A large pumped storage power station is set to be built deep in the mountains of Xiangyang Township, Luxi County, Yunnan. Kunming Survey, Design & Research Institute Co., Ltd., a subsidiary of PowerChina, recently secured the Engineering, Procurement, and Construction (EPC) contract for this project with a bid of 8.594 billion yuan. The second-ranked bidder was Zhongnan Engineering Corporation Limited, which submitted an offer of 8.65 billion yuan.
The Luxi Pumped Storage Power Station will have a total installed capacity of 2,100 megawatts, comprising six units of 350 megawatts each. Based on this scale, it is classified as a first-class large (Type 1) project, equivalent in rank to a major hydropower station. The station is located approximately 150 kilometers in a straight line from Kunming. The upper reservoir will be situated in a karst depression on the left bank of the Nanpan River, while the lower reservoir will utilize the existing reservoir of the already-built Fenghuanggu Hydropower Station.
The principle of pumped storage is straightforward. During periods of low electricity demand, surplus power from the grid is used to pump water from the lower reservoir to the upper reservoir for storage. When electricity demand is high, water is released from the upper reservoir to generate power. Essentially, it functions as a massive "power bank" for the grid, providing peak shaving and valley filling services. Once operational, the Luxi station will primarily serve the Yunnan power grid, performing functions such as peak regulation, load balancing, energy storage, frequency regulation, phase modulation, and emergency backup.
The project consists of four main components: the upper reservoir, the lower reservoir, the water conveyance system, and the powerhouse complex. The upper reservoir will be constructed in a karst depression through a combination of excavation and fill. Its normal pool level is set at 1,511 meters above sea level, with a minimum operating level of 1,470 meters, providing a storage capacity of 11.14 million cubic meters. The dam will be a concrete-faced rockfill dam with a maximum height of 59 meters. While this height is not considered particularly high for this type of dam, its construction in a karst region makes seepage prevention the critical challenge. Comprehensive anti-seepage measures must be applied to the reservoir floor and banks to prevent water loss.
The lower reservoir is the existing Fenghuanggu Hydropower Station reservoir, which has a normal pool level of 821 meters and a total storage capacity of approximately 50 million cubic meters. Its dam is a concrete gravity structure with existing spillway facilities. Utilizing this pre-existing reservoir significantly reduces investment costs.
The water conveyance system will adopt a "two tunnels, six units" layout, meaning two headrace tunnels will each supply water to three generating units. The horizontal distance is 3,220 meters, with a rated head of 663 meters. This head is considered high for pumped storage projects; a higher head allows for more electricity generation from the same volume of water. The system includes upper horizontal sections, upper inclined shafts, intermediate horizontal sections, lower inclined shafts, and lower horizontal sections, with a surge shaft located at the end of the upper horizontal section. While no surge shaft is planned for the tailrace section, the tailrace tunnels will feature steel linings to prevent water seepage into the powerhouse.
The underground powerhouse will be excavated deep within the mountain, developed from the tail section. The main and auxiliary powerhouse cavern will be 218.4 meters long, 25.5 meters wide, and 58 meters high. These dimensions are substantial for an underground project, equivalent to laying an 18-story building on its side inside the mountain. The main transformer cavern will be 222 meters long, 21.7 meters wide, and 53 meters high, similar in scale. The two large caverns will be connected by busbar tunnels, access tunnels, ventilation shafts, and cable shafts. The construction of this underground complex hinges on ensuring surrounding rock stability and precise blasting control to avoid damaging adjacent structures.
The surface switchyard will include a GIS building, a 500-kilovolt switchyard, a relay protection building, and a diesel generator house to facilitate power transmission.
With a total capacity of 2,100 MW from six 350 MW units, the individual unit capacity is significant. The reversible pump-turbines, capable of both pumping and generating, demand high manufacturing and installation precision.
As the EPC contractor, Kunming Survey, Design & Research Institute is responsible for the complete design, procurement, and construction. During the survey and design phase, a thorough understanding of the engineering geology in the karst region is essential. The Luxi area features typical karst topography, with developed underground caves and subterranean rivers. The anti-seepage design for the upper reservoir built in a karst depression requires careful evaluation, likely involving a grout curtain extending to an impermeable layer.
During construction, the excavation of the underground powerhouse complex will be the critical path activity. Excavating caverns over 200 meters long and 50 meters high will involve layered excavation with support measures applied at each stage, including rock bolts, shotcrete, wire mesh, and steel arches. Areas like cavern intersections and pillars, where stress concentrates, will require intensified monitoring. The water conveyance tunnels will pass through various rock strata, and the high 663-meter head imposes strict requirements on the lining. High-pressure tunnels typically use reinforced concrete linings with surrounding rock grouting or steel linings. The Luxi project already specifies steel linings for the tailrace tunnels, and the solution for the headrace system will depend on geological conditions.
The construction period for a pumped storage power station, from commencement to the first unit generating power, typically spans five to six years. Work on the upper and lower reservoirs, the water conveyance system, the underground powerhouse, and unit installation proceeds concurrently. The underground powerhouse excavation alone may take two to three years, followed by approximately a year and a half for unit installation.
The winning bid of 8.594 billion yuan was less than 100 million yuan lower than the second-ranked offer, indicating a close competition. As a local design institute, Kunming Institute holds advantages in its familiarity with Yunnan's geological conditions, local coordination, and material supply chains. While Zhongnan Engineering Corporation has more extensive experience in the pumped storage sector, it was ultimately outmaneuvered by the local contender.
For the Yunnan power grid, the completion of the Luxi Pumped Storage Power Station will significantly enhance its peak shaving capacity. Yunnan relies heavily on hydropower, which experiences substantial variation between wet and dry seasons, leading to surplus power during wet periods and shortages during dry spells. Pumped storage can store surplus energy from wet seasons for use in dry seasons and also help balance the intermittency of wind and solar power.