Wave Dragon
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Wave Dragon is the world’s first offshore wave-energy converter, slated to produce power for the Danish power grid. It was deployed in December 2003, expected to reach maximum output in August 2004, and final structural completion in December 2004.
Wave Dragon is a joint EU research project, including partners from Austria, Denmark, Germany, Ireland, Portugal, Sweden, and the UK. Moored in coastal waters in depths of over 25 meters, the 237-ton Wave Dragon utilizes energy generated by waves 'overtopping' the unit; the water is initially stored in a reservoir to pass through turbines which produce electricity. The current project is one-fourth the size of the full proposed system.
If successful, Wave Dragon will be a competitive new technology. Plans to build and deploy power production units elsewhere in the EU are already underway.[1]
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[edit] Technology
Wave Dragon is a floating, slack-moored energy converter of the 'overtopping' type which can be deployed as a single unit, or in arrays of up to 200 units; the output of such an array would have a capacity comparable to traditional fossil-fuel power plants.
The first prototype was connected to the power grid in 2003 and is currently deployed in Nissum Bredning, Denmark. Long term testing is under way to determine system performance; i.e. availability and power production under different weather and tide conditions. A multi-MW deployment is expected in 2009.
The Wave Dragon concept combines existing, mature offshore and hydro turbine technology. In the Wave Dragon, the Kaplan turbine is being tested at the Technical University of Munich. This turbine uses a siphon inlet whereas the next 6 turbines to be installed will be equipped with a cylinder gate to start and stop water inlet to the turbine.[2]
Wave Dragon is the only wave energy converter technology under development that can be freely up-scaled. Due to its size service, maintenance and even major repair works can be carried out at sea leading to low O&M (overhead and maintenance) cost relative to other concepts.
[edit] Principles
[edit] Construction
Wave Dragon uses principles from traditional hydropower plants in an offshore floating platform to use wave energy.
The Wave Dragon consists of two wave reflectors that direct the waves towards a ramp. Behind the ramp, a large reservoir collects the directed water, and temporarily stores the water. The reservoir is held above sea level. The water leaves the reservoir through hydro turbines.[3]
Three-step energy conversion:
Overtopping (absorption) -> Storage (reservoir) -> Power-take-off (low-head turbines)
Main components of a Wave Dragon:[3]
- Main body with a double curved ramp (reinforced concrete and/or steel construction)
- Two wave reflectors in reinforced concrete and/or steel
- Mooring system
- Propeller turbines
- Permanent Magnet Generators
[edit] Design
Wave energy converters make use of the mechanical motion or fluid pressure. Wave Dragon does not have any conversion, e.g. oscillating water/air columns, hinged rafts, and gyroscopic/hydraulic devices. The Wave Dragon directly utilises the energy of the water's motion.
The Wave Dragon is of heavy, durable construction and has only one kind of moving parts: the turbines. This is essential for any device bound for operations offshore, where extreme conditions and fouling, etc., seriously affect any moving parts.
Wave Dragon model testing has been used in order to:
- Optimize 'overtopping'
- Refine hydraulic response: anti-pitching and anti-rolling.
- Reduce stress on wave reflectors and the mooring system, etc.
- Reduce construction costs, maintenance and running costs.
[edit] Main Body
The main body or platform consists of one large floating reservoir. To reduce rolling and keep the platform stable, the Wave Dragon must be large and heavy. The prototype used in Nissum is of a traditional (ship-like) plate construction of plates of 8 mm steel. [3] The total steel weight of the main body plus the ramp is 150 tons, so that 87 tons of water must be added to achieve the 237 tons total weight needed for stable continuous operation. [3]
[edit] See also
[edit] References
- ^ Quote from EU Commission, Press release, IP/04/350, Brussels, 16 March 2004:
- ^ Keulenaer, H. “Wave Dragon”, Leonardo Energy, 2007-04-13. Retrieved on 2008-04-10:
- ^ a b c d Wave Dragon Wave Dragon Homepage, Retrieved on 2008-04-10:
[edit] External links
- Wave Dragon - official website
- http://www.guardian.co.uk/science/2004/mar/21/energy.renewableenergy
