Minesto 'Deep Green' technology rides the waves of progress

Hot on the heels of the recent news that Swedish tidal energy outfit Minesto has received an additional €3.5M from KIC InnoEnergy, late last month the company's board has also revealed that it has decided to apply to list shares in the company on First North at NASDAQ Stockholm 'and conduct a new issue of units directed to the public in Sweden of approximately EUR 10 million.'

First created more than ten years ago by Magnus Landberg, an engineer at the Swedish aircraft producer SAAB, the Minesto 'Deep Green' tidal energy technology device is made up of a kite - sometimes also referred to as a wing - that houses a nacelle and a turbine, and which is tethered via a mooring line to a fixed point foundation on the sea bed. The kite is controlled by using a rudder, a servo system and a control system that is steered in a predetermined trajectory at velocities up to ten times faster than the speed of the water current. This action allows the device to generate electricity by converting renewable energy from tidal and ocean currents using an innovative action, closely akin to the behaviour of a wind kite. As water surges over the wing, the current applies a lift force on it that nudges the kite forward - enabling water to pass through a rotating turbine where electricity is created by using a gearless generator.

Minesto began work on prototype Deep Green systems in 2006 - and has assembled, built and tested a total of five devices at a number of basin and ocean sites since then, including a quarter scale prototype that was installed and proven in the tidal waters in Strangford Lough, Northern Ireland two years ago.

The company describes this as a 'cost-efficient R&D platform' where all sub-systems and performance parameters for the full-scale demonstrator are being verified, where the prototypes' integrated power plant has been automatically controlled over a full tidal cycle - from the highest to the lowest tidal currents in ebb, flood and slack water - with the subsequent test results also making it possible to validate several theoretical models and simulations.

WELSH SUPPORT

According to Anders Jansson, Managing Director at Minesto, the company is currently working with partners in Taiwan, Japan, Chile and the US, but the first commercial arrays will be operational in the initial target market of the UK. He reveals that, during May, the company was awarded €13 Million in financial support from the European Regional Development Fund (ERDF) via the Welsh Government as part payment for the inaugural commercial deployment of the device off the coast of Holyhead in North Wales.

As part of the initiative, Minesto will set up its UK Headquarters in North Wales and deploy the first ever commercial scale 0.5MW Deep Green power plant in Holyhead Deep. Following this initial deployment, the company will make additional installations over a period of 'several years' - eventually culminating in an array boasting a total capacity of at least 10MW that is slated for full operation in 2019. According to the company, the North Wales array will eventually supply power that equates to the domestic electricity needs of some 8,000 households and help to generate 'significant employment opportunities in both the construction and operational phases.'

COST COMPETITIVE

In Jansson's view, one of the chief benefits of the Minesto system is that it is 'the only dependable technology that it is capable of generating electricity at sites with depths between 50-120 metres from low and medium-velocity tidal and ocean currents between 1.2 and 2.5 metres per second (m/s)' - a level at which he claims 'no other known technology works cost-efficiently.' He also believes that the technology's high efficiency is another factor that enhances its competitiveness - a quality that he says is achieved via the 'unique technique' of raising the relative amount of water flowing over the turbine 'by a factor of at least 10 compared to competing devices,' in the process helping to make it 'the most cost-effective power plant on the market today.'

"The Deep Green tidal and ocean current power plant is a step change marine energy technology with the potential to double the amount of electricity that can be produced from tidal and ocean currents," adds Jansson.

In terms of offshore costs, Jansson also points out that, due to the lower operational velocities and the lightweight nature of the device, smaller boats and equipment can be used for installation and service and maintenance, helping to reduce costs. For example, the device can be serviced with Multicats that cost €4,000-10,000/day - compared with some competing technologies that Minesto says need special DP vessels, which cost approximately €67,000-159,000/day to rent.

Deep Green is also relatively small in size and lightweight - the plant weighs in at about seven tonnes, around 10-25 times less per MW than competing technologies located in 'hot-spot' areas with strong and relatively easily reached tidal currents.

"Deep Green fits in a standard EU container, allowing fast and low cost logistic solutions. For instance, a 0.5 MW wind power station needs 4-6 trucks for transportation, Deep Green needs just one," says Jansson.

As well as being relatively compact and cost competitive, Jansson highlights the fact that the Deep Green device is also easily accessible.

"In strong currents boats can sometimes only operate for as little as three hours per day. Deep Green sites are accessible at least 14 hours per day," he says.

"The extensive real life testing and technical modelling point suggests a long-term COE (cost of energy) of some €66-118/MWh. This is significantly lower than all current offshore energy production - and closing in on wind power on shore," he adds.