Product Abstract

This report presents the results of a collaborative research project funded by the Electric Power Research Institute (EPRI), the U.S. Department of Energy (DOE), and hydropower industry partners with the objective of completing the remaining developmental engineering required for a "fish-friendly" hydropower turbine called the Alden turbine. Earlier engineering and research that was started in 1995 and completed in 2008 established a viable conceptual design. Additional engineering completed in 2009 and 2010 included (1) converting a conceptual design with the use of computational fluid dynamics into a machine design that can be built and (2) constructing and testing a physical model of the turbine to evaluate its performance characteristics for economic analysis and mechanical layout. Completion of these efforts provides a mechanical and electrical design that can be readily adapted to site-specific conditions with additional engineering development comparable to costs associated with conventional turbine designs.

Objective

The primary challenge for this project was to complete the requisite engineering necessary to convert a conceptual turbine design into a design that could be built and commercially competitive with existing hydropower turbine designs. The overall objective was to provide a turbine design ready for actual manufacture, field deployment, and testing. Future demonstration of the commercial and fish protection viability of the Alden turbine is vital for the ultimate acceptance of the Alden turbine by the resource and regulatory agencies, non-governmental organizations, and the hydropower industry.

Approach

Starting with the previously engineered and researched conceptual design, computational fluid dynamics was used for the hydraulic development of the turbine and was accomplished with engineering design modifications to the spiral case, distributor (stay vanes and wicket gates), runner, and draft tube to improve turbine performance while maintaining high fish passage survival. A scaled (1:8.71) physical model of the turbine was manufactured and tested with data collected for power and efficiency, cavitation, runaway speed, axial thrust, radial thrust, pressure pulsations, and wicket gate torque. These data were used to determine the final sizing of the supporting mechanical and balance of plant equipment, estimate cost, and develop the supply schedule.

Results

Computational results for pressure change rates and shear within the runner passage were similar in the original and final turbine geometries, while predicted pressures were higher for the final turbine at the blade leading edges and within the draft tube cone below the deflector. These pressure improvements resulted in a new turbine setting that is over 9 feet (2.7 m) higher when compared to that originally planned for the pilot site. The final turbine geometry and resulting flow environments are expected to further enhance the fish passage characteristics of the turbine when compared to the original conceptual design due to improved flow alignment at the blade leading edges, improved runner-draft tube interaction, increased minimum pressures within the water passage, and improved component alignment between the stay vanes with the wicket gates. Computational results for the final hydraulic shapes were shown to improve turbine efficiencies by over 6% at the selected design condition when compared to the original concept. Prior to the release of the hydraulic components for model manufacture, finite element analysis (FEA) calculations were conducted for the stay vanes, wicket gates, and runner to verify that structural design criteria for stress and deflections were met. Performance of a physical model of the turbine tested for power and efficiency, cavitation, runaway speed, axial thrust, radial thrust, pressure pulsations, and wicket gate torque indicated that all parameters were observed to fall within ranges expected for conventional radial flow machines. Based on these measurements, the expected efficiency peak for the prototype application is almost 94%. The preliminary turbine cost for the design specification is $1450/kW with a total supply schedule of 28 months. This supply includes turbine, generator, unit controls, limited balance of plant equipment, field installation, and commissioning.

Application, Value and Use

Hydropower planners, managers, and developers will find the information provided to be of value for planning new development, for adding capacity to existing projects and non-power dams, and for harnessing lost power associated with minimum flow (either below the dam or into the bypass reach for environmental values) and non-turbine discharges for downstream fish passage. The Alden turbine may also be used as a retrofit option where existing downstream fish passage mortality associated with conventional turbine operation is unacceptable to licensing stakeholders.