An overview of the policies and models of integrated development for solar and wind power generation in China

LiWei Yang,XiaoQing Gao,ZhenChao Li

Key Laboratory of Land Surface Progress and Climate Change in Cold and Arid Regions,Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,China

Keywords: Renewable energy Solar PV Wind power Policies Integrated development

ABSTRACT Under the goal of “Carbon Emission Peak and Carbon Neutralization”,the integrated development between various industries and renewable energy (photovoltaic,wind power)is of great significance in China.This paper summarizes the relevant policies,integration schemes and typical cases of the integrated development between renewable energy and other industries.First,the development status of wind and solar generation in China is introduced.Second,we summarize the relevant policies issued by the National Development and Reform Commission,National Energy Administration and other departments to promote the integrated development in photovoltaic and wind power generation in China.Third,eight kinds of photovoltaic three-dimensional development models are described,including “photovoltaic+agriculture,industry,environmental protection,transportation,architecture,communication,hydrogen and ecology”.Fourth,eight kinds of wind power threedimensional development models are summarized,including “Offshore wind power+marine ranch,marine energy,marine tourism,marine oil and gas,hydrogen,communication,Energy Island”and“Onshore wind power+courtyard”.In the future,the promotion and application of the above integrated development projects will be accelerated.This overview aims to provide reference for the design in photovoltaic and wind energy systems and help potential investors to make decisions.

1.Introduction

Energy is the necessary guarantee for human production and maintenance of life.Since the first industrial revolution,human beings have continuously increased the development and utilization of energy in order to meet the growing needs of life.Since the 21st century,the global energy security and ecological environment protection issues have become increasingly serious.The COVID-19 epidemic has seriously affected the economic and social development of countries.The release of the Sixth IPCC Assessment Report“Special Report on Global Warming of 1.5°C” in October 2018 means that the global energy structure is facing a transition.By 2050,70%-85%of global electricity supply needs to come from renewable energy sources in order to reduce industrial carbon dioxide emissions by over 75% compared to 2010 and control temperature rise within 1.5°C.To address climate change to economic recovery and long-term goals together,countries have a“green recovery”route choice,placing green economy at the core of the stimulus package,and more than 50 countries have formulated policies and regulations for renewable energy development (Oosthuizen and Inglesi-Lotz,2022).

In recent years,China's position in the field of renewable energy has become increasingly prominent,gradually becoming the leading role in promoting the transformation of global energy structure.As the“largest country in renewable energy”,the installed capacity of wind power,solar energy and other renewable energy ranks first in the world.Although China has made remarkable achievements in the development of renewable energy,the current energy structure is still dominated by fossil fuels,leading to China becoming the world's largest greenhouse gas emitter (Shen et al.,2020;Zhang and Chen,2022).According to the“Three Step” route of the “Carbon Neutrality” goal,the proportion of non-fossil energy consumption in China will continue to rise in 2025,2030 and 2060,eventually reaching more than 80%.In order to effectively advance and achieve the “Carbon Emission Peak and Carbon Neutralization” target and inject new momentum into the high-quality development of China's economy,the large-scale development of renewable energy is imminent (Wang et al.,2020;Meng et al.,2022).

China's new power system with renewable energy as the main part is accelerating construction.Renewable energy with photovoltaic and wind power as the main body has entered a new development stage.Its development trend and relevant policy guidance have also brought new development changes,which has brought new opportunities and challenges to the design and development of power stations.The construction of renewable energy power stations should be diversified,comprehensive,innovative and integrated.The application of“renewable energy+”should be developed in combination with multiple scenarios such as ecology,agriculture and desert restoration.That will become the key direction of renewable energy development in the future.

This study is organized as follows: Section 2 describes the development status of wind and solar generation in China.Section 3 provides the policies of integrated development in solar and wind energy systems.Section 4 summarizes the integrated (Three-dimensional) development models in solar and wind energy systems.Finally,Section 5 prospects the future development trends and suggests paths for future research.

2.Development status of wind and solar generation

During the 12th Five Year Plan for Economic and Social Development of the People's Republic of China (12th Five-Year Plan) period,the combined annual power generation of wind and photovoltaic(PV)power in China accounted for less than 4%,annual growth of about 0.6%(Fig.1).

Fig.1. Wind and Solar PV generation in China over 2012-2021 (data from National Energy Administration).

During the 13th Five-Year Plan period,China's energy structure continued to be optimized,and remarkable achievements were made in low-carbon transformation.The proportion of non-fossil energy consumption reached 15.9%,while the proportion of coal consumption dropped to 56.8%.The installed capacity of non-fossil energy power generation ranked first in the world,with the installed capacity of wind and solar power generation reaching 280 GW (kW) and 250 GW respectively (National Development and Reform Commission,2022a).The maximum single capacity of onshore and offshore wind power continues to increase,the diameter of wind turbines continues to grow,and breakthroughs in key core technologies continue to be made.Photovoltaic power generation in efficiency,capacity,technical level and other aspects continue to maintain an international leading position(China Electricity Council,2021).During the 13th Five-Year Plan period,China's wind&PV annual power generation accounted for 5%-10%;and growing at about 1 percentage point per year.

In 2021(the first year of the 14th Five-Year Plan),the newly installed capacity of wind and PV power generation in China reach 101 GW,including 47.57 GW of wind power and 54.88 GW of PV power.According to the statistics of the National Energy Administration,the distributed installed capacity is about 29.28 GW in China's new PV installed capacity,accounting for 53.4% of all new installed capacity.Provinces with relatively large new installed capacity included Shandong(4.75 GW),Hebei(3.63 GW)and Anhui(1.96 GW)(Wang et al.,2022).In 2021,onshore wind power added 30.67 GW and offshore wind power added 16.9 GW.Provinces and regions with large new installed capacity included Jiangsu (5.02 GW),Guangdong (4.69 GW),and Henan(3.22 GW).By the end of 2021,the grid-connected wind and PV power installed capacity reached 328 GW and 306 GW respectively.The annual cumulative power generation of wind and PV power reached 978.5 billion kWh,up 35% year-on-year,accounting for 11.7% of the total power generation,an increase of 2.2 percentage point over the previous year(Fig.1).

3.Policies of integrated development in solar and wind power generation

Innovation and integration is the key direction for the future development of renewable energy power stations.The first is the integration between power stations and development sites,the second is the technical integration between energy development and utilization,and the third is the integration of industrial development (Ye,2021).Countries around the world continue to deepen the layout of PV power industry chain innovation,as a major strategic measure to promote the development of emerging industries.Photovoltaic applications are developing towards multi-use scenarios.Countries around the world,according to their own actual conditions,actively promote the development of PV building integration,floating PV,PV agriculture,PV carport and other new application forms.

For example,the United States encourages rooftop PV through tax incentives,loan guarantees and other policies(Borenstein,2017;Leibowicz et al.,2019;Wolske,2020).In terms of solving the consumption problem,the United States encourages residents to use their own electricity spontaneously.When residents install PV power equipment in their homes,if there is still surplus electricity after deducting electricity consumption,they can transfer the electricity to the next month for self-use.Encouraged by such a self-use policy,the problem of grid connection consumption has been solved,and the cost of large-scale construction of high-voltage power grid has been saved.According to the U.S.Energy Information Administration(EIA),the installed capacity of new residential roof PV in the US in 2021 reached 4.3 GW,an increase of 29%.California was the largest market for rooftop PV in the US last year (2020),accounting for about 1/3 of all new installations.In addition,the U.S.Department of Energy announced a new "National Community Solar Partnership",which aims to have community solar projects deliver 26 GW of power and generate$1 billion in revenue by 2025.The total installed capacity will reach 30 GW by 2030.

Road PV is a new application mode,providing deep integration between transportation and renewable energy industry (Dezfooli et al.,2017;Liu and Fei,2021).According to the report of Japan economic news on October 14,2021,Japan is involved in the business of laying PV panels on roads to generate electricity.Japan's East Asian road industry will cooperate with Colas,a large French road construction enterprise,to develop technology.Colas'PV power generation laying system can install panels with width of 0.69 m,length of 1.25 m and thickness of 6 cm on the pavement,and can be used on driveways and sidewalks.Colas has introduced the system in about 10 countries around the world,including Canada and the United Arab Emirates.East Asia Road Industry plans to introduce the system in Japan as well.The East Asia Road Industry is negotiating with some Japanese local governments to set up parking lots,parks and walking trails from 2023.East Asia Road Industry will cooperate with Colas to develop materials that can also fix PV panels on the road under high temperature and humidity.

Germany's sustained stability policy facilitates rooftop PV.Germany's new Renewable Energy Law(EGG)aims to increase solar PV capacity to 100 GW (up from 52 GW at present).EGG also promotes “user-rent”schemes,in which German homeowners install solar panels on their roofs and charge for Internet access.However,tenants cannot participate.EGG uses business tax reductions to encourage landlords to install PV rooftop solar panels for tenants.In renewable energy consumption,Germany has done a better job.Against the background of large installed capacity,the abandoned light rate in Germany is only about 1%,and there are two main reasons for such a high absorption rate.One is that Germany is keen to keep the growth of installed capacity in step with the construction of the power grid.Among the policies to encourage wind and PV power generation,the most important is the fixed feed-in tariff.High subsidies and the guarantee of full Internet access have attracted large amounts of capital,which has greatly stimulated the rapid growth of installed wind and PV capacity.

Western countries are leading the world in the integrated development in solar and wind energy systems.Compared with Western countries,China has gaps in policy objectives,legislative system and incentive means,which need to be further improved.However,under the early guidance of the policies,China's solar and wind energy industries have quickly formed scale advantages and supply chain advantages.Overall,China belongs to the country with abundant solar energy resources,with two-thirds of the country's regions having an annual radiation level of over 5,000 MJ/m2.China is also a country with abundant wind energy resources.There are great regional differences in solar energy resources in China(Jing et al.,2023).Solar energy resources in plateau areas and dry areas with little rain are larger,while those in plain areas and rainy areas with high humidity are smaller(Yao et al.,2022).Regions with the most abundant wind energy in China are mainly distributed in the“Three North”regions,namely northeast,northern North and northwest China,followed by coastal areas(Zhu et al.,2021).

China has recently released intensive policies related to wind and solar energy industry.From the end of 2021,the National Development and Reform Commission issued the “Revitalization and development plan for special types of regions during the 14th Five-Year Plan”,and then successively issued the “Implementation opinions on accelerating the transformation and development of rural energy and helping rural revitalization”,the “Modern energy system planning for the 14th Five-Year Plan”,“Guidance on energy work in 2022”,“Implementation plan for promoting high-quality development of new energy in the new era”and the“Renewable energy development plan during the14th Five-Year Plan”in 2022(see Table 1 for more details).It can be seen that wind and PV power have become the main force supporting the development of renewable energy.In terms of wind and PV power development modes:centralized and decentralized development,land and sea development,nearby and external development,multi-energy complementation,single and multi-scene development will be the direction of the future.

Table 1 Relevant policies for integrated development in solar and wind energy systems in China.

Up to now,many provinces have issued the“14th Five-Year Plan”for renewable energy development.For example,(1) Shandong Province promotes the “integrated base of scenery and storage in saline alkali Beach” and the “PV +” base in coal mining subsidence area (Energy Administration of Shandong Province,2022;Shandong Development and Reform Commission et al.,2022).(2)Jiangsu Province promotes the application of distributed wind power and distributed PV (Energy Administration of Jiangsu Province,2021).(3) Guangdong Province promotes the integrated construction of PV buildings and multi-field and multi-scene application in areas such as transportation,communication and data centers (People's Government of Guangdong Province,2022).(4)Fujian Province promotes the development of new energy application modes and new business forms,such as"PV+",micro grid,integration of wind,solar energy and storage,and smart energy(People's Government of Fujian Province,2021).(5) Zhejiang Province actively develops multi-energy complementary demonstration projects combining wind,solar and other energy sources (Zhejiang Development and Reform Commission and Energy Administration of Zhejiang Province,2021).(6)Henan Province promotes the establishment of "PV +" bases in coal mining subsidence areas,rocky desertification,oil well and mine wasteland(People's Government of Henan Province,2022).(7)The Inner Mongolia Autonomous Region has accelerated the distributed development of wind and PV power (Energy Administration of Inner Mongolia Autonomous Region,2022).(8) Qinghai Province promotes the large-scale development of PV and wind power base,and develops PV applications in various forms,such as agriculture,animal husbandry,forest and sand control,according to local conditions (People's Government of Qinghai Province,2022).(9) Gansu Province proposes to give priority to large-scale construction in desert,Gobi and desert areas to realize the integrated development of solar power generation,desertification control,ecological restoration and agriculture and animal husbandry(People's Government of Gansu Province,2021).

4.The models of integrated development for solar and wind power generation in China

4.1.Three-dimensional development models of solar PV generation

At present,China's PV power generation is mainly concentrated on land.Agriculture,construction,transportation,communications and other fields has become the main PV application scenarios,in the form of“PV +” power generation systems and functional integration of venues,facilities,to effectively promote various regions and trades alternative and renewable energy “Carbon Emission Peak and Carbon Neutralization” process is of great significance.In addition,more “PV +” application projects are quietly changing our lives and improving our environment,such as:PV+sand control,PV+mining area management,PV+environmental protection,PV+industry and PV+military-civilian integration.It is worth mentioning that at present,offshore PV power generation has become a globally recognized application form (Ranjbaran et al.,2019;Kumar et al.,2021).The global offshore PV potential capacity is about 4,000 GW,and the theoretical installation capacity of China's offshore PV can exceed 70 GW.Table 2 lists the main application forms of“PV+”,and some classic cases in China.The following is a brief introduction to each application forms.Fig.2 shows the schematic diagram of“PV +”industry integration modes.

Table 2 The “photovoltaic +”integration modes.

Fig.2. Schematic diagram of“PV+”integration modes,for instance.(The image source comes from online data.The websites are as follows:(a):https://www.thepa per.cn/newsDetail_forward_14 331101;(b): https://www.sohu.com/a/247304318_99 904385;(c): http://www.ycnews.cn/p/380058.html;(d): http://www.xio ngan.gov.cn/2021-04/05/c_1211098520.htm;(e): http://www.subaonet.com/2022/sztw/0523/505918.shtml;(f): https://www.sohu.com/a/393671861_ 162522;(g): http://www.nengyuanjie.net/article/72662.html (h): https://www.sohu.com/a/622139452_752796.).

Photovoltaic agriculture is a new type of agriculture that widely applies the solar power generation technology to fields of modern agricultural planting,irrigation,pest control and agricultural machinery power supply.Specifically,it refers to reserving the space necessary for agricultural planting and breeding in the design,construction and operation of PV power stations,so as to ensure that the normal power generation of PV power stations can meet the physiological needs of animals and plants,achieve the effect of agricultural light complementation,and realize ecological agriculture integration and innovation of circular agricultural technology model (Zhao et al.,2021).At present,there are four major modes of photovoltaic agriculture in China:photovoltaic planting,photovoltaic breeding,photovoltaic water conservancy and photovoltaic cottages(Xue,2017).

The “Photovoltaic+industry” refers to the integration of industrial and commercial plant roofs with PV applications.The power plants are built on the roof of the factory building.The enterprise can adopt the power consumption mode of“self-use,surplus power on the Internet”or“full access to the Internet”,so as to make full use of idle resources of the factory building and become the first choice for the enterprise to increase revenue and reduce expenditure(Zhao and Xie,2019).Industrial buildings are one of the main directions of"PV+"application at present due to their large single area,stable electricity consumption,high electricity price,good economy of PV installation,and mature products and models(Catalbas et al.,2021).

The “Photovoltaic+environmental protection” is mainly applied to sewage treatment.The biological pool of the sewage treatment plant covers a large area and is idle above.If PV modules are set above the biological pool,space resources can be effectively used without occupying land area.At the same time,the PV power generation system can effectively reduce the operation cost of the sewage treatment plant and provide green power energy for the plant (Ricky et al.,2019).In April 2020,the“Guidelines on improving policies related to sewage treatment charging mechanism in the Yangtze River Economic Belt” was issued(National Development and Reform Commission et al.,2020),encouraging sewage treatment enterprises to comprehensively utilize site space and construct PV power generation projects in the mode of“self-use and surplus Internet access”.In 2021,the Energy Administration of Zhejiang Province (2021) officially issued the first provincial implementation guidelines for promoting the pilot work of distributed PV development in the whole county,which clearly pointed out that the proportion of PV installation of existing sewage plants and water plants is required to be more than 90%,becoming one of the key work of distributed PV development.

There are a lot of land and space resources available along the slopes of highways,station facilities,high-speed railway,service areas,gas stations and other areas,which have favorable conditions for the distributed development and nearby utilization of renewable energy such as “PV +”.The specific performance of photovoltaic transportation is“PV+transportation infrastructure” and “PV+vehicles” (Osˊorio et al.,2021;Chen et al.,2022;Ren et al.,2022).Specifically,“PV+transportation infrastructure” includes “PV+sound barrier”,“PV+airport,port”,“PV+high-speed railway station,subway station,high-speed service area”,“PV+car charging pile” and “PV+carport”.The “PV +vehicles” include “PV+roof (PV panoramic roof)”,“PV+express tricycles”,“PV+refrigerated vehicles” and “PV+saloon cars”.In recent years,photovoltaic bus stations,photovoltaic gas stations,road slope protection PV power stations have also emerged in large numbers,and photovoltaic floor tiles,photovoltaic roads and other exploratory applications.

The distributed PV system on the building has two forms: installed photovoltaic power station(BAPV)and building integrated photovoltaic(BIPV).The most widely used roof PV power station belongs to BAPV system;BIPV system integrates the technology of solar PV module power generation products into the building and becomes a part of the building,such as photovoltaic curtain wall,photovoltaic sun visor and photovoltaic roof that directly replaces the color steel tile roof(Shukla et al.,2016;Ghosh,2020).The development of photovoltaic technology promotes the integration of photovoltaic architecture into a new form of solar energy application architecture.Since 2009,China has been promoting the application of solar energy in the field of construction,implementing the“Golden Sun Project”to provide financial subsidies for rooftop PV power generation projects.Since 2014,solar architecture has been vigorously promoted as one of the important ways of targeted poverty alleviation.The BIPV represents the development trend of green building and has become the direction of strong policy support.

With the expansion of communication service coverage and the updating of communication technology in China,the situation of inconvenient power supply of communication base station in remote areas and the sharp increase of power consumption of the base station equipment is becoming more and more prominent.The“Photovoltaic+communication” can support distributed PV power stations for communication base stations,realize local power supply,and solve the problems of power consumption of base stations in areas without power and areas with unstable urban power grid supply.Solar communication base station is based on PV power generation technology to power the communication base station,has advantages of safety and reliability,no noise and other pollution,simple installation,low operation cost and can be applied to a wide range of advantages (Ma et al.,2021;Botero-Valencia et al.,2022).

According to the latest “World Energy Outlook (2022 Edition)”released by British Oil Company (BP): by 2050,the proportion of hydrogen energy in total terminal energy consumption will increase by 16%,in which hydrogen production from electrolytic water will become the main source of hydrogen supply.According to the“White paper”issued by China Hydrogen Energy Alliance (2019),by 2050,hydrogen production from renewable energy electrolysis will account for 70%of the hydrogen supply structure in China.In the photovoltaic hydrogen production mode,“green electricity” produced by PV is an important raw material for the production of“green hydrogen”by means of water electrolysis.It has the special advantages of suppressing the instability of PV power generation and improving the utility of energy storage,creating new application scenarios and broad market demands for PV power generation(Fereidooni et al.,2018;Chatterjee et al.,2022).According to media statistics,most of the 13 largest green hydrogen energy projects being developed worldwide are photovoltaic hydrogen production,with a total investment of more than US$100 billion and a staggering 61 GW.

Photovoltaic ecology is to use abandoned barren hills and barren slopes,salt and alkali beaches,abandoned coal mining areas,mining subsidence areas and other idle land to develop ecological photovoltaic,build photovoltaic power stations,or build tourism areas through integrated development mode,to achieve double harvest of environmental protection and economic benefits.This includes “PV+sand control”,“PV+industrial and mining waste land management”,"PV+mining subsidence area management" and other specific forms.In addition to recycling wasteland,this model can also achieve ecological governance and restoration,which can better realize ecological sustainable development.Among them,“PV+sand control” is a new achievement explored in the past decade(Chang et al.,2018;He,2022).The PV power station is surrounded by “grass grid” sand barriers and sand-fixation forest to form a protection system.Water-saving drip irrigation facilities are installed below the PV panels,and green economy is planted to achieve win-win economic and ecological benefits.

4.2.Three-dimensional development models of wind power

Due to the scarcity of three-dimensional application models for onshore wind power,this section mainly introduces the application models of offshore wind power.

According to World Bank statistics,the development potential of offshore wind power technology in 115 coastal countries or regions around the world has reached 71 billion KW,and the theoretical annual power generation has reached 213 trillion KWH,of which only 11%needs to be developed to meet the world's power demand.China has the natural advantage of developing offshore wind power,with a coastline of 18,000 km and a useable sea area of more than 3 million square kilometers,and abundant offshore wind energy resources.In 2021,the cumulative installed capacity of offshore wind power was 26.39 GW,with 16.9 GW newly installed(Chen,2011;Liu et al.,2021).As a key field of renewable energy in China,offshore wind power will enter a new development period during the 14th Five-Year Plan period,and its development will enter a new stage.

Integrating the construction of offshore wind power with other marine development activities,strengthening intensive and economical use of the sea and realizing three-dimensional development is the inevitable choice for high-quality development of offshore wind power.The integrated development of offshore wind power is mainly concentrated in marine fishery(marine ranch),other marine energy,tourism,marine oil and gas industry,seawater hydrogen production,energy island construction,marine chemical industry,marine engineering construction,marine salt industry,marine biological medicine,marine shipbuilding industry,marine mining,seawater desalination and construction of marine comprehensive test site.It is conducive to promoting the full use of three-dimensional space in the sea area,and is an important development direction of offshore wind power in the future.Table 3 lists the main application forms of “offshore wind power +”,and some classic cases around the world.The following is a brief introduction to each application forms.Fig.3 shows the schematic diagram of “wind power +” industry integration modes.

Table 3 “Offshore wind power +” integration modes.

Fig.3. Schematic diagram of“Offshore wind power+”integration modes,for instance(The image source comes from online data.The websites are as follows:(a):htt ps://www.163.com/dy/article/GKHP7O540511KMS0.html;(b): https://baijiahao.baidu.com/s?id=1749540563345402121&wfr=spider&for=pc;(c): https://www.sciencedirect.com/science/article/pii/S2214629620 303017;(d): http://news.sohu.com/a/536080492_121124367.).Note: Photos of the project under construction cannot be provided.

The integrated development mode of offshore wind power and marine ranch not only produces clean energy,but also provides a good habitat and shelter for organisms,and carries out wind power generation and underwater aquaculture of fish,mussels and coral reefs.Europe has already carried out “offshore wind power+marine ranch”demonstration projects,such as the EU-backed MARIBE (Marine Investment for the Blue Economy) project.The bidding for Borssele offshore wind farm in the Netherlands includes a variety of offshore options.In 2016,South Korea launched a combined project of offshore wind power and mariculture.In January 2019,the “Comprehensive pilot program for the construction of modern marine pasture in Shandong province”(People's Government of Shandong Province,2019)was issued,which proposed to explore the integrated development of marine ranch and offshore wind power.In August 2019,Shandong Province launched the first “offshore wind power+marine Ranch”demonstration project in China,known as the "Changyi marine ranch and Three Gorges 300 MW offshore wind power integration experimental demonstration project”,with a total investment of 5.13 billion yuan($766 Million).In addition,according to the“14th Five-Year Plan”period,the development of 20 GW of offshore wind power and marine ranch integration projects can drive the output value of marine fisheries to increase by about 50 billion yuan ($7.46 billion).In the future,long-distance offshore development of offshore wind power and the combination of marine ranching and intelligent cage will improve the economic benefits of wind farms to a certain extent.

Tidal,wave,ocean thermal,salinity gradient and other marine energies have broad development prospects.However,the development cost of single energy is high,and it is less economical than conventional energy,which is not conducive to commercial promotion(Li et al.,2022).Therefore,the comprehensive utilization of marine energy is imperative.Combining the distribution characteristics of wind energy and marine energy resources,using offshore wind energy to drive the development of wave energy and tidal energy,to realize the purpose of complementary advantages and comprehensive utilization (Bhattacharya et al.,2021;Robertson et al.,2021;Patel et al.,2022).Its comprehensive development modes can be divided into: (1) shallow combination: shared sea area,joint construction,overall delivery,shared operation and maintenance,reducing the construction cost of marine energy,which can be realized in the near future;(2) Deep integration: Coupling design,synchronous construction.In the future,when the technology is mature,the cost will be further reduced and the quality of offshore power generation will be improved.

Marine tourism is one of the biggest industries of marine economy in the world and the pillar industry of marine economy in China.At present,the tourism industry is mainly offshore,including marine tourism industrial park,marine theme park,coastal tourism resort and other modes.The integrated development of offshore wind power and tourism is mainly aimed at enhancing public awareness of offshore wind power and promoting the integration of offshore wind power and tourism provinces (Smythe et al.,2020).In the future,with the construction of large-scale offshore tourism platform,it will have great potential for integrated development.

Offshore wind power construction,installation,operation and maintenance equipment are consistent with the marine oil and gas industry.In general,long-distance offshore wind power and marine oil and gas industry have a large space for integrated development.Using offshore wind turbines for power generation and configuring energy storage equipment can transmit power to the newly planned platform,meet the power demand of the platform and reduce the energy cost(Zhang et al.,2021).The use of floating wind turbines can be integrated with the long-distance offshore oil and gas resources and drive the development of long-distance offshore oil and gas resources.France is exploring the comprehensive utilization of floating offshore wind power,wave energy,hydrogen energy and other energy sources to supply power for offshore oil and gas platforms.

Hydrogen energy is clean energy with great potential for development.Increased numbers of countries have placed Hydrogen energy into the national energy strategy.In China,the integration of offshore wind power and hydrogen energy is the main direction of future development as offshore wind power is developing in a concentrated and large-scale way in the long-distance offshore region.Hydrogen production can be realized directly on the side of wind turbines by transforming existing oil and gas platforms into hydrogen production platforms or building electrolytic cells inside wind turbines or floating platforms (Apostolou and Enevoldsen,2019;Luo et al.,2022).The total scale of announced reserves of electrolytic water hydrogen production projects worldwide is 32 GW,about half of which comes from offshore wind power (Li and Yuan,2022).Overseas offshore wind power hydrogen production projects are mainly concentrated in Europe.

Driven by the rapid development of the marine industry,the demand of network coverage in offshore areas is becoming increasingly urgent.The offshore base station can not only effectively guarantee the construction and operation of offshore wind power,but also provide mobile communication services for the personnel of offshore wind power engineering units,passing ships and fishermen working in surrounding waters(Zhou et al.,2020).Similar to“PV+communication”,offshore wind power can be used to solve problems such as electricity consumption of offshore communication base stations.

The early definition of an energy island is“a natural island or artificial platform that acts as a hub for the generation of electricity from the surrounding offshore wind farms and transmits it to countries in the North Sea region”.It is a diversified marine utilization system built around offshore wind power.The energy island can be used to create a comprehensive development model of offshore“energy island”resources that integrates various energy sources such as wind,hydrogen,offshore PV,seawater desalination and energy storage (Jansen et al.,2022;Tosatto et al.,2022).In 2017,European transmission system operator-TenneT put forward the idea of building an energy island on the Doge coast-the Consortium North Sea Wind Power Hub,which is mainly used for access to the international development of offshore wind.The project initially planned to build three islands,each covering an area of about 6 square kilometers,with ports,airports and other transportation facilities.Up to now,the Consortium North Sea Wind Hub is the earliest and most well designed energy island project,which is expected to be completed between 2030 and 2050.In China,on August 2020,the leading group office for comprehensively deepening reform and opening up in Hainan issued the comprehensive energy reform plan for Hainan (People's Government of Hainan Province,2020),proposing to build a clean energy island in Hainan.By 2025,Hainan clean energy island will begin to take shape.

There are few models for integrated development of onshore wind power,and courtyard wind power is the main mode at present.Wind power agriculture in the United States started from the courtyard(National Energy Administration,2005).Its characteristic is that the wind power or solar energy equipment installed in these users' homes“feedback” the electricity to the grid when the electricity is surplus.To encourage customers to build wind power plants,many states in the United States have adopted the “power swap” method.That is,power enterprises and users can supply power to each other and offset each other's power supply and consumption.In China,on October 2021,118 cities and more than 600 wind power enterprises jointly launched the “Wind Power Partnership Action Zero Carbon City and Rich Beautiful Village” plan.The plan specifies that during the “14th Five-Year Plan” period,10,000 wind turbines will be installed in 100 counties and 5,000 villages,with a total installed capacity of 50 GW.

5.Conclusions

There is a broad space for integrated development between various industries and renewable energy (photovoltaic,wind power).It is not only conducive to the further development of renewable energy,but also conducive to promoting the low-carbon transformation of energy in various industries,so as to jointly contribute to the realization of the“Carbon Emission Peak and Carbon Neutralization” target.This paper summarizes the relevant policies,integration schemes and typical cases of the integrated development between renewable energy and various industries.

First,during the “14th Five-Year Plan” period,the domestic photovoltaic and wind power industry will maintain large-scale,high-proportion,market-oriented,high-quality direction of development.Second,the National Development Reform Commission,the National Energy Administration and other departments have issued many relevant policies to promote the integrated development in photovoltaic and wind energy systems,mainly including the following points:ecological restoration,rural revitalization,large-scale construction in desert and Gobi areas,integrated application with building and transportation and hydrogen production demonstration.Third,the main PV application scenarios are described,including: PV+agriculture,PV+industry,PV+environmental protection,PV+transportation,PV+architecture,PV+communication,PV+hydrogen,PV+ecology.Fourth,the main wind power application scenarios are discussed,including: Offshore wind power+marine ranch,Offshore wind power+marine energy,Offshore wind power+marine tourism,Offshore wind power+marine oil and gas,Offshore wind power+hydrogen,Offshore wind power +communication,Offshore wind power+energy island and Onshore wind power+courtyard.In the future,the promotion and application of the above integrated development projects will be accelerated.

Suggestions for the future: strengthen policy guarantee,form demonstration effect,and accumulate experience in existing projects.The industrial technology level,industrial system and supporting environment need to be continuously improved.The impact of renewable energy integrated development modes on local climate and environment(especially ecological fragile areas) need to be observed,simulated,evaluated and planned in advance.

Acknowledgements

This work is financially supported by the National Key R&D Program of China (2018YFB1502800),National Natural Science Foundation of China (No.42330601) and the CREEI (ZY-KJHB-20220005).We thank Wuhan Library,Chinese Academy of Sciences for providing some information.