The LHEEA research department of Ecole Centrale De Nantes – CNRS has been working on energy ships for far-offshore wind energy conversion since 2016. This concept didn’t receive much attention until 2000s e.g. Tsujimoto et al. and Platzer & Sarigul-Klijn in 2009, and Kim & Park in 2010. In 2017, Gilloteaux & Babarit were the first to propose the use of autonomously-sailing energy ships. In total only a few concepts have been proposed. Yet, no experimental proof-of-concept has been built. Thus, the energy ship concept is still in the very early stages (TRL is 2 “Technology concept formulated”).
Scientific advances and innovation
So far, arbitrary values have been assumed in studies on energy ship concepts for the capacity factor. For example, a value of 55% was considered in Kim & Park, 2014. To our knowledge, the only study which considered weather-routing for the capacity factor optimization is by Tsujimoto et al., 2009. However, they considered a sailing wind farm and not an energy ship. The sailing wind farm is slow and has poor maneuvering capabilities which lead to a capacity factor of only 42.6%. In the WEREVER_OPTIROUTE project, we consider energy ships which are fast and have high maneuvering capabilities as was shown in Gilloteaux & Babarit, 2017. These features are expected to lead to high capacity factors (as indicted by the preliminary results of Simoneau, 2017). This will be shown in this work for realistic conditions which will be the advance of the state-of-the-art provided by the project.
Expected technical and economic impact
The hydrogen-producing autonomously-sailing energy ship is a new concept for wind energy harvesting in the far-offshore. The energy ship consists of a wind driven ship towing a water turbine. The electricity produced by the water turbine is converted to hydrogen for on-board energy storage. When the hydrogen tanks are full, the energy ship sails to a shore-based terminal for unloading the hydrogen. Then, it goes back to the far-offshore and start a new charging cycle.
The energy ship concept is complementary to grid-connected bottom-fixed or floating wind turbines. Indeed, in contrast to energy ships, such wind turbines cannot be deployed in the far-offshore because of the grid-connection and moorings costs. Moreover, energy ships are mobile platforms. Therefore, they can be weather-routed towards the most favourable meteorological conditions. This feature may lead to capacity factors much greater than for other renewable energy sources.
The aim of the WEREVER_OPTIROUTE project is to evaluate and optimize this capacity factor for realistic conditions in terms of deployment areas and exploitation duration. It requires the development of new weather-routing algorithms dedicated to energy ships concepts.
Key project milestones
- April 30, 2017 - Project start date
- August 31, 2017 - End date