In 2008, China’s wind power started to grow rapidly, marked by the approval of a 10,000 MW wind power base in Jiuquan, Gansu Province, opening a new chapter of the new energy construction of China [1
]. Since then China’s installed capacity of wind power continued to rise, showing a “blowout” situation with construction of eight 10,000 MW-class new energy bases being approved, forming a mode of large-scale, concentrated development and long-distance transmission [2
]. The total installed capacity of wind power connected to the grid was 148,640 MW in 2016, which is 16.7 times that of 2008 [3
] (Figure 1
), creating a miracle in the history of the new energy development of the world. While making great achievements, China saw a growing problem of wind curtailment [4
]. It has become a focus of the whole society on how to improve the new energy utilization rate and reduce the electricity being curtailed.
The electricity system simultaneously realizes power generation, supply and consumption and the electricity load shows obvious time-variant characteristics. The peak-valley difference of the power grid in northwest China has exceeded 30%, and shows a growing trend. A basic condition for the electricity system to run steadily is that the system adjustment capacity must be higher than load fluctuation [5
]. Because of the characteristics of wind and solar energy as resources, the output of new energy features randomness and fluctuation. The daily fluctuation of the wind power can be as high as 80% of the installed capacity, and shows some features of anti-peak load adjustment. When the new energy such as wind power is connected to the electricity system at a high proportion, the burden of electricity system is increased. The conventional power sources not only need to change with the load changes, but also need to balance the output fluctuation [6
]. When the wind power output exceeds the system adjustment scope, efforts must be made to control the output so as to realize the system dynamic balance, resulting in wind curtailment.
China’s wind curtailment is characterized by imbalance of regional development of wind power [7
]. The contrary distribution of the wind resource and load and the large-scale concentrated development make China a country with the highest access voltage and the longest transmission distance of wind power [8
]. China’s wind power is mainly distributed in northwest China, North China and Northeast China which enjoy rich wind resources and account for more than two thirds of the total installed capacity of China [3
]. Different from Germany, Spain and Denmark that feature dispersed distribution and local consumption of wind power, China normally transmits the wind power through the high voltage line to a long distance. The wind power base of Jiuquan transmits the surplus wind power to the load center 1000 km away; the wind power base of Inner Mongolia also transmits the wind power to consumers more than 250 km away [7
]. Provinces in western and northern China that enjoy abundant wind resources are far from the electricity consumers in eastern China, resulting in the high rate of wind curtailment. It is noteworthy that the wind curtailment rate has remained high in northwest China (Figure 2
) that accounts for almost a half of China’s total (the northwest China accounted for 49% and 48% of China’s wind curtailment in 2015 and 2016, respectively).
After the wind power is connected to the electricity system at a large scale, it brings non-negligible impacts on the stability, voltage, electricity quality and system backup of the electricity system because of fluctuation, randomness and intermittency of the wind power output [6
]. However, the electricity system has to limit the wind power output to ensure safe and stable operation and balance of quantities of electricity to meet the requirements of peak load adjustment, voltage control, economic dispatching and frequency modulation and other tasks. However problems have been properly managed in the United States and Europe where renewable energy has developed well. The United States and Europe have developed wind power for nearly 20 years and taken a leading role in the technology, operation management and electricity market of the world [3
]. Take Europe for example, that its wind power has developed rapidly can mainly be attributed to constant improvement of wind power control technology, rational planning and support and guidance of the electricity market. In 2012, the installed capacity of Denmark and Germany reached 40% and 15% and the wind power output accounted for 22% and 10%, respectively [3
]. The reason that Europe can maintain the relative high access of wind power is because that the oil-fired generators, gas-fired generators and pumped storage account for a high proportion in the power source, and a robust 400 KV grid serves as an effective support of the wind power transmission in Europe. Moreover, European countries not only are obliged to accept all provisions on wind power, but also set forth strict technical requirements on the technology and norms of wind power grid connection, wind turbine performance and wind farm management.
The most common explanation of the imbalanced development of wind power among different regions in China is distribution of wind resources. China boasts rich wind resource and the available potential wind energy exceeds 5500 GW (gigawatt) [9
], but distributed quite unevenly among different regions. According to the research of He and Kammen of China’s wind resource and wind power development potential [10
], the potential of wind power development varies remarkably from province to province from less than 1 GW to more than 600 GW. However, the distribution difference of the wind resource could not perfectly explain the huge regional differences of the wind power development that the wind resource utilization rate varies from less than 1% to 90% from province to province. Even in provinces with similar wind resource, the installed capacity varies highly.
Another even more perplexing question is why installed capacity has been increased rapidly while the region with rich wind resource has so serious wind curtailment since 2009. Take northwest China for example, the total installed capacity of wind power increased from 16,260 MW in 2013 to 43,290 MW in 2016, up 266%. Meanwhile, the wind curtailment became even more serious, worsening the regional imbalance of the wind power development.
In 2010 China saw obvious wind curtailment and with rapid development of wind power, the electricity rationing became even more prominent. That year the newly increased installed capacity of wind power was 18,900 MW, the accumulative installed capacity ranked the world’s first, and the total rationed electricity reached 3943 GWh, reaching 10% [7
]. In 2011, the rationed wind power in China exceeded 10,000 GWh. Large-scale wind curtailment became frequent and normalized in northeast and northwest China. The rationed electricity of Gansu, Inner Mongolia, Jilin and Heilongjiang reached 5304 GWh, accounting for 50% of China’s total; and the national electricity rationing reached 14.5% [7
]. The year 2012 saw the most serious wind curtailment in history and the total rationed wind power hit 20,800 GWh, more than two times of that in 2011, accounting for 14.7% of the total wind power output of the year, the highest in history [7
]. In 2013, the wind curtailment rate started to decrease with concerted efforts of the government departments, grid companies and the wind power industry, and the rationed electricity reduced to 16,200 GWh, down 4600 GWh, the proportion of rationed electricity was reduced to 10.5%, down 6.2 percentage points year-on-year. However, that did not mean the wind curtailment phenomena was bettered because the big wind power provinces still had high wind curtailment rate and Jilin and Gansu provinces still faced more than 20% rationed electricity [7
]. In 2014, the wind curtailment was obviously improved because of the generally lower wind force, and the rationed electricity was 12,600 GWh, and the average wind curtailment rate was 7.3%, the lowest in recent years. The whole country, except Xinjiang, saw decreased wind curtailment rate to different extents, but the wind curtailment rate of northeast China, north China and northwest China was still relatively high, for example the rationed electricity of Xinjiang and Jilin reached 15%. In the first half of 2015, the wind curtailment rebounded obviously and 17,500 GWh of wind power was curtailed, an increase of 10,100 GWh; and the average wind curtailment rate reached 15.2%, up 6.8 percentage points year-on-year. It was even more serious in some areas. For example in the six big wind power provinces, namely Jilin, Gansu, Xinjiang, Heilongjiang, Inner Mongolia and Liaoning, the proportion of rationed electricity reached nearly or exceeded 20%, and Jilin Province saw the highest, as high as 43%. In the second half of 2015, the electricity rationing worsened in Gansu and Xinjiang etc. From July to October, the electricity rationing reached more than 50% monthly, unprecedentedly serious. In 2015, more than 33,900 GWh of wind power was curtailed, and the wind curtailment rate exceeded 15%, creating a new high in history [3
]. The losses caused by wind curtailment almost offset the newly increased installed capacity in 2015.
In years between 2011 and 2015, China was the world’s largest wind power market, but faced increasingly serious wind curtailment. According to the data of the National Energy Administration, the average use time of wind power was 1724 h, a new lowest in the five years (2011–2015). In 2015, 33,900 GWh of wind power was curtailed, an increase of 21,300 GWh year-on-year, and the average wind curtailment was 15%. In 2016, the average wind curtailment was 17.1% [3
] (Figure 3
), the highest since 2013 when the large-scale wind curtailment appeared for the first time. Gansu ranked first of all provinces with as high as 43% of the wind curtailment rate while Xinjiang’s was 20%. The wind curtailment rate remained high and showed an intensified trend. With growing grid-connected installed capacity, the wind curtailment in 2016 reached a new high in history with as high as 49,700 GWh of wind power being curtailed, an increase of 15,800 GWh compared with that in 2015, and almost four times of that in 2014. The curtailment resulted in as high as RMB 27 billion of electricity charge losses, equaling to nearly 16 million tons of standard coal equivalent [3
]. Compared with the world’s typical wind power countries that enjoy below 3% of the wind curtailment rate, northwest China’s wind curtailment was strikingly high [11
The high wind curtailment may result in a huge waste of renewable energy resources and power generation enterprises in losses, and seriously upset enterprises’ investment enthusiasm. Consequently, the capital market started to upturn the risk assessment level of the wind power and PV industry. If the wind curtailment could not be solved as soon as possible, the renewable energy industry will fall into a vicious circle; the renewable energy development goals set in the 15th Five-Year Plan could not be realized, and the 2030 emission reduction goals and energy structure adjustment plan undertaken at the Paris Climate Change Conference will come to nothing [12
Most of the studies on curtailing wind power in China are statements of common sense or obvious views. Some studies explore the impact of a certain factor on the development of wind power. For example, Zhang have discussed whether enlarging the outward transmission of wind power can solve the problem of curtailment of wind power [14
]. It can be seen as another perspective to analyze whether the difficulties of outward transmission of wind power are the main reason for wind curtailment. Wei studied the role of local governments on the development of wind power, relevant laws and regulations in China [15
]. A small number of empirical studies only analyzed some specific factors that affect wind curtailment from one aspect. Liu analyzed the impact of wind power integration on the existing power grid [16
]. Zhang et al. analyzed the average annual government revenue and tax increase for 10,000 yuan of investment in thermal power or wind power of two typical districts based on the input–output method and concluded that thermal power generation has obvious advantages over wind power generation [17
]. A large number of studies have subjectivity, one-sidedness and superficiality. In addition, they seem not like scientific papers for lack of necessary data analysis, which means further researches are needed. Therefore, it is impossible to figure out the main causes for wind curtailment. Thus these studies’ contributions on how to solve the problem are limited. This paper attempts to construct a genesis analysis model, carry out a comprehensive analysis of the causes of wind curtailment, and use data analysis/case and scenario analysis method to clearly verify the model.
This paper aims at exploring why northwest China faced a large amount of wind curtailment and why the wind curtailment rate has remained high. Northwest China herein includes Gansu Province, Xinjiang Uygur Autonomous Region, Ningxia Hui Autonomous Region, Qinghai Province and Shaanxi Province. This paper mainly analyzes the first three provinces (autonomous regions) as Qinghai and Shaanxi has lower wind curtailment.
2. Analytical Model
Studies on the wind power operation and accommodation have different focuses and methods; some focus on the grid planning, construction and operation system analysis [18
]; some center on the electricity market operation [23
]; some discuss the coordination relationship between wind power characteristics and the electricity system [8
]; some explain the flexibility of the electricity system [28
]. Specifically, Pei et al. conducted an in-depth analysis of the operational characteristics and market consumption of China’s wind power, pointing out that the mismatch between supply structure of domestic power and wind power development as well as insufficient capacity of cross-regional power transmission are the main reasons for low China’s wind power consumption. Some researchers had studied the challenges of power grid brought by wind power integration and intended to design proposals to solve the problem. For example, the researches on the coordinated operation mode of combined heat and power generation, the combined operation strategy of peak power supply and intermittent power supply based on power grid security economy and the optimization of the operation and the market have the guidance meaning for policy making, which will help to ease the current tension of wind power consumption.
In addition to the qualitative analysis method, model demonstration and case study are used in the studies [31
]. All these studies provide important inspirations for the establishment of the analytical framework and research of the paper.
From the aspect of the development process of renewable energy of the globe, only China is facing the large-scale wind power grid connection accommodation constraints in a large scope [3
]. Compared with the United States and Europe, China faces many practical obstacles and challenges for the wind power accommodation.
First, China’s electricity operation still follows the mode of planned economy. China’s existing dispatching arrangement, from both the power generation side and the power consumption side, still adopts the management mode with characteristics of planned economy and flexible resources are lack of enthusiasm to voluntarily participate in the system balance adjustment. With regard to the electricity operation, though the Renewable Energy Law of China stipulates to implement the system of guaranteeing the purchasing of electricity generated by using renewable energy resources in full amount and power grid companies shall purchase in full amount the on-grid electricity of the grid-connected power generation projects which meet the grid connection technical standards in the coverage area of their power grids, the provisions that renewable energy resources shall be given priority and the full amount power grid connection are far from implemented.
Second, the cross-province electricity trading and transmission face obstacles. China has long been promoting construction of the electricity industry and the power market with province as an entity. Though in the past 30 years such practice has stimulated investment in the electricity industry and guaranteed power supply, the administrative provinces as executor of the planned economy of electricity industry have also hindered the cross-province electricity trading. The provincial electricity market led by the provincial government is characterized by the self-contained system and self-balance, making the relatively closed provincial market not conducive to optimizing the national electricity system planning, power source structure adjustment, the cross-province power grid operation, electricity trading, auxiliary services or renewable energy accommodation.
Third, there is a lack of a mechanism for demand-side response and energy storage and other flexible resources to participate in the market. In northwest, north and northeast China that face difficulties in the wind power accommodation, there is no demand-side management response and incentive mechanism that is conducive to the valley wind power accommodation such as the user-side peak-valley electricity price and time-of-use electricity price.
Based on above considerations, this paper constructs an analytical model (Figure 4
) to comprehensively and systematically explore the causes of the imbalance development of wind power and worsening wind curtailment in northwest China. It includes the wind power supply capacity, electricity demand, power grid transmission capacity and electricity system flexibility and related market mechanism and laws, the four main elements impacting the wind power operation and accommodation in northwest China.