Research Projects
Present Research Activities
- Tidal Stream Turbine Arrays: Experimental Study
- Simulation of Unsteady Loading of Tidal Stream Turbines
- Wave Energy Devices: Arrays & Extreme Loading
- Manchester Bobber
- EQUItable appraisal of MARine Energy, EQUIMAR, EU FP7
Small farms of horizontal axis tidal stream turbines are presently being studied2 in the wide- wave and current flume. The configuration of each device is similar to a two-bladed wind turbine but with blade design adjusted to suit the small scale of the experiments. The project addresses the effect of free-surface and device-proximity on the power output of individual devices and the wakes of multiple devices.
This is part of an Energy Technologies Institute project “Performance Assessment of Arrays of Wave and Tidal devices” (PerAWAT) which also involves Garrad Hassan, Electricité de France, EoN, University of Oxford, University of Edinburgh and Queens University Belfast.
Although average tidal stream velocities can be accurately predicted, high velocity tidal flows are unsteady due to both large-scale turbulence and waves. It is important to understand the effect that unsteady flow has on both power output and device loading since both influence device design and viability.
Preliminary studies have been conducted of unsteady loading of a porous disc model of a device subjected to unsteady incident flow indicating large fluctuations of horizontal load and modification of wake structure. Ongoing numerical work involves resolving the rotor of a rotating three-bladed turbine, modelling combined current and wave loading and simulating deformation of the free surface in the vicinity of a device. Device simulations are conducted using CODE_SATURNE and the work is presently funded by EdF.
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Several ongoing research projects address the response and power output of wave energy devices with a particular focus on closely spaced arrays.
Experimental work conducted in the wide-wave-current flume has recently provided measurements of individual device response when subject to extreme waves and the response of arrays of devices due to both regular and irregular wave conditions. Under EPSRC grant EP/D077036/1, measurements of response to focused waves are compared to computational models to improve understanding of the most appropriate tools for modelling wave device design loads. Studies of array interactions focus on closely spaced arrays of heaving floats to understand how hydrodynamic interactions influence device design. Numerical models of arrays, principally based on linear hydrodynamics (e.g. WAMIT), have been evaluated against measured responses and are presently being used to improve understanding of the optimal power output from arrays of non-identical floats in regular waves.
Experimental measurements have improved understanding of power interaction factors in both regular and irregular waves.
The Manchester Bobber wave energy device comprises a rectilinear array of shallow draft floats that oscillate vertically (in heave) when subjected to wave excitation. The motion of the float drives a clutched flywheel and rotational generator. Each float is constrained to oscillate in heave only by a system of horizontal tethers. Experimental studies have addressed:
- Power output from a single device – used to validate numerical models
- Response of a single device to severe wave loading
- Variation of device response and power capture when deployed in closely-spaced arrays.
Experimental research on this device has involved the development of a set of 25 identical drive-trains which provide accurate scale model of an induction generator. Each drive incorporates a friction compensated dynamometer system that allows specification of unique generator characteristics for each drive-train. Use of this system is beneficial for analysing wave device arrays as it ensures that all floats are subject to identical mechanical constraint. Time-varying mechanical constraint (i.e. a torque-speed curve) is specified for each generator to replicate alternative control systems.
EQUIMAR is a 22 partner EU project focusing on the development of a suite of protocols for the equitable evaluation of both wave and tidal stream devices. The protocols are intended to harmonise testing and evaluation procedures to facilitate inter-comparison of the wide variety of devices that are presently in development. University of Manchester contributes to the development of methods for assessing the economic viability of large scale marine energy projects.
Recent work includes evaluation of support structures for wave or tidal stream devices and studies of the time available for installation of marine energy projects.