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Tidal power plant: Star Wars fighter makes green electricity

The most powerful floating tidal power plant in the world has gone into operation off the coast of the Orkney Islands. It's called O2, looks like a jet that has landed in the water and can power 2,000 homes.

With the end of the age of combustion engines, the world is becoming more and more electric - and the need for sustainably generated electricity is increasing rapidly. People are currently generating so-called green electricity from hydroelectric power, wind and sun – and to a small extent also from the tides. Humans have been using the tidal range created by the gravitational pull of the moon and sun in combination with the rotation of the earth for more than 1,400 years. The oldest known tide mill to date has been discovered by archaeologists on an island in the Irish natural harbor of Strangford Lough - it dates from 619 to 621 AD. The company Orbital Marine Power from the Scottish Kirkwall (capital of the largest Orkney island Mainland) now announces the commissioning of the most powerful and most modern floating tidal power plant in the world, called O2.

Anchored in the tidal current

What looks like a passenger jet that has landed in the water or a James Bond villain's favorite weapon is a 74 meter long mobile power plant. Its wingspan is 25 meters. The wings can be lowered about 15 meters into the water so that the tidal current can drive the propellers, which are located at the wing tips and have a diameter of 20 meters. Orbital Marine Power emphasizes that its employees assembled the power plant entirely on land in the Scottish port city of Dundee - this means that no complicated and expensive work is required later on the water. O2 can be transported to its place of use both by heavy transport overland and later by tugboat on the water. There, four anchors hold it in place in the tidal current - according to the manufacturer, each of the four anchor chains could lift the weight of 50 double-decker buses (i.e. at least 500 tons). On animations and photos it looks as if the power plant is moving in the water, but it is just hanging in a fixed position in the current.

Two megawatts for 2,000 households

The two propellers drive two one-megawatt generators. The total output of two megawatts reaches the seabed via a movable cable and from there to the mainland via a permanently installed cable. The energy is sufficient to supply 2,000 households with electricity - Orbital Marine Power states annual CO2 savings of 2,200 tons. The project has already started: after 15 years of development work, the first O2 is ready – it is now lying in the waters off the Orkney Islands and is producing electricity. In the future, it will also produce electricity for the European Marine Energy Center (EMEC).The EMEC is a test and research center for the development of wave and tidal power plants based on the Orkney Islands and used by many international companies. The electricity supplied by the O2 power plant is to be used to produce hydrogen as part of the EMEC project. Hydrogen is considered to be too inefficient for vehicle drives ( see podcast ), but in the field of decarbonization of large industries, experts believe that the use of hydrogen has future opportunities.

Twelve revolutions per minute

The propellers rotate at twelve revolutions per minute. That is around 500 times less than with a combustion engine, for example. However, because of the size of the propellers, the wing tips reach a speed of around 43 km/h. Interactions with the marine fauna and flora therefore play an important role when selecting the location for the power plant. According to Orbital Marine Power, the site is selected in close consultation with environmental protection authorities - the manufacturer assumes that the operation of the power plant will have hardly any negative effects. But in addition, several research institutions continuously monitor the operation in order to identify previously undiscovered environmental effects.

Environment Fund, Scotland and EU support

Funding for the development and construction of O2 came from Abundance Investment, a platform specializing in ethical green energy investments, the Scottish Government and the European Union. The EU contributed to the costs through the Horizon 2020 innovation program as part of the FloTEC project and through the North West Europe Development Fund as part of the ITEG (Integrating Tidal energy into the European Grid) project. Since January 31, 2020, Great Britain has no longer been part of the European Union - in Scotland, however, 60 percent of those polled in the exit referendum decided to remain in the EU.

Building a megawatt network creates jobs

Orbital Marine Power is now aiming to commercialize its O2 power plant and integrate it into a multi-megawatt network. The developers assume that the costs for the construction of such power plants will fall sharply in the case of series production - after all, this was also the case with wind power and solar systems. The Scots emphasize that 80 per cent of the parts supplied to the plant come from British companies and that such power plants create many jobs in coastal regions. Orbital Marine Power employs a total of 32 people at its offices in the Orkney Islands and in the Scottish capital Edinburgh.


The futuristic looking O2 tidal power plant from the Scottish manufacturer Orbital Marine Power can be used in different places because of its portability.Because the manufacturer assembles it entirely on land, the potentially high cost of complicated assembly at sea is eliminated.

Man has been using the tides as a source of energy for over 1,400 years. The O2 power plant is now the most powerful energy converter to date that man has used to generate electricity from the alternation between low and high tide. According to the manufacturer, the two-megawatt O2 power plant can supply 2,000 households with sustainably generated electricity. The so-called green electricity also plays an increasing role in electromobility - after all, only electricity generated free of CO2 really helps the climate.

Of course, the law of conservation of energy also applies to a tidal power plant: Driven by the propellers, the tidal current slows down slightly – just like hydroelectric power plants reduce flow speeds and wind power plants reduce wind speeds. Although this can also have an impact on the climate, according to the current state of knowledge, these are negligible not only in comparison to the consequences of climate change fueled by CO2.


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