SubScrew Hydro Project: Low-cost fish friendly solution for river connectivity

The recently ratified Nature Restoration Law (NRL) aims to remove river barriers so that 25,000 km of rivers returns to free-flowing status. This presents challenges to development of new hydropower projects especially those that take advantage of pre-existing river barriers. The removal or modification of existing barriers in rivers appears to be a costly exercise with considerable social and environmental impacts. As such, it has emerged that barrier modification to open up routes for fish and sediment movement is the most credible option to comply with the NRL due to its cost implications. The SubScrew Hydro Project intends to address the cost, public opposition and environmental issues associated with river barrier removal by developing a low-cost barrier modification system for the safe passage of fish and downstream transport of sediments. Results from stakeholder engagements revealed a widespread demand for community energy projects which could benefit from this project. It also highlighted a need to overcome challenges to fish and sediment movement across river barriers and the need to simplify the environmental consenting process for micro-hydropower projects as they are currently onerous, costly and time consuming. The application of analytical pump-as-turbine conversion ratios to a database of centrifugal screw pumps revealed their potential for energy generation when operated at heads and flow rates between 10-100m and 2-1650 l/s, respectively ,while generating up to 750 kW of power at up to 82% efficiency. The project will confirm these performance characteristics, the machine’s fish friendly nature and propose its use for barrier modification.