CAMREG KEYSTONE PROJECTS
Theme 3: Multifunctional materials for energy applications
KP9- Morphing aero- and hydro-dynamic working surfaces.- Prof Feargal Brennan University of Strathclyde & Dr. Ignazio Maria Viola UoE Engineering
The project aims to investigate novel working surfaces to enhance the durability of wind and tidal turbines. In particular, one of the main cause of failures of the blades are the unsteady loads, which are due to both the environmental flow (turbulence, shear in the onset flow velocity profile, etc.) and to the rotation of the rotor. Hence, the focus of the project is to develop novel technology that will enable the mitigation of unsteady loadings. The project includes the Universities of Edinburgh (Viola) and Cranfield (Brennan), as well as SRI International in California, US.
KP10 – Dielectric elastomers for power take-off. - Dr. Aristides Kiprakis UoE Engineering & Prof. Feargal Brennan University of Strathclyde
Conventional electromagnetics-based generation operates with high rates of change of flux linkage brought about by intense field strengths and high speeds of rotation. Ocean waves deliver high reciprocating mechanical forces at low speeds thereby making the electro-mechanical interface of the converter particularly challenging to design, considering the dynamic characteristics of the resource and the environment. Existing technologies suffer from low reliability and long-term survivability of components in the harsh ocean operating conditions. Additionally, controllability of existing WECs is universally poor, as they are matched to a specific, and generally narrow range of sea states, while operation and protection from extreme conditions also requires advanced control techniques and additional safety mechanisms. Dielectric Elastomers (DE) have been proposed as a direct conversion PTO mechanism with minimal number of moving parts and excellent potential for control. Use of deformable electroactive composites, driven either by wave-driven air columns or, more interestingly, by the direct motion of the seawater, avoids the need for end-stops, speed increase, or mechanical control and appears to offer excellent scalability. This KP will explore existing and design new materials, configurations and processes of ‘synthetic muscles’ for elastomeric electricity generation to optimise the mechanical response of the working surfaces. Specifically, collaborative work with SRI International will be focused on the design of the synthetic muscle and on real-time active control to optimise the response of the converter for the given wave climate. Successful completion of experimental work will lead to an opportunity to upscale existing physical models and/or test them in array configurations, and moreover, the possibility to combine the outputs of this KP with results from KP11 to develop a unified PE-only WEC system.
KP11 – Programmable flexible materials for mooring and station keeping. - Prof. Margaret Stack and Prof. Feargal Brennan University of Strathclyde
The moorings of wave devices, floating tidal turbines and ultimately floating offshore wind turbines will be subjected to the combined excitations of hydrostatic, hydrodynamic, aero-dynamic and electromechanical forces driven by a combination of wave, tidal, wind and network interactions. The performance and structural responses of the energy converters are influenced by the behaviour of the moorings (particularly if bio-fouled). Existing moorings are either passive or adaptive based on extension or articulation. This KP proposes to investigate the potential of programmable flexible materials to provide adaptive behaviour and improved, sympathetic mooring response. The research work will build upon the knowledge of dynamic mooring systems to create a definition of adaptive strain/stiffness. The performance of active and passive hydro-elastic materials will be investigated and some small-scale wet and dry trials will be conducted. The challenge is truly adventurous and if successful could allow the development of compliant offshore structural concepts which are not presently possible.
Specifically, CAMREG would begin to examine the required performance characteristics of dynamic mooring systems and create a global model so that local adaptive strain/stiffness requirements can be defined. Smart material solutions would then be investigated in tandem with mooring design analysis. In this way it would be possible to define the elements and capabilities required for a larger collaborative initiative to fully explore the potential for programmable flexible materials for mooring and station keeping.
KP12 – Damage tolerant and self-repairing structures. - Prof. Margaret Stack and Prof. Feargal Brennan University of Strathclyde
Large structures used for energy applications tend to be relatively damage tolerant and the volume of materials used inherently means significant amounts of defects are present from the outset. The aerospace industry has in particular, developed the concept of providing “hard regions” and segmentation of structural areas so that fatigue cracks cannot propagate unhindered along a major structural element. Pipelines too, utilise “crack arrestors” to contain cracks otherwise they might run for kilometres with catastrophic consequences.
This KP aims to build on the idea that materials can be locally hardened/stiffened/toughened through a combination of surface treatments (e.g. laser or ultrasonic peening) to “control” progressive damage. It might be possible to reintroduce resistance to fatigue crack initiation through reworking or applying such treatments in the field potentially effectively providing an infinite fatigue life in a manner not dissimilar to biological material systems. It KP involves the design of materials and structures to support not only primary purpose but also to consider failure from the outset. This includes “design for inspection and maintenance” as well as “controlled failure design”. The former is to ensure materials are responsive to inspection and structural health monitoring whereas the latter is concerned with ensuring a material and its structural design considers failure and if possible to ensure it does so minimising the consequence. The findings of the KP could have applications across a range of energy materials in offshore structures and drive train and turbo machinery components and transmission infrastructure. The concept would work in tandem with structural health monitoring and advanced sensor systems of the type described earlier and close the structural integrity loop through the self or remotely applied repair. One significant application would be chosen to examine the failure control methods which might be applicable and then to model using non-linear numerical methods an effective failure control/arrest scenario. In the same way a self-repair system can be examined and applied to the same application. This would provide understanding of the potential of damage tolerant and self-repairing structures and wider collaboration.