Wave Energy Converter Patent

8/8/2019 Wave Energy Converter Patent

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Drawings in which:

-..;;/FIG. 1 is a perspective view of a wave catcher wave energy conversion device;

-..;;/FIG. 2 is a perspective view of a divided container;

-..;;/FIG. 3 is a perspective view of a float, a fin, and a rudder;

-..;;/FIG. 4 is a perspective view of a power take off system;

-..;;/FIG. 5 is a perspective view of a drive housing;

-..;;/FIG. 6 is a functional block diagram of a wave crest approaching a wave energy

conversion device;

-..;;/FIG. 7 is a functional block diagram of a wave crest receding from a wave energy

conversion device;

-..;;/FIG. 8 is a functional block diagram of a wave trough approaching a wave energy

conversion device;

-..;;/FIG. is a functional block diagram of a wave crest receding from a wave energy

conversion device;

-..;;/FIG. is a functional block diagram of a high velocity wave approaching a wave energy

conversion device;

-..;;/FIG. 11 is a ;

-..;;/FIG. 12 is a;

-..;;/FIG. 13 is a;

-..;;/FIG. 14 is a;

-..;;/FIG. 15 is a;


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-..;;/FIG. 16 is a;

-..;;/FIG. 17 is a;

-..;;/FIG. 18 is a;

-..;;/FIG. 19 is a; and

-..;;/FIG. 20 is a.

-..;;/031503661540

BRIEF DESCRIPTION OF THE DRAWINGS - REFERENCE NUMERALS

-..;;/4..wave energy conversion device

DETAILED DESCRIPTION FIRST EMBODIMENT here you should describe in great

detail the static physical structure of the first embodiment of your invention (not how it

operates or what its function is).

-..;;/Referring now to the drawings, wherein like reference numbers are used to designate

like elements throughout the various views, several embodiments of the present invention are

further described. The figures are not necessarily drawn to scale, and in some instances the

drawings have been exaggerated or simplified for illustrative purposes only. One of ordinary

skill in the art will appreciate the many possible applications and variations of the present

invention based on the following examples of possible embodiments of the present invention.

-..;;/With reference to FIG. 1, a wave energy conversion device 100 in accordance with the

preferred embodiment is shown and is collectively referred to as a wave catcher. The wave

energy conversion device 100 includes a differential wave energy conversion system 200, a

wave motion differential wave energy conversion system 300, a power take off system 400,

and a propulsion system 500. A frame 101 supports all of the systems. A float 102 maintains

the wave energy conversion device 100 at the desired level. A fin 103 and a rudder 104

maintain the wave catchers orientation.

-..;;/With reference to FIG. 2, a wave motion differential wave energy conversion system

200 is shown. The wave motion differential wave energy conversion system 200 has a

number of wave amplifiers; three front wave amplifiers 201,202, and 203, and three back


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wave amplifiers and 204, 205, and 206. Two of the front wave amplifiers 201 and 203 merge

as do the two of the back wave amplifiers 204 and 206. The merged amplifiers connect to the

front and back of a louvered container 207. Inside louvered container 207 is a vertical turbine

wheel 208 rotating on a freewheel 209. The freewheel 209 engages with a axle 208 . Wave

pressure differentials between the front and back of the louvered container 205 opens a pair

of louvers 209 and 211 or a louvers pair 210 and 212. The front inward opening louvers 209

opens on the right side of the louvered container 205 and the back outward opening louvers

211 also opens on the right side of the louvered container 205 if the wave pressure

differential is greater on the front side than the pressure on the back side. The back inward

opening louvers 210 opens on the left side of the louvered container 205 and the back

outward opening louvers 211 also opens on the left side of the louvered container 205 if the

wave pressure differential is greater on the back side than the pressure on the front side. The

louver pair 209 and 211 opening permit water to flow from the front to the back of the

louvered container 205 and the water flow forces the vertical turbine wheel 206 to rotate

counter clockwise. Also, the louver pair 210 and 212 opening permit water to flow from the

back to the front of the louvered container 205 and the water flow forces the vertical turbine

wheel 206 to rotate counter clockwise. The vertical turbine wheels 206 rotation engages the

freewheel 207 and rotates the axle 208. The axle 208 is connected to a transmission 213

containing gears that increases the low speed axle 208 rotation to rotate a flywheel 214 at

high speed. The flywheel 214 is attached to a clutch 215 and the clutch 215 can be engaged

with a generator shaft 216 to produce electricity.

-..;;/With reference to FIG. 3, a differential pressure wave energy conversion system 300 is

shown. A front wavelength tunable cavity 301 and rear wavelength tunable cavity 302

-..;;/With reference to FIG. 4, a focused wave impulse wave energy conversion system 400

is shown.

-..;;/With reference to FIG. 5, system 500 is shown.

DETAILED DESCRIPTION OPERATION FIRST EMBODIMENT


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levels to extract energy from9

power take off system judged on the following aspects: component complexity survivability, the costof building and maintenance, the amount of secondary losses, and feasibility of designing

and manufacturing of the system

DETAILED DESCRIPTION ALTERNATIVE EMBODIMENTFIGS.

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Z!160Z66er between the primary interface and the PTO (2), giving

the captured power ._ Stage three: is the _ow of power between the PTO and the _nal stage of power conversion(3), giving the delivered power.

During these three stages of power transfer, the WEC must also perform the powerconditioning tasks described by Salter et al [32], namely:_ Gearing: conversion of wave induced motion, characterised by low velocities and high


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forces, to motion with high velocities and low forces, as is required for electricitygeneration_ Recti_cation: conversion of bi-directional motion into uni-directional motion._ Limitation: restraints on forces that exceed design limits._ Storage: conversion of a random or cyclical _ow of power into a smoother power output.

Each individual interface may move with six degrees of freedom: three rotational (pitch, roll,yaw) and three translational (heave, surge, sway).

The PTO captures a portion of the intercepted power. This captured power may betransferred to the next stage by any suitable intermediate energy carrier. Energy carriers thatare currently in common use are electricity and hydraulic

The second stage captures power by opposing the relative motion of the primary interfaceand a reference point. This reference point may be classi_ed as: Referenced: to aneighbouring body (either horizontally or vertically adjacent) thatexperiences a different exciting force.

Moorings are broadly classi_ed into three groups,according to their opposition to motion in the direction of the PTO force:_ Rigid: a solid connection to ground (the sea bed), for example a cassion with a foundationon the seabed, a _xed tower mooring, or an articulated loading column [38]._ Tight: an elastic but stiff connection to ground, for example taut spread mooring._ Slack: station-keeping, negligible opposition to displacement in the direction ofPTO, highly non-linear spring to oppose non-linear second-order forces, for examplemulti-catenary mooring.

The captured power is usually not in a form convenient for transmission or consumption. Itmay require a change of energy carrier, or it may require conditioning (gearing, recti_cation,storage, limitation as described in x 2.2.3) so that it _ts the standards of the form of thedeliveredpower.

In a WEC, the power conditioning functions of gearing, recti_cation, storage and limitation(x 2.2.3) may take place in any or all of the three stages of power - direct drive and buffereddrive


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In a buffered system, the power is captured in the second stage and is transferred to amediumthat is easy to store. At present the preferred medium is pressurised _uid. Storage ofhydraulicoil in paired high and low pressure accumulators is favoured by many device developers,while

others are considering pumping water to onshore reservoirs


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Accumulators are energy storage de

accumulators of adequate size andimportant functions. First, they stor

loads. Second, they keep the systemthan hose should be used between t

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Examples of geometry control include:_ Aligning a directional device with respect to the principal wave direction, which changes

the excitation coef_cient._ Altering mechanical mass or spring coef_cients (often referred to as `slow tuning'),which changes terms in the intrinsic impedance that are not due to radiation._ changing the con_guration of structural members relative to each other or the watersurface, which affects both excitation coef_cient and intrinsic impedance_ Changing the degrees of freedom of motion with respect to each other or the watersurface, which affects both excitation coef_cient and intrinsic impedance.Geometry control works best when used in conjunction with PTO force control.PTO force control determines the amount of power returned to the sea during the secondstageof the power conversion chain. The amount of power returned to the sea also depends uponthe intrinsic impedance, which is why geometry control works better when PTO force is alsocontrolled.

Control of the third stage refers to regulation of the quality and quantity of the deliveredelectricity. Load shedding, voltage control or power factor control may be applied at thisstage.In a buffered system, power conditioning may include storage management. In a direct drivesystem, power conditioning may include power smoothing (storage), and control offrequency,harmonic content, and voltage.


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=B

The PTO regimes considered here are those that can be used to describe the operationin different types of sea states:_ Capture no power._ Maximise generation of power._ Maximise generation of power given constraints and limitations._ Capture a set level of power.

When the goal is to maximise power generation, the conventional approach of feeding backthe error to minimise the difference between the set-point and the output has an extra levelofcomplexity. The difference between the power maximisation and the amplitude limitationregimes is notstraight-forward. There are many strategies for determining the set-point for power in themaximum andlimitation regimes.

When the sea state contains insuf_cient energy then no power will be generated. If a seastateis very energetic it may be necessary to stop capturing power and to put into placeproceduresto limit the risk of storm damage.

In wave energy literature, the most common usage of the term controldoes not mean controlin the classical sense at all, and is strictly an optimisationproblem. It is typically used tomeanthe optimisation of the PTO settings, which corresponds to the second stage in the controlclassi_cation by power _ow. The most common usage also refers to a control regime thataims to maximise energy capture. This is optimisation rather than control because there arenoset-points: the desired system state is to capture as much energy as possible, but it is notknownhow much is actually possible. There are however various ways of choosing the PTO

settingsthat optimise the system, and these methods are the focus of much of this thesis.

The upper bound of this capture width [56] is determined by the modes of motion.Intriguingly, the upper bound of capture width is not affected by the scale of the WEC, so apoint absorber has the same upper bound as a scaled up version of itself. This means that,in theory at least, a small WEC (a point absorber) could absorb as much power as a largeWEC

For a WEC, the total force f can be expanded to give:fe floss fr fs fpto = ma (3.23)wherefe is the wave excitation force

floss is the net force due to energy lossesfr is the force due to radiation of wavesfs is the net restoring (spring) force, which includes the effects of gravityfpto is the external force provided by the PTO system

As described by the Archimedes principle, a _uid exerts a buoyancy force equal to theweight ofthe displaced _uid. At equilibrium, the weight of the body, mg, is balanced by the weight ofthe


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displaced _uid, _gv, where v is the submerged volume, _ the water density, and ggravitationalacceleration. The net force on the body is the resultant of these two forces:fb = mg _gv

Mechanical spring includes any means of opposing displacement apart from buoyancy andthePTO force. A mechanical spring that reacts against the same reaction point as the PTOsystem isnot the same as PTO spring. The mechanical spring term forms part of the intrinsicimpedanceof the WEC, rather than part of its PTO impedance.

The control scheme results in an acausal equation of motion, so the PTO force may beacausal or anticausal. In practice it will be anticausal, as this the requirement for applyingthe ideal control conditions at more than one frequency.

The ideal conditions are applied at every frequency of the excitation. This results incomplete absorption of the incident wave.

However, if the radiated waves cancel the diffracted andtransmitted waves then there is no net outgoing wave, and hence no energy carried awayfromthe body.


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A frequency at which optimum absorption will occur must be chosen. A common approach isto _nd the peak of the power spectrum of wave elevation [109]. Measuring wave elevationfora full-scale WEC in real seas is not practical, as the value of wave elevation required is attheposition of the WEC, and the surrounding wave _eld will have been altered by radiation anddiffraction. A more realisable approach is to measure the peak in power spectrum ofmeasuredvelocity [49]. As the operating frequency is usually the peak of some spectra or other, it isoften referred to as the peak frequency and will be denoted !p. Another commonly used

nameis tuning frequency, which evokes the analogy of tuning an antenna [107] to have maximumpower transfer at one frequency, and low power transfer at all others.

Capacity factor describes the average annual energy capture as a percentage of the energythat


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would have been captured if operating at rated power over the entire period.

Small WECs generally have highcapacity factors: this is an integral part of their design philosophy [158]. A greater proportionoftime is spent at full stroke, resisting design loads, and generating rated power. Consequentlyasmall proportion of time is spent in the maximising or soft limits regimes, and a largeproportionof time is spent in the hard limits and power set-point regimes. The reverse is true for largeWECs. For a given wave climate, capacity factor is inversely proportional to scale.

More signi_canthowever is that smaller WECs have a lower threshold for displacement limits and thus arenot able to capture all the power as indicated by capture width theory. Small WECs tend tooperate at their maximum power rating for longer periods of time, so have larger capacityfactors than large WECs. When operating under the power maximisation regime, they mayrequire displacement limits, but generally the operating frequency will be close to the naturalfrequency. Large WECs require fewer displacement limits and may give broader bandwidthcausal unrestrained response. It is likely that they will operate at rated power (powerlimitationregime) for their design sea states, and that under the power maximisation regime, theoperatingfrequency will be higher than the natural frequency.

Besides the annual power capture, the other important contributions to the cost of energyarethe cost of the plant (WEC) and the balance of plant costs, which are all the other costs ofthe project apart from the plant costs, such as moorings, cables, installation andmaintenance[159]. The devices may only be a small proportion of the capital costs. As there are many

_xedoverheads per device, the balance of plant costs for a wave farm with a few large WECsmaybe less than that for a wave farm with many small WECs.

The principle behind the wave absorber is that incident waves onto thepaddle are absorbed by the paddle as a wave crest impinges on it

The total energy contained in a wave consists of two kinds: the potentialenergy, resulting from the displacement of the free surface and the kinetic

energy, due to the fact that the water particles throughout the fluid aremoving. This total energy and its transmission are of importance in determining

how waves change in propagating toward shore, the power requiredto generate waves, and the available power for wave energy extraction

devices, for example. looking at the actual sea surface, one sees that the surface is composed of a large

variety of waves moving in different directions andwith different frequencies, phases, and amplitudes. a large number of waves must be superimposed

to be realisticIf a small neutrally buoyant float is placed in a wave tank and its trajectorytraced as waves pass by, a small mean motion in the direction of the waves


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can be observed. The closer to the water surface, the greater the tendency for

this net motion.The total energy per wave per unit width is then simply

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modular and decentralised and therefore less vulnerable to damage9These sub-surface motions due to wave action can be utilisedin a number of ways.but in the longer

term over the year the principal direction may change. Thepossibility of deriving substantial quantitiesof energy without limit of time by relatively simple meansrequirement for a wave-powergenerator is that itless demandingin the level of design, operation and maintenance skillsrequiredMultiple use of ocean platforms1'''

The trajectories are circles which decay exponentially with depth. For a depthofz = -L/2, the values ofA and B have been reduced by the amount e-", orthe radii of the circles are only4% of the surface values, essentially negligible.

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Approximate global distribution of wave power levels (kW/m of wave front)

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It is clear from Equation 2 that t

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Note that in deep water the celerity is independent of water depth, which is not surprising in

view of the fact that the waves do not interact with the bottom. What is interesting, however,

is that the celerity depends on the wave length. Water is therefore a dispersive medium

with respect to deep water surface waves, in much the same way that it is a dispersive

medium for light waves. Shallow water surface waves, on the other hand, do feel the bottom,

and slow down as the square root of the depth. Their speed is not a function of the wave

length.

As surface waves travel across various depths of water their period T does not change (for aproof see the article entitled "Constancy of Wave Period"). In deep water, therefore, the wave

length is constant, but as waves approach a beach the wave length decreases as the square

root of the depth.

Wind-generated waves typically have periods from 1 to 25 seconds, wave lengths from 1 to

1000 meters, speeds from 1 to 40 m/s, and heights less than 3 meters. Seismic waves, or

tsunamis, have periods typically from 10 minutes to one hour, wave lengths of several

hundreds of kilometers, and mid-ocean heights usually less than half a meter. Because of

their long wavelengths, tsunamis often satisfy the criterion for shallow-water waves. For

example, when a tsunami with a wave length of 200 km passes over a depth of 4 km (the

average depth of the oceans) the relative depth is d/L=.02. Since this is less than .05, this

tsunami is a "shallow-water wave", and its celerity depends only on the water depth.

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Tsunami

A tsunami (pronounced sue-nahm-ee) is defined as a series of huge waves that

can cause major devastation and loss of life when they hit the coast. The word

tsunami is a Japanese word which means harbor waves (tsu harbor, nami

waves). The possible causes of a tsunami are underwater earthquake with

the Richter scale magnitude of over 6.75, sub marine rock slides, volcanic

eruptions or if an asteroid or a meteoroid crashes into the water from the

space. A tsunami starts when a huge volume of water is shifted by any of the

phenomenon mentioned. When such a large volume of water is moved, the

resulting wave is very large and can be spread over an area of a hundred

miles. This wave can travel from the point of origin to the coast at great speed.

A tsunami has been known to travel with speeds as high as 600 mph in the

open ocean. This is the speed with which a jet travels and a tsunami can move

from one end of the ocean to the other end in a few hours!

With the advance in technologies over the years, tsunamis can now be

detected before they hit the coast thereby reducing loss of life. Fortunately,


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tsunamis are very rare with approximately six of them hitting the coast every

century, most of them occurring in the Pacific Ocean.

Tides

The biggest waves in our oceans are the tides. These are caused by the gravitational forces

between the earth and the sun and the moon. The moon has the biggest influence because it is

close. It essentially pulls up a bulge in the ocean on the side of the earth closest to it. It

actually pulls up the land too, but not as much. There is also a bulge on the side opposite the

moon. This one is tougher to understand. Ive heard it explained two ways that seem to help:

1. Because of centrifugal force (more an effect of the earth and moon revolving together thanan actual force), the ocean on the side of the earth opposite the moon is sort of thrown

outward, like you are when you go around a bend in your car.

2. Imagine a race car, minivan, and bicycle starting a race. All three accelerate, and from the

point of view of the minivan, the race car shoots out in front and the bicycle gets left behind.

The way they spread out depends on the differences in rate of acceleration. Similarly, the side

of the earth nearest the moon gets pulled out harder than the side away from the moon

relative to the earth itself. The nearside shoots out ahead, and the backside gets left behind.


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HB

I dont care which of these you prefer, as long as you get that there is this bulge on BOTH

sides of the earth even though the moon is only on one side! So this bulge sort of sits there

and we rotate around such that sometimes were under the bulge and sometimes were not.

Since it takes 24 hours for the earth to complete a rotation, plus we have to catch up a little

because while the earth was rotating, the moon was revolving around the earth, we are

directly under a bulge, or experiencing high tide, about every 6 1/2 hours.

Twice daily tides like this are called semidiurnal tides. It is also possible to have only onehigh and one low tide per day. That would be a diurnal tide. Partly this depends on your

latitude, but it turns out that some 400 variables go into predicting the tide at any one place,

so it isnt nearly this simple.

The sun tugs on the oceans too, but since its so far away, it has less influence than the moon.

You can see the influence when the moon and sun and earth are all lined up. This would be

during a full moon and a new moon. With both the sun and moon pulling the same direction,

we get extra high high tides and extra low low tides (a big tidal range). These happen twice a

month and are called spring tides. In between these, during the quarter phases of the moon,

we get tides with the lowest ranges. These are called neap tides.

Global warming: Is wave power important in fighting global warming?


46/51

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Yes

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Fisheries: Is wave power consistent fishing industry interests?

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Yes

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Aesthetics: Does wave power preserve environmental beauty?

Yes

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See also

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External links and resources

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Documents

Wave Energy Converter Patent