Minesto's marine energy converter DG500 during its commissioning program in the Holyhead Deep, Wales

The future of renewable energy

Imagine that you are standing on a beach, flying a kite in the wind. You feel the strong lift force from the kite in the rope as the wind tries to carry the kite away. As you move the kite sideways, you notice that it flies fast – way faster than the wind is blowing.

If you would attach a turbine to the kite and put it in the ocean, where a water current flows instead of the wind blowing, you would have the concept of Deep Green, Minesto’s patented and awarded ocean energy power plant.

Expanding the ocean energy potential

What makes Deep Green different from other tidal energy technologies is the wing, the size of the turbine and the fact that the power plant is “flying” under water. The wing pushes the turbine through the water in an eight-shaped trajectory, sweeping a large area at a relative speed that is several times the actual speed of the underwater current.

The speed has a cubic relationship to the power production. This means that when Deep Green multiplies the relative speed which the turbine is pushed through the water, the electricity produced by the power plant's generator is several hundred times greater compared to if the turbine would be stationary.

By adding this step of energy conversion, Minesto expands the global ocean energy potential.

How it works

Minesto’s marine energy technology, called Deep Green, generates electricity from low-flow tidal streams and ocean currents by a unique and patented principle similar to a stunt kite flying in the wind.

The wing uses the hydrodynamic lift force created by the underwater current to move the kite. With onboard control system and rudders, the kite is autonomously steered in a pre-determined figure of eight, pushing the turbine through the water. By doing so, the turbine experiences a water flow several times higher than the actual stream speed.

The turbine diffuse power to the generator which outputs electricity via power cable in the tether. Seabed umbilical transfers the electricity to the onshore connection.

Illustration of Minesto's Deep Green technology in operation
Illustration of the Deep Green power plant and its subsystems

Power plant parts

The power plant consists of a wing (1), which carries a turbine (2) directly coupled to a generator in a nacelle (3). Rudders (4) and control system steers the kite in the predetermined trajectory. The struts (5) are via a top joint connected to the tether (6), which is connected to a bottom joint at the seabed foundation. The tether accommodates the tether rope and cables for communication and power distribution.

Competetive advantages

Market exclusivity

Deep Green is the only known technology to cost-effectively produce electricity at sites with velocities between 1.2–2.4 m/s and depths of more than 60 meters.

Small in size and lightweight

Up to 15 times less per MW than competing technologies.

Low-cost offshore operations

Smaller vessels and equipment are used for installation, service and maintenance. Detachable design concept enables service and maintenance on shore.

No visual, minimal environmental impact

Deep Green operates completely submerged below the water surface, in unison with the marine environment.

Predictable electricity production

Tides are generated by the relative motion of the Earth, sun and moon, which can be calculated with almost 100% accuracy. Ocean currents are nearly constant.

Utilisation of ocean currents

The ability to operate at low velocities makes Minesto's Deep Green the only technology to be cost-efficient in both tidal and ocean currents.

Two product lines provide flexibility and increased market opportunities

Deep Green UtilityDeep Green Microgrid
ApplicationMulti-megawatt grid-connected farmsRemote islands, remote/coastal communities, aquaculture
MarketGlobalGlobal
Market driverAdding baseload renewable energy to the energy mixEmerging energy access, electrification of remote users
CustomersUtilities, project developers, power producersProject developers, island economies, aquaculture developers
Rated power0.5–3MW50–250kW
Wingspan12–24m4–6m
Weight10–35t1–3t
Depth of installation>60m<60m
Operating stream flows1.2–3.0m/s1.2–3.0m/s
Operation & MaintenanceSurface/onshoreSurface/onshore

Technology and project development

Deep Green has been undergoing extensive ocean testing in scale model since 2013 at Minesto's test and demonstration facility in Strangford Lough, Northern Ireland, during which operational functionality and power production have been verified and gradually improved. Read more about the test site here.

Minesto are engaging in several projects to promote the market uptake of the Deep Green technology. Read more under Projects.