Note: Descriptions are shown in the official language in which they were submitted.
1~716~49
Solar energy collecting device~ are of two type8, ~hose with movable
part:s which track the sun and flat plate collectors. The latter have presented
a problem in that it was hitherto neces~ary for their co~ponents to be indi~
vidually designed and crafted, adding appreciably eo the cost. Present dey
tec~mology in the glas~ industry would now allow for mass production.
The pri~e problem a~sociated with solar collector3 has been the ef-
ficient retention of heRt energy or stated conversely the prevention cf he~t
108s. ~eat 1088 oc~urs in three ways, by convection, by conduct~on and by
radiation. The first means of heat transference, convection, can be eliminated
by evacuating the ambient surrounding the heat absorption means. Conduction
can be appreciably reduced by eliminating the use of good heat conductors such
as m2tals, and the interfacing of materialæ with different level~ of heat
contuctivity.
The refocusing of scattered radiation ~y the concave ~ir~ored sur-
face of the ~acket and by the one way reflector coating on the remainder of
the inner ourface of the ~acket, 80 that it is directed on the blackened heat
absorption neans, further aid~ in reducing heat lc88. The evacuated smbient
reduces deterioratioo of the mirror, and the efficiency of the blackening mæans
increase heat absorption.
It io the primary ob~ect of the present invention to pro~ide a
collector which i8 capable of ~a~ production, relatively low in cost,
durable and which generates the st hea~ for the available solar radiation.
Partlcular care has been given to desi8n a solar collector suitable for u~e
in clouty and cool climes with a ~lnimum of heat loas. A practical collector
~hould act as a one way hoat trap, energy ~hould flow uni-directionally
into the sy~tem and not radiate back out. The present collector has been
dèsi8ned wholly of borosilicate glas~ pre~enting no interfaces of differing
materials with different ratcs of heat conductivity and its attendent heat
10~8. The all gl~88 collector 1~ capable of being mass produced and has
hiKh evacuation and insulating capabillties which will withstand long periods
of cold and cloudy weather.
There is an ancillary benefit derivet from the u~e of an all glass
collector, namely it solves one of the ~Dst urgent of collector problems,
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corrosion. Corrosion has been a formidable problem in this
art both from exposure to the elements which requires elaborate
shielding, and from the circulation of the fluids within the
collecting tubes. Corrosion has necessitated premature and
costly replacement of parts in the collectors.
The present evacuated tubular solar thermal collector
has many unique features among which are that it is constructed
entirely of glass with the exception of the aluminized reflective ~ ~ -
surface. This construction eliminates heat losses attendant
with metal-fluid interfaces. Additionally, glass to metal seals
are not as strong as glass seals. An all glass construction
alleviates expansion problems in a system in which the inner
and outer tubes will be at varying tempertures in a high vacuum.
The use of a high vacuum virtually eliminates conven- -
tion and the use of glass minimizes conduction. In effect, the
operatlng efficiency of the collector is independent of the
outslde temperature, which is particularly important in cold
climate~.
Broadly speaking, therefore, and in summary of the
abovel the present invention may be defined as a glass solar
energy collector tube comprising an outer cylindrical evacuated
~acket having a reflective coating on its inner surface extending
around approximately half the circumference of the ~acket and
constituting a concave mirror, inner glass absorption tubing
circulating heat storing fluid in and out of the jacket, the
tubing lying in the focal plane of the concave reflecting coating,
glass connecting means between the outer jacket and the inner
tubing to support and position the tubing within the jacket, and
blackening means associated with the inner tubing to increase
3D the absorption of heat energy, the ~acket comprising a main
elongated cylindrical body portion having a central longitudinal
; axis, a sealed necked entry portion coaxial with tbe longitudinal
axis, and a dimini~hed rounded end, and the reflecting coating
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extending the length of the main elongated cylindrical body
portion of tlle jacket, the absorption tubing for circ-llating the
heat storing fluid entering through the sealed entry of the jacket
and being offset in the main body portion, ~xtending nearly the
length of the nlaln body portioll of the jacket, and doubling over
upon itself defining parallel ingress and egress legs, one of
the legs lying along the principal axis of the concave mirror
and the other leg of the inner tubing paralleling the one leg
and being disposed between the one leg and the longitudinal axis
of the body portion of the jacket for capturing scattered
radiation, the one leg being spaced from the reflecting coating,
and the legs being similarly offset to exit the sealed necked
entry of the jacket.
The present invention will be described in greater
detail and with reference to the drawing6 wherein:
- Figure 1 is a plan view of a solar collecting panel
mounted on a support structure.
Figure 2 is a plan view of an individual collector
tube with the process tube for evacuating the colleotor still
in place.
Figure 3 i9 a cross-sectional view taken on line 3-3
of Figure 2.
Figure 4 is a cross-sectional view taken on line 4-4
of Figure 3 through the neck of the collector tube ~acket.
Figure 5 is a cross-sectional view taken through the
main cylindrical portion of the collector tube ~acket.
Figure 6, appearing on the same sheet as Figure 1, is
the top end view of the lntake and outtake portions of the fluid
circulating tube system.
Referring now to the drawings in detail wherein like
reference characters indicate like parts throughout the several
figures, the reference numeral 10 indicates generally a solar
collector panel which consists of a number of collecting tubes
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each having an outer evacuated glass jacket 8, which encases
heat absorption fluid circulating tubes 12 which are serially
connected in the panel, see Figure 1. A process tube 14 used
for evacuating the glass jacket, is shown in Figures 2 and 3,
before it is burned off when
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1~7~49
the neck 16 of the ~acket i8 se~let after the vacuu~ i8 achievet. The
vacuum 18 of a high order, (4 x 10 6 Torr.) which virtually eliminates the
convection mechanism of heat 1088. The main body of the gla3s ~acket i~
a C~*i~ rS
cylindrical in configuration and about one hundred and twelve ~ in
len~Sth, the neck of the ~acket i8 additionally seventy-five millimeters long
and the opposite diminished rounded end 20 i8 fifty millimeters in length.
The absorption tube 12 wh1ch has a diameter of nineteen millimeters as com-
pared to a hundred ~illi~eters of the cylintrical ~acket enters the neck of
the cylinder and i8 offset to extend the length of the main portion of the
cylinder in proxlmity to and parallel with the wall of the cylinder. The tube
12 is doublet over upon itself short of the rounded end 20 to lie as clo~e to
itself as po~sible without contact. The egress tube parallel~ the ingress tube
for the length of the cylinter and i8 similarly offset to exit the neck of the
~acket. In Figures 1 and 6 insulating sleeves are ~hown encasing the con-
necting portions of the tubes 12. The doublet over humped turnaround bight
B f tube 12 is ~hown in Figure ~ and lndicated at 13. A curved gla~s support
and positionlng means 24 has three arched portions connected together with the
free ends of each secured one to the humped turn of the circulatlng tubing,
and the other two, designated 26, to opposed walls lô of the diminished end
20. ~11 members described, the ~acket, heat absorption tubing and support
~nd po~itioning me~bers are made of borosilicate glass. There are no inter-
facos of dissimilar materials to di~sipate the heat.
There are three wsys to blacken the heat absorption tublng. The cir-
culation fluid may be blackened by means of dyes or colloidal suspensions such
a~ Lo~pblack, graphite or charcoal in a water base. Antl-free~e and other
agent~ may be added to the fluid. A black coating on either the outer or inner
surface of tube 12 would provide another means of achlevlng heat absorption.
An aluminum coatlng i~ placed upon the inner sur~ace of the cylin-
drical ~acket extendlng the length of the maln portion thereof and having a
lateral extont of half the clrcu~ference of the ~acket. Thi~ coated 3urface
constitute~ a concava cylintrical d rror for the reflection of entering
light rays to focu~ them on the absorption tubi~g. The absorption tubing
i~ placod along tho princlpal a~is of the concave reflecting mirror at the
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focus of the light reflectet from the mirror. Parallel rays of light enter-
ing the cylindrical tubing will be slightly converged by the convex surface
o the ~acket and the focusing of the reflected light fron the concave
mirror will be closer to the mirror than the principal focu~ and will extend
the length of the mirror. Some of the entering rays of light will strike the
inner ab~orption tubes directly and be absorbed, but others will be directet
to the mirror and refocused on the lnner absorption tubing. Some of the
radiation will scatter snt exit the glass cylinder. The doubllng of the
absorption tubing will extend it a dist~nce of over for~y ~illimeters deep
into the ~acket along the primary axi8 of the concave mirror. Thi~ tepth
will allow the upper portion to capture scattered radlation. By necking the
cylinder, the absorption tubing will retard 3cattered radiation and serve as
additional insulation in that area. To further minimize the 10~8 of scat-
tered radiation, a one war light transmitting coating, known in the glass art,
may be applied to the inner surface of the ~acket. Such one wny transparent
coating would allow light to pass unl-directionally into ths cylinder but not
out. Those coatings may act a8 a second reflecting surface bouncing back
~cattered radlstlon and retaining it within the collector tube.
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