Since march 2003 a development consortium has performed long term and real sea testing on hydraulic behaviour, turbine strategy and power production to the grid. The 4.35 mill. € project has been secured through substantial grants from the Danish Energy Authority (1.7 mill. €), the European Commission (1.5 mill. €, Contract No: ENK5-CT-2002-00603) as well as the Danish system operator Elkraft System’s RTD fund (0.25 mill. €).
The prototype was deployed in Nissum Bredning, a fjord in the northern part of Denmark.
The 237 tonnes prototype Wave Dragon was March 2003 towed to the first test site at the Danish Wave Energy Test Center in Nissum Bredning, where installation of 6 additional turbines, initial tests and simulations were performed. The prototype was tested continuously until January 2005.
In 2006 a modified prototype was deployed to another test site with more energetic wave climate.
The prototype was finally scrapped in 2010. The all steel built device was designed for a lifetime of only 3 years and the subsurface structural parts was not protected against corrosion. The device was nevertheless still structurally sound after 7 years at sea.
Some of the results are:
- Wave energy absorption performance: Results on Wave Dragon’s wave energy absorption, i.e. overtopping, have been gathered by Aalborg University. Test results from the more than 20,000 operating hours fully verify Wave Dragons wave energy absorption performance
- The turbine/PM generator/frequency converter system performance has been verified
- Redesign of the joint between main platform and wave reflector: Due to a number of de-attachments of the wave reflectors during storms these joints have been modified
- Control system algorithms have been optimised based on the real sea experiences
- More than one year operating and maintenance experience has been achieved on all sub-systems, components and materials used on the prototype. Allmost all subsystems (remote control, frequency converters etc.) have subsequently been improved
- Turbine re-design: Operating and maintenance experience from running the turbines in an offshore environment has led to a number of modifications on the turbines
Results from prototype testing has been published; primarily by scientists at Aalborg University and Technical University Munich in co-operation with the Wave Dragon team. For more info on the test- and development-activities, please refer to the papers and articles in the download section.
In a project co-funded by the Danish Energy Agency and the European Commission, a model Kaplan turbine – especially designed for the low and varying heads and flows – was developed and tested with very promising results. This and 6 new turbines were installed on the prototype. Based on the results of the Kaplan turbine testing the new turbines are propeller turbines (fixed blades) with fixed gate vanes.
Following the EU Joule Craft project, the geometrical layout of the Wave Dragon was somewhat modified. Wave tank tests on this new design were performed at Aalborg University, resulting in significantly improved overtopping characteristics – without sacrificing survivability. This design has been implemented in the prototype.
The prototype is designed as a 1:1 (full-size) model relative to the wave climate in Nissum Bredning. This corresponds to scale 1:4.5 for a North Sea Wave Dragon and scale 1:5.2 for a Wave Dragon in a 36 kW/m wave climate.
Due to scale effects the rated power of the Nissum Bredning prototype will be 20 kW resembling 4 MW when deployed in a relatively low-energy (24 kW/m) wave climate and 7 MW when deployed in a 36 kW/m climate.
The prototype activities has established the necessary knowledge to deploy a full-scale Wave Dragon.