Parabolic solar collector body and method

A solar collector structure and method of fabrication are disclosed, the solar collector being of the linear, parabolic reflector-type. The parabolic reflector body includes an elongated layered structure having a concave parabolic reflective surface. The reflector body is supported and reinforced by a longitudinal beam member bonded to the convex backside of the layered structure. The layered structure includes a first reflective layer and a supporting molded layer formed of an amorphous hard-curing adherent material such as concrete or stucco. The entire reflector body structure is fabricated on an elongated convex mold. The method of fabrication includes forming the mold using a screed-moving apparatus which moves longitudinally along the mold. As the parabolic reflector body is formed on the mold, the screed-moving apparatus is again used to shape portions of the reflector body. A means for fabricating a parabolic reflector body, including both the elongated mold and the molded and reflective portions of the reflector body, together with the reinforcing longitudinal beam member, is also disclosed.

BACKGROUND AND SUMMARY OF THE INVENTION 
The Invention relates generally to parabolic reflector-type solar 
collectors which concentrate solar energy along a focal line, and in 
particular to a parabolic reflector body construction suitable for in 
situ, large-scale fabrication, together with a method for making the same. 
Elongated, parabolic solar collectors employ a concave trough-like 
reflective surface having a parabolic shape to focus the sun's energy onto 
a focal line. Such collectors harness solar energy by positioning an 
absorber pipe or similar energy transfer device along the focal line of 
the parabolic reflector. Concentrated solar energy heats the water or 
other transfer medium in the absorber pipe, which is then transferred to a 
generator or similar device to perform useful work. 
Linear parabolic collectors are rotationally mounted and pivoted 
mechanically to follow the diurnal movements of the sun. Installations of 
linear parabolic collectors date back to the early part of this century. 
One example is the solar-powered pumping station built by Mr. Frank Shuman 
in Meadi, Egypt, in 1913. Today, large-scale linear parabolic collectors 
could provide an economically viable alternative to conventional power 
generation systems, if large-scale reflector structures with sufficient 
structural integrity and stability can be constructed at a cost low enough 
to justify the required financial investment. Roughly two-thirds of the 
cost of harnessing solar energy by means of parabolic solar collectors is 
the construction of the large numbers of collectors required. The cost of 
each collector structure must be reduced if a favorable cost-to-benefit 
ratio is to be achieved for solar energy. The twin goals of reducing cost 
and increasing benefits for a solar collector installation will need to be 
met before solar energy becomes an economically important energy resource. 
Designing and building solar power stations for generating electricity is a 
complex problem requiring large-scale, efficient collectors at locations 
which receive maximum sunlight. Two alternatives for providing collectors 
at high-sunlight locations are (1) to construct collectors at the site, 
typically a remote location without fabrication facilities, or (2) to 
construct the collectors elsewhere and transport them to the site. The 
required size of linear parabolic solar collectors make their transport 
impractical. 
Fabricating large-scale linear parabolic collectors out of steel framing is 
not only time consuming and expensive but also subject to introduction of 
optical distortion due to fabrication stresses. Maximum collector 
efficiency requires exceptionally accurate parabolic reflective surface, 
which in turn requires high-tolerance construction techniques. Structures 
supporting a parabolic reflector-type collector must be both well designed 
and accurately assembled to produce and maintain its parabolic shape under 
thermal conditions which vary widely throughout its useful life. Weather 
conditions, temperature extremes and corrosion represent a constant 
challenge to the integrity of any exposed, steel-frame structure. Assembly 
of a frame-type collector at the site of a power station requires 
transport of a large volume of material to the site and accurate assembly 
under sometimes harsh conditions. 
It would be advantageous to be able to fabricate highly accurate, 
free-standing parabolic collectors in remote locations without the need to 
transport all structural materials to the site. It would also be 
advantageous to provide linear parabolic collectors which possess a high 
degree of internal strength and structural integrity to resist changes in 
shape under various thermal conditions and adverse weather conditions. It 
would be particularly advantageous to provide parabolic solar collectors 
which can be fabricated economically enough to compete, on a per 
Kilowatt-Hour (kWH) basis, with conventional thermal energy sources such 
as fossil fuels and nuclear power. 
It is an object of the present invention to provide a parabolic reflector 
body of the type which concentrates solar energy along a focal line, for 
use in linear parabolic collectors, and which can be fabricated on an 
elongated convex parabolic mold near where the solar collector is to be 
permanently installed. 
It is another object of the invention to provide a method of fabricating 
parabolic solar collectors of the type which concentrate solar energy 
along a focal line. The method includes forming an elongated mold having a 
convex top surface with a parabolic cross-section and then forming an 
elongated layered structure and associated support structures on the mold. 
Accordingly, the invention provides a parabolic reflector body fabricated 
on an elongated, convex parabolic mold, the reflector body being of the 
type which concentrates solar energy along a focal line. The parabolic 
reflector body comprises an elongated layered structure having a parabolic 
concave first side, a convex second side opposite the first side, and 
generally parallel longitudinal edges. The layers of the structure include 
a reflective layer on the concave first side which contacts and is 
conformed to the mold during fabrication, and a support layer bonded to 
the first layer on the convex second side. The support layer is 
predominately formed of an amorphous hard-curing adherent material applied 
over the reflective layer in a moldable state and conformed generally to 
the convex shape of the mold. In addition, the reflector body includes a 
beam member bonded to the layered structure on the second side thereof, 
extending longitudinally parallel to the side edges of the layered 
structure. In its preferred form, the reflector body includes a tubular 
beam member which is embedded into a ridge of amorphous hard-curing 
adherent material applied on the support layer. Additional structural 
members are provided, extending generally between the beam member and the 
layered structure, to further support the reflector body. 
The invention further provides a means for fabricating a parabolic 
reflector body, the means being an intermediate construction formed during 
the process of fabricating the completed reflector body. The means for 
fabricating comprises the mold on which the layered structure of the 
reflector body is fabricated, together with the layered structure itself. 
The mold of the present invention is an elongated mold having a convex top 
surface with a parabolic cross-section. The elongated reflector body 
fabricated on the mold, which body is detachable therefrom after 
fabrication, includes a layered structure having a concave parabolic first 
side, a convex second side and generally parallel longitudinal edges. The 
layers of the body include a reflective layer on the concave first side in 
contact with and conforming to the mold, and support layer, bonded to the 
reflective layer. The support layer is predominately formed of an 
amorphous, hard-curing adherent material applied over the reflective layer 
in a moldable state and shaped to generally conform to the mold. In its 
preferred form, the means for fabricating a parabolic reflector body 
includes a beam member extending longitudinally along the support side of 
the layered structure, generally parallel to and centrally disposed 
between the longitudinal edges. A central ridge of amorphous, hard-curing 
adherent material in a moldable state is preferably centrally disposed on 
the support layer, together with similar parallel edge ridges extending 
longitudinally adjacent the edges of the layered structure. The beam 
member is partially embedded in the central ridge. Additional structural 
members are partially embedded in the edge ridges and are preferably also 
embedded in mortar extending along the beam member. 
The invention further provides a method of fabricating a parabolic 
reflector body of the type which concentrates solar energy along a focal 
line. The method comprises steps which include forming an elongated mold 
having a convex top surface with a parabolic cross-section. Steps in 
forming the elongated mold include providing a hard-curable moldable 
material on a base surface, such as the ground. A screed is then guided 
over the moldable material by means of a screed-moving apparatus. The 
screed has a parabolic shape and is moved longitudinally along the base 
surface supporting the mold. After the screed has shaped the mold, the 
moldable material is allowed to cure. 
Following formation of the mold, an elongated layered structure is formed 
on the mold by steps including: applying a reflective layer of material 
having a reflective surface on the top of the mold with the reflective 
surface facing down; positioning a lattice of reinforcing members over the 
reflective layer; and forming a support layer on the reflective layer. The 
support layer is formed by steps including applying an amorphous, 
hard-curing adherent material in a moldable state onto the reflective 
layer to a depth which covers the reinforcing members. The support layer 
is then shaped by guiding a screed over the amorphous, hard-curing 
adherent material by means of the screed-moving apparatus used to form the 
mold, whereby the reflective and support layers together form the layered 
structure of the reflector body. 
In its preferred form, the method further includes bonding a beam member 
longitudinally to the support layer of the layered structure, after the 
shaping of the support layer. Additional preferred steps include forming a 
central ridge of amorphous, hard-curing adherent material on the support 
layer centrally on the second side of the layered structure and forming 
two additional parallel ridges adjacent the edges of the layered 
structure. The beam member is then embedded into the central ridge of 
amorphous hard-curing adherent material and additional structural members 
are partially embedded in the edge ridges and similarly embedded in mortar 
extending along the beam member. After curing, the reflector body is an 
integral, self-supporting unit with a highly accurate parabolic, concave 
front surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, parabolic reflector bodies according to the present 
invention are fabricated on an elongated, convex parabolic mold 20. The 
mold is created by a mold-forming apparatus 22 employed at o near the site 
where a solar energy power station is to be constructed. The mold-forming 
apparatus includes a pair of guide rails 24 positioned along a base 
surface 25 on which the mold is to be formed. Base surface 25 will, in 
most installations, be the ground, suitably graded to provide a relatively 
firm, level surface on which mold 20 and apparatus 22 are supported (base 
surface 25 is the support surface on which the structures shown in FIGS. 
1, 3-9 and 11 rest). The mold-forming apparatus 22 includes a movable 
frame 26, supported on wheels 28, which ride on and move along rails 24. 
Referring to FIGS. 1 and 2, the movable frame 26 of mold-forming apparatus 
22 carries a grading tool 30, which is box-shaped, having parallel side 
walls 34, 36 joined to parallel end walls 38, 40 to surround and enclose a 
central rectangular channel 42. The lower edges 44, 46 of side walls 34, 
36, respectively, each have a parabolic arcuate shape which, when drawn 
laterally across a moldable substance, serves as a screed to grade and 
form the moldable material into a parabolic shape. Parabolic edges 44, 46 
are formed by a machining tool which forms an accurate curvature in 
accordance with coordinates established by the equation of the parabola, 
as is well known in the art. The shape of the parabola, which establishes 
the parabolic shape of the completed reflector body, is selected by the 
designer to position the focus of the parabolic reflector at whatever 
distance is preferred for the final solar collector installation. The 
parabolic lower edges 44, 46 of side walls 34, 36 serve as a shaping 
device for shaping moldable material when moved at right angles across the 
moldable material. Grading tool 30, shown in FIG. 1 on and surrounded by 
movable frame 26, and also shown in FIG. 2 (turned 90.degree. from FIG. 
1), is hereinafter referred to as screed 30. 
Movable frame 26, includes means for supporting screed 30 between rails 24, 
above base surface 25. Pins, bolts or other fastening means extend through 
selected openings 51 in frame 26 and through cooperating openings 52 in 
end walls 38, 40 of screed 30, to releasably attach the screed to the 
frame. A plurality of openings 51 are provided in frame 26 to allow the 
screed to be positioned at selected heights above base surface 25. In that 
way, parabolic edges 44, 46 of the screed can be repositioned to form 
moldable material into a parabolic shape at different heights above base 
25. 
The first step in the method of fabricating a parabolic reflector body in 
accordance with the present invention is to form an elongated mold having 
a convex top surface with a parabolic cross-section. That step is 
accomplished by, first, providing a hard-curable, moldable material on 
base surface 25. The moldable material used to make mold 20 is preferably 
concrete, stucco or mortar, referred to hereinafter as concrete. The 
concrete is laid down on base surface 25 by introducing it through central 
opening 42 of screed 30. In an installation for fabricating parabolic 
reflectors on a relatively large scale, as presently envisioned, rails 24 
of mold-forming apparatus 22 are approximately 12-22 feet apart and 
movable frame 26 is approximately 6 feet high. To introduce concrete into 
screed central opening 42, in such a large-scale installation, a concrete 
mixing truck (not shown) or the like will drive alongside apparatus 22 and 
direct freshly mixed concrete into opening 42 via suitable pumps and 
conduits. The concrete will flow out through the open bottom 32 of screed 
30, adjacent parabolic edges 44, 46. Movable frame 26 is simultaneously 
moved along rails 24, spreading the fresh concrete supplied through 
opening 42 over base surface 25. 
As soon as a sufficient quantity of concrete has built up on base surface 
25, the top of the concrete begins to be shaped by parabolic edges 44, 46 
of screed 30. As frame 26 moves along rails 24, the second step in the 
forming of mold 20 is accomplished, namely, guiding a screed having a 
parabolic shape over the concrete to form the concrete into a convex, 
elongated parabolic mold. The step of guiding the screed over the concrete 
is accomplished by means of movable frame 26, which serves as a 
screed-moving apparatus movable longitudinally along base surface 25. 
Depending on the composition of the concrete, the rate at which concrete 
is introduced in opening 42, and the speed at which screed 30 is moved 
over the mold, one or more passes of screed 30 over mold 20 may be 
required to complete the shaping of the mold. 
Referring to FIG. 1, the rails 24 of mold-forming apparatus 22 can be of 
any desired length. Thus, the apparatus is capable of forming a mold of 
any useful length. A typical width 62 for mold 20 would be 16 feet. In 
most applications, rails 24 will be up to several hundred feet long and 
the apparatus 22 will be used to form one continuous mold structure of the 
same length. Alternatively, a plurality of consecutive molds, each 
approximately 35 feet long and 16 feet wide could be formed. The thickness 
66 of each mold along the center line of the mold, referred to as 
longitudinal axis 64, is approximately 12-16 inches, with the thickness 
tapering down to zero along the parallel longitudinal side edges 68, 70 of 
the mold. Central longitudinal axis 64 and side edges 68, 70 are mutually 
parallel to one another. An apparatus 22 used to create a plurality of 
35-foot long mold segments, will form the molds on base surface 25 
co-linearly, all the molds extending lengthwise along longitudinal axis 
64. 
In forming individual molds, the ends of each mold segment, depicted as 
flat end 72 in FIG. 1, are formed by placing substantially vertical forms, 
made of wood or the like, on base surface 25, as will be readily 
understood by those skilled in the art. The forms (not shown) will confine 
the moldable material (i.e., concrete) until the material has cured and 
hardened, after which the forms will be removed. 
Referring to FIG. 3, a completed mold 20, in the form of an elongated, 
convex parabolic body, rests on base surface 25. A plurality of retainer 
openings 76, such as pin-receiving sockets or the like, are embedded into 
mold 20 around its periphery prior to curing, for attachment of 
reinforcing members in later steps of the fabrication process. Retainer 
sockets 76 are embedded into the concrete of mold 20 to be flush with the 
mold surface. Retainer sockets 76 can receive hooks, eyelets or other 
suitable devices for retaining reinforcing wire or the like. FIG. 3 
illustrates retainer sockets 76 at spaced intervals along the parallel 
side edges 68, 70 of mold 20 and over the end crown of the mold, adjacent 
end 78 of top surface 60. Similar retainer sockets are provided at the 
opposite end (not shown) of mold 20 in the same manner as along edge 78. 
To complete mold 20, top surface 60 will preferably be smoothed and 
otherwise finished to form a hard, relatively smooth parabolic surface on 
which a parabolic reflector body is formed in accordance with the present 
invention. Rails 24 remain as part of the screed-moving apparatus of the 
invention, which includes frame 26, wheels 28 and rails 24, and which is 
used later in the fabrication method to shape portions of the reflector 
body. 
The next step is to form an elongated layered structure on mold 20, as part 
of the parabolic reflector of the present invention. To form the elongated 
layered structure, a layer 80 of reflective material is first applied to 
the top surface 60 of mold 20, with the reflective surface facing down. 
Referring to FIG. 4, reflective layer 80, also referred to as first layer 
80, is shown in position on the top 60 of mold 20. Reflective layer 80 can 
be any type of reflective material, including silvered glass, anodized 
aluminum, galvanized sheet metal, glass-glazed silvered steel, aluminized 
or silvered plastic, or various ceramic materials onto which a reflective 
surface can be added. The non-reflective, convex backside of layer 80 is 
selected or coated to bond to mortar. 
The material forming reflective layer 80 will preferably be a thin, flat 
material which bends to conform to the parabolic shape of mold top surface 
60, or is pre-made with a parabolic shape which conforms to the shape of 
top surface 60. The latter type of pre-formed material could include heavy 
glass sheeting and ceramics, but such material is very expensive and 
relatively delicate to transport to remote locations and therefore is not 
favored for use as the reflective layer. Anodized aluminum or plated and 
glazed steel sheet material is considerably less expensive and easier to 
manufacture and handle, although such materials have slightly lower 
reflectivity. The selection of the reflective material used in layer 80 
must be based on a cost-benefits analysis, at least in commercial 
installations. The exact formulation of layer 80 is matter of design 
choice and the several alternatives discussed above, as well as others, 
could be used within the scope of the present invention. 
Assuming metal, thin glass or another bendable material is used for 
reflective layer 80, the material will be draped over mold 20 and confined 
to the parabolic shape of upper mold surface 60 by reinforcing wires 90 or 
equivalent means. The reflective surface is oriented to face downwardly 
toward mold 20. It may be desirable to protect the reflective surface of 
the reflective layer from scratches, due to direct contact with mold 20, 
by interposing a protective sheet of paper or a similar disposable 
material between first layer 80 and the mold. Such a protective sheet of 
material could be specified for inclusion by the manufacturer of the 
reflective layer at minimal additional cost. 
After reflective layer 80 has been laid down on mold 20, reinforcing 
members 90 are installed over the reflective layer to reinforce the next 
layer laid down. Reinforcing members 90 are preferably steel wire, 
approximately 0.03 inches in diameter, spaced at 2-inch or greater 
intervals, or at the intervals between retainer sockets 76. Reinforcing 
members 90 are anchored to mold 20 by means of hooks, eyelets or other 
suitable devices inserted into retainer sockets 76 on the periphery of the 
mold. FIG. 4 illustrates reinforcing members 90 in a rectilinear, 
cross-hatched pattern. For rapid, efficient installation, reinforcing 
members 90 are laid directly against the convex upper or back surface of 
layer 80. As an alternative to using wire for reinforcing members 90, a 
suitable pre-formed reinforcing mesh or lattice, similarly anchored to 
retainers 76, can be used for the reinforcing material. Such a reinforcing 
mesh, formed of wire or the like, would be laid directly onto the back 
convex surface of the reflective layer and secured to retainers 76. 
After the reinforcing members have been placed over reflective layer 80, 
the mold is prepared to receive a second layer, referred to as support 
layer 100, composed of amorphous, hard-curing adherent material. The 
support layer is applied over the reflective layer while the amorphous, 
hard-curing adherent material is in a moldable state, and is subsequently 
shaped to its final configuration. FIG. 4 illustrates how mold 20 is 
prepared to receive the support layer. Barrier strips 82, 84 are installed 
along the side edges of reflective layer 80 to serve as forms confining 
the support layer until it cures. Barrier strips 82, 84 are joined at 
their respective ends to barrier strips 86, and a corresponding barrier 
strip at the distal end of mold 20 (not shown), along the distal end of 
reflective layer 80. Barrier strips 82, 84, 86 are preferably laid down 
over reinforcing members 90. Together, barrier strips 82, 84, 86 provide a 
form into which concrete, mortar, stucco or another amorphous, hard-curing 
adherent material is caused to flow while in a moldable or flowable state. 
Hereinafter the amorphous, hard-curing adherent material used to form the 
support layer will be referred to as stucco. 
The next step in forming the elongated reflector body of the present 
invention is to bond the support layer to reflective layer 80. The support 
layer is predominantly formed of stucco, applied over the convex backside 
of layer 80 in a moldable or fluid state and shaped to generally conform 
to the shape of mold 20, within the confines of barriers 82, 84, 86. The 
bonding of support layer 100 to reflective layer 80 occurs during the 
curing process of the stucco. The stucco is applied using the 
screed-moving apparatus shown in FIG. 1 and described in connection 
therewith. Apparatus 22 is employed to support screed 30 above mold 20. 
Parabolic shaping edges 44, 46 are raised a selected distance above the 
level employed in forming mold 20 by resetting the retaining pins in holes 
51 to a different set of holes 51 in frame 26. Screed 30 is raised enough 
to provide the desired thickness for support layer 100. In a large-scale 
parabolic mold fabrication installation, producing parabolic reflector 
bodies of approximately 14 feet in width and 30 feet in length, it is 
anticipated that support layer 100 will be approximately one inch thick. 
Stucco is applied over reflective layer 80 by introducing moldable or wet 
stucco through opening 42 of screed 30 (see FIGS. 1 and 2) while 
simultaneously moving the screed longitudinally along mold 20 on rails 24. 
Use of the screed-moving apparatus 22 of FIG. 1 permits the stucco to be 
applied over the reflective layer to a depth which covers reinforcing 
members 90. When sufficient stucco has been applied to raise the support 
layer to the level of the curved parabolic lower edges of the screed, the 
moving screed 30 will contact and shape the support layer. In most 
instances, screed 30 will be guided over the wet stucco of the support 
layer one or more times in order to shape the support layer to correspond 
to the shape of parabolic edges 44, 46 of screed 30. An alternative method 
of applying the stucco would be to spread stucco by hand or another means 
to a depth slightly exceeding the final depth desired and guiding or 
drawing screed 30 over the stucco to give it a final shape. 
The formation and shaping of support layer 100 results in an elongated 
layered structure 102 resting on mold 20. Referring to FIGS. 4, 5 and 10, 
layered structure 102 includes reflective layer 80 and support layer 100 
resting on the convex top surface 60 of mold 20. The elongated layered 
structure has a concave parabolic first side 104 (see FIG. 10, 
illustrating layered structure 102, together with the rest of the 
parabolic reflector body, after removal from mold 20), a convex second 
side 106, opposite the first side 104, and generally parallel longitudinal 
edges 108, 110, formed by barrier strips 82, 84. Layered structure 102 
also includes a first end 112 formed against barrier 86 and a second end 
114 (FIG. 10) at the distal end of the mold. 
After support layer 100 has been applied and shaped so that its second side 
106 generally conforms in shape to the parabolic top surface 60 of mold 
20, a beam member 120 (FIG. 6) is bonded to the support layer. Beam member 
120 is positioned centrally on the back or second side 106 of layered 
structure 102, parallel to central axis 64 of the mold, midway between and 
parallel to longitudinal edges 108, 110. Beam member 120 is preferably in 
the form of a steel pipe with closed ends, also referred to as a 
closed-ended length of tubular steel. The exact position where beam 120 is 
installed on layered structure 102 is important to the final alignment of 
the parabolic reflector body. Consequently, beam 120 should be carefully 
aligned parallel with the central axis of layered structure 102. A 
convenient means of accurately aligning the beam member is to include 
index marks 121 on the beam member which can be precisely aligned with the 
longitudinal axis of 64 of mold 20. Suitable marks (not shown) on mold 20 
could be used to assist in assuring precise alignment between the beam 
member and layered structure 102. Index marks 121 on the beam member are 
preferably scribed onto the steel surface during manufacture. 
Beam 120 is bonded to the layered structure 102 by steps shown in FIGS. 5, 
6 and 7. A central ridge 122 of amorphous, hard-curing adherent material 
is formed on second layer 100, extending longitudinally along the spine or 
topmost longitudinal line extending along the second convex side of 
support layer 100. Ridge 122 is preferably formed of the same material as 
is support layer 100, for example, stucco. Ridge 122 is applied to the 
surface of support layer 100 by any suitable means while the support layer 
is wet or uncured, such as by directing a flow of wet stucco onto support 
layer 100. Beam member 120 is then partially embedded in central ridge 122 
while the stucco is in a moldable state, securing the beam member to the 
two-layered structure 102. 
Referring to FIG. 6, tubular beam member 120 is covered in selected regions 
with an adherence-enhancing covering such as a pattern of reinforcing wire 
124 welded or otherwise attached to the beam member. In FIG. 6, 
reinforcing wire 124 having a sinusoidal pattern is welded to the beam 
member on one side, and a similar adherent pattern of material is welded 
to the beam member on the opposite side (not shown) in order to enhance 
adherence of the beam to the central stucco ridge 122. Without the 
adherence-enhancing properties of surface 124 welded to the beam member, 
the beam will not properly adhere to the stucco. 
FIG. 7 shows the partially completed parabolic reflector body 130. Beam 
member 120 is bonded to support layer 100 of elongated layered structure 
102 along central stucco ridge 122. Additional side ridges of stucco 132, 
134 (see FIGS. 5, 6 and 7) are applied to support layer 100, either 
simultaneously with the formation of central ridge 122 or after the 
central ridge has been formed and beam member 120 partially embedded 
therein. Side ridges 132, 134 are formed of stucco in a moldable state, 
and applied to support layer 100 while it is still in a moldable state. 
The side ridges are parallel ridges of amorphous, hard-curing adherent 
material. The ridges are formed on support layer 100, one on each side of 
central ridge 122. 
To further reinforce the structural integrity of the parabolic reflector 
body, additional structural members are attached between side ridges 132, 
134 (FIG. 7) and beam member 120. Referring to FIG. 8, the additional 
structural members are preferably in the form of a plurality of concrete 
slabs, each partially embedded in one or the other of side ridges 132, 134 
and extending to beam member 120. Reinforcing slabs 140, 142 are 
preferably flat, relatively thin slabs of concrete formed at a site near 
where parabolic reflector bodies of the present invention are fabricated. 
Formation of reinforcing slabs 140, 142 can be by any conventional means, 
such as, for example, by providing concrete forms of a suitable depth, 
having flat bottoms, in which wet concrete is poured. The concrete used 
for slabs 140, 142 can be the same or similar to that used for forming 
mold 20, or can be stucco or another equivalent moldable, hard-curing 
material. FIG. 8A illustrates a representative concrete slab used for 
reinforcing slabs 140, 142, the representative slab being slab 140. 
Referring to FIGS. 8, 8A and 9, reinforcing wires 144 are embedded in slabs 
140, 142 during formation, as is well known in the art. The reinforcing 
wires 144 protrude beyond the side edges 146, 148 of slab 140. Similarly, 
reinforcing wires 144 extend beyond the side edges 150, 152 of slab 142 
(FIG. 8), to facilitate anchoring the slabs to the reflector body. Each 
Slab 140, 142 is preferably a unitary, continuous, elongated body 
extending the full length of the parabolic reflector. 
Referring to FIG. 9, in order to bond slabs 140, 142 to the other 
structural parts of the parabolic reflector under construction, additional 
stucco is applied along and over slab edges 146, 148, 150, 152. Barriers 
are installed at locations 160, 162 and 164, adjacent the ends of beam 
member 120 and side ridges 132 and 134 (FIG. 7), respectively, to confine 
the additional stucco applied. Barriers similar to 160, 162, 164 are also 
applied at the distal end of mold 20, as will be readily understood. After 
installation of barriers 160, 162, 164, slabs 140 and 142 are each bonded 
along one edge to beam 120 and along the opposite edge to layered 
structure 102. Slabs 140, 142 are bonded to beam member 120 by an 
application of stucco 154, which serves as a cementing substance bonding 
the slabs to beam member 120. Applied stucco 154 surrounds and overlies 
the reinforcing members 144 protruding from edge 148 of slab 140 and edge 
150 of slab 142. The additional stucco also engages the reinforcing wire 
124 welded to beam member 120. 
Edge 146 of slab 140 is bonded to layered structure 102 by applying 
additional stucco to edge ridge 132 (see FIG. 7), previously applied. The 
additional stucco, together with the side ridge 132, partially embeds edge 
146 in stucco ridge 132. Similarly, edge 152 of slab 142, and the 
reinforcing wires 144 protruding therefrom, are partially embedded in 
stucco ridge 134 by applying an additional layer of stucco over edge 152 
and the adjacent reinforcing wires. 
After the additional stucco 154, 166 and 168 have been applied, the entire 
reflector structure is allowed to cure and harden and the reinforcing 
wires are clipped from the retainers in retainer sockets 76 on mold 20. 
Once that has occurred, the parabolic reflector body 130 is lifted from 
mold 20 as a single unit. Referring to FIG. 10, reflector body 130 is 
shown inverted after removal from mold 20. Elongated layered structure 102 
has a concave parabolic first side 104, a convex second side 106 and 
generally parallel longitudinal edges 108, 110. Beam member 120 is bonded 
to the convex second side 106 of layered structure 102 by means of central 
ridge of stucco 122. Reinforcing slabs 140, 142 help support and stabilize 
the entire structure. 
As shown in FIG. 10, layered structure 102 extends lengthwise between a 
first end 112 and a second end 114, the latter being referred to herein as 
the distal end. Beam member 120, is slightly longer than layered structure 
102, extending beyond first end 112 and second end 114 (not shown) in 
order to provide a means for rotatably supporting the parabolic reflector 
body for rotation about the central axis 174 of the tubular beam member. 
The end portions of beam member 120--end portion 176 being at first end 
112 and a corresponding end portion (not shown) at the distal end of the 
beam member--include cylindrical support surfaces for supporting the 
reflector body 130 for rotational movement about axis 174. Referring to 
FIG. 11, cylindrical support surface 178 is that part of end portion 176 
on which the beam member 120 rests when mounted for rotational movement. A 
corresponding cylindrical support surface is provided on the distal end of 
beam 120. 
FIG. 11 shows a representative means for installing and rotatably 
supporting parabolic reflector body 130 in a solar collector installation. 
FIG. 11 shows first end 112 of parabolic reflector body 130. A 
corresponding support structure will be used at the distal end (not shown) 
to support second end 114 (see FIG. 10). A support pedestal 180 rests on 
base surface 25, such as the ground. The pedestal includes rotational 
mountings 182 for engaging cylindrical support surface 178 of cylindrical 
beam member 120. Each rotational mounting is in the form of a plurality of 
rollers 184. A motor 186 and belt or chain 188, coupled to beam member 
120, rotates the beam member and attached parabolic reflector structure 
130 about the beam member axis 174. Assuming the orientation of the 
support structure and parabolic reflector is properly aligned with the 
rotational axis of the earth, the installation shown in FIG. 11 will 
permit parabolic reflector 130 to effectively follow the diurnal movement 
of the sun. 
It is anticipated that a plurality of individual reflector bodies 130 will 
be mounted generally co-linearly with one another, for rotation about a 
single continuous axis 174, which is the axis of the beam member 120. A 
single electric motor 186 and drive means 188 will thereby be used to 
rotate a plurality of parabolic reflector bodies 130. Adjacent collector 
bodies are coupled together by aligning scribed beam member index marks 
121 (FIG. 6) and welding adjacent beam members to one another. In that 
way, the reflector bodies can be assured of coordinated, identical 
patterns of movement under the control of a single control mechanism. 
One of the advantages of using a closed-ended tubular or cylindrical beam 
member 120 as the major support of reflector body 130 is the storage 
capacity provided in the interior of the tubular beam member. One 
practical application for the storage capacity within tubular beam member 
120 is the storage of fluids such as hydrogen gas, turbine exhaust 
condensate, or other useful fluids. In order to access the interior of 
tubular beam member 120, a passageway for fluid is provided by one or more 
openings 190 through the closed end of the beam member, as shown in FIG. 
6. Openings 190, in conjunction with plumbing extending to a suitable 
rotary seal, enable fluid to flow into and out of the interior of the beam 
member. The use of the interior of beam member 120 for gas storage, such 
as for hydrogen gas, can be part of an energy-storage system which 
generates hydrogen gas electrically by electrolysis during daylight, 
peak-production periods, stores the hydrogen gas under pressure within 
beam 120, and utilizes the hydrogen at night to produce additional power. 
Such systems can help to make large-scale solar collectors cost effective, 
continuous energy producers. 
A representative system for collecting the solar energy focused along a 
focal line is illustrated in FIG. 11. An absorber tube 200 is positioned 
above the concave reflective surface 104 of collector body 130 along the 
focal line of the parabolic surface. Absorber tube 200 is mounted in any 
suitable manner, such as by a support strut 202 and wires 204, 206. The 
absorber tube is coupled to a fluid conduit 208, which transports a 
heat-absorbing medium carried within absorber tube 200 to a transfer 
conduit 210 mounted axially along axis 174 of tubular beam member 120. A 
suitable rotary seal 212, having a fluid-tight rotational seal, couples 
transfer conduit 208 to conduit 210. Similar absorber tubes 200 will be 
mounted above each parabolic reflector body 130 in a continuous 
installation extending along a linear array containing a plurality of 
reflector bodies. Water or another heat transfer medium is pumped through 
absorber tube 200 and conduits 208 and 210, transferring heat generated 
within absorber tube 200 to an external use such as a steam turbine (not 
shown) for power generation or the like. 
Another use of the parabolic reflector bodies of the present invention, 
particularly on overcast, rainy days when power generation is not 
possible, is to collect water. Referring to FIG. 10, the parabolic 
reflector surface 104 has a trough-like shape which ca be an efficient 
water collector. All that is necessary is to orient the reflector bodies 
generally horizontally and water falling on the parabolic surface 104 will 
run to the center. A provision of a slight incline will cause the water to 
flow to one end of the reflector body, as will be readily understood. In 
installations with a plurality of reflector bodies arranged co-linearly, a 
connecting water channel 220 is provided at the lower end of the reflector 
body to channel water thereon onto the next or adjacent reflector body. 
The lowest or final collector body in a line of collector bodies will be 
provided with a suitable collection trough or device for recovering the 
water which falls on all the collector bodies in the line. Large-scale 
installations containing up to hundreds or even thousands of collector 
bodies will be able to collect and recover substantial quantities of water 
in this manner. The water can be used in the steam generation process or 
for another purpose. 
The invention provides a highly accurate, stable parabolic reflector body 
useable in solar collector installations. The collector body, when 
completed, is a virtually unitary and monolithic device which will 
effectively retain its accurate parabolic shape under extreme variations 
in the environment. The absence of bolts, rivets, and the like reduces the 
chance of structural deformation and degradation over time. Fabrication of 
the parabolic reflector body is accomplished on a mold which is formed at 
or near the location of the solar collector installation. The same 
apparatus used to create the mold is subsequently used in the fabrication 
of the collector body itself. Because it is formed of molded concrete, 
stucco or mortar, it is fabricated using large quantities of sand, a raw 
material present in many desert locations where solar installations are 
constructed. Consequently, a significant portion of the material used to 
fabricate the collector bodies will be present at or near the solar 
installation, reducing construction costs and transport costs. Because the 
collector bodies are fabricated in situ, construction costs are minimized. 
The invention further provides a means for fabricating parabolic reflector 
bodies in the form of a mold with a partially-completed collector body 
thereon. The means for fabricating the collector body employs the 
efficient fabrication techniques of the invention. The invention further 
provides an efficient method of forming parabolic reflector bodies at or 
near the sight of a solar collector power station. 
In addition to its advantages as part of a solar collector, the collector 
bodies of the present invention include storage space useful in power 
generation, within the tubular beam member on which the collector bodies 
are supported. Furthermore, the collector body is useable to collect 
rainfall which, at remote desert locations, is a scarce and valuable 
commodity. 
The present invention provides solar collector bodies which can be 
fabricated and erected at only one-tenth the cost of prior art collector 
installations. Because of the importance of the cost-to-benefit ratio in 
achieving greater commercial use of solar energy, it may be desirable to 
make minor alterations to further reduce costs. For example, the storage 
feature of tubular beam member 120 could be eliminated and the beam member 
perforated to provide an adherent surface, instead of welding reinforcing 
wire to the beam member, as shown at 124 in FIG. 8. Reinforcing slabs 140, 
142 could be exchanged for sheet-metal struts or the like which, in 
certain circumstances, might prove less expensive. Other cost reduction 
techniques will occur to those skilled in the art as installations 
according to the present invention are constructed. 
The invention provides a parabolic reflector body for use in linear 
parabolic collectors which concentrate solar energy along a focal line. 
The reflector bodies can be fabricated near where the solar power station 
is to be permanently installed. Each reflector body is fabricated on an 
elongated convex parabolic mold. The means for fabricating the collector 
bodies comprises a portion of a collector body in place on the mold from 
which an integral parabolic collector body, capable of rotational movement 
to follow the sun, can be efficiently fabricated.