Five in focus – new pumped storage schemes22 December 2010
IWP&DC presents details on five important pumped storage schemes currently under development or recently commissioned worldwide
Ingula, South Africa
Ingula pumped storage scheme is located 23km northeast of Van Reenen’s Pass on the border of Free State and KwaZulu Natal in South Africa. The facility will generate power for the national grid. Van Reenen’s Pass was selected out of three sites that were shortlisted from 90 locations. The scheme is being built on a 9000ha site by state-owned Eskom at a cost of R8.9B. The work on the facility began in November 2007 and is expected to be complete by 2014.
Development of the scheme was proposed in 2002 and was initially called the Braamhoek scheme, named after a tributary of the Klip River. In March 2007, the scheme was renamed Ingula. The basic design of the scheme began in 2004, when it was given environmental clearance.
The project will comprise an upper and a lower reservoir. The upper dam, named Bedford Dam, is located in the secondary of Wilge River that flows into the Vaal River system. The dam is 810m long and 40.9m high. It also has a 100m long emergency spillway, a dam crest with elevation of 1740.6m and 8m crest width. It will have a total capacity of 22.6Mm3 and an active storage of 19.3Mm3.
The lower dam, named Braamhoek Dam, is situated in the secondary of Klip River that flows into the Thukela River. The length and crest width of the dam are 331m and 5m. The dam is 38.6m high and has a 40m long crest. The 0.5m dam wall height holds flood inflows to avoid 1:200-year flood dam spill. The lower reservoir will have a 26.3Mm3 capacity and active storage of 21.9Mm3.
The reservoirs, 4.5km apart, will be connected by underground waterways to a subterranean generating plant which will include four 342MW pump turbines from Voith Hydro.
A joint venture led by Italian firms Impregilo and CMC were awarded a contract by Eskom Holdings in 2009 to construct the underground works and reservoirs for the project. Construction works on the scheme include caverns, tunnels, adits, shafts and penstocks, installation of the pump-turbines, and construction of the dams for the upper and lower reservoirs.
Power and automation technology group ABB won a $23M order to supply an electrical balance of plant (eBoP) solution to the project earlier this year. Key products to be supplied include the service and auxiliary transformers, dry-type distribution transformers and medium- and low-voltage switchgear.
As at September 2010, the progress on key works was as follows (courtesy Eskom):
• Surge chambers 3 and 4: Completion of second stage support work in progress. Top support 65% complete
• Surge chambers 1 and 2: Top widening in progress, 60% complete.
• Tailrace tunnel: Advanced 82.95m downstream and 59.96m upstream. Tunnel 63% complete
• Outlet structure: Construction has progressed to the tower section with only the top slab remaining to be cast. Trashracks are partially installed. Stop logs shall be installed before finally casting the top slab. The structure was 90% complete.
• Machine hall: The second of two benches was 50% complete.
• Transformer hall: Work started on the first of two benches.
• Main drainage gallery: Excavation work completed, with concrete work on the invert commencing.
• Penstocks: No 4 is complete, with No 3 at 70%. Widening of the anchor block is in progress.
Limmern (Linthal 2015), Switzerland
Kraftwerke Linth-Limmern AG – a partnership between the canton of Glarus and Axpo – is expanding its existing facilities under the Linthal 2015 project to be able to ensure security of electricity supply in the future. The core of the project is the Limmern pumped storage power plant with a pump and turbine capacity of 1000MW. Construction on the project commenced at the end of September 2009 and is expected to take almost seven years to complete in total. The commissioning of the first generating unit is planned for 2015 and the last for 2016.
The project will pump water from the existing Limmern dam to Lake Mutt; with the level of Lake Mutt to be raised as part of the project. Depending on operating conditions and management of the Limmern dam, the Limmern plant will have a drop of between 560m and 710m.
Lake Mutt is a natural reservoir; the lake’s surface level will be raised by up to 30m through the construction of a 1050m long concrete gravity wall. During turbine operations, water from Lake Mutt will be collected from the inlet/outlet structure and channelled via the 570m long headwater pressure tunnel, which has an inner diameter of 8m, in the direction of the pressure shafts. A service chamber with two butterfly control valves is located at the top of the pressure shafts. The two reinforced pressure shafts are 1050m in length with an inner diameter of 4m; they channel the water down a drop of 680m to the machinery gallery.
Just before the machine gallery, each of the pressure shafts splits into two headwater connecting tunnels that then lead to the four turbines. There is a ball valve on the headwater side of each turbine to control the operational, emergency and maintenance settings. The water surge pressure created in the water system when the shutoff device is activated is dampened by the surge chamber. The water is channelled from the turbines to the Limmern dam via the tailwater tunnels.
The four tailwater tunnels are reduced to two tunnels with a length of 420m and 370m and an inner diameter of 6m. The water is channelled into the Limmern dam via the two inlet/outlet structures.
The underground gallery centre is made up of a machinery gallery and a transformer gallery and the two are connected by various tunnels. The machinery gallery is 160m in length, 30m in breadth and 50m high, while the transformer gallery is 140m long, 20m wide and 25m high. A new access tunnel called ZS 1 will be built from Tierfehd to the machinery gallery and will be 4000m in length with a bored diameter of 8m. The access tunnel will be fitted with a funicular railway to transport heavy loads, and will facilitate the delivery of the generator-transformer units to the site; each unit weighs 225 tonnes.
The four pumped storage units, to be supplied by alstom Hydro, will be installed in the machinery gallery; each unit is made up of a single stage pump turbine with an installed pump and turbine output of 250MW and a variable rotary asynchronous motor-generator with the necessary support and ancillary equipment. The designed throughput volume for the pump action is approximately 35m3/sec and approximately 50m3/sec for the turbine action. The pump turbine units are reversible Francis turbines. Each motor-generator is coupled via its transformer to the 380kV substation. Two 380kV cable systems lead from the substation to the new Tierfehd transformer substation via the ZS1 access tunnel.
A 17km long 380kV overhead line is being constructed from the Tierfehd substation to connect the Limmern pumped storage plant to the Swiss high voltage grid.
In June 2010, consulting firm Poyry was awarded a EUR 2.1M surveying contract for the project. Pöyry’s tasks comprise the independent checking of all major geodetic surveying works as well as geodetic deformation measurements and the monitoring of caverns, dam and tunnel sections. Furthermore, Pöyry’s contract includes the geodetic basic point network and the major setting-out of access tunnels, galleries, caves, gravity dam, surge chamber, pressure shafts and associated structures. Pöyry’s task ends with the industrial surveying for the installation of components such as turbines and steel structures.
ABB will provide electrical equipment, including transformers, medium-voltage switchgears, and instrumentation and automation systems for the project, with Nexans to supply, install and commission six 380kV XLPE-insulated underground cables. DSD-Noell will design, supply and erect two penstocks for scheme.
Limberg II, Austria
Limberg II is being developed as an extension to the Kaprun project by Verbund subsidiary, Austrian Hydro Power (AHP). The project is a US$467M peak-load pumped storage project that, upon completion, will increase capacity at Kaprun from 353MW to 833MW. The project is located in the southern part of the federal province of Salzburg, north of the Glockner Group in the Kaprun Valley, near the junction of the three regions of Salzburg, East Tyrol and Carinthia. It will operate on the existing Mooserboden and Wasserfallboden reservoirs in the lower Kaprun valley. The reservoirs have a live storage of 81.2 and 84.9Mm3 respectively, and a mean level difference of 366m for pumped storage. The power conduit between Mooserboden and Wasserfallboden will have a maximum flow of 140cm/sec The project includes 7.5km of road tunnel and escape tunnel; a cavern measuring 62m x 25m x 44m; a 4km-long, 7m-diameter headrace tunnel; a 750m-long, 5.5m-diameter inclined shaft; a 600m-long, 8m-diameter tailrace tunnel; two valve chambers; and a surge tank.
A tunnel system measuring a total of 5.8km was erected during the initial opening up of the construction site – with work completed in record time and top tunnelling performances of up to 24m per day. The transformer cavern (61m long, 15m wide, 16m high) and the machine cavern, which is as large as the nave of St. Stephen’s cathedral, were completely broken through in July and December 2007, respectively. Once work has been completed on the machine cavern, two reversible Francis turbines with a nominal capacity totalling 480MW will be installed. The units will be commissioned in 2011 and full operation should start in March 2012, with 1.3GWh annual average production from pumped storage mode – the current plant averages 670MkWh/yr. The fully automated plant will be monitored from Kaprun’s main control room.
During construction of the scheme, AHP took great care to avoid negative impacts on the environment and landscape. Only the access buildings and storage areas for tunnel excavation material will be above ground, with the project often being described as the ‘invisible plant’.
Key players in the project are:
• Hinteregger & Sohne: Technical Overhead
• Voith Hydro
• andritz Hydro
• VAM GmbH & Co Anlagentechnik und Montagen
• Poyry Energy
• Arge Poyry Infra GmbH/Intergeo ZT GmbH
• hans-kunz GmbH
Nant de Drance, Switzerland
The Federal Environment Ministry licensed the EUR650M (US$9.3M) Nant de Drance project in August 2008. Located between the towns of Martigny and Chamonix in Valais, Nant is a joint venture between Swiss utility Alpiq (54%), Federal Swiss Railways SBB (36%) and municipal utility FMW (10%).
Atel (forerunner of Alpiq) and SBB first applied to licence Nant in summer 2006. Then the cost estimate was a more modest EUR500M (US$695M). SBB came close to abandoning the project as raw material and construction costs soared over the next 18 months. One condition of the build and operate deal creating the Nant de Drance company, agreed in November 2008 between the then joint partners, was the need to rein in building and engineering costs before work began.
The plant is scheduled to come on-line in stages from 2015, with a maximum 1500GWh annual output of peak load electricity – enough to cover demand from 600,000 homes. The 380kV grid running from Chatelard through the Rhone valley will also be modernised and extended ahead of Nant’s completion.
The contract for construction work on Nant went to Groupement Marti Implenia (GMI). The powerhouse will be built almost entirely underground in a cavern between two existing reservoirs, Emosson (1930m altitude) and Vieux Emosson (2205m altitude), on land belonging to the Valais border municipality Finhaut. A 5.6km long gallery will access the cavern at 1700m altitude in the Lower Valais.
Alstom Hydro will equip the new power station with four 157MW vertical Francis reversible turbines, four 170 MVA vertical asynchronous motor/generator units and further key equipment. Alstom will also handle complete site delivery, erection, supervision and commissioning.
Alstom Hydro’s facilities in Grenoble, France and Birr, Switzerland will be in charge of the engineering and manufacturing of the equipment, to be delivered until 2017. A F Colenco is providing engineering services for the project.
Ukraine has been investing in additional hydropower capacity as it introduces much needed flexibility into its ageing system. One of these projects is the Dnestrovskaya pumped storage plant on the Dnyéstr River, just downstream of Novodnestrovsk in Ukraine. The Dnyéstr River rises in Ukraine, near Drohobych close to the border with Poland, and flows toward the Black Sea. The plant was commissioned in December 2009 by UkrHydroEnergo Open Joint Stock Company (OJSC), a non-profit public organisation which brings together individuals and companies operating in hydropower in Ukraine.
The task of the Dnestrovskaya project is to regulate peak loads in the electricity supply system, participate in frequency regulation, and provide emergency power reserves. The plant has seven 421MW units and, when all units are operational, will have a total capacity of 2947MW, making Dnestrovskaya the largest pumped storage plant in Europe.
The control system on the plant has been supplied as a turnkey project by Emerson Process Management in partnership with Ukrainian Joint-Stock Company Enpaselectro and included the supply of an Ovation expert control system along with the associated project management, engineering, installation supervision, start-up and commissioning services.