HOW IT WORKS| HOW IT SURVIVES | ADVANTAGES | ROAD MAP | PARTNERS

InfinityWEC – at the forefront of wave power technology

InfinityWEC is a novel point absorbing Wave Energy Converter (WEC). It is both highly efficient in capturing energy through its ability to adjust to the sea state, and robust enough to operate reliably and survive the harshest marine conditions. Cost efficiency is achieved by its modular design and the easy handling, allowing for road transportation and requiring a minimum of offshore operations.

The system is installable with a minimum of complicated offshore operations and no diving or heavy lifting are necessary offshore. An anchor cage is lowered to the seabed with a crane and filled with 500 ton high density ballast from an installation vessel. The buoy and PTO are towed separately to the installation site. The PTO is connected to the anchor and then to the buoy by pulling the mooring rope from the PTO through the center of the buoy. The InfinityWEC technology and design is patent protected and developed by Ocean Harvesting Technologies AB in collaboration with experienced partners.

InfinityWEC is developed according to the following Design Principles, to achieve high performance, low cost and to be prepared for high volume production and roll-out

OHT-Design-Principles-July-2022-2Download

Technology Advantages of the
power take-off

Only Proven Subsystems

  • Uses only proven subsystems available from established suppliers
  • Designed for factory production, transportability (road, railway and sea),
    and for fast installation on site

Instant Force Control Capability

  • Hydraulic pre-tension spring (1 MN force) combined with two direct drive ball screw actuators (± 1 MN force) provide instant force control from 0 – 2 MN force
  • Enables efficient predictive reactive force control to maximize energy output from every wave. Up to 30% higher annual energy production compared to non-predictive control

Passive Survival Function

  • Hydraulic cylinder attached below main PTO to adjust its height for tidal variations
  • Gas accumulators connected to the cylinder provides a soft end stop spring, holding the buoy submerged through the crest of large waves.
  • The end stop spring in the level cylinder is activated by the end stop cushion in the pre-tension cylinder, which reduces the end-stop force by 30%.
  • Ensures survival and reliable power production even in the harshest conditions

Buoy made of high-strength concrete

Ocean Harvesting is developing a novel concrete hull for the prime mover (buoy) of the InfinityWEC wave energy converter, using high strength concrete, with low environmental footprint and excellent durability. The solution allows for large scale production and results in a buoy with similar weight to a conventional steel hull, but at a quarter of the cost, a third of the CO2 footprint and one tenth of the manufacturing time.

Highly flowable concrete is poured into a mould with void fillers, forming the concrete shell and the internal honeycomb structure, one of the strongest structures in nature. Most of the raw materials will be sourced locally at the installation site, where the buoy is cast in a process common in civil engineering. The buoy will be towed or shipped to the installation site and linked to the InfinityWEC PTO system with a mooring rope, which enables quick and diverless attachment and detachment of the buoy from the PTO system during installation and maintenance operations.

The RISE (Research Institutes of Sweden) department for Infrastructure and Concrete Technology has developed a unique high-performance concrete mix for the buoy, as part of the joint industry project WECHull. To facilitate a thin-walled, lightweight structure and easy, rapid manufacturing, alternative reinforcement measures were investigated, evaluating the use of fibres of different types (carbon, aramid, glass, steel and biomass), as well as polymer reinforcement with carbon-textile grids. By using recycled aggregates and replacing more than 50% of the cement content, InfinityWEC’s buoy is aligned with the European Circular Economy Action Plan.

How it works

Advanced reactive force control on the buoy is provided throughout the full wave motion, which greatly amplifies the energy output and minimizes cost by limiting loads.

Direct drive ball screw actuators in combination with a hydraulic pre-tension spring system provide highly efficient PTO force control capability at a low cost.

  • The waves lift the buoy, together with the pre-tension cylinder and the ball nuts attached to it with the upper mooring rope.
  • The pre-tension cylinder is connected to a piston accumulator with a large gas volume and applies a constant spring force, providing half of the available PTO control force.
  • The vertical motion of the ball nuts causes the ball screws in the PTO hull to rotate, driving the frameless torque motors (generators) directly connected to the ball screws.
  • Variable Frequency Drives are used to apply bi-directional torque up to ± 50% of the available PTO control force, enabling instant stepless control from 0 – 100% together with the pre-tension spring.
  • A second hydraulic cylinder below the PTO hull adjusts the position of the PTO hull to the tidal variations.

How it survives

InfinityWEC does not have a survival mode where power production is shut down in strong sea states, instead it uses a passive survival strategy allowing power to be produced in every wave.

A novel two-stage end stop cushion system holds the buoy submerged through the crest of large waves.

  • The first stage is a cushion in the pre-tension cylinder, which increases the cylinder force to stop the motion of the heave system just before the end of stroke.
  • The second stage of the cushion is a hydraulic spring in the level cylinder, allowing the PTO to be pulled up along with the buoy up to about 2 meters until the motion stops and the buoy is held submerged through the crest of large waves.
  • After a submerge event, the PTO is returned to its previous position by the hydraulic spring, making the system ready to capture power in the next wave.
  • The two-stage end stop cushion reduces the required control force and stroke length of the heave system, and stops the buoy motion with a low deceleration force.
  • This greatly reduces the cost of the InfinityWEC and improves the energy output and reliability.

Advantages of InfinityWEC

Solving the challenges of wave energy

Our technology has the potential for cost effective electricity generation to main power grids, as well as to off-grid applications.

  • Through our advanced power take-off and force control technology, we achieve high energy output at low cost.
  • The passive two stage end-stop cushion system protects the system from excessive forces and enables power to be produced also in the harshest conditions.
  • Through energy storage we address the challenge of ensuring a constant and predictable power output despite the high short-term variability in wave power generation.
  • The system is modular and suitable to produce in large scale, and is also made from parts and materials that can be easily transported and assembled on any location.
  • Our technology has the potential for electricity generation for main power grids as well as for off grid applications such as isolated areas, island communities, oil & gas platforms and fish farms.
  • Only proven technologies from other industries are used and integrated in the InfinityWEC system, enabling fast and capital efficient route to market.
  • Wave energy requires less than 1/10 of the area needed for wind power, due to the higher energy density in waves compared to wind, and can be placed much closer to the shore-line, since the visual impact is virtually zero.
  • The estimated LCoE is highly competitive to wind and solar energy at 100 EUR/MWh already at 100 MW deployed capacity, and 35 EUR/MWh at GW scale deployment.

Road map

We follow the staged development method set out by the international marine energy community

OHT is since 2017 developing the novel InfinityWEC wave energy converter with advanced force control and with AI capabilities. We have an extensive know-how in the wave power application and patent protection covering all aspects of the InfinityWEC system. To mature the concept we have developed tools to accurately assess dependencies between design and the overall life cycle cost of the system. We believe in using numerical models to time and cost efficiently simulate the behavior, loads and performance of the system, and to verify them with limited and controllable physical tests. This ensures we are on track to a commercially viable system before we move into large scale prototypes and testing.

We are currently preparing for sea trials of a fully operational InfinityWEC in scale 1:3 on the west cost of Sweden.

In 2025 we plan start the sea trial project of a full-scale 500 kW InfinityWEC, after which our system is validated and certified, followed by our first commercial installations.

Partners