Wedge Global

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"Wedge Global, riding the wave of clean energy"

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Wedge’s Mission:

  • Created in 2008 to develop an innovative solution for generating electricity from ocean waves (wave energy), a new and steadily growing segment within the renewable energy industry.
  • To reduce wave electricity production costs to sustainable levels through technology development, operational excellence and scalability to ultimately compete with conventional generation.
  • To provide an integrated, portfolio-based approach to project economics from site selection and project development through transmission access, power purchase agreement and project asset sale.

Wedge’s Strategy:

  1. Optimizing the performance of the Company’s proprietary power-take off system consisting of a switched reluctance and high force density linear generator for use with existing point absorbers. The Company’s first prototype has been completed and is currently undergoing laboratory testing.
  2. Developing its own wave energy converter (WEC), either individually or through partnerships with other technology developers, in order to provide clients with a complete turnkey solution.
  3. Identifying sustainable wave energy markets and participating in the development of new projects, including the installation and ongoing operation/maintenance of wave farms.

Overview:

Wedge Global combines the most important aspects within the wave energy value chain, including design, manufacture, testing and commercial application. These capacities help to strategically position the Company to play a leading role in the future development of wave farms and to become leading a leading manufacturer of components and a turnkey supplier of projects on a worldwide basis.

The Company’s current product consists of a worldwide patented design for a switched reluctance linear generator to be used in a resonant point absorber. A prototype of this generator has already been been and is currently undergoing laboratory testing as shown in the image below.

As part of its next phase of growth, Wedge is planning to also design, manufacture and test electrical devices (submarine transformer, connectors, etc) for the WEC grid connection and to develop its own point absorber.

Technological Breakthrough:

A considerable body of work has been completed on the research and development of linear induction generators as the main PTO element in wave energy converters. Most of the theoretical and laboratory work has been based on permanent magnet machines.

At least two wave energy converters, fitted with PM linear generators, have reached sea testing stage (AWS and Seabased). There are disadvantages of permanent magnet linear generators for wave energy conversion, notably that the device is necessarily significantly overrated most of the time. High capital costs and the need to re-magnetise are other negatives. Most telling perhaps for a point absorber is the inflexibility of such a PTO, inhibiting effective control.

Switched reluctance technology is well developed in motors, usually for high speed rotary applications. Wedge Global have filed for PCT protection for their innovative use of two translators placed between two lateral stators and a further intermediate stator. This solution balances the lateral magnetic forces, at the same time doubling the machine’s installed capacity with only half the additional investment in stators.

The SRLG concept is based on three stators and two translators. The stators allocate the coils creating the magnetic field and extracting the power, and are equivalent to the stators of a rotary electrical machine. The translator has no coil, just iron yokes, and is equivalent to the rotor of a rotary switched reluctance machine.

Assuming resistive losses in the copper coils to be the dominant loss mechanism, it was found that efficiencies in the order of 75%-85% are achievable with switched reluctance linear generators under typical conditions. However, a more extensive independent simulation should be performed to verify the switched reluctance linear generator expected performance.

A notional schematic representation of a resonant point absorber with switched reluctance linear generator is depicted below:

Resonant point absorber with switched reluctance linear generator

The stator includes the machine coils which are connected to the SRLG-side electronic converter. This converter is responsible for supplying the machine phase with the appropriate current to get the required dynamics in the generator. The SRLG-side converter (MSC) is connected to the grid-side converter (GSC) by means of DC-link (1000V). The grid side converter is in charge of maintaining the DC voltage level, delivering the power into the grid with the adequate quality level. Both converters are bi-directional, which allows the SRLG to work as motor as well as a generator. The grid-side converter is equipped with both grid protection devices as well as devices to guarantee the power quality (harmonics, voltage level…). After the converters, a transformer might be needed to increase the voltage from 1 kV to the voltage required at the grid interface.

To minimize the costs related to production, maintenance and spare parts supply and refurbishment, it is currently envisioned that the switched reluctance linear generator will be a modular component that can be replaced easily as a whole. As such, it is not expected that the switched reluctance linear generator will form an integral part of the resonant point absorber structure. Furthermore for ease of maintenance and repair, each coil can be (dis-) assembled as separate modules on their own.

Competitive Advantages:

There are several advantages that can be obtained from a switched reluctance linear generator application in a resonant point absorber wave energy converter as compared to the traditional hydraulic solutions. Many of those advantages derive directly from the fewer number of energy conversion steps and the reduced number of components involved. The figure shows the difference in number of components from a "wave-to-wire" point of view.

"Wave-to-wire" generic power conversion chain for hydraulic and switched reluctance linear generator PTO.

Specific advantages of switched reluctance linear generator technology with respect to hydraulic PTO include:

  1. Better control based on electronic converter: faster, less losses, reverse power flow
  2. More power: total 75%-85% efficiency
  3. Lower CAPEX equivalent to hydraulic PTO, easy to outsource.
  4. Lower OPEX as maintenance is dramatically reduced and reliability incremented
  5. Other advantages include: power scalability, better ground failure protection, more speed more power.