Shaping array design of marine current energy converters through scaled experimental analysis

• Published in: Energy (Oxford) 2013-09, Vol.59, p.83-94
• Main Authors: Bahaj, A.S., Myers, L.E.
• Format: Article
• Language: English
• Subjects: Actuator disks; Applied sciences; Array; Arrays; Channels; Computational fluid dynamics; Computer simulation; Converters; Design engineering; Devices; Direct power generation; electricity; Energy; energy conversion; Energy of waters: ocean thermal energy, wave and tidal energy, etc; Exact sciences and technology; farms; Marine; Marine current energy converters; Natural energy; renewable energy sources; rotors; Tidal power; Turbine; Turbines; Turbulent flow; Wake; Wakes
• ISSN: 0360-5442; 1873-6785
• DOI: 10.1016/j.energy.2013.07.023

Marine current energy converters or tidal turbines represent an emerging renewable energy technology that can provide a predictable supply of electricity. Single devices are in operation around the world with aspirations to deploy farms or arrays of multiple devices. We present an experimental study that has characterised the downstream wake flow around a 1/15th-scale turbine in a large circulating water channel and a series of experiments involving static actuator disks at 1/120th-scale allowing simulation of multiple-device layouts. Our analysis demonstrates that the near wake is highly turbulent with structures generated by the rotor and support structure. This region of flow may prove difficult to numerically simulate with a high degree of accuracy. In the far wake the performance of static actuator disks can be matched to mechanical rotors reducing scale and cost facilitating replication of complex array geometries. Here the ambient turbulence and geometric properties of the device/channel drive the wake recovery towards free stream conditions. Devices operating downstream of others will be subject to a non-steady flow field making comparative performance difficult. We discuss the possibility of unequal device specification and rated power within an array (unlike wind farms) providing a more representative measure of array performance. •1:15th-scale tidal turbine experiments conducted.•High resolution flow mapping of downstream wake.•Identified different drivers for near and far wake recovery.•Demonstrated static models can be used to replicate flow around larger rotating turbines.•Postulated that turbines in an array might benefit from non-identical designs (as opposed to offshore wind farms).