Lock Form Reversible Tidal/River Energy Extraction Device

A means of extracting power from tidal or river flows is provided consisting of two or three gate type sluice valves 2,3, and 4 mounted one behind the other along the length of a flume channel 1 where the water level is higher at one end of the flume to the other. Each gate can stop or allow the flow of water through the channel. Two of the gates 2,3 are mounted a fixed distance apart and the third 4 is mounted onto a carriage that travels backwards and forwards between them. The outer gates open in sequence whilst the centre gate closes allowing water through from the higher level to drive the carriage along the flume whilst extracting energy by means of a hydraulic pump or similar. Return of the opened carriage gate enables repositioning of the carriage and the commencement of a further cycle.