The world is experiencing rapid industrial, economic, and social changes. Underpinned by a new round of technological and industrial revolution, the trend toward energy diversification, clean energy, and a low-carbon economy is gaining momentum. The energy landscape is undergoing profound changes as energy restructuring accelerates [1]. Technological progress has a huge impact on the structure of global energy supply, resulting in greater supply, an extended timescale for the depletion of fossil-based energy resources [2], and a revitalized competitive edge for fossil energy produced and utilized in a clean and efficient manner. Fast-growing non-fossil fuels help diversify the energy portfolio and spur a transition toward energy production and consumption. Distributed energy systems emerge as renewable energy grows rapidly. Power generation using renewable energy sources increasingly requires grid connection. Meanwhile, electrical grids, including large grids and microgrids, are becoming smarter. The widespread adoption of emerging energy technologies is expected to give rise to new business clusters and sources of growth on many fronts, such as the clean and efficient use of fossil fuels, marine and unconventional oil and gas development, the safe use of nuclear energy, the large-scale development and utilization of renewable energy, the deployment of smart grids, large-scale energy storage and distributed energy usage, and the adoption of high-performance energy equipment and key materials [3]. Energy technology innovation is thus becoming the driving force behind the transformation of the energy industry.

Resources, the environment, and the economy will remain themajor challenges to the world’s energy development in the next two decades. Developed countries and emerging economies will both continue to introduce policies to accelerate the development and commercialization of new energy technologies to seek an advantage in the new round of industry growth driven by green and low-carbon energy technologies. It is a long-term task for China to promote the revolution in the production and consumption of energy and ensure national energy security [4]. Science and technology (S&T) is the key factor to trigger and bolster the energy revolution in China [5]. The long-term, healthy, and sustainable development of a large and complex energy system will be driven and underpinned by technological innovation. Therefore, it is important to understand domestic and global trends in energy development as well as strategic energy engineering needs when formulating the future innovation system required by China. Such foresight will help identify the key areas, technological priorities, and measures needed to formulate China’s medium- and long-term energy engineering development plans and initiatives.

China is the world’s largest energy producer and consumer. The rapid development of its energy industry has made important contributions to the national economy and social development. However, extensive growth and demand-oriented energy supply have resulted in the rapidly expanding production and consumption of energy resources. In 2015, China accounted for 23 % of global energy consumption and contributed 43 % to its growth. Although the 1.5 % increase in that year marked the lowest growth in nearly 20 years, China has been the leading contributor to global energy consumption growth for 15 consecutive years [6]. Meanwhile, the overall size and rate of growth vary considerably among the types of energy sources, presenting a complex picture of differences and challenges.

China’s resource endowment is widely imbalanced. The country has a large amount of fossil energy resources, mostly coal. Moreover, although reserves of oil and gas are relatively insufficient, there is great potential in unconventional hydrocarbon resources. However, unlike energy-abundant economies, China’s reserves per capita are relatively low, characterized by a shortage of high-quality green resources, geologically and technologically challenging conditions in the development of coal, oil, and gas reserves, and inadequate prospecting of and a lack of economic efficiency for unconventional resources [7]. Most of the renewable energy resources suitable for large-scale development are found in the western region far from load centers. Indeed, the geographical disconnection between the production and consumption of energy is noticeable. Resource endowment is badly out of line with water needs, the ecological environment, and economic growth and there is a long-standing need for large-scale, long-distance energy transportation.

Far from being produced and utilized in a highly sophisticated manner, coal and other conventional fossil fuels have too large a share of China’s primary energy mix. China is the world’s largest coal producer and consumer. Coal, as the main source of energy, makes an important contribution to economic and social development as well as to energy security. However, from the perspective of production, large coalmines are being built despite the issue of massive overcapacity and the adoption of clean coal technology is limited; from the perspective of consumption, there is considerable pressure on controlling air pollution, reducing emissions and protecting the environment, and clean and efficient use is yet to be increased. As a significant producer and consumer of oil and gas, the commercial exploitation of unconventional resources is taking place in China. However, domestic oil and gas resources are insufficient to meet the huge need for energy, as it is increasingly difficult to sustain a steady growth rate of oil production, and gas production is slowing because of a decline in deposit grades. All this leads to soaring oil and gas dependency rates.

Despite its rapid development in China, non-fossil energy has low economies of scale and plays a limited role in replacing conventional fossil fuels. Nuclear power is a high-tech sector in which China is poised to gain a competitive edge, and the country is well prepared to embrace large-scale nuclear power generation with its proprietary Generation III nuclear power unit, equipment, and nuclear fuels. However, during energy restructuring, the role of nuclear power is limited because of the size of the installed capacity. China is the world’s largest renewable power generator with its solar power and wind power capacities growing rapidly. Indeed, as the world’s leading wind power market, China has the largest new capacity installed for wind power. It is also the world’s largest producer of solar power with remarkably improved competitiveness in power generation. However, a number of issues concerning equipment manufacturing, operation and management, and power utilization have yet to be addressed. China has the world’s largest power system for large-scale distribution and optimization across the country. Smart grids are making headway; however, renewable energy is yet to be improved in terms of its supporting facilities, economic benefits, and the reliability of its transmission and distribution.

Although the energy supply constraints on China’s economic development have been alleviated, environmental protection and climate change have become a major concern in the country’s energy development. Energy efficiency is low, the percentage of electricity in end-use energy consumption is small, and per capita electricity consumption is far below that of advanced economies. Overall, there is huge energy-saving potential. To meet energy demand and ensure national energy security, optimize the structure of energy production and consumption, improve the ecological environment and cope with climate change, and cultivate new economic growth momentum, there is therefore an urgent need for energy engineering S&T innovations.

Since the 12th Five-Year Plan, China has picked up the pace in bolstering its research and development (R&D) efforts and promoting industrialization in the energy sector. Proprietary innovations together with foreign technologies that have been imported, adapted, and re-innovated continue to enhance technological competency and innovation in various areas. China has become a leading player in a few domains of energy [5]. For example, it is taking the lead in coalmine construction and mining technology, with major breakthroughs in the clean and efficient processing and use of coal, such as ultra-low emissions from power generation, advanced coal-fired power generation, and coal-to-chemicals technologies. In the oil and gas sector, China leads the way in exploration theories and techniques, controlled water injection in mature fields, and chemical flooding for enhanced oil recovery, with significant progress in the exploration and production of deepwater drilling, tight gas, shale gas, tight oil, and coal-bed methane. Further, the nuclear power industry has improved its ability to innovate, mastering most Generation III nuclear power technologies and launching its own large pressurized water reactors. The renewable energy boom is seeing new generating capacity installed exceeding that for fossil fuels as China keeps pace with the world market in solar power generation and begins to lead the design and manufacture of large turbine blades. In addition, excellent results have been achieved in ultra-high voltage (UHV)/flexible electricity transmission, large grid management and power dispatching and renewable energy generation, while a good foundation has been provided for R&D, equipment manufacturing, and the adoption of smart grids. Finally, emerging sectors such as distributed power, energy storage, energy-saving technology, and fuel cells are making progress.

Meanwhile, China is faced with a number of issues in the development of energy technology. Its innovation mechanisms in energy exploration, processing, utilization, and equipment manufacturing are outdated. The coal industry needs to become cleaner and more efficient, which requires advanced coal technology to be developed and promoted. Technological constraints on the development of unconventional oil and gas resources are yet to be overcome, and the commercial exploitation of unconventional and deepwater deposits still has a long way to go. The installed nuclear power capacity is yet to be expanded and nuclear technology needs to become safer and more efficient. Moreover, innovation in renewable energy technology is inadequate, with core equipment for photovoltaic (PV) cells, concentrated solar power, and geothermal power largely dependent on foreign imports, issues such as grid connection and power utilization yet to be addressed, and smart grids subject to a number of technology and market constraints. Meanwhile, major energy projects rely heavily on imported equipment [5]. With respect to technological forefronts, R&D and industrialization efforts need to be strengthened in areas such as ultra-low emissions from coal-fired power generation, integrated gasification combined cycle (IGCC)/integrated gasification fuel cell (IGFC), micro-earthquake, digital oilfields, volume fracturing of horizontal wells, deepwater and unconventional exploration and production, UHV, Generations III and IV nuclear power, smart grids, energy-saving and new energy vehicles, PV, wind power, fuel cells, and large-scale energy storage.

The medium- and long-term development of energy engineering S&T in China should be in line with the current stage of socioeconomic development and national strategic priorities. Given the irreplaceable role of fossil fuels in China’s energy system, it is important to cut high-carbon energy by using clean and efficient energy technologies; smart grids, the energy Internet, and energy-saving innovations will help boost the percentage of electricity in end-use energy consumption and improve significantly the overall efficiency of the energy system to revolutionize the energy-saving and efficient energy system [8]. Therefore, bearing in mind the guiding rules for the development of energy technologies, green production technologies and clean, lowcarbon, and intensive energy utilization options will be promoted, with priority given to energy-saving and emissions reduction technologies. A complete value chain will be created, comprising innovation, R&D, commercialization, marketing, and application; new energy technologies and equipment solutions will be identified; and R&D and domestic equipment manufacturing will be bolstered through a series of demonstration projects. The fundamental purpose is to establish an internationally competitive energy engineering S&T system in line with the development needs and resource characteristics of China to reshape its energy system, allowing a shift from a simple clean and efficient mode of energy exploitation and utilization to a green and low-carbon one, and eventually to a smart and diversified energy system. Overall, the country needs energy products and services that are eco-friendly and meet the needs for sustainable energy development as well as facilitate the transformation from a major energy producer/consumer to an energy superpower.

3.2.1 Coal engineering

Coal transformation will focus on eco-friendly mining and low-carbon coal-fired power generation. First, safe and efficient mining remains the key issue in coal development. Water conservation and the ecological restoration of surface disturbances in the main coal-producing areas of western China represent an important engineering topic. Meanwhile, a number of technological challenges are yet to be tackled, including precise exploration; safe and efficient coal mining in difficult coal seams; the coordinated mining of coal, uranium, oil and gas, and other associated minerals; and intelligent mining and smart mines. Second, it is important that coal is used in an efficient, energy-saving, water-saving, and clean manner. The research and development of next-generation clean, high-efficiency, and near zero emissions technology will pick up pace, and curbing carbon dioxide emissions will remain a major challenge [5]. 10 MW largescale permanent magnet synchronous turbines, 10 MW doubly-fed speed-up turbines, and 3 MW+ low-speed turbines working at low wind speeds will be developed. Exploratory research on highaltitude (6 000–12 000 m) wind turbines will be carried out. Offshore wind farm technologies will be developed and deployed. Other research topics include wind power big data, the design of wind farms, and the optimization of operations. Fourth, in the field of biomass energy, technological options for biomass conversion, clean production and efficient utilization, the genetic engineering of energy plants, and biomass oil purification and production will be explored. Waste-to-energy technologies using waste from agriculture, forestry, and animal husbandry will be developed, targeting technical issues in clean conversion, low-cost separation and purification, and scale-up engineering for biodiesel, fuel alcohol, pyrolysis oil, synthetic oil, and other biomass liquid fuels. Algae also represent an important direction of biomass energy. Fifth, the focus of hydropower development is on the management of hydropower operations, including the optimal operation of cascaded hydropower systems, safety management and risk mitigation of reservoirs and dams, and ultra-high-voltage direct-current (UHVDC) hydroelectricity transmission and peak shift. Research on technology packages for large-scale, interconnected hydropower management will be carried out. Sixth, in the field of geothermal energy, two common issues are to be tackled: artificial splitting and fracturing techniques and anti-corrosion anti-scaling techniques for geothermal fluids. R&D efforts on enhanced geothermal generation and low-temperature geothermal heating and cooling will be sped up. Seventh, the sources and uses of hydrogen fuels will be expanded. From fossil fuels to renewable energy, physical storage to hydrogen carriers, chemical hydrogen to hydrogen-led carbon-free energy, integrated research efforts will be pursued to create a hydrogen energy system for eco-friendly production and the efficient storage and use of hydrogen. Natural gas/ hydrogen transportation solutions and flexible-fuel burners will be developed. The technical barriers to the use of fuel cells in distributed power generation will be overcome. Eighth, technical issues concerning efficiency, reliability, cost, and environmental impact in the production and use of marine energy will be addressed. Key technologies for wave power generation, tidal farms, and desalination will be developed and commercialized.

3.2.5 Power engineering

The global development of power engineering is characterized by safety, reliability, cost-effectiveness, and smart technology. Emphasis will placed be on smart grids, the grid integration of large-capacity renewable energy sources, distributed microgrid for renewable energy, direct current (DC) power grids, and alternating current/direct current (AC-DC) power grids. Technical barriers to the grid integration of large-capacity renewable energy sources will be overcome to enable largecapacity, long-distance grid integration. Internet-based interactive grid technologies will be developed to turn power grids into energy-sharing platforms. The smart grid is the key factor to the development of power systems. Flexible power transmission and coordination technologies will be promoted to improve grid stability and operating efficiency. Distributed power generation, microgrid, demand response, and flexible energy systems will see wider application. Technological breakthroughs in largescale power storage are needed. A series of power engineering advancements will be achieved, including integrated largescale renewable energy absorption solutions, high-voltage highcapacity flexible DC transmission and grid integration systems, ultra-long-distance ±1 100 kV UHVDC transmission, and smart power systems for smart cities.

Taking into account such factors as technological innovation, technology potential and readiness, and market demand, the key energy engineering S&T topics for 2035 in the coal, oil and gas, nuclear energy, electricity, and renewable energy sectors are ① clean and efficient technologies for the development and utilization of fossil energy sources, ② exploration and production technologies for unconventional and deepwater oil and gas resources, ③ proprietary nuclear power generation technologies and nuclear waste treatment technologies, ④ smart grid and energy storage technologies, and ⑤ technologies for large-scale renewable energy utilization. These main technology priorities are shown in Table 1 [9]. In addition, the basic research, new materials, and IT infrastructure that underpin the development of energy engineering will be promoted.

In the next two decades, the urbanization process in China will undergo a fundamental shift characterized by the completion of industrialization and profound change in production and consumption patterns. Demand for energy resources will remain strong as traditional industry and infrastructure construction upgrades. A substantial increase in demand for new technologies will be seen in the renewable energy, nuclear energy, natural gas, and carbon emission reduction sectors. Although demand for energy will continue to grow as a whole, energy growth will become less closely correlated with economic growth because of economic development and efficiency improvement. By 2035, fossil fuels will continue to play a major role in the energy mix despite the challenges to the traditional fossil fuel-based energy structure. Meanwhile, renewable energy will maintain strong momentum, with non-fossil energy and natural gas accounting for increasing proportions of end-use energy consumption as well as primary and secondary energy sources. The pattern of energy growth will become intensive rather than extensive and the role of energy in economic growth will be more ecoresponsible and climate-friendly. While pursuing quality and sustainability, the energy industry will experience profound changes both in its forms and in its characteristics [12,13], entering a new era characterized by low-carbon development, smart technology, and diversification.

Conventional fossil fuel energy supply and intelligent exploration and production will be greatly boosted. Technological breakthroughs and the wide adoption of technologies to evaluate clean coal resources, the precision production of energy, transparent geophysics with integrated detection, smart mines, the development of unconventional oil and gas resources, deep-well exploration and production, the development of complex reservoirs, and EOR will significantly bolster the safety, efficiency, and synergy of energy development. China’s peak for coal mining is approaching, while conventional oil production remains steady. Unconventional oil and gas technology may see a major breakthrough, and unconventional and deepwater oil and gas resources, coal-to-chemicals, and bio-fuels as alternative energy sources will greatly change the landscape of oil and gas supply. Electricity generation will continue to grow in the long term. Renewable energy such as wind power and photovoltaics will account for a larger proportion. Renewable and nuclear power generation will lead to a fundamental change in the structure of power sources. Non-fossil fuel energy will dominate the newly increased energy and electricity generation. The goal of nonfossil fuels accounting for 20 % of the primary energy structure by 2030 is likely to be achieved ahead of schedule.

While total energy consumption will increase, the structure of energy consumption will continue to be optimized. End-use energy and electricity structures will improve significantly. Coal use, mainly concentrated in power generation, will fall slowly. Oil consumption will remain stable as a whole. Natural gas consumption will grow remarkably. Access to energy and electricity in both urban and rural areas will be significantly improved. For electricity consumption, the emergence of load demand response, smart building, smart appliance, and electric vehicle technologies will allow interactions between end-users and power grids and meet the need for diversified energy. Smart grids will raise energy efficiency, enable the optimized allocation of energy resources, improve the cost-effectiveness of energy transmission, meet the needs of diversified and interactive power consumption, and ultimately bring about a fundamental change in end-use energy consumption. Energy-saving regulations and measures will be developed. Smart manufacturing will further explore the energy-saving potential of industrial energy consumption. Smart building systems will optimize the energy efficiency of buildings and reduce energy consumption. Buildings will be equipped with intelligent control systems and interfaced with smart grids and distributed energy systems. Smart transportation technology will lead to a revolution in transport modes as well as the energy dissipation structure of vehicles [2]. Smart manufacturing, smart building, and smart transportation will in turn give rise to a structural change on the supply side. The interactive mechanism between end-users and power grids will greatly improve power consumption in end-use and energy efficiency, while offering new options for the better utilization of grid assets.

The industrial development framework will undergo profound changes, leading to an overall improvement in the technological strengths and an internationally leading position in many energy sectors, which will in turn reshape the geopolitical landscape in the global energy market. Coal production will continue to be mainly concentrated in Shanxi, Shaanxi, Inner Mongolia, Ningxia, and Northern Xinjiang. Oil and gas production growth will derive largely from deepwater and unconventional resources. The power grid system will undergo a major transformation, resulting in the largest and most complex hybrid power grid in the world comprising UHV transmission networks and microgrids. The trendsetting energy interconnection system will bolster large-scale, long-distance power transmission and coal transportation. Large-scale renewable electricity will be absorbed and distributed locally in a cost-effective manner to bridge the geographical distance between energy production and consumption. The costs of wind power and solar power are expected to fall to a similar level to those for power generation using conventional energy sources. Non-fossil energy will become as competitive as conventional fossil fuels. Technological advancements in energy production and consumption will enjoy an internationally leading position, with the emergence of a number of globally competitive energy companies. Cross-border, intercontinental power grid connection will be promoted, endowing China with a growing voice in the global energy market and helping pave the path to the commanding heights of emerging energy industries [2]. Meanwhile, the coordinated development of energy, the ecosystem, technology, and the socioeconomic system will be promoted. The transformation of the energy industry will benefit from financial innovations and advancements in other sectors, thereby improving the exploration, extraction, conversion, storage, sharing, and application of energy sources. Energy is for everyone to explore, control, gain access to, and benefit from. Low-carbon and intelligent energy production and consumption will shape the outlook of energy, the economy, and society by 2035.

Energy engineering S&T innovations are facilitating a global shift in the energy industry characterized by a low-carbon, climatefriendly, and eco-responsible energy structure and smart energy services. China’s energy industry will become more technologyand knowledge-intensive as well as highly integrated with the Internet, energy Internet, and Internet of Things. The national energy network will be complemented by regional and end-use energy networks. Smart grids, distributed power generation systems, and microgrids will be widely implemented. Smart manufacturing, smart building, and smart transportation will continue to inspire a structural change on the supply side. A diversified mix of options for energy supply and consumption will give rise to an integrated approach to the development of the energy industry that will reshape China’s energy system.

A comprehensive range of long-term measures should be taken to bolster the fundamental role of energy engineering innovation and ensure that China’s technological strengths in energy engineering and application can hold a leading position in the long run.

(1) The national energy plan emphasizes the clean and efficient utilization of fossil energy and large-scale development of nuclear and renewable energy, insisting on the collateral development of these two kinds of technology. Strategic planning for the integration of a diversified mix of energy sources is strengthened and next-generation energy technologies, the including energy Internet, are taken into consideration. The development of new energy technologies is supported by China’s strategic planning for emerging industries. A national innovation fund for technical know-how and industry of disruptive energy will be set up.

(2) Existing energy S&T resources should be consolidated to promote international big science plans and projects in the energy sectors in which China enjoys a leading position, such as coal, nuclear energy, and electricity. A series of key initiatives concerning the integration of a variety of energy sources and research projects such as the “integrated transparent detection of energy resources,” “intelligent clean energy development,” and “energy Internet” can be planned. National energy laboratories should be set up in Beijing, Shanghai, and Shenzhen, targeting cutting-edge, disruptive energy technologies as well as multidisciplinary basic research topics involving materials, information technology, and machinery. There is ongoing support for research efforts in energy strategy and technology policy. Highend think-tanks and large-scale market-based comprehensive energy research institutions will be set up and measures will be taken to nurture and support individuals and groups working on energy S&T innovations.

(3) Leading energy brands and companies should be encouraged to go global, offering internationally competitive products, equipment, and infrastructure in nuclear energy, coal, and electricity. Offshore energy technology markets and energy supply and transit hubs will be explored. An integrated approach will be taken to strengthen governance, regulation, and innovation policy in the energy sector. Further reforms in energy pricing will be launched in recognition of the nature of energy as a commodity. Natural resources consumption tax and environmental taxes (including carbon tax) will be introduced or improved. A series of initiatives can be established to promote responsible energy consumption, encourage energy-saving practices, and facilitate a shift to a clean, efficient, low-carbon, diversified market signaling system.

The support and help from the following project team members were invaluable in the preparation of this paper: Su Gang, Zhang Guosheng, Li Peng, Huhe Taoli, Cao Zhiguo, Wang Hongjian, Li Qiming, Guo Qifeng, Liang Kun, Fu Xiaopeng, and Fan Jingli.