With an installed base of 56 GW of pump turbines and motor generators, Alstom is currently developing 6 GW of PSP projects worldwide. Three gigawatts are variable speed, and the other three are of the fixed speed type. Besides the flexibility benefit, some sites actually require variable speed, since a variable speed PSP can sustain a higher variation in the height (or head) between the water in the two reservoirs. “Challenging sites such as Nant de Drance in Switzerland and Tehri in India would have been impossible to exploit without variable speed pumps,” says Teller.
All Alstom’s in-house products and technologies for hydraulic turbines are designed and developed in the Global Technology Centre (GTC) in Grenoble, France. This centre manages all the product development phases, from identification of customer need to aftersales service.
In 2008, Alstom expanded the GTC, equipping its scale model test laboratory with 2 new test rigs, bringing the total number of test rigs to 6 and doubling the site’s testing capacity.
With a pumped storage market expected to grow by 60 % over the next 4 years (mostly in China and Europe), the GTC is now looking forward to extending PSP operational envelopes towards more challenging conditions (1) such as very high or very low head (>800 m and <50 m), increased head range, underground and sea operation, small decentralised PSPs, etc., as well as enhancing flexibility and power range.
(1) 40 % of European PSPs are expected to be variable speed.
An extra 1,000 MW from a cavern under the Swiss Alps
Switzerland, with its mountainous landscape, is a very active producer of hydroelectricity, which represents more than half of the total energy produced in the country. The steep altitude differences in the Swiss Alps create a particularly favourable environment for the use of pumped storage power plants. In 2009, Kraftwerk Linth-Limmern AG (KLL) decided to extend its Linthal power plant in the Glarus Canton of east-central Switzerland by constructing a new underground pumped storage facility that will pump water from Lake Limmern up to Lake Mutt (which is 630 m higher, at an altitude of 2,474 m). The water is pumped through a pair
of 1 km-long penstocks inclined at 45°, in order to reuse it for electricity production when needed. Alstom will provide
four new 250 MW variable speed pump turbine and motor generator units. “The facility, which is installed in a giant underground cavern, will have pump and turbine capacities of 1,000 MW, boosting KLL’s output from the current 450 MW to 1,450 MW and putting it, in terms of power delivery, on a par with the Swiss Leibstadt nuclear power plant,” says Thomas Kunz, Alstom’s Global R&D Product Development Director. Many innovative components had to be developed for this project. The first units are to be installed next year, and Linthal commercial operation is due to begin in 2015.