Marine Renewable Energy Industry Research Articles

Towards component reliability testing for marine energy converters

The dearth of generally available, failure data that can be directly applied to marine energy converters (MECs) has been commented on for some years. The advancement of the industry will be fundamentally linked to proven reliability assessments, which is difficult on an industry wide basis. This paper describes how targeted component reliability testing could enable the establishment of relevant failure rate data for the marine renewable energy industry. The necessity of dedicated component testing is briefly reviewed for the wave energy sector together with the experience from other industries. A generic procedure used in test intensive industries for service simulation testing is outlined and applied to wave tank mooring tests. By means of a rainflow analysis procedure and the Palmgren–Miner rule the most severe load cycles, largely contributing to the fatigue damage are identified and reproduced for a possible component test signal. The application of the suggested generic test approach will assist marine energy stakeholders in obtaining evidence of component reliability under simulated operational conditions much more rapidly than can be achieved with prototypes under normal service conditions. Importantly, this would also allow a more accurate estimate of field failure rates and could reveal possible failure modes/design weaknesses ahead of field deployments.

ASSESSMENT OF MARINE RENEWABLE ENERGY INDUSTRY STAKEHOLDER REQUIREMENTS IN NORTH SCOTLAND

This paper describes two marine renewable energy stakeholder workshops in North Scotland that were held in March 2009 to discuss industry requirements for developing the Pentland Firth and Orkney waters between Scotland's north coast and the northern isles. This is an area of considerable interest for the development of renewable energy in Scotland. If the area is developed (mainly with wave and tidal power) it could make a significant contribution to both meeting government renewable energy targets and to the local economy. However, following accelerated applications by developers for site leasing, development of the area was delayed by uncertainty in environmental data shortages and subsequent slow progress in government formulation of marine spatial planning policy. In order to proceed, the marine renewable energy industry in Scotland required timely investment in regional infrastructure and a clear policy direction from government. Energy industry stakeholders who attended the workshops called for a single authority to take responsibility for both regulation and direct investment from government so that national renewable energy targets could be met in the required timeframe. Ultimately, government and policy makers were expected by industry to take responsibility for this with a central authority to decide and importantly communicate where and when marine turbines could be built. This required by government a proper understanding of the resources and not just the constraints in identifying the most suitable areas. Local knowledge in the community offered to dispel some of the uncertainty regarding the physical environment in a way that could also guide policy and perhaps accelerate marine spatial planning in designating workable areas for wave and tidal power.

Is there a conflict between cetacean conservation and marine renewable-energy developments?

There is currently an unprecedented expansion of marine renewable-energy developments, particularly in UK waters. Marine renewable-energy plants are also being developed in many other countries across Europe and in the wider world, including in the USA, Canada, New Zealand and Australia. Large-scale developments, in UK waters, covering thousands of square kilometres are now planned; however, data on the likely impact of this expansion on the 28 cetacean species found in UK waters are lacking, or at best limited. However, the available information, including inferences drawn from the impact of other human activities in the marine environment, indicates a significant risk of negative consequences, with the noise from pile driving highlighted as a major concern. The marine renewable-energy industry will also deploy some novel technologies, such as large submerged turbines, with unknown consequences for marine wildlife. Further research is urgently required, including distributional and behavioural studies, to establish baselines against which any changes may be measured. Precautionary actions, particularly with respect to pile driving, are advocated to minimise impacts on cetaceans.

Demonstrating survivability of marine energy converters

The marine renewable energy industry is in its infancy with many developers currently undertaking research, development and demonstration activities to prove that their fledging technologies will provide a viable form of energy generation. Given the very nature of the technology and resource, they will generally be deployed either at the highly dynamic sea surface, or submerged many metres under water, or both. In either case, imposed environmental loads can be significant whereas access for inspection and maintenance activities could be limited due to harsh weather and sea conditions. Therefore it is essential that these technologies are developed and designed to survive these aggressive conditions for the whole of their operational lives, with a very low level of planned and unplanned inspection and maintenance interventions – and this requires the consideration of the ‘survivability’ of the ‘marine energy converter’ during design development. There is a clear ‘blueprint’ in place for all developers to follow in order to approach and demonstrate the survivability of their technology, which is based on the use of modern analysis techniques, such as ‘failure, modes, effects and criticality analysis’, together with traditional engineering design principles and procedures. This paper elaborates this blueprint further.