Sun-light-redirector useful in day-lighting, photo-voltaics and solar heating
Kind Code:

An automatic sunlight redirector comprises of a device which redirects sunlight to a place of user's choice. This is a universal model and does not need data and microprocessor to track the sun at different latitudes, nor does it need any computer to calculate the angle of reflectance. This device works on principle of arranging incident sun-ray, target-line and the mirror-axis as sides of an isosceles triangle and is realized by the devices of sun-tracking director-bar, a slide fitted on this director-bar, and a groove on the mirror-axis pipe/bar (5) for free movement of the director-bar (10) which not only tracks the sun but continuously adjusts the position of the mirror such that the light is reflected on the fixed target. The declination-setter (8) and time-setter (15) track the daily changes in the declination of the sun and the length of the day respectively.

Shukla, Arun Gomtishanker (Jabalpur, IN)
Application Number:
Publication Date:
Filing Date:
Primary Class:
Other Classes:
126/569, 248/176.3
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Primary Examiner:
Attorney, Agent or Firm:
I claim:

1. The device of sunlight-redirector wherein the novel technique of redirecting sunlight on a fixed target is achieved by arranging i) direction of incident sun-ray ii) the direction of the target and iii) the axis of the moving mirror as three sides of an isosceles triangle.

2. The sunlight redirector device of claim 1 where two arc-couples holding the mirror, make possible the movement of target-arm in practically all directions, and yet maintain the same distance between director-bar-pivot and the mirror-arm-pivot, thereby making it useful for reflection of sunlight in any direction without making any change whatsoever in the machine.

3. The device of claim 1 where the said arrangement of isosceles triangle described in claim (1) above is achieved by the combination, the sizes and the placing of following components:— a) the Sun-tracking director-bar, fitted on and moved by the polar-axis-bar, being one of the equal sides of the isosceles triangle which occupies the position of sun-ray, b) the virtual line, joining pivot of the director-bar and the pivot of the mirror-axis, equal in length to the length of the director-bar, occupying the position of the second equal side of the isosceles triangle and c) the mirror axis forming the third line of the isosceles triangle.

4. The device as claimed in claim 1 where i) a slide fitted on the sun-tracking director-bar, ii) the groove on the mirror-axis pipe/bar for holding the slide and allowing its free movement, iii) the two mutually perpendicular axles for the mirror-axis-bar ensuring its free movement in two plains, make possible the working of technique claimed in claim (1) by (i) allowing free movement to the director-bar to remain sun-oriented, (ii) adjusting the mirror-arm to different positions when moved by the director-bar and (iii) maintaining the isosceles character of the triangle formed by the three arms as narrated in claim (1) and claim (2) above.

5. The sunlight redirector of claim 1 where the adjustable circular arc holding polar-axis-bar makes possible setting of polar-axis-bar parallel to the earth-axis at all places of different latitudes, and by this makes the machine globally useful without any change in the machine, and at the same time maintains the same distance between the director-bar-pivot and the mirror-arm-pivot.

6. A declination-setter which sets the angle of declination of the sun-tracking director-bar on the polar-axis-bar exactly equal to the angle that the Sun has with the axis of the earth on the day of operation by virtue of the specific size, designing, and respective functions of the components: declination-bar, clamp, coning-bar, circular-trip, eccentric positioning of the circular-strip and calendar-disc, and the timer.

7. A time-setter which sets position of the polar-axis-bar with the help of its components; time-bar, time-discs, and the timer such that when it starts working on the alarm of the clock, the increase or shortfall in the length of that particular day i.e. the time elapsing between last and the coming noon—commonly ascribed to fast or slow movement of the Sun or alternatively of the earth—is neutralized by the shifting of the time-point caused by the movement of time-disc with uneven radius—specifically designed on the basis of actual experience to bring about this effect in one version, and with the help of a programmed timer to start operation at different time on each day while the starting point is fixed according to the desire of the user.



This application is based on, and claims the priority of, PCT International Application No. PCT/IN2004/000368 Filed on Nov. 29, 2004.


This invention of automatic sunlight redirector comprises of a device which redirects sunlight to a place of user's choice by arranging incident sun-ray, target-line and the mirror-axis as sides of an isosceles triangle.


In the last three decades solar energy has been recognized as a potential source of energy for various purposes. The two known manifestations of solar energy—namely light and heat are being converted in to useful energy. Light is converted in to electricity through photo-voltaic cells and heat is either being used for heaters or for generating electricity through thermal power plants.

It is common knowledge that photo-voltaic power generation in spite of all its advantages is very costly option. For this reason, the progress in this area has not been quite impressive.

In countries between 45 degree north and 45 degree south latitude, sunlight is quite rich and it can be harnessed for many purposes including lighting of the interiors of the buildings. This is done through passive reflectors and glazed windows/roofs. Some active sun-tracking devices have also been invented which can send light into the interiors. For redirection of sunlight into interiors very accurate sun-tracking is essential. However, as yet no device has been invented which can help harnessing solar energy to fuller extent at affordable price for individual users for domestic purposes or for small requirements. The cost of machines is high because movements of the sun during the day and during the year are very complicated and defy any simple mathematical formulation capable of being translated into mechanical device, and therefore help of costly computers and sensors etc. have to be taken for sun-tracking.

Importance of Sun-Tracking

Solar energy begins to shower on the earth as soon as the sun appears on the eastern horizon. Its intensity increases until noon, then it begins to decrease until sun sets in the west. This variation is due to angularity of the sun-beams in relation to the surface of the earth. In the morning the sun-rays have to pass through greater layer of air and dust particles; also each unit area of sun-beam falls on larger area of earth-surface due to this angularity.

While nothing can be done to reduce the layer of air and dust, human effort can help in catching larger amount of sunlight by keeping the receiver perpendicular to the sun-rays. This activity of moving objects according to the movement of the Sun is known as sun-tracking. Owing to its importance various types of sun-tracking devices have come into existence.

By sun-tracking, not only the output of the system increases but also some activities like producing high temperature become possible.

Problems in Sun-Tracking

Sun tracking is very complex affair for following reasons:

1) Sun changes its route everyday throughout the year.
2) Sun takes different time every day during the year to travel from eastern horizon to western horizon.
3) Both the route and the timing vary from place to place even on the same day of the year. Apart from these simple problems, there are some much more complex problems which are narrated later.

Therefore no simple mechanical device could be designed so far which could help in following the route of the sun at every place in the world—this has precluded large scale production of a mechanical device which could be universally useful.

For sun-tracking the object e.g. a mirror, sought to be sun-oriented has to be moved in the direction of the sun. This can be done by fixing the mirror on a machine moving on north-south axis and rotating from east to west. The object is oriented towards sun at sunrise. Then with the climbing of the sun the machine is to be rotated from east to west.

When such a simple rotation is given, it is observed that the mirror does not follow the route as explained below because except on equator the sun moves not only westward but also north-south-north-ward also.

A probable solution is to move mirrors slowly towards south also, from sunrise to noon. So there is a necessity for following information, and a device to achieve this:

1) Angle of deviation from east at sunrise.
2) Angle of elevation of the sun at noon.
3) Time taken by the sun to traverse from horizon to reach noon position.
4) A device to move the mirror both westward and southward at the required speed calculated from the above three information.

But unfortunately such arrangement will not work on next day because all 3 factors namely:

1) Angle of deviation from east at sun rise,
2) Angle of elevation of the sun at noon and
3) Time taken by the sun to traverse from horizon to reach noon position, will be different every day. So the information for all the 365 days of the year have to be at hand and the mirror-rotating device has to be programmed for these different movements and for different timings.

This is a horrible work. Unfortunately, even if such a machine is built, it will be useful only for that particular place. It will not work at a place with different latitude. For this reason no device could be invented which can have simple function and universal application. Therefore, electronics-supported costly systems were opted by large-scale users of solar energy and nothing could be done for small users.

One can imagine the problem of reflecting light on a point of one's choice when sun-tracking itself is a tough task. This is so because for reflecting light, not only the sun is to be tracked but the mirror has to be moved such that the light is always reflected on the desired place while the angle of incidence and reflectance are changing every moment as shown in FIG. 5.

Prior Art

As mentioned earlier, owing to the complexities of the movement of the Sun no mechanical device could be built which could track the Sun and redirect sunlight on desired target on each day of the year and at each place in the world at a price affordable to a small-scale user.

With the advancement of Science and Technology and efforts of inventors, many systems have come into existence for reflecting light on user's choice. This is being done today with the help of computers. Obviously these systems are very sophisticated and costly, therefore they are not becoming popular. There are also some machines which can send sunlight into the kitchen for cooking. These machines have a parabolic mirror, which rotates on polar-axis and sends light along this axis into the house. They cannot send light to any point of users' choice. This limitation coupled with high cost and unsuitability to lifestyle has precluded its acceptability to the users. This machine can be used for daylighting also but with the above limitations.


The problems mentioned above have been solved by the device of the present invention. The advantages of the machine are as follows:

1) It can be operated manually, through torque of spring or by electricity.
2) It is a universal model.
3) It can reflect light on any point of users' choice, thereby making possible—solar-cooking inside the kitchen, heating and day-lighting of the buildings etc. This can also be useful for increasing the output of the costly photo-voltaic panels by using multiple reflectors and supplying greater amount of sunlight on the panels. It can also help for its security against winds etc. as the panels can be housed inside lock and key while receiving light through a window etc.
4) Its functioning is very simple and with a very limited training one can be able to install, operate or repair the machine.
5) Its cost is low.


The present invention has been devised to reflect sunlight at a point of user's choice for daylighting, heating etc. This has two parts namely sun-tracking part and the reflector part. Sun-tracking part is based on polar-axis tracking with novel features to make it a completely automatic system.

The present invention has a declination-setter which automatically sets the sun-tracking-bar according to the declination of the sun for the day of operation, and thereby does away with the two-axis tracking to cope with the north-south-north movement of the sun during the day or the trouble of adjusting for sun-declination in the polar-axis tracking.

The present invention has arrangement for starting of the machine at a particular time of the day through time-setter. This has advantage over the sensor-based systems, which have problem if the morning is cloudy and the light lining is far away from the actual point of sunrise. This has advantage of not only cost but also of simplicity over the computer-data-software based systems because their data and software are place-specific; also in the present invention there is absolutely no necessity of calculating angle of reflectance for the mirror—the machine performs both the jobs simultaneously—the sun-tracking and the redirection of sunlight on the desired target area.


FIG. 1 generally illustrates a side perspective view of the light machine of the present invention.

FIG. 1a generally illustrates a side perspective view of a declination-setter device of the light machine.

FIG. 2 generally illustrates a side perspective view of a detailed portion of the light machine.

FIG. 3 generally illustrates the movement of the sun around the Earth.

FIG. 4 generally illustrates the change of declination of the sun at local noon.

FIG. 5 generally illustrates the change in the angle between the sun and the target.

FIG. 6 generally illustrates the time-disc mover of the present invention.

FIG. 7 generally illustrates the effect of a ray falling on the mirror of the present invention.

FIG. 8 generally illustrates the arrangement for reflection of light to the target area.

FIG. 9 generally illustrates the arrangement extension of the size of the mirror from the B to the F position.


FIG. 1.

This is perspective of the complete machine. The parts that need elaboration are separately shown in FIGS. 2 and 6.

01 Stand—to support the whole structure.
02 Base pipe—to hold revolving arc couple (3) and the shaft (7-A)
03 Arc-couple—revolving on pipe (2). Free to move 360 degree, thereby, together with arc-couple (β) makes possible to move mirror in any direction and even then maintaining same distance between the pivot of director bar (10) and pivot of mirror-arm (12).
04 Axle—giving free movement to mirror arm (12) caused by sliding director-bar (10) in north-south-north direction when in operation.
05 Pipe-holding axle (5-A). Axle (5-A) fitted inside pipe (5) helps to give free movement to mirror-arm (12) caused by movement of director-bar (10) in the east-west direction when in operation.
06 Arc-couple—fitted on arc couple (3) with nut-bolt for adjusting the position vertically in the desired direction.
07 Arc—made of two arcs and having gap to allow its placing on the supporting rod (7-A) such that the polar-axis-bar (9) can be placed on the position parallel to the axis of the earth.
08 Declination setter—This device automatically sets the director-bar according to the declination of the Sun on that day. It is described in details in the description of the FIG. 2.
09 Polar-axis-bar—This is a rotating bar fitted on arc (7) on free bearings. This has to be placed parallel to the axis of the earth. This position is attained by bringing the rotating bar in geographical north-south line (alternately called meridian line) and then by moving it in vertical plain by an angle equal to the latitude of the place of operation, e.g. at a place at 30 degree north latitude, the northern end of rotating-bar will have to be moved upwards by an angle of 30 degree in relation to horizontal line. Director bar—When adjusted by the declination setter for the date of operation, and moved by the rotating bar it remains sun oriented. And as the movement of the Sun has two components namely east-west and north-south-north, the director-bar also moves accordingly. By its movement the director-bar moves the mirror-arm (12) to a position that it reflects sunlight on the target-area. Slide—Either spherical or cylindrical, fitted on the director-bar and sliding on groove on the mirror-arm (12), it helps to move the mirror-arm (12) in east-west and south-north-south direction. Mirror-arm—Holds mirror and is moved by the slide (11) fitted on the director-bar (10). This has free movement in two directions because of free axles (4) and (5-A). Timer—Moves the rotating bar at a speed of one round every 24 hours. This starts working as soon as the alarm-clock sends the message to start operation and continues to move the polar-axis-bar (9) until the alarm-clock sends the message to stop and come back to the original position for the next morning. The original position for the next day would be different and would be taken care of by the time-setter. Orientation-Bar-disc—The bar of this bar-disc is virtually extension of the director-bar (10). It is to be fitted on the free end of the director bar (10) passing through the mirror-arm (12). There is a disc between the director-bar (10) and this bar. When the director-bar (10) is moved such that there is no shadow of this bar on the disc, it is ensured that the director-bar is sun-oriented. This helps in making the director-bar (10) sun-oriented if the machine is to start operation during any time of the day after installation or after repair of the machine. Time setter—It is attached with the arc (7) on a metal-plate. The user may fix the time for starting of the machine automatically with the help of this component and an alarm-clock (16). This time-setter is described in detail in the description of FIG. 6. Alarm-clock—This is an electronically programmed alarm-clock which sends the message to the timer (13) to start and end the working at a specified time everyday. The user has an option to program the starting and ending of the movement of timer-motor (13) as per his choice through electronic circuits {these circuits may be used to bring back the director bar (10) to the position of next day immediately after stopping of the timer at the end of the day).

FIG. 2.

This is declination-setter device for the director-bar described above as (10) in FIG. 1 and has following components:—

1. This is a rotating bar named as declination-bar fitted on a steel frame. There is a hole at the center of the bar through which passes another small bar. On this small bar a U-shaped clamp is fitted and on this clamp another bar is fitted which is connected on the other end with the circular strip (3) such that the circular movement of the strip (3) forms a cone of 23.5 degree having its vertex on the center of this declination-bar (1).

On this declination-bar (1) is fitted the director-bar described as (10) in the FIG. 1. When circular strip (3) is moved one full circle by movement of the gear (6) it gives all the angles to declination-bar (1) which the Sun forms with the earth axis during one year, and the director-bar thereby is adjusted to the position for each day of the year.

2. This bar connects the free moving clamp to the circular strip (3) and makes a cone of 23.5 degrees when rotated by the movement of the calendar-disc described in (6) below and may be named as coninq-bar.
3. This circular strip is a part of a virtual circle which is formed having its center on the center of the axis of the declination-bar (1). The bar (2) is fastened on this strip in a hole at a distance of 23.5 degree from the pivot of the circular strip.
4. This is a freely moving pivot-axle fitted through a strip which is fitted on the frame parallel to the rotating-bar (1). On one side of this pivot is fitted the circular strip (3) and on the other side is fitted another strip (5).
5. This strip has a hole on which a small nail is inserted, which nail is fitted on the toothed disc (6).
6. This is toothed disc fitted on a pivot that is eccentric in relation to the pivot (4) to the extent that its movement equal to 177.2 degree causes a movement of the strip (5) equal to 180 degree during one half of its movement, and in its second half of the movement its 182.8 movement causes 180 degree of the movement of strip (5). The movement of the strip (5) is caused due to fastening of the nail fitted in the gear-disc (6) and fastened on the hole of strip (5). This gear-disc is moved by a motor at a speed of one round every 365.25 days. This disc may be used as a calendar if suitably the dates are marked on the circumference of the disc; these markings can be useful for installation of the machine. Then this disc may be named as calendar-disc.
7. This is a motor for moving calendar-disc (6) at a speed of one round every 365.25 days.

FIG. 3

Shown in FIG. 3 is the movement of the earth around the sun

FIG. 4

Shows the change of declination of the sun at local noon

FIG. 5

Shows the change in the angle between the Sun and the target FIG. 6.

1. Timer—This moves time-disc-mover (2) at a speed of one round per year.
2. Time-disc-mover—This disc has marking for each day of the year and fitted on one side of the time-setter-plate (4) and fitted firmly with the time disc (3) with an axle passing through the base-plate (4). When moved by the timer it moves time disc through the common axle between itself and time-disc (3).
3. Time-disc—This has varying radius corresponding to each date of the time-disc mover.
4 Time-setter-base-plate—On this all components of time-setter except (6) and (7) are fitted.
5 Time point—This is a flat square shaped thick plate sliding on a groove fitted on time-setter-base-plate. It is so fitted that one of the two opposite corners touches the time disc (3) and on its other corner time bar (6) rests after the end of the day to begin working at the appointed time as per users choice. This point is shifted by the movement of the time-disc because of its varying radius for each day.
6 Time-bar—This is fitted on a co-axial pipe on the rotating bar numbered in Rg-I as (9) whose cross section is represented by (7) and which is fitted on that position of the rotating bar according to the desire of the user for the starting time of the machine.
7 This is cross section of the polar-axis-bar. FIG. 7-A shows the effect of a ray falling on the mirror
FIG. 7-B shows an isosceles Triangle ABC
FIG. 7-C, is an isosceles triangle ABC where sides AB and AC are equal.
FIG. 7-D shows the shift of position C in an isosceles triangle due to fixature of BA and sun orientation of AC.
FIG. 8 Shows the arrangement for reflection of light to target area
FIG. 9 Shows the arrangement extension of the size of the mirror from B to F position


The invention machine performs two operations, namely it tracks the Sun and it redirects sunlight on a fixed point throughout the day from where it can again be redirected to where it is needed. Obviously the invention machine has to be in two parts, one for sun-tracking and the other for redirection of sunlight. Since the sun-tracking part is subservient to the redirection system the redirection system is being described first.

Part-1: Redirection-System.

As narrated earlier the sun-tracking itself is a very complicated work and therefore computers have been put to service for the purpose. When the light is to be reflected/concentrated within the system a good sun-tracking system is sufficient because a concentrator can be fitted in the system which can be kept sun-oriented and the sun-rays get concentrated on the focal point of the concentrator. But when the light is to be reflected on a point outside the system the job becomes still tougher, because as shown in figure (5) angle of incidence of sunlight and therefore, the angle of reflectance also goes on changing every minute of the day and therefore this new factor is to be taken care of, in addition to locating the position of the Sun. Looking to the complexity of the problem, in the existing systems, help of computers is being taken.

The invention takes into consideration the principles of reflection of Light, basic geometry and the mechanics as explained below:—

1. Reflection of Light:

As per the principles of Optics when a ray falls on the mirror the angle between the incident ray and the reflected ray is divided equally by a perpendicular on the mirror at the point of incidence as shown in the figure (7-a). 2. Principles of Geometry: As per simple principles of geometry, in an isosceles triangle, the line which divides the angle between equal sides equally, is perpendicular on the third side as shown in figure (7-b).

3. Combining 1 and 2 Above:

The combination of these two principles by which is devised a formula for reflection of ray of light whose direction is known and the direction of the target is also known as described below.

Shown in figure (7-c), is an isosceles triangle ABC where sides AB and AC are equal. If a ray of light CA is to be reflected in the direction AB then the mirror MR will have to be placed such that a perpendicular on the mirror at point A divides angle BAC in to two equal parts—as per the laws of reflection quoted above. In this position all the rays coming parallel to CA will be reflected in the direction parallel to AB. Now if the position of the mirror is shifted to the position of BC, even then all the rays parallel to the line CA will be reflected in the direction parallel to AB. This will happen so because AD is perpendicular on BC also because ABC is an isosceles triangle, and therefore line MR and BC are parallel to each other. So is achieved the formula that if the rays are coming in the direction parallel to one of the equal sides of an isosceles triangle and they are to be reflected towards the direction parallel to the other equal side of the triangle then the mirror has to be placed along the line parallel to the third side of the triangle, or the mirror may even be kept along the third line itself.

Now, coming to the application of the above formula what is to be achieved is that, the light coming from the Sun, which is changing its position every moment of the day, is to be reflected. Therefore, the point C will go on shifting its position because AC will always be sun-oriented, whereas the line BA will always be fixed as a fixed target to reflect light upon. When CA will be shifted, C will occupy some other position, say E7 in the space, which will not be coplanar with our triangle ABC as shown in figure (7-d);

therefore to be sure that our system continues to work, it must be ensured that the mirror is brought along the line BE so that all the three lines continue to be coplanar. It is also to be ensured that the new triangle ABE continues to be isosceles and the rays coming from the Sun are reflected along the direction parallel to AB—our target.

Therefore the following arrangement must be created where:

1) Line AB is fixed,
2) Lines CA and AB maintain their original length, and still they are moveable on points A and B respectively so that ever changing position of the Sun (C)—and thereby ever changing direction of CA can be kept pace with. Also it is ensured that CA be always kept coplanar with the line AB.
3) The isosceles character of the triangle ABC is maintained—by keeping the length of CA and AB same, while the length of the line BC goes on changing due to change in the angle BAC as shown in figure (7-d). (This change in the angle between the Sun and the target can be seen in the FIG. 5)

Application of Mechanics and Making of the Invention Machine.

(This is only an explanation how the above technique has been applied, the actual design is narrated later.)

Now to realize what has been narrated just above in paragraphs 1, 2 and 3 three bars occupy the positions of the three sides of our triangle ABC. For convenience the name of the components are designed on the basis of above principles.


Please see figure (8):
1) Sun-tracking bar will occupy the position of the line CA and may be named as SUN-ARM,
2) Bar holding the mirror will occupy the position along the line BC and may be named as MIRROR-ARM,
3) At the point B, mirror will have its pivot and may be named as MIRROR-PIVOT,
4) Sun-tracking bar—SUN-ARM—will rotate on point A as its pivot, therefore let us name this point A as SUN-ARM-PIVOT.
5) Bar occupying the position of the line AB will be oriented towards target and may be called TARGET-ARM.


Now following arrangements are to be made as shown in FIGS. 8 and 9:

1. Since the Sun will go on moving and the position of C will go on changing and therefore the magnitude of the angle BAC will also change during the day, therefore the Mirror-arm must be sufficiently long to allow all possible locations to point C after knowing the longest angle which the sun-arm may bear with the target-arm. Also the mirror-arm must have sliding-space on which the sun-arm will slide for different locations of C. 2. Target-arm must be oriented towards the target and then must be fixed securely on a base to ensure that movements of sun-arm and mirror-arm do not disturb its fixed position. The target-arm must also have on one end of it a pivot for the mirror-arm, and arrangement to allow the movement of mirror-arm both ways—one in the circular direction along the circumference of the target arm and the other in the plane of sun-arm and target arm because the Sun will move not only east-west but also north-south-north; this north-south-north movement will appear in the form of up and down movement of the Sun. For this reason the target-arm must also have on the other end a pivot for the movement of sun-arm both ways to adjust for all positions of the Sun during the day.
3. The sun-arm must have some arrangement so that while it slides on the mirror-arm, yet it keeps the mirror-arm moving so that the isosceles triangle of the three arms continues to exist.

If the above arrangements are made our system is complete for reflection of light on target area as shown in FIG. 8.

However, if the size of the mirror is equal to only BC, then reflected light will keep changing the position and the target will not be fully illuminated at any point of time. Therefore, there must be an extention of the size of the mirror from B to F position as shown in FIG. 9.

(Also the size and shape of illuminated area will go on changing and therefore size and the shape of the mirror should be such that the whole target area is always illuminated. An elliptic shaped mirror would be preferable, as it would illuminate nearly a circular area throughout.) Part-2: Sun-tracking system.

As narrated above in the description of the Redirection System would require a SUN-ARM—a bar—which should be sun-oriented throughout the day. This is realized in the present invention through a perfect tracking system, which provides solution for all the problems unsolved so far, through invention of new devices of declination-setter and time-setter as described herein below.

The present sun-tracking system is based on polar-axis tracking. Polar-axis tracking is based on the principle derived from following phenomenon:—

The earth moves around the Sun with a tilted axis and completes one round in a year. Because of the revolution of the earth around the Sun, position of the earth-axis in relation to the direction of the Sun undergoes change everyday which results in the change of declination of the sun at local noon as shown in FIG. 4.

Now let us imagine that a bar is placed parallel to the axis of the earth—let us name this as polar-axis-bar and it is rotated such that its direction and speed neutralize the rotation of the earth. Then, if a second bar is fitted on this bar, and then this second bar is once oriented towards the Sun, this second bar will remain sun-oriented throughout the day because the said movement of the polar-axis-bar neutralizes the movement of the earth by moving from east to west (while the earth rotates on its axis from west to east). On the basis of this principle polar-axis tracking is done.

However, the next day, the second bar, let us name this as director-bar, will have to be moved north or south depending upon quantum of the shift of the sun. This is not a simple task The declination of the sun is uneven during the year. The difference is very vast which can be seen as follows:—

Period. Declination-Change (Northwards)
March 22 to April 22-12 degrees April 22 to May 22-8 degrees May 22 to June 22 3 degrees

Since this uneven change in declination has evaded any mathematical formulae, the problem has also evaded mechanical solution. Therefore, the scientists have opted sensor/computers etc for the purpose. The present inventor has solved this problem through his invention of declination-setter described later herein.

(For changing the position of the director-bar the inventor in his earlier invention—application 559/mum/2002 dtd.26 June 2002—solved this problem by using a calendar-arc on which there was marking for fixing the director-bar. The director-bar could be fixed for the date of operation manually, or through an electronically programmed motor. The calendar-arc was devised because the declination of the Sun changes unevenly as described below, and evades any mathematical solution which could be translated into a mechanical device.)

There is another problem in tracking the Sun. The movement of the sun cannot be synchronized with our earth-clock even when polar-axis sun-tracking is opted. This is so because the length of the day i.e. time elapsing between two local noons is not always 24 hours. The variation can be as much as nearly one minute. The cumulative effect of this variation over a period of time is too much; the earliest local noon at any place comes at 11-44 a.m. and the latest at 12-14 p.m.—a difference of half-an hour. This phenomenon is known as analemma-curve effect. This variation also being uneven during the year, also evades any mechanical solution. This problem has been solved through time-setter in the present invention. Inventor has invented these new components which ensure working of the machine automatically through-out the year and there is no need of adjusting the director bar for each day. The innovation is useful for all sun-tracking systems based on polar-axis tracking. These devices are described as below.

Declination Setter:

The device to set declination has been named as declination-setter. The mechanism is devised on the basis of following facts and imaginations:—

(Please see FIG. 3)

As narrated above the earth moves around the Sun with a tilted axis at 23.5 degree, and completes one round in 365.25 days.

Let us imagine that the position of the Sun and the earth are interchanged. By interchanging the position of the sun and the earth—the earth static and the Sun revolving around her—it will be found that different angles of sunrays are created on the earth-axis during the revolution of the Sun around the earth.

Let us further imagine, as shown in the third drawing of the FIG. 3, that the Sun is stopped at a point and then the earth-axis is rotated around a perpendicular on the ecliptic—an imaginary plain in which the earth revolves around the sun during the year—then, all those angles will be created between the sunray and the earth-axis which are created by the (imaginary) revolution of the Sun around the earth. In this rotation of the earth axis it can be seen that a cone of 23.5 degree will be created by this rotation.

Now if the positions of the earth-axis and sunrays are interchanged i.e. instead of rotating the earth-axis against a fixed sunray, the sunray is rotated on the fixed earth-axis such that the sunray creates a cone of 23.5 degree as achieved by the rotation described above, one gets all the angles which were created by the above rotation of the earth-axis against the fixed Sun.

From the above is achieved a formula that if on the polar-axis-bar the director-bar is rotated such that it forms a cone of 23.5 degree, then it can cover all the positions of the sun during the year.

However there is again a problem. The Sun moves from north to south from 22nd June to 22nd December and from south to north from 22nd December to 22nd June, thus taking equal time, but it takes different time for moving from central position to 23.5 degree north and coming back to central position and then moving to south and coming back to central position; it takes roughly 186 days for the first and only 179 days for the second movement. This fact has also been taken into account while devising the declination setter.

The above formulae of 23.5 degree cone has been translated into mechanism as follows:—

(Please See FIG. 2 if Necessary.)

The purpose of declination-setter is to move the director-bar according to the change in the declination of the Sun; this can be done by moving director-bar on the polar-axis-bar to form a cone of 23.5 degree with its vertex on the axis of the polar-axis-bar as seen above. But the inventor has devised another device, the time-setter by providing for the polar-axis-bar a zero position as the staring point permanently, therefore the east-west movement of the director-bar in its conic movement would disturb the arrangement. Thus the requirement of the other device namely time-setter is such that the movement of the director-bar takes place in just two dimensional plane. Therefore more components have been added so that only north-south-north changes are obtained and the east-west changes of the director-bar caused by its conic movement are eliminated. This is achieved as follows. The polar-axis-bar is cut into two equal pieces and then a frame is fitted between the two pieces at a perpendicular. A bar, fitted in the frame, is placed along the perpendicular on the axis of the polar-axis-bar such that the axis of this another bar forms a right angle on the axis of the polar-axis-bar. Let us name this another bar as declination-bar. The declination-bar has free movement along its axis. There is a hole at the center of the declination-bar. A U-shaped clamp is fitted on a nail passing through the hole on this declination-bar. A thin bar is fitted on the clamp. Now if the thin bar is rotated in a circle, because of the combined effect of the nail and the clamp the declination-bar will also rotate. If the thin bar is rotated such that it forms a cone of 23.5 degree with its vertex on the axis of the declination-bar, the declination-bar will experience all the angles which a the director-bar needs in the north-south-north direction during the year. For achieving this the following arrangement is had.

On the frame on which declination-bar is fitted, there is another strip, let us call it second strip, parallel to the declination-bar. At the center of this second strip there is a pivot for a circular strip. This circular strip is an arc cut out of an imaginary circle which has its center on the axis of declination-bar, the thin bar is fastened on a hole on the circular-strip at a distance equal to 23.5 degree from its pivot. This circular-strip is rotated one full circle in one year. In its regular movement it causes all angles in the declination-bar for the year.

However, one has to provide for the eccentricity of the earth-orbit around the Sun which is experienced in the peculiarity that the central position for the sun on the polar axis comes once in 179 days and then in 186 days approximately. This is provided for as follows.

The circular-strip is fitted on an axle passing through the second-strip. On the other end of the axle is fitted another strip. This strip has a hole on which a nail coming from the parallelly moving gear disc is fastened.

There is a third strip on the frame, which is also parallel to the declination-bar. On this third strip a disc having teeth on its circumference is fitted parallel to the declination-bar. Though the gear is placed parallel to the declination-bar its pivot is eccentric in relation to pivot of circular-strip. A nail is fitted on this disc which is fastened on the strip fitted on the other side of the circular-strip. The distance of the nail from the pivot of the disc is scaled according to the difference—the quantum of eccentricity—between the pivots of the circular-strip and the disc and it has to be such that when the disc moves, the movement of the director-bar from central position to the south and back is completed by 177.2 degree movement of the disc and the northern movement of the director-bar is completed in 182.8 degree movement of the disc.

The disc completes one round in one year i.e. 365.25 days when moved by the timer. For convenience for installation or on resumption of operation after repair caused by breakdown etc., a circular lamina having marking of dates on its circumference may be fitted on the disc and may be named as calendar-disc. (This calendar may be used with caution keeping in mind the effect of leap-year.)

This declination setter is one complete invention in itself, yet it forms unity of invention of the present machine because it helps in automation of the polar-axis tracking system.


The device of time-setter is based on the actual experience of the difference in the timing of noon.

The device has two versions.

The first is based on the principle that there should be a fixed zero position for starting of the operation of the machine and it should reach the noon—the meridian position of the Sun—when the Sun is expected to be there as per real experience for the particular day and for the particular place where it is operating. The zero point will be resting point for the machine till it begins operating in the morning. On the basis of actual experience a the data is created for each place of operation and then a microprocessor is designed and programmed for starting of the machine at the time stipulated for each day of the year. This is a simple mechanism.

In the second version, the time bf starting the machine is fixed and no data or microprocessor is required; therefore this is preferable for reducing cost and easier maintenance of the machine. In this version the starting point is manipulated everyday.

For example if the machine is fixed for starting at 6 a.m. then for a standard day i.e. when the Sun actually reaches meridian point at 12.00 p.m. the polar-axis-bar will move 90 degree because it is moving at a speed of one round per 24 hours. So the basic point for starting will be 90 degree before the meridian point. A time-bar parallel to the director-bar is fitted on the polar-axis-bar and the basic point is decided as described above. Then with the help of time-disc described in the description of FIG. 6 which has varying radius for each day the time-bar is brought to the suitable starting point as per actual experience. This time-disc is not place specific because the apparent slow and fast movement of the Sun is same globally.

Combining of the Two Parts Viz. Redirection System and Sun-Tracking System:

As mentioned earlier the sun-tracking part is designed to realize the technique of the redirection system. In actual designing of the machine one has to just place the director-bar—described in Sun-tracking Part—in the sun-arm position of the system described above in Redirection System.

As shown in FIG. 1 in the actual design of the machine, however, while the same principle is used, the target-arm is truncated and only tiny axle (5-A) as shown in FIG. 1 is retained. Also the sun-arm, though occupying the position as per original plan, is fitted on the polar-axis-bar and gets movement due to the movement of the polar-axis-bar.

By combining these two parts a complete machine has been created which has been described in the description of FIG. 1.

Functions of the Components and their Assembling for Operation:—

(Please See FIG. 1.)

The whole device is supported by stand (1). The stand (1) has to be adjusted such that the shaft (7-A) supporting arc (7) is in vertical position.

Arc (7) is then placed on the supporting shaft (7-A) such that the polar-axis-bar (9) comes in the position parallel to the axis of the earth. Circular shape of Arc (7) ensures that in any position of the rotating bar (9) the pivot point of director bar is at the same distance from mirror-pivot.

The mirror is fitted on the mirror-arm (12) such that its surface is precisely parallel to the axle (4). Free movement of axle (4) and (5-A) must be checked before slide (11) is fitted into mirror-arm (12) and the machine is put to operation.

With the help of declination-setter (8) the director-bar (10) is set at the position for the date of operation. In this position the director bar has the same angle with the polar-axis-bar (9) as the sun has with the earth-axis on that day of the year.

The time-setter is also adjusted for the date of operation so that the machine starts at the desired time next day. Timer of the Time-setter is also put on. Before starting timer (13) the director-bar which has extension on the other side of the mirror arm (12) bar disc (14) is fitted and the rotating bar is rotated on either side until there is no shadow of the bar on the disc. This ensures sun-orientation of the director-bar (10).

Then Arc-couple (3) and (6) are so adjusted that the sun-light is reflected on the desired target area. The sun orientation of the director bar (10) must be checked again and arc couples and director bar adjusted if necessary.

Now the timer (13), timer of the declination setter and the timer of the time-setter must be put on.

Working of the Machine:—

When timer (13) is energized by the spring work/electricity starts moving the polar-axis-bar (9), the director bar (10) also starts moving. This movement of the director bar (10) ensures that it is constantly sun oriented. By the movement of director bar, the slide (11) fitted on the director bar (10) starts moving the mirror arm. The mirror-arm has movement in two directions and as explained earlier, it continues to occupy the position of the third side of the triangle which ensures reflection of sun light parallel to the direction of target arm. As long as the timer (13) keeps moving the rotating bar at the speed of one round every 24 hours, sun-light is reflected continuously on the target area until the sun sets in the west.