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Streaming power plants  02: tide power plants 02: news 01

The sea brings energy, you just have to know how to use it

News

presented by Michael Palomino

Feb17, 2012: Electricity from the power of the tides: Siemens relies on low and high tide (ebb and flow)
(orig. German: Strom aus der Kraft der Gezeiten: Siemens setzt auf Ebbe und Flut)
from: n-tv online; 17.2.2012;
http://www.n-tv.de/wirtschaft/Siemens-setzt-auf-Ebbe-und-Flut-article5524856.html

Translation:

The realignment in the German energy policy is improving the chances of success for niche providers in the market for renewable energies. The DAX-listed company Siemens is forging ahead with a takeover to secure know-how for tidal power plants.

German industrial giant Siemens wants to take over the small British company Marine Current Turbines (MCT - link) completely. The remaining shares are to be acquired in the next few weeks, Siemens announced. No details were given about the financial details. The Munich-based technology group had only increased its stake to 45 percent in November 2011.

Bristol-based MCT is considered a specialist in the marine energy market. Experts expect this still very young segment of the renewable energies sector to have great potential for the future.

Tidal power plants use the currents in the sea created by the ebb and flow of the tide to generate electricity. In principle, they do not work much differently than wind power plants: A propeller drives a generator. This converts the naturally occurring kinetic energy into electricity. Unlike wind turbines, the rotors rotate underwater.

Usually, only the maintenance platform is visible from land. A special feature is that the rotor blades are much shorter and more compact due to the high water resistance. Tidal power plants consist of massive structures that, with their anchoring, not only have to withstand the force of the tides, but are also permanently exposed to the risk of corrosion from salt water.

Tidal turbines ultimately harness the gravitational pull of the moon. Their greatest advantage is the consistency of the tidal range triggered by the moon's orbit. Unlike winds, tidal currents occur in regular cycles. The amount of current generated can be calculated in advance with some minor variations.

However, the gravitational forces of the moon can only be exploited meaningfully in a few regions. To generate strong currents, special geographic coastal formations are required.

Individual coastal areas of Canada, Great Britain, Ireland, France and some countries in the East Asian region are considered suitable for the construction of tidal power plants.

mmo/rts>

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Brittany (France) Nov.3, 2012: Tidal power plant under the water level in the open sea  - tidal turbine park on the sea ground "Paimpol-Bréhan":
Renewable energies: France builds a power plant under water
(orig. German: Erneuerbare Energien: Frankreich baut ein Kraftwerk unter Wasser)
http://www.welt.de/wirtschaft/article110591813/Frankreich-baut-ein-Kraftwerk-unter-Wasser.html

Translation:

<While in Germany the landscape and the sea are littered with wind turbines, the French are trying it with turbines under water. That has a lot of advantages - and not just visually.

By Daniel Wetzel

The Bretons don't usually have much of a thing for the folks from Paris. Projects of the central government have often failed due to the stubbornness of the coastal inhabitants. Especially energy supply projects. The Bretons don't want other forces mengling into their affairs.

It's no wonder that none of France's 58 nuclear power plants is located in Brittany. Well, except for Brennilis, this tiny experimental reactor with an output of barely 70 megawatts. And even for that one, there was only room in the remote Devil's Moor Yeun Elez, which the ancient Celts said was the entrance to another world, and the Christian missionaries said was the entrance to hell.

The Brennilis breakdown reactor has been shut down for a quarter of a century, a ruin. The Bretons prevented the construction of a larger reactor in 1980 in the village of Plogoff with street battles and barricade building against a large police force.

No nuclear power plant reached Brittany

The attack of Roman cohorts on the small Gallic village of Asterix, which is said to have been located nearby, was nothing compared with this.

Even a special troop of paratroopers of the gendarmerie could not impose the will of the state. It was an anti-nuclear revolt in the nuclear state of France, which never was repeated in other regions of France.

But now Brittany is becoming the scene of a new energy revolution. And although France's state-owned nuclear company Électricité de France (EdF) is once again at the center of it, this time the otherwise so recalcitrant Bretons are playing along. A small miracle occurs: EdF will build a power plant in Brittany. But it's a power plant that no one sees and no one hears: It will be the world's first underwater power plant in the open sea, a power plant powered only by the current of the tides.

EdF manager convinces population of the new power plant

The miracle was made possible by Vincent Denby-Wilkes, a veteran of the French energy industry who heads EdF's operations in Brittany. Denby-Wilkes broke the resistance of the locals with a completely civil method: Citizen participation. Admittedly, in a flexible, compliant, pragmatic way that the planners of a major project like [the underground train station of] Stuttgart 21 could have learned a lot from.

Denby-Wilkes is a manager who prefers to wear a blouson or rain jacket instead of a suit because he is so often on the coast with the people. Every few weeks for the past four years, he has regularly sat down with fishermen, ship owners, hoteliers, environmentalists, village mayors and city councillors to talk about the EdF project, which is first and foremost his project, but of which he only ever says: "It's the people's project here, it belongs to them."

The power plant can be visited for a short time

For the past two years, the manager has invested two days of his working week to promote the unique tidal power plant project among local residents.

The spot in the sea where the underwater power plant is to be sunk in 2013 was not chosen by the energy company, but by local fishermen: The men chose a protected zone for lobsters and crustaceans, where fishing vessels do not go fishing anyway.

The miracle can still be seen for a short time before it sinks: in Brest, the port city at the far tip of the French hexagon, which juts out far into the Atlantic. Completely bombed during the last war, today the naval base is dominated by faceless concrete buildings.

Power plant looks like a cyclops' eye

Fixed to the harbor's dike near the city's fortress walls, a catamaran is moored here, carrying a 16-meter, almost spotless white ring of steel between its outriggers. With its wide band of fins, the structure looks like the iris of a cyclops' eye. It is the prototype of the "Arcouest" tidal turbine.

Sailors from Ireland unhitch the catamaran and tow the turbine wheel through the harbor waters on a test basis. Only half in the water, wedged between the catamaran's outriggers, the Arcouest slowly begins to turn - producing electricity like the dynamo on a bicycle.

Green power technology with the lowest environmental impact

James Ives is always enthusiastic: "The turbine is totally reliable and low-maintenance, with only one moving part," says the head of Irish manufacturing company OpenHydro. "No other green power technology has such a low environmental impact."

That's hard to believe at first: after all, with its standing frame, the marine turbine is 21 meters high and weighs 850 tons. Such a monstrous fish-chopping machine is supposed to have no environmental impact?

But Ives and his clients from EdF are sure of their case. Unlike offshore wind turbines, he argues, the subsea turbines are only installed on the seaground.

Noisy foundation drilling is therefore not necessary. And fish do not feel at home in places with a current speed of at least three meters per second that are productive for electricity production. For months, they would have tested the plant for side effects at the "European Marine Energy Center" on the Scottish Orkney Islands. None were found.

Compared to wind turbines, the underwater turbines have a number of other advantages. Whereas the wind is unpredictable and erratic and is repeatedly interrupted by lulls, the tidal turbines operate in the strong tidal range off the French coast as smoothly and predictably as Swiss clockwork: 24 hours a day, 365 days a year.

This is worth its weight in gold for the stability of the power grid. The direction of the current changes every six hours. But during the ebb and flow of the tide, there is only a small time interval of 20 to 70 minutes every day when the turbine is not working.

Power plants in rivers hardly feasible any more

The idea producing current with tides is not at all new. As early as 1966, Électricité de France completely blocked the mouth of the River Rance in northeastern Brittany with a dam in which 24 turbines were installed to generate electricity. At 240 megawatts, La Rance is still the second-largest tidal power plant in the world after the Sihwa Lake plant in South Korea, which was completed just last year and is also built into a dam.

But blocking off entire rivers is unlikely to be enforceable in the future; ecological considerations speak against it, as do tourist considerations. That's why the new idea of installing free-standing flow turbines in the offshore sea has far more potential.

Tidal power plant with 2.2 megawatts output

The first tidal power plant in the open sea off the coast of Paimpol-Bréhat will initially have four turbines and will only be a test plant with a modest 2.2 megawatts. But even this will be enough to reliably meet the electricity needs of up to 3,000 households around the year.

When the turbine is sunk into 35 meters of water next fall, it could mark the birth of a promising new green energy technology. EdF believes that there are enough strong ocean currents along France's 3,400-kilometer coastline to power tidal power plants with 3,000 megawatts, which could replace three to four nuclear power plants. For Europe as a whole, the potential is estimated at 15,000 megawatts.

French President Hollande wants to reduce nuclear power

For French President François Hollande, the green electricity project of Électricité de France comes just at the right time: The Socialist had announced during the election campaign that he wanted to reduce the share of nuclear power in France from currently 75 to 50 percent by 2025.

Two reactors in Fessenheim, Alsace, are to be shut down as early as 2016, although Germany also wants to shut down more reactors on the other side of the border by then. To launch his new energy policy, Hollande has already convened a strictly timed consultation process that is to culminate in a new energy law in May 2013.

It is clear that the young technology of free-standing tidal power plants will not be able to make a substantial contribution to meeting the demand for electricity in France for several years to come. But the new Paimpol-Bréhan tidal turbine park is already a striking flagship of the French president's green energy vision.

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April 7, 2013: New generation of wave and stream power plants: <power of tides delivers incredible amount of energy:
(orig. German: Kraft der Gezeiten liefert unfassbar viel Energie)
aus: Welt online; April 7, 2013;
http://www.welt.de/wissenschaft/article115038976/Kraft-der-Gezeiten-liefert-unfassbar-viel-Energie.html

Translation:

<Electricity from the power of the waves.

The streams of the oceans contain the energy of 1,000 nuclear power plants. The water movements can be used more and more efficiently by the new generation of wave power plants, which deliver hundreds of megawatts.

By Silvia von der Weiden

This is what the wave power plant of the future could look like: like giant red water snakes on the sea. This power plant is being designed by the Scottish company Pelamis Wave in Edinburgh.

Tides, currents and waves keep the water masses in the world's oceans in constant motion. The energy stored in them could be tapped by modern technologies. The World Energy Council in London estimates that the amount of electrical energy that could be harnessed in principle is 2,000 terawatt hours per year - that's more than three times Germany's annual electricity consumption.

This could supply 250 million people worldwide with renewable energy, the World Energy Council believes: "Above all, power plants that use tides and strong ocean currents to generate electricity will contribute a share to the renewable energy supply in the near future."

They work much like wind turbines, only underwater, and can be operated wherever the tides create strong streams near the coast. Because water has an energy density about 800 times greater than wind, the underwater power plants can generate electricity much more efficiently. Energy experts estimate the potential of the technology at 1.5 terawatts, which is equivalent to the output of about 1,000 nuclear power plants.

It all began in 1967 with the La Rance tidal power plant in Brittany, where the Rance River flows into the Atlantic Ocean in the Bay of St. Malo. The power plant uses a tidal range of twelve to 16 meters. At high tide, the water flows through 24 tubular turbines into the bay, which is separated by a dam wall. When the water level between the open sea and the reservoir is at the same level, the tubes are closed. As the level falls at low tide, the process is repeated in reverse.

Tubular turbines like in storage power plants

With its total output of 240 megawatts, the tidal power plant supplies around 600 million kilowatt hours of electricity a year. That's about as much as 300 wind turbines produce, and enough for a city of 150,000 households. Two years ago, the old pioneer had to relinquish the superlative of being the largest tidal power plant in the world to the Sihwa-ho tidal power plant in South Korea.

Built in Asan Bay near the capital of Seoul, the power plant has a total capacity of 254 megawatts. However, it only uses the incoming water at high tide to generate electricity; at low tide, the water is returned unused to the sea. Tubular turbines are also used, as have long been used by storage power plants to generate energy.

Engineers in the German-British research project "Seaflow", led by the British company Marine Current Turbines, have ventured into new technological territory, i.e. into the open sea with its storm-lashed, salty waters. In 2003, the first ocean current power plant went into operation in the Bristol Channel off the coast of Cornwall.

Concentrated power under the water

The rotor, which consists of two blades, has a diameter of eleven meters and is mounted several meters underwater on a steel tower anchored to the seabed. The sea there is about 50 meters deep. The prototype had rotor blades that could rotate in opposite directions so that the currents could be optimally used to generate electricity during both low and high tides. The test turbine reached a maximum output of 290,000 watts and provided valuable research data during one year.

These have enabled the construction of its successor, SeaGen, in the Northern Ireland Straits near the fishing town of Strangford. It is the first commercial ocean current power plant. The strong currents of up to four meters per second prevailing there make the use of the technology economical. The power plant, with a total capacity of 1.2 megawatts, has been in operation since 2008 and supplies electricity almost around the clock.

It resembles a wind turbine with two turbines. However, little of it can be seen. Only the upper part of the steel tower rises out of the water. At least three meters below the water level, the two rotors, each mounted on a boom, turn in the current. The electricity they generate is fed into the grid and is enough to supply 1500 households.

Longer rotors are like wind turbines

Since that's going so well, power engineering company Siemens, which acquired SeaGen with Marine Current Turbines, is now planning to build a ten-megawatt power plant. The new subsea power farm is to be built in the Irish Sea off Wales near the Skerries group of islands and will consist of five turbines of the more advanced SeaGen-S type in the final stage. The power plant is scheduled to go on stream in 2015 and will then supply electricity for around 10,000 households.

To achieve this, the output of the new turbines will be significantly increased. At one megawatt each, this is almost twice as high as before. The most striking feature is the large rotors, whose diameter will be increased from 16 meters in the predecessor type to 20 meters and which will also each be equipped with an additional rotor blade. This makes the underwater power plants increasingly similar to wind turbines.

The analogy goes even further, as Wolfgang Maier, Head of Business Development at the Swabian company Voith Hydro Ocean Current Technologies, explains. "As with offshore wind energy, the development of current power plants is leading to increasingly powerful plants that are erected in underwater power parks. This has the advantage that large amounts of electricity are transported to the mainland in bundled form."

Hundreds of turbines in huge dimensions

One such large-scale project, for which Voith is supplying the turbines, is being planned off the coast of the South Korean province of Jeollanam-do. With the Seaturtle Tidal Park, the world's largest tidal current power plant will be built there starting in 2016/2017. In its final stage, it will combine hundreds of turbines delivering a total output of 150 megawatts. With its dimensions, the project sets new technological standards, a challenge for the engineers and technicians involved.

That's why the manufacturer first tested the loads on a 1:3 scale model with a 110-kilowatt prototype of a new type of tidal current turbine. "The rotors and turbine housings must be designed to withstand the harsh operating conditions in the sea, especially with regard to corrosion by salt and fouling by algae and barnacles," says Stefan Riedelbauch, a professor at the Institute of Fluid Mechanics and Hydraulic Fluid Machinery at the University of Stuttgart. Together with his team, the scientist was involved in optimizing the new type of turbine.

The test turbine, which has since been dismantled and returned, "fully met the expectations placed in it," the manufacturer also emphasizes. The design is based on a small number of moving components, which are robust and designed to be seawater-resistant. "The rotor blades can be approached from both sides and can thus absorb energy from both directions without having to rotate the turbine when the tidal current changes. The bearings are lubricated by seawater and require no oils or greases at all. The entire turbine and thus also the generator gap are flooded and cooled by seawater," says Voith Hydro expert Maier, listing the most important advances.

"Gaping oyster" from Scotland

The "Oyster" project of Edinburgh-based Aquamarine Power proves that engineers are not running out of ideas for using marine power. The power plant, which floats in shallow water close to the coast and is anchored to the seabed, is shaped like a giant hatch and thus resembles a gaping oyster. While one part of the bulky plant lies just below the water level, the other part of the flap protrudes almost vertically from the water surface. The swell pushes it down forward and then swings it back to its original position.

The rhythmic motion caused by the wave energy is transmitted to two pumping pistons that deliver water through a pipe to the shore. The water, which is under high pressure, drives a turbine there. This is how the Scottish manufacturer explains the operating principle of the unusual technology, which it has already tested with a prototype. According to the manufacturer, Oyster 1 delivered 315 kilowatts of power during tests in 2009 at the European Marine Energy Center on the Orkney Islands and completed 6,000 hours of operation.

Meanwhile, the manufacturer is testing an even more powerful power plant. Oyster 2 measures 16 by 26 meters when unfolded and has an output of 800 kilowatts. Three such turbines are to be combined into an "Oyster" power plant this year. On its website, the company already dreams of a power plant park with up to 100 megawatts of capacity.

Power plant is also possible on the open sea

No less clever is the idea with which the Dutch company SBM Offshore wants to convert the kinetic energy stored in ocean waves directly into electric current: with electroactive plastics in which the force of the waves triggers a change in their shape and thus charge shifts in the material. This way of generating electricity actually works in practice, as scientists at Darmstadt Technical University and Robert Bosch GmbH have already demonstrated with a specially designed di-electric elastomer generator.

Another concept involves mooring buoys in the sea. The ropes used to attach the buoys to the seabed are to consist of rolled films of electroactive polymers. The buoys will transmit the ups and downs of the waves to them. The polymers are thus stretched and compressed and generate electricity in this way. In the future, this could create a power plant on the open sea.>

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