Technology

Symphony Wave Power: what is it?

Symphony Wave Power is a technology that converts the power of the ocean into clean, renewable energy. Wave energy is believed to be a great opportunity with a potential comparable of even bigger than the offshore wind industry. The technology of Symphony Wave Power is highly efficient, invisible and sustainable, has a simple design and a scalable technique. That is why we believe Symphony Wave Power is the new wave of invisible energy.

 

Highly efficient

  • Hydraulic pointabsorber technology 
  • 300% to 500% more efficiency compared to non-resonant systems

 

Simple design

  • Low number of parts
  • Long intervals for maintenance
  • Robust design with high reliability and survivability

 

Invisible & sustainable

  • Submerged and therefor invisible
  • Limited space needed
  • Made of recyclable materials
  • Environmental friendly: little impact expected on biodiversity

 

Scalable technique

  • Same design for different wave conditions
  • Designed for arrays
  • Learning curve

Result of 25 years of experience

History

The technology of Symphony Wave Power is a novel technology based on more than 20 years of experience in wave and tidal business. The technology is a product of co-creation between science and industry led by Teamwork Technology BV in the Netherlands. It represents the know-how of a network of expertise over Europe and beyond. Developed with public support, including from the European Commission, and with the expertise of the offshore industry.

The Symphony Wave Energy Converter (WEC) technology is robust enough to survive the worst case conditions and sophisticated enough to convert wave energy into electricity in a highly efficient way

 

Environmental Friendly

The working principle

The working principle of Symphony can be explained shortly as a device with an internal spring that resonates at the wave frequency. Even small waves will attenuate the Symphony motion up to the full stroke. The generator damps this motion by extracting electrical energy.

The system is placed ca. 6 meter under the still water level and will experience a pressure field under the wave crest. This will push the outside hull down and compress the air inside. Under a wave through the air will expand and push the outside up again.

If the natural frequency of the system is close to the wave frequency, it will be able to abstract energy from a larger area than its own diameter. This is called point absorption in wave energy literature. This phenomenon has been studied extensively, but not many devices have been able to apply it, also because it is potentially destructive: as the device charges itself with energy, it will hit the mechanical endstops and destroy itself. In Symphony Wave Power, the endstops are integrated in the shape in which the membrane rolls. This gives the endstop the characteristic of a stiff spring – a buffer that not dissipate the energy, but returners it into the system. By doing so, it causes a small delay which lowers the intake of energy.

 

Inside the Symphony is a double-acting structural roll membrane. Inside this membrane is a liquid. This liquid is pressurized by the gas on top of the liquid. As the gap from the upper membrane is larger than the one from the lower, the liquid moves in and out of the pressure chamber as the hull moves up and down. As the air volume decreases, the pressure increases. This increase gives a higher force on the membrane and drives the hull upwards once the pressure in the wave pushing on top of the device decreases. This causes the hull to start moving up. The air volume together with the membrane acts like a spring, which must be tuned well according to the mass. This is done by the size of the air volume, making the device resonate at the dominant wave frequency. Looking at the time series in the graph shown above one can see that the device moves at its full stroke, even on low waves. During this motion, the energy captured is calculated by the force of the wave times the stroke. In this way power can be converted even from low waves.

 

[The black line represents the wave, the blue line represents the motion.]

 

Simple Design

Only two key components

With Symphony we introduced a number of innovative features that replace the function of critical parts existing in other designs. The Symphony WEC contains in the end only two critical or key components. These are the structural membrane and the turbine. Both are new, patented technologies. By implementing these two elements together with specific structural measures, known key vulnerabilities of heaving WECs can be  eliminated or mitigated, including bearings, end-stops, hydraulic pistons, a linear generator and the large air volume.

 

Although the Symphony key components are novel, they have been carefully designed and undergo rigorous testing. The membrane is designed, built and tested by Trelleborg. The turbine has been tested since 2018 (thanks to the in2sea BASEPOINT project in Sines, Portugal) and after two iterations of turbine blade and functional optimisation has undergone new tests until 2021.

Invisible & Sustainable

Placed in arrays

Symphony Wave Power is an invisible source of energy. It has zero visual impact as the buoys are placed in arrays (of 6 or more buoys) underneath the water surface, requiring 20 meter of water depth. The arrays require limited space. As the energy transition is speeding up not only pricing, but also the availability of space and location is becoming more of an issue.

 

 

The artist’s impression shows the possibility to share the grid infrastructure in coastal areas between offshore wind turbines and Symphony Wave Power, to make better use of the limited ocean space through MUS solutions (Multiple Use of Space). In addition to operational advantages and cost reduction, this limits further restriction of areas for fishery and other shipping.

 

In deeper water (+30 meters) a promising combination to share the infrastructure is possible, as indicated in the artist’s impression. In even deeper areas floating wind turbines can be co-located with underwater arrays of Symphony Wave Power devices. Also energy storage becomes more and more crucial. The production of this green hydrogen may play a crucial role for the energy transition in the next years. Symphony will therefor develop a wave converter specifically suited to produce hydrogen at off-grid locations.

Scalable Technology

Product portfolio

Symphony Wave Power BV is planning to extend its product portfolio in the future. First with a larger Ocean Version, second with hydrogen production and storage units in order to increase stability of electricity delivery.

 

Currently the protype is being tested. A 100kW version is designed for the North Sea with relative low waves and requires a water depth of 20 meters or more. Once the design is tested in the water, the technology will be extended to develop an Ocean version of 900kW.

 

By enlarging the diameter up to 200% but limiting the highest operational wave to ca. Hs 3m, Symphony still has a 90% availability while limiting the cost for the power-take-off components. These systems could be placed between wind turbines, and in remote areas, as no grid connection is needed. Because of this and the sophisticated fast connection single point mooring system, this provides the possibility for a “fast roll out”.

Highly Efficient

Comparison to other systems

Because the Symphony is a resonant system, it is capable of extracting more energy than most other systems. The simple reason for this is that many other systems, especially buoyant systems have a too stiff spring. The spring is based on its displacement of water as a function of displacement, as the mass is fixed (equal to the displacement of water in its middle position). Most buoyant systems have a natural period of ca. 5 seconds. This makes them move with the waves instead of a motion that is slightly delayed. See both figures below.

The left figure represents a “normal” buoy following the wave motion, while the right figure depicts the buoy movement in a resonant system. The blue line is the wave, the thin, non-dashed line the position and the dashed line the velocity. The pressure of the wave times velocity gives the power output. In the left figure the lower power out and – during part of the motion even a negative power – are visible. This is caused by the device moving down while the wave is still positive.  Most buoyant wave energy systems have found ways to mitigate this problem smaller.

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