Sunset over South Stack Lighthouse on Holy Island, Anglesey

Holyhead Deep – the world's first low-flow tidal stream project

Holyhead Deep marks the starting point of the industrialisation of Minesto’s unique marine energy technology Deep Green. It is not only our first utility-scale project – but also the first low-velocity tidal energy project in the world.

Holyhead Deep has been identified as a perfect location for a utility-scale Deep Green installation. The area matches all the site requirements by providing low-flow tidal velocities (1.5–2 m/s mean peak flow) at a depth of 80–100 meter, only approx. 8 km from Holyhead where Minesto UK head offices are located.

In June 2014, Minesto was awarded an Agreement for Lease by The Crown Estate for a 10 MW installation in Holyhead Deep.

Location of the Holyhead Deep site

Holyhead Deep is the name of a large depression in the seabed, located west of Anglesey, North Wales. Except having perfect oceanic requirements, the area also benefits from good port facilities in Holyhead Port, onshore grid connection possibilities at Holy Island as well as good transport links and access to installation and maintenance services.

Project development process

Developing Holyhead Deep into a commercial tidal energy array will be done in phases. In a first step, one 0.5MW demonstrator, called DG500, will be installed. The purpose of this first installation is to prove functionality and power production performance in utility scale. In April 2017, Minesto was consented Marine License for the DG500 installation in Holyhead Deep.

Commissioning of the DG500 device was first initiated in June 2018, comprising a series of tests over different stages, including verification of launch and recovery procedures, testing of each function of the control system, and finally operating the DG500 unit in full figure-of-eight trajectories.

Following successful deployment and testing of the DG500 was achieved during the autumn 2018.

The installation site is located in the southern corner of Holyhead Deep. The area has been carefully selected to maintain separation from shipping lanes and to minimise the impact on other sea users. Stakeholder engagement and multi-disciplinary environmental research work have been ongoing since 2012, and we work closely with Bangor University and research organisations in Wales to understand the specific local site criteria's.

Commercial array expansion plans

Minesto's long-term plan is to expand the Holyhead Deep site to a commercial tidal energy array with a total installed capacity of up to 80MW. Minesto intends to develop the site in phases as part of a deploy-and-monitor approach. This gradual expansion would see us taking the Deep Green technology from demonstrator to full industrial roll-out in North Wales.

Minesto has submitted a scoping report to UK consenting authorities Marine Management Organisation (MMO) and Natural Resources Wales (NRW), asking for their scoping opinion for development of an 80MW site in Holyhead Deep.

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Choosing Wales

After an in-depth option analysis of low-flow velocity sites around the world, we identified UK as the most suitable location on the basis that its territorial waters contain approximately half of the European tidal resource and around 10–15 percent of the known global resource.

Numerous locations around the UK were considered, but Wales was selected as the preferred option due to the highly suitable environmental conditions and government commitment to marine renewable energy, which offers significant opportunities to attract support and investment into the Holyhead project.

The Holyhead Deep site is in close proximity to the West Anglesey Demonstration Zone, an area which has been identified as a suitable location for installation of marine energy devices in the short to medium term. Minesto is collaborating with Morlais Marine Energy, manager of the West Anglesey Demonstration Zone, to jointly develop grid and cable infrastructure for the future proposed array. Such collaborative initiatives could significantly reduce costs and minimise the combined environmental footprint of the two projects.

An EU-funded project

In May 2015, Minesto was awarded a €13m grant from the European Regional Development Fund through the Welsh European Funding Office (WEFO), part of the Welsh Government, for the commercial rollout of Deep Green. As part of the contract, Minesto UK's head office has been established in Holyhead. In May 2019, the Welsh government announced their continued support for Minesto’s commercial development in Wales following the award of €14.9 million of EU funding through WEFO for the next phase of Minesto’s tidal energy scheme in Wales.

The project is not affected by the British exit from the European Union.  

Creating shared value

The vision of the Holyhead Deep project is to contribute to the transition from fossil fuels to renewable energy, making Wales and the UK a global leader of a sustainable future. This is the first tidal energy project in the world targeting the power of low-velocity currents. Once fully installed, a 10MW Deep Green array will supply local, safe and clean electricity to the equivalent of more than 8,000 Welsh households. The planned increase of the site to 80MW installed capacity would increase that figure to almost 70,000 households.

The investment linked to building, commissioning and operating the first commercial-scale Deep Green array will also make a significant positive contribution to the creation of new employment opportunities and stimulating long-term growth and investment in Anglesey.

The establishment of Minesto UK head offices in Holyhead has seen 17 full-time jobs created to date and the Holyhead Deep project is already stimulating business both in and outside the direct supply chain.  

Environmental Statement & HRA report

We are committed to developing the Holyhead project in an environmentally responsible fashion, ensuring all potential impacts on the local environment and wildlife are minimised.

As part of the application for a Marine Licence for the first 0.5MW installation in Holyhead Deep, Minesto commissioned an in-depth Environmental Impact Assessment (EIA) informed by two years’ of multi-disciplinary environmental research including dedicated site-specific surveys and predictive modelling exercises. The results are detailed in an Environmental Statement (ES), which was submitted alongside the licence application.

Minesto also commissioned a Habitats Regulations Assessment (HRA) report to provide information on the potential effects of the project of internationally important conservation sites designated under European legislation (known as Natura sites). The ES, Non-Technical Summary (NTS) and HRA report are available to download below.

Decommissioning Plan

In addition to the Marine Licence (ORML 1618) which gives Minesto right to construct and operate an offshore renewable energy installation in Holyhead Deep, the company are required to submit a plan (“decommissioning programme”) for decommissioning of the installation to the Department for Business, Energy & Industrial Strategy. This decommissioning plan is available for download below.