Solar energy converter

Converter for use in a location adjacent the inside of a window to receive solar energy and change it to useful heat.

BACKGROUND OF THE INVENTION 
The rays of the sun which fall on an exposed surface on a sunny day contain 
considerable amounts of energy. It has been calculated, for instance, that 
a square foot of cross-section of the sun's rays contains 86,000 BTU's in 
a day. When these rays fall on a window, they pass through in the form of 
actinic rays, as well as ultraviolet and infrared, the more substantial 
portion of the thermal energy being in the lower wave length or infrared 
rays. However, when sun's rays pass through a window, they do so at a 
fairly high angle and they usually fall on a horizontal surface beside the 
window such as part of the floor. Energy is absorbed by such a surface and 
is only re-radiated to a small extent, so that it does not add very much 
to the heating of the room. The heat that is thus carried by the sun's 
rays but is not used, has been recognized for a considerable number of 
years and many attempts have been made to utilize it. Most of the 
inventions in this area involve a screen (similar to a venetain blind) 
where slats are mounted transversely of the window to receive the heat and 
convert it to useful energy. It has even been suggested that the slats be 
coated with a heat-absorptive material. Prior attempts have been less than 
successful for a number of reasons: the slats seem to be incapable of 
trapping any high percentage of the sun's energy. There is no provision 
for the admission of light into the room or to allow any degree of 
observation outwardly and attempts to produce a flow of air have not been 
effective. Most of this prior art apparatus has been very expensive and 
requires substantial adjustment and attention to operate to its highest 
degree. These and other difficulties experienced with the prior art 
devices have been obviated in a novel manner by the present invention. 
It is, therefore, an outstanding object of the invention to provide 
apparatus for receiving the sun's rays and converting them efficiently 
into useful heat. 
Another object of this invention is the provision of solar energy converter 
arranged beside a window to change the sun's rays to heat and, 
nevertheless, to allow light to enter the room and to permit a person 
inside of the room to see out to a certain extent. 
A further object of the present invention is the provision of a solar 
converter which is simple in construction, which is inexpensive to 
manufacture, and which is capable of a long life of useful service with a 
minimum of maintenance. 
It is another object of the instant invention to provide a solar converter 
which operates most effectively during the winter months, but which, 
nevertheless, is capable of receiving the sun's rays from a substantial 
range of angle and converting it effectively into heat. 
A still further object of the invention is the provision of a solar 
converter which not only absorbs most of heat from the rays of the sun 
passing through a window, but converts it into a flow of heated air. 
It is a further object of the invention to provide a solar energy converter 
consisting of curved slats whose curvature not only increases the 
absorption of solar energy over a wide range of angles, but also promotes 
effectively a proper flow of heated air. 
With these and other objects in view, as will be apparent to those skilled 
in the art, the invention resides in the combination of parts set forth in 
the specification and covered by the claims appended thereto. 
SUMMARY OF THE INVENTION 
In general, the invention consists of a solar energy converter including a 
support adapted to be mounted on the inside frame of a window. A plurality 
of slats are mounted on the support, each slat being curved in the 
transverse direction with a convex surface facing the window. Each slat is 
formed of a material having a high capacity for thermal absorption and 
having the said convex surface coated with a heat-absorbing coating. 
More specifically, the support consists of two spaced, parallel beams, each 
having a rectangular cross-section with the longitudinal direction 
extending perpendicular to the window. Each slat has an elongated slot 
through which each beam passes and each beam having a notch in which the 
edge of the slot rests. The dimensions of the beam and of the slots in the 
slats are selected in such a way that the convex surface of the slat is 
directed in such a way that more heat is absorbed when the sun is in the 
winter range of angles.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring first to FIGS. 1 and 2, which best show the general features of 
the invention, it can be seen that the solar energy converter, indicated 
generally by the reference numeral 10, is provided with a support 11 which 
is mounted on the inside frame 12 of a window 13. Mounted on the support 
11 are a plurality of horizontal, parallel, vertically spaced slats 14. 
Each slat is formed from a thick sheet of aluminum or other metal having a 
high capacity for absorbing thermal energy. 
The support consists of two spaced, parallel, vertical beams 17, each beam 
having a rectangular horizontal cross-section. As is evident in FIGS. 4 
and 5, each slat 14 has a slot 19 through which each of the beams 17 and 
18 pass. Referring to FIG. 5a, each beam has a step means such as a notch 
21 to receive one end of the slot 19. 
In FIGS. 6 and 6A it can be seen that in an alternative form of the 
invention the slat 14a has a length which is adjustable by means of a 
number of central apertures 23. Fasteners 24 extend through the apertures 
and hold the two halves in a selected, fixed, longitudinal position. 
In FIGS. 7 and 7A it can be seen that the beam 17a is a modified form of 
the invention that is also made adjustable by being formed in two 
overlapping parts whose corresponding notches can be located in a 
generally coincidental position to provide adjustment of the length of the 
beams. The beams 17a and 17b are not only provided with notches 21, but 
also with notches 22 at the other edge. 
The operation and advantages of the present invention will now be readily 
understood in view of the above discussion. The beams 17 and 18 are 
suspended from the upper part of the frame 12 of the window 13 by means of 
hooks. Slats can then be introduced on the lower end of the beam and 
dropped into place in the notches which hold them in the proper spaced 
positioning and, since the beams extend vertically downwardly, the 
angularity of the slats 14 is determined by its relationship to the beam. 
This is best evident in FIG. 2. When the sun's rays strike the surface of 
the slats 14, the absorbant coating, combined with the highly 
heat-absorbant nature of the metal from which the slats are formed, causes 
the slat to heat up and by convection and radiation heat up the air 
between the window 13 and the vanes themselves. As is evident in FIG. 3, 
the curvature of the slats 14 provides an outwardly-directed convex 
surface 15 which is curved so that the sun's rays strike the surface 
approximately at a right angle to a tangent both in a high and a low 
position. This curvature will be selective, of course, to allow this to 
occur mostly in the late fall, winter, and early spring months at which 
time of year the heat is necessary. At other times of the year the 
converter 10 would probably be removed from the window, but in any case 
(with the sun very, very high) the effect would not be as great. In any 
case, the flow of air, therefore, takes place up the space between the 
window 13 and the converter and passes inwardly in the space between the 
slats. With the slat adjustment means shown in FIGS. 6 and 6A it is 
possible to adjust the slats to accommodate itself to a wide range of 
window sizes. In the same way the vertical height can be adjusted by use 
of the means shown in FIGS. 7 and 7a. 
It can be seen, then, that, because the converter slats are fixed in spaced 
position and at an appropriate angle in the notches provided on the 
supporting beams, the mounting angle and the curved or arcuate profile 
provide proper focus of the convex surface of each slat with the sun at 
relatively low positions throughout the heating season from September 
through March. Sunlight passing through the window is converted 
immediately into thermal energy within the absorbing slats. This causes 
heat-transfer to the surrounding air, thus inducing convection of heated 
air upward and inward. The air flow thus generated is directed by the vane 
effect of the series of concave sides of the slat and this conversion is 
continuous while sunlight is present and, consequently, produces free 
solar heat in the building. Anodized aluminum slats provide the most 
efficient solar energy collection, conversion and heat-transfer. The 
spaces are provided between the slats to permit free and unobstructed flow 
of converted air through the absorber slat assembly for maximum 
heat-transfer and most effective heated air delivery into the room. This 
feature also provides for vision outwardly through the device and through 
the window from within the building. It also allows a limited amount of 
sunlight to enter the building for natural illumination, while providing 
some shading protection against fading of colors in articles in the room. 
The design of the invention is of the utmost in simplicity and has a 
minimum number of different parts, all parts being of a simple shape. It 
provides assembly dimension alternatives for a broad variety of window 
lengths and widths. It will be necessary to install two support hooks at 
the upper part of the window lintel. In addition, the invention provides 
optimum durability and fire safety by use of heavy gauge aluminum absorber 
slats, by using metal support beams and metal support hooks. There is a 
minimum of maintenance and the optimum of aesthetic value is achieved with 
permanent dark colored anodized finishes. 
The National Energy Act of 1978 defined a challenge to be met that would 
serve to reduce American consumption of fuel and its dependency on its 
imported fuels. The development of on-site solar energy equipment has been 
encouraged by the U.S. Department of Energy with goals for solar 
alternatives to supply 20% of the energy demand toward a balanced energy 
program. While active systems with flat plate collectors have proven 
successful in domestic hot water and space heating applications, the 
present high cost of these systems (with long term pay-back) serves to 
retard consumer implementation and the utilization of the renewable solar 
energy source. With the present invention, a low cost device is provided 
to retrofit existing buildings with solar collection capability. The 
present invention reduces the cost of equipment by avoiding the necessity 
for some of the more expensive parts that are necessary to construct an 
outdoor flat plate collector. The present invention does not require an 
enclosure case, a transparent panel, collector supporting components, and 
motor-driven fans or pumps that are necessary in the more elaborate 
outdoor installations. The present invention is intended to be installed 
indoors adjacent windows that face south, east and west where sunlight is 
generally unobstructed in the winter season. The invention, therefore, 
utilizes the building as an enclosure and the existing windows as the 
transparent panels and it serves to convert sunlight into thermal energy 
delivering heated air directly within the building by means of natural 
convection and without any other means such as pumps or fans. The U.S. 
Department of Energy has established passive solar heating gain potentials 
as high as 120,000 BTU's per square foot of collector area. The average 
home or small building with approximately 8 windows can be retro-fitted 
easily by the consumer with 8 units of this invention to provide as much 
as 140 square feet of solar collector area. Adapting this low cost 
equipment serves to facilitate utilizing solar energy to produce a 
supplementary heat that may be as high as 16,800,000 BTU's per year. This 
is an equivalent of the usable heat of 120 gallons of oil per year. 
In a commercial version of the invention, the cost of this equipment was 
approximately $3.00 per square foot, so that $420 (reduced by the 30% 
energy tax credit) results in a net cost of 294. At present oil prices 
this means a payback possibility of 2 years. The invention has an 
effective life expectancy of 10 years, so that the consumer may realize an 
average return as high as $114 (30%) per year on this investment, assuming 
that oil prices do not change. The invention, therefore, offers 
substantial longterm savings for the consumer and provides an alternative 
means of utilizing renewable solar energy, while providing an opportunity 
to reduce fossil fuel consumption and the demand for imported oil. While a 
single on-site installation appears to contribute little to the national 
energy goal, when this contribution is multiplied by millions of homes and 
small buildings that could be equipped, the consumption reduction is 
appreciable. 
In the commercial version of the invention, the converter 10 was located 4 
inches inwardly of the window glass. The slats were made of heavy gauge 
aluminum, which was 0.025 inches thick and which had high thermal 
conductive characteristics. The slat width was approximately 3 inches and 
was curved to an arcuate profile to provide proper focus with the sun at 
varying winter season angles. The arcuate slat profiles were held fixed at 
an appropriate angle, so that the sun's rays would impinge perpendicularly 
to corresponding positions on the slat curve to collect solar energy most 
efficiently. In performance tests the absorber slat temperatures have 
ranged from 55.degree. nightroom temperature to 130.degree. daytime 
temperature during the lowest insolation in December. The device which was 
motionless and silent served to increase the room temperature from 
55.degree. to 78.degree. during the sunlight hours. This occurred while 
the outdoor temperature ranged from 8.degree. to 24.degree. with a 24 
miles per hour wind velocity. 
It should be pointed out that, if it is necessary to cancel the solar 
collection action at any time, the slats are easily detached and stacked 
on the window sill, or a conventional fabric window shade may be drawn to 
closed position between the collector and the window. 
It can be seen, therefore, that the present invention provides an improved 
collector of solar energy with efficient conversion to thermal energy and 
with effective distribution of the heat within the room or building by 
means of natural convection. It also provides an improved absorber slat 
assembly that is spaced to allow natural light to pass through to 
illuminate the room interior and also to permit vision outwardly by 
persons inside of the room, even while the converter is functioning. It 
also has the advantage of low cost, simple assembly, easy retrofit, 
optimum durability, fire safety, and aesthetic appeal with a minimum 
amount of maintenance. 
It is obvious that minor changes may be made in the form and construction 
of the invention without departing from the material spirit thereof. It is 
not, however, desired to confine the invention to the exact form herein 
shown and described, but it is desired to include all such as properly 
come within the scope claimed. 
The invention having been thus described, what is claimed as new and 
desired to secure by Letters Patent is: