Wave energy converters (WECs) are built to extract wave energy. However, these devices remain expensive for commercial utilisation. One possible solution to this is to cut down the cost of WECs by sharing the construction-cost by combining a WEC with a breakwater. Here, an integrated WEC-type of breakwater (WEC-B) system is proposed, however this system is still in an immature phase and under development. This project aims to develop the WEC-B system to be more efficient and resilient.

To analyse and evaluate the performance of WEC-B systems, stable and accurate numerical method is necessary. This project uses the software, OpenFOAM®, to analyse wave-structure interaction issues in the WEC-B system. OpenFOAM® is a C++ toolkit of classes for writing computational continuum mechanics codes. Navier-stokes equations are used as governing equations for CFD simulations in this project.

Based on the appropriate CFD method, this project will continue to implement following investigations to develop WEC-B systems:

1. Optimise existing concept of the WEC-B system. The dimension of breakwater structures and layout of the WEC-B system can be regarded as the key parameters which may influence the hydrodynamic performance of the WEC-B system. Parametric investigations will be conducted based on these parameters.

2. Investigate the survivability of the WEC-B system. Several phenomena, including gap resonance and Bragg resonance, as well as storm conditions should be considered according to the future investigation. These phenomena will be highlighted in the chapter of literature survey. Extreme conditions and how they influence the survivability of the WEC-B system structures will be discussed.

3. Propose new concept of the WEC-B system and evaluate the performance. New forms of integrated WEC-B system combining different type of WECs with breakwaters will be proposed based on the experience of the optimisation of existing WEC-B breakwater concept and the literature review. The performance of the new concept will be predicted and compared with the optimised system that have been studied in the studies earlier.

Science

This research will develop OpenFOAM® with more new modules so as to better simulate the WEC and breakwater devices. By investigating the performance of WEC-B systems, multiple new hydrodynamic phenomena of waves interacting with multiply structures, such as gap resonance of floating structures and Bragg resonance of floating structures, will be analysed and studied deeply.

Based on current research, part of the results have been published in following papers:

Ding, H., Zang, J., Blenkinsopp, C., Ning, D., Zhao, X., Chen, Q. and Gao, J., 2019a. Numerical investigation of the performance of a pile-restrained WEC-type dual-floating breakwater system. The 34th International Workshop on Water Waves and Floating Bodies, 7- 10 April 2019, Newcastle, Australia.

Ding, H., Zang, J., Ning, D., Zhao, X., Chen, Q., Blenkinsopp, C. and Gao, J., 2019b. Evaluation of the performance of an integrated WEC type of breakwater system. the 38th International Conference on Ocean, Offshore & Arctic Engineering, 9-14 June 2019, Glasgow, Scotland, UK.

Impact

The development of WEC-B systems is a possible way to share the construction-cost between WEC devices and breakwater devices. With reduction of cost of the WEC technology, the huge storage of wave energy can be utilised commercially in the future. This utilisation of renewable energy technology will contribute to reduce the pressure of energy depletion and climate change. In addition, the concept of multi-functional system can also save the space for the installation of offshore structures, which is important for small island countries and cities with restricted construction-space.

This is the PhD project of Haoyu Ding from the Department of Architecture & Civil Engineering. Email address: H.Ding@bath.ac.uk