The potential of the water hammer in pico-scale tidal power systems: an experimental investigation

The tidal energy within the seas surrounding the United Kingdom offers a vast renewable resource that is perfectly predictable over long timescales. Currently, the bulk of tidal energy research is focused on developing large devices for the most resource rich locations, which can be many miles from populated areas. The potential of small-scale tidal power from sub-optimal shallow water sites, close to populated regions, has so far been overlooked. Such generation would benefit from reduced transmission losses and contribute towards a distributed electricity grid, helping to overcome the variability of other renewables. This work presents a novel method for generating hydropower using the water hammer effect: a pressure surge that can occur in a pipeline following the abrupt closure of a valve. These pressure surges are used to produce vertical oscillations from horizontally flowing water, allowing power to be generated in a manner analogous to a wave energy convertor. A non-optimised scale model was found experimentally to have a peak available power density of 1.08 ± 0.25 kW/m2 and a mean of 0.07 ± 0.02 kW/m2. In comparison, the MCT SeaGen S (arguably the most well-developed tidal energy device) is capable of generating 3.18 kW/m2. With further development, a water hammer device may therefore be useful for generating pico-scale tidal power in slow, shallow water flows