COMMANDE D'ENERGIE SOLAIRE

SOLAR ENERGY CONTROL

Description

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,SOLAR ENERGY CONTROL
This invention is in the field of solar energy systems and in particular
controlling the
energy received by a solar receptor such as a boiler, oven, or the tike.
BACKGROUND
Considerable development is taking place in an attempt to efficiently and
effectively
harness solar energy. One typical system involves a curved mirror shaped to
gather and
focus solar rays into a cone-shaped focused solar beam. A solar receptor is
placed near
the apex of the cone and considerable heat can be generated irr the receptor
to perform a
desired function that requires heat energy. The curved mirrors are typically
made up of
an array of smaller flat mirror segments arranged on a curved frame to achieve
the
focusing effect, and can be quite large, depending on the energy requirement
of the
receptor.
Such solar systems are generally placed in arid locations where the sun is
reliably
available so that the heat generated by the solar beam will be at least
substantially
consistent. The solar receptors can include boilers, thermal reactors,
Stirling engines, and
the like. A problem with such systems is controlling the amount of heat energy
received
by the solar receptor. For example a Stirling engine has no control that
~rresponds to a
throttle whereby the energy supplied to the engine corresponds to the load.
When
powering a Stirling engine with solar energy from a mirror array, the solar
energy
supplied to the engine is substantially constant, and so the load must be
maintained at a
sufficient level to use all the solar energy supplied by the mirror array. ff
the load drops,


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the engine very quickly overheats and is damaged. Similar overheating and
damage can
occur with other solar receptors as well.
To provide a level of control, the flat mirror segments on the mirror array
can be mounted
such that they can be moved by an actuator. Controllers activate the actuators
and pivot
the mirrors to produce the focused cone-shaped solar beam. The amount of
energy
received by the receptor can thus be varied. Thus when overheating is detected
the
mirror segments are moved out of focus to reduce the amount of energy
received, such as
when the load on a Stirling engine drops. Such systems also allow a receptor
to be heated
slowly by gradually bringing the flat mirror segments into focus until the
maximum or
desired energy is received. The movable mirror segments, actuators, and
controls are
complex and so these systems are very costly to build and maintain.
It is also known to prevent damage from overheating by moving a plate into
position to
block the solar beam, or a portion thereof. Such plates are made from
refractory
materials in order to withstand the intense heat of the solar beam, and are
quite fragile
and subject to damage from the elements.
SUMMARY OF THE INVENTION
zo
It is an object of the present invention to provide a solar energy control
apparatus that
overcomes problems in the prior art. 1t is a further object of the present
invention to
provide such a control apparatus that prevents a portion of a focused solar
beam from
contacting a solar receptor.
It is a further object of the present invention to provide such a control
apparatus that
comprises a shutter movable from an open position, where the complete solar
beam hits


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the solar receptor, to at least a partially closed position wherein a portion
of the solar
beam is blocked and prevented from hitting the solar receptor. It is a further
object of the
present invention to provide such an apparatus comprising one or more shutter
plates,
each having a cooling conduit defined in an interior thereof, and a source of
cooling fluid
connected to flow through the cooling conduit to remove heat from the shutter
plate.
The present invention provides a shutter assembly adapted to be positioned
between a
curved mirror that is operative to focus solar rays into a focused solar beam,
and a solar
receptor that is oriented to receive the focused solar beam. The solar
receptor will
1Q typically be a reaction chamber, Stirling engine, or the like and the
curved mirror will be
provided by an array of mirror segments.
In one embodiment, the shutter assembly comprises a plurality of shutter
plates pivotally
mounted to a shutter frame, and a shutter control operative to move the
shutter plates
i5 from an open position, where the complete solar beam hits the solar
receptor, to a
plurality of partially closed positions wherein varying portions of the solar
beam are
blocked and prevented from hitting the solar receptor, and then to a closed
position where
the solar beam is completely blocked. Each shutter plate includes an internal
cooling
conduit and a source of cooling fluid is connected to each cooling conduit
such that
20 cooling fluid circulates through the cooling conduits to remove heat from
the shutter
plates.
In a send embodiment the shutter assembly comprises an annular shutter plate
defining
a central aperture. Again the annular shutter plate includes one or more
internal cooling
25 conduits and a source of cooling fluid is connected to the cooling conduits
such that
cooling fluid circulates through the cooling conduits to remove heat from the
annular
shutter plate. The annular shutter plate is mounted transversely to the solar
beam. When


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the annular shutter plate is located close to the solar receptor, the complete
solar beam
can pass through the central aperture and hit the solar receptor. As the
annular shutter
plate is moved away from the solar receptor toward the curved mirror the outer
portion of
the cone-shaped solar beam hits the annular shutter plate and is thus
prevented from
hitting the solar receptor. Due to the conical shape of the beam, the annular
shutter plate
can be wide enough that when located a considerable distance from the solar
receptor, the
great majority of the solar beam is blocked, with only a small portion passing
through the
central aperture to hit the solar receptor. In this embodiment a linear
shutter control
controls the distance between the annular shutter plate and the solar
receptor.
The cooling fluid could conveniently and effectively be a mixture of water and
glycol
such as is used in engine cooling systems. Such a mixture pumped in large
volumes has
the ability to remove a large amount of heat from the shutter plates, and is
safe and
convenient to handle. It is contemplated that other Quids, both liquid and
gaseous, could
be used as cooling fluids as well.
It is also contemplated that the shutter plates could be insulated or
reflective on a rear
surface thereof facing the solar receptor. Then during periods of cloud or at
night, the
shutter plates could be closed and heat would be retained in the solar
receptor rather than
ZO radiating out through the opening in the shutter assembly.
DESCRIPTION OF THE DRAWINGS:
While the invention is claimed in the concluding portions hereof, preferred
embodiments
are provided in the accompanying detailed description which may be best
understood in
conjunction with the accompanying diagrams where like parts in each of the
several
diagrams are labeled with like numbers, and where:


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Fig. 1 is a schematic side view of a shutter assembly of the invention set up
between a curved mirror and a solar receptor in the open position with all of
the
solar beam being received by the solar reoeptar;
Fig. 2 is a schematic side view of an embodiment of the shutter assembly of
Fig. 1
with pivoting shutter plates showing the shutter assembly in a partially
closed
position with only a portion of the solar beam being received by the solar
receptor;
Fig. 3 is a schematic side view of an alternate embodiment of the shutter
assembly
of Fig. 1 with an annular shutter plate showing the shutter assembly in a
partially
closed position with only a portion of the solar beam being received by the
solar
receptor;
Fig. 4 is a perspective rear view of a shutter assembly comprising pivoting
shutter
plates such as could be used in the embodiment of Fig. 2 showing the shutter
plates in the open position;
Fig. 5 is a perspective front view of the shutter assembly of Fig. 4 showing
the
shutter plates in the open position;
Fig. 6 is a perspective rear view of the shutter assembly of Fig. 4 showing
the
shutter plates in partially closed position;


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Fig. 7 is a perspective front view of the shutter assembly of Fig. 4 showing
the
shutter plates in an almost fully closed position, and also showing a shield
plate to
protect the shutter mechanism;
Fig. 8 is a schematic perspective rear view showing the internal cooling
conduit in
one of the shutter plates;
Fig. 9 is a front view of sn alternate annular shutter plate such as would be
used in
the shutter assembly of Fig. 3;
Fig. 10 is a schematic illustration of the operation of the shutter assembly
of Fig.
lo.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS:
Fig. 1 schematically illustrates a shutter assembly 2 of the invention set up
between a
curved mirror 4 and a solar receptor 6 such as are known in the prior art. The
curved
mirror 4 focuses solar rays into a cone-shaped solar beam 8, and the solar
receptor 6 is
positioned substantially at the apex of the cone to receive the solar beam 8.
The heat
generated by the solar beam 8 in the solar receptor 6 is used in various ways
as are well
known in the art.
In Fig. 1, the shutter assembly 2 is shown in the open position where all of
the solar beam
passes through the shutter assembly and is received by the solar receptor 6.
Fig. 2
schematically illustrates the operation of an embodiment of the shutter
assembly 2 that
uses movable shutter plates to block the solar beam 8 and prevent varying
portions
thereof from hitting the solar receptor 6. Fig. 2 illustrates the shutter
assembly 2 in a


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partially closed position with only a portion of the solar beam 8 being
received by the
solar tsceptor 6.
Such a shutter assembly 2 is illustrated in Figs. 4 - 8. The shutter platxs 10
are pivotally
mounted on a shutter frame 12 and define a central aperture 14. The shutter
plates 10 are
also pivotally connected via links 20 to a shutter ring 16 that rotates with
respect to the
shutter frame 12 in response to rotation of a drive motor 18. Thus the shutter
plates 6 can
pivot from the open position of Figs. 4 and 5, through the partially closed
position of Fig.
6, and through the more fully closed position of Fig. 7 to a completely closed
position.
It can thus be seen that as the shutter plates 6 move from the open position
to the closed
position, varying portions of the solar beam 8 will be blocked and prevented
from hitting
the solar receptor 6. The heat energy received by the solar receptor 6, and
thus the
temperature thereof, can be thus be finely controlled by activating the drive
motor 18 to
open or close the shutter plates 10. As can be seen, unlike a camera shutter,
the shutter
plates 10 do not overlap. The solar beam 8 can pass between the edges of the
shutter
plates 10, as well as through the center of the central aperture 14. Fig. 8
illustrates the
front of the shutter assembly 2 that faces the curved mirror 4 with a shield
plate 21
installed to protect the shutter mechanism.
While the particular arrangement illustrated is simple and convenient, it is
contemplated
that other arrangements would also serve the purpose of moving the shutter
plates 10 in
and out of the solar beam 8 to block reception by the solar receptor 6, and
such other
arrangements are contemplated to fall within the scope of the invention.
Fig. 8 illustrates in one shutter plate 10 the internal cooling conduit 22
that is defined in
the interior of each shutter plate 10. The shutter plates 10 are quite thick,
and the cooling


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conduit 22 is provided quite simply in the illustrated embodiment by drilling
a pair of
holes 24 from the outer edge of the shutter plate 10 on an angle toward the
inner end
thereof. The holes 24 meet near the inner end and thus form the cooling
conduit 22.
Hose barbs 2G are attached to the exposed ends of the holes 24 to facilitate
connection of
S the cooling conduit 22 to a cooling fluid source 28. A cooling fluid, such
as a water-
glycol mixture, air, or the like is circulated from the cooling fluid source
28 through the
cooling conduit 22.
The holes 24 are sized such that they pass quite close to the surface of the
shutter plate 10
to quickly draw heat away from the surface_ The shutter plates are made from
material
that conducts heat well and also withstands exposure to the elements. Aluminum
provides a good material for the shutter plates 10, however other materials
such as copper
could also be used. The front surface of the shutter plates 10, facing the
curved mirror 4,
could also be polished to reflect the solar beam 8 such that less heat is
absorbed that must
be removed by the cooling fluid. The shutter assembly 2 could be oriented at
an angle to
the solar beam 8 as well, such that reflected solar rays do not reflect back
on the shutter
assembly 2 from the mirror.
Further, where the shutter assembly 2 is located closely adjacent to the solar
receptor 6 as
in Figs. 1 and 2, the shutter plates 10 could be insulated or reflective on a
rear surface
thereof facing the solar receptor 6. Then during periods of cloud or at night,
the shutter
plates 10 could be closed and heat would be retained in the solar receptor 6
rather than
radiating out through the central aperture 14 and being lost.
Fig. 9 illustrates an alternate shutter assembly 102, suitable for use as
illustrated in Figs. 3
and 10. The shutter assembly 102 comprises an annular shutter plate 110. A
plurality of
internal cooling conduits 122 are defined in the annular shutter plate 110 in
a similar


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manner to that described above and are connected to a cooling fluid source.
The annular
shutter plate 110 is again made from heat conductive material to facilitate
removal of heat
by cooling fluid circulating thmugh the cooling conduits 122.
As illustrated in Fig. 10 when the annular shutter plate 110 is located in
position A, close
to the solar receptor 6, all of the solar beam 8 passes through the central
aperture 114 and
hits the solar receptor 6. The aimular shutter plate 110 is mounted on a track
or the like
such that same can be moved away from the solar receptor 6. As the annular
shutter plate
moves away from the solar receptor 6 the outer portions of the conical solar
beam 8
10 are blocked by the annular shutter plate 110. In position -B; a
smallportiorr~of-Ehe solar
beam 8 is blocked, while at position C a very large portion of the solar beam
8 is blocked.
While the particular arrangements illustrated are simple and convenient, it is
contemplated that other arrangements would also serve the purpose of moving
the shutter
plates 10 in and out of the solar beam 8 to block reception by the solar
receptor 6, and
such other arrangements are contemplated to fall within the scope of the
invention.
Thus the foregoing is considered as illustrative only of the principles of the
invention.
Further, since numerous changes and modifications will readily occur to those
skilled in
the art, it is not desired to limit the invention to the exact construction
and operation
shown and described, and accordingly, all such suitable changes or
modifications in
structure or operation which may be resorted to are intended to fall within
the scope of
the claimed invention.

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