Judges have completed reviewing the technical submissions and a total of 20 Qualified Teams are advancing to next phase of the Wave Energy Prize! Here are the entries.
Contributed by | Wave Energy Prize
The Wave Energy Prize is a public prize challenge sponsored by the U.S. Department of Energy (DOE)‘s Water Power Program. The prize is designed to increase the diversity of organizations involved in Wave Energy Converter (WEC) technology development, while motivating and inspiring existing stakeholders. DOE envisions this competition will achieve game-changing performance enhancements to WEC devices, establishing a pathway to sweeping cost reductions on a commercial scale.
The wave energy industry is young and is experiencing many new innovations as evidenced by a sustained growth in patent activity. While the private industry is developing these early-concept WEC devices through design and benchtop prototype testing, funding is hard to secure for performance testing and evaluation of WEC devices in wave tanks at a meaningful scale. This is a problem for the industry since scaled WEC prototype tank testing, validation, and evaluation are key steps in the advancement of WEC technologies through the technical readiness levels to reach commercialization.
The Wave Energy Prize will encourage the development of more efficient WEC devices that double the energy captured from ocean waves, which in turn will reduce the cost of wave energy, making it more competitive with traditional energy solutions.
Judges have completed reviewing the technical submissions and a total of 20 Qualified Teams are advancing to next phase of the Wave Energy Prize!
Advanced Ocean Energy @ Virginia Tech
Hampton Roads, Va.
Virginia Tech’s MULti-body LinEar Terminator (MULLET) is a self-contained array of Bundled pIpe Terminator Wave Energy Converters (BITWECs). Each BITWEC is a floating bundle of large-diameter, high-density polyethylene (HDPE) pipes. The basic MULLET building block is a “tandem BITWEC” whereby two pipe bundles are arrayed one behind the other in the down-wave direction.
Each bundle is tethered by a pair of flexible fiber matrix composite tube pumps to the deeply submerged deck of a pontoon barge, which also is fabricated from large-diameter HDPE pipe sections, as shown in the conceptual diagram, below. Seawater output from the tube pumps is piped to an underwater habitat housing an accumulator and Pelton turbine-generator.
The MULLET barge is assembled while floating in calm water at dockside and then towed to its offshore installation site. Once on site, the barge is connected to a pre-set catenary anchor-leg mooring (CALM) buoy. The barge pontoons and CALM buoy are then flooded with seawater, submerging the barge to its mid-water operating position, where the barge deck acts as an inertial reaction plate for the floating bundles to work against, stretching the tube pumps. For inspection and maintenance, the barge and CALM buoy are re-floated to the surface by reversing the installation procedure.
AquaHarmonics' Wave Energy Device is a point absorber device consisting of a simple Power Take Off (PTO) system mounted in a cone/cylinder shaped hull with a single mooring line that has a power cable at its core.
The PTO System consists of a sheave fixed to a shaft mounted in bearings within a sealed compartment and directly coupled to a pair of axial flux generators. The device only generates power on the rise of the wave, and during the fall of the wave the generators are operated as motors to reel in the mooring line for the next wave cycle.
During reel in, the control system of the device can provide additional energy input to achieve phase locking with any wave frequency. This control method is known as "de-clutching," which has been shown to effectively increase the operational bandwidth of a wave energy device.
The generated power is far greater than that consumed during the wave cycle with some energy stored on board for periods of low wave activity. The power is conditioned on board and sent to shore via a slipring on the shaft connected to the power cable located at the core of the mooring line.
Atlantic Wavepower Partnership
The AWS-III is a large-scale surface floating multi-absorber wave energy converter. Each absorber cell comprises a partially submerged air-filled chamber, one face of which is covered with a rubber diaphragm which flexes in response to the incoming wave actions. The movement of the diaphragm pumps air to and from the cell via an air turbine-generator set where the energy is converted to electricity. The cells are inter-connected via a ring-main such that air is exchanged between cells rather than with the outside environment.
All mechanical moving parts are isolated from the sea and contained within the device, whilst the turbine technology is tried-and-tested and available on the commercial market. The device is moored using traditional systems for offshore structures, either catenary systems and drag-embedment anchors or tension tethers and suction anchors. Accordingly, the device is utility-scale and has low technical risk and is capable of on-board maintenance of all parts with the exception of the diaphragms. Initial systems are expected to be rated at 2.0MW.
Atlas Ocean Systems
The Atlas Ocean Systems SQ5 Wave Energy Converter is a completely new device that captures energy primarily from pitch using two independent coupled oscillators. The SQ5 consists of three primary elements: 1) a float, 2) a new innovative submerged bag filled with air under pressure, and 3) a large submerged ballast. The bag and submerged ballast are essentially in static buoyant equilibrium. The catamaran float provides roll stability and resonates in pitch with the waves and transfers vertical motion to the bag system which then excites a vertical oscillation of the submerged ballast. The oscillation of the ballast drives shape changes within the bag to pump air through a reversible flow turbine to generate useful energy. Pitch response of the float is adjustable in real-time using a ballasting system and coupling between the float and ballast is adjusted during design. Coupling between the two oscillating systems provides a wide dual-peak absorption spectrum providing good power output over a variety of sea states. There are no mechanical moving parts, seals, hinges, or pistons requiring lubrication or maintenance. The turbine system is protected within the pressurized pneumatic system and is suspended in a transverse mounting minimizing gyroscopic forces. The nominal system is designed for a 500kW-1MW rating.
CalWave provides a solution to harness the renewable power of ocean waves to produce electricity and freshwater. Our device is a novel Wave Energy Converter (WEC) called the WaveCarpet that is simple and scalable. Our innovative approach was inspired by the ability of a muddy seafloor to effectively absorb overpassing ocean waves within only a few wavelengths. The unique converter design uses a synthetic-seabed-carpet that has the ability to extract wave energy the same way.
The technology is based on research conducted at the Massachusetts Institute of Technology (MIT) and the University of California, Berkeley.
The Wave Carpet operates submerged, allowing it to survive stormy seas while causing no visual pollution or posing any collision danger. The WaveCarpet has the advantage of being:
Due to the fact that the carpet is fully submerged, it is able to survive the strong momentum of stormy seas.
The device poses no visual pollution to the ocean surface and no collision danger to boats and sea life.
High, broadband and omnidirectional absorption efficiency of ocean waves.
The modular design allows the device to scale in width for setting a desired output power capacity.
Enorasy Labs designed a control system characterized by the Department of Energy as "unique." This control system enables the implementation of a unique turbine, which can generate MegaWatts of electricity with efficiencies that have not been reached before, both in ocean and in land. The control system, called D.A.R.L.E.M., dynamically adjusts the rotational platform of an eccentric mass in multiple degrees of freedom. This real-time "smart" adjustment causes a heavy eccentric mass to rotate at the desired RPM, while it is directly coupled with an electromagnetic generator. The power input for the adjustment is extremely small, as it is provided when the rotating mass, being eccentric, is in a position that requires minimal effort to incline. This is why this unique turbine, which we call Gravity Control Turbine, is extremely efficient.
The ocean wave version of this turbine gyroscopically keeps track of the platform level, which is altered by ocean waves, and in real-time "smartly" adjusts it for optimized results. This frees up the device from the need to predict the upcoming wave characteristics. The mechanism, totally enclosed in a substantially submerged simply moored circular buoy, is also independent from wave directions. DOE: "it has the potential to absorb a significant amount of wave power."
Float Inc. – BergerABAM
San Diego, Calif.
Wave energy absorption is maximized by matching the input impedance of the WEC to the characteristic impedance of the targeted water waves. (The term “Rho-Cee” (ρC) is the formulation of that impedance: water mass density X wave propagation velocity.) The Rho-Cee is the only WEC system that does that – as a matter of explicit design and operational principle. In the ρC, three nested L-shaped oscillating water columns are tuned to resonate over a band of energetic wave frequencies – fitted with float-driven linear electric generators. In an effective “terminator” linear array configuration, no leeward replication, as in a “farm”, is required. Limited model testing (supported by MMS in ‘09-‘10) has shown unprecedented absorption, validating the application of the impedance matching principle to WEC design.
The Rho-Cee WEC structure is made entirely in reinforced concrete, as is its deploying moored Pneumatically Stabilized Platform (PSP). Literally, only concrete is in contact with sea-water in both the Rho-Cee WEC and its PSP, so that with proper formulation and application in construction, neither need suffer corrosion in a 50 year (or more) lifetime. All maintenance-requiring equipment in the ρC WEC is located well above the water line, under cover, fully accessible to personnel on foot.
IOwec (MIT Sea Grant College Program)
The IOWEC (Inertial Ocean Wave Energy Converter) is an all enclosed, monolithic floating WEC secured to the sea floor by a slack mooring line. The kinetic energy of the hull resonant wave induced pitch motion is converted into mechanical energy at the axis of the PTO by a gyroscopic system. All mechanical components are enclosed into internal watertight compartments and protected from sea water. The hull pitch motion induces a variation of the angular momentum of the flywheel thus generating a gyroscopic torque. In its turn, due to precession speed, the gyroscope imparts a damping torque to the hull and extracts the corresponding kinetic energy. The PTO is connected to the precession axis, so it is actuated by the gyroscopic torque and produces electrical energy by means of a permanent magnet electrical generator. The use of Pitch Resonance Tuning Tanks (PRTT) allows tune the resonance frequency of the device, thus increasing the overall efficiency of the system in different over a wide range of sea states. The main advantage of the IOWEC are the long operational life, high reliability and low OPEX: these are achieved by designing the IOWEC hull according low-tech shipbuilding standard and with no submerged moving parts.
M3 Wave's entry into the Wave Energy Prize competition is NEXUS, a mid-column variant of their venerable DMP/APEX submerged pressure differential technology. The system harnesses the pressure wave under ocean swell while stationed above the ocean floor but still safely under the surface, protected from surface hazards. All power, electrical, and mechanical systems are inside protected dry chambers- there are no exposed mechanical joints or sliding seals.
NEXUS turns the pressure fluctuations under ocean waves into alternating expansion and compression cycles of air inside an enclosed pipe. Power is harnessed with a bi-directional air turbine. M3 Wave proved the viability of the underlying conversion technology during pilot testing of their APEX variant in 2014 off the coast of Oregon. NEXUS is positioned higher up the water column, dramatically increasing device power output while preserving the robustness and deployability aspects of APEX.
The Mocean wave energy converter (WEC) is a hinged raft. Wave forcing and the bodies' dynamic responses leads to a motion about the hinge (called flex), which drives a power take-off mechanism that converts the kinetic energy into electricity. It has seven degrees of freedom.
The innovation of the Mocean WEC is in the design of the shapes of the bodies, which dramatically improves its dynamics and thus power absorption. The configurations are based around varying the ratio and position of the water-plane area to the submerged volume, where the water-plane area affects the hydrostatic restoring force and the volume affects the mass and added mass. By changing these values one can induce coupling between the modes and tune the resonant response to improve performance in wavelengths that are significantly longer than the overall length of the machine.
Consequently, although the power take-off is solely in flex around the hinge, there is extensive cross-coupling with other degrees of freedom, and when excited by wave action the device responds not only in flex but substantially in heave and also pitch and surge. This results in greater cancellation of the incoming wave and a broader bandwidth response than a standard hinged raft.
The OE buoy is a deep-water, self-referenced oscillating water column device. The device consists of a long submersed backward-facing duct connected to an air-chamber. Wave forces induce a differential air-pressure in the air-chamber, which gets converted to electricity using a bi-directional air turbine.
The key advantages of this device include: (1) there is only one moving part – the turbine runner – which is out of the water and easily accessible, (2) the air turbine generator combination runs at generation speeds and there are no gearboxes involved making the drive train simple, and (3) being a floating platform it is able to easily shed excessive loads during storm conditions.
The OE Buoy is the result of over 10 years of research and development and has just completed over three years of rigorous testing in Atlantic waters.
Extreme storms and Atlantic waves have confirmed the survivability of the OE Buoy as a power generation platform in the most extreme conditions. This is a testament to the design of the buoy and the simplicity of the functional design as well as the strength of the mooring technology.
Oscilla Power’s Triton™ wave energy converter is a two-body point absorber, consisting of a large surface float connected by flexible tethers to a submerged heave plate. As ocean waves excite the surface float, it reacts against the heave plate, generating tension changes in the tethers. These tension changes are applied to a linear drivetrain, consisting of a hydrostatic load amplification system and a variable reluctance generator that translates the low displacement, high force mechanical energy input into electrical energy in a simple, highly reliable manner that is unachievable in the ocean environment with conventional generators. Triton’s advantages over conventional point absorbers include greater energy production, lower capital costs and lower maintenance costs.
Principle Power is humbled and excited to be a part of the DOE's Wave Energy Prize to develop affordable, clean energy technologies.
RTI Wave Power
The RTI F2/F2D Wave Energy Converter (WEC) development objective is the lowest Capital Cost per Megawatt of output combined with secure survivability in severe seas. WECs must weigh less to cost less. Intercepting maximum energy containing wave front per unit WEC vessel volume, which like ship volume, determines WEC weight and cost. This is only realizable with WECs utilizing single or adjacent multiple Elongated Wave Front Parallel (EWFP) floats.
To concurrently capture a majority of both heave and surge energy the RTI F2/F2D utilizes elongated swing arms to attach its EWFP float directly to a generator in its motion stabilized floating twin vertical spar frame which constrains the float to move concurrently upward (for heave capture) and rearward (for surge capture) on wave crests and return forward and downward on subsequent wave troughs. The F2/F2D WEC utilizes RTI’s floodable and submergible floats and seawater ballasted frame to place its EWFP float safely below severe sea wave troughs.
The RTI F2/F2D is covered under US Patents 9,127,640, 8,614,520, U.S. Published Application 2015/0082785 and pending U.S. and International Applications.
The DUO wave energy converter is a new design concept that simultaneously captures power from both the heave and the pitch/surge motions induced by wave action.
The additional modes of power capture have the potential for increased efficiency in terms of energy capture per unit cost compared to devices operating in a single mode or single direction.
The DUO’s patented configuration, which connects oscillating bodies with angled pre-tensioned cable linkages and a Power Take Off system, enables power capture from pitch motions to be exploited simultaneously with heave motions. The DUO’s primary power absorption is achieved by damping the relative heave and rotational motions of the oscillating structures.
This produces a significant increase in power capture (and energy production) compared to devices that capture power from a single mode of motion.
The increased power capture and the associated engineering innovations can produce major reductions to the costs of generating electricity from wave energy resources.
Redwood City, Calif.
SEWEC is an oscillating water column (OWC) wave energy converter -- a device that operates in a similar fashion to the most successful shore based wave energy convertors, such as the Limpet (https://en.wikipedia.org/wiki/Islay_LIMPET).
The difference is that SEWEC is free-floating and specially adapted to withstand the more challenging offshore, deep water environment where available energy levels are higher and more widespread than those available nearshore.
The SEWEC device extends the proven OWC concept, enabling devices to be moored offshore in a much wider range of locations than conventional shore-based devices. Unlike shore-based OWC’s, only minimal site work is required to set up a SEWEC wave energy farm – the devices are simply towed out to their moorings.
The Wave Energy Prize targets offshore wave energy capture and uses conversion efficiency and capital cost as key metrics to compare the competing entries. SEWEC scores well on both counts – its simplicity and robustness result in low capital costs and the highly efficient OWC principle delivers great conversion efficiency.
Only large-scale deployment of low-cost, robust and efficient devices can fully exploit the huge and as yet largely untapped renewable energy resource surging in the world’s oceans. So Team SEWEC is eagerly participating in the WEP competition -- a great way to identify the really serious contenders.
Super Watt Wave Catcher Barge Team
Super Watt Wave Catcher Barges take full advantage of economies of scale and use proven low-cost components. They use an ocean going barge to catch as much vertical wave pressure as possible with one structure, one mooring system and one export power cable. They are moored vertically and horizontally. Their vertical mooring legs turn large diameter uni-directional pulleys that "store torque" in large recoil springs located inside large diameter flywheels. These flywheel / recoil spring combinations uniformly unload their "stored torque" to four low torque, low RPM, high output direct drive wind turbine generators located onboard. The generators take advantage of sea water cooling for further cost, space and weight reduction. The power can be converted onboard or delivered directly to a Lazy S export power cable connected to a local power hub for further power farm conversion. The vertical mooring system loads are reduced automatically to a maintenance top tension during storms and the barge rides out the storms on its horizontal mooring system. After the storms pass, the vertical mooring system is reengaged and the power generation, of up to 4 x 6 megawatts of power, is resumed. CAPEX an OPEX are similar to onshore wind power.
Team FLAPPER (Floating Lever and Piston Power ExtractoR)
Research Triangle Park, N.C.
Wavefront Power's Very Large Flapper Array (VLFA) is being developed for utility-scale power production from deepwater ocean swell waves. The design will introduce a number of innovative, patent-pending technologies that will enable for the first time the economic capture of deepwater wave power. Operating at depths up to 100 meters, the device is expected to be rated at approximately 5 MW with a capacity factor of 48% based on an annualized average wave density of 30 kilowatts per meter.
The VLFA generally falls into the oscillating wave surge converter category of wave energy collection devices. While intellectual property concerns prevent us from disclosing many of the VLFA's internal mechanisms, general operation is characterized by a conversion of the kinetic energy of wave swells into electrical energy through a power conversion chain including a hydraulic power take-off, hydraulic motor and electrical alternator.
Wave Energy Conversion Corporation of America (WECCA)
North Bethesda, Md.
Wave Energy Conversion Corporation of America (WECCA) has developed its patent-pending Advanced Wave Energy Conversion System (AWECS), which physically presents as three articulating barges, securely anchored off shore, which survived nine years of WEC platform concept testing off the west coast of Ireland. The fore and aft barges are propelled by continuous, undulating, emission free, ocean waves surrounding the world's continents. Power Take Off devices are connected at leveraged hinge points to the center barge via robust hinges. The relative motions of the fore and aft barges, compared to the "weight dampened center barge", provide opportunity to cost effectively capture and transform ocean wave energy into electricity. AWECS electricity is then "conditioned" for local grid requirements.
The AWECS is constructed from lightweight, durable composite material providing strength, maintenance advantages and long term environmental cost benefits to operators and consumers. Designed to constantly sense and dynamically tune its physical characteristics, the system is able to extract the maximum energy through resonance relative to changing wave climates. When hazardous storm conditions are sensed, the AWECS is designed to submerge and hover at safe depths, until storm conditions subside, then surface again to generate electricity.
The Archimedes Waveswing™ is a submerged point-absorber wave energy converter which uses the change in pressure caused by passing waves to expand and contract a large piston. The piston houses a linear generator which converts the relative motion of the two parts directly into electricity. The unique operating principle of the device provides a gearing effect resulting in amplification of the effective wave height, thus producing a highly effective point absorber. The device is tension-tethered to the sea bed anchor via a structural leg which also carries a flexible power cable for export of electricity ashore.
The device was originally invented by Fred Gardner in Holland in 1994 and a previous variant was tested offshore Portugal at large scale. The recent innovations have enabled down-scaling of the device, thus improving the energy yield per unit volume and hence reducing the cost of power produced. Initial systems will be rated at 50kW and designed to meet power needs in isolated situations and island communities where the cost of alternatives is high. The technology is expected to progress to utility scale as learning is gathered through early deployments. The current design although novel, is based on many years of experience.
The content & opinions in this article are the author’s and do not necessarily represent the views of AltEnergyMag
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