Since 2003, the island group off the northern coast of the Scottish mainland has gradually transformed into a global leader in the sector. Fast-moving tidal streams, huge Atlantic waves and vast, sheltered natural harbours make Orkney an ideal testing ground for tidal and wave energy devices, and the Stromness-headquartered European Marine Energy Centre (Emec) has developed the infrastructure and expertise to enable it.
Here are five projects that show what the rest of the UK – and the world – could gain by exploring wider deployment of marine renewables and associated zero-carbon infrastructure.
The O2 tidal turbine
Developed by Orbital Marine Power, the O2 is billed by the company as “the most powerful tidal turbine in the world”. Floating on the surface – unlike earlier seafloor-mounted horizontal-axis turbines – with two rotors submerged, the 2MW device is designed for easy and cost-effective installation, maintenance and operation.
Future iterations might be bigger or smaller depending on the installation site, CEO Andrew Scott told Professional Engineering. “We recognise we needed to do it at scale, so the scale that we built to, 2MW, is pretty epic from an engineering perspective,” he said. “It's about the size of a jumbo jet and it kind of looks like a spaceship.”
Emec’s hydrogen production plant
Even before marine renewables reach their full potential, the islands already had a unique problem – they generate too much wind energy for the grid to handle. One of Emec’s solutions was hydrogen.
The centre has a hydrogen production plant at Caldale on Eday, just a short distance from the Fall of Warness tidal test site. The 0.5MW rapid response proton exchange membrane (PEM) electrolyser can produce ‘green’ hydrogen from excess energy produced by tidal turbines and the 900kW Eday community wind turbine.
The production plant is complemented by other infrastructure, such as a fuel cell on Kirkwall Marina that powers ferry electricals while they are in port, as well as a refuelling point for hydrogen cars. Future projects could see hydrogen used to decarbonise shipping or aviation.
The ATIR tidal turbine
Similar to the O2, and tested roughly 100m away in the Fall of Warness, the ATIR turbine by Magallanes Renovables also has two submerged blades. Unlike the O2, the blades are fore and aft, rather than port and starboard. The configuration is made possible by a 15m rudder-shaped mast, which helps maintain the platform’s position in the water and gives engineers and technicians direct access to the powertrain.
Magallanes engineers can control the machine from shore, but a control system is designed to handle everything itself. When in use, it changes parameters such as turbine blade angle – changing the speed of rotation – and distribution of water ballast – keeping the platform level.
The Blue X
Unlike the ATIR and O2 platforms, the Blue X by Mocean Energy is aimed at extracting energy from the waves, rather than the tide. Predecessor to planned devices Blue Star, which will power subsea applications, and the grid-scale Blue Horizon, the Blue X harvests energy by flexing around a central axis as waves travel along its length.
“It’s forced to flex because of the shape of the waves – it dips in the middle when it’s in the trough of a wave, and when it’s at the peak it’s forced to flex the other way,” said Tom Jackson from Mocean Energy.
The devices could one day work alongside floating offshore wind turbines to maximise the amount of energy harvested from offshore sites, managing director Cameron McNatt told Professional Engineering.
ReFlex
Led by Emec, ReFlex Orkney is a £28.5m project aimed at creating an integrated energy system throughout the islands. Powered entirely by renewable energy, it includes a ‘virtual powerplant’ formed of hundreds of domestic batteries and battery-electric vehicles, which are flexibly charged in response to supply and demand.
The system is designed to maximise the potential of the islands’ renewable power sources, reduce the cost of energy and lower the area’s carbon footprint. Developers hope it could provide a model for other areas around the UK and in other countries.
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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.