Tech Notes

Study downgrades GHG impact of hydro project reservoirs

An international team of scientists has amassed the largest data set to date on greenhouse gas emissions from hydroelectric reservoirs. Their analysis, published in August in the online version of Nature Geoscience, posits that these human-made systems emit about one sixth of the carbon dioxide and methane previously attributed to them.

Prior studies based on more limited data cautioned that reservoirs impounded to provide water for hydro projects could be a significant source of both carbon dioxide and methane.

Through an analysis of 85 globally-distributed hydro reservoirs, the authors revealed that these systems emit 48 million metric tons of carbon annually, compared to earlier estimates of 321 million metric tons. Further putting things in perspective, hydro reservoirs are responsible for less than 16% of the total carbon dioxide and methane emissions from all types of human-made reservoirs combined.

"Our analysis indicates that hydroelectric reservoirs are not major contributors to the greenhouse gas problem," comments Dr. Jonathan Cole, a limnologist at the Cary Institute of Ecosystem Studies and one of the paper's authors. "But there are some caveats. To date, only 17% of potential hydroelectric reservoir sites have been exploited, and impacts vary based on reservoir age, size and location."

ICOLD Forum: Bulletin on geomembrane sealing systems

The International Commission on Large Dams (ICOLD) offers Bulletin 135, Geomembrane Sealing Solutions for Dams.

This technical bulletin covers factory-made continuous polymeric and bituminous sheet geomembranes and their application in dam construction. The bulletin was prepared by ICOLD's European Working Group, which consists of 15 members from nine countries.

The 464-page bulletin covers:

— Materials, testing and ageing;

— Geomembrane testing;

— Loads applied to geomembrane sealing systems;

— Geomembranes for new construction and rehabilitation of fill dams;

— Geomembranes on concrete and masonry dams;

— Geomembranes for roller-compacted-concrete dams: New construction, rehabilitation and induced joints;

— Special cases (such as repair of joints and cracks); and

— Control of quality of a geomembrane sealing system.

The bulletin updates Bulletin 38, issued in 1981, and Bulletin 78, issued in 1991. This new bulletin also deals with application of geomembranes for dams affected by alkali-aggregate reactivity and reports about sealing of defective joints and cracks in the upstream face of concrete-faced rockfill dams.

To order this bulletin for €76 (US$106), visit www.icold-cigb.net and click on Publications, then Bulletins.

— ICOLD is a nongovernmental organization providing a forum for knowledge exchange in dam engineering. To learn more about ICOLD, contact Michel De Vivo, Secretary-General, ICOLD, 61 avenue Kleber, Paris 75116 France; (33) 1-47041780; E-mail: secretaire.general@icold-cigb.org.

Chile utility develops hydro maintenance pilot program

Endesa Chile plans to evaluate results by the end of the year from a pilot condition-based maintenance (CBM) program the company expects will increase the availability of its hydroelectric units, reduce costs and improve asset management.

Endesa Chile, a subsidiary of Endesa Group of Spain, initiated CBM with the goal of designing an expert system to leverage the knowledge and experience of specialized personnel at its facilities. That is to enable the company to optimize preventive maintenance of generating units to reduce corrective maintenance, predict faults and prolong useful life of equipment.

An expert system was designed that accumulates and analyzes all information obtained in real time from a plant's monitoring system. It also integrates and processes all the data obtained by maintenance personnel and from laboratory reports, operations logs and systems.

Additionally, the experience of specialists is to be captured and retained using the expert systems, which are based on software designed to emulate the reasoning of specialists.

The pilot program was initiated at the end of 2010 at Endesa Chile's 570 MW Pehuenche project in central Chile. The two-unit project has been producing power for about 20 years, with output in 2010 totaling 2,091 GWh. Endesa says the Pehuenche plant offers ideal conditions for implementation of CBM, yielding a wide range of operational data.

Based on the results of the pilot project, the experiment is to be extended to all critical hydroelectric units in Latin America in which Endesa has an interest.

IHA elects 18 to board

The International Hydropower Assoc-iation elected a new board of directors September 9, with 85% voting member participation. IHA reports 1,084 votes were cast out of a possible 1,262, naming board members to two-year terms.

New board members are:

— Dr. Refaat Abdel-Malek

— Roy Adair, Hydro Tasmania

— Ken Adams, Manitoba Hydro

— Colin Clark, Brookfield Asset Management Inc.

— Jean-Michel Devernay, EDF Hydro Engineering Centre

— Roger Gill, Hydro Focus Pty

— Dr. Dominik Godde

— Rasim Khaziakhmetov, RusHydro

— Chuxue Lin, China Three Gorges Project Corp.

— Gil Maranhao Neto, GDF Suez Energy

— Dr. Terry Moss, Eskom Holdings

— Dr. Roland Muench, Voith Hydro Holding GmbH & Co. KG

— Mario Lucio Ozelame, Itaipu Binacional

— Israel Phiri, Ministry of Water and Energy Development, Zambia

— Martine Provost, Hydro-Quebec

— Karin Seelos, Statkraft

— Torstein Dale Sjotveit, Sarawak Energy Berhad

— A.B.L. Srivastava, NHPC Ltd.

Austrian plant to feature thermomechanical steel penstock

The 430 MW Reisseck II pumped-storage plant, currently under construction in Austria, is being equipped with a high-pressure penstock lining assembled using thermomechanical steel.

The fine-grained structure of steel can be improved by restricting the alloying elements via a thermomechanical treatment. This treatment consists of a combination of deformation, heating and cooling operations.

The 430 MW Reisseck II pumped-storage project, an addition to the 138.1 MW Reisseck/Kreuzeck complex, will be equipped with a high-pressure penstock lining assembled using thermomechanical steel.

When compared with heat-treated steel, thermomechanical steel offers the advantages of simpler welding and lower production costs, says Bilfinger Berger Industrial Services (BIS) Group, the company responsible for the planning, production and assembly of the high-pressure penstock lining and related components at Reisseck II.

The penstock for Reisseck II, owned by Verbund Austrian Hydro Power AG, will be fabricated with a strength class of 690 N/mm². The penstock has a diameter of 3.6 meters and an operating pressure of 105 bar. The material required has a total weight of 3,963 tons.

Reisseck II is an addition to the 138.1 MW Reisseck/Kreuzeck complex in Upper Carinthia. Construction is expected to cost €335 million (US$412 million).

Construction on this project began in the summer of 2010. Assembly of the penstock is scheduled to begin in July 2012. Commissioning of Reisseck II is expected in 2014.