Carwyn Huw Frost

• PhD. BEng.
• Lecturer at Queen's University Belfast

With many Tidal Energy Conversion (TEC) devices at full scale prototype stage there are two distinct design groups for Horizontal Axis Tidal Turbines (HATTs). Devices with a yaw mechanism allowing the turbine to always face into the flow, and devices with blades that can rotate through 180° to harness a strongly bi-directional flow. As marine turbi...

Extensive Research and Development (R&D) within the tidal energy industry is pushing this sector towards commercial viability, with full scale prototypes starting to meet the challenges of the marine environment. This paper combines velocity data collected from Ramsey Sound (Pembrokeshire, Wales), with Computational Fluid Dynamics (CFD) to assess t...

Tidal Stream Turbines are developing renewable energy devices, for which proof of concept commercial devices are been deployed. The optimisation of such devices is supported by research activities. Operation within selected marine environments will lead to extreme dynamic loading and other problems. Further, such environments emphasise the need for...

The transient interaction between tidal currents and the rotation of a horizontal axis turbine rotor have the potential to induce high asymmetric loadings, which are subsequently transmitted to the drive shaft and potentially high speed drive train components. To mitigate the potential for early component failure, analysis of asymmetric loading on...

Tidal energy is on the verge of commercial viability and full scale prototypes are meeting the challenges of the marine environment. The primary focus of the sector has concerned Horizontal Axis Tidal Turbines (HATTs); comprising a turbine supported by a tubular stanchion operating on a bi-directional, or yaw system. The direction of tidal flow, ho...

A linear potential flow model of a rotating lift-based wave energy converter is developed by assuming that the lift is generated by a pair of equal and opposite circulations and that the amplitude of motion is small. The linearisation of the hydrodynamics means that the forces can decomposed and expressions for the wave excitation force and radiati...

This paper presents a three-dimensional numerical study employing an actuator line model to investigate the effect of turbine solidity on the performance of a Transverse Axis Crossflow Turbine (TACTs). Transverse Axis Crossflow Turbines have a low rectangular form and are ideally suited to relatively shallow tidal and riverine sites due to their ab...

Assessment of the upstream flow available to the tidal energy converters (TEC) is key to evaluate its performance. Simultaneously, TEC technology has been innovating on its concepts and designs to expand the potential sites to harvest energy generated by tidal currents and rivers. The Gkinetic CEFA 12 is an easy-to-deploy device suitable to operate...

The purpose of this study is to demonstrate through towing tank experiments the effectiveness of a novel sensor-less Maximum Power Point Tracking (MPPT) control for Tidal Stream Turbines (TST) under fluctuations of the onset flow. Ocean energies will play a crucial role in the renewable energy sector over the next decades. Instream turbines for tid...

Tidal resource assessment for the characterisation of turbine performance or Annual Energy Prediction currently uses the method of bins as recommended by international standards. An alternative method is proposed in this paper and applied to the Sustainable Marine Energy PLAT-I deployment in Connel Sound, Scotland. This method may be suitable for t...

Transverse Axis Crossflow Turbines (TACTs) are a niche subset of tidal turbines. TACTs are not as well understood as the more traditional horizontal axis turbine and associated flow theory which leans heavily on advances in wind energy and marine propulsion. This paper reviews laboratory and field based experimental fluid dynamics work from the per...

Developing Innovative Strategies to Extract Ocean Wave Energy, or the LiftWEC project, is exploring the potential of using lift forces generated by ocean waves as a source of power. Principal Researcher, Matt Folley, seeks to finally prove waves can make sense as the next big renewable.

Experimental testing of physical turbines, often at a smaller scale, is an essential tool for engineers to investigate fundamental design parameters such as power output and efficiency. Despite issues with scaling and blockage which are caused by limitations in size and flow velocity of the test facilities, experimental tank testing in laboratory e...

Transverse Axis Crossflow Turbines (TACTs) are a niche subset of tidal turbines. TACTs are not as well understood as the more traditional horizontal axis turbine and associated flow theory which leans heavily on advances in wind energy and marine propulsion. This paper reviews laboratory and field based experimental fluid dynamics work from the per...

Tidal resource assessment for the characterisation of turbine performance or Annual Energy Prediction currently uses the method of bins as recommended by international standards. An alternative method is proposed in this paper and applied to the Sustainable Marine Energy PLAT-I deployment in Connel Sound, Scotland. This method may be suitable for t...

The majority of devices designed to extract energy from ocean waves operate through exploitation of the buoyancy (Froude-Krylov) and/or diffraction force regimes. Such devices extract energy through interaction with the displacement and/or acceleration of fluid particle motions respectively. By comparison, very little consideration has been given t...

Representing the velocity at a tidal energy extraction site in a standardized manner is essential for the development of the tidal energy sector. The International Electrotechnical Commission (IEC) have issued a technical specification to determine the mean representative current velocity (MRV) relative to a tidal energy converter (TEC). This metho...

The main objective of this paper is to analyse extreme cases of wave-current interactions on tidal stream energy converters. Experiments were undertaken in the INSEAN tow tank facility where carriage speeds of 0.5 and 1m/s were used with and without waves. The waves studied in this testing campaign had wave heights of 0.2 to 0.4m with a 2s wave per...

The first aim of the research presented here is to examine the effect of turbine control by comparing a passive open-loop control strategy with a constant rotational speed proportional–integral–derivative (PID) feedback loop control applied to the same experimental turbine. The second aim is to evaluate the effect of unsteady inflow on turbine perf...

The sustainable deployment of Horizontal Axis Tidal Turbines will require effective management and maintenance functions. In part, these can be supported by the engineering of suitable condition monitoring systems. The development of such a system is inevitably challenging, particularly given the present limited level of operational data associated...

Inflow turbulence can impact a turbine's power performance and load conditions and also affects wake recovery. At array scale, changes in flow conditions across a site impact the energy yield, performance and load conditions of turbines. Understanding the variation of flow conditions in time and space at deployment sites is therefore important to t...

Load fluctuations caused by the unsteady nature of tidal streams can have severe impacts on turbine components. As seen in the wind industry, turbine blades can become misaligned due to a fault in the pitch mechanism or blade deformations arising over time. These misalignments will represent a loss of power capture and perhaps even premature failur...

The paper presents data from two experimental campaigns at CNR-INSEAN's towing tank in Italy and Strangford Lough tidal test site in Northern Ireland. The experiments maintained identical instrumentation between the campaigns allowing the comparison of steady uniform flow with unsteady non-uniform conditions, respectively. The rotor is a 3 blades d...

Extensive Research and Development have helped drive the tidal energy industry towards commercial viability, with full-scale prototypes starting to meet marine environmental challenges. This paper utilises velocity data collected from a site off the welsh coast with Computational Fluid Dynamics (CFD) to determine the effects of misaligned flows on...

This thesis investigated the non-dimensional performance characteristics of a tidal stream turbine and how they varied in response to changes in flow direction. The problem was considered from an industrial perspective and used the commercial software package ANSYS CFX and a 1:20th scale experimental turbine. Initial considerations analysed the...

This study used computational fluid dynamics to investigate the effect of waves and a velocity profile on the performance of a tidal stream turbine (TST). A full scale TST was transiently modelled operating near its maximum power point, and then subjected to waves both in and out of phase with its period of rotation. A profile was then added to one...

The transient behaviour of the sea and the rotation of a turbine rotor can result in high asymmetric loadings, which are transmitted to the drive shaft. A turbine mounted on a circular stanchion has been used to highlight the effects of introducing more realistic boundary conditions, over a rotational cycle of the turbine. The consequences on the t...