Venturi-enhanced hydropower

Generation of electricity from elevated water sources has been the subject of much scientific research over the last century. Typically, in order to produce cost-effective energy, hydropower stations require large flow rates of water across large pressure drops. The pursuit of low head hydropower is largely avoided because turbines which deal with large flow rates are very expensive. Thus, regions of relatively flat land, such as large parts of the UK, miss out on hydropower due to the lack of sufficient elevated water sources.

During my DPhil at Oxford, I worked with VerdErg Renewable Energy on the mathematical modelling and optimisation of a novel type of small-scale hydropower. Tailored for river/tidal situations where there is a small drop in pressure head, it remains cost-effective by exploiting the Venturi effect. It does so by allowing the majority of the flow to bypass the turbine, whilst converging to a faster, low pressure stream, thereby ‘sucking’ the rest of the flow through the turbine which experiences a much larger pressure drop. In this way the turbine remains relatively cheap because it deals with the minority of the flow, whilst a high power is maintained via the amplified pressure drop. Other advantages include the low environmental impact on aquatic life, since the majority of the flow avoids the turbine, passing through a section with no moving parts.

The efficiency of the hydropower depends upon the mixing of the fast and slow flows in a closed channel. In particular, the shape of the channel has an effect on how the flows mix and therefore the resulting amount of power generated [1-3]. During my DPhil project [4] I used particle image velocimetry experiments (shown to the bottom right), in conjunction with simple mathematical models for the flow, to study the optimum shape of the Venturi that generates power most efficiently.

[1] Benham, G.P., Castrejon-Pita, A.A., Hewitt, I.J., Please, C.P., Style, R.W. and Bird, P. Turbulent shear layers in confining channels. Journal of Turbulence, 19.6, 431-445, (2018).[pdf]

[2] Benham, G.P., Hewitt, I.J., Please, C.P. and Bird, P. Optimal control of diffuser shapes for confined turbulent shear flows. Journal of Engineering Mathematics, 113, 65-92, (2018).[pdf]

[3] Benham, G.P., Hewitt, I.J., Please, C.P. and Bird, P. The effect of swirl on confined co-axial flow. arXiv preprint arXiv:1805.02961. (2018).[pdf]

[4] Benham, G.P. Mathematical modelling and optimisation of Venturi-enhanced hydropower, DPhil Thesis, 2018. [pdf]