The £2m Renewables for Subsea Power (RSP) demonstrator project connected the Blue X wave energy converter, built by Edinburgh company Mocean Energy, with a Halo underwater battery developed by Aberdeen energy management specialists Verlume.
The two technologies were deployed in the seas off Orkney, north of the Scottish mainland, and have begun a minimum four-month test programme, where they will provide low-carbon power and communication to infrastructure including subsea controls equipment from energy technology company Baker Hughes and a ‘resident’ underwater autonomous vehicle provided by Transmark Subsea.
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An artist's render of the installed devices, including the Transmark robot (bottom left)
The European Marine Energy Centre (Emec) has supplied instrumentation to measure the speed and direction of currents during the deployment, while Wave Energy Scotland has provided £160,000 to support the integration of an electricity-carrying ‘umbilical’ into the wave energy converter.
The project aims to show how green technologies can combine to provide reliable low-carbon power and communications to subsea equipment, offering a cost-effective alternative to umbilical cables, which are carbon-intensive and have long lead times to procure and install.
The partners are testing the entire system 5km east of the Orkney mainland, raising the system’s technology readiness level (TRL) to 6-7 (actual system completed and qualified via test and demonstration).
Mocean Energy’s Blue X prototype underwent rigorous at-sea testing at Emec’s Scapa Flow test site in Orkney in 2021, where it generated first power and provided data on machine performance and operation. Wave Energy Scotland supported that programme with £3.3m funding for development, construction and testing.
“This is a natural next step for our technology,” said Mocean Energy managing director Cameron McNatt. “The new test site east of Deerness offers a much more vigorous wave climate and the opportunity to demonstrate the integration of a number of technologies in real sea conditions.”
The Halo seabed energy storage system was specifically designed for the harsh underwater environment, reducing operational emissions and facilitating the use of renewable energy by providing a reliable, uninterrupted power supply. The battery has an ‘intelligent’ energy management system, Axonn, which autonomously maximises available battery capacity in real-time.
The RSP Halo system is the second variant built for commercial wave power integration, and the first built at Verlume’s facility in Dyce, Aberdeen.
Andy Martin, chief commercial officer at Verlume, said: “The testing will provide a great opportunity to gather high quality performance and operational data, which will support the further electrification of the subsea sector.”
Nigel Money, managing director of Transmark Subsea, said: “This is a fantastic opportunity to further test our resident autonomous underwater drone in an open sea environment.
“We currently run the system in salmon farming nets, which is a more closed environment.
“Mocean and Verlume’s solution fits very well with our product and allows us to demonstrate broader operational capabilities of an off-grid resident AUV. Our dock and drone is designed to be easily deployed anywhere and the RSP project is a great demonstrator of this capability.”
The Orkney deployment is the third phase of the RSP project, which is supported by consortium partners including UK energy companies Harbour Energy and Serica Energy. Each phase of the programme has been supported by grant funding from the Net Zero Technology Centre (NZTC).
In 2021, the consortium invested £1.6m into phase two of the programme, which saw the successful integration of the core technologies in an onshore commissioning test environment at Verlume’s operations facility in Aberdeen.
Graeme Rogerson, renewables lead at the NZTC, said: “We are delighted to support this final phase field trial, as we see the potential for the RSP system as a dispatchable energy source to provide reliable renewable energy for remote off-grid applications, powering subsea tiebacks to injection wells for CCS (carbon capture and storage.”
Professional Engineering spoke to Mocean Energy’s Cameron McNatt in 2021, where he provided detail on the RSP project, including information on the underwater vehicle. “An umbilical running down to the seabed… will provide power and communications down to a subsea skid, which will have subsea batteries as well as what are called subsea control modules,” he said.
“We'll also have a ‘residential’ autonomous underwater vehicle that will be deployed... it goes in, docks, and gets a power and communications link. And then it can essentially live underwater for an extended period of time, and carry out repeat subsea activities, inspections, and things like that.”
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