Experimental and numerical modeling of a vertical axis turbine for gravitational water vortex power plant

Because of an ever-growing concern regarding the environmental issues, demand for efficient and cleaner energy sources are rising. One solution to answer this need is to develop technologies such as gravitational water vortex power plants to harvest the untapped energy from many rivers and canals. This system is composed of a cylindrical basin where a bathtub vortex is created via a drainage hole at the bottom of the tank. The kinetic energy from the bathtub vortex is then harvested by a vertical axis turbine. This technology is simple in design and only requires a very low head (0.5 to 2 m). These advantages make gravitational water vortex power plants good candidate for wave energy conversion applications and offshore electricity production in remote locations. Despite several research on this field, this technology remains at a preliminary stage and numerical models are not readily available to accurately predict the power output. The present study aims at developing such a model. To do so, an experimental setup is developed. PIV measurements with and without the turbine are performed. Results show that the flow is mainly irrotational and provide linear relationships between upstream vortex intensity and water height in the system at constant flow rate. A numerical code based on potential flow theory is developed. While the model overestimates power output by up to 160% under lightly loaded conditions, it demonstrates good predictive accuracy for moderate to high loads, with relative errors remaining below 15%.