A Passive Fish Screen for Hydroelectric Turbines
approach velocity, bypass, downstream fish passage, hydroelectric, inclined screen, intake, mortality, penstocks, screens, turbines, wedgewire, wedgewire screens
The author designed a fixed screen to bypass fish from the intakes of hydroelectric turbines. It is entirely within a turbine penstock. It utilizes Johnson wedgewire screen with 2 mm bars and 2 mm spaces and is in the penstock at 19 degrees to the flow with bars parallel to the flow. A volume of 400 cfs goes through 250 square feet of screen resulting in approach velocities of 1.6 fps. Flow over the screen is 5 fps. A 30-inch pipe bypasses 50 cfs at 10 fps. The main screen tilts 45 degrees, so that backflushing cleans it. Test fish put through the system were collected in a trap. No mortalities were found. A small number had lost scales, but this was probably from sources other than the screen. During a year's operation, the designed cleaning system was at times used, although not generally by necessity. Cost was about $100,000, of which $15,000 was for the screen material.