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ICOLD Forum: Bulletin on concrete-faced rockfill dams

The International Commission on Large Dams (ICOLD) offers a technical bulletin devoted to design concepts, analysis, foundation treatment, instrumentation, construction, and performance of concrete-faced rockfill dams (CFRD). Bulletin 141, Concrete Face Rockfill Dams – Concepts for Design and Construction, was prepared by the ICOLD Committee on Materials for Fill Dams.

The origin of CFRDs is the Sierra Nevada in California, USA, in the 1850s, the bulletin states. With the advent of vibratory-roller-compacted rockfill in the 1950s, the development of CFRDs progressed. Today, this is a major dam type, with 68 completed between 1990 and 2000, the bulletin says.

The bulletin is divided into 11 chapters:

— Development of CFRDs;

— Analyses for design;

— Foundation excavation, treatment;

— Plinth (dimensions, geometric layout, stability, etc.);

— Perimeter joints and waterstops;

— Face slab (behavior, dimensions, crack development, etc.);

— Parapet wall (height, joints, crest width, etc.);

— Embankment zones and properties;

— Instrumentation;

— Performance of CFRDs; and

— Appurtenant structures (such as low-level outlets and spillways).

The 402-page bulletin uses data from Bulletin 70 (published in 1989), as well as the proceedings of several conferences.

To order this bulletin for €90 (US$122.50), visit www.icold-cigb.org and click on Publications, then Bulletins.

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

Screw generator produces electricity at low-head sites

A centuries-old technology is being used today to generate electricity. The design of the Archimedes screw is attributed to Archimedes of Syracuse in the 3rd century BC. Originally, this technology was used to lift water up an incline. Recently, scientists determined that it is possible to produce electricity by letting water drop through the screw.

The screw generator consists of a central shaft with a helical blade, like a screw. Allowing water to flow downward through the screw causes it to rotate. This rotation can be used to produce electricity using a generator. The screw generator is safe for fish to pass through and can serve as a fish ladder, the company says. The screw generator can be used in locations with relatively low head (up to 10 meters) and requires minimal maintenance, Spaans Babcock says.

Spaans Babcock is one company that manufactures the Archimedes screw generator. Units are available in capacities up to 500 kW.

This technology is being used in several applications. Near Bedford, UK, two 180 kW Archimedes screw generators are being installed in the Great Ouse River to power Borough Hall, the offices of the Bedford Borough Council.

In May 2010, Spaans Babcock was awarded a contract to supply and install four Archimedes screw generators at a training camp location for the London 2012 Olympic Games. This work is part of an ongoing upgrade of the Tees Barrage whitewater course. The screws will pump water to provide the course. When not needed, the screws can use the river water to generate electricity.

Hydro potential in Mexican rivers

An assessment shows that there are feasible hydro projects with nearly 270 MW of capacity in three river basins located in Mexico.

This assessment was performed by the Mexican Institute of Water Technology for the Comision Federal de Electricidad (CFE), the national utility in Mexico. The assessment was to include hydro projects with a maximum capacity of 30 MW that do not require a reservoir, says Armando Trelles Jasso, water resources and energy specialist with the institute. The three river basins selected for the pilot study were Culiacan, Nautla, and Tecolutla.

Two different methods were used for the assessment, Jasso says. The first involved regional regression equations, which allow estimation of mean stream flow based on drainage area, mean annual precipitation, and mean annual temperature. The second involved a distributed hydrological model, which allows simulation of daily multi-annual stream flow series and other hydrologic variables based on distributed physiographic characteristics of the river basin and daily time series of precipitation and minimum and maximum temperatures at weather stations. The second method was retained for being more precise and complete.

Potential projects identified were classified according to their capacity (up to 100 kW, 100 kW to 1 MW, and 1 to 30 MW), hydraulic head and applicable turbine technology (conventional or nonconventional).

Hydropower potential was classified a number of different ways, including:

— Basic or gross potential;

— Available basic potential (taking into account river reaches already developed and those in a conditional or exclusion zone); and,

— Feasible basic potential (taking into account grid connection, substations, etc.).

Results show that, for example, there is a feasible capacity of 42.9 MW across some 139 high-head, mini hydro (up to 1 MW) projects in Tecolutla river basin.

The results of the assessment were included in a geographic database that features river reaches and sites of feasible projects. The database also includes context features, such as electrical infrastructure, exclusion zones, access areas, hydrography, and more. The database can be queried by topology, location, exclusions, hydrology, and other features.

According to Jasso, the same methodology and tools can be used to perform a similar analysis in other river basins throughout the world.

Project investigates using hydro to support other renewables

The HydroPEAK project under way in Norway is studying how the hydropower system can be used to support the increasing amount of non-regulated renewables in the Nordic and European power system. The study also will assess what type of adaptations will be needed both in the existing and future hydropower systems.

HydroPEAK consists of eight work packages and outcomes:

1. Scenarios and dissemination. Collect and analyze information and generate scenarios for future development of the renewable capacity and its impact on the hydro system in Norway. Organize a conference at which the main results and findings will be presented.

2. Hydrology. Improve inflow prognosis tools for both long-term management and short-term peaking operation, including flood management.

3. Impact of short-term effects on long-term hydro scheduling. Improve long-term scheduling models to take into account the turbine-related costs of rapid variations in operations, better represent time delays, and account for reserve markets.

4. Pumped-storage plants. Evaluate the demand for changes in operational modes, perform a system dynamic evaluation of existing plants, and develop effective systems for altering between pump and turbine modes of operation.

5. Frequency and load governing. Evaluate the original dimensional criteria regarding governing stability, define new demands under changing operational regimes, and develop governing and control systems to meet this new challenge.

6. Effects of load fluctuation on tunnels and associated hydraulic structures. Develop scenarios for hydraulic fluctuations at selected sites, develop experimental reaches for monitoring and testing, analyze the effects of fluctuating loads on tunnels and structures, and develop guidelines and propose mitigation measures.

7. Physical effects of load fluctuations in rivers and reservoirs. Develop scenarios for hydraulic fluctuations at selected sites, develop experimental reaches for field monitoring and testing, analyze the effects of fluctuating loads on bed and banks, and develop guidelines and propose mitigation measures.

8. Ice problems in rivers. Analyze ice formation at several regulated study sites with rapid variation in hydro production over the winter season, study the impacts of ice runs and increased ice production on intakes, and propose mitigation measures to handle adverse ice conditions.

The HydroPEAK project kicked off in 2009 and is being coordinated by the Norwegian Institute for Nature Research, Norwegian University of Science and Technology, and SINTEF. SINTEF is an independent research organization in Scandinavia.

For more on this project, visit: www.sintef.no/projectweb/cedren/hydropeak

Study to identify effects of climate change on Central America hydro

The Organizacion Latinoamericana de Energia (OLADE) plans to study the vulnerability of hydroelectric systems in Central America to the potential effects of climate change.

OLADE has requested funding from the Inter-American Development Bank for the study of hydro systems in Central American countries, including Costa Rica, Guatemala, Honduras, Nicaragua, and Panama. Because climate change is expected to affect the hydrological cycle, it could affect water resources and hydropower generation.

A consultant, fluent in Spanish, will collect and analyze available information on climate variability and the effects they have on the energy sector. The consultant also is to study the impact of climate change on major climatic variables in Central America.

Work is to include case studies in Guatemala, Honduras, Nicaragua, Costa Rica, and Panama of the vulnerability of their hydro systems to climate change. For each case study, the consultant is to analyze the benefits and costs of adaptation to climate change. The consultant is to develop a methodology for assessing vulnerability to climate change in other hydroelectric systems of Central America and in the surrounding communities.

The work also is to include capacity building and dissemination of study results through workshops and technical meetings.

Scottish laboratory creates renewable energy facility hub

The Scottish Energy Laboratory (SEL) has been created to improve collaboration between Scotland's low carbon energy development facilities.

SEL brings together 50 energy research, test, and demonstration facilities, including the European Marine Energy Centre in Orkney. The lab will allow national and international companies to identify the best test and demonstration assets for their technologies.

The SEL network has a combined investment value of US$406.6 million across all key energy sectors, including hydrogen and offshore wind. It is supported by Scottish Enterprise, Highlands & Island Enterprise, Scottish Development International, the Energy Technology Partnership, and the Scottish devolved government.

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