New research in tidal current energy

AbuBakr S. Bahaj

In order to meet our aspiration for energy security, reducing dependence on finite and polluting fossil fuels and to combat climate change, we need to exploit as many of the available natural and sustainable resources within our planet as possible. The oceans, which cover more than two-thirds of our planet, offer an incredible store of energy. One of the forms of energy within our oceans is that resulting from the gravitational effects of the planetary motions of the Earth, the Moon and the Sun, which produce the tides that drive strong marine currents. The kinetic energy present in marine currents can be converted using technologies not too dissimilar to those used in wind energy. While technologies harnessing energy from the tides and currents have been discussed for many years, it is evident from recent deployment of single devices at megawatt scale that real progress has been achieved in a very short period of time. This progress is the reason that tidal current energy is frequently referred to as an emerging technology that has the potential to successfully augment existing renewable energy technologies.

Although the potential for marine energy conversion clearly exists, the technology is presently still in a pre-commercial phase and only a handful of devices have so far been tested at full scale in the ocean. Unlike wind energy, there are currently various designs being promoted, with no single device design emerging as a winner so far. In addition, there are many aspects of the technology requiring various optimization and design improvements, as well as in situ experience in operation and maintenance. Therefore, in order to develop marine energy technology, deployment pathways will need to be at the multi-megawatt array level. In order to facilitate this, and in the absence of real site performance, small-scale research and development studies are underway that are geared to inform optimized site array designs, including consideration of wakes, the influences of turbulence and their impact on device spacing. This is the reason why there is a large amount of high-quality academic research presently being carried out at leading international research institutions, with the main aim of optimizing the technology and its deployment and to thereby rapidly advance marine current or tidal energy itself.

The purpose of this Theme Issue is to contribute to this knowledge. It comprises an elite selection of articles within the marine current energy conversion area. The idea for it was conceived during the 9th European Wave and Tidal Energy Conference (EWTEC-2011) held in Southampton, UK, in September 2011, the world's largest and most renowned academic conference in this field. The high quality of the research articles submitted for this conference prompted the wish to dedicate an entire Theme Issue to the topic, detailing the focus of the current research. The best papers were selected by the conference's technical programme management and further developed by the authors to fit within the framework of this Theme Issue.

The research presented here covers the key focal points of the international research, such as turbine design, performance and optimization, tidal resource assessment, array design and wake interactions, while the methodology of the work encompasses numerical modelling, experimental studies as well as field measurements.

Acknowledgements

I would like to thank our colleagues and authors for their excellent work and their readiness to promptly address reviewers' comments to allow publication to progress as planned. I would like to thank my colleagues in the local Technical and Management Committees of the conference who were instrumental in the compilation of this issue and with additional special thanks to the overall EWTEC Technical Committee.

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