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Drakoo Wave Energy Converter


Hann-Ocean has developed a novel design concept for wave energy conversion, namely “Drakoo” Wave Energy Converter. This is a system for absorbing, transforming and converting wave energy into electricity while reactively cancelling or reducing reflective wave energy in the ocean. The Drakoo can absorb the ocean wave’s kinetic energy and drive hydro-turbine(s) and generate electricity. The highly optimal design of the Drakoo enablesto achieve high energy absorption efficiency for ocean waves with wide range of wave heights and periods. Drakoo is therefore a cost-effective and reliable solution for wave energy absorption and conversion to electricity.

The Working Principle


The working principle of Drakoo, being a twin-chamber oscillating water column system, is to transform waves into a continuous water flow which drives a hydro turbine generator.

The Drakoo operation sequence is as follows:

Firstly:an incoming wave increases the inlet chambers’ water level, while simultaneously water is partly directed from the inlet to the outlet chamber, through the hydro turbine.

Secondly: once the water level outside the device falls, both chambers’ water levels also fall, leading to a flow from the inlet to the outlet chamber and the outlet chamber to the outside environment.

The two-step action of the water columns occur continuously in waves. Meanwhile, the checkerboard valves regular the water flow. The water flow is nearly constant and one-directional resulting in smooth rotation of the hydro turbine which in turn generates stable electricity efficiently.

Performance


Verified by National Renewable Energy Center (Narec, UK), Drakoo has consistently achieved a wave-to-hydro power conversion efficiency, defined as Capture Width Ratio (CWR), beyond 80% at peak and 50% on average in regular waves over wide wave spectrums. The latest commercial model Drakoo-B0010 (10kWp) has been proven to achieve a peak conversion efficiency (i.e. waves to electricity) of close to 50%.

Key elements


Drakoo consists of three typical features:
Twin-chamber Body
Checkerboard Valves
Power Take-off System
A unique integration of these three features was invented and have been developed by Hann-Ocean. The system can be customized and optimized for different wave conditions. With the use of a specially designed composite for checkerboard valves, matured permanent magnetic generator, a matured hydro turbine technology, and economical materials, Drakoo is a simple, efficient, of modular design and gives a strong competitive edge over other wave energy converters.

Advantages

Drakoo is the world’s first WEC that works efficiently under very small wave condtions. The main advantages include:

Applications


Fixed Modular Drakoo WEC Array


Drakoo-B design works in fixed mode, verified by Narec UK. Drakoo-B is also a modular concept which suits well for construction of wave energy array where the Drakoo units are installed side by side. In sea waters with little tidal level changes, Drakoo-B can be fixed onto the shore, seabed or rigid breakwater as long as the draft of the device remains sufficient in common tidal conditions.

Floating Modular Drakoo WEC Array


Drakoo-B design also works in floating mode, verified in repeated prototype sea trials. Drakoo-B is designed with a modular concept and can be used to build a floating wave energy array where the ‘Drakoo’ units are joined by welding or Rigidfloat Rigid Pontoon Connectors. In waters with large tidal level changes, Drakoo-B is recommended to stay afloat to maintain constant draft for efficiency.

Drakoo can float on water by self-buoyancy or it can be attached to existing floating structures, including floating wind turbines, semi-submerged oil rigs, floating jetties or floating breakwaters. Furthermore, it can be integrated in offshore production platforms or ships to generate electricity for local consumption.

Floating Stand-alone Drakoo WEC


The Drakoo-R design is of a round-shape and stand-alone floating wave energy converter. It is designed to operate in large waves (2.5m – 5.5m high) and produce mega-watt scale electricity in any wave heading in the ocean. It can produce low cost electricity for utility scale offshore. The research and development works are currently in progress.

Wave Absorbers


The Drakoo technology extracts wave energy as a static or semi-static system (fixed or floating-anchored) that protrudes the water surface. It absorbs the wave energy and able to convert the energy to electricity. Integrating Drakoo-B WECs onto fixed breakwater design, it absorbs the incident wave energy rather than reflecting sea waves. It blocks the waves from transmitting to the sea behind and reduces wave breaking in front of the breakwater.