Tidal array cost reduction: Testing a removable nacelle design for DeltaStream Technology

Lead Research Organisation: Cardiff University
Department Name: Sch of Engineering


The tidal renewable energy sector is at a stage where it is going to expand with larger devices and arrays of devices. An estimation of nearly 4GW of installed capacity by 2020 is likely by 2020, enabling the sector to make a serious contribution to the energy requirement. Moving the sector forward from its current infancy still requires evelopment of fundamental aspects of the technology in order to provide greater cost efficiency. One particular area is to significantly reduce the cost of deployment and recovery for maintenance. Given the harsh environment in which the devices are deployed and the costs associated with the vessels, the speed of recovery is essential to reducing the life costs associated with the energy generated over a device lifetime.

Hence the urgent need to reduce the installation and maintenance costs of the DeltaStream system. The current project proposes an effective wet-mate nacelle removal system for cost-effective installation and recovery.

Cardiff University will assess the lifting dynamics involved in lowering the turbine from the surface of the sea onto the structure and evaluate the connection aspects of the novel design of the Deltastream. Integrated with physical testing by the project partners, the data will provide feedback to the industrial partner to assess any modifications needed to the proposed design

This Work Package focuses specifically on the modelling the dynamics of lowering the turbine from the surface of the sea into the wet-mate socket. Specifically Ansys software will be used for the modelling. The outputs of the workpackage will also provide feedback to the component testing and final device assembly undertaken as part of the overall project.

Planned Impact

The collaboration between industry and academia will provide an effective partnership for the research and development of wet-mate system which will help drive down the cost of deployment and recovery of the turbine, hence the cost of the energy generated. The implementation of this design into the Deltastream device will provide a major advancement in the technology. The gravity mounted system already allows for reduced deployment costs, the ability to remove/replace a turbine within the short window of opportunity provided by the harsh environment will further drive down the cost of generating electricity. The speed of replacement will also ensure the security of supply (of electricity) when maintenance is required, which in turn will ensure the growth of this sector. The follow on is the development and security of the supply
chain; Ultimately job creation in the UK.

Key areas of impact of this work will be as follows:
Academia: Where data gathered in the project is free of commercial sensitivity, it will also be shared with the academic community for application to research activities related to other significant projects in the marine and maritime sectors. The research assistant will benefit from the direct contact with the industrial partners and active involvement with an industrial scale development. Attendance at a conference will allow for networking and discussions with leading experts in the marine energy research and development.

Device designers: The UK is the world leader in the area marine energy, specifically with the development and deployment of devices. The development of the technology described in this proposal will have a significant impact on the developer and accelerate the deployment of the first array of the Deltastream devices. As with most investors the risk and payback are vital, so a reduction in both the risk and the payback period will encourage independent investors, so also accelerating the deployment of arrays.
TEL will on successful development of the wet-mate system by the end of the project look to implement and integrate the design into their existing Deltastream. Hence the research and development will be rapidly utilised into an industrial application

Energy companies, Consultants and Policy makers: The reduction of the cost of electricity from a renewable energy source will allow for greater investment from the energy companies and help meet the reductions in emissions targets. The
development of the marine energy industry through best practice at low cost will help Policy makers and consultants inform the wider community at both national and international levels.


10 25 50
Description The computational modelling undertaken by Cardiff as part of this award has shown that the nacelle of the deltastream device can be lowered from the surface of the sea into the receiving socket with the tidal current at 0.75 m/s. The sideways and rotational movements of the device due to the small current is within the tolerance required for location to be made for both the mechanical and electrical connectors.
Exploitation Route The project has shown that tidal turbines can be developed which allows the structure to remain in place and only the nacelle has to be removed for maintenance. This will allow quick removal and replacement thus ensuring continual power production and minimum downtime, hence reduced costs (and LCOE). The removed device can then be maintained ashore.
Sectors Energy

Description The potential for reduced costs and easier access to devices will be of interest to the companies running tidal devices and/or selling the electricity generated. The first publication has been published in the 2017 EWTEC conference.
First Year Of Impact 2017
Sector Energy
Impact Types Economic

Description Tidal array cost reduction: Testing a removable nacelle design for DeltaStream Technology
Amount £101,008 (GBP)
Funding ID EP/N509838/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 05/2016 
End 04/2017
Title Loadings on a tidal stream turbine during installation using CFD modelling 
Description Deploying a tidal stream turbine is a process which must be made more economic if tidal stream energy is to become a competitive and viable option. Significant costs arise from the installation process itself along with subsequent removal as part of the maintenance cycle. Currently the marine renewable industry largely relies on the use of offshore construction vessels from the oil & gas sector which can cost in the region of £125k per day. Downtime cost is also significant whilst waiting for favourable conditions in which to carry out the removal and/or installation process. CFD modelling has been used to assess the loadings on the nacelle of a horizontal axis tidal stream turbine associated with its installation at the slack period of a neap tide. The CFD code used for this assessment is avaialble. It can be run using ANSYS. 
Type Of Technology Software 
Year Produced 2019