HYLOW · Hydropower converters with very low head differences

Small hydropower with very low head or pressure differences below 2.5 m and hydraulic power ratings of 50 to 1000 kW is a significant renewable resource, with an estimated unused potential in rivers alone of e.g. 600 to 1000 MW in the UK and more than 500 MW in Germany. The economically and ecologically efficient utilisation of this hydropower bracket still constitutes an unsolved problem since conventional turbines (Kaplan or Cross flow) are not cost effective, and since they are considered to have a negative ecological impact. In order to open up this hydropower bracket for exploitation, an innovative solution - the hydrostatic pressure turbine - was developed. This novel hydraulic machine utilises differential hydrostatic pressures; with theory and initial model tests indicating high theoretical efficiencies for low head differences. It rotates at slow speeds and operates under atmospheric pressure with a continuous bed, thus minimising negative impact on fish and allowing for unhindered sediment and fish passage. Initial work indicated significant development potential, whilst the expected structural simplicity promises increased cost effectiveness. Three configurations will be investigated for different applications in rivers with a head difference, for free stream situations and for energy generation in water supply systems. The configurations will be optimised using a combination of small and large scale model tests, theoretical and numerical modelling. The ecological impact will be assessed at every step of development, and fed back into the R/D process to achieve an ecologically effective design. In the absence of appropriate testing facilities, large scale tests will be conducted in natural rivers scenarios, adding to the realism of environmental impact assessment. The project is expected to develop, and prove, novel economically and ecologically effective hydropower converters for applications with head differences below 2.5 m.