Document Type

Theses, Ph.D

Rights

Available under a Creative Commons Attribution Non-Commercial Share Alike 4.0 International Licence

Disciplines

Electrical and electronic engineering, Ocean engineering

Publication Details

Successfully submitted for the award of Doctor of Philosophy to the Technological University Dublin, April, 2015

Abstract

Wave energy is an emerging industry and faces many challenges before commercial wave energy converter (WEC) arrays are installed. One of these challenges is the grid integration of WEC arrays. This includes offshore electrical networks, grid compliance, and access to electrical markets. This must be achieved in a technically viable manner and also at an acceptable cost. As electrical networks are expected to make up a large proportion of the overall WEC array CAPEX, perhaps up to 25%, this area is critical to the long term competitiveness of wave energy.

The objectives of this thesis are to develop technically and economically acceptable electrical network designs for WEC arrays, evaluate voltage flicker issues for WEC arrays and develop design tools to analyse same, and evaluate the market scale for wave energy in Ireland, considering electrical integration issues in both the domestic and export markets.

This thesis presents the optimum design for WEC array electrical networks. By building from the industry state of the art, including offshore wind experience, a comprehensive techno-economic optimisation process is undertaken. This includes optimising the key electrical interfaces between the WEC and the array electrical network, optimising the array network configuration, assessing efficiency of the network, and demonstrating that the network can be achieved at a cost which will allow competitiveness. Some challenges to the economics of WEC array electrical networks and some strategies for improving the economics are presented in this research also. The results provide timely guidance to WEC and WEC array developers.

This research also demonstrates the critical link between voltage flicker emissions from WECs and the primary resource, i.e. ocean waves. Some practical assessment tools for the evaluation of this power quality issue are shown to assist in quantifying the problem. Also the full flicker performance of a candidate WEC is assessed helping characterise this link further.

In this thesis both the domestic and export markets for Ireland’s wave energy resource are assessed as, although Ireland has an enviable wave energy resource, it is unclear where the market for this resource lies. This analysis shows that the medium term market for wave energy in Ireland is an export market. Also, although technically feasible, there is an additional cost for export transmission which must be considered in evaluating export markets.

Some of the critical grid integration issues have been evaluated and addressed in this thesis. Future work is recommended in the areas of weather risk to cable installation at high energy wave sites, evaluating the benefits of shared electrical infrastructure across a range of renewable projects, designing offshore substations for WEC arrays, and quantifying the benefits of the addition of wave energy to the Irish renewable energy mix.

DOI

https://doi.org/10.21427/D7VG7F

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