Solar system having improved heliostat and sensor mountings

This specification discloses an improvement in a solar system having one or more collectors for receiving and using radiant energy from the sun and at least one and preferably a plurality of respective reflector means for reflecting the radiant energy onto the collectors. The improvement is characterized by having each reflector in the form of a heliostat that can be moved to maximize the radiant energy reflected onto its collector, driving motor for so moving each heliostat; firmly anchored support structure carrying each heliostat; and sensor connected by suitable controls with each drive motor for so moving each heliostat; the respective sensor being mounted on the same support structure as the heliostat and aligned in a straight line from the heliostat to its collector. With this construction, the sensor does not require an expensive and firmly anchored separate support structure to prevent receiving small surface movements different from those received by the heliostat.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to solar systems employing reflectors for reflecting 
radiant energy onto one or more collectors. More particularly, this 
invention relates to an improvement in the solar system having the 
reflectors and collector in which the expense of installation is reduced 
without sacrificing precision and efficiency. 
2. Background of the Invention 
The prior art has seen the development of a wide variety of systems for 
producing useful work. One of the systems that has long been used but has 
been recently reactivated with a special emphasis is the use of solar 
energy. The systems for using the solar energy are referred to as solar 
systems. These systems have taken a wide variety of forms ranging from the 
photovoltaic cells that convert the radiant energy directly into 
electrical current, such as used in space probes, space vehicles and the 
like; to the more mundane systems converting the energy to heat for 
heating a fluid for use in generation of power. Regardless of which system 
is employed, it is generally conceded to be beneficial to employ a 
concentrating principle in which the sun's radiant energy from a much 
larger area than the collector, per se, is directed, or focused, onto the 
collector that uses the radiant energy. 
In a typical installation at the surface of the earth, a collector may be 
mounted on a tower or the like and reflectors spaced thereabout for 
directing radiant energy onto the collector. In order to maximize the 
radiant energy directed onto the collector, a sensor has been employed 
intermediate the collector and the reflector so as to detect when the sun 
rays depart from the most direct and concentrated reflection of the 
radiant energy onto the collector. Typically in such an installation, the 
reflector was mounted on one support structure, such as a post that was 
firmly anchored in the surface of the earth or the like. In order to 
resist receiving minor surface movements, the sensor then had to be 
mounted on a similarly rigidly anchored support structure. Since the 
anchors had to go down to subsurface layers to resist the surface 
movements that might be spurious or different one from the other, the 
second support structure was expensive. 
Accordingly it can be seen that the prior art was not totally satisfactory 
in providing an economical combination of reflector, collector, sensor and 
their respective supports. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of this invention to provide a solar system 
that is more economical than the prior art systems, yet does not sacrifice 
efficiency. 
It is a specific object of this invention to provide a solar system in 
which there is employed a collector for using the radiant energy, a 
reflector for reflecting radiant energy onto the collector, a sensor for 
maximizing the reflected energy and support for the respective elements of 
the system that was more economical than the prior art and that resisted 
receiving different surface movements by the sensor and reflector. 
These and other objects will become apparent from the descriptive matter 
hereinafter, particularly when taken in conjunction with the appended 
drawings. 
In accordance with this invention, there is provided an improvement in a 
solar system located on the surface of the earth exposed to the sun and 
including at least one receiving collector for receiving and using the 
radiant energy from the sun and at least one reflector means for 
reflecting the radiant energy from the sun onto the collector. The 
improvement comprises having the reflector in the form of a heliostat that 
can be moved to maximize its reflected radiant energy onto the collector; 
means for moving the heliostat to maximize the radiant energy; a support 
structure carrying the heliostat; the support structure being anchored 
firmly in the surface; and a sensor connected with the means for moving 
the heliostat for maintaining the maximim radiant energy onto the 
collector; the sensor being mounted on the support structure and aligned 
with a straight line from the heliostat to the collector and disposed so 
as to sense reflected radiant energy from the heliostat and respond by 
generating an error signal when the light received is not at its maximum 
and not uniform over the total sensing surfaces of the sensor; the sensor 
not requiring an expensive, firmly anchored separate support structure to 
prevent receiving small surface movements different from those received by 
the heliostat.

DESCRIPTION OF PREFERRED EMBODIMENTS 
It is immaterial in this invention whether the collector be of photovoltaic 
cells for converting the radiant energy directly to electricity or 
converting the radiant energy to heat, as for heating a fluid that will 
ultimately be used in the generation of power. The latter application is 
easily understood and this invention will be described in this context. 
Referring to FIG. 1, the solar system 11 includes a collector 13 for 
receiving and using the radiant energy from the sun, shown by the ray 15. 
The solar system 11 also includes at least one reflector means 17 for 
reflecting the sun's radiant energy, shown by ray 19, onto the collector 
13. Ordinarily, in the prior art, the collector 13 is supported on a tower 
21 to facilitate receiving the radiant energy from a plurality of the 
reflector means 17 spaced about the collector 13. 
The collector 13 may be a steam generator or the like for heating a fluid 
directly; for example, to convert water into steam to be used in passing 
through turbines for generating electricity by rotating generators or the 
like. Alternatively, the collector 13 may absorb the radiant energy and 
heat an oil or other high boiling liquid that will be passed in heat 
exchange relationship with the water to generate the steam. How the 
collector 13 uses the radiant energy is relatively immaterial to this 
invention. 
The tower 21 is structurally adequate to hold the collector 13 against the 
ambient winds and the like. Ordinarily, the tower 21 will comprise linear 
structural elements that are connected together to form a rigid unitary 
mast that is anchored in suitable foundation 23. As indicated 
hereinbefore, the collector 13 may be merely a module for heating an oil 
or the like so as to require less structural support. A great deal depends 
upon the temperature that is desired to be obtained in the collector 13. 
These temperatures may range from as low as about 200 degrees Fahrenheit 
(93.degree. C.) to as high as 1500 degrees Fahrenheit (816.degree. C.). Of 
course, the design will vary significantly between these extremes. 
It is ordinarily when temperatures in excess of a few hundred degrees 
Fahrenheit is desired that it becomes imperative to try to maximize the 
radiant energy absorbed, or reflected onto the collector 13. In such 
instances, respective sensors 25 are disposed intermediate the reflector 
means 17 and the target, collector 13. The sensors 25 detect when the most 
intense radiation for a given condition is being received. The sensors may 
comprise any of those commercially available. It has been found in this 
invention advantageous to employ dual tube sensors having photovoltaic 
cells arranged in matched pairs at the base of an elongate tube. The open 
end of the tube faces directly into the reflector means 17. As long as 
there is uniform lighting on the cell surfaces, the cells are matched and 
no error signal is generated. Once the sun moves such that there is non 
uniform lighting or shadowing of one or more of the cells, an error signal 
is generated, causing the reflector means to be positioned at a new angle 
to effect best focusing of the sun's rays onto the collector 13. As will 
be appreciated, it is critical that the sensor 25 always be correctly and 
carefully aligned with the center of the reflector means 17 and the target 
13. 
Consequently, in the prior art, the sensor 25 was as firmly mounted in the 
surface 27 as was the reflector means 17. Expressed otherwise, the support 
structures 29, 31 and foundations 33, 35 were both firmly anchored 
sufficiently deep that both the sensor 25 and the reflector means 17 
receive the same movements and there were no spurious surface movements 
received by either one alone. Ordinarily, each supporting structure 29 and 
31 comprised relatively large steel posts designed to resist movement by 
ambient winds and the like. Respective foundations 33 and 35 were formed 
of concrete and penetrated into the subsurface layers of the earth deeply 
enough to resist spurious movement of the surface layers, as from 
expansion of clays or the like when wet by rain. 
While only the pair of the diametrically opposite reflector means and 
sensors are illustrated, it is to be remembered that any desired array of 
the reflector means can be employed with respect to one or more collectors 
13, 13a. For example, the reflector means may be placed in an array 
throughout 360 degrees around each collector. 
Referring to FIGS. 2-4 for the improvement in accordance with this 
invention, the reflector means 17 is in the form of heliostat 37 with both 
it and the sensor 25 being carried by the supporting structure, or post, 
39. The post 39 is, in turn, carried by the foundation 41. Ordinarily, a 
plurality of heliostats are employed for reflecting the radiant energy 
onto a given respective collector 13. The respective heliostats may have 
any suitable dimension and form. For example, the heliostat may comprise 
an arcuate reflector means, such as a mirror, to convert the substantially 
parallel rays from the sun into focussed rays that converge on the 
collector 13. As illustrated, each heliostat is about 24 feet (9.7 meters) 
tall and about 20 feet (6.1 meters) wide on each single post structure. 
Focusing is obtained by aligning a plurality of relatively small; for 
example four feet by four feet (1.2 meters by 1.2 meters) flat facets into 
a Fresnel approximation of a spherical concentrator. Each facet has a 
reflecting surface of a mirrored glass plate for utmost reflectivity. The 
mirroring may be of conventional design, such as aluminum or silver. 
Second surface silvering has proven to be the most durable and best 
reflective material found. The making of the individual flat facets 
involves only state of the art technology and need not be detailed herein. 
As can be seen in FIG. 4, the illustrated facets 43 are arranged in rows 
and columns and are supported by structural elements 45 in a unitary array 
of 26 facets. The heliostat 37 has a central reflector 47. The heliostat 
37 has a slot 49 below the central reflector 47 so as to be pivoted 
without hitting the post 39 or connected elements. The heliostat 37 is 
light in weight. Accordingly, the structural elements are preferably 
formed of a light weight metal such as aluminum, magnesium, or the like, 
although steel is frequently employed because it is high strength. The 
facets 43 are affixed to the structural elements by any suitable means, as 
by bonding or the like. Preferably, the reflecting area is maintained at 
or near the maximum. 
As illustrated, the heliostat 37 is movable pivotally about a horizontal 
axis through the central reflector 47 to accommodate, primarily, the daily 
path of the sun. If desired, the heliostat 37 also may be radially movable 
about a vertical axis passing through the central reflector 47. The radial 
movement is through a limited arc to accommodate the 231/2 degrees 
variance between the sun's path during the different seasons. 
The means for moving the heliostat to maximize the radiation towards the 
collector 13, includes a motor 51 and worm gear drive 53, serving as an 
elevation drive means for pivoting the heliostat about its horizontal axis 
through the central reflector 47. The worm gear acts on the circular 
pinion 55 in attaining and holding a desired angle. The worm gear serves 
as a braking means so as to resist movement of the heliostat once a given 
signal is obtained. 
If the heliostat is to be rotated about the vertical axis through the 
central reflector 47, a suitable motor, gear reducer and rack 57, FIG. 2a, 
may be employed engaging a circular pinion 59 for effecting the rotation 
about the vertical axis. 
The respective motors, worm gear drives, gear reducers, racks and pinions 
are all well known and are conventionally available so need not be 
detailed herein. 
With respect to the foregoing, it is sufficient to note that the slot 40 
enables the heliostat to be pivoted or rotated through its limited arc 
without striking the sensor 25 or its cantilever mounting member 61. 
Specifically, the sensor 25 is a dual tube sensor such as described 
hereinbefore employing two sets of photovoltaic cells each with the cells 
matched to balance each other when each are receiving the same intensity 
of light. In the event that there is a moving of the sun without 
corresponding movement of the heliostat, one of the cells suffers a loss 
of intensity. Consequently, an error signal is generated that causes the 
motor to pivot the heliostat 37 to bring the intensity of radiation back 
to its maximum and achieve a uniform distribution of light over the 
photovoltaic cells. The respective cells of a matched pair indicates the 
nature of the correction to be made; for example, greater tilting of the 
heliostat. The use and connection of the sensor, controls and motor driven 
means is conventional and need not be delineated in detail herein. The 
conductors from the sensor 25 are usually run interiorly of cantilever 
mounting member 61. 
The sensor 25 is carried by the cantilever mounting member 61; which in 
turn, is affixed, as by welding, to the post 39. The cantilever mounting 
member 61 is structurally adequate to retain the sensor 25 in place 
against ambient winds or the like. When the conductors are run interiorly 
of the member 61, it is tubular with passage through its interior. 
Otherwise, member 61 can be of any desired shape. Preferably, both the 
cantilever mounting member 61 and the sensor 25 resist destructive effects 
of weather, such as, the destructive effects of sun, rain, ice or the 
like. This cantilever mounting member 61 may be affixed by any suitable 
means to the post 39 as long as it is structurally adequate to move in 
unison with the post 39 and heliostat 37, and not be moved by other forces 
such as wind or the like. It is readily apparent that, as closely mounted 
as the sensors are to the heliostat, small movements are reflected as 
large movements of the reflected rays by the time the radiant energy is at 
the distance of the collector 13. 
The heliostat sensor assembly will survive earthquake environment 
experienced in the continental United States. Reattainment of performance 
following earth movement is achieved with minor aiming adjustments. The 
mirrors are readily maintained because of the flat unstressed shape of the 
glass. 
In operation, the collector is installed in the conventional fashion. The 
foundation 41 is poured and the post 39 attached thereto, as by bolts 
through a flanged plate or the like. The heliostat 37 is pivotally mounted 
on the top of the post 39 with its slot 47 disposed about and encompassing 
the post 39. The respective means for moving the heliostat are 
interconnected with the suitable gears and pinions meshing. The sensors 25 
and the cantilever mounting members 61 are then emplaced so as to detect 
the rays aimed at the collector 13. Thereafter, suitable controls are 
connected and activated to pivot the heliostat 37 to the desired angle for 
the sun at any given point and calibration of the sensors 25 is made. 
As a consequence of the error signals, the heliostat is moved as the sun 
moves in its trajectory across the heavens to maximize the radiant energy 
reflected onto the collector 13 for a given heliostat 37. If desired, the 
elevation drive means may be connected to a timer or the like to bring the 
heliostat back into its initial position for receiving the morning rays of 
the sun. Corrections may be made by manual override control in the event 
of a malfunction. 
The conventional controls may be employed for testing the circuits of the 
sensors and or the control circuits of the respective motors. 
It is sufficient to note that by the respective one or more movements of 
the heliostat 37 about its respective axes through the central reflector 
47, the radiant energy directed toward the collector 13 is maintained at a 
maximum and the efficiency is maintained near the maximum. 
One of the particular advantages of this structure is that the heliostat 
may be oriented horizontally, face down for minimum wind resistance from 
any direction in the event there is a storm or the like. Moreover, the 
effects of a storm on the post 39 are reflected in the same relative 
positioning of both heliostat and sensor 25 such that only minor 
alteration is required in the events there is movement. This is in 
contrast to the prior art where movement of the heliostat frequently could 
have required major work to correct the orientation of the heliostat post 
or the separate post containing the sensor 25. 
From the foregoing it can be seen that this invention achieves the objects 
delineated hereinbefore. 
Although the invention has been described with a certain degree of 
particularity, it is understood that the present disclosure is made only 
by way of example and that numerous changes in the details of construction 
and the combination and arrangement of parts may be resorted to without 
departing from the spirit and the scope of this invention.