Wave-Powered Energy Conversion System
A wave-powered device having enhanced motion. The device including first, second, and third barges, with the second barge having a first reservoir and a second reservoir. The first and second reservoirs being coupled by a first passageway to permit a first fluid to selectively and passively move between the first and second reservoirs in a predetermined manner to increase the pitching moment of the second barge while the second barge pitches while floating over waves. A first coupling mechanism is coupled between the first and second barges to enable the first and second barges to move relative to one another, and a second coupling mechanism is coupled between the second and third barges to enable the second and third barges to move relative to one another.
This application claims the benefit of provisional U.S. Patent Application Ser. No. 60/740,674, entitled “Wave-Powered Energy Conversion System,” filed Nov. 30, 2005, which is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION1. Field of the Invention
The utilization of ocean wave energy has been the goal of many for more than a century. There are primarily two products of wave energy conversion, those being electricity and potable water. Because electricity production is more “exciting” to humankind, most of the efforts in wave energy conversion have been focused on electricity. For those of us more interested in the benefit to humankind, potable water is more desirable. To realize this fact, the reader should answer the following two questions: (a) How long can I survive without electricity? (b) How long can I survive without water?
2. Description of Related Art
Of all of the wave energy techniques, the most apropos for water production, in the opinion of this writer, is the articulated barge system. There are two versions of this technique. The first is the Hagen-Cockerell raft and second is the McCabe Wave Pump. These are disclosed in U.S. Pat. Nos. RE 31,111 to Hagen; 4,210,821 to Cockerell; and 5,132,550 to McCabe, each of which is incorporated by reference thereto. The former is simply a system of freely-floating hinged rafts having pumps located over the hinges. The latter is a three-barge system having a horizontal damping plate suspended below the center barge. It has been found that the McCabe concept is more efficient than the Hagen-Cockerell raft system, which is a wave-following system. Because of its low efficiency, the Hagen-Cockerell raft system was never developed; while, the McCabe Wave Pump is now in the development stage.
BRIEF SUMMARY OF THE INVENTIONDescribed herein is a passive technique for improving the efficiency of a wave-following, articulated raft wave-energy system. The motion-enhanced system is promising for the production of potable water for coastal communities and island communities.
One aspect of the application relates to a wave-powered device, including a first barge; a second barge having a first reservoir and a second reservoir, the first and second reservoirs being coupled by a first passageway to permit a first fluid to selectively and passively move between the first and second reservoirs in a predetermined manner to increase the pitching moment of the second barge while the second barge pitches while floating over waves; a third barge; a first coupling mechanism coupled between the first and second barges to enable the first and second barges to move relative to one another; and a second coupling mechanism coupled between the second and third barges to enable the second and third barges to move relative to one another.
The Articulate Barge Wave-Energy Conversion System
A computer-generated picture of an articulated barge system is shown in
Barges excite the pumps 16 located over the hinges. These pumps 16 are preferably hydraulic pumps designed to draw in salt water, pre-filter the water and pump the water at high pressure to a reverse-osmosis (RO) desalination plant. Depending on the application and product water (potable water) requirements of the system, the RO can be on shore or on the deck of the after barge 18 of the system.
The center barge 14 preferably has a length that is less than half of the forward barge 10 length, by design. This ensures that the relative angular displacements of each barge will be relatively large.
The after barge 18 is preferably the longest of the three for two reasons. First, since it receives about 40% of the incident wave power, it needs to be longer to capture that power. Second, a longer after barge 18 provides a certain amount of directional stability to the system. That is, it helps the system face into the direction of the incident waves.
Motion Enhancement
There are two types of motion enhancement of the system sketched in
A. Center-Barge U-Tube
In
It is known that U-tubes 24 have natural periods of oscillation. That period, without any damping in the system, is T=2π√ (l/2 g), where l is the linear distance from the center of the air-water interface in the center of one reservoir to the same point in the other reservoir. This frequency should be avoided. To do this, both hydraulic and pneumatic valves are used to increase the flow resistance. This changes the period and causes the transfer of water between the reservoirs to be orderly.
The volume of fresh water within the hydraulic system is determined from both performance predictions in a design sea, and the ballast requirements of the system. For performance, the reservoirs should be separated by a relatively large transfer pipe 24 in order to produce a high pitching moment. The weight of the water 22 acts as ballast, and will help determine the operating draft of the system.
B. Forward-Barge and After-Barge U-Tubes
For optimal performance, there are two considerations: First, the forward 10 and after 18 barges should be in resonance with the incident waves. Pitching about the hinges 12 attaching the barge-pairs (forward-and-center and center-and-after) is the production motion of system. The natural pitching period of each barge 10, 14, 18 depends on the ballast and the location of the center of gravity. The U-Tube technique can be used to tune the pitching motions of the barges 10, 14, 18 to the design wave period. Referring to
The second optimization concerns the relationship between the total length (L) of the system in
We may choose the smaller of the length ratios: so, for the 7-second wave, the ideal length is 125 feet. For this length, the displaced system as the crest of a design wave passes would resemble that in
C. Off-the-Shelf Design
For L/λ=0.5, a system can be constructed using the Flexifloat 110, 114, 118 barges or some other commercially available barges. Using the Series S-70 Flexifloat 110, 114, 118 barges to illustrate the system is shown in
a. S-70 End Rake, 10 feet in length, displacing 5.25 tons, coupled to a
b. S-70 Quadrafloat, 40 feet in length, displacing 17.80 tons
c. S-70 DuoFloat, 20 feet in length, displacing 9.45 tons
d. S-70 Quadrafloat, 40 feet in length, displacing 17.80 tons, coupled to a
e. S-70 DuoFloat, 29 feet in length, displacing 9.45 tons
The pumps are preferably salt-water pumps of special design. These are located 4 feet above the hinges.
While the invention has been described with reference to the certain illustrated embodiments, the words which have been used herein are words of description, rather than words or limitation. Changes may be made, within the purview of the appended claims, without departing from the scope and spirit of the invention in its aspects. Although the invention has been described herein with reference to particular structures, acts, and materials, the invention is not to be limited to the particulars disclosed, but rather extends to all equivalent structures, acts, and materials, such as are within the scope of the appended claims.
Claims
1. A wave-powered devices comprising:
- a first barge;
- a second barge having a first reservoir and a second reservoir, said first and second reservoirs being coupled by a first passageway to permit a first fluid to selectively and passively move between said first and second reservoirs in a predetermined manner to increase the pitching moment of said second barge while said second barge pitches while floating over waves;
- a third barge;
- a first coupling mechanism coupled between said first and second barges to enable the first and second barges to move relative to one another; and
- a second coupling mechanism coupled between said second and third barges to enable the second and third barges to move relative to one another.
2. A device according to claim 1, wherein
- said second barge includes a second passageway between said first and second reservoirs for a second fluid to enter said first and second reservoirs.
3. A device according to claim 2, wherein
- said first fluid is water and said second fluid is a gas.
4. A device according to claim 1, wherein
- each of said first and second coupling mechanisms includes a hinge.
Type: Application
Filed: Nov 30, 2006
Publication Date: Apr 2, 2009
Applicant: Ocean Energy Systems LLC (Glen Burnie, MD)
Inventor: Michael E. McCormick (Annapolis, MD)
Application Number: 12/095,200