U.S. patent application number 14/196928 was filed with the patent office on 2014-07-03 for concentrating solar energy collector.
This patent application is currently assigned to Cogenra Solar, Inc.. The applicant listed for this patent is Cogenra Solar, Inc.. Invention is credited to Gilad ALMOGY, Brian E. Atchley, Amir BAR, Nathan P. BECKETT, Andrey BOCHKARIOV, Ratson MORAD, Radu RADUTA, Ofer RICKLIS, Amir A. WEISS.
Application Number | 20140182660 14/196928 |
Document ID | / |
Family ID | 44971429 |
Filed Date | 2014-07-03 |
United States Patent
Application |
20140182660 |
Kind Code |
A1 |
ALMOGY; Gilad ; et
al. |
July 3, 2014 |
CONCENTRATING SOLAR ENERGY COLLECTOR
Abstract
Systems, methods, and apparatus by which solar energy may be
collected to provide electricity, heat, or a combination of heat
and electricity are disclosed herein.
Inventors: |
ALMOGY; Gilad; (Palo Alto,
CA) ; MORAD; Ratson; (Palo Alto, CA) ;
RICKLIS; Ofer; (Kfar-Sava, IL) ; BECKETT; Nathan
P.; (Oakland, CA) ; BAR; Amir; (Sunnyvale,
CA) ; BOCHKARIOV; Andrey; (Rosh Ha'ayin, IL) ;
WEISS; Amir A.; (Sunnyvale, CA) ; RADUTA; Radu;
(Mountain View, CA) ; Atchley; Brian E.; (Oakland,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cogenra Solar, Inc. |
Mountain View |
CA |
US |
|
|
Assignee: |
Cogenra Solar, Inc.
Mountain View
CA
|
Family ID: |
44971429 |
Appl. No.: |
14/196928 |
Filed: |
March 4, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13079193 |
Apr 4, 2011 |
8669462 |
|
|
14196928 |
|
|
|
|
61431603 |
Jan 11, 2011 |
|
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61347585 |
May 24, 2010 |
|
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Current U.S.
Class: |
136/246 |
Current CPC
Class: |
Y02E 10/47 20130101;
F24S 30/425 20180501; H01L 31/0525 20130101; Y02B 10/20 20130101;
Y02E 10/40 20130101; Y02E 10/60 20130101; Y02E 10/52 20130101; F24S
40/52 20180501; H01L 31/0521 20130101; Y02B 10/70 20130101; H01L
31/0547 20141201; H02S 40/44 20141201; F24S 2030/134 20180501; F24S
23/74 20180501 |
Class at
Publication: |
136/246 |
International
Class: |
H01L 31/052 20060101
H01L031/052 |
Claims
1. A concentrating solar energy collector comprising: a linearly
elongated reflector having a linear focus; a linearly elongated
receiver oriented parallel to and located at or approximately at
the linear focus of the reflector and fixed in position with
respect to the reflector; and a support structure supporting the
reflector and the receiver and pivotally mounted to accommodate
rotation of the support structure, the reflector, and the receiver
about a rotation axis parallel to the linear focus of the
reflector; wherein the receiver comprises solar cells that, in
operation of the concentrating solar energy collector, are
illuminated by solar radiation concentrated by the reflector onto
the receiver; wherein the reflector comprises a plurality of
linearly elongated reflective elements each having a long axis, and
the linearly elongated reflective elements are arranged on and
attached to a sheet of metal in two or more parallel side-by-side
rows with the long axes of the linearly elongated reflective
elements and the rows oriented parallel to the linear focus of the
reflector, the sheet of metal providing longitudinal support
parallel to the rotation axis along the length of the linearly
elongated reflective elements; and wherein each row of linearly
elongated reflective elements includes two or more of the linearly
elongated reflective elements arranged end-to-end such that gaps or
joints between the linearly elongated reflective elements in each
row are not next to gaps or joints between linearly elongated
reflective elements in an adjacent row.
2. The concentrating solar energy collector of claim 1, wherein the
linearly elongated reflective elements are of two or more different
lengths.
3. The concentrating solar energy collector of claim 2, wherein in
each row of linearly elongated reflective elements arranged
end-to-end each gap or joint between linearly elongated reflective
elements is separated from its nearest neighbor gap or joint in the
other rows of linearly elongated reflective elements by at least
one row of linearly elongated reflective elements.
4. The concentrating solar energy collector of claim 1, wherein the
receiver comprises one or more coolant channels through which, in
operation of the concentrating solar energy collector, fluid may
pass to collect heat from solar radiation concentrated by the
reflector onto the receiver.
5. The concentrating solar energy collector of claim 1, wherein:
the support structure comprises a plurality of transverse reflector
supports to which the sheet of metal is attached; each transverse
reflector support extends transversely to the rotation axis to
support the reflector; and upper surfaces of the transverse
reflector supports orient the sheet of metal, and thus the linearly
elongated reflective elements attached to it, in a desired
orientation with respect to the receiver.
6. The concentrating solar energy collector of claim 1, wherein the
reflector has a parabolic curvature transverse to its long
axis.
7. The concentrating solar energy collector of claim 1, wherein the
linearly elongated reflective elements are flat or substantially
flat transverse to their long axes.
8. The concentrating solar energy collector of claim 1, wherein:
the receiver comprises one or more coolant channels through which,
in operation of the concentrating solar energy collector, fluid may
pass to collect heat from solar radiation concentrated by the
reflector onto the receiver; the linearly elongated reflective
elements are flat or substantially flat transverse to their long
axes; and the support structure comprises a plurality of transverse
reflector supports to which the sheet of metal is attached, the
transverse reflector supports supporting the reflector and
extending transverse to the rotation axis.
9. The concentrating solar energy collector of claim 8, wherein the
linearly elongated reflective elements are of two or more different
lengths.
10. The concentrating solar energy collector of claim 9, wherein in
each row of linearly elongated reflective elements arranged
end-to-end each gap or joint between linearly elongated reflective
elements is separated from its nearest neighbor gap or joint in the
other rows of linearly elongated reflective elements by at least
one row of linearly elongated reflective elements.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/079,193 filed Apr. 4, 2011 and titled
"Concentrating Solar Energy Collector", which claims priority to
U.S. Provisional Patent Application No. 61/347,585 filed May 24,
2010 and titled "Concentrating Solar Energy Collector" and to U.S.
Provisional Patent Application No. 61/431,603 filed Jan. 11, 2011
and also titled "Concentrating Solar Energy Collector," all of
which are incorporated herein by reference in their entirety.
FIELD OF THE INVENTION
[0002] The invention relates generally to the collection of solar
energy to provide electric power, heat, or electric power and
heat.
BACKGROUND
[0003] Alternate sources of energy are needed to satisfy ever
increasing world-wide energy demands. Solar energy resources are
sufficient in many geographical regions to satisfy such demands, in
part, by provision of electric power and useful heat.
SUMMARY
[0004] Systems, methods, and apparatus by which solar energy may be
collected to provide electricity, heat, or a combination of
electricity and heat are disclosed herein.
[0005] In one aspect, a concentrating solar energy collector
comprises a linearly extending reflector having a linear focus and
a reflective surface that is or approximates a portion of a
parabolic surface from primarily on one side of a symmetry plane of
the parabolic surface, a linearly extending receiver oriented
parallel to and located at or approximately at the linear focus of
the reflector and fixed in position with respect to the reflector,
a support structure supporting the reflector and the receiver and
pivotally mounted to accommodate rotation of the support structure,
the reflector, and the receiver about a rotation axis parallel to
the linear focus of the reflector, and a linear actuator pivotally
coupled to the support structure to rotate the support structure,
the reflector, and the receiver about the rotation axis. The
reflective surface may be or approximate a portion of the parabolic
surface from entirely on one side of the symmetry plane of the
parabolic surface. The rotation axis may be oriented in an
East-West or approximately East-West direction, for example.
[0006] The receiver may comprise solar cells that, in operation of
the solar energy collector, are illuminated by solar radiation
concentrated by the reflector onto the receiver. The receiver may
additionally or alternatively comprise one or more coolant channels
through which, in operation of the solar energy collector, fluid
may pass to collect heat from solar radiation concentrated by the
reflector onto the receiver.
[0007] The solar energy collector may optionally comprise a drive
shaft extending parallel to the rotation axis and mechanically
coupled to the linear actuator to transmit rotational motion of the
drive shaft to drive the linear actuator. The linear actuator may
be pivotally coupled to the drive shaft, and the drive shaft
isolated from thrust loads on the linear actuator.
[0008] The support structure may be pivotally mounted at a
plurality of pivot points, in which case the linear actuator may be
one of a plurality of linear actuators each of which is located
near a corresponding one of the pivot points and pivotally coupled
to the support structure to rotate the support structure, the
reflector, and the receiver about the linear actuator's
corresponding one of the pivot points. One or more drive shafts,
optionally present, may extend parallel to the rotation axis and be
mechanically coupled to the linear actuators to transmit rotational
motion of the drive shaft to drive the linear actuators. The linear
actuators may be pivotally coupled to the drive shaft or shafts,
and the drive shaft or shafts may be isolated from thrust loads on
the linear actuators.
[0009] The support structure may comprises a plurality of
transverse reflector supports supporting the reflector and
extending transverse to the rotation axis, and a corresponding
plurality of receiver supports each connected to and extending
from, or approximately from, a single end of a corresponding
transverse reflector support to support the receiver above the
reflector. In such cases, the linear actuator may be pivotally
coupled to a transverse reflector support to rotate the support
structure, the reflector, and the receiver about the rotation axis.
Alternatively, the linear actuator may be pivotally coupled to a
receiver support to rotate the support structure, the reflector,
and the receiver about the rotation axis.
[0010] The support structure may comprises a rotation shaft
coincident with the rotation axis and a lever arm attached to the
rotation shaft, in which case the linear actuator may be pivotally
coupled to the lever arm to rotate the rotation shaft and thereby
rotate the support structure, the reflector, and the receiver about
the rotation axis.
[0011] The receiver may comprise upper and lower surfaces on
opposite sides of the receiver, with the lower surface of the
receiver located at or approximately at the linear focus of the
reflector and the upper surface of the receiver comprising solar
cells arranged to face the sun when the solar energy collector
(e.g., the reflector and the receiver) is oriented to concentrate
solar radiation on the lower surface of the receiver. The solar
cells of the upper surface of the receiver may generate sufficient
electricity under a solar irradiance of at least about 100 Watts
per square meter (W/m.sup.2) of solar cell, at least about 150
W/m.sup.2 of solar cell, at least about 200 W/m.sup.2 of solar
cell, at least about 250 W/m.sup.2 of solar cell, at least about
300 W/m.sup.2 of solar cell, at least about 350 W/m.sup.2 of solar
cell, or at least about 400 W/m.sup.2 of solar cell to power a
drive system, including the linear actuator, coupled to the support
structure to rotate the support structure, the reflector, and the
receiver about the rotation axis. If the receiver comprises one or
more coolant channels as described above, the solar cells of the
upper surface may additionally, or alternatively, power one or more
pumps that pump fluid through the coolant channels.
[0012] The reflector may comprise a plurality of linearly extending
reflective elements oriented parallel to the linear focus of the
reflector and fixed in position with respect to each other and the
receiver, with the linearly extending reflective elements arranged
in two or more parallel side-by-side rows with each row including
two or more of the linearly extending reflective elements arranged
end-to-end. In such cases, the support structure may comprise a
plurality of separate longitudinal reflector supports each of which
has a long axis oriented parallel to the linear focus of the
reflector and each of which comprises a channel portion parallel to
its long axis, a first lip portion on one side of and parallel to
the channel portion, and a second lip portion parallel to and on an
opposite side of the channel portion from the first lip portion.
Each of the linearly extending reflective elements may be attached
to and supported by the lip portions, and bridge the channel
portion, of at least a corresponding one of the longitudinal
reflector supports. Each row of linearly extending reflective
elements may be supported by at least a first and a second of the
longitudinal reflector supports arranged end-to-end with an end
portion of the first longitudinal reflector support positioned
within a flared end of the channel portion of the second
longitudinal reflector support.
[0013] In another aspect, a concentrating solar energy collector
comprises a linearly extending reflector having a linear focus, a
linearly extending receiver oriented parallel to the linear focus
of the reflector and fixed in position with respect to the
reflector, a support structure supporting the reflector and the
receiver and pivotally mounted to accommodate rotation of the
support structure, the reflector, and the receiver about a rotation
axis parallel to the linear focus of the reflector, and a drive
system coupled to the support structure to rotate the support
structure, the reflector, and the receiver about the rotation axis.
The receiver comprises upper and lower surfaces on opposite sides
of the receiver, with the lower surface of the receiver located at
or approximately at the linear focus of the reflector and the upper
surface of the receiver comprising solar cells arranged to face the
sun when the solar energy collector (e.g., the reflector and the
receiver) is oriented to concentrate solar radiation on the lower
surface of the receiver. The solar cells of the upper surface of
the receiver generate sufficient electricity under a solar
irradiance of at least about 100 Watts per square meter (W/m.sup.2)
of solar cell, at least about 150 W/m.sup.2 of solar cell, at least
about 200 W/m.sup.2 of solar cell, at least about 250 W/m.sup.2 of
solar cell, at least about 300 W/m.sup.2 of solar cell, at least
about 350 W/m.sup.2 of solar cell, or at least about 400 W/m.sup.2
of solar cell to power the drive system.
[0014] The drive system powered by the solar cells on the upper
surface of the receiver may comprise, for example, one or more
motors, one or more drive shafts extending parallel to the rotation
axis and driven by the one or more motors, one or more linear
actuators driven by the one or more drive shafts and coupled to the
support structure to rotate the support structure, the reflector,
and the receiver about the rotation axis, and a controller that
controls the motor and/or actuators.
[0015] The rotation axis may extend, for example in an East-West or
approximately (e.g., substantially) East-West direction.
[0016] If the receiver comprises one or more coolant channels as
described above, the solar cells of the upper surface may
additionally, or alternatively, power one or more pumps that pump
fluid through the coolant channels. Alternatively, such pumps if
present may be powered by an energy source external to the solar
energy collector.
[0017] The reflector may comprise a plurality of linearly extending
reflective elements oriented parallel to the linear focus of the
reflector and fixed in position with respect to each other and the
receiver, with the linearly extending reflective elements arranged
in two or more parallel side-by-side rows with each row including
two or more of the linearly extending reflective elements arranged
end-to-end. In such cases, the support structure may comprise a
plurality of separate longitudinal reflector supports each of which
has a long axis oriented parallel to the linear focus of the
reflector and each of which comprises a channel portion parallel to
its long axis, a first lip portion on one side of and parallel to
the channel portion, and a second lip portion parallel to and on an
opposite side of the channel portion from the first lip portion.
Each of the linearly extending reflective elements may be attached
to and supported by the lip portions, and bridge the channel
portion, of at least a corresponding one of the longitudinal
reflector supports. Each row of linearly extending reflective
elements may be supported by at least a first and a second of the
longitudinal reflector supports arranged end-to-end with an end
portion of the first longitudinal reflector support positioned
within a flared end of the channel portion of the second
longitudinal reflector support.
[0018] In another aspect, a concentrating solar energy collector
comprises a linearly extending reflector having a linear focus, a
linearly extending receiver oriented parallel to and located at or
approximately at the linear focus of the reflector and fixed in
position with respect to the reflector, a support structure
supporting the reflector and the receiver and pivotally mounted at
a plurality of pivot points to accommodate rotation of the support
structure, the reflector, and the receiver about a rotation axis
parallel to the linear focus of the reflector, and a plurality of
linear actuators each of which is pivotally coupled to the support
structure near a corresponding one of the pivot points to rotate
the support structure, the reflector, and the receiver about its
corresponding one of the pivot points.
[0019] The solar energy collector may optionally comprise a drive
shaft extending parallel to the rotation axis and mechanically
coupled to the linear actuators to transmit rotational motion of
the drive shaft to drive the linear actuators. The linear actuators
may be pivotally coupled to the drive shaft, and the drive shaft
isolated from thrust loads on the linear actuators.
[0020] The receiver may comprise upper and lower surfaces on
opposite sides of the receiver, with the lower surface of the
receiver located at or approximately at the linear focus of the
reflector and the upper surface of the receiver comprising solar
cells arranged to face the sun when the solar energy collector
(e.g., the reflector and the receiver) is oriented to concentrate
solar radiation on the lower surface of the receiver. The solar
cells of the upper surface of the receiver may generate sufficient
electricity under a solar irradiance of at least about 100 Watts
per square meter (W/m.sup.2) of solar cell, at least about 150
W/m.sup.2 of solar cell, at least about 200 W/m.sup.2 of solar
cell, at least about 250 W/m.sup.2 of solar cell, at least about
300 W/m.sup.2 of solar cell, at least about 350 W/m.sup.2 of solar
cell, or at least about 400 W/m.sup.2 of solar cell to power a
drive system, including the linear actuators, coupled to the
support structure to rotate the support structure, the reflector,
and the receiver about the rotation axis. If the receiver comprises
one or more coolant channels as described above, the solar cells of
the upper surface may additionally, or alternatively, power one or
more pumps that pump fluid through the coolant channels.
[0021] The reflector may comprise a plurality of linearly extending
reflective elements oriented parallel to the linear focus of the
reflector and fixed in position with respect to each other and the
receiver, with the linearly extending reflective elements arranged
in two or more parallel side-by-side rows with each row including
two or more of the linearly extending reflective elements arranged
end-to-end. In such cases, the support structure may comprise a
plurality of separate longitudinal reflector supports each of which
has a long axis oriented parallel to the linear focus of the
reflector and each of which comprises a channel portion parallel to
its long axis, a first lip portion on one side of and parallel to
the channel portion, and a second lip portion parallel to and on an
opposite side of the channel portion from the first lip portion.
Each of the linearly extending reflective elements may be attached
to and supported by the lip portions, and bridge the channel
portion, of at least a corresponding one of the longitudinal
reflector supports. Each row of linearly extending reflective
elements may be supported by at least a first and a second of the
longitudinal reflector supports arranged end-to-end with an end
portion of the first longitudinal reflector support positioned
within a flared end of the channel portion of the second
longitudinal reflector support.
[0022] In another aspect, a concentrating solar energy collector
comprises a linearly extending reflector having a linear focus, a
linearly extending receiver oriented parallel to and located at or
approximately at the linear focus of the reflector and fixed in
position with respect to the reflector, a support structure
supporting the reflector and the receiver and pivotally mounted to
accommodate rotation of the support structure, the reflector, and
the receiver about a rotation axis parallel to the linear focus of
the reflector, a linear actuator extending transverse to the
rotation axis and pivotally coupled to the support structure to
rotate the support structure, the reflector, and the receiver about
the rotation axis, and a drive shaft extending parallel to the
rotation axis and mechanically coupled to the linear actuator to
transmit rotational motion of the drive shaft to drive the linear
actuator. The linear actuator may be pivotally coupled to the drive
shaft, and the drive shaft isolated from thrust loads on the linear
actuator.
[0023] The receiver may comprise upper and lower surfaces on
opposite sides of the receiver, with the lower surface of the
receiver located at or approximately at the linear focus of the
reflector and the upper surface of the receiver comprising solar
cells arranged to face the sun when the solar energy collector
(e.g., the reflector and the receiver) is oriented to concentrate
solar radiation on the lower surface of the receiver. The solar
cells of the upper surface of the receiver may generate sufficient
electricity under a solar irradiance of at least about 100 Watts
per square meter (W/m.sup.2) of solar cell, at least about 150
W/m.sup.2 of solar cell, at least about 200 W/m.sup.2 of solar
cell, at least about 250 W/m.sup.2 of solar cell, at least about
300 W/m.sup.2 of solar cell, at least about 350 W/m.sup.2 of solar
cell, or at least about 400 W/m.sup.2 of solar cell to power a
drive system, including the linear actuator, coupled to the support
structure to rotate the support structure, the reflector, and the
receiver about the rotation axis. If the receiver comprises one or
more coolant channels as described above, the solar cells of the
upper surface may additionally, or alternatively, power one or more
pumps that pump fluid through the coolant channels.
[0024] The reflector may comprise a plurality of linearly extending
reflective elements oriented parallel to the linear focus of the
reflector and fixed in position with respect to each other and the
receiver, with the linearly extending reflective elements arranged
in two or more parallel side-by-side rows with each row including
two or more of the linearly extending reflective elements arranged
end-to-end. In such cases, the support structure may comprise a
plurality of separate longitudinal reflector supports each of which
has a long axis oriented parallel to the linear focus of the
reflector and each of which comprises a channel portion parallel to
its long axis, a first lip portion on one side of and parallel to
the channel portion, and a second lip portion parallel to and on an
opposite side of the channel portion from the first lip portion.
Each of the linearly extending reflective elements may be attached
to and supported by the lip portions, and bridge the channel
portion, of at least a corresponding one of the longitudinal
reflector supports. Each row of linearly extending reflective
elements may be supported by at least a first and a second of the
longitudinal reflector supports arranged end-to-end with an end
portion of the first longitudinal reflector support positioned
within a flared end of the channel portion of the second
longitudinal reflector support.
[0025] In another aspect, a concentrating solar energy collector
comprises a linearly extending reflector having a linear focus, a
linearly extending receiver oriented parallel to and located at or
approximately at the linear focus of the reflector and fixed in
position with respect to the reflector, and a support structure
supporting the reflector and the receiver and pivotally mounted to
accommodate rotation of the support structure, the reflector, and
the receiver about a rotation axis parallel to the linear focus of
the reflector. The reflector comprises a plurality of linearly
extending reflective elements oriented parallel to the linear focus
of the reflector and fixed in position with respect to each other
and the receiver, with the linearly extending reflective elements
arranged in two or more parallel side-by-side rows with each row
including two or more of the linearly extending reflective elements
arranged end-to-end. The support structure comprises a plurality of
separate longitudinal reflector supports each of which has a long
axis oriented parallel to the linear focus of the reflector and
each of which comprises a channel portion parallel to its long
axis, a first lip portion on one side of and parallel to the
channel portion, and a second lip portion parallel to and on an
opposite side of the channel portion from the first lip portion.
Each linearly extending reflective element is attached to and
supported by the lip portions, and bridge the channel portion, of
at least a corresponding one of the longitudinal reflector
supports. Each row of linearly extending reflective elements is
supported by at least a first and a second of the longitudinal
reflector supports arranged end-to-end with an end portion of the
first longitudinal reflector support positioned within a flared end
of the channel portion of the second longitudinal reflector
support.
[0026] Optionally, in each row a single one of the linearly
extending reflective elements extends the length of the first
longitudinal reflector support except for its flared end, and
another single one of the linearly extending reflective elements
extends the length of the second longitudinal reflector support and
abuts an end of the linearly reflective element supported by the
first longitudinal reflector support. The ordering of the first and
second longitudinal reflector supports in adjacent rows may be
opposite, so that gaps or joints between the reflective elements in
one row are not next to gaps or joints between reflective elements
in an adjacent row.
[0027] In another aspect, a concentrating solar energy collector
comprises a linearly extending reflector having a linear focus and
a reflective surface that is or approximates a portion of a
parabolic surface from entirely on one side of a symmetry plane of
the parabolic surface, a linearly extending receiver oriented
parallel to and located at or approximately at the linear focus of
the reflector and fixed in position with respect to the reflector,
and a support structure supporting the reflector and the receiver
and pivotally mounted at a plurality of pivot points to accommodate
rotation of the support structure, the reflector, and the receiver
about a rotation axis parallel to the linear focus of the
reflector. The support structure comprises a plurality of
transverse reflector supports supporting the reflector and
extending transverse to the rotation axis, and a corresponding
plurality of receiver supports each connected to and extending
from, or approximately from, a single end of a corresponding
transverse reflector support to support the receiver above the
reflector. The solar energy collector also comprises a plurality of
linear actuators each of which is located near a corresponding one
of the pivot points and pivotally coupled to a corresponding one of
the transverse reflector supports to rotate the support structure,
the reflector, and the receiver about the linear actuator's
corresponding one of the pivot points, and a drive shaft extending
parallel to the rotation axis and mechanically coupled to the
linear actuators to transmit rotational motion of the drive shaft
to drive the linear actuators. The linear actuators are pivotally
coupled to the drive shaft, and the drive shaft is isolated from
thrust loads on the linear actuators. The rotation axis may be
oriented in an East-West or approximately East-West direction, for
example.
[0028] The receiver may comprise solar cells that, in operation of
the solar energy collector, are illuminated by solar radiation
concentrated by the reflector onto the receiver. The receiver may
additionally or alternatively comprise one or more coolant channels
through which, in operation of the solar energy collector, fluid
may pass to collect heat from solar radiation concentrated by the
reflector onto the receiver.
[0029] The receiver may comprise upper and lower surfaces on
opposite sides of the receiver, with the lower surface of the
receiver located at or approximately at the linear focus of the
reflector and the upper surface of the receiver comprising solar
cells arranged to face the sun when the solar energy collector
(e.g., the reflector and the receiver) is oriented to concentrate
solar radiation on the lower surface of the receiver. The solar
cells of the upper surface of the receiver may generate sufficient
electricity under a solar irradiance of at least about 100 Watts
per square meter (W/m.sup.2) of solar cell, at least about 150
W/m.sup.2 of solar cell, at least about 200 W/m.sup.2 of solar
cell, at least about 250 W/m.sup.2 of solar cell, at least about
300 W/m.sup.2 of solar cell, at least about 350 W/m.sup.2 of solar
cell, or at least about 400 W/m.sup.2 of solar cell to power a
drive system, including the linear actuators, coupled to the
support structure to rotate the support structure, the reflector,
and the receiver about the rotation axis. If the receiver comprises
one or more coolant channels as described above, the solar cells of
the upper surface may additionally, or alternatively, power one or
more pumps that pump fluid through the coolant channels.
[0030] The reflector may comprise a plurality of linearly extending
reflective elements oriented parallel to the linear focus of the
reflector and fixed in position with respect to each other and the
receiver, with the linearly extending reflective elements arranged
in two or more parallel side-by-side rows with each row including
two or more of the linearly extending reflective elements arranged
end-to-end. In such cases, the support structure may comprises a
plurality of separate longitudinal reflector supports each of which
has a long axis oriented parallel to the linear focus of the
reflector and each of which comprise a channel portion parallel to
its long axis, a first lip portion on one side of and parallel to
the channel portion, and a second lip portion parallel to and on an
opposite side of the channel portion from the first lip portion.
Each of the linearly extending reflective elements may be attached
to and supported by the lip portions, and bridge the channel
portion, of at least a corresponding one of the longitudinal
reflector supports. Each row of linearly extending reflective
elements may be supported by at least a first and a second of the
longitudinal reflector supports arranged end-to-end with an end
portion of the first longitudinal reflector support positioned
within a flared end of the channel portion of the second
longitudinal reflector support.
[0031] In another aspect, a concentrating solar energy collector
comprises a linearly extending reflector having a linear focus, a
linearly extending receiver oriented parallel to and located at or
approximately at the linear focus of the reflector and fixed in
position with respect to the reflector, a support structure
supporting the reflector and the receiver and pivotally mounted to
accommodate rotation of the support structure, the reflector, and
the receiver about a rotation axis parallel to the linear focus of
the reflector, and a first solar radiation sensor that, when
illuminated by solar radiation concentrated by the reflector,
generates a signal by which rotation of the support structure, the
reflector, and the receiver may be controlled to maximize
concentration of solar radiation onto the receiver. The first solar
radiation sensor may be located, for example, in a focal region of
the reflector.
[0032] The first solar radiation sensor may optionally comprises
two solar radiation detectors positioned on opposite sides of a
center line of the linear focus of the reflector, each of which is
optionally elongated in a direction transverse to the linear focus
of the reflector.
[0033] The solar energy collector may also comprise a second solar
radiation sensor positioned to be illuminated directly by solar
radiation not concentrated by the reflector. The second solar
radiation sensor may generate a signal by which rotation of the
support structure, the reflector, and the receiver may be
controlled to illuminate the first solar radiation sensor with
solar radiation concentrated by the reflector. The second solar
radiation sensor may, for example, be fixed in position with
respect to reflector and the receiver and located in a plane
oriented perpendicular to an optical axis of the reflector.
[0034] The second solar radiation sensor may comprise, for example,
a linearly elongated gnomon and two linearly elongated solar
radiation detectors positioned on opposite sides of the gnomon,
with the long axes of the gnomon and the linearly elongated solar
radiation detectors arranged parallel to the linear focus of the
reflector.
[0035] In another aspect, a method of collecting solar energy
comprises orienting a concentrator to maximize or substantially
maximize concentration of solar radiation onto a receiver through
which a fluid is flowed to collect heat, thereby shading a surface
underlying the concentrator from direct solar radiation. The method
further comprises reorienting the concentrator to reduce the amount
of solar radiation concentrated on the receiver, while maintaining
significant shading of the surface underlying the concentrator,
when a temperature of the fluid exceeds a predetermined value.
[0036] The reoriented concentrator may block, for example, at least
about 70%, about 80%, about 90%, or about 95% of the amount of
solar radiation that the concentrator would block if oriented to
maximize concentration of solar radiation onto the receiver. The
predetermined temperature may be, for example, at least about
70.degree. C., about 75.degree. C. about 80.degree. C., about
85.degree. C., about 90.degree. C., or about 95.degree. C.
[0037] These and other embodiments, features and advantages of the
present invention will become more apparent to those skilled in the
art when taken with reference to the following more detailed
description of the invention in conjunction with the accompanying
drawings that are first briefly described.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIGS. 1A-1C show an example solar energy collector.
[0039] FIG. 2 shows a graph of a parabolic surface and its symmetry
plane, by which features of some solar energy collectors disclosed
herein may be better understood.
[0040] FIGS. 3A-3D show perspective (3A), side (3B), and end (3C,
3D) views of examples of a linearly extending reflective element
attached to and supported by a longitudinal reflector support; FIG.
3E shows an end view of linearly extending reflective elements
attached to and supported by a portion of another example
longitudinal reflector support, FIGS. 3F and 3G show perspective
views of reflectors attached to additional example longitudinal
reflector supports, FIG. 3H shows a cross-sectional view of the
longitudinal reflector supports of FIGS. 3F and 3G.
[0041] FIG. 4A shows a side view of the example solar energy
collector of FIGS. 1A-1C, absent its reflector, including details
of a transverse reflector support; FIG. 4B shows the portion of the
example longitudinal transverse reflector support of FIG. 3E
supported by a portion of a transverse reflector support as shown,
for example, in FIG. 4A, FIG. 4C shows a top view of
reflector/longitudinal reflector support assemblies of FIGS. 3F and
3G attached to transverse reflector supports.
[0042] FIGS. 5A-5C show an example arrangement for mounting a
portion of a reflector-receiver arrangement (e.g., module) of a
solar energy collector on a rotation shaft.
[0043] FIGS. 6A and 6B show an example solar energy collector
comprising three reflector-receiver modules sharing a rotation
shaft.
[0044] FIGS. 7A and 7B show an example of three solar energy
collectors ganged to be driven by a single actuator.
[0045] FIGS. 8A-8B show another example solar energy collector.
[0046] FIG. 9 shows an example arrangement of a transverse
reflector support and a receiver support used in the example solar
energy collector of FIGS. 8A, 8B, 11A, and 11B.
[0047] FIGS. 10A-10C show the example solar energy collector of
FIGS. 8A and 8B oriented to concentrate solar radiation onto its
receiver when the sun is directly overhead (10A), at -5 degrees
from the vertical (in the direction of the earth's equator), and at
+60 degrees from the vertical (away from the equator).
[0048] FIGS. 11A-11B show another example solar energy
collector.
[0049] FIGS. 12A-12C show the example solar energy collector of
FIGS. 11A and 11B oriented to concentrate solar radiation when the
sun is directly overhead (10A), at -5 degrees from the vertical (in
the direction of the earth's equator), and at +60 degrees from the
vertical (away from the equator).
[0050] FIG. 13 shows another example solar energy collector.
[0051] FIGS. 14A-14B show the example solar energy collector of
FIG. 13 oriented to concentrate solar radiation onto its receiver
when the sun is at -15 degrees from the vertical (in the direction
of the earth's equator), and at +65 degrees from the vertical (away
from the equator).
[0052] FIGS. 15a and 15b show, respectively, example solar energy
collectors comprising five and six of the solar energy collectors
of FIG. 13.
[0053] FIGS. 16A-16C show perspective, exploded, and
cross-sectional views of an example gear assembly that may be used
to drive linear actuators in some example solar energy collectors
disclosed herein.
[0054] FIG. 17 shows a portion of an example solar energy collector
comprising the example gear assembly of FIGS. 16A-16C.
[0055] FIGS. 18A-18B show example arrangements of sun sensors that
may be used to control the orientation of some example solar energy
collectors disclosed herein.
[0056] FIGS. 19A-19B show example reflective elements (e.g.,
mirrors) having laminated structures.
DETAILED DESCRIPTION
[0057] The following detailed description should be read with
reference to the drawings, in which identical reference numbers
refer to like elements throughout the different figures. The
drawings, which are not necessarily to scale, depict selective
embodiments and are not intended to limit the scope of the
invention. The detailed description illustrates by way of example,
not by way of limitation, the principles of the invention. This
description will clearly enable one skilled in the art to make and
use the invention, and describes several embodiments, adaptations,
variations, alternatives and uses of the invention, including what
is presently believed to be the best mode of carrying out the
invention.
[0058] As used in this specification and the appended claims, the
singular forms "a," "an," and "the" include plural referents unless
the context clearly indicates otherwise. Also, the term "parallel"
is intended to mean "substantially parallel" and to encompass minor
deviations from parallel geometries rather than to require that
parallel rows of reflectors, for example, or any other parallel
arrangements described herein be exactly parallel.
[0059] This specification discloses apparatus, systems, and methods
by which solar energy may be collected to provide electricity,
heat, or a combination of electricity and heat. Solar energy
collectors as disclosed herein may be used, for example, in some
variations of the methods, apparatus, and systems disclosed in U.S.
patent application Ser. No. 12/788,048, filed May 26, 2010, titled
"Concentrating Solar Photovoltaic-Thermal System," incorporated
herein by reference in its entirety.
[0060] Referring now to FIGS. 1A-1C, an example solar energy
collector 100 comprises a linearly extending reflector 120, a
linearly extending receiver 110 comprising a surface 112 located at
or approximately at the linear focus of the reflector and fixed in
position with respect to the reflector, and a support structure 130
supporting the reflector and the receiver and pivotally mounted to
accommodate rotation of the support structure, the reflector, and
the receiver about a rotation axis 140 parallel to the linear focus
of the reflector. In use, the support structure, reflector, and
receiver are rotated about rotation axis 140 to track the sun such
that solar radiation incident on reflector 120 is concentrated onto
receiver 110, i.e., such that the optical axes of reflector 120 are
directed at the sun. (Any path perpendicular to the linear focus of
reflector 120 for which light rays traveling along that path are
focused by the reflector onto the centerline of the receiver is an
optical axis of reflector 120 and collector 100).
[0061] In the illustrated example, the reflective surface of
reflector 120 is or approximates a portion of a parabolic surface.
Referring now to the graph in FIG. 2, a parabolic surface 132 may
be constructed mathematically (in a coordinate space spanned by
axes x, y, z, as shown, for example) by translating a parabola 134
along an axis 136 (in this example, the y axis) perpendicular to
the plane of the parabola (in this example, the x, z plane).
Symmetry plane 137 (the y, z plane in this example) divides
parabolic surface 132 into two symmetric halves 132a, 132b. The
linear focus 138 of the parabolic surface is oriented perpendicular
to the plane of the parabola and lies in symmetry plane 137 at a
distance F (the focal length) from the parabolic surface. For
parabolic reflective surfaces as in this example, the optical axes
are in the symmetry plane of the surface and oriented
perpendicularly to the linear focus of the surface. In this
example, the z axis is an optical axis of the reflector.
[0062] Referring again to FIGS. 1A-1C, in the illustrated example
the reflective surface of reflector 120 is or approximates a
portion of a parabolic surface taken entirely from one side of the
symmetry plane of the parabolic surface (e.g., from 132a or 132b in
FIG. 2, but not both). In other variations, the reflective surface
of reflector 120 is or approximates a portion of a parabolic
surface taken from primarily one side of the symmetry plane of the
parabolic surface (e.g., more than 50%, more than 60%, more than
70%, more than 80%, more than 90%, or more than 95% of the
reflective surface is from one side of the symmetry plane of the
parabolic surface), but includes a portion of the parabolic surface
on the other side of the symmetry plane, as well.
[0063] Although reflector 120 is parabolic or approximately
parabolic in the illustrated example, reflector 120 need not have a
parabolic or approximately parabolic reflective surface. In other
variations of solar energy collectors disclosed herein, reflector
120 may have any curvature suitable for concentrating solar
radiation onto a receiver.
[0064] In the illustrated example, reflector 120 comprises a
plurality of linearly extending reflective elements 150 (e.g.,
mirrors) oriented parallel to the rotation axis and fixed in
position with respect to each other and with respect to the
receiver. Linear reflective elements 150 may each have a length
equal or approximately equal to that of reflector 120, in which
case they may be arranged side-by-side to form reflector 120.
(Reflector 120 may have a length, for example, of about 5 meters to
about 12 meters, in some variations about 11.2 meters, in some
variations about 6 meters). Alternatively, some or all of linear
reflective elements 150 may be shorter than the length of reflector
120, in which case two or more linearly extending reflective
elements 150 may be arranged end-to-end to form a row along the
length of the reflector, and two or more such rows may be arranged
side-by-side to form reflector 120.
[0065] Linearly extending reflective elements 150 may each have a
width, for example, of about 8 centimeters to about 15 centimeters,
and a length, for example, of about 1.2 meters to about 3.2 meters.
In some variations, some or all of reflective elements 150 have a
width of about 10.7 centimeters. In some variations, some or all of
reflective elements 150 have a width of about 13.2 centimeters. The
widths of reflective elements 150 may vary with position in
reflector 120. For example, in some variations reflective elements
150 located further away from receiver 110 are wider than
reflective elements 150 located closer to receiver 110 (see, e.g.,
FIG. 15B described below). Reflective elements 150 may be flat,
substantially flat, or curved (e.g., along a direction transverse
to their long axes to focus incident solar radiation).
[0066] Although in the illustrated example reflector 120 comprises
linearly extending reflective elements 150, in other variations
reflector 120 may be formed from a single continuous reflective
element, from two or more reflective elements with a width
perpendicular to the rotation axis greater than their length along
the rotation axis, or in any other suitable manner.
[0067] Linearly extending reflective elements 150, or other
reflective elements used to form a reflector 120, may be or
comprise, for example, any suitable front surface mirror or rear
surface mirror. The reflective properties of the mirror may result,
for example, from any suitable metallic or dielectric coating or
polished metal surface. Some variations may utilize a mirror having
a laminated structure as described later in this specification.
Some other variations may utilize a rear surface mirror formed with
low-iron glass having a thickness of about 3 to about 4
millimeters.
[0068] Receiver 110 may comprise solar cells (not shown) located,
for example, on receiver surface 112 to be illuminated by solar
radiation concentrated by reflector 120. In such variations,
receiver 110 may further comprise one or more coolant channels
accommodating flow of liquid coolant in thermal contact with the
solar cells. For example, liquid coolant (e.g., water, ethylene
glycol, or a mixture of the two) may be introduced into and removed
from receiver 110 through manifolds (not shown) at either end of
the receiver located, for example, on a rear surface of the
receiver shaded from concentrated radiation. Coolant introduced at
one end of the receiver may pass, for example, through one or more
coolant channels (not shown) to the other end of the receiver from
which the coolant may be withdrawn. This may allow the receiver to
produce electricity more efficiently (by cooling the solar cells)
and to capture heat (in the coolant). Both the electricity and the
captured heat may be of commercial value.
[0069] FIGS. 1A and 1B also show optional coolant storage tank 115,
pump 117, and controller 120. Coolant may be stored in tank 115 and
pumped by pump 117 from tank 115 to receiver 110 (through coolant
conduits, e.g., not shown), through receiver 110, and back to tank
115. Pump 115 may be controlled by controller 120 based, for
example, on temperature measurements of coolant entering and/or
leaving receiver 110.
[0070] In some variations, the receiver comprises solar cells but
lacks channels through which a liquid coolant may be flowed. In
other variations, the receiver may comprise channels accommodating
flow of a liquid to be heated by solar energy concentrated on the
receiver, but lack solar cells.
[0071] Solar energy collector 100 may comprise any suitable
receiver. In addition to the examples illustrated herein, suitable
receivers may include, for example, those disclosed in U.S. patent
application Ser. No. 12/622,416, filed Nov. 19, 2009, titled
"Receiver For Concentrating Photovoltaic-Thermal System;" and U.S.
patent application Ser. No. 12/774,436, filed May 5, 2010, also
titled "Receiver For Concentrating Photovoltaic-Thermal System;"
both of which are incorporated herein by reference in their
entirety.
[0072] In some variations, receiver 110 is the same length, or
approximately the same length, as reflector 120 and centered
length-wise over reflector 120 (e.g., the examples of FIGS. 8A and
11A). In some variations, receiver 110 is shorter than reflector
120 and centered length-wise over reflector 120 (e.g., the examples
of FIGS. 6A and 6B). In some variations receiver 110 is the same
length, or approximately the same length, as reflector 120 and
positioned length-wise with respect to reflector 120 such that one
end of receiver 110 extends beyond a corresponding end of reflector
120 (not shown). In some variations, receiver 110 is shorter than
reflector 120, and positioned with one end approximately in line
with a corresponding end of reflector 120 (not shown). In the
latter variations, the other end of receiver 110 does not extend to
the other end of reflector 120.
[0073] In some variations, surface 112 of receiver 110 is tilted to
face reflector 120. In the illustrated example, the reflective
surface of reflector 120 is or approximates a portion of a
parabolic surface, and receiver surface 112 is tilted away from an
orientation that would make it perpendicular to the symmetry plane
of that parabolic surface by about 45 degrees. In other variations,
surface 112 may be tilted, for example, at an angle of about 30
degrees to about 60 degrees from an orientation perpendicular to
the symmetry plane. Surface 112 may also be tilted to face
reflector 120 in variations in which reflector 120 is not parabolic
or approximately parabolic. In the illustrated example, the
periphery (edges) of surface 112 defines the optical aperture of
receiver 110. In some variations, receiver 110 may absorb solar
radiation on an internal surface, after the solar radiation passes
through an optical aperture of the receiver. In such variations,
the optical aperture of receiver 110 (though not defined by an
external surface as in the illustrated example) may be tilted to
face reflector 120 as just described for surface 112.
[0074] In some variations, support structure 130 supports receiver
110 above and off-center of reflector 120. In the illustrated
example, the reflective surface of reflector 120 is or approximates
a portion of a parabolic surface, and receiver 110 is located
closer to the edge of reflector 120 nearest the symmetry plane of
the parabolic surface. In other variations, receiver 110 may be
supported above reflector 120 in a different location.
[0075] In some variations, in use, the receiver is illuminated by
concentrated solar radiation that under-fills the receiver. For
example, more than about 80%, more than about 85%, more than about
90%, or more than about 95% of the energy of the concentrated solar
radiation may be incident on the receiver in a region having a
width (transverse to the long axis of the receiver) that is about
75%, about 80%, about 85%, about 90%, or about 95% of the overall
width of the receiver (or of that portion of the receiver
comprising solar cells). In some variations at least about 90%, or
at least about 95% of the solar energy incident on the solar cells
is concentrated on a central portion of the linear array of solar
cells having a width, perpendicular to the long axis of the array
of solar cells, of less than about 80% of the corresponding width
of the linear array of solar cells. Under-filling the receiver in
this manner may increase the efficiency with which concentrated
solar radiation is collected and converted to useful electricity or
heat.
[0076] Such under-filling may be accomplished, for example, by
selecting the width of linearly extending reflective elements 150
(and their transverse curvature, if they are not flat or
substantially flat) to provide the desired concentrated solar
radiation intensity distribution on the illuminated receiver
surface.
[0077] Referring again to FIGS. 1A-1C, in the illustrated example
support structure 130 comprises a plurality of transverse reflector
supports 155 supporting the reflector and extending transverse to
rotation axis 140 and/or to a long axis of the reflector, and a
plurality of receiver supports 160 each connected to and extending
from an end, or approximately an end, of a transverse reflector
support to support the receiver over the reflector. In the
illustrated example, a single unitary support structure comprises a
transverse reflector support 155 portion and a receiver support
portion 160. In other variations, including examples described
later in this specification (e.g., FIGS. 8A-15B), a transverse
reflector support and a receiver support may be separate pieces
attached to each other at, or approximately at, an end of the
transverse reflector support. In yet other variations, any other
suitable structure may be used to support the reflector and the
receiver.
[0078] In the illustrated example, transverse reflector supports
155 in combination with receiver supports 160 form "C" shapes. In
other variations, transverse reflector supports 155 in combination
with receiver supports 160 may form, for example, "V" shapes, "L"
shapes, or any other suitable geometry.
[0079] In the illustrated example, transverse reflector supports
155 are attached to a shaft 165 (also shown separately in FIG. 5C)
pivotally supported by bearings on support posts 170. Support posts
170 support the shaft 165 and other components of support structure
130 above a base 175. Base 175 may be installed, for example, at
ground level, on a rooftop, or in any other suitable location. Base
175 is optional. For example, in some variations posts 170 may
directly support components of support structure 130 at or above
ground level or on a rooftop, for example.
[0080] In the illustrated example, rotation axis 140 is coincident
with shaft 165, which is located approximately under and parallel
to an edge of reflector 120 nearest receiver 110. In some
variations, the reflective surface of reflector 120 is or
approximates a portion of a parabolic surface, and rotation axis
140 lies in the symmetry plane of the parabolic surface. In other
variations, rotation axis 140 may be located elsewhere.
[0081] In the illustrated example, a linear actuator 180 comprising
an extensible shaft 182 is mechanically coupled between a pivotal
connector 184 on base 175 and a pivotal connector 186 on a
vertically extending lever arm 188 attached to shaft 165. Linear
actuator 180 may rotate shaft 165 (and hence reflector 120 and
receiver 110) around rotation axis 140 to track the motion of the
sun by extending or retracting extensible shaft 182. In the absence
of base 175, linear actuator 180 may be coupled, for example, to a
pivotal connector on or attached to the ground, a rooftop, or a
separate support structure. In some variations, linear actuator 180
may be controlled, for example, by a locally positioned controller
such as controller 120 shown in FIGS. 1A and 1B.
[0082] Other variations, some of which are described below (e.g.,
FIGS. 8A-17), may utilize a differently positioned linear actuator
to rotate reflector 120 and receiver 110 around rotation axis 140.
In some variations described below (e.g., FIGS. 13-17), the linear
actuators are or comprise lead screws driven by a shared drive
shaft to rotate reflector 120 and receiver 110 around rotation axis
140. Any other suitable actuators or mechanisms and mounting
arrangements that allow receiver 110, reflector 120, and support
structure 130 to be rotated around a rotation axis parallel to a
linear focus of reflector 120 to track the sun may also be
used.
[0083] Solar energy collector 100 as illustrated, and its
variations as described throughout this specification, may be
arranged with rotation axis 140 oriented in an East-West, or
approximately East-West, direction. The solar energy collector may
be positioned with the receiver side of reflector 120 positioned
closest to the earth's equator or, in other variations, with the
receiver side of reflector 120 positioned away from the equator and
closest to the earth's (North or South, depending on hemisphere)
pole.
[0084] In such East-West orientations, the daily motion of the sun
in the sky may require a rotation of reflector 120 and receiver 110
around rotation axis 140 of, for example, less than about 90
degrees (e.g., less than about 70 degrees) to collect a valuable
quantity of incident solar radiation during the course of a day. A
rotation mechanism utilizing a linear actuator as illustrated, for
example, may effectively and inexpensively accomplish such a range
of motion. Utilizing a reflective surface that is or approximates a
portion of a parabolic surface taken entirely or primarily from one
side of the symmetry plane of the parabolic surface may provide a
compact reflector that may be rotated about a rotation axis located
close to supporting surfaces, particularly in variations in which
the rotation axis is near an edge of the reflector.
[0085] As described in more detail below, support structure 130 may
comprise longitudinal reflector supports each of which has a long
axis oriented parallel to the rotation axis 140 and each of which
supports a linearly extending reflective element 150, or a single
row of linearly extending reflective elements 150 arranged
end-to-end. The linearly extending reflective element or elements
may be attached, for example, to an upper surface of the
longitudinal reflector support. Transverse reflector supports 155,
if present, may support such longitudinal reflector supports,
directly support mirrors or other reflective elements, or support
some other intermediate structure that in turn supports mirrors or
other reflective elements.
[0086] Referring now to FIGS. 3A (perspective view), 3B (side
view), and 3C (end or cross-sectional view), an example
longitudinal reflector support 250 comprises a channel portion 255
parallel to its long axis, a first planar lip portion 260a on one
side of and parallel to channel portion 255, and a second planar
lip portion 260b parallel to and on an opposite side of channel
portion 255 from the first lip portion 260a. Linearly extending
reflective elements 150 are attached to and supported by lip
portions 260a, 260b, and bridge channel portion 255, of
longitudinal reflector support 250. In other variations, lip
portions 260a and 260b need not be planar, as illustrated. Any
suitable profile or shape for lip portions 260a, 260b may be
used.
[0087] In the example illustrated in FIGS. 3A-3C, linearly
extending reflective elements 150 are attached to lip portions
260a, 260b by adhesive or glue pads 265. The adhesive or glue pads
may be spaced, for example, at intervals of about 0.2 meters under
the reflective elements. In some other variations, linearly
extending reflective elements 150 are attached to longitudinal
reflector supports with a silicone adhesive such as, for example,
DOW Corning.RTM. 995 Silicone Structural Sealant. Any other
suitable method of attaching the reflective elements to the
longitudinal reflector support may be used, including other
adhesives or glues deployed in any other suitable manner, screws,
bolts, rivets and other similar mechanical fasteners, and clamps or
spring clips.
[0088] In the illustrated example, longitudinal reflector support
250 is about 11.2 meters long, channel portion 255 extends the
length of longitudinal reflector support 250 and is about 10.5
centimeters wide and about 3.5 centimeters deep, and lip portions
260a and 260b extend the length of longitudinal reflector support
250 and are about 2.0 centimeters wide. Linearly extending
reflective elements 150 are about 10.7 centimeters wide in this
example. In the example illustrated in FIGS. 1A-1C, each linearly
extending reflective element is as long as reflector 120. In other
variations (e.g., the examples of FIGS. 3B, 8A, and 11A further
described below), two or more linearly extending reflective
elements are attached end-to-end along a longitudinal reflector
support with, for example, a spacing of about 1 millimeter between
reflective elements.
[0089] Individual longitudinal reflector supports as disclosed
herein may extend the length of the reflector. Alternatively, some
or all of the longitudinal reflector supports may be shorter than
the overall length of the reflector, in which case two or more
longitudinal reflector supports may be arranged end-to-end to form
a row along the length of the reflector. Longitudinal reflector
supports may have lengths that allow them, for example, to be
easily handled by an individual person and/or easily transported
to, for example, a roof top on which a solar energy collector is
being assembled. Longitudinal reflector supports may have lengths,
for example, of about 1.0 meters to about 3 meters, about 1 meters
to about 5 meters, about 1 meters to about 12.0 meters, about 3.0
meters to about 5.0 meters, about 3 meters to about 12 meters,
about 5 meters to about 12 meters, about 2.8 meters, about 3.2
meters, and about 6.0 meters. Channel portions 255 may be, for
example, about 8 centimeters to about 15 centimeters wide and about
2.0 centimeters to about 8.0 centimeters deep. Lip portions 260a,
260b may be, for example, about 1.0 centimeters to about 4.0
centimeters wide.
[0090] Referring now to FIG. 3D, in another example a longitudinal
reflector support 265 is substantially similar to longitudinal
reflector support 250 just described, except that longitudinal
reflector support 265 further comprises slot portions 270a, 270b at
the ends of lip portions 260a, 260b. In this example, linearly
extending reflective elements 150 may be loaded onto longitudinal
reflector support 265 by sliding the reflective elements in from
the end of the reflector support. Slot portions 270a, 270b help
maintain linearly extending reflective elements 150 in position.
Adhesives, glues, clamps, or mechanical fasteners, for example, may
be used to further secure the reflective elements to the reflector
supports.
[0091] In the examples illustrated in FIGS. 3A-3D, the longitudinal
reflector supports 250, 265 are trough shaped with a cross section
having a flat-bottomed "U" shape. In other variations, the
longitudinal reflector supports may be trough shaped with, for
example, a rounded bottom "U" shape cross-section, a "V" shape
cross-section, or an upside-down .OMEGA. (Greek letter Omega)
cross-section. In other variations, the longitudinal reflector
support may comprise multiple channel portions (e.g., 2, 3, or more
than 3), side-by-side in parallel, between lip portions 260a and
260b. In such variations, the longitudinal reflector support may
have, for example, a W shaped cross section or a cross-section that
may be viewed as composed of multiple V or U shapes
side-by-side.
[0092] Referring now to FIG. 3E (end or cross-sectional view),
another example longitudinal reflector support 275 has the form of
a corrugated sheet of material (e.g. a corrugated sheet of metal)
comprising troughs 277 and crests 279. Longitudinal reflector
support 275 supports two or more parallel rows of reflective
elements 150. Reflective elements 150 may be attached to crests 279
with glue pads 265, for example. Each row of reflective elements
150 may comprise a plurality of reflective elements arranged
end-to-end (e.g., as described above), or a single reflective
element extending the length of longitudinal reflector support 275.
In solar energy collectors 100 as described herein, a longitudinal
reflector support 275 may be substituted, for example, for two or
more longitudinal reflector supports 250 or 265 supporting an
equivalent total number of rows of reflective elements 150.
Longitudinal reflector supports 275 may have lengths similar or the
same as longitudinal reflector supports 250 and 265. The depth and
width of troughs 270 may be similar or equivalent to corresponding
dimensions in longitudinal reflector supports 250 and 265.
[0093] Longitudinal reflector support 275 may comprise sufficient
troughs 277 and crests 279 to support all rows of reflective
elements 155 in a particular solar energy collector 100.
Alternatively, a solar energy collector 100 may comprise two or
more longitudinal reflector supports 275. In the latter case,
different longitudinal reflector supports 275 may have troughs and
crests dimensioned to accommodate linear reflective elements of
different widths. A single longitudinal reflector support 275 may,
in some variations, include troughs of two or more sizes and crests
of two or more sizes to accommodate linear reflective elements of
two or more different widths.
[0094] Referring now to FIGS. 3F-3H, some variations comprise one
or more longitudinal reflector supports 280 differing from those
described so far. Longitudinal reflector support 280 comprises a
channel portion 255 and lip portions 260a, 260b similar to
previously described variations. However, longitudinal reflector
support 280 differs from previously described variations in that at
one end 281a the channel portion 255 is flared outward compared to
its dimensions along the rest of its length and at its other end
281b. One or more linearly extending reflective elements 155 are
attached to longitudinal reflector support 280 similarly to as
described above for other variations, except that flared end
portion 281a is left uncovered by the reflective elements. As
further described below with reference to FIG. 4C, two or more such
assemblies of longitudinal reflector support 280 and reflective
elements 155 may be arranged end to end with unflared end portions
281b of longitudinal support structures 280 positioned within
flared end portions 281a of adjacent longitudinal reflector
supports 280. The flared 281a and unflared 281b end portions of
channels 255 may be dimensioned so that the outer surface of an
unflared end portion 281b fits closely within the inner surface of
a flared end 281a to allow for easy mechanical coupling of adjacent
in-line longitudinal reflector supports. In such an arrangement,
the edges of linearly extending reflective elements 155 supported
by adjacent in-line longitudinal supports 280 may abut (with an
optional gap, for example, of about 1 millimeter) to form a
substantially continuous reflective surface.
[0095] Such variations may further include a longitudinal reflector
support 282 having the same general configuration as longitudinal
reflector support 280, except that both of its ends 281b are
unflared and one or more linearly extending reflective elements 155
extend its full length. Either end 281b of longitudinal reflector
support 282 may be positioned within the flared end portion 281a of
an adjacent in-line longitudinal reflector support 280. A row of
longitudinal reflector supports may thus include, for example, one
or more longitudinal reflector supports 280 arranged end-to-end
followed by one longitudinal reflector support 282 ending the row
(see, e.g., FIG. 4C).
[0096] Longitudinal reflector supports 280, 282 may have lengths
similar or the same as longitudinal reflector supports 250 and 265
described above. The depth and width of channel portions 255 of
longitudinal reflector supports 280, 282 may be similar or
equivalent to corresponding dimensions in longitudinal reflector
supports 250 and 265. Longitudinal reflector supports 280 and 282
as used in the same collector may be of the same length or of
different lengths.
[0097] Longitudinal reflector supports may be formed, in some
variations, from sheet steel, sheet aluminum, or other sheet
metals. In some variations, the lips and channel portion (and slot
portions, if present) of a longitudinal reflector support as
illustrated in FIGS. 3A-3D and 3F-3H, for example, may be rolled,
folded, or otherwise formed from a continuous piece of sheet metal.
In some variations, the corrugated structure (e.g., troughs and
crests) of a longitudinal reflector support as illustrated in FIG.
3E, for example, may be rolled, folded, or otherwise formed from a
continuous piece of sheet metal. In some variations, longitudinal
reflector supports as illustrated are formed from a continuous
sheet of steel having a thickness of about 1 millimeter.
[0098] Longitudinal reflector supports as disclosed herein may also
be utilized as suitable in any other solar energy collectors. For
example, longitudinal reflector supports as disclosed herein may be
used in solar energy collectors as disclosed in U.S. patent
application Ser. No. 12/781,706, filed May 17, 2010, and titled
"Concentrating Solar Energy Collector," which is incorporated
herein by reference in its entirety.
[0099] As noted above, support structure 130 may comprise a
plurality of transverse reflector supports that extend away from
the rotational axis 140 and directly support mirrors or other
reflective elements or, alternatively, support mirrors or
reflective elements via longitudinal reflector supports as
disclosed herein or via any other suitable additional reflector
support structure.
[0100] Referring now to FIGS. 1A-1C, and particularly to FIGS.
4A-4C, in the illustrated example transverse reflector supports 155
in solar energy collector 100 each comprise a notched edge 285.
Portions of surfaces 300 adjacent to the notches in transverse
reflector supports 155 may be cut to define desired orientations of
linearly extending reflective elements to be supported by the
transverse reflector supports. Each notch in an upper surface of a
transverse reflector support 155 (e.g., FIGS. 4A-4C) corresponds to
a separate row of one or more longitudinal reflector supports
(e.g., 250, 265, 280, 282; FIGS. 3A-3D, 3F-3H) or to a separate
trough 277 or row of troughs 277 in one or more longitudinal
reflector supports 275. Each notch in a transverse reflector
support 155 is aligned with a similarly or identically placed notch
(corresponding to the same row of longitudinal reflector supports
or troughs) in the other transverse reflector support (or supports)
in solar energy collector 100. The channel portions 255 of the
longitudinal reflector supports 250, 265, 280, 282 (or the troughs
277 in longitudinal reflector supports 275) are positioned in
corresponding notches of the transverse reflector supports 155. The
lip portions 260a, 260b of the longitudinal reflector supports 250,
265, 280, 282 (or the crests 279 of the longitudinal reflector
supports 275) are then in contact with and supported by portions of
surfaces 300 of the transverse reflector supports adjacent to the
corresponding notches. Surfaces 300 may orient the longitudinal
reflector supports, and thus the linearly extending reflective
elements 150 they support, in a desired orientation with respect to
receiver 110 with a precision of about 0.5 degrees, for example, or
better (i.e., tolerance less than about 0.5 degrees). In other
variations, this tolerance may be, for example, greater than about
0.5 degrees.
[0101] In the example of FIG. 4C, each longitudinal reflector
support 280 or 282 supports a single linearly extending reflective
element 155, reflective elements supported by longitudinal
reflector supports 282 are longer than those supported by
longitudinal reflector supports 280, and the ordering of
longitudinal reflector supports 280 and 282 reverses in adjacent
rows. As a consequence, gaps or joints 375 between the reflective
elements in one row are not next to gaps or joints between
reflective elements in an adjacent row. Such staggering of gaps or
joints 375 may produce a more uniform illumination of the receiver
by solar radiation concentrated by reflector 120 than would occur
if such gaps or joints were generally next to gaps or joints in
adjacent rows, because in the latter case such gaps or joints might
cast shadows that were superimposed on each other on the receiver.
Staggering of gaps or joints 375, or of ends of rows of linearly
extending reflective elements 155, is further described at several
points below.
[0102] Longitudinal reflector supports (e.g., 250, 265, 275, 280,
282) may be attached to transverse reflector supports 155 or to
other portions of support structure 130, for example, by welding,
gluing, or use of any suitable clamp, screw, bolt, rivet or other
mechanical fastener. In some variations, the longitudinal reflector
supports are clamped at their ends (e.g., only at their ends) to
another portion of support structure 130.
[0103] As noted above, in the example illustrated in FIGS. 1A-1C
and FIG. 4A, a single unitary piece comprises a transverse
reflector support 155 and a receiver support 160. In such
variations, the unitary piece may be formed, for example, from
continuous metal (e.g., steel, aluminum) sheets or plates into
which the notches are cut or otherwise formed. The transverse
reflector supports may be similarly fabricated in other variations
(e.g., FIGS. 8A-15B) in which the transverse reflector support and
receiver support are not parts of a unitary piece.
[0104] Although particular examples of longitudinal reflector
supports and transverse reflector supports are illustrated and
described herein, any other suitable reflector supports may be used
in combination with the other elements of the solar energy
collectors disclosed herein.
[0105] FIGS. 5A-5C show an example arrangement for pivotally
mounting a portion of a reflector-receiver arrangement (e.g., a
module) to a rotation shaft. In the illustrated example,
longitudinal support bracket 305 extends parallel to the linear
focus of reflector 120 between transverse reflector supports 155,
to which it is attached. Longitudinal support bracket 305 has, for
example, an approximately 90 degree angled cross-section configured
to complement a portion of a square cross-section of shaft 165, to
which it may be attached.
[0106] In addition, FIG. 5B shows an example in which linearly
extending reflective elements 150 are arranged so that their ends
are staggered, i.e., lie at varying positions at the ends of
reflector 120, as measured parallel to the linear focus of the
reflector. Such staggering may blur the edges, created by the ends
of reflector 120, of the linearly extending concentrated solar
radiation pattern focused on receiver 110 by reflector 120, and
consequently produce a more uniform illumination of the receiver.
In the illustrated example, the pattern at one end of reflector 120
made by the staggered positions of reflective elements 150
complements the pattern at the other end of reflector 120. This may
allow two or more identical or substantially identical such solar
energy collectors to be aligned in parallel and adjacent to each
other with adjacent staggered ends interleaved to form an
approximately continuous reflective surface. In such cases, the
gaps between linearly extending reflective elements 150 from
adjacent reflector structures will lie at varying positions along
the length of the reflector. This also may produce a more uniform
illumination of the receivers. As evidenced by the example of FIG.
5A, staggering of the ends of linearly extending reflective
elements is optional.
[0107] Solar energy collectors as disclosed herein may be modular,
with two or more identical or substantially similar modules, which
might be independent solar energy collectors, arranged to form a
larger solar energy collector. In the example of FIGS. 6A and 6B, a
solar energy collector 310 comprises three of the example
reflector-receiver arrangement (module) depicted in FIG. 5A (and
utilized as well in the example solar energy collectors of FIGS. 1A
and 1B) arranged in line and adjacent to each other on a shared
rotation shaft 165. In other variations, two, or more than three,
reflector-receiver modules may be similarly arranged in line and
adjacent to each other on a shared rotation shaft.
[0108] Solar energy collectors as disclosed herein may also be
arranged side-by-side in parallel and ganged, i.e., driven by a
shared drive (e.g., a linear actuator) to rotate around their
respective rotation axes to track the sun. Referring now to FIGS.
7A and 7B, for example, a solar energy collector 320 comprises
three of the solar energy collectors of FIGS. 6A and 6B arranged
side-by-side and in parallel and driven by a single linear actuator
180. In the illustrated example, a linkage comprising push-pull bar
330 and lever arms 335 (a separate one of which is coupled between
the push-pull bar and each of the ganged solar energy collectors)
transfers the rotational motion of the solar energy collector
directly driven by the linear actuator to the other solar energy
collectors. In other variations two, three, or more than three
solar energy collectors may be ganged in this or a similar
manner.
[0109] FIGS. 8A-17 show several more examples of solar energy
collectors and their components. Similarly to the previously
illustrated examples, these additional example solar energy
collectors comprise one or more linearly extending receivers 110
comprising a surface 112 located at or approximately at a linear
focus of the reflector and fixed in position with respect to the
reflector, and a support structure supporting the reflector and the
receiver and pivotally mounted to accommodate rotation of the
support structure, the reflector, and the receiver about a rotation
axis 140 parallel to the linear focus of the reflector. The support
structure, reflector, and receiver may be rotated about rotation
axis 140 to track the sun such that solar radiation incident on
reflector 120 is concentrated onto receiver 110. Also similarly to
the example solar energy collectors described above, in these
additional examples the reflective surface of the reflector may be
or approximate a parabolic surface taken entirely, or primarily,
from one side of the symmetry plane of the parabolic surface.
Receiver 110 may be tilted to face reflector 120, and may be
positioned with respect to reflector 120, as in the solar energy
collectors described above.
[0110] Generally, the individual components of the additional
example solar energy collectors, and their structure and
arrangement, may be varied similarly or identically to as described
above with respect to the previously illustrated examples. Some of
the additional example solar energy collectors (e.g., those shown
in FIGS. 8A-12C) may be ganged as previously described, to allow a
single actuator to simultaneously drive (rotate) two or more
side-by-side rows of solar energy collectors. In use, the
additional example solar energy collectors may be advantageously
oriented with rotation axis 140 along an East-West direction.
[0111] Referring now to FIGS. 8A and 8B, and also to FIG. 9, an
example solar energy collector 350 differs from the examples
previously described herein primarily in the structure and
arrangement of transverse reflector support 155 and receiver
support 160, and in its rotation mechanism. Referring now to FIG. 9
in particular, in this example transverse reflector support 155 and
receiver support 160 are formed as separate pieces, rather than as
parts of a single unitary piece as previously illustrated.
Transverse reflector support 155 comprises a transverse support
member 155a supporting a plate 155b. Plate 155b comprises a notched
edge 285, with portions of surfaces 300 adjacent to the notches cut
(or otherwise formed) to define desired orientations of linearly
extending reflective elements to be supported by the transverse
reflector support. Receiver support 160 comprises a receiver mount
(or bracket) 160a at one end of a support member 160b. The other
end of support member 160b is attached to an end of transverse
support member 155b.
[0112] As described with respect to previous examples, transverse
reflector support 155 may support longitudinal reflector supports
250 (as in FIG. 8A), directly support mirrors or other reflective
elements, or support some other intermediate structure that in turn
supports mirrors or other reflective elements.
[0113] Referring again to FIGS. 8A and 8B, each assembly of a
transverse reflector support 155 and a receiver support 160 is
pivotally mounted, near the joint between support members 155a and
160b, to a support 355. These pivot points are aligned to define
rotation axis 140. A linear actuator 180 comprising an extensible
shaft 182 is mechanically coupled between a pivotal connector 184
on base 175 and a pivotal connector 186 attached to transverse
support member 155a of a transverse reflector support 155. Linear
actuator 180 may rotate transverse reflector support 155, receiver
support 160, and hence reflector 120 and receiver 110 around
rotation axis 140 to track the motion of the sun by extending or
retracting extensible shaft 182. In the absence of base 175, linear
actuator 180 may be coupled, for example, to a pivotal connector on
or attached to the ground, a rooftop, or a separate support
structure. Some variations utilize a single actuator configured as
illustrated to rotate reflector 120 and receiver 110 around
rotation axis 140, with the rotational motion transferred to other
transverse reflector supports 155 by a longitudinal member 360
extending parallel to the long axis of the reflector and attached
to each of the transverse reflector supports. Other variations may
utilize several such linear actuators, each coupled to a separate
one of the transverse reflector supports.
[0114] FIGS. 10A-10C show the example solar energy collector of
FIGS. 8A and 8B oriented to concentrate solar radiation when the
sun is directly overhead (FIG. 10A), at -5 degrees from the
vertical in the direction of the earth's equator (FIG. 10B), and at
+60 degrees from the vertical away from the equator (FIG. 10C).
[0115] Referring now to FIGS. 11A and 11B, another example solar
energy collector 370 differs from the example described in FIGS.
8A-10C primarily in its rotation mechanism. In this example, each
assembly of a transverse reflector support 155 and a receiver
support 160 is pivotally mounted, in a central region of support
member 155a, to a support 355. These pivot points are aligned to
define rotation axis 140. A linear actuator 180 comprising an
extensible shaft 182 is mechanically coupled between a pivotal
connector 184 on base 175 and a pivotal connector 186 attached to a
receiver support member 160b of a receiver support 160. Linear
actuator 180 may rotate receiver support 160, transverse reflector
support 155, and hence reflector 120 and receiver 110 around
rotation axis 140 to track the motion of the sun by extending or
retracting extensible shaft 182. In the absence of base 175, linear
actuator 180 may be coupled, for example, to a pivotal connector on
or attached to the ground, a rooftop, or a separate support
structure. Some variations utilize a single actuator configured as
illustrated to rotate reflector 120 and receiver 110 around
rotation axis 140, with the rotational motion transferred to other
receiver support members 160b by a longitudinal member 360
extending parallel to the long axis of reflector 120 and attached
to each of the receiver support members. Other variations may
utilize several such linear actuators, each coupled to a separate
one of the receiver support members.
[0116] FIGS. 12A-12C show the example solar energy collector of
FIGS. 11A and 11B oriented to concentrate solar radiation when the
sun is directly overhead (FIG. 12A), at -5 degrees from the
vertical in the direction of the earth's equator (FIG. 12B), and at
+60 degrees from the vertical away from the equator (FIG. 12C).
[0117] Referring now to FIG. 13, another example solar energy
collector 400 differs from the examples of FIGS. 8A-12C primarily
in its rotation mechanism. In this example, each assembly of a
transverse reflector support 155 and a receiver support 160 is
pivotally mounted, in a central region of transverse reflector
support 155, to a vertical support 355. These pivot points are
aligned to define rotation axis 140. Linear actuators 405 each
comprise a threaded rod 405a and a threaded pivotal connector 405b.
Each threaded pivotal connector 405b is pivotally mounted to a
lever arm 410 attached to a transverse reflector support 155. One
end of each threaded rod 405a engages its corresponding threaded
pivotal connector 405b. The other end of each threaded rod 405a is
mechanically coupled to a corresponding gear assembly 415 pivotally
connected to a lower portion of vertical support 355. A drive shaft
420 extending parallel to the long axis of reflector 120 drives
each threaded rod 405a via its corresponding gear assembly 415.
Threaded rods 405a may be driven to move threaded pivotal
connectors 405b either toward or away from vertical supports 355
and thereby rotate transverse reflector supports 155, receiver
supports 160, and hence reflector 120 and receiver 110 around
rotation axis 140 to track the motion of the sun.
[0118] FIGS. 14A-14B (end views) show the example solar energy
collector of FIG. 13 oriented to concentrate solar radiation when
the sun is at -15 degrees from the vertical in the direction of the
earth's equator (FIG. 14A) and at +65 degrees from the vertical
away from the equator (FIG. 14B). In the illustrated example, these
orientations represent the ends of the travel range for linear
actuators 405, with all angular orientations in between accessible.
In other variations, linear actuators 405 may be arranged to
provide rotation over different (e.g., greater or lesser) angular
ranges as desired.
[0119] As with other solar energy collectors previously described
herein, solar energy collectors 400 shown in FIG. 13 and FIGS.
14A-14B may be used as modules from which larger solar energy
collectors may be assembled. In the example of FIG. 15a, a solar
energy collector 499 comprises five of the solar energy collectors
400 arranged in line and adjacent to each other, mechanically
coupled, and sharing a single drive shaft 420 that drives all of
linear actuators 405. Other variations may comprise two, three,
four, or more than five of the solar energy collectors 400 so
arranged. In the illustrated example, drive shaft 420 is in turn
driven by a motor 425 centrally located along solar energy
collector 499. In some variations, solar energy collector 499
comprises two drive shafts, each driven by motor 425, extending in
opposite directions from motor 425 along the long axis of solar
energy collector 499 to drive different sets of linear actuators
405. FIG. 15B similarly shows a solar energy collector 498
comprising six of the solar energy collectors 400 arranged in line
and adjacent to each other, mechanically coupled, and sharing a
drive shaft that drives linear actuators 405.
[0120] In the examples illustrated in FIGS. 13-15b, solar energy
collectors 400, 498, and 499 each comprise a linear actuator 405
(arranged to rotate reflector 120 and receiver 110) for each pivot
point defined by the pivotal connection between a transverse
reflector support 155 and a vertical support 355, with all of the
linear actuators 405 in a solar energy collector driven by a shared
drive shaft 420. In other variations, however, more or fewer linear
actuators than pivot points may be used. Also, in other variations
more than one drive shaft may be used, with each drive shaft
driving a different set of linear actuators.
[0121] More generally, in some variations a solar energy collector
(e.g., solar energy collector 498 or 499) is assembled from two or
more (e.g., identical or substantially identical) modules, each of
which includes a transverse reflector support 155 and associated
longitudinal reflector support or supports. In some such
variations, where the solar energy collector includes N modules, it
may include N+1 pivot points (i.e., one between each module and one
at each end of the solar energy collector), with a linear actuator
associated with each pivot point to rotate the reflector and
receiver around the solar energy collector's rotation axis. The
number of modules N may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9,
10, or more than 10. The linear actuators may be driven by one or
more shared drive shafts extending along the long axis of the solar
energy collector.
[0122] One advantage to associating a separate linear actuator with
each pivot point is that the solar energy collector need not be as
resistant to torsion (twisting around its long axis) as would be
necessary if fewer drive mechanisms than pivot points were used.
Hence the solar energy collector may be of lighter construction
than otherwise, and more suitable for rooftop deployment, for
example. In addition, as explained in more detail below, gear
assemblies 415 (e.g., as shown in FIGS. 13-15a) may be arranged so
that the thrust load from the linear actuators 405, resulting from
forces exerted to rotate the reflector and receiver assembly, is
decoupled from drive shafts 420 and instead borne by vertical
supports 355. This allows the load resulting from rotation of the
reflector and receiver assembly to be easily distributed across a
large area beneath the solar energy collector, through the (e.g.,
N+1) vertical supports 355, rather than concentrated at only a
small number of locations (e.g., at the ends of a long rotation
shaft). Such a broad load distribution beneath the solar energy
collectors may also be advantageous, for example, when the solar
energy collectors are installed on rooftops or similar
locations.
[0123] Solar energy collectors 400, 498, and 499 differ from
example solar energy collectors previously described herein by
including (optional) angled cross brace 435 extending between an
upper portion of one vertical support 355 and a lower portion of an
adjacent vertical support 435. Solar energy collector 400, 498, and
499 further differ from example solar energy collectors previously
described herein by including (optional) angled cross brace 440
extending transversely to the long axis of the solar energy
collector between an upper portion of vertical support 355 and base
175, on the opposite side of vertical support 355 from its
associated linear actuator 405.
[0124] In FIG. 15a, solar energy collector 499 is shown attached to
and supported by an (optional) support structure 445 comprising
horizontally oriented cross members 450 supported by vertical
supports 455. Base portions of solar energy collectors 400 and 499
may be attached to cross member portions of support structure 445
using U-bolts 460 (FIG. 13), for example, or any other suitable
connectors. Support structure 445 may be arranged such that its
vertical supports 455 align with or are otherwise appropriately
located with respect to load bearing elements of an underlying
structure such as a roof, for example. Support structure 445 thus
serves as an adaptor between any underlying structure and the solar
energy collector it supports. Similar support structures may be
used in combination with the other example solar energy collectors
described herein.
[0125] FIGS. 16A-16C illustrate details of an example gear assembly
415 that may be employed in some variations of solar energy
collectors disclosed herein (e.g., FIGS. 13-15b) to drive linear
actuators that rotate a reflector/receiver assembly around a
rotation axis to track the sun. As explained below, in operation a
portion of gear assembly 415 pivots around drive shaft 420 to
accommodate rotation of the reflector/receiver assembly to which it
is mechanically coupled by lead screw 405a. As also explained
below, gear assembly 415 decouples the thrust load on lead screw
405a from drive shaft 420 and may instead transmit that thrust load
directly to stationary support structure of the solar energy
collector. FIGS. 16A-16C illustrate one example of a gear assembly
415 providing these functions. Other variations of gear assembly
415 providing such functions may also be advantageously employed in
the solar energy collectors described herein.
[0126] Referring now to FIGS. 16A-16C, a portion of drive shaft 420
internal to gear assembly 415 is coupled via couplers 465 to
external portions of drive shaft 420 (not shown in FIGS. 16A-16C).
Pinion gear 470 of gear assembly 415 is mounted coaxially on and
rotates with drive shaft 420. Bevel gear 475 is mounted coaxially
on the end of and rotates with lead screw 405a, which is arranged
at a 90 degree angle to drive shaft 420. Pinion gear 470 engages
bevel gear 475 to transmit rotational motion of drive shaft 420 to
lead screw 405a. Lead screw 405a engages a threaded pivotal
connector (e.g., 405b shown in FIG. 13) attached to a
reflector/receiver assembly in the solar energy collector to
transmit forces collinearly with the axis of lead screw 405a to the
reflector/receiver assembly and thereby rotate the
reflector/receiver assembly about one or more coaxial pivot points
(see, e.g., FIG. 13). Rotation of drive shaft 420 in one direction
or the other about its axis thus drives rotation of the
reflector/receiver assembly in one direction or the other about its
pivot points.
[0127] In the illustrated example, gear assembly 415 comprises a
front bracket 480 (including front wall 480a and side walls 480b)
and rear brackets 485 enclosing gears 470, 475, and a portion of
drive shaft 420. Lead screw 405a is laterally supported by bushing
490 as it passes through an opening in the front wall of bracket
480. Similarly, drive shaft 420 is laterally supported in the side
walls 480b of bracket 480 by bearings 495 rotatably contacting
bushings 500. In addition to supporting bearings 495, bushings 500
also laterally support drive shaft 420 as it passes through
openings in rear brackets 485.
[0128] Thrust loads on lead screw 405a are transmitted by thrust
bearings 505 from lead screw 405a to the front wall 480a of bracket
480 and thence to the side walls 480b of bracket 480. Thrust loads
carried by side walls 480b of bracket 480 are transmitted via
bearings 495 and bushings 500 to rear brackets 485. The thrust
loads on lead screw 405a are thus isolated from drive shaft 420 by
thrust bearings 505, bushings 500, and brackets 480 and 485. Rear
brackets 485 may be mounted on stationary support structure of the
solar energy collector using optional bolts 510, for example.
[0129] In operation, bearings 495 rotatably contacting bushings 500
allow front bracket 480, lead screw 405a, and bevel gear 475 to
pivot around drive shaft 420 as drive shaft 420 drives rotation of
a reflector/receiver assembly around its pivot points.
[0130] FIG. 17 shows gear assembly 415 as just described in
position in an example solar energy collector.
[0131] Referring again to FIGS. 13-15B, solar energy collectors
400, 498, and 499 differ from example solar energy collectors
previously described herein by including (optional) solar cells 430
on an upper surface of receiver 110. Solar cells 430 are arranged
so that they face the sun when reflector 120 and receiver 110 are
oriented to concentrate solar radiation on lower surface 112 of
receiver 110. Solar cells 430 generate electric power from solar
radiation directly incident on them rather than concentrated on
them by reflector 120. Other solar energy collectors described
herein, as well as solar energy collectors described in U.S. patent
application Ser. No. 12/788,048, filed May 26, 2010, titled
"Concentrating Solar Photovoltaic-Thermal System," may also
optionally include similarly arranged solar cells to generate
electric power from solar radiation not concentrated by the
reflectors. Alternatively, or in addition, solar cells may be
similarly arranged on or attached to portions of the support
structure of such solar energy collectors to generate electric
power from solar radiation not concentrated by the reflector.
[0132] Electric power generated by solar cells 430 may be used, for
example, to augment an electric power output from receiver 110
generated using concentrated solar radiation. Alternatively, or in
addition, electric power generated by solar cells 430 may be used
to power or partially power the solar energy collector's control
systems, drive motors, or both. In the latter cases, solar cells
430 may allow the solar energy collector to operate autonomously,
i.e., to power itself rather than draw power from the grid.
[0133] In some such autonomous variations of solar energy
collectors, the number, efficiency, and/or area of solar cells 430
is sufficient to generate sufficient electricity under a solar
irradiance of at least about 100 Watts per square meter (W/m.sup.2)
of solar cell, at least about 150 W/m.sup.2 of solar cell, at least
about 200 W/m.sup.2 of solar cell, at least about 250 W/m.sup.2 of
solar cell, at least about 300 W/m.sup.2 of solar cell, at least
about 350 W/m.sup.2 of solar cell, or at least about 400 W/m.sup.2
of solar cell to power the solar energy collector's drive system.
The drive system may include, for example, linear actuators, drive
shafts, and or motors that rotate the reflector and receiver, a
control system that controls such motors and actuators, and an
optional sun tracking system (e.g., see below) that provides
information to the control system to allow the control system to
orient the reflectors and receivers to collect solar energy. In
some variations, solar cells 430 generate sufficient electricity to
also power one or more pumps (and any associated control system
including, e.g., temperature sensors) that circulate coolant
through the receiver. In other variations, the drive system is
powered by solar cells 430, but coolant pumps and associated pump
control systems are powered by an external source of electricity.
In the latter variations, the pumps may be controlled and powered,
for example, by an application or user of the heated coolant.
[0134] Such autonomous systems may include solar cells on the lower
surface of the receiver and thus generate electricity and collect
heat (in the coolant) from concentrated solar radiation.
Alternatively, such autonomous systems may be thermal--only. That
is, some such autonomous systems may lack solar cells on the lower
surface of the receiver, use the output of solar cells 430
primarily or only to power the drive systems and (optionally) pumps
and pump controllers, and provide only collected heat (in the form
of heated coolant) as an output. In such thermal-only variations,
lower surface 112 of receiver 110 may be coated, painted (e.g.,
black), or otherwise treated to increase its absorption of solar
radiation.
[0135] Any of the autonomous solar energy collectors just described
may be optionally configured to receive electric power from an
external power source as necessary for maintenance, repair, or
other service of the solar energy collector, or as backup power in
the event the solar cells fail or otherwise provide insufficient
power, while still relying exclusively on power from solar cells
430 for routine operation. Alternatively, any of the autonomous
solar energy collectors just described may be optionally configured
to receive electric power from an external power source for routine
operation, and rely on the solar cells for back-up power in the
event the external power source fails or otherwise delivers
insufficient power. In the latter cases, autonomous operation
occurs when the external primary source of power fails.
[0136] Autonomous solar energy collectors as just describe may be
advantageously implemented with an East-West rotation axis. In such
configurations, the reflector/receiver orientation used at the end
of one day's collection of concentrated solar radiation is near to
the orientation required at the beginning of the next day.
Consequently, at the end of one day of autonomous operation solar
cells 430 will be left in position to approximately face the sun at
the beginning of the next day's operation, reducing the number and
efficiency of solar cells 430 required to power the solar energy
collector at start-up and through the day.
[0137] Any of the solar energy collectors disclosed herein may (but
need not necessarily) include one or more sun sensors used to
determine the orientation of the reflector in the solar energy
collector (e.g., of its optical axis) with respect to the position
of the sun. This information may be used to control the orientation
of the reflector to optimize or otherwise adjust the amount of
solar radiation concentrated by the reflector onto the solar energy
collector's receiver. Examples of such sun sensors are described
next.
[0138] In the schematic illustration of FIG. 18A, solar energy
collector 600 may be identical or similar, for example, to any of
the solar energy collectors described above. In addition to
components previously described, however, solar energy collector
600 comprises a fine sun sensor 605 positioned in the focal region
of reflector 120. Fine sun sensor 605 may be positioned in the
plane of the front surface of a receiver 110 for example, as shown
in FIG. 18B. When illuminated by solar radiation (indicated by rays
607) concentrated by reflector 120, fine sun sensor 605 produces a
signal or signals from which the orientation of the reflector
120/receiver 110 assembly can be determined with respect to the sun
with sufficient precision to allow that orientation to be adjusted
as desired. In some variations, fine sun sensor 605 allows
determination of the orientation of the reflector 120/receiver 110
assembly with respect to the position of the sun with a precision,
for example, of or within about .+-.0.1 degrees.
[0139] Referring again to FIG. 18B as well as to FIG. 18A, in some
variations fine sun sensor 605 comprises two solar radiation
detectors 605a, 605b positioned in the plane of the front surface
of receiver 110. Detectors 605a, 605b are positioned on opposite
sides of the center of the linear focus of the reflector, each
extending transversely with respect to the long axis of the
receiver and the linear focus of the reflector. Detectors 605a,
605b may be, for example, linearly elongated transversely with
respect to the long axis of the receiver. In this arrangement, if
the reflector 120/receiver 110 assembly is optimally aligned with
the sun to maximize collection of solar radiation (i.e., with the
optical axis of reflector 120 directed at the sun), detectors 605a,
605b will detect solar radiation of particular magnitudes and
produce signals indicating those magnitudes. If the reflector
120/receiver 110 assembly is misaligned with respect to optimal
orientation but one or both of detectors 605a, 605b are still
illuminated by concentrated solar radiation, the signals provided
by detectors 605a, 605b will indicate the magnitude and direction
of misalignment. For example, misalignment in one direction may
increase the signal provided by one of the detectors and decrease
the signal provided by the other. Hence the orientation of the
reflector 120/receiver 110 assembly with respect to the sun can be
determined by comparing signals from detectors 605a, 605b so long
as one or both of the detectors are illuminated by solar radiation
concentrated by reflector 120. Any suitable method or apparatus for
comparing the signals from detectors 605a, 605b may be used.
[0140] Detectors 605a, 605b may be or comprise solar cells, for
example. The solar cells may be, for example, of the same type as
those used in receiver 110 and/or solar cells 430. Any other
suitable solar radiation detectors may be used instead, however.
Also, any other suitable implementation or configuration of a fine
sun sensor 605 illuminated by solar radiation concentrated by
reflector 120 may also be used in place of that just described.
[0141] As illustrated in FIG. 18A, solar energy collectors as
disclosed herein may also include an optional coarse sun sensor
610. Coarse sun sensor 610 may be positioned above or on an upper
surface of receiver 110 in a plane oriented perpendicularly to the
optical axis of reflector 120, for example, as shown. Any other
suitable position and orientation for coarse sun sensor 110 may
also be used. When illuminated directly by solar radiation
(indicated by rays 612), coarse sun sensor 110 produces a signal or
signals from which the orientation of the reflector 120/receiver
110 assembly can be determined with respect to the sun with
sufficient precision to allow that orientation to be adjusted as
desired. In some variations also utilizing fine sun sensor 605,
coarse sun sensor 110 allows the orientation of the reflector
120/receiver 110 assembly with respect to the sun to be measured
with sufficient precision to adjust that orientation to illuminate
fine sun sensor 605 with solar radiation concentrated by reflector
120. That precision may be, for example, of or within about .+-.5
degrees, .+-.3 degrees, .+-.2 degrees, or .+-.1 degree. Fine sun
sensor 605 may then be used to further optimize the orientation of
reflector 120/receiver 110.
[0142] In the illustrated example, coarse sun sensor 610 comprises
two linearly elongated solar radiation detectors 610a, 610b
positioned one on either side of a linearly elongated gnomon 615
(shading structure), with the long axes of detectors 610a, 610b and
gnomon 615 arranged parallel to each other and to the rotation axis
of the solar energy collector. Gnomon 615 is oriented perpendicular
to the plane of detectors 610a, 610b, and parallel to the optical
axis of reflector 120. In this arrangement, if the reflector
120/receiver 110 assembly is optimally aligned with the sun to
maximize collection of solar radiation, gnomon 615 will be aligned
directly at the sun and will cast no shadow. If instead the
reflector 120/receiver 110 assembly is aligned away from the
optimum for collecting solar radiation, gnomon 615 will shade one
of solar radiation detectors 610a, 610b. The magnitudes of signals
provided by detectors 610a, 610b thus indicate the magnitude and
direction of misalignment of the reflector 120/receiver 110
assembly. Hence, similarly to as described for fine sun sensor 605,
the orientation of the reflector 120/receiver 110 assembly can be
determined by comparing signals from detectors 610, 610b. Any
suitable method and apparatus for comparing the signals from
detectors 610a, 610b may be used.
[0143] Detectors 610a, 610b may be or comprise solar cells, for
example. The solar cells may be of the same type as those used in
receiver 110 and/or solar cells 430. Any other suitable solar
radiation detectors may be used, however. Also, any other suitable
implementation or configuration of a coarse sun sensor 610 may also
be used in place of that just described.
[0144] In some variations, signals from a coarse sun sensor 610 as
described above are used to control the orientation of the
reflector 120/receiver 110 assembly to adjust that orientation to
illuminate a fine sun sensor 615 as described above. Signals from
fine sun sensor 615 are then used to control further adjustment of
the orientation of the reflector 120/receiver 110 assembly to, for
example, maximize collection of solar radiation.
[0145] Some other variations do not utilize a coarse sun sensor.
Some of those variations measure an absolute orientation of the
reflector 120/receiver 110 assembly (e.g., using accelerometers),
compare that orientation to a calculated position of the sun, and
adjust the orientation of the reflector 120/receiver 110 assembly
to illuminate a fine sun sensor 615 as described above. Signals
from fine sun sensor 615 may then be used as previously
described.
[0146] Some variations using a coarse sun sensor 610 in combination
with a fine sun sensor 605 additionally measure an absolute
orientation of the reflector 120/receiver 110 assembly (e.g., using
accelerometers), compare that orientation to a calculated position
of the sun, and adjust the orientation of the reflector
120/receiver 110 assembly to a range in which coarse sun sensor 610
effectively or more effectively provides signals with which the
orientation may be further adjusted to illuminate fine sun sensor
605 with concentrated solar radiation.
[0147] In addition to and as a consequence of collecting solar
energy, solar energy collectors generally shade the area beneath
them from the sun. This is particularly true, for solar energy
collectors as described herein, when the reflector/receiver
assembly is oriented to optimally collect solar radiation, or at
nearby orientations. In some variations in which a solar energy
collector is located on a building rooftop, for example, the
orientation of the reflector/receiver assembly may be adjusted to
reduce or stop collection of concentrated solar radiation by the
receiver but continue to reflect a significant portion of incident
solar radiation away from the roof and thereby provide significant
shading of the underlying rooftop. For example, the reoriented
reflector (more generally, concentrator) may block at least about
70%, about 80%, about 90%, or about 95% of the amount of solar
radiation that it would block if oriented to maximize concentration
of solar radiation onto the receiver. Such an orientation may be
selected to provide maximum shade without overheating or otherwise
damaging the receiver, for example. Such defocusing may be done,
for example, on occasions in which the supply or temperature of
coolant available to cool the receiver is insufficient to otherwise
prevent overheating the receiver. For example, such defocusing may
de done when the receiver, or a coolant in the receiver, reaches or
exceeds a predetermined temperature of, for example, at least about
70.degree. C., about 75.degree. C. about 80.degree. C., about
85.degree. C., about 90.degree. C., or about 95.degree. C.
[0148] In variations employing one or more sun sensors to control
the orientation of the reflector/receiver assembly, a defocused
orientation may in addition be selected to maintain the
reflector/receiver assembly in an orientation in which the one or
more sun sensors can provide signals with which to return the
reflector/receiver assembly to an orientation that maximizes or
substantially maximizes concentration of solar energy on the
receiver. For example, in variations employing coarse and fine sun
sensors as described above, a defocused orientation may in addition
be selected to maintain the reflector/receiver assembly in an
orientation in which the coarse sun sensor can detect the position
of the sun and effectively provide signals with which the
orientation may be further adjusted to illuminate the fine sun
sensor with concentrated solar radiation.
[0149] Maintaining significant shading of an underlying roof, as
just described, effectively provides a "white roof" that may
advantageously keep the building on which the solar energy
collector is located cooler than would otherwise be the case.
[0150] As noted above, in some variations a reflector 120 comprises
linear reflective elements arranged end-to-end in rows (e.g., of
equal length) along the length of the reflector, with two or more
such rows arranged side-by side (see, e.g., FIGS. 8A, 11A, and
15B). In such variations, and as illustrated, the linear reflective
elements may be of two or more different lengths and arranged such
that gaps or joints 375 between the reflective elements in one row
are not next to gaps or joints between reflective elements in an
adjacent row. In some variations, no gaps or joints between
reflective elements in any row are next to gaps or joints between
reflective elements in any adjacent row. In some variations, the
majority of gaps or joints between reflective elements in any row
are not adjacent to gaps or joints between reflective elements in
any adjacent row. Arrangements such as those just described may
produce a more uniform illumination of the receiver by concentrated
solar radiation than would occur if gaps or joints between
reflective elements in rows were generally next to gaps or joints
in adjacent rows.
[0151] Also as noted above, in some variations linearly extending
reflective elements 150 have a laminated structure. Referring to
FIG. 19A, in the illustrated example reflective element 150
comprises a low-iron glass layer 720 having a first surface 722 and
a second surface 723. In use in a solar energy collector as
disclosed herein, reflective element 150 is oriented so that
surface 722 faces the receiver (and hence also the incident solar
radiation). A reflective layer 725 is disposed on the second
surface of the low-iron glass layer. An adhesive layer 730 is
disposed on the reflective layer. A second glass layer 735 is
attached by adhesive layer 730 to reflective layer 725.
[0152] In the example illustrated in FIG. 19B, reflective layer 725
is absent from edge portions (e.g., around the entire periphery of
reflective element 150) of the second surface 723 of low-iron glass
layer 720. Adhesive layer 730 attaches corresponding edge portions
(e.g., around the entire periphery of reflective element 150) of
second glass layer 735 directly to the exposed edge portions of
surface 723, and attaches other portions of second glass layer 735
to reflective layer 725. In this example, adhesive layer 730, in
combination with glass layers 720 and 735, may seal and/or protect
reflective layer 725 from the external environment.
[0153] Low-iron glass layer may be, for example, about 0.5
millimeters to about 3 millimeters thick. Reflective layer 725 may
comprise, for example, silver, gold, chrome, or any other suitable
metal or non-metal material or materials and be, for example, about
20 nanometers to about 200 nanometers thick. Adhesive layer 725 may
comprise, for example, an acrylic closed-cell foam adhesive tape
(e.g., VHB.TM. tape available from 3M.TM.), and be, for example,
about 0.5 millimeters to about 1.5 millimeters thick. Second glass
layer 735 may comprise, for example, soda lime glass or
borosilicate glass and be, for example, about 2 millimeters to
about 5 millimeters thick. In one example, low-iron glass layer 720
is about 1 millimeter thick, reflective layer 725 comprises silver
and is about 80 nanometers thick, adhesive layer 730 comprises
acrylic closed-cell foam tape and is about 0.9 millimeters thick,
and second glass layer 735 comprises soda lime glass and is about 4
millimeters thick.
[0154] Reflective layer 725 may be deposited and patterned (e.g.,
its edges removed), and adhesive layer 730 deposited, by
conventional processes, for example.
[0155] Any of the above described variations of solar energy
collectors may optionally be provided with spray nozzles, or the
equivalent, located on the receiver 110 or the receiver support
160, for example, and configured to spray a washing fluid (e.g.,
water) onto reflector 120 to wash the reflector.
[0156] This disclosure is illustrative and not limiting. Further
modifications will be apparent to one skilled in the art in light
of this disclosure and are intended to fall within the scope of the
appended claims. For example, a shared hydraulic or pneumatic drive
system driving two or more (hydraulic or pneumatic) linear
actuators may, in some variations, be substituted for a shared
drive shaft driving two or more linear actuators as described
herein.
* * * * *