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UHV Grid: the Artery of Clean Energy

Date:2013-03-19 13:27:00 Author:hnr_admin

Reprinted from www.cec.org.cn
It is known that energy is an important material basis to support national economy and social development. The limited supply ability of traditional fossil energy and deteriorated environment are common challenges faced by all countries. Consequently, the exploration of clean energy becomes their consensus and strategic choice. Due to the uneven distribution of energy resources centers and load centers in China, the effective exploration and utilization of clean energy are influenced to a large extent. This is the main bottleneck of China’s clear energy development. However, by developing Ultra-voltage (UHV) grid, the large-scaled grid’s capacity of interregional resource allocation optimization can be fully reached, which laid a solid foundation for the development of Chinese clean energy.  
    The development of clean energy is a strategic choice for China.
    Due to current rigid growth of China’s energy demand and insufficient sustainable supply of traditional fossil energy, it is very difficult to meet the potential energy demand in the future. As a result, the development of clean energy becomes a strategic choice for China.
    All most all clean energy resources including hydro power, nuclear power, wind power, solar power, etc. have to be transformed into electricity before final utilization. In 2012, the total amount of China’s clean-energy-generated power consumption is 1.0662 trillion KWH, 21.4% of the total on-grid electricity. Among which, electricity generated from hydro power, nuclear power, wind power and solar power reached 864.1 billion KWH, 98.2 billion KWH, 100.4 billion KWH and 3.5 billion KWH respectively. By the end of 2012, China’s installed capacity of clean energy power generation exceeded 300 million KW, 28% of the total installed capacity.
    The development goal of our clean energy in the future is explicitly put forward in China’s Twelfth Five Year Plan for Energy Development. According to this plan, the installed capacity of hydro power, nuclear power, wind power and solar power should reach 290 million KW, 40 million KW, 100 million KW and 21 million KW respectively in 2015.  
    The Construction of UHV transmission channel is a necessity to promote the development of renewable energy base and new energy delivery in western and northern regions.    
    Although China’s abundant clean energy resources are mostly concentrated in western and northern areas, energy demand areas are mostly concentrated in middle and eastern regions, where the economy is more developed. Consequently, a large amount of clean-energy-generated electricity in western area should be delivered to the load centers of middle and eastern areas. Generally, the transmission distance exceeds 1000 Km, which is far beyond the economical delivery distance for 500 Kv transmission lines. As for these above-mentioned conditions, UHV grid delivery becomes a necessity to the long-distance transmission of large-scaled clean energy.   
    In accordance with clean energy development modes chose by various countries, the concentrated development and transmission of non-hydro renewable energy like wind power is becoming a mainstream trend. In the meanwhile, many countries are actively planning and studying the enlargement of electricity transmission lines to meet the future need of a high proportion of wind power, solar power, etc. integration and consumption.    
    1.Hydro power
  Resource distribution: China is abundant in hydropower resource. Technically, the exploration can reach 542 million KW, listed No.1 in the world. However, the distribution of hydropower resource is uneven -- over 80% of hydro resources are concentrated in relatively backward southwest regions like Sichuan, Yunnan and Tibet, while only 4.6% of them are located in eastern regions. 
   
    Power transmission scale: Due to the low leveled load demand in southwest region, the large-scaled hydro-electricity should be transmitted to other areas. It is predicted that the transmission scale of southwest hydro-electricity would reach 76 million KW in 2020, 22% of the total national installed capacity of hydro-electricity, and that the transmission amount of southwest hydro-electricity would reach 300 billion KWH, 25% of the total amount of China’s hydropower generation. The distance between southwest hydropower base and the load centers of middle and eastern regions is 1000-3000 Km. By constructing large-scaled UHV AC/DC transmission channels, the electricity can be transmitted in bulk to load centers of middle and eastern areas. Because large hydropower stations along downstream of Jinsha River and Yalong River are far away from the local load centers of Sichuan Province, electricity generated by these stations can be delivered by UHV DC channels. In addition, hydro-electricity generated by other stations in Sichuan Province can be transmitted after AC collection.
  2. Wind Power
  Resource Distribution: According to China’s wind resource distribution, there are rich wind resource in large-scaled wind power bases of east and west Inner Mongolia, Xinjiang Hami, Gansu Jiuquan, Hebei Bashang, Jilin, Shandong coastal area and Jiangsu offshore area, etc. The potential exploration amount of 50 meters height grade 3 or higher wind resource is about 1.91 billion KW, accounted for 80% of the national potential exploration amount.  
  Power transmission scale: It is predicted that the exploration scale of wind resource in Three North Areas of China would account for about 85% of the total national exploration amount. The principle of “provincial first, regional second, national third” is used in wind power consumption.  In northeast area, there is limited space for the expansion of wind power consumption market in regional grid of Hei Longjiang, Jilin and east Inner Mongolia, so large-scaled wind power exploration should depend on interregional transmission. In North China, apart from being consumed by the regional grid and Beijing-Tianjin-Tangshan grid, the wind power generated in west Inner Mongolia should also be transmitted to load centers of middle and eastern areas. According to preliminary analysis, the interregional transmission scale of China’s wind power would reach about 100 million KW in 2020.
  3.Solar Power
  Resource distribution: According to the distribution map of annual amount of solar radiation in China, the annual sunlight duration of desert and gobi areas in Tibetan plateau, northern Gansu, northern Ningxia and southern Xinjiang is long. The northwest region is abundant in solar energy resources, which is very suitable for large scale concentrated exploration.   
  Power transmission demand: Because photovoltaic generation bases are mainly located in remote western areas, the problem of large-scaled exploration and transmission should also be faced. Besides, solar power generation needs additional peak load regulating capacity provided by the grid. However, the capability of peak load regulation in northwest areas is insufficient. The development of UHV interregional grid is beneficial to large-scaled concentrated exploration and utilization of photovoltaic generation, as well as the coordinate development of wind, solar, hydro and thermal energy.
  Therefore, the construction of UHV grid--a high speed channel for energy transmission--can lay a solid foundation for large scaled development of clean energy and nationwide optimized resource allocation. Based on this, the construction of peak load regulating stations like pumped storage power station and LNG power station at receiving end should be accelerated, in order to ensure safe and stable grid operation after the integration of high proportion of clean energy.

    Effective consumption and utilization of clean energy rely on the UHV grid synchronized platform.
  Due to the enlargement of western and northern clean energy transmission scale, and the increasing complexity of electricity systems in North China, Central China and East China, higher requirements on receiving end’s capability of resource allocation and its function of coordinate operation platform are proposed--More coverage of receiving end grid, stronger power grid structure, higher dynamic balance ability and higher level of safety and stability are required. The UHV synchronized power grid forms strong ultra-voltage power grid structure support at receiving end, which can meet the needs of nationwide large-scaled development and effective utilization of clean energy (such as hydro power, nuclear power, wind power and solar power).     1.
    1.Hydro power
    UHV grid can enlarge the receiving end market of hydropower base. As the further development of hydro power in the southwest, it is necessary to construct strong UHV power grid at receiving ends. By interregional regulation, hydro-electricity generated in southwest area can be effectively consumed in middle and eastern areas. In the meanwhile, by enhancing the construction of inter-grid channel between southwest hydropower base and the northwest region, bulk of electricity can be handled in different seasons and at different times. As a result, the coordination between thermal power and hydro power as well as the peak load regulation can be realized in broader area.  
  2. Nuclear Power
  UHV grid can promote concentrated integration, effective allocation and safe operation of nuclear power. China’s nuclear power is primarily developed in eastern coastal provinces. In 2020, the installed capacity of nuclear power generated in East China will reach about 30 million KW. If we still depends on traditional EHV grid, the difficulty of choosing corridor will be increased,  and the tech-economic irrationality will also increase the difficulty of overcoming excess system short-circuit current. Besides, as the ever-increasing scale of receiving direct current in East China coastal areas, if we simply rely on or strengthen the current EHV power grid, the problem of voltage instability in East China may not be avoided when there is a serious blackout. Consequently, the stable operation of nuclear power unit cannot be guaranteed. With the help of UHV synchronized power grid constructed in North China, East China and Central China, risks caused by concentrated input of direct current into the East China power grid can be decreased. Furthermore, thanks to the UHV synchronized power grid along with additional regulating capacity of power grid in other areas, the stable operation of coastal nuclear power under rated condition can be guaranteed.           
  3. Wind Power    The development of UHV power grid is important to the construction of wind power consumption platform. In the middle and eastern regions of China, apart from consuming wind power generated by the planned wind power bases of west Inner Mongolia, Hebei, Shandong, and Jiangsu, etc., bulk of wind power generated by northeast and northwest wind power bases are also needed. As a result, the construction of UHV synchronized power grid at receiving regions can act as a larger platform for resource allocation optimization in order to overcome the insufficient consumption ability of large-scaled wind power in China. Due to the differences of seasons and times in various regions of North China, East China and Central China, the maximum and minimum load peak of power system often occur in different months and times. The construction of UHV synchronized power grid is obviously beneficial to load peak regulating and narrowing the gap between maximum and minimum load peaks. Besides, with the help of seasonal peak load complementation of various interregional power resources, the wind power consumption ability of power system is improved. A research shows that the wind power consumption capability of North China-Central China-East China UHV synchronized power grid is 40 million KW more than that of the total wind power consumption capability of the separated power grids in these three areas.
    Conclusion
  Generally, UHV power grid plays an important role in promoting the development of China’s clean energy. It is estimated that the amount of non-fossil energy power generation which can be inter-regionally transmitted and allocated would reach 700 billion KWH in 2020, equivalent to 220 million tons of standard coal and accounted for about 30% of the goal of 15% of non-fossil energy generation in 2020.
  As for the reverse distribution of China’s clean energy resource center and national economic development center, the effective exploration and utilization become basic requirements for the development of clean energy. The construction of UHV grid can promote successful implementation of national energy strategy. This great measure is of benefit to both China and its people.

    (Author: Shi Dinghuan, Counselor of China’s State Council and chairman of Chinese Renewable Energy Society)

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