WaveRoller - Ocean Wave Converter Device
WaveRoller is a device that converts ocean waves to energy and electricity. The machine operates in near-shore areas (approximately 0.3-2 km from the shore) at depths of between 8 and 20 meters. It is fully submerged and anchored to the seabed. A single WaveRoller unit (one panel) is rated at between 500kW and 1000kW, with a capacity factor of 25-50% depending on wave conditions at the project site.
Product Details
The story behind the invention
The simple yet very powerful idea for the design of WaveRoller came in a moment of enlightenment when Finnish professional diver Rauno Koivusaari was exploring a shipwreck. He noticed that a very heavy flat piece of the ship’s body was moving back and forth, driven by the energetic under-surface surge of water, the ocean waves. Since that first moment of insight the WaveRoller design has gone through multiple cycles of building prototypes, testing them in laboratories, conducting highly sophisticated simulations and numerical modelling, and finally deploying the test devices in the real ocean environment to make observations, adjust the scale and repeat the development cycle.
How it works
WaveRoller behaves in essentially the same way as the flat part of the wreck that Rauno observed. The back and forth movement of water driven by wave surge puts the composite panel into motion.
To maximize the energy that WaveRoller panel can absorb from the waves, the device is installed under water at depths of approximately 8 – 20 meters, where the wave surge is most powerful. The panel spans almost the entire depth of the water column from the sea bed without breaking the surface. This ensures that the panel does not protrude onto the seascape and prevents the creation of material inefficiencies that would put additional load on the structure.
As the WaveRoller panel moves and absorbs the energy from ocean waves, the hydraulic piston pumps attached to the panel pump the hydraulic fluids inside a closed hydraulic circuit. All the elements of the hydraulic circuit are enclosed inside a hermetic structure inside the device and are not exposed to the marine environment. Consequently, there is no risk of leakage into the ocean. The high-pressure fluids are fed into a hydraulic motor that drives an electricity generator. The electrical output from this renewable wave energy power plant is then connected to the electric grid via a subsea cable.
Power production and operations
The power output from a single WaveRoller device, or in other words output from a single panel, ranges between 500 and 1000 kW. The differences in power production result from the local wave resources (see more in Wave energy resources globally).
When multiple WaveRoller devices are installed at a single site, we talk about wave farms or arrays. These farms can include tens of devices, so that part of the infrastructure of the site is distributed among the machines, thus reducing the cost of an individual unit. Since each WaveRoller is equipped with an on-board electricity generator, the output from many devices can be combined via electricity cables and a substation. Large wave farms have nominal capacity of a utility-scale power plant.
One of the unique features of WaveRoller that ensures its cost effectiveness in delivering reliable power output is its distinctive operation and maintenance concept. WaveRoller units feature large ballast tanks that are filled with air so they can be floated to their deployment locations. These tanks can be flooded with water to submerge the unit. Although the wave energy converter remains fully submerged during regular operation, it can be easily re-floated on the surface for maintenance by emptying the ballast tanks. There is consequently no need for complex, costly and potentially hazardous diving operations when maintaining WaveRoller. Additionally, the device can be installed or serviced without additional costly equipment such as large cranes or jack-up barges.
Site Selection
A number of different factors affect successful site selection. A meticulous approach to project implementation requires that developers consider not only the site resource and technical points of view, but also environmental issues and other current uses for the location of the planned implementation. The WaveRoller team brings its specialized expertise gained from years of field work as a pioneer in near-shore wave energy development to site selection. Heavy investments in the tools required for site resource assessment and micro-siting of this type of technology are also important aspects of a successful project.
The site selection process for WaveRoller wave farms typically begins with a high-level analysis of wave energy resources available along the shores within the scope of the project. Once the areas with the highest potential have been identified, we conduct a more in-depth analysis of site candidates. Apart from more detailed analysis of the micro-site wave climate, including the study of the seabed shape (bathymetry) and structure (sediment), we evaluate environmental and spatial planning building blocks.
Completing this kind of detailed site feasibility study, allows us to more accurately estimate the potential power output from the planned WaveRoller wave farm and to move forward with project development.
Testing
Testing is not only an essential part of WaveRoller technology development, but it is also deeply rooted in the manufacturing and operating processes. During many years of the technology development, we have crystallized a standard operating procedures that yield incremental improvements at every cycle of the development.
In our research and development activities, we run cycles where each iteration of technology development combines inputs from numerical modelling, scaled tank tests and open sea tests.
In addition to developing in house expertise in numerical simulations and computational fluid dynamics we cooperate with universities, research institutions and specialized engineering firms to ensure that our estimates and simulations are reliable. We place heavy emphasis on identifying the weakest links in the design at an early stage, when errors are easier to identify and eliminate.
To further validate the results of the computer simulations, we conduct wave tank tests. Scale models allow us to analyze whether calculations are correct and reliable. It is much more cost effective to test a smaller-scale unit in a wave tank, compared to building a full-scale unit and finding design errors at that advanced stage.
Once theoretical calculations and wave tank tests prove the design reliable, it is possible to building larger-scale WaveRoller units that to be operated in real sea conditions. Apart from generating electricity, the units continue to provide to an invaluable stream of performance data in the field. This information is used to further improve the performance and reliability of subsequent generations of WaveRoller.
One of the advantages of WaveRoller technology is the fact that we can reliably and cost efficiently validate the functionality and performance of our devices before they are even deployed in the ocean. While bench testing is possible on land, it can also be used to simulate real sea conditions.
The data representing sea states is fed into a test rig, which transfers the energy to the tested device in the same way as if the device was absorbing energy from the waves. The absorbed energy is, in turn, converted into electricity by the generator running inside the tested WaveRoller. We can thus measure the performance of the device, as well as, ensure that it works properly before installing it in the sea.
Operation & Maintenance
Since WaveRoller doesn't require any fuel, the main cost drivers during the life of a project are operation and maintenance. WaveRoller addresses these issues with a smart design that combines proven submarine technology with remote condition monitoring and control systems.
Maintenance always on surface
WaveRoller units can float without any external support. This feature makes it relatively cheap and easy to tow the devices to and from the project site. We deploy the units by flooding the ballast tanks with water - causing the device to sink to the sea bed where it can commence normal operations.
For service or maintenance, we simply pump air back to the ballast tanks, so that the WaveRoller unit can rise to the surface. Operators can then access the machine rooms directly on site or tow the device to a suitable location closer for maintenance work. This intelligent design also allows us to address a very important health & safety issue.
Remote condition monitoring & control system
The WaveRoller unit is controled remotely, making it possible to access device performance and condition data in real time from multiple locations around the globe. This data is collected via an array of sensors located inside the device. In addition monitoring the quality of the power output, remote monitoring provides data about the conditions inside the device and the behaviour of its individual components. The performance and condition data serve for many purposes.
- To identify any potential faults or maintenance needs
- To adjust the WaveRoller to respond to the sea state and ensure optimal power output the prevailing wave conditions
- To collect data for long-term performance analysis
- To provide data for R&D inputs for future generations of WaveRoller
Wave Farms
A series of WaveRoller devices can be deployed into an array to create a wave farm. Since WaveRoller is constructed as modular individual units, there is no natural upper limit to the number of devices that can be used in an array, therefore offering a high level of scalability and reliability.
The electricity output from an individual WaveRoller panel travels to a hub or substation, making it easy to plug in new units in separate project development stages to introduce additional capacity to a wave farm. The modular design of the units means that any potential underperformance or service and maintenance breaks in individual units have no impact on the remaining devices, ensuring uninterrupted power output from the farm.
Layout is an important factor in the installation of a WaveRoller wave farm. In fact, the power output from the farm may vary significantly depending on how the units are positioned in relation to each other. Our extensive experience gathered from installing and running WaveRoller arrays in the open sea environment, as well as results from array tank tests ensures that we can assist our customers with optimal layout design for specific project sites.
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