Autor: Roland Gruber , 26.06.2016

In order to optimally capture the energy of flowing water and turn it into electricity, efficient technologies are needed, with pipelines being essential parts of the power generation system.

Thanks to top-quality GRP penstocks and pipe routing possibilities that are both highly efficient and cost-saving, HOBAS substantially increases the profitability and brings out the best of hydro power plants all around the world.

The town of New Milford in the US state of Connecticut is home to the Rocky River Hydroelectric Power Plant, the first large-scale pumped-storage development in the United States. The original wooden and steel penstock transported water back and forth between Candlewood Lake and the plant’s surge tank above the Housatonic River. The wooden pipe section DN 4500 was originally built in 1928 and replaced in 1965. As it aged, it began to leak and, after a number of failed maintenance attempts, it was decided to replace the penstock section with a new one. The project went out to bid in January 2012 and the company Kleinschmidt Associates was hired to find a reliable and cost effective replacement pipeline. Kleinschmidt evaluated plastic, steel and GRP as pipe materials. HOBAS GRP eventually exceeded the other materials a number of aspects: The pipe could be easily connected to the existing steel pipeline, it is UV resistant, and the hydraulic capacities and lower friction factor allow for a higher flow rate and an increased electricity generation due to reduced head losses. Furthermore, the hydraulic performance of the HOBAS Pipeline allowed for a reduced pipe diameter, which in turn reduced the installation project’s capital costs. HOBAS Pipe USA supplied 290 m of DN 3000 pipes including three mitered elbows of nine, 18, and 20 degrees. The installation contractor efficiently installed the new penstock – most of it half-buried, only two 6m-sections at the upper end of the penstock that were placed on concrete supports. The penstock DN 3000 was connected to the existing steel pipes with transition sections and the mitered elbows were encased in concrete to resist deformation. The project was successfully completed in December 2012. The owner and operator of the Rocky River Hydroelectric Power Plant, Richard Laudenat, is very pleased with the outcome of the project: “The new penstock continues to meet all of our expectations after its first winter under severe New England weather conditions.”

The family-owned hydropower plant Pena Flor – Los Sisitos in Guatemala was built in 900 m above sea level, in 15 km distance to the two volcanos Santa Maria and Santiaguito. The WKV cross flow turbine with a capacity of 0.6 MW is powered with the water from two creeks which is led in underground non-pressure PVC pipes to the forebay, from which the 802 m long HOBAS Penstock DN 700, PN 6 and 10 runs to the powerhouse. Installation works of the penstock commenced in May 2014. The pipeline route is set on a slight incline and the alignment is relatively straight, except for one 18° bend around 125 m from the powerhouse. On recommendation of the HOBAS Site Expert, the pipes were installed in 1.6 m depth. This way, passive earth pressure holds the pipe in place and laborious, time-consuming thrust block designs were unnecessary. Because of the rainy season with up to 125 mm rainfall per day, the pipe trench had to be prepared bit by bit to prevent the walls from collapsing. Bedding material from nearby creeks was manually shoveled onto trucks, unloaded, and wheeled to the trench. Despite the difficult conditions, an average installation rate of five pipes per day could be achieved. Thanks to a perfect collaboration of the construction team, the owner Juan Pablo Cordon who personally supervised the installation, and not least the HOBAS Site Expert who advised the team in optimally storing, transporting, handling, and installing the products, the installation works were finalized to everyone’s content in September 2015. The pressure test was successfully conducted and the hydropower plant went into service on October 27, looking ahead to decades of green energy.

The Schwarzenberg family foundation Vaduz operates three small hydropower plants in the Austrian municipality Turrach. After two of them, Leimingbach and Geissbach, with a joint standard capacity of 1.8 GWh had been successfully operated for some time, the family foundation endeavored the erection of a further plant at the stream Turrachbach in 2012. In aiming to unite high quality and longevity with economic viability, particular attention was paid to the choice and design of the approximately 2.5-km-long penstock. Featuring a service life of at least half a century and optimal hydraulic properties, HOBAS Hydropower Pipe Systems presented the ideal solution. Under the supervision of the planning agency Pittino ZT GmbH, the contractor Felbermayr Bau commenced the construction of the plant with 71 m head in March 2012. The comparably light pipes, which were delivered in 3 and 6 meter lengths, were installed quickly and easily with an average cover of 1.5 m. The upper half of the penstock was implemented with HOBAS Pipes DN 1600, PN 4 and 5, the lower part with HOBAS Pipes DN 1500, PN 6, 8 and 10. Rocks and ledges dominate the last 100 meters of the penstock so that a cast iron pipe DN 1200 was connected to the GRP line there. Thanks to the possibility to accommodate angular deflection in the couplings and the proven method of angular cut pipe ends, the line could be optimally adapted to the route across the narrow valley of the Turrachbach while saving on bends and keeping installation costs to a minimum. After all necessary tests had been conducted, the cross-flow turbine with a standard capacity of 5.4 GWh went into operation in December 2012. Pleased with the result, the director of the Schwarzenberg family foundation, Michael Sterneck, says: “Of course we want these projects to be economically successful. However, to us it is most important to have a solid and environmentally sound construction.”

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