Minesto generates power from tidal and ocean currents with measurement technology from HBM

Strain gauges critical in green technology project

Swedish clean tech companyMinesto already extracts one of the bigger energy sources of the future.

At the moment, their award-winning tidal power plants are being tested in the ocean depths off the coast of Northern Ireland.

Inside the prototype, HBM strain gauges play a key role in verifying how the plant behaves in the water and how it measures the forces to which it is exposed.

Oceans cover 70 percent of the earth’s surface. This largely untapped energy source is the focus of Minesto, the largest marine energy company in the Nordics. In 2007, Minesto developed a new concept for tidal power called Deep Green.

Already producing electricity

Deep Green is a relatively small power plant that can extract marine energy even at slow water currents, which makes it considerably more cost effective than previous techniques. Both investors and prospective customers are showing great interest and the company plans to launch the first full-scale power plant in 2017. However, Deep Green already produces electricity using slow tidal currents in the test facility outside Northern Ireland.

The power plant Deep Green resembles a sweeping underwater kite, comprising of a blade and a turbine attached to the seabed with an anchoring line. It moves in a fast 8-shaped path in the water.

Like a kite

The secret of Deep Green is that it moves. It flies like a kite in a figure eight pattern under water, reaching a speed that is up to ten times higher than the currents in the surrounding water. Therefore, the 1:4 scale prototypes can generate 3 kW when the tide has a speed of one meter per second. The goal is to launch a 0.5 MW power plant park in Wales in 2017 and to eventually expand it to an output of 10 MW.

Measuring inside the prototype

Minesto follows a rigorous development plan which has now reached the fifth generation of the prototype of the power plant at a scale of one to four. As part of the development work, complex calculations and simulations are important, but actual measurements are also critical to ensure that the project is on the right track. Minesto has used HBM’s expertise to help install strain gauges in the best possible way inside Deep Green.

Heije Westberg, CTO at Minesto, explains: “We have received very good support from HBM. Strain gauges are not part of our core business, so it's important to get the expertise in measurement technology. HBM has experience from offshore installations and has better tools than we would have access to. In the end, it is both easier and cheaper to use professional help, fully rely on the installation to be solid and to provide reliable measurement results.”

With limited space in the prototype, HBM glued strain gauges directly onto Minesto’s power plant components before they were assembled.

HBM strain gauges are relatively protected inside the plant, but it is still important that the moist environment in no way affects the measurement result.

Moisture and space - a challenge

Although the strain gauges are relatively protected inside the power plant, it is important to ensure that the moist environment in no way affects the measurement result. Thanks to its proven installation and sizing technology for offshore environments, HBM can guarantee this. The lack of space inside the prototype creates another challenge, leading HBM to glue the strain gauges directly onto the plant components before they are assembled in Minesto’s lab.

Testing and measurement throughout the design process is a given at Minesto: “You can calculate anything, but only if you’re aware of its existence. There are always surprises in the form of wind, waves or other unknown loads. Therefore, it is necessary not only to simulate loads, but also to verify reality,” says says Heije Westberg. “Since we cannot over-dimension the power plant just to be on the safe side, we have to know exactly what kind of forces it is subjected to.”

In its full-scale version, Deep Green will only weigh seven tons and operate on 60-120 meters.

Global plans

Measurement will continue to play a critical role at Minesto. In the first full-scale plant, plans are made to include equipment for force measurement. The company has big plans for the future - generating commercial electricity from slow ocean and tidal currents. There are also global opportunities, with projects already underway in several continents. Minesto continues its work to live up to the mission to help minimize the global footprint of the energy sector.

Facts about Minesto

Scandinavia's largest clean tech company in the marine energy field
Founded in 2007
The head office is located in Gothenburg, with a subsidiary in the UK
They develop power plants for commercial production of electricity from slow ocean and tidal currents
Has patented the marine power plant Deep Green
Has been named one of Sweden's 33 hottest young technology companies in the Swedish newspaper Ny Teknik and has been recognised by British magazine Power Technology
Listed on Nasdaq First North Stockholm. Main owners are BGA Invest and Midroc New Technology.