Wind park repurposing

In Europe, 65 offshore wind parks will need to be re-powered, upgraded, or decommissioned, in the next 20 years.[1] The first decommissioning project began in 2016, and in the North Sea alone, decommissioning costs are expected to reach between €80 to €100bn over the next 25-30 years.[2] Costs of decommissioning, which include environmental and technical challenges, fall on the current wind parks' owners.[3]

Installing wave energy systems is an opportunity to offset the cost of decommissioning by re-purposing the wind parks' infrastructure. Wind parks already have crucial electrical cables buried under water, and strong structural foundations. Leaving these intact can offset the costs, and damages to the seabed associated in their removal.

The best conditions for exploiting wave as an energy resource are found in deeper waters (more than 40m), where power densities can reach 60–70 kWh/m^3. In the European north-eastern Atlantic (including the North Sea), the available wave energy power resource is about 290 GW/year.[3] Wave energy systems are designed to work with waves of 6-8m, but waves with a height of 1-5m constitute 85% of the available resource globally. Therefore, innovation to enhance performance at lower sea levels is crucial for application at decommissioned wind parks. The potential global market for this technology is 500 GW, with annual electricity sales of about €50bn.[4,5]

While the offshore wind industry focuses on setting up new projects, the decommissioning phase has thus far received little attention.

When will the installation of wave energy systems at decommissioned offshore wind farms become accepted practice?

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References:
[1] Ospar Commission (1992), Convention Text
[2] World Energy Council (2017)
[3] Cipollina A., Micale, G. and Rizzuti, L. eds., (2009), Seawater desalination: conventional and renewable energy processes.
[4] International Renewable Energy Agency (2014), Wave Energy Technology Brief.
[5] This number is an own calculation based on a (1:1) relationship between the prices of electricity produced from wave energy and wind energy. The assumptions are 500GW of production, production efficiency of 40%, wave energy plants working for 24 hours all year round (no maintenance), and no change in price from other sources of energy. The number is an average of three assumed equally likely scenarios of the future equilibrium price of electricity from offshore installations in the North Sea (no change, exponential, power function). The future price is calculated from the development of prices of the years 2011 and 2017 for offshore wind park production in the North Sea.
More information:
Margheritini, L.; Hansen, A.M.; Frigaard, P. (2012), A method for EIA scoping of wave energy converters—Based on classification of the used technology.
Cruz, J. (ed.), (2008), Ocean Wave Energy: Current Status and Future Perspectives
Brooke, J. (2003), Wave Energy Conversion, Volume 6 1st Edition

By Matthew J. Spaniol