Note: Descriptions are shown in the official language in which they were submitted.
~0~?~4~5
SP~Cl~ICAT10_
This invention relates to an energy conversion system
for converting kinetic energy possessed by the wind
into mechanical energy,using a particular compact de-
sign for vertical axis rotors in combination with a
specially adapted tower structure .
A survey of existing configurations for vertical axis
windmills and windturbines shows,that these configurations
can be devided in two groups.In the first group appear the
configurations using sails,cups and flat curved surfaces,
as for instance the Savonius rotor,where more or less drag-
differences between the parts,wrich rotate in wind-direction
and the parts rotating against the wind,are the driving
forces.The other group consists of windturbines with verti-
cal arranged straight and bent blades,having aerofoil cross-
sections and rotate coaxially around a shaft and mountingstructure ,for instance Darrieus rotors,where mainly lift-
forces effectuate a rotation.The first group has found only
limited application in the instrumentation and ventilation
field because of low efficiency .The other group of vertical
axis windturbines encounters difficulties especially if the
feasibility of large windpower units is investigated,which
are comparable in siee to powerplants using fossil fuel.
Then the building cost are progressing excessively and se-
vere construction and stress-problems appear,which in con-
sequence of the use of relatively thin-wal~ blades with
consi~erable dimensions can not be solved easely.Similar
prob~ems exist for the ~esign of windturbines,havin~ a hori-
30ntal axis,also described as axial-flow turbines.Here the
larc~e rotating mass of ro~or blades ,which are flexed con-
3~ si~lously mainly by insteady aerodynamic and inertial loads,
10~425
is a drawb~ck for the development of large windpowerplants.
A primary object of the invention is to provide a wind-
turbine system using such configurations of vertical axis
turbine rotors with very compact and robust forms ,that
these main stress-problems are eliminated and the building
of large windpower plants becomes feasible and practical
dependent on a material and weight saving design for low
manufacturing cost.
It is an other object of t~le invention ,by combination of
such vertical axis turbine rotors with a tower structure ,
having aerodynamic features and mechanical means,to increase
the efficiency of the turbine rotors and to form an adequate
control system for the speed of the rotors.
With the above objects in mind the invention basically ~re-
sents a wind energy conversion system ,where at least a
portion of the kinetic energy possessed by the wind is con-
verted into mechanical energy,com~rising tangential flow
turbine rotors for rotation around the vertical axis,each
rotor having the form of a hollow prism with at least three
vertical in wind-direction curved surfaces ,having a ver-
tical shaft mounted in end-bearings fitted into lower and
upper intermediate support frames and a tower structure to
support a double row of turbine rotors,arranged vertically
and symmetrically behind the tower structure in a down-wind
position,having main-bearing a~semblies for the interme-
diate support f`rames,being allowed to swivel around the tower
struc~ure at least through the effect of wind forces ,and a
w.nd-deflecting snield arranged in front of the tower struc-
3~ ~ure,attach~d rigiàly to the intermediate su~port frames.
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This wind-deflecting shield is curved convexly against ~he
wind-direction on front of the tower structure and further
ex~ends symmetrically along both sides of the tower structure
to the rotation circles of the turbine rotors.thus guide-
surfaces for the airflow are formed ,W~-iCti are moderately
inclined against the wind-direction and oirect a tan~ential
airflow over the curved surfaces of the turbine rotors but
shield the turbine rotor segments rotating against the wind-
direction,said tangential airflow having a direction to
achieve optimum efficiency lor the turbLne rotors.
Usually the tower structure is a design in structural steel,
having a rectangular cross-section ,but also concrete towers
having a round cross-section can be used for this windturbine
system,to lower the building cost.Then the smooth outer sur-
face of the round tower structure in front of the turbinerotors deflectcthe wind, while separate guide vanes,in wind-
direction on both sides of t~ie tower structure~rot~atable around
the vertical axis,the leading edges arranged close to the
smooth outer surface of the tower structure ,can direct the
airflow against the curved surfaces of the turbine rotors with
d;f~rent angles of attack,thus influencing the rotational speed
of the turbine rotors.
Practical embodiments of the invention are described in detail
together with presentation of following drawings:
5 Figure 1 shows a cross-section of a shielded tower structure
with a turbine unit behind,consisting of two vertical
axis turbine rotors,each having the form of a prism.
Figure 2 is a partial view of a windturbine power-plant ~re-
senting the arrangement of several turbine rotor units
3~ with su~port frames and servicing platform.
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Figure 3 shows a cross-section of a shielded tower ctrucsure
with a turbine rotor unit behind,the shield beinK
provided with guide vanes .
Figu.e 4 presents a cross-section of a round concrete tower
with a turbine rotor unit behind,provided with se-
parate guide vanes.
ln figure 1 the tower structure 1 consists of a convential
steel truss tower with rectangular cross-section .the turbine
rotors 2 and 3 are arranged behind the tower structure in
lU down-wind position and have each the form of a prism with the
cross-section of a three-corner polygon.rhe three vertical
surfaces of such a turbine rotor are curved in wind-direction
moderately,first convexly then concavely along the straight
line between the corners of the polygon.rhe bearings 4 for
the shafts of the turbine rotors are indicated and the inter-
mediate support frame 5 can be seen,which is mounted along
with.the main bearing assembly 6 to the tower structure 1.
The wind-deflecting shield 7 is rigidly joined to the inter-
mediate support frame 5,which can rotate freely around the
tower structure 1.
The lay-out of such windturbine system is ruled by several
characteristic parameters,which influence therefore the per-
formance of the system. They are related to the airflow through
the input area in M ~ ,which corresponds to the overall width
of the turbine system and to the considerable smaller airflow
through the area in BB',decreased in size by the vertical
plane area protected by the shield.Further influencial is the
Diameter Dr of the tower structure,depending on the structural
system used,wllich determines the minimum size of the shield
and the diameter ~ of the turbine rotors having the distance d
from each other.
10'~5425
The airflow through the area in AA' towards the turbine rotors
is àeflec~ed to a large extend beyond the area in B~',but part
of the wind-energy loss is recovered again by the increased
velocity of the airflow along the shield towards the turbine
rotors.This effect can be compared with the s~ill-over effect
and flow energy gain of a shroud around an axial flow turbine.
The final inclination of the shield surface close to the ro-
tation circle of the turbine rotor,with the deflection angle
towards the wind-direction ~ ,must be therefore only moderate,
to a~hieve an optimum of the airflow acceleration.If the de-
flection angle is too large ,the loss by the spill-over effect
becomes excessive.It can be seen,that the diameters of the
turbine rotors DX and the distance d determine the position
of the turbine rotors and the available input area in M '.
But too large a rotor diameter effects a low ro~ational speed
because the tip speed of the rotor will not exceed the peri-
pheral wind velocity and the sensitivity for a low wind velo-
city is decreased.lf the rotor diameter is determined,then
also the distance d and the position of the turbine rotors
fo~ows,if one vertical rotor surface can be aligned in one
rotational position of the rotor with the inclination of the
shield surface.In this rotational position then a smooth tan-
gential flow over the turbine rotor surface is attained,having
a fa~ourable angle of attack in relation to the convexly
curved surface part and a maximum lift force is produced
with a resulting main driving force.
In figure 2,correspoding to figure l,can be seen the
vertical row of turbine rotors 3 arranged in down-wind posi-
tion behind the tower structure l.The shafts 10 of the turbine
rotors3 are moun~ed in end-bearings ~,which are fitted into
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the intermediate support frames,having the main bearing
assemblies ~,mounted to the tower structure l.The wind-
deflecting shield 7 extends over the whole length of the ver-
tical row of turbine ~ tors 3.A r.eavy main support frame ~
at ttle ~ower base,rotatable around the tower structure 1,is
combined with a servicing platform 9 containing an energy
transl`Orming installation ,auxiliary servo equipment and con-
trol instrumentation .rhe torque transmission shaft 10 of one
vertical row of turbine rotors 3 is connected with the main
flexible coupling 11 to the gearbox 12.rhe electric output
from the generator 13 is taken off by a slide ring assembly 1~.
In figure 3 the wind-deflecting shield 7 in fron~ of the
tower structure l,joined rigidly to the intermediate sup~ort
frame 5,is not extending towards the rotation circles of the
turbine rotors,but is replaced there on both sides of the
tower structure with the guide vanes 15 and 16.rhese vanes
are connected smoothly to ~he snield 7,but are rotatable to
a smaller degree from the position (a) to the position ~b).
If ttle guide vane has the position (a),then a tangential air-
flow will be directed over the convexly curved surface of theturbine rotor,if the rotational position as shown in figure 1
is reached and the turbine rotor will rotate with maximum
speed.If the guide vane has moved to the position (b),as indi-
cated by the guide vane 16,then the airflow has the general
direction t~wards the center line of the turbine rotor.Now
only irregular vortices and drag-forces are produced such,that
in one peculiar rotational position the tur~ine rotor ceases
to rotate.rrreg~lar movements or oscillations caused by wind-
gusts can be damped by a braKing arrangement.rhe guide vanes
are actuateà by a s~itable speed control system.
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In figure ~ the to~ler structure is a pre-stressed concrete
to~er 17 having a round cross-section and a smooth outer sur-
face and serves also as a wind-deflecting o~ject in front of
the turbine rotors .rhe rotatable guide vanes 1~,19 are posi-
tioned on both sides of the concrete to~-er,seen in wind-direc-
tion,having shafts 20,21 mounted to the intermediate sup~rt-
frame 24.rhe leading edges 22,23,covering the shafts 20,21
against the wind-direction ,are attached close to the smooth
outer surface of the concrete tower,if the guide vanes 1~,19
are in a postion (a) for maximum rotor speed and the deflected
airflow from the front of the concrete tower passes without
turbulence over the guide vanes.As leading edges can be used
stripes of elastic material able to glide with minimum friction
around the tower surface when the intermediate support frame
is swivelling .Because the diameter of the pre-stressed con-
crete tower 17 can be kept relatively small,the overall width
d of.the windturbine system is reduced.Then without loss of
useful wind-energy in 1ront , the turbine rotors are Posi-
tioned moreclosely to each other,both rotation circles over-
lapping,w~lile the rotation is synchronized in the gearbox 12.
Consequently tne omission of the large shield in front of the
turbine rotors ,the lower wind-pressure upon the tower struc-
ture and the smaller dimensions of the supporting structures
contribute to lower building cost.
The general lay-out of the wind-power plant i5 determined
by the requirements for simplicity,low weight and cost and
suitability for mass-production,without lowering the efiicien-
cy of the power sys~em to an impractical value,but sustaining
a high degr~e of durability also under severe weather condi-
3~ tions.~tructural parts and turbine ro~ors form building modules
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of stan~arized size,w~ich can be combined in various numbers
for difierent power output.A turb ne rotor has a weight-saving
design,which is similar to an aircraft wing structure,but has
a simplifieà aluminum ~rame work to secure the cross-section
form only under far less aerodynamic loadir.g.The vertical
prism -surfaces of the turbine rotor are covered with weather
resistant light material as fcr instance aluminum and re-
inforced plastic sheets ,while as construction material honey-
comb structures and urethan-foam can be preferably used.The
horizontal bottom and top faces of the turbine rotor are left
uncoveredlthus saving material and avoiding under winter con-
ditions a piling up of snow,which could hamper the operation
of the power plant.A small degree of form flexibility of the
turbine rotors and temporarely deflexed surfaces,caused by
1~ excessive wind-pressure and teperature influence,will not
change the performance significantly and can be tolerated.
The shafts of the turbine rotors are mounted in self-aligning
bearings and flexible couplings ,while the shaft diameters
and bearing dimensions closer to the tower base are increased,
2~ to be able to transfer the torque increasing with the number
of turbine rotor units and therefore length of shaft assembly.
rhe built-in mechanical flexibility of the tower structure
and turbine rotors requires a suitable oscillation dampening
system,preferably electronically controlled,but lowers the
otherwise high building cost,if an absolutely rigid system of
high strength is persued ,llhe addition of at least one smaller
turbine rotor unit for high rotor speed on top of the tower
structure improves the starting capability of the Dower Dlant
at moderate wind velocities and ~rovides Dower for auxiliary
equipment also .~hen the power plant is not in o~eration.
10 - 10~!5~25
rhe use of a single pre-stressed concr~te tower for a power
plant of medium size can be cost saving especially because
the lar~e àeflecting shielas are then omitted .B~t if a
very large power output is required the steel struss struc-
ture should be preferred.Several such guyed towers of con -
siderable height can be combined in a power plant grou~ ,
where the to~ers are positioned in a circle for instance
and spaced only so far,as not to interfere aerodynamically
with each other.rhe towers of such power plant group can be
1~ guyed toget~er to form a tower group of high stability and
durability,also suitable for sites close to sea and ocean
shores with extrem high wind velocities .
