Bulb-type solar energy collector

The disclosure relates to a bulb-type solar energy collector device comprising a hollow glass body shaped with a parabolic interior surface that is coated with specular finish of a metal, e.g. silver, and includes an apex aperture and integral hollow yoke. A hollow glass, bulb-shaped absorber element is exteriorly coated with a wave length selective coating. The bulb-shaped element includes a tubular hollow stem dependent from the bulbar portion and fixed in the yoke of the glass body so that the central axis of the stem and bulbar end portion is along the focal axis of the parabolic reflecting surface. A cover plate is sealed over the enlarged end of the reflecting surface enclosing the interior mirror surface in a chamber which is evacuated to substantial vacuum, e.g. 10.sup.-4 torr or greater vacuum. A working media is circulated from a source in a manifold through the interior volume of the absorber element to remove the solar energy absorbed thereby as heat and the media is returned to the manifold. The solar energy laden media is available for heating, cooling or power generating uses.

The present invention relates to an apparatus for collecting radiant energy 
from the sun and supplying that energy in the form of heat for use in 
other apparatus for heating, cooling or other useful work applications. 
The apparatus of the present invention employs a bulb-type radiant energy 
collector comprised of three principal structural parts fabricated 
basically of glass. 
In my copending applications Ser. Nos. 682,705 and 682,8l7, both filed May 
3, 1976, a bulb-type solar energy collector is disclosed in which a molded 
glass body includes a parabolic interior wall surface which includes a 
hollow tubular end extension centered on the axis of the parabolic wall. A 
hollow tubular wall absorber element closed at the one end and open at the 
other end is fixed into place along the central axis of the parabolic 
wall. A transparent cover plate closes the space within the parabolic wall 
of the body, and the space is evacuated to a high vacuum. The absorber is 
coated on the exterior surface with an energy absorbing material. 
SUMMARY OF THE INVENTION 
In the present construction, the bulb-type collector is fabricated of glass 
parts and a special absorber element of enlarged surface area is utilized 
within the vacuum space of the parabolic walled reflector. The absorber 
element is a blown glass bulbar shape having a hollow dependent 
cylindrical or hollow stem. The bulbiferous portion of the element is 
preferably substantially spherical in shape, which provides the maximum 
surface area for a bulbous collector and maximum strength. The strength 
factor is significant because the absorber element will be exposed to the 
vacuum pressure differential. One (outer) surface of the absorber will be 
at vacuum pressure conditions while the opposite (inner) surface will be 
at approximately atmospheric or greater pressure. 
The exterior surface area of the bulbiferous portion of the absorber 
element is provided with an opaque coating layer of a solar energy 
absorbing material of a type herein disclosed to absorb the solar energy 
focused thereon by the parabolic wall surface. The parabolic wall is 
mirrored by a specular coating of a metal compound, such as silver. The 
solar radiation striking the parabolic reflector is focused to the axis 
and onto the absorber surface. 
If the collector apparatus is mounted stationary at a mean solar exposure, 
or is employed with some device for tracking of the sun, the absorber 
element of this invention will operate with efficiency. 
The collector of the present invention being constructed of glass parts, 
may be manufactured and assembled by utilizing known equipment, such as 
glass forming equipment suitable for pressing, blowing or centrifugally 
molding glass articles. As indicated in my aforementioned applications, 
the collector may be shaped exteriorly into interfitting or interlocking 
assemblies to construct a curtain wall surface made weather resistant and 
situated on a favorable solar exposure of a building, viz the roof or a 
wall surface thereof. 
A significant feature of the invention is the means in the structure by 
which radiation losses are reduced. This is accomplished by a wave length 
selective coating on the absorber surface and by keeping the exposed 
surface area of the absorber member relatively small in relation to the 
larger surface area of the parabolic reflector. 
The bulb collectors are assembled onto a manifold apparatus by inserting an 
outwardly depending hollow yoke thereof into an aperture formed in the 
manifold. In one form of the invention, the yoke is sealed in the manifold 
aperture by rubber ring gasket or ring grommet seals. 
The fluid from the manifold is circulated into the absorber bulb and back 
into the manifold through the stem portion thereof by fluid handling means 
extending into the absorber. Circulation of the working fluid through each 
of the bulb absorbers of the collectors continuously removes the heat 
energy of the solar radiation collected on the energy absorption surface 
of the absorber element. The solar radiation is focused onto the surface 
of the absorber member by the mirrored specular parabolic surface at the 
interior of the bulb body. Relatively high temperatures may be developed 
in the working fluid by the apparatus of this invention. 
Other advantages of the invention will be more readily apparent to those 
skilled in the art from the following detailed description of the 
drawings, on which:

DESCRIPTION OF THE INVENTION 
Referring to FIGS. 1 and 2, a bulb body 10 is molded, such as by pressing, 
centrifugal casting or pressing and blowing glass in a mold (not shown) to 
form an annular glass wall 11 defining on its interior surface 12 a 
paraboloid of revolution generated about a central axis which is the focal 
axis for surface 12. This surface 12 may be in the form of parabolic 
segments joined together about the central focal axis. This surface of 
whichever of such forms is herein called a "parabolic surface". At the one 
end of the glass body wall 11 is a large end opening defined by the 
peripheral edge 13. An outwardly projecting peripheral flange 14 depends 
from edge 13 which encircles the collector body 10. Along the axis at the 
apex of the parabolic surface 12 there is a tubular wall extension which 
is the yoke portion 15 of the glass body. The one end 15a of yoke 15 is 
integral with the glass wall of the parabolic portion and defines an 
aperture 16 concentrically disposed about the focal axis of the parabolic 
surface 12. The outer open end 17 of yoke 15 provides the means by which 
the collector is connected onto a manifold system, to be hereinafter 
described. 
The glass body 10, just described, is treated to receive a thin specular 
coating 18 of silver, or the like, over the parabolic surface 12 to form a 
specular mirror finish throughout the parabolic surface to the aperture 
16. 
The absorber member 19 comprises a hollow, enlarged, substantially 
spherical, bulbous end portion 20 from which there depends a hollow, 
substantially cylindrical stem portion 21. The absorber member 19 may be 
blow molded from glass and annealed, or otherwise heat treated, to provide 
sufficient strength in the unit to withstand and hold the pressure 
differentials in the collector which is under vacuum after the absorber is 
installed in the collector body 10. The outer end of stem 21 is open and 
may include an outwardly flared portion 21a adjacent the end. The O.D. of 
flared portion 21a is approximately the same as the I.D. of the open end 
17 of yoke 15. In assembly of the absorber 19 in yoke 15, the flared 
portion 21a of the absorber stem is fused by a glass-to-glass seal thereof 
in the end 17 of the yoke. 
Additionally, before assembly, the absorber stem 21 may be worked upon 
heating the glass to the softening point or higher such that an annular 
rib-like enlargement 22 is formed along the stem length; the rib 22 having 
an O.D. that is the same as or slightly larger than the diameter of 
aperture 16 in the glass wall 11. The absorber member 19 also includes a 
coating layer or layers 23 of an energy absorbing coating which extends at 
least over the bulbous end 20 and a part of stem 21 disposed above 
aperture 16. Thus, a coating 23 is applied beginning at about rib 22 
upwardly over stem 21 and all of the exposed exterior surface of 
bulb-shaped end portion 20. 
The coating 23 takes the form of a highly efficient solar energy absorbing 
coating, e.g. a wave length selective coating. The glass absorber member 
19 with the coating 23 thereon comprises the means by which radiation of 
the sun is absorbed by the collector. The absorber 19 will be disposed 
axially (vertically) in the unit with its central axis generally aimed at 
the sun. The absorber is of a smaller surface area compared to the 
relatively large surface area of the parabolic reflector surface 12. This 
contributes greatly to a minimal radiation heat loss from the unit by 
having the absorber of the smaller surface area. The highly efficient 
coating 23 on the absorber tube further reduces radiation losses and 
retains the energy on the absorber member 19. The bulb collector unit is 
highly efficient for collection of the energy of the sun's rays. 
Circulation of working media through the interior of the absorber tube, 
such as described hereinafter, exchanges the absorbed heat of the sun's 
energy which is carried by the media. The wave length selective coatings 
should have the property of very high absorption (preferably more than 0.8 
absorption in wave lengths above 2.5 microns) and very low emission 
(preferably less than 0.1 emission in the infra-red wave lengths, less 
than 2.5 microns). 
The coated absorber member 19, just described is assembled along the 
central axis of the body 10 (focal axis of surface 12). In assembling the 
collector shown on FIGS. 1 and 3, the absorber 19 is inserted open end 
first past the large opening 13 of the glass wall reflector aperture 16 
and into yoke 15. Flared end portion engages the inner wall surface of 
yoke 15 near the end thereof and the rib engages (or nearly so) the glass 
of wall 11 adjacent the perimeter of aperture 16. Glass of the flared end 
may be (preferably) fused with the glass of the yoke wall adjacent open 
end 17. The glass in rib 22 is similarly (preferably) fused with the glass 
of wall 11 around aperture 16. The solar absorber element 19 is now 
connected in place in the collector bulb assembly. 
A face plate or cover plate 25 is formed of transparent glass and includes 
a circular outwardly domed section 26, and an integral peripheral flange 
27. The perimeter of inner edge 28 of the domed section of the face plate 
approximately matches the circular edge 13 on the bulb body, and the 
flange 27 overlies the peripheral flange 14 thereof. Inasmuch as the bulb 
interior is under vacuum, the convex cover plate adds strength to the 
assembly. However, a flat cover plate may be used with success. 
As seen on FIGS. 1 and 3, a tubulation 29 is formed on the glass wall 11 of 
the bulb which includes an aperture 30. The bulb and face plate are now 
assembled and securely fastened or joined together at the matched flanges 
14, 27. This is most conveniently done by fusion of the two flanges of 
glass. The interior space or chamber within the bulb is next evacuated by 
connecting a vacuum pump at tubulation 29 and combined with a bake out the 
interior of the bulb collector is drawn down to a vacuum of 10.sup.-4 torr 
or more; whereupon, tubulation 29 is tipped off and sealed in the known 
manner (see bulb 10 on FIG. 3). The vacuum chamber within the bulb 
collector reduces the convection and conduction of heat losses of the 
unit. 
As shown in FIG. 3, several of the bulb collectors 10 may be assembled onto 
a manifold connected in a system for circulating a working medium, i.e. 
gas or liquid. 
THE MANIFOLD 
The manifold 31 is shown connected with an array of collector bulbs 10. 
Working media, such as water, is circulated from the manifold into each of 
the bulbs so that the bulbs are serviced in a parallel arrangement. 
Although a liquid media (water) is suggested for use with this 
arrangement, a gaseous media, such as air, may be substituted. 
The manifold 31 is comprised of a top wall 32 and bottom wall 33 and 
opposed side walls 34 which define a conduit that is divided 
longitudinally into upper and lower passageways 35 and 36 respectively, by 
a central wall 37 extending sidewise of the conduit from opposite side 
walls 33. The aperture 38 in wall 32 receives the yoke 15 of a bulb 
collector which is sealed in the manifold by a pair of O-ring gaskets 39. 
Working media is connected from the lower passageway 36 into the interior 
chamber of the absorber element 19 by a delivery tube 40 which has its 
upper open end 41 spaced from the top of the bulbous end 20 of the 
absorber. Flow of the working media is shown by the arrows on FIG. 3 in 
which cooler media flows from passage 36 into the absorber and exchanges 
heat with the glass wall thereof in the bulb shaped end 20. The heated 
media returns to passageway 35. 
Manifold 31 also includes a complete exterior layer 42 of sufficient 
thickness of an insulation, such as a foamed (cellular) polyurethane or 
the like. Preferably, the exposed exterior of insulation layer 42 is 
coated or painted with a sealer, such as a plastic or paint, to close any 
cellular structure and provide a more durable exterior to the unit. 
As may be seen, for example as illustrated by the ray lines on FIG. 3, the 
sun's rays pass through the face plate and strike either the energy 
absorbing surface 23 of the absorber tube or strike the mirror surface 18 
of the parabolic reflector 12. The rays impinging upon the mirror surface 
of the parabolic reflector are reflected to the focal axis of parabolic 
surface 12 whereat they strike the coated outer surface of the bulbar 
absorber. The vacuum in the space inside the bulb prevents loss of energy 
from convection and conduction. 
As shown on FIG. 3, the bulb collectors may be peripherally joined as a 
curtain wall installation that affords resistance to weather and the like. 
The several bulb collectors may be placed in side-by-side arrangements 
with their sealed together flanges 14, 27 abutting one another. A suitable 
grouting compound or cement 43 is forced in the seams around the flanges 
sealing the exposed plane of the collectors from leakage, which produces 
run off of snow and rain or the like to keep the curtain wall from sun 
masking obstructions, etc. 
Having illustrated and described several embodiments of the invention 
herein, it should be understood that further modifications may be resorted 
to without departing from the spirit of the invention and scope of the 
appended claims.