving and environment-friendly technologies”

《Table 1.2.8》

Table 1.2.8 Institutions with the greatest output of citing papers on the “renewable energy power generation and energy storage: energy- saving and environment-friendly technologies”

perception is an automatic detection and transmission technology for underground equipment, personnel, and disasters. It aims to achieve automated meticulous monitoring of the whole mining process in underground complex geological conditions. In this field, Australia focuses on intelligent detection of coal seam geological structures based on thermal infrared imaging whereas China focuses on intelligent detection of the position and pose of mining equipment. The equipment level of intelligent mining in China is equivalent to that of foreign countries. Chinese mining machines have online awareness of fault parameters and operation parameters, shearer drum cutting memory program, and wireless remote control system, which realize a remote monitoring system of mining machines. Foreign mainstream hydraulic supports can achieve remote control and system fault diagnosis whereas the reliability of hydraulic support electro-hydraulic control systems in China still has a certain gap with foreign technology. At present, the intelligence of Chinese independent development conveyors is mainly reflected in soft start control, chain automatic tensioning, and monitoring of operating conditions. The intelligent integrated system of a fully mechanized mining face can realize intelligent integrated control and cooperative interlocking of mining machine, hydraulic support, conveyor, and other equipment in the mining face. Automatic control indicates that the mining machine can achieve self-regulation and autonomous cruising through pre-programming without manual intervention to complete the mining operation independently. In this field, Australia focuses on the development of mining machine memory cutting and autonomous navigation technology, whereas China focuses on remote control technology of mining equipment.

Key engineering technologies, equipment, and materials for digital mines and mine system network. Focusing on mine spatial data and models, it is a concentrated expression of spatial information technology, network technology, and visualization technology in the comprehensive application of mining enterprises. Its basic task is to provide data security and technical support for the visualization, refinement, and intelligent control of the whole process of mine production through unified space-time benchmarks, unified data standards, unified network structure, and unified integration platform. The main directions of the future of digital mines include mine spatial data warehouse and data update technology, mine data mining and knowledge discovery technology, true 3D solid modeling, and virtual mining technology. The mine system network consists of the perception layer, transport layer, analysis layer, and application layer. The mine sensor network is built on a high-speed network covering the mine ground surface and underground. The mine environment, equipment, and personnel are connected in real time through various sensors to the real-time monitoring, sensing, communication, and control of the environment, equipment health, and personnel safety posture. The future development of the mine system networks is focused on multi-network convergence transmission technology and multi-parameter information analysis and processing technology. As the scope of coverage of mine system networks becomes increasingly wider, the amount of generated data of the “human, machine, and physical” ternary worlds interacting and integrating in the information space and available on the Internet is also increasing, and the data are inherent. The extraction and utilization of value must be supported by ultra-large-scale and highly scalable cloud computing technology. Large data cloud computing technology for coal mines is still in its infancy. Moreover, it needs to focus on the development of unified technical standards and data modeling.

Key engineering technology, equipment, and materials for intelligent drilling. Intelligent drilling combines large data and artificial intelligence, and uses advanced detection, closed-loop control, and precision guidance, which can effectively avoid drilling risks, form high-quality wellbore, improve drilling speed and drilling ratio, and reduce drilling cost. It is the basis for the smooth development of well completion and production. Intelligent drilling uses the big data of the drilling process to adaptively optimize the drilling rock-breaking parameters and intelligently regulate the well trajectory by analyzing the real-time working conditions. The key engineering technology of intelligent drilling involves data bidirectional efficient transmission technology, closed- loop intelligent regulation technology, and intelligent drilling guidance technology. The drilling process generates massive data. To ensure the dynamic interaction between the ground control system and the downhole information, it is necessary to use an intelligent drill pipe and other equipment for more efficient data transmission. The use of intelligent analysis of drilling data, optimization of drilling parameters through signal feedback, and formation of closed-loop control of drilling information significantly improves the efficiency of drilling data processing, specifically involving unmanned drilling rigs, intelligent pressure control, integrated driller control, and other equipment. Intelligent guidance uses strata conditions and ground control commands to control the drilling speed of the drill bit for targeted directional drilling, specifically involving intelligent drill bits and other equipment. To improve the performance of tools under complex conditions, carbon fiber composites, high-entropy alloys, super steels, pure phase polycrystalline diamond, and other materials have received extensive attention at home and abroad. Furthermore, bionic drilling fluids and supramolecular polymer drilling fluids have been extensively studied at home and abroad as important carriers for wellbore drilling and smooth progress. Currently, Norway has applied highly flexible, executable multi-task unmanned rigs to the field. Baker Hughes’ first TerrAdapt adaptive drill bit has dramatically reduced the frequency of downhole faults through automated controls. The British North Sea Babbage Oilfield used intelligent closed-loop control and intelligent drill pipe to efficiently transmit data through the intelligent drill pipe, which has increased the penetration rate by nearly 200%. Schlumberger, Baker Hughes, Weatherford, Halliburton, etc. have used intelligent steering technology for drilling sites.

Key technology, equipment, and materials for intelligent well completion. Intelligent well completion uses advanced sensing, transmission, and automatic control equipment, combined with large data, artificial intelligence, etc. It can monitor and control the production of oil and gas in real time including interlayer isolation, permanent monitoring, flow control, and sand control, and provide strong support for the intelligent production. The key technology of intelligent well completion is mainly related to oil-well inflow control and intelligent optimization of completion parameters. At present, an integrated well management control system integrates downhole monitoring, data transmission, and stratified flow control. It can realize reservoir information management, dynamic data sharing, and intelligent flow control. It is widely studied at home and abroad. It involves downhole sensors, downhole production controller, multi-channel packer, etc. At present, the Beck Hughes InCharge completion system can control up to 12 production layers using an electric hydraulic drive and achieve stepless throttling. The Schlumberger Manara well completion system can conduct data wireless transmission, multi-channel separation, and hierarchical monitoring. In addition, Halliburton and China National Petroleum Corporation (CNPC) launched SmartWell and EIC- Riped completion systems. Furthermore, the multi-function intelligent nano completion fluid system of nanomaterials and completion fluids can automatically identify and deal with complicated conditions or accidents in the downhole, which has become the trend of future development.

Key engineering technology, equipment, and materials for intelligent production. Intelligent production is the dynamic management and optimization of the whole life cycle of oil and gas field based on big data and trail learning. Intelligent production of oil and gas can be achieved using the effective integration of data, instruments and equipment, and field operation through the collaborative work of research branches. Intelligent production utilizes a sensing device to collect the downhole data, subsequently transmits it to the ground system for intelligent analysis and signal feedback, and carries out the control instruction through the ground and downhole equipment to continue the intelligent management and optimization to the well work condition. The key engineering technology of intelligent production involves the dynamic real-time four-dimensional interpretation technology of reservoir production, intelligent displacing technology to improve oil recovery, and intelligent analysis and utilization technology of multivariate massive data. The intelligent production of oil and gas mainly involves the intelligent monitoring of oil and gas fields, capturing the dynamic information of each link to provide the support for the real-time interpretation of oil and gas reservoir, and the intelligent analysis of gas and oil exploitation. Moreover, the massive data produced during the field operation must be analyzed intelligently using deep learning and data mining, which impose stringent requirements on the performance of big-data storage and computing equipment. The nano intelligent oil displacement agent has attracted increasing attention at home and abroad because it can remarkably improve the recovery rate of a low-permeability reservoir. To analyze the production dynamics of oil and gas reservoirs, Anadarko Petroleum is building a huge monitoring database based on microbial DNA in Delaware Basin. Oil reservoir robot, which has become a hot research topic globally, can monitor the temperature and pressure data under complex conditions, and Saudi Aramco has carried out active research in this field. Shell used big data and cloud computing to establish an oil field management system, which initially achieved automatic control of production. To improve oil recovery, CNPC and Sinopec Group have been actively exploring the improvement of oil recovery using intelligent fine water injection and an intelligent nano flooding agent. The Natural Resources Corp., Canada also carried out a pilot test to enhance the recovery rate of polymer nano microspheres. In addition, China has developed supercomputers rapidly and has reached the international advanced level, which lays an important foundation for the study of massive data storage, calculation, and analysis of oil and gas exploitation.

(3)  Development status and future development trend

The development direction of intelligent mining is to achieve a real-time and intelligent full life cycle regulation of the coal and oil-gas production process, based on the dynamic information of the production process, relevant engineering technology, equipment, and material. At present, a significant amount of research has been carried out in the key fields of intelligent mining at home and abroad. However, the entire process of intelligent mining has not been realized. The following major breakthroughs must be achieved in the future.

Deep integration of engineering equipment, materials, and artificial intelligence. Efficient intelligent development of coal, oil, and gas is realized through effective data acquisition, hierarchical intelligent production, and data mining and intelligent analysis. Advanced computer, optoelectronic, and navigation technology are used to automatically locate mining equipment and personnel in order to achieve safety monitoring and accurate mining. Moreover, the deep integration of materials and artificial intelligence will help improve the performance of engineering equipment in all directions, realize the automatic exploration and detection of the unknown area of mining stopes, and even automatically identify and deal with the complicated production conditions or accidents in underground mines.

Integration technology of intelligent data acquisition, efficient transmission, intelligent analysis, and intelligent control. Intelligent analysis is adopted to determine the real-time production dynamics and use intelligent control in the mine production process based on the acquisition of multivariate data to achieve data collection, transmission, analysis, control, and coordination work in all aspects.

(4)    Countries, institutions, and the comparison and cooperation between them

According to Table 1.2.9, the countries with the largest numbers of core papers in this research direction are China, India, Canada, Australia, and the UK. Among them, the core papers from China exceed 50%, and the core papers from other countries account for less than 10%. According to Table 1.2.10, the institutions with the largest number of core patents in this research direction are Xi'an University of Science and Technology, Luohe Medical College, and China University of Mining and Technology, Beijing. Among them, Xi'an University of Science and Technology and Luohe Medical College have a core patent ratio exceeding 5%.

According to Figure 1.2.5, countries such as China, Australia, USA, UK, and Italy have paid more attention to the cooperation among nations or regions in this research direction. Among them, China has built a cooperative relationship with Australia, the USA, and the UK, with the largest number of co- published core paper. Although India and Canada have a high number of core papers, they have no cooperative relationship with other countries.

According to Figure 1.2.6, the institutions with a cooperative relationship with other institutions are Luohe Medical College, Chinese Academy of Sciences, Henan Vocational College of Quality Engineering, Henan Polytechnic Institute, and Commonwealth Scientific and Industrial Research Organisation (CSIRO). Among them, Luohe Medical College has built a cooperative relationship with Henan Vocational College of Quality Engineering and Henan Polytechnic Institute. Furthermore, they have the largest number of co-published core papers. Xi'an University of Science and Technology of Xi'an, China has the largest number of publications. However, it has no co-published papers.

According to Table 1.2.11, China, Australia, the USA, the UK, and India have produced the largest number of cited core papers in this research direction. Among them, more than 50% of the core papers from China have been cited, whereas only 10.2% from Australia have been cited. According to Table 1.2.12, the most productive institutions in terms of the

《Table 1.2.9》

Table 1.2.9 Countries or regions with the greatest output of core papers on the “key engineering technologies, equipment, and materials for the intelligentization of coal, oil, and gas exploitation”

《Table 1.2.10》

Table 1.2.10 Institutions with the greatest output of core papers on the “key engineering technologies, equipment, and materials for the intelligentization of coal, oil, and gas exploitation”

number of core papers published in this research direction are China University of Mining and Technology, Chinese Academy of Sciences, and Shandong University of Science and Technology. Among them, the core paper outputs of China University of Mining and Technology and Chinese Academy of Sciences are more than 20%.

《2 Engineering development fronts》

2 Engineering development fronts

《2.1 Development trends in the Top 14 engineering development fronts》

2.1 Development trends in the Top 14 engineering development fronts

The top 14 engineering development fronts assessed by

《Figure 1.2.5》

Figure 1.2.5 Collaboration network among major countries or regions in the engineering research front of “key engineering technologies, equipment, and materials for the intelligentization of coal, oil, and gas exploitation”

the Field Group of Energy & Mining Engineering are shown in Table 2.1.1. These fronts include the fields of energy and electrical science, technology, and engineering; nuclear science, technology, and engineering; geology resources science, technology, and engineering; mining science, technology, and engineering. Among these top 14 development fronts, “research and application of wireless power transmission and its related equipment,” “green mining technology (coal, oil, gas, ores),” and “safe, intelligent, and precise mining technology and equipment” are emerging fronts. “Development and utilization system of fossil energy (coal, and unconventional oil and gas) and core technology and equipment,” “spent fuel reprocessing and nuclear facility instrumentation,” “renewable resources generation system and its operation and control,” “advanced reactor technology and equipment development,” “new tools and materials for petroleum engineering,” “logging identification of unconventional reservoirs,” and “3D geological modeling technology” are further developments of traditional research fields. “Advanced nuclear fuel technology research and development” is the subversive front. “High-voltage and high- power power electronic devices and equipment in power systems,” “advanced energy storage technology in energy and power systems,” and “using wide spectral remote sensing techniques to explore the mineral deposits and geothermal resources” are the fronts of interdisciplinary integration. The numbers of core papers published each year from 2012 to 2017 for each of the top 14 engineering development fronts are listed in Table 2.1.2.

《Figure 1.2.6》

Figure 1.2.6 Collaboration network among major institutions in the engineering research front of “key engineering technologies, equipment, and materials for the intelligentization of coal, oil, and gas exploitation”

《Table 1.2.11》

Table 1.2.11 Countries or regions with the greatest output of citing papers on the “key engineering technologies, equipment, and materials for the intelligentization of coal, oil, and gas exploitation”

《Table 1.2.12》

Table 1.2.12 Institutes with the greatest output of citing papers on the “key engineering technologies, equipment, and materials for the intelligentization of coal, oil, and gas exploitation”

(1)  Development and utilization system of fossil energy (coal, and unconventional oil and gas) and core technology and equipment

The key technology and equipment of coal exploitation can be divided into two aspects: mining and tunneling. Complete fully mechanized automation, and intelligent and unmanned mining technology and equipment generally refers to the application of automation and intelligent technology in fully mechanized mining equipment to achieve the same work with only a few people, or with unmanned mining on the working face. Developing fully mechanized automation and intelligent technology to achieve unmanned mining on the coal face is the developmental direction of coal mining technology. The main technical orientations include hydraulic-powered support and surrounding rock-coupling adaptive technology; automated top coal caving control systems based on intelligent decision-making, sequential control, memory coal caving, and manual intervention cooperative control; reliable, real-time, and safe working face multi-machine cooperative control systems; automation of the working face end support system and the advanced support system.

Intelligent rapid tunneling technology and equipment for coal roadways refers to the driving equipment for coal roadways, such as tunneling machines, anchor machines, crushing transfer machines, and belt conveyors, which have the ability to perceive, memorize, learn, and perform decision- making tasks, controlled by a hubbed automatic control system, with remote visual monitoring, as a means to ensure safe and efficient tunneling technology of “full face rapid excavation and parallel operation of excavation support

《Table 2.1.1》

Table 2.1.1 Top 14 engineering development fronts in energy & mining engineering