New guidance system for fish enters pilot phase
Researchers at the Laboratory of Hydraulics, Hydrology and Glaciology (VAW) have developed a new type of guidance system to improve fish protection at hydropower plants. The protection system was recently put into operation at the ecologically refurbished power plant Herrentöbeli on the river Thur. If successful, it could be used at many other plants in Switzerland and abroad. The pilot project is supported by the Federal Office for the Environment.
The curved-bar rack (CBR) fish guidance system consists of specially shaped bars that create pressure and flow differences in the water. "Fish can detect these signals and interpret them as obstacles," explains Robert Boes, professor of hydraulic engineering, the functioning of the system. "Consequently, the fish swim along the rack and toward a safe passage, allowing them to bypass the turbines of hydropower plants.” At the same time, the rack is designed to have minimal impact on power plant operations.
The CBR system was developed as a part of the EU research project "FIThydro". Since 2018 it has been tested with barbel, spirlin, nase, Atlantic salmon, European eel and brown trout at a VAW test facility. For Herrentöbeli, the fish guidance screen was adapted to the local conditions. This complex interdisciplinary orientation phase was supported by a diverse team of civil and environmental engineers, steel hydraulics construction engineers, fish biologists and plant operators.
Promising technology
Over the next two years, day-to-day operations at the Herrentöbeli power plant will be accompanied by extensive hydraulic and fish biological monitoring campaigns. Thereafter, it will become clear to what extent the CBR bypass system, which was developed in the laboratory, is effective and suitable for the real conditions on a mountain river.
"If successful, this novel protection system can be used at numerous other river power plants, such as plants on midland rivers," states Prof. Boes. "Especially for these kind of power plants, there is no other fish protection system yet that is promising and proven both from the point of view of power plant operation and with regard to energy management and fish biology requirements."
Restoring fish migration
The Swiss Waters Protection Act, which was revised in 2011, prescribes measures to restore fish migration in rivers. For this reason, Herrentöbeli had to be refurbished. The hydropower plant is operated by the St. Gallisch-Appenzellische Kraftwerke AG (SAK) and supplies electricity for about 750 households. Due to the great potential of this new technology, the pilot project is financially supported by FOEN.
The research team developed the fish guidance screen together with Wälli AG Ingenieure and the steel hydraulics constructor Fäh AG. The technology, for which a patent application has been filed, was selected as one of the top 20 ETH technologies of 2021. ETH Zurich presents the "Spark Award" each year for the most promising invention that has led to a patent application. The criteria for evaluation are originality, patent strength and market potential.