Hydropower Station
Jiangsu Yixing Pumped Storage Power Station
    Jiangsu Yixing Pumped Storage Power Station is one of significant energy project to be constructed in Jiangsu Province’s 15th Five-year Plan Period and also the first large-sized hydropower project with a total installed capacity of 1MW in Jiangsu Province. The project is financed by World Bank. In the year 2004, it was listed as a national important project by the State Development & Reform Commission.
    The power station locates in Tongguanshan Mountainous Region, at southeast suburb of Yixing City, about 7km from city proper, is a daily regulation and simply pumped storage power station. The rated water head of power generation of the power station is 363.00m. The total installed capacity is 4 x 250MW with 4 units of reversible pump/turbine. Daily average energy output is 4085kWh and annual energy output 1490GWh and annual energy consumed for pumping water 1960GWh at a comprehensive efficiency of 0.76. The power station after built will be mainly engaged in tasks of load peak regulation, load trough fill, frequency and phase modulation, spinning reserve etc.
    The power station consists of upper reservoir, lower reservoir, water conveyance system, underground powerhouse and 500kV ground substation etc.
    Upper reservoir is built by excavation and filling in a col. The main dam is a composite rockfill dam faced with reinforced concrete, plus a concrete retaining wall, which is laid at downstream of conventional reinforced concrete faced rockfill gravity dam. The dam crest’s elevation is 474.2m, and the maximum dam height above toe board 47.2m and dam axis length 498.9m. Auxiliary dam is a RCC gravity dam, with the maximum dam height of 35m. The upper reservoir has a normal storage level of 471.5m, normal drawdown level of 435m due to power generation and dead level of 428.6m. The reservoir bed is at the elevation of 427m. A total storage capacity 5.307 million m3 and its effective one is 5.073 million m3. The upper reservoir adopts reinforced concrete face covering whole bed for impervious purposes.
    Lower reservoir is formed by reconstructing and expanding the original Huiwu Reservoir. Dam built on lower reservoir is a rockfill dam with clay core. The dam crest’s elevation is 83.4m and the maximum dam height 50.4m. The reservoir has the maximum storage level of 80.60m and a normal storage level of 78.90m and a deal level of 57.00m, and total storage capacity of 5.728 million m3. Since natural runoff into the reservoir isn’t sufficient, it is supposed to build a water complementary component to divert water from Huangtong River into the lower reservoir.
Water conveyance system lies in mountain mass between upper and lower reservoirs. Structures include intake/outlet at upper reservoir, emergency gate shaft (also as surge shaft), diversion tunnel, tailrace tunnel, tailrace gate chamber, tailrace surge shaft, intake/outlet at lower reservoir. A layout of two chambers – four units is applied in water conveyance system. The diversion system has a total length of 3000m and diversion tunnel employs complete steel lining structure with a tunnel diameter range of 6.0 ~ 3.4m. Tailrace tunnels are lined with reinforced concrete. The tunnel diameter ranges 7.2 ~ 5.0m and its total length is 3300m.
    Underground powerhouse chamber group locates in the middle part of water conveyance system. Main chambers in cavern include main and auxiliary powerhouses, main transformer chamber, busbar chamber, out-going line chamber etc. Underground powerhouse is laid in the middle-to-headrace pattern. The excavating dimension of main and auxiliary powerhouses is 155.3m×22.0m×52.4m (length x width x height). Substation locates on eastern side of col about 200m north to underground powerhouse, on a moderate slope at the elevations of 170 ~ 210m.
    Static investment in the power station is 3.985 billion RMB yuan and dynamic investment 4.763 billion RMB yuan including the loan of US$ 145 million from the World Bank. The capital accounts for 20% of the total investment. The remaining 80% consists of World Bank loan (i.e. US$ 145 million used for procurement of electromechanical equipment) and domestic bank loans (local investment).
    The main works was started construction in August 2003 and is expected to have 1st unit put into operation in December 2007 and all units into operation in December 2008.
    During construction period of the power station, materials supply, productive and living demand of constructors, tax on construction and operation, tax on city’s construction will all strongly promote Yixing’s economic prosperity and development. It may also gradually improve environment around the power station, resulting in tourism attractions added. The power station after built will not only function the regulation of load peak and the fill of load trough but also the modulation of frequency and phase, emergency reserve which are dynamic effect and cannot be replaced by other power supplies. It is favorable for the improvement of power supply structure in power grid, the elevation of power grid stability, safe and economical operation, and effectively promotes continuous, steady and fast development of Jiangsu Province’s economy.