Ocean current power plant

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Wired ocean current turbine
Sea-bottom current turbine

An ocean current power plant is a hydroelectric power plant that generates electricity from the natural ocean current. Unlike most other hydropower plants, a dam is not built, but the turbine (a tidal turbine ) - similar to a modern wind turbine  - stands freely in the current on a mast, for example.

Advantages and disadvantages

advantages

  • The decisive advantage of ocean current power plants is that ocean currents flow continuously and can therefore be predicted very precisely. The quality of a location can be assessed very well. The amount of electricity fed in is less dependent on the weather than that of wind turbines or solar power plants .
  • Ocean current power plants also manage with very low flow velocities, as the density of the water is around 800 times greater than that of the air.
  • Commercial ocean current power plants should be completely submerged in the water, since mixing the water current with air would lead to a rapid decrease in the density of the current and thus to a drop in performance. In this case, further problems such as corrosion (rust) due to higher air supply are also avoided. This fact also means that there is no visible change in the landscape.
  • Ocean current turbines are as environmentally friendly in operation as wind turbines or solar power plants, as the turbines do not emit any waste materials such as carbon dioxide .
  • The slow rotation of the rotor means that ocean current power plants are probably harmless to fish and other marine animals. This question is currently being investigated in more detail.

disadvantage

  • Ocean current power plants are currently even more expensive compared to other regenerative energy sources, especially wind power and photovoltaic systems, due to the lack of mass production.
  • In the vicinity of the systems, effective fishing is only possible if the water level above the turbine is sufficiently high.
  • When constructing the turbines, interactions with possible ship movements must be taken into account.
  • The installation of the systems is difficult in terms of hydraulic engineering and structural steelwork , so construction work on the open sea or in rivers is particularly challenging. Steel , concrete and other building materials must be suitable for underwater use and protected against salt attack . In addition, puddles can form on the foundation of the system . The seabed near the facility may be eroded or eroded. Maintenance is time-consuming because the systems are under water and therefore difficult to reach.
  • The turbines extract energy from the flow (in principle like wind turbines). This can have an impact on the behavior of marine animals that prefer certain currents. This can also have an impact on the transport of sediments , as the movement of the seabed depends primarily on the current.
  • The turbines make noise that spreads underwater.

European potentials and developments

In Europe (prior to 2007) around 2–3% of electricity consumption can be covered with this technology, in Great Britain around 20%.

In Germany the potential is very low. The only location listed by the Scientific Service of the German Bundestag is the flow area south of the island of Sylt . However, this is located in the Schleswig-Holstein Wadden Sea National Park and the water there is not deep enough to install systems the size of the Seaflow system.

In general it can be said (as of: before 2007) that the trend in Europe is to combine many large systems to form parks, similar to wind parks. Smaller systems are also being developed in the USA, some of which are to be connected directly to the energy end user.

Executed systems

There are over a hundred possible locations in Europe; So far only a few ocean current power plants have been built worldwide:

MeyGen

The most powerful ocean current power plant to date is "MeyGen", located in the Pentland Firth between the Scottish mainland and the Orkney Islands. The first turbines have been supplying electricity since 2016. When fully expanded, MeyGen should be able to generate almost 400 megawatts of power.

In December 2014, Atlantis Resources in Edinburgh announced the start of construction for a total of 269 turbines with a final total output of 398 MW and a standard energy capacity corresponding to the electricity consumption of around 175,000 households. The first two turbines with 1.5 MW each from Andritz Hydro went into operation at the end of 2016, and two more turbines with 1.5 MW each were installed in 2017, so that the nominal output in October 2017 was 6 MW. The expansion to 269 turbines should be completed by 2022.

Hammerfest

The world's first underwater power plant went online in 2003 in Hammerfest, Norway . In 2008 this was the only generator in the world that actually generated underwater electricity.

Minas basin

In trial operation from autumn 2016 to summer 2018, a power plant ran in the Minas Basin, a branch of Fundy Bay in Nova Scotia at Burntcoat Head near the town of Parrsboro , which floated freely in the water due to its own weight. The device had a turbine diameter of 16 meters, a total height of 20 meters and a total weight of around 1000 tons (including 700 tons of foundation for weighting) and was supposed to generate up to 2 megawatts. Fish could cross the system through a central opening, and the rotor blades also turned slowly. The generator was located in the outer ring, the sea water provided the lubrication, so that no oily lubricants were used. The turbines worked in both directions of flow that are available here. In the Minas Basin there are four further planning projects with different technical designs due to the high tidal range with large amounts of water flowing in and out.

This project was terminated in summer 2018 due to insurmountable difficulties, the operator went bankrupt. The main problems were material fatigue and destruction due to stones in the water, water penetrating the device, which disrupted the electronics, and very high costs due to the use of divers for maintenance and repairs.

Scotrenewables SR 2000, Orkney

In the sea in the north of Scotland, a floating, elongated platform built like a ship has been tested since 2017, which is anchored to the seabed with four ropes and on which two propellers hang down to drive the generators. This model "Scotrenewables SR 2000" with a 2 MW turbine generated around 3 GWh of electrical energy from the ocean current between 2017 and August 2018. This is more than all of Scotland's wave and tidal power plants supplied to the grid in the 12 years prior to the completion of this new system. The design makes this floating model easy to maintain because it can be built like a ship on a dock and brought back on land if necessary. At the place of use, all that is needed is an anchorage on the seabed. For the route between the dock and the deployment site, the turbines below are folded up to reduce the draft.

In August 2018, a success was reported in summary: The SR 2000 tidal turbine from the operator European Marine Energy Center EMEC was tested in Scotland off the Orkney Islands for a year with very good results. This currently the most powerful tidal turbine in the world can supply 830 households and at times provided a quarter of the electricity required on the entire island. The company is therefore talking about a record. The turbine could generate electricity cheaply because it was easy to reach even in winter. "Because we were able to use ships for this, the operating costs and losses due to failures could be kept low. Even if the system is still in the test phase and it is our first turbine on this large scale, this first year has shown that its performance." is at the level of other, mature renewable technologies ", say the operators. They are convinced that the new system, together with the 8 gigawatt hours generated in the nearby Meygen project last year, will prove the marketability of tidal power. "When converting to a completely renewable system, it is really important that we have many different sources of electricity," commented Gina Hanrahan of the Scottish WWF office on the successful one-year test.

Electric power from such tidal turbines is considered to be relatively predictable. Energy researchers estimate the global potential for this marine energy to be around 1,500 TWh per year, of which around 10% comes from Europe. Overall, this amount of energy corresponds to almost 6.2% of global energy production in 2015 (24,255 TWh).

Ramsey Sound

In the summer of 2012, a 1.2 MW marine current power plant was built on Ramsey Sound (West Wales) for a test run of 12 months. A module made up of three three-bladed turbines was sunk to a depth of 31 m and connected to a mainland station with a submarine cable. There the electricity is transformed to 33 kV and fed into the public grid. Since the module is not firmly anchored, but rather remains in position thanks to its special construction, the interference with nature is minimal - a prerequisite for why this system received approval in the Pembrokeshire Coast National Park . Strict monitoring (including with IR underwater cameras on all turbines) accompanies the test. Above all, the effects on the environment and changes in the flow are to be examined.

The module is designed so that any number can be grouped at one location. The next step will be a test run with several modules to examine the mutual influence of the turbines.

The sound between Ramsey Island and the mainland is characterized by extreme tidal currents that can reach up to 7  knots . The sound runs in a north-south direction and the island offers the facility protection from storms and heavy waves.

Seaflow (UK, 2003)

The Seaflow power plant , a prototype built in 2003 with a nominal output of 300 kW, was never connected to the power grid for cost reasons. The knowledge gained in the trial operation was implemented in the follow-up project SeaGen .

SeaGen (Northern Ireland, 2008-2017)

The Strangford tidal power plant (also called SeaGen for short ) in the Strangford Strait, County Down , Northern Ireland, was in regular, commercial operation from 2008. The plants were dismantled in 2017.

Roosevelt Island Tidal Energy (RITE)

A demonstration plant for generating energy from the tidal currents with an output of 210 kW was operated from 2006 to 2009 on the bottom of the East River in New York City . However, the current turned out to be so strong that turbine blades were torn off. An improved rebuilding has not gotten beyond the planning stage to date (as of October 2019).

Openhydro

Nova Scotia Power and its technology partner OpenHydro constructed a marine turbine with an output of 1  megawatt (MW) in 2009 , which was launched into the water for a marine energy test facility off Nova Scotia. The turbine, which is open in the middle for the passage of fish, was manufactured by OpenHydro in Ireland . The turbine rested directly on the ocean floor. The 10-meter turbine failed the test run. The aim was to determine the environmental compatibility and future economic viability of a power plant standing in the water, and the test operation should also check the robustness of the turbine in the harsh environment. The prototype was recovered in December 2010, the rotors were broken off because the mechanical stress was too great.

For the unsuccessful successor to the Cape Sharp Tidal consortium, see the information above under 'Executed Plants' (Fundy Bay).

In March 2010, OpenHydro, together with Scottrenewables, received the exclusive rights to develop a 200 MW power plant at Cantick Head in the Pentland Firth off the north coast of Scotland .

A power plant with four 16 m rotors and a nominal output of 0.5 MW has been installed in Brittany off Paimpol since 2011 under the name Arcouest .

Others

  • After a one-year test run in a model power plant near the South Korean island of Jindo in 2010, Voith built a one-megawatt machine on a 1: 1 scale and further developed the current turbine technology at the European Marine Energy Center (EMEC) in Scotland. A test turbine built by Voith at the Heidenheim location was installed off the Scottish Orkney island of Eday from 2013 to 2015 .
  • Sabella D10 in Brest (France) (2015)

Possible combinations

While the combination of wave energy with offshore wind force is unproblematic, the combination with flow energy poses greater challenges.

A unidirectional movement of wind and water is ideal. These proportions can only be found on the trade belts.

See also

literature

  • Niels A. Lange, John Armstrong: Economic use of tidal energy . In: Schiff & Hafen , Issue 3/2013, pp. 76-78, Seehafen-Verlag, Hamburg 2013, ISSN  0938-1643
  • World's first floating tidal platform officially launched The first BlueTEC tidal energy platform was formelly named recently by the mayor of Texel, Francine Giskes, in the Dutch port of Den Helder . In: Ship & Offshore , issue 4/2015, p. 50/51 (English language)
  • Ralf Diermann: Wind turbines under water . In: Deutsche Seeschifffahrt , Issue 3–4, 2016, pp. 54–57, Association of German Shipowners , Hamburg 2016

Web links

Individual evidence

  1. ↑ a b This content was added to the article on February 6, 2007 without citing the source and is now certainly out of date. More recent information is not known.
  2. ↑ Ocean current power plant at www.planet-wissen.de, as of January 14, 2020, accessed on April 23, 2020
  3. ↑ Green light for world's largest planned tidal energy project in Scotland. In: The Guardian , December 19, 2014, accessed December 24, 2014
  4. ↑ Underwater current turbines for the "MeyGen" project . In: Schiff & Hafen , 5, 2018, p. 38f.
  5. ↑ Frank Binder: New technology in the sea for generating energy · SKF relies on current systems · Mega project off Scotland · Special SKF seals from Hamburg · Huge turbines have to withstand strong tides · Forces like a hurricane on land at 350 km / h . Daily port report , October 25, 2017, pp. 1 + 15
  6. ↑ Underwater current turbines set world record. International Economic Forum for Renewable Energies, October 20, 2017, accessed on October 21, 2017
  7. ↑ Norwegians tap into the tides. In: Der Spiegel , September 24, 2003
  8. ↑ Dirk Asendorpf: Lies until the image is right In: Die Zeit , January 24, 2003
  9. ↑ BBC
  10. ^ SR 2000
  11. ↑ website, engl.
  12. ↑ Electricity Generation By Region (2015), page 33 of Key World Energy Statistics of the International Energy Agency , September 2017, accessed September 24, 2018
  13. ↑ NS Power and OpenHydro successfully install ocean current turbines in the Bay of Fundy. In: ots.at , November 13, 2009
  14. ^ OpenHydro & SSE Renewables win license to develop major tidal farm off Scottish coast . ( Memento of March 26, 2010 in the Internet Archive ) March 16, 2010, accessed on April 10, 2010 (PDF; 30 kB). For further information see the section 'Scotrenewables SR 2000', Orkney, above
  15. ^ Voith Hydro. In: EMEC Orkney. Retrieved April 25, 2020 .
  16. ^ Ocean currents between Italy and Sicily provide electricity. In: Die Welt , March 1, 2003
  17. ↑ Offshore power plants Semi- floating wind power plants for the generation of CO2-free energy on a large scale ( Memento from May 20, 2011 in the Internet Archive ) floating wind power plant with double-bladed underwater rotors