The exploitation of low-head hydropower by pressure interchange with air, using siphons

The paper describes and analyses a hydropower system based on siphons in wh ich the pressure of low-head water is converted into air pressure. The anal ysis suggests that, with careful design of the flow passages to minimize lo sses, air-pumping efficiencies of 70 per cent or more should be achievable; the overall efficiency of the hydropower system should be better than 60 p er cent. Although such values of efficiency are lower than usually found in hydro plant, the economics of the system are likely to be attractive owing to the low capital cost of the system compared with conventional water tur bine systems. It is shown that a siphon plant is suitable, in single-stage form, for heads up to about 1.7 m. For higher heads the system can be used in two or more stages.