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Hydropower Engineering at SAFL
Hydropower has been part of the research program at SAFL since its inception in 1938. Spillway and intake model studies have been carried out on many major hydropower sites around the world, including what still is the world's largest—Guri in Venezuela. Following this extensive international activity, SAFL was a major player in the development of hydropower within Minnesota. Viable hydropower sites were identified and developed during energy shortages in the 1980's, including St. Cloud, Rapidan, Byllesby, and Hastings, in Minnesota, and Jim Falls in neighboring Wisconsin. SAFL research into environmental effects of dams was called upon in licensing studies. We have provided turbine efficiency acceptance testing and hydraulic design assistance in the form of model studies.
SAFL researchers have also pioneered advanced Computational Fluid Dynamics (CFD) schemes for analysis and design of turbines, including the effects of cavitation. Earlier work identified draft tube performance as a major problem for retrofitting older plants with new runners passing larger discharges. The laboratory's research anticipated this problem, and our resulting CFD codes are the first to realistically evaluate the problem of unstable flow in draft tubes.
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Research Projects
The Physical Model Study of the Fish Bypass Louver System of the School Street Hydroelectric Project
To determine the head losses associated with a 20-degree fish bypass louver system proposed for the School St. Hydroelectric Project in Cohoes, NY, a physical model study of a section of the channel leading to the power house and the louver structure was conducted at St. Anthony Falls Laboratory. The model scale was 1:14. The tests were conducted under 3,100, 5,100 and 7,100 cfs flow conditions, and three louver configurations: 1) 2-inch bar spacing, 2) 4 3/8-inch bar spacing and 6 3/4 & 4 3/8 & 2-inch bar spacing. In addition to head loss, other parameters such as water surface drop across the louver, and flow velocities along the louver as well as upstream of the louver were measured.
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Selected Applications
- Hydropower feasibility at existing dam sites
- Environmental & licensing problems
- Spillway and turbine oxygen dynamics
- Numerical simulations
- Turbine and spillway cavitation
- Intake and powerhouse hydraulic design
- Turbine efficiency testing
- Powerplant cooling/thermal effects
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Hastings Lock and Dam Oxygen Study and Navigation Study.
SAFL identified the potential of this site on the Mississippi River at Lock & Dam No. 2 in a state-wide review of hydropower feasibility. We completed field investigations, analyzed dissolved oxygen changes caused by the plant, and proposed mitigation alternatives for low oxygen conditions. We also evaluated, via modeling, the effect of plant flows to barge navigation into the locks.
St. Cloud Dam Hydropower Study
At St. Cloud, Minnesota, SAFL conducted a model study to assist in the design of the approach channel to the plant. Modeling identified changes in channel configuration needed to eliminate problematic intake vortices. After construction, SAFL conducted efficiency acceptance testing required by the turbine supply contract and in compliance with IEC standards.
Wissota Hydro Plant Automatic Spillway Gate Study.
The Wissota Hydroplant is located on the Chippewa River at Chippewa Falls, Wisconsin. The main purpose of this study, commissioned by the Northern States Power Company, was to assure that the automatic spillway gates of the Wissota Plant would operate properly during the Probable Maximum Flood (PMF) as required by the Federal Energy Regulatory Commission (FERC). Based on measurements on the prototype gates and on a physical hydraulic model built at SAFL to test conditions not possible on the prototype, it was found that (due to flow separation and ventilation which created an uplift force), the gates would not remain in a fully down position at the higher discharges without additional force being applied. Further studies were performed to evaluate the pressure distribution on various gate lip configurations due to an additional force applied hydrodynamically.
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