Dragon Class – next generation marine energy power plants

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 Minesto’s patented and awarded marine energy technology called Deep Green. Featuring increased performance and decreased manufacturing costs, the Dragon Class is a new range of power plants. It evolves from the grid-connected Deep Green systems Minesto has installed and operated in Vestmannasund, Faroe Islands.

What makes the Deep Green technology 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 a Deep Green power plant multiplies the relative speed which the turbine is pushed through the water, the electricity produced by the 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

The composite 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.

Power plant parts

By combining different wing spans, generator sizes, and tether lengths, Minesto can offer power plants that are customized to different applications and customer needs. The current product range in development stretches from Dragon 4 (~4-meter wing) to Dragon 12 (~12-meter wing), with rated power ranging from 50 kW to 1.2 MW.

A light and strong FRP structure with a CNC kitted Divinycell foam core withstands the forces generated when the kite circulates under water at high speed. Together with Elitkomposit – a Swedish Composite manufacturer, Minesto has developed the sandwich composite structure. Diab has supported the solution to optimize the geometry/fitting of the Divinycell foam core to best address the manufacturing process.

Minesto to concentrate Dragon Class operations in the Faroe Islands in 2022

Minesto has decided to concentrate this year’s operations with its Dragon Class marine energy converters at the established and grid-connected site in Vestmannasund, Faroe Islands. This plan will mitigate supply chain delays and at the same time allow Minesto to take advantage of significant synergies and new opportunities for more cost-effective operations, electricity production under an existing Power Purchase Agreement, and hence a quicker route to commercial roll out.

Minesto’s first Dragon 4 unit will go straight into continuous grid-connected operation in Vestmannasund, Faroe Islands during the first half of 2022 as originally intended.  To optimise the timeline, Minesto has also decided to install also the second Dragon 4 (100 kW) and the larger D12 (1.2 MW) units in Vestmannasund during 2022, rather than deploying them for demonstration testing in France and Wales, as originally planned.

“The Dragon Class’ increased customer value is straight to the point – maximise yield and minimise costs. This is the backbone product for our ongoing commercial scale-up” said Martin Edlund, CEO, Minesto Group