Photo: The Edinburgh Tidal Array used for testing at FloWave (Courtesy of the University of Edinburgh)

Research challenges traditional rules for tidal array layout design

A team of engineering researchers from two UK universities have conducted a study which showed that arranging tidal turbines in a close formation, as opposed to wider spacing, results in an increased power capture.

Photo of the Edinburgh Tidal Array used for testing at FloWave (Courtesy of The Universtiy of Edinburgh)
The Edinburgh Tidal Array used for testing at FloWave (Courtesy of the University of Edinburgh)

The team, led by Aristides Kiprakis from University of Edinburgh’s School of Engineering, carried out physical tests at Flowave Ocean Energy Research Facility as part of the study that challenges the rules which currently govern the layout of tidal turbines.

The team’s experimental methods and findings will be useful for further scale-testing of turbine arrays elsewhere, for refining computer models of arrays and for assessing their performance taking into account factors such as forces exerted on the turbines by sea waves, according to the researchers from the University of Edinburgh and the University of Manchester who conducted the study.

Kiprakis said: “Existing empirical rules in tidal array layout design dictate that the separation between units should be in the order of 10 to 15 rotor diameters. Modern tidal turbines have rotor diameters upwards from 20 m, meaning that the distance between neighbouring machines can be several hundreds of metres.

“Our findings show that this should not necessarily be the case; a closely spaced array will potentially increase energy yield and profit, while at the same time will allow the developer to make a more efficient use of the seabed, and reduce the cost of the offshore grid, compared to an installation with more typical 10–15 diameter spacing between rows of turbines.

“The resulting lower ‘Levelised Cost Of Electricity (LCOE)’ will make tidal arrays more competitive, bringing them one step closer to wide-scale deployment”.

An array of three tidal turbines installed in the FloWave tank during experiments (Courtesy of the University of Edinburgh)
An array of three tidal turbines installed in the FloWave tank during experiments (Courtesy of the University of Edinburgh)

The research findings have been revealed in a paper titled ‘Experimental Assessment of Flow, Performance and Loads for Tidal Turbines in a Closely-Spaced Array’. The paper has been published in the open-source peer-reviewed MDPI Energies journal, and recently won an Editor’s Choice Award.

The research was funded by the UK Engineering and Physical Sciences Research Council (EPSRC) through the SuperGen UK Centre for Marine Energy Research, and project FloWTurb: Response of Tidal Energy Converters to Combined Tidal Flow Waves and Turbulence.