Note: Descriptions are shown in the official language in which they were submitted.
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Description
The general layout of the Wave Power Generator WPG is shown in
figure -1-. The WPG is basically Mass-Spring-damper combination which
known in so many application.
In this invention the electrical generator by which the electrical power
generated resemble the damper.
To understand the operation let us look to fig-1 . Consider the event
when wave moves from right to left, two wave components are affect on
WPG body, these forces are as follow
1- Horizontal force Fh which is due to horizontal ( surface ) wave
movement.
2-Vertical force Fo which is due to Oscillating wave column OWC wave
movement.
when the wave strike the WPG both of above forces Fs & Fo combined to
produce a torque rotating the WPG CCW. it is useful to say that when the
wave strike the WPG , some of energy in Fs component transform to
vertical component,i.e. Fo increases.
As a result of WPG CCW rotation, the Active Mass M start moving left
down due to ( inclined surface) the instantaneous force acting of M Fm
equal to
Fm= a*m* sin (th) ........................ 1
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a= Gravitational acceleration ( app= 9.8 N.m/ sec 2 )
m= active mass M weight in Kg.
th= instantaneous incline angle of WPG with respect to horizon
the active mass keep moving in same direction at variable velocity V(t)
. Until it finally stopped due to :
1- Spring force Fs which always try to push the active mass in opposite
direction, the Fs is proportional to displacement ( d) of the active mass M.
so Fs= k*d , k is spring constant ...............2
2- damping force Fd which due to frictions of the active mass bearings
with surface & other friction force(s) Ff & force due to electrical power
generator Fg , both damping forces are proportional to active mass
velocity v.
so Fd= z (V(t)) , z is damping factor ............................ 3
on other hand the wave get weaker as the wave moves along the WPG.
So the active mass eventually stopped then pushed to move in opposite
direction due to spring force Fs so the WPG rotated clock wise CW, but
the damping force again oppose the active mass movement in both
strokes (ccw,&cw).
So the WPG keep oscillating at certain frequency.
For maximum power delivery the WPG must resonate with Ocean waves
frequencies strike it. this is the key point of this invention.
The frequency at which the WPG resonate will depends on ( m,k,&z) .
In this invention m,& k are constant for a WPG . but to tune the WPG
frequency with Ocean wave we would change the damping factor z as
requested that z =Z(t) , t is the time.
In normal operating state Z(t) set to keep the system in under damp state
with variable frequency range .
But in real world the Ocean/sea wave variable height, variable frequency,
variable wave length & variable speed.
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To maximize the power within above variables , we have to consider the
factors which categorized as follow :
1- At design level, these factors should be considered
a-The shape & dimensions of WPG.
b-Weight & material of the active mass & weight of the Gross WPG.
c- Spring coefficient value, electrical generator rating & characteristics
(rotor weight, no.of winding ....etc).
d-Location of each components within the WPG.
2-At operating level
Output voltage & current of the electrical generator will be monitored by
the ( Monitoring & control unit MCU) . By online reading of above output
voltage & current the MCU can determine the instantaneous power
generated . Once the MCU measure the power output it will change the
value of magnetic excitation field B(t) of the electrical alternator/generator
For maximum power generation.
Other functions of the MCU will be discussed in more details in next
sections.
Description of components
The components can be classified as follow
1- Mechanical Components
The main component as follow
1.1 The active mass
M is an important part of the WPG , the active mass play an important
role in determining the power generation & the natural frequency of the
WPG.
As shown in fig-1 the active mass moves in straight line , but to reduce
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the friction as possible & keep in in straight line , it should be loaded on
proper bearing & proper bearing number. That bearing should be running
through rails( channels) to keep it moves in strait line.
The friction of that bearings highly affect the efficiency of the system.
So regular ball bearing is quite suitable .
The active mass weight should be calculated at design level.
The material could any material that have density above water density
1000Kg/m3 ( the more density is better ), of course the lowest cost will be
preferred * to ease the installation & mobilization the active mass should
be sliced to proper sizes.
1.2 Springs
The springs plays an important role in the principle of operation with
active mass ,& electrical generator.
The spring factor k described before in equation -2 will be related to
active mass weight M (Kg) according to equation below
Wo"2= k/Me .................4
Me=M+ Mg,
where Mg proportional to generator rotor or mass of coil of linear
generator.
:Wo"2 is the square of maximum radian frequency of the system ,i.e the
frequency with NO friction . Practically the maximum frequency would be
less because we cannon avoid the friction . The value of k would be
determined as design level.
1.3 Electrical Generator & its mechanism
The electric generator has two very important functions , 1st converting the
mechanical power captured from wave to electrical power& 2"d by
controlling its rotating magnetic field Bi(t), the WPG tuned to proper
frequency for maximum power delivery.
Because the active mass move linearly & for practical & cost reduction we
can avoid the use of linear generator, In stead we can convert the linear
motion to rotating as shown in fig-2.
A teethed Rubber belt or chain firmly connected to active mass so when
the active mass moved the belt(s)/chain(s) will move too. This belt/chain
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run on two sprockets at the two end.
So that when the active mass moves right & left the sprockets rotate
CCW,& CW.
At any of these two sprocket, the electrical generator coupled to it through
gear box with proper speed ration determined as design level.
Regarding the gear box, the higher speed will be at generator side.
The rotating generator would be regular 3-Ph generator runs at'
variable speed RPM'.
1.4 WPG Capsule (Shell )
The WPG capsule is the vessel which contains all other components
The most important properties for it is
- High resistance for corrosion for its out side which exposed to water.
-The materials weight should be as minimum as possible.
The dimensions & shape of the capsule would highly affect the WPG
efficiency. The top view of the WPG shown in fig-3
Electrical components
The basic electrical layout is shown in fig-5.
2.1 Monitoring & Control Unit ( MCU)
The MCU is the Sole & brain of the WPG, by which the maximum power
generated by controlling the magnetic field of the generator Bi.
The MCU could a general purpose programmable controller & data
acquisition available in the market.
In addition many other tasks executed by MCU which can be categorized
as follow.
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2.1.1 monitoring & measuring the power output online
The MCU measure the power on line by continuously by measuring the
output voltage & current of the generator after been rectified. In order to
a- Maximum power delivery as described in above or as in section 3.0
WPG tuning.
b- in case of the output power exceed the maximum allowable average
power of the generator ( due to very high wave power strike the WPG) ,
MCU will manage to reduce the power output by pushing the system
away from the maximum power generation by mean of adjusting the
magnetic excitation field Bi of generator to reduce the power, but the
MCU continuously monitors the output power to keep it near the
maximum allowable power as possible.
c- In case of zero power delivered to final destination such as due to
power cable disconnection, the MCU will cease the power generation
electrically by pushing the system to be over damped by set Bi(t) to
maximum value.
d- As an option if cable disconnection combined with very high wave so
that action described in -c not enough MCU will stop the active mass
oscillation mechanically.
2.1.2 Alarming
MCU can send alarm signal such as flash or by wireless device(s)
available . Alarming should be necessary for the cases b,c,& d described
in section 2.1.1.
2.1.3 Input Data
The input data needed by MCU is the setting parameter for MCU (default
setting), program by which the maximum power delivered, update data or
even debugging.
Such setting parameter in necessary for calculation of exact excitation
magnetic field Bi , to attain the maximum power delivery.
Also that data tell the MCU how to make the decision in sec.2.1.1 & 2.1.2
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2.1.4 Output data
We can suggest many output data such as the current power, alarms
described above .............etc
2.2 The generator & rectifier
The electrical generator is a classical 3-phase alternator & its output will
be rectified as shown in fig-5 .
Another function of the rectifier in addition to AC/DC conversion is to
send the sensing signal Vs to be processed by MCU , by this signal the
MCU detect the current frequency of the active mass .
2.3 Inverter & battery
The final output preferred -for practical reasons- to be AC voltage ( 220-
110 V)/(50-60 Hz) to be used in home appliances & to reduce the copper
loss which is less in higher voltage as compared if the output directly
taken out of the battery.
The battery shown in fig-5 is NOT a storage battery, instead it is a basic
component of the electrical system.
3.0 WPG Tuning
Let us return to equation -4 above where the natural radian frequency
Wo= 'l(k/Me), zero damping force
But when the damping forces considered the instantaneous frequency Wi
would be approximately :
Wi= 4 [ (K/Me)- ((Ka*Bi^2 / 2Me+ C)^2) ] ...............5
by solving a 2nd order differential equation in under damping state.
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Ka= a constant depending on alternator factor such as total length of
conductor exposed to magnetic field...... etc, gearbox ratio,& load current
(I) shown in fig-5.
C= is a constant proportional to the friction forces in the system.
So we can set the WPG natural frequency for maximum power delivery by
changing the generator/alternator excitation field Bi as shown in equation
-5.
So the frequency Wi always less than Wo , but should be greater than
zero to keep the system in under damp state, if we increased the Bi so
that the value in bracket under square root become negative then the
system get in over damped state which should be avoided in normal
operation except the case mentioned in section 2.1.1-C.
For practical purpose we can choose Wo= II , then F0= 0.5 Hz
So the maximum WPG natural frequency will be always less than 0.5 Hz
Important Comments
The invention described so far is the basic design just as the prove of
concept.
Many improvements/options can be done, for example using a linear
generator would increase the efficiency due to avoidance of friction in
gear box described in section 1.3.
Also we can improve the power efficiency if we design the WPG according
to some practical experiments' or by computer simulation .
Offshore design
The invention described so far seem to be designed for Onshore .
However we can build the Offshore ocean power generator based on the
onshore WPGs as shown in fig-4.
The main differences are as follow
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1- A centre Buoy needed to connect the WPGs .
2- At least three WPG needed to compose the Offshore design .
3- The WPGs would swinging independently at frequencies explained
before, each of WPG hanged by two powerful joints & rods as shown in
fig.4
4-The mooring would by through the central buoy.
5- The central buoy will contain the Storage battery & the central inverter
at higher voltage (in Kv) because the longer distance & higher power.
6- The output AC voltage cable should be routed under the central buoy at
proper depth.
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Figures & components
Fig-1- : The basic view of the wave power Generator WPG
1- The active mass
2- The Springs
3-Spring channel ( rod).
4-Upper active mass bearings.
5-Lower active mass bearings.
6-Lower active mass bearings channel/ rail.
7-Upper active mass bearings channel/rail.
8- Linear generator or generator mechanism shown in fig-2.
9- Magnetic excitation coil in case of using the linear generator.
10- Electrical and electronic unit shown in fig-5.
11- Flexible output power cable.
12- The antenna.
13- The service cover for maintenance & installation.
14- Front buoy.
15- Rear buoy.
16- Mooring.
17- Emergency flashing light.
18- WPG capsule/ shell.
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Fig-2 : Generator mechanism
1- Teethed belt(s) or metallic chain(s).
2-Sprocket with gearbox coupling.
3-Sproket.
4- Sprocket to gearbox coupling.
5- Gearbox.
6- 3-phase alternator.
7- 3-phase output cable shown in fig.5.
8-Magnetic excitation cable of the 3-phase alternator shown in fig.5.
9- The active mass.
10.Springs.
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Fig-3- Top view of the WPG ( Onshore design)
1- WPG Capsule ( Shell) .
2-Wave reflector.
3-Output cable gland.
4-Output AC- voltage flexible cable.
5- Removable service cover for maintenance & installation.
6- Antenna.
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Fig-4 : Offshore design Wave Power Generator
1- Central buoy & the container for Storage battery & inverter.
2.1,2.2,&2,3 Swinging joints & bearings of the 3-WPG(s).
3.1,3.2,& 3.3 Connection joints & bearings by which the WPG(s)
connected to central buoy through out the connection rods ( items
7.1,7.2,&7.3).
4.1,4.2,&4.3 the Onshore WPG(s) shown in figure-1.
5.1,5.2,5.3 the flexible cables deliver the DC current produced by each
WPG to storage battery inside the central buoy.
6.1,6.2,&6.3 wave reflector of the WPG(s).
7.1,7.2,& 7.3 a connection rods which connect the swinging joints and
connection joints described above.
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Fig-5 : Electrical & Electronic Unit
1- Electrical 3-phase alternator.
2- Three phase AC/DC rectifier.
3- DC/AC inverter for Onshore design.
4- Monitoring & Control Unit MCU.
5-Wireless communication unit.
6- Antenna.
7- AC voltage output cable gland for Onshore design.
8- AC voltage output flexible cable shown fig-1 & fig-3.
9- DC voltage output cable gland for Offshore design.
10- DC voltage output flexible cable shown in fig-4.
11- Excitation field coil of the alternator shown in fig-2.
