Horizontal trash rack – a new intake concept for efficient backflushing

At many hydropower intakes in rivers, there are extensive problems with debris fouling the trash rack. An alternative to manual or mechanical cleaning is the hydraulic concept of backflushing, in which water removes debris from the trash rack and flushes it back to the river out of a flushing conduit. A new intake concept with the intake gate located upstream of a horizontal trash rack, for the efficient utilization of backflushing, is tested in a physical model. The experimental results provide an opportunity for energy production during the automatic cleaning. The cleaning efficiency is strongly dependent on the flushing capacity. The costs related to the flushing conduit and a slightly increased head loss can be less important for many cases than the advantages from timely and efficient debris removal, reduced costs for human labor and improved safety. Additional possibilities for downstream fish-passage through the bottom outlet call for further studies.