Synergies for a Wave-Wind Energy Concept

Introduction
In recent years, with more and more offshore wind farms being constructed, the question arises as to the possibility of integrating other marine renewables with offshore wind. This integration presents a number of advantages, including a better utilisation of the marine space and lower installation costs relative to separate installations. Therefore, new hybrid or multiplatform solutions are being developed.

Approach
This work is focused on the integration of Wave Energy Converters (WECs) into offshore wind farms. Furthermore, the sustainable development of both offshore wind and wave industries requires a proper use of the natural resources, optimizing their exploitation where present. And it is in relation to this and on the shared challenge for both in reducing cost that the option to integrate these energies arises.

Main body of abstract
Accordingly, the paper first goes into the positive synergies when offshore wind and wave energy technologies share the same marine space. Among that ones are: shared cost; a smoothing power output; and shielding effects of WECs over the offshore wind farm, which contribute to increase the weather windows for operation and maintenance.

Secondly, this work outlines the risks and challenges that arise when combining these energies. To some extent WECs increase the uncertainty of the project, leading to a higher project cost and an increase the associated financial risk.

In third place three case studies are proposed to illustrate different possibilities of a combined wave/wind array. Different types of WECs are considered together with various array configurations, such as: co-located wave and offshore wind turbines, i.e. the WECs are located at the outer rim of the wind farm; hybrid energy converters, i.e. both technologies share the same structure; and a combination of the two previous cases.

Conclusion
Finally, a complete overview of these three cases is evaluated based on the following parameters: initial and life time savings, shared costs, power production and risks.

This work is the result of a collaborative task proposed by DONG Energy at the 6th annual INORE symposium held in Denmark in May 2012. INORE is the International Network in Offshore Renewable Energies, a world-wide network that brings together researchers on offshore renewable energies.