By Others

The gestic motion of ocean waves is long considered substantive kinetic resource. Estimates indicate world energy demand would be satisfied if less than 0.02% of renewable ocean energies are converted to electricity. Possible mechanisms include surface following buoy arrays that use linkage between respective floats and fixed objects to produce mechanical power, connected to a generator or transferred to a working fluid, water, or air pressure, that drive a turbine generator. I.L. Roberts' 1881 patent (image upper left) is of a modular, buoy-based wave power machine. If then developed during a most naturally moderated world climate, perhaps hydrocarbon, nuclear, and related process waste mismanagement would now be considered non-conventional energy. In haste to a quick fix, plethora of seemingly divergent equipment has been proposed, or slightly developed, for converting the large amounts of mechanical energy, present in water waves, to electrical energy. Small scale offshore devices have been ocean tested and activity is increased since the 1992 Earth Summit identified carbon dioxide emission reduction as central objective against climate change. Yet exploitation is only slowly evolving from early stages of technical development. Despite wide variety of proposed wave power technologies, extensive utilization of practical configurations is partly restrained by designs of limited material efficacy that provide blurry vision of required technological response. Within considerable range of apparently differing technique are inferred general classification of well understood approaches. The art field is now expanding to copious extent so to seemingly dilute improvement rate from among core precedent. As with many current products comprising increased technoplexity of theretofore well-adapted apparatus, contributions by Roberts, and others, are largely forgotten or purposely ignored. Incrementally diminished concept variation forms infringing identity of construct, trademark, and particular confusion to those becoming interested in the art. Several entities quite exactly reproduce LEG linear electrical generator elements invented April 1978, disclosed in 1980 U.S. Patent 4,232,230 to Ames, and tank tested 1982. Still others pursue power conversion aspects of U.S. Patent 4,672,222 to Ames.

Though signs of Roberts’ 1881 invention remain discernable through the noise, extremely few systematic techniques have been achieved. Instead, the field is replete with designs of usually disproportionate, complex, unitary, or lineal style that off-scale end use functions and do not efficiently avail planar expanses of multi-directionally fluctuative energy comprising the wave environment. Majority prior and current approaches comprise fundamentally permanent wave conversion installations positioned on shorelines, breakwaters, or in shallow water. While power of breaking waves is visually prominent along coastlines that seem obvious installation locale for several proposals, such phenomena are actually in shape change perturbation, losing energy to increasing bottom friction, and confused exhaustion upon shore. With relatively high ancillary cost, fixedly structured surge channels are necessarily durable to withstand slamming and storm damage. Such land-bound or onshore structure proportions are unavoidably off-scale with normal wave activity and readily may generate functionally disrupting reflected waves. Often, land uses impose operational, environmental, or social constraint from scenic degradation. Shorelines and littoral edges or margins are most delicately enriched with pre-existent natural process and life of intertwined biodiversity continually identified for designation as Marine Protected Areas. Many zones are, or nearly, compromised from persistent landward encroachment and would completely devastate from major seaside envelopments. Oceandustrial imposition, to any extent, intrinsically impacts surroundings. The technological approach must be minimum systems imprint carefully and quietly adapted considerable distance from influencing organic communities or as peripheral barriers to navigation about previously damaged areas. In very special-case environs having suitable site conditions, perhaps removable non-contacting skeletal planar structures may be prudently assimilated at or near hydroface to cast shade that helps restore sick reef habitats or intrinsically foster marine growth in dead zones. Notably, use of magnetic materials and distributed electrical transmission requires environmental shielding. Discrete anchored systems may provide hanging sensors in various strata for monitoring such activity with only marginal disruption to seafloor-disposed bioforms.

Extensive commercial utilization is partly restrained by device practical limitations for maximal potential use of available resources and materials. Commonly, wave energy converters are designed with absence of neutrally stabilized unit modularity by which self-supported modules are similarly interconnected with other of an array for expansion or reduction to any desired quantity. Powerful but diffuse wave nature requires a significant number of devices to generate industrial scale electricity. Conglomerate investment in singular, or quantity single point-of-use, devices divert application from direct energy extraction of multipoint generated multidirectional waves at the times they locally promulgate and subside. Frugal industrial interface with such medium would suggest that, if a “large bucket of money were thrown” at the kinetic opportunity, technology imprint must also be of diffuse nature- dominantly horizontal planarly distributed and openly spread, point-to-point, in melding correlation with hydroface. This quality is vital for matching the electrical product to changing end use demands.

Representative examples of oversized devices are intended for "concentration" of wave energy into a tapered area before conversion. These focusing surge devices are sizable barriers that channel large waves to increase wave height for redirection into elevated reservoirs. The water then passes through hydroelectric turbines on the way back to sea level thus generating electricity. Land or breakwater grid-connected wave power systems include a 350 kW Norwegian Tapered Channel plant and an Indian 150 kW oscillating water column. Japanese plants of 20, 30, 60 kW, and a 75 kW Scottish project put estimates of existing worldwide capacity at about 700 kW. The durability of the Norwegian design led to two commercial 1.5 megawatt power plants in Java, Indonesia and King Island located near Tasmania. Environmental objection to continuous arrays of onshore or shore based wave-energy devices are founded upon the physical alteration of coastlines. These array types may present hazards to shipping, affect marine ecology, and result in coastal erosion where the waves are concentrated and more sedimentation in adjacent areas. During severe storms, energy transmitted by breaking waves may be over 10 times average conditions and coastal wave energy plants must be built to withstand these forces. Thus, while focusing devices are less susceptible to storm damage, massive structuring renders them most costly among wave power plant types.

Proposals for pneumatic wave energy converters (PWEC) or anchored oscillating water column mechanisms (OWC) utilize pressure changes of above hydroface, closed-chamber air columns for driving turbines and generators. The simplest examples are navigational buoys where waves entering the anchored buoy compress air in a vertical pipe. The compressed air is used to blow a whistle or drive a turbine generator producing electricity for light. Since 1965, Japan has installed hundreds of OWC-powered navigational buoys and is currently operating two small demonstration OWC power plants. China constructed a 3 kW OWC having an artificial gully and a Wells turbine. India has a 150 kW OWC caisson breakwater device with Wells turbine. PWECs receive much attention by inventors and in international cooperative efforts such as "Kaimei", a large, multi-chamber experimental barge. It was shown that power extraction was maximal at the resonant period of the air-water column and not at the natural period of heaving. In monochromatic seas, turbine stators were manually adjusted for "tuning" impedance of conversion means to the resonant period but satisfactory automatic "tuning" was not achieved. Though results were made with "Kaimei", partially due to its overall size in excess of multiple wavelengths, concepts for autonomous versions of PWEC seem plagued with a further problem whereby chamber means develop self-heaving and irregularities of wave form and period that usually negate "tuning". The resulting oscillation of the chamber and wave group is often cophasal. This effect severely curtails air pressure flow through the turbine and subsequent power extraction. Taut mooring may be employed to limit chamber movement but this condition causes undesirable submergence of operative components in swell conditions and suffers the above mentioned deployment limitations. Furthermore, omnidirectional deployment of the device covers and dampens the source of energy from which it operates.

Other products use submerged shoreline turbine generators, near shore anchored wave stations, and near shore combined wave and wind stations. Typical hybrid assemblies essentially share available force and are most conspicuous in single or spaced apart “multiple single” point-of-use applications. Representative pneumatic or hydroelectric fabrications normally have generally tapered cowling means intended for redirecting and concentrating predominately unidirectional wave surge toward turbine focus. Or, a heaving air column in a captive chamber is vented through turbines and power take-off.Such designs typically necessitate high maintenance, costly, taut moorings or foundations per unit for operation while only using the extreme upper strata of an ocean site for energy conversion. Additionally, taut mooring deployment is limited to primarily onshore locations.

Another typical configuration is defined by an elongated housing, mounted on columns above a body of water, having several suspended driveshafts with buoys. Driveshafts are series-connected to a common output shaft. This mechanical unification of disparately operative point absorbers centralizes energy conversion means that must be responsive to extensively variable forces ranging from slight movement of a single buoy to substantial movement of all buoys. Conversion means are necessarily constructed to accommodate maximal forces and, thus, are less efficient when other conditions prevail. Additional concepts incorporate dense mass associated with buoyancy means for equalizing power take-off from buoyancy in the upward direction and gravity in the downward direction. Rather than improving electrical generation efficiency, such buoy associated mass impedes upward buoy movement after submergence. Conversely, downward forces of additional mass are partially negated by buoy lift. Resultantly, reciprocation frequency is substantially lower than wave frequency thus causing partial cessation and slower output speeds during normal operation. This device also suffers source dampening.

A Wave Energy Module (WEM) implements two parallel platforms connected by six hydraulic pumps with check valves. One platform, a raft, floats on the hydroface and the other, a reaction plate, is suspended below the hydroface for dampening. The structure also incorporates elastic suspension cords. As the raft rises relative to the reaction plate, the pumps force fluid through end ports to charge a high-pressure accumulator. A low-pressure accumulator forces fluid back into the pumps when the raft lowers. While a measurable improvement over other platform devices, such as the Cockerell Wave Contouring Raft, the apparatus remains scale sensitive. For example, if the impinging wave profile is low amplitude/high frequency or high amplitude/low frequency, the entire structure is raised and lowered quite evenly thus maintaining a parallel relation with little relative movement between the platforms. Tensioning of elastic cords would divert otherwise useful wave energy. Implementation of hydraulic fluids adds an unnecessary step to the conversion process. Furthermore, this device is not readily associative with other similar units and thus is not a module.

The Salter Duck comprises a longitudinal series of floating vessels pivoting about a common shaft that drives hydraulic fluid to produce electricity. Vessels are shaped as coformed circular and triangular sectional vanes. A Duck variant was used as a unidirectional wavemaker in a demonstration film. The appearance of 80% incoming wave energy capture is depicted when the film was run backward. Deployment of several units requires sufficient non-interference spacing. The configuration causes detrimental forces on hinging mechanisms with less than optimal orientation over more realistic seascapes.

Demi-Tek Inc., West Caldwell NJ, proposed a "Monitor" hybrid tide, wave, and wind electrical generation system in the ocean off Asbury Park. The invention is in service, August 1999, generating enough energy to light the boardwalk and Convention Hall. The lab tested Monitor is designed to reduce wave action on severely eroded beaches along the coast. The 12' x 20' x 40' system is secured, by catapult-type cables that expand or retract with ocean currents. The cables attach to 30-foot anchors screwed into the ocean floor, as used on large oil rigs today. Each anchor carries 140,000 pound load and six anchors are estimated as sufficient to withstand a major storm. Monitor water is guided so that it flows in one direction to spin blades that produce electricity. The electricity is then transferred to shore through a cable buried in the sand. One such device is reported to generate one megawatt.

Ocean Power Technologies, Princeton, NJ, has developed a "hydropiezoelectric" generator consisting of a slender panel tethered between a float and anchor. Panel models are 50’ long, 1’ wide, about 1’ thick, and consist of 50 to 100 thin sheets of a polyvinylidene fluoride trifluoroethylene copolymer. Electricity is generated from applied pressure as this piezoelectric material is stretched and released by rising and falling buoys. The inventors claim that an array of generators covering five square kilometers could supply electricity for 250,000 people at a cost of one to three cents per kWh. This compares with about five cents for electricity produced from state-of-the-art combined cycle gas plants and eight or more cents for oil-fired stations. "It's a very new concept. It's a feasible technology but it's a matter of cost at the end of the day. It seems an incredibly low figure. Even the most favorable cost estimate from current wave power technology is five to eight cents per kWh. When an early proposal has such low figures, one tends to be skeptical," said Tony Lewis, of Ireland's University of Cork, who also advises the European Commission on wave power. Japan's Penta-Ocean Construction Company Ltd. has contributed an undisclosed sum to fund the construction of a 1-kilowatt (kW) prototype in the Gulf of Mexico. While the proposed geometry draws many questions and suffers from usual taut mooring problems, the material may be practically used for OWEC® damper plates and bellows or sleeves, as further described. OWECO suggests material evaluation of this "crackling carpet" for efficient sea anchorage while synergetically generating electricity on selected modules.

Larry Bergren wave tank tested a wave energy device consisting of a floating buoy and a submerged plate. Both buoy and plate are vertical, straight, circular cylinders of equal radius connected to a power take-off mechanism. The mechanism breaking force is controlled to enable various mathematical models to be tested. Hydrodynamic properties of wave induced forces are calculated keeping the buoy and the plate fixed. Added mass and damping interactions are calculated separately for the two bodies by oscillating one of the bodies and keeping the other one fixed. The hydrodynamic properties are solved by the method of matched eigenfunction expansion. The model allows non-linear phenomena to be included in the time domain. Examples of such phenomena may be irregular waves, non-linear power take-off mechanisms and non-linear drag forces.

Of note, United States Patent 5,186,822 issued Feb. 16, 1993 to Tzong, et al referenced OWEC® U.S. Pat. 4,672,222 to Ames despite substantial technical difference. This wave powered desalination apparatus includes turbine-driven pressure responsive desalination means, a storage tank and conduit connecting to a pump mounted in a resonant chamber caisson having an opening in one side for receiving the incoming ocean waves. The caisson is configured in accordance with the natural frequency of the incoming waves and amplifies waves to drive a float coupled with the pump. Actuation of such pump pressurizes the storage tank to drive brine through desalination means for separating potable water. The apparatus includes a turbine generator arranged to facilitate pressurizing of the brine.

Cited devices indicate hestoric trends and do not exhaust the myriad of permutations in the field of wave energy conversion techniques elucidated in US Patent Class 60, sub-classes 495-507, Class 290/42-44, 52-54, 60, Class 417/330-334, International Patent Class F03B 13/12, former Classes 290/42-53, ongoing patent, literature, and internet searches of wave concentrators, pneumatic, self tuning, parallel platform types, or the above-generally described permutations.