Minesto – Unlocks low-flow tidal streams with a subsea kite

Minesto has developed a unique subsea kite, Deep Green, that generates electricity from low-flow tidal streams and ocean currents. The technology makes it possible to harness the large potential of the previously untapped low-flow tidal streams.

In order to achieve a sustainable global energy transition, a diverse and domestic energy mix is critical to ensure safe, reliable and affordable energy. Tidal stream and ocean current energy has the potential to play a vital role in this development. In comparison to wind and solar energy, which are unpredictable due to their dependence on climatic conditions, tidal streams and ocean currents have a substantial competitive advantage as they are energy-rich, predictable, reliable, and available on all continents. In addition, they can be exploited with a relatively small environmental interaction. However, while conventional technologies are designed for high-speed locations, a large share of the tidal current resources in the world consists of relatively slow-flowing currents. Minesto aims to harness the largely untapped potential low-flow tidal streams, and has developed a unique technology, Deep Green, that is able to cost-effectively generate electricity at sites with velocities between 1.2m/s and 2.4m/s, and at depths between 60m and 120m.

The company is a spin-off from the Swedish aerospace manufacturer, Saab, and was founded in 2007. The technology was originally invented within the scope of a wind turbine study where vertical-axis turbine concepts were explored. The idea was then taken to Chalmers University of Technology in Gothenburg to evaluate the technical and commercial viability. Since then, Deep Green has been under continuous development, and several generations of prototypes have been tested both in indoor pools and in the ocean. Minesto currently employs 65 people located in Sweden, Wales, Northern Ireland and Taiwan.

A novel marine energy solution

Minesto´s subsea kite technology converts kinetic energy to electricity by way of a unique principle similar to flying a stunt kite in the wind. The concept consists of a wing that is tethered to the seabed, and carries a turbine underneath. The kite uses the lift force of the stream flow to ‘fly’ across the underwater current, pushing the turbine through the water in an eight-shaped trajectory at a speed several times the actual stream flow. As moving water is 832 times denser than moving air, this creates favourable conditions for efficient energy conversion. Electricity is produced in the onboard generator and transmitted through the tether to seabed cables. deep green

There are some small-scale, early-stage development projects focusing on low-flow tidal streams, but these have not yet reached the stage of testing in real conditions.Martin Edlund, CEO of Minesto, explains that to their knowledge, Deep Green is the only known technology that has the potential to produce electricity cost-effectively fromlow-flow tidal streams and ocean currents.The key to Minesto technology's uniqueness is a patented method to increase water flow through a turbine, thus making it possible to increase the energy output per weight unit. This is critical to reach cost competitiveness, and it enables us to operate in low-flow tidal areas.Compared to other technologies, our product enhances the energy conversion, making it a commercial proposition applicable to vast areas of the ocean, which means that we are substantially expanding the exploitable resource”.

Engaging in several projects to promote the market uptake of Deep Green

Since the company´s founding, six generations of Deep Green prototypes have been developed, built and tested. Since 2013, the technology has undergone testing in the tidal streams of Strangford lough, Northern Ireland and in 2018, the DG500 system, a 0.5MW demonstrator, was installed and tested. This was Minesto´s first commercial-scale prototype. As well as expanding the company´s Holyhead Deep site off North Wales, where the goal is to reach an installed capacity of up to 80GW, Edlund explains that Minesto is also developing a smaller-scale system (100kW) which targets off-grid applications such as island economies and aquaculture.

deep greenThe company is currently involved in a project called Deep Green Island Mode (DGIM) in Vestmannasund, Faroe Islands, which aims to install Minesto's first two commercially viable microgrid units in a production and customer environment. In June 2019, Minesto was awarded a €2.5 million grant from the European Commission’s SME Instrument programme. The funding will support the installation of Deep Green in the Faroe Islands together with the utility company SEV. This summer, Minesto completed its first offshore installation phase of the Vestmannasund project. The DG100 tidal kite device is planned to be installed in October 2020 to commence grid-connected operation. In parallel with the DG100 installation, the company has also conducted measurements of tidal flow conditions in another location in the Faroe Islands. 

In addition to their in-house expertise and a customer-focused approach, Edlund considers their ability to raise funding to be the key to their success. Minesto has successfully raised substantial equity and public funding over the years to finance the technology and project development. With more than €40 million of awarded funding from the European Regional Development Fund via the Welsh European Funding Office, European Innovation Council and InnoEnergy, Minesto is the European Union’s largest investment in marine energy to date. The company aims to initiate more collaborations and installation projects, preferably within the frameworks of the vast availability of public financing, which is being launched from 2020 onwards, focusing on renewable energy and innovation linked to the marine environment.

Contact Minesto.


Images © Minesto


By Anna Lygre Solvang