Wave Dragon wave-wind project

Abstract

Wave Dragon wave-wind project

Wave power is more consistent than wind-, solar- and tidal power. Wave is at the same time more predictable than wind and solar. The paper assesses the economic performance of the different wave energy converter (WEC) types and discusses the possibility for WECs to match the levelized cost of energy for offshore wind. Utility size wave energy parks may become a viable solution by using large WECs, but at sites with reasonable wind climates it is not possible to match the power price from bottom standing wind turbines. Large floating WECs carrying wind turbines can, however be very competitive at good wave-wind climate sites with water depths above 60 m.

The development of the Danish type horizontal-axis 3-bladed wind turbine was kick started by the oil crisis in the early 1970s with series production of 22kW windmills. The World’s first offshore wind park with 11 units and a total capacity of 5MW was inaugurated in Denmark less than 20 years later. The plant was in operation for 25 years. The upscaling of the Danish wind turbine has continued, and today’s offshore turbines have a power of more than 10MW. The reason for this large upscaling of offshore wind turbines is primarily the reduction of balance of plant costs and lower OPEX.

Many hundred types of small WECs of power (in full scale) comparable to the first commercial windmills have been tested, but very few WECs comparable in power to the first offshore windmills have until now been tested - and no MW size WECs. Like windmills offshore WECs need to be scalable to more than MW sizes to be feasible.

Wave Dragon is an overtopping system that is designed to lie still even in large waves and can therefore, in principle, be scaled up without limit – the efficiency will actually increase with size.

Wave Dragon is planning to deploy and validate an offshore 1.5 + 1.5MW wave-wind platform at a site with an average wave climate up to 6 kW/m and a max significant wave height of around 8 m. Test sites with the needed conditions can be found at the Danish test site DanWEC in the North Sea and at PLOCAN in the Canaries. 

The WD platform stands out from the most known wave energy devices by bringing together proven technologies put together in a novel way and it was world’s first grid connected floating WEC when it was successfully tested in scale 1:3 of a 1.5MW device. The PTO system is based on industry standard propeller turbines installed in a power smoothing water reservoir offering improved reliability and reduced power variability. 

Test of a floating model in scale 1:50 of the 1.5 + 1.5MW wave-wind platform is planned at AAU, and preliminary results shall be reported in the paper. Feasibility studies for very large WD wave-wind devices with capacities up to 38 MW suitable for wave climates above 36 kW/m are also planned with input from previous WD studies and tests without windmills.