Wave power plant
Wave power plants are a form of smaller hydroelectric power plants . They use the energy of the ocean waves to generate electricity and are classified as renewable energies . Systems that have been implemented so far are prototypes and are used for various experiments and trials.
In contrast to the tidal power station , it is not the tidal range that is used to utilize the energy difference between ebb and flow, but the continuous wave movement .
potential
The power released when waves hit a steep coast averages 19 to 30 kilowatts per meter of coastline; The waves on the high seas reach up to 100 kW per meter of wave cylinder in the most favorable places (e.g. north-east Pacific, north-east Atlantic, Cape Horn, Pacific south of New Zealand). In the inland seas (Mediterranean Sea, Baltic Sea) the values are only about a tenth of those in the oceans. The wave energy available for the location of a wave power plant can be estimated in advance on the basis of the values of wave height and period (period from the arrival of a wave crest at one point to the arrival of the next wave crest) that have been collected by measuring buoys in many places in the seas and oceans for decades .
So far, wave power has cost up to ten cents per kilowatt hour in production. The price is about twice as high as that of wind energy . The world's first commercial wave power plant with an output of 300 kW was commissioned in 2011 in the port city of Mutriku in northern Spain by the energy supplier Ente Vasco de la Energía.
Operating principles
The use of wave energy is possible through various principles:
- Use of the air flowing in and out in a pneumatic chamber, in which the water level rises and falls through a connection to the sea, by a wind generator
- Use of the movement of buoyancy or floating bodies stimulated by waves, which is converted into electricity either via hydraulic systems (Pelamis project, so-called sea snake ) or via linear generators (SINN Power project)
- Use of the potential energy (height energy) of rising waves on a ramp, where the overflowing water flows through a water turbine (Wave Dragon project)
- Use of attenuators such as movable plates, gates or fins, in which the z. B. the movement of the limbs caused by wave currents due to the rising seabed off the coast is converted into electricity (WaveRoller project)
- other approaches (buoys from CorPower Ocean from Sweden (see for example the article from 2016 on the inhabitat website) )
Pneumatic chambers
In wave power stations based on the OWC principle ( English Oscillating Water Column , German: oscillating water column ) pushes each shaft the water in chimney-like concrete pipes and then pulls it in a trough out again. At the upper end, the tubes open into turbines . The air in the concrete pipes is alternately compressed or sucked in by the water column moving up and down. This creates a rapid flow of air in the outlet, which drives a Wells turbine .
A first wave power plant of the OWC type went into operation in 2001 on the Scottish island of Islay for test purposes and thus for the first time fed electricity into a commercial power grid. It was built by the Scottish company Wavegen. The performance data of the "LIMPET 500" power plant were disappointing in the first few years of operation. The originally planned annual average power of 500 kW had to be reduced to 212 kW because the design did not take into account the effects of a sea floor plateau. Overall, however, only an average output of 21 kW was achieved in 2002. In 2005 Voith Hydro took over Wavegen and was able to gradually increase the availability of the turbines to 98%. In 2011 Voith Hydro put an OWC wave power plant into operation in the pier in the Basque town of Mutriku. The plant with 16 Wells turbines and a total nominal output of 300 kW is the first commercial power plant of its kind and is currently operated by the Basque utility Ente Vasco de la Energía (EVE).
One tries to deal with the discontinuity of the energy output, which fluctuates with each wave, by using short-term storage devices such as flywheels . The parallel operation of several similar power plants that are spatially separated can smooth out the fluctuations.
Movement of floats
The movement of floating or buoyancy bodies excited by waves either to one another or to a fixed reference point such as the sea bed, the shore or a very large, inert plate can be converted into electricity using various methods, hydraulically or directly.
Attenuator
One possibility to use the kinetic energy of the waves is an arrangement of movable, hinged elements floating on the surface in a carpet or snake shape. The ocean waves twist the entire construction. There are hydraulic cylinders in the joints . The movement forces the working fluid through pipes with integrated turbines and generators into the compensating cylinders. Electricity generation is uneven, but averages when using many devices. An early approach to this was the Salter ducks by the Scottish developer Stephen Salter. Here the shaft raises and lowers the cam levers of an oversized axle.
The best known representative of the attenuator approach comes from the company Pelamis Wave Power from Edinburgh in Scotland. Their power plant resembles a snake in its appearance, hence the name “Pelamis” (Greek for sea snake). A P-750 system consists of 4 long steel tubes and 3 "energy conversion modules" with a nominal output of 250 kW each. It is 150 m long, has a diameter of 3.5 m and weighs 700 t with ballast. After various tests between 2004 and 2008 in the Portuguese port of Peniche (90 km north of Lisbon) and in front of Aguçadoura near Pavoa do Varzim (north of Porto ), all three plants were shut down in the first quarter of 2009 due to technical and financial problems and in moved to the port of Porto. In 2014, the operating company filed for bankruptcy.
→ Main article: Sea snake (wave power plant)
Point absorber
The movement of the waves can also be used to generate energy if the movement of the buoyancy bodies (point absorbers) excited by waves is converted into electricity relative to a fixed reference point. This approach is currently the most numerically followed by wave energy developers worldwide. Some buoy designs in the concept stage use hydraulic cylinders , other developers use linear generators or other pantographs (power take-off, PTO).
An example of such a point absorber power plant is the wave power plant from the German developer SINN Power. The wave power plant uses the relative movement of floating bodies to a fixed structure in a floating compound to generate electricity by means of linear generators. SINN Power has been testing a single one of its wave power plant modules on the Greek island of Crete since 2015.
Other float technologies
Another approach, which uses the movement of waves via a float, is to attach a float to the existing tower of an offshore wind turbine using ropes (e.g. offshore wind farms in the North Sea ). The movement of a tensioned rope by the upward and downward movement of the buoyancy body transfers the mechanical energy to a generator on the wind turbine tower, where it is converted into electrical energy. The Development Center for Ship Technology and Transport Systems (DST), in cooperation with the University of Duisburg-Essen, carried out studies on this, which suggest relatively high levels of efficiency with low construction costs. In 2014 NEMOS GmbH carried out tests on models on a scale of 1: 5 in the Danish test center for wave energy and in Nantes in France at the ECN.
Waves wash over
The Wave Dragon project, which is an example of the overflowing wave power plant concept, consists of a wave concentrator that concentrates the waves towards the center through two V-shaped barriers. The waves amplified in this way run up a ramp. From there, the overflowing water flows back into the sea via turbines that drive a generator. The entire system is designed as a floating offshore power plant and is therefore not tied to the coast. A prototype was tested between 2003 and 2007 in Nissum Bredning , a fjord in the northern part of Denmark . However, the EU project was terminated because it did not meet technical and economic expectations.
Oscillating or moving attenuators
A large part of the wave energy is transmitted by water movements below the water surface. Various technologies use this approach.
The WaveRoller from the Finnish company AW-Energy enables the use of the wave movement underwater near the coast. In water depths of 8–20 m - practically almost on the beach - vertical, movable metal plates are attached to lowerable metal platforms. The currents cause these metal plates to move back and forth. A hydraulic system with an enormous pressure generated in a connected hydraulic motor a torque . Electrical energy is generated from this in a generator connected downstream. The system is connected to the power grid via a submarine cable . The first system of this type went into operation in the summer of 2012 north of the port city of Peniche near Baleal off the coast of Portugal. It consisted of a platform with three movable "plates". The nominal power was a total of 300 kW. Various test series are currently running. The number of “plates” varies from 1 to 3. Anchored to the sea floor, nothing can be seen of the systems above water - apart from the markings.
An alternative implementation of the principle is a floating flap, which is anchored near the coast in a water depth of 10 to 15 meters on the seabed, as developed by the Scottish company Aquamarine Power. In 2009, a first prototype of this system ( Oyster 315 with 315 kW rated power) was tested in the Billia Croo test field of the European Marine Energy Center (EMEC) on the Orkney Islands. In this type of system, the back and forth movement of the flap drives two hydraulic pistons that pump water through a pipeline onto land. The water, which is under high pressure, drives a turbine here. Just like Pelamis Wave Power, Aquamarine Power had to file for bankruptcy in 2015 because no private investor could be found for the capital-intensive development of the technology.
The very broad approach also includes other technologies, such as B. that of the Japanese wave power plant Pendulor . Here, the waves breaking on the bank break open a gate and flow into a container behind. When flowing back, the gate is moved in the other direction. The movements of the door are converted into electrical energy via hydraulics.
Further approaches
Occasionally there are other approaches to the use of wave energy in different concept and development stages.
In a model of sea serpentine wave power plants called anaconda , the floating body consists essentially of a rubber-like material. The energy required for production is therefore significantly lower compared to the steel bodies of other models, which significantly improves the harvest factor, i.e. the amount of energy required for production is generated again in a much shorter time by the system itself .
Individual developers also examined the use of wave energy to move ships, for example. The Orcelle ship designed by the shipping company Wallenius-Wilhelmsen , an overseas car transporter, uses the wave energy through plates arranged almost horizontally at the bottom of the hull, which are moved by the waves around an axis perpendicular to the direction of travel. In addition to the energy of the waves, this ship should also use that of the sun and wind. In contrast, the Suntory Mermaid II catamaran , which was realized in Japan, only moves forward with wave power. However, he only achieves very modest performance (less than walking pace). This is brought about by two movable plates at the stern, which are also approximately horizontally arranged and which are moved by the waves around a wave lying transversely to the direction of travel.
Problems
Many test facilities were destroyed by winter storms, which deliver around a hundred times as much power as the wave movement during the other seasons. As there is therefore insufficient experience with wave power plants, little is known about the ecological effects, for example on marine life.
See also
Web links
Wave energy in general
- Functional principles of different wave power plants
- A detailed overview of the history and technologies of wave energy use by Achmed Khammas
Technical discussion of the topic
- Wave energy - a hydromechanical analysis - dissertation by Dr.-Ing. Kai-Uwe Graw, 1995. Extensive treatise on the possibilities of using wave energy. (PDF file; 17.08 MB)
- Comparison of a new type of wave power plant technology with existing power supply options at a decentralized model location - dissertation by Dr.-Ing. Philipp Sinn, 2015. Contains a discussion of the functional principle of the SINN Power wave power plant as well as a historical review and a discussion of the various wave power plant approaches. (PDF file; 14 MB)
- Wave power as a concentrate. Chinese researchers are using novel methods from transformation optics to increase the efficiency of wave power plants, by Dirk Eidemüller, November 2018
Research centers
- European Marine Energy Center (test and research center in Great Britain)
- Nordic Folkecenter (test and research center in Denmark)
Individual evidence
- ↑ Wave energy map ( Memento from August 22, 2010 in the Internet Archive )
- ↑ Mutriku, the first wave power plant
- ↑ Press release on the website of the turbine supplier
- ↑ The Queen's University of Belfast: Islay Limpet Wave Power Plant, Publishable Report, November 1, 1998 to April 30, 2002. (PDF) (No longer available online.) Pp. 55–56 , archived from the original on March 5, 2016 ; accessed on January 1, 2017 (English).
- ↑ ETSU Report V / 06/00180/00 Rep, wavegen.co.uk (PDF; 1.4 MB)
- ^ Harnessing the power of the ocean. (PDF) In: HyPower. Voith Hydro, 2011, accessed on November 28, 2017 (English).
- ↑ Achmed Khammas: Book of Synergy - Wave Energy - Selected Countries (II) - Great Britain. Retrieved January 2, 2017 .
- ^ European Marine Energy Center (EMEC): Wave Developers. January 15, 2016, accessed January 2, 2017 .
- ↑ cf. z. B. SRI Wave-Buoy Generator (EPAM) on YouTube
- ↑ SINN Power | News. (No longer available online.) Archived from the original on January 2, 2017 ; accessed on January 2, 2017 (English). Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ^ Benjamin Friedhoff, Jan Peckolt: Wave energy for wind parks . In: Hansa , Heft 12/2014, P. 64/65, Hamburg 2014, ISSN 0017-7504
- ↑ NEMOS website Using the energy potential of ocean waves in offshore wind farms to generate electricity , accessed on January 14, 2015
- ↑ wavedragon.net ( Memento from August 26, 2005 in the Internet Archive ) and The Wave Dragon wave energy converter on YouTube
- ^ Sasha Klebnikov: Penn Sustainability Review: Wave Energy. March 5, 2016, accessed January 2, 2017 .
- ^ AW-Energy Oy: WaveRoller Concept. (No longer available online.) Archived from the original on February 22, 2017 ; accessed on January 2, 2017 .
- ↑ Aquamarine Power calls in administrators. BBC News, October 28, 2015, accessed January 2, 2017 .
- ↑ Pendulor ( Memento of May 10, 2015 in the Internet Archive ) (PDF; 88 kB)
- ↑ July 4, 2008. In: New Scientist
- ^ Renewable Energy World. July 15, 2008
- ↑ Pico OWC - Like a snarling monster. In: heise.de - On the special features of wave energy generation on the Mid-Atlantic Ridge
