FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
AN INTELLIGENT SOLAR TRACKING SYSTEM AND METHOD THEREOF
THERMAX LIMITED
an Indian Company,
of Thermax House, 4, Mumbai-Pune Road,
Shivajinagar, Pune - 411 003,
Maharashtra, India.
Inventors:
THAKUR DEEPAK JANGADA JAYPRAKASH AHMAD TANVEER
The following specification particularly describes the invention and the manner in which it is to be perforined.

FIELD OF DISCLOSURE
The present disclosure relates to solar thermal plants and solar concentrators thereof.
BACKGROUND
There are many methods for producing heat and power from solar energy. The most common and viable method includes a system that employs reflective surfaces, typically referred to as solar concentrators, to concentrate the incident sunlight onto a receiver, thereby translating solar energy into electrical or thermal energy.
Rotation of earth about the polar axis, results in a diurnal cycle of night and day and causes the apparent motion of the sun across an imaginary celestial sphere. In order to obtain a focus of the reflected beam of the incident sunlight onto the receiver at the ground level, the standing concentrators in the northern hemisphere are made to face towards the south and vice versa. Further, in order to adjust the concentrators with respect to migration of the sun, the concentrators are provided with two actuators for adjusting the inclination of the concentrator by half of the change of the solar declination angle and to attain the required shape of the parabola for any day of the year. This correction or sun apparent movement is also called North-South (N-S) movement of the sun. Each concentrator needs to be individually adjusted such that it is precisely aligned to reflect the optimum concentration of solar radiation to the receiver. Generally, the receiver is located at the focal point of the concentrator.
Fixed focus concentrators have been widely used for medium temperature application in different parts of the world. These concentrators generally are the

lateral sections of the parabolic dishes or paraboloids and therefore provide a fixed focus that is away from the path of incident beam of radiations, throughout the year. While installing a fixed focus concentrator at any site, the axis of rotation is fixed very precisely at an angle equal to "the latitude of the site" with horizontal in north-south direction. Further, for daily tracking, these concentrators rotate along an axis parallel to the polar axis with an angular velocity of one revolution per day to counterbalance the effect of daily rotation of the earth.
Typically, in a solar thermal power plant, numerous solar concentrators are employed to reflect sunlight onto the receivers. The concentrators need to be continuously repositioned according to the relative apparent motion of the sun with respect to the earth. This periodic exercise of repositioning of the concentrators may result in associated dish orientation errors further leading to optical losses.
Certain solar concentrator tracking systems comprise semi open loop automated East-West (E-W) tracking system through a Programmable Logic Circuit (PLC) and a manual actuator for seasonal adjustment. However at certain times, the focus of the reflected beam goes out of the receiver aperture; whereby the manual adjustment of the actuators, after every one or two days, is necessary.
During cloudy conditions, tracking of the sun and its motion becomes difficult As a result, adjusting the concentrators poses a tricky challenge. Furthermore, the presence of multiple concentrators makes the tracking process technically demanding.

A need is thus felt to develop an intelligent tracking system that overcomes the aforementioned shortcomings and provides a more effective, economical and self-sufficient system that can continuously track the solar concentrators with respect to the sun, under any environmental conditions and absorb maximum solar energy.
OBJECTS
Some of the objects of the system of the present disclosure are aimed to ameliorate one or more problems of the prior art or to at least provide a useful alternative and are listed herein below.
An object of the system of the present disclosure is to absorb maximum solar energy.
Another object of the system of the present disclosure is to enable maximum sunlight to be incident on the solar concentrators.
Another object of the system of the present disclosure is to continuously track the solar concentrators with respect to the solar movements.
Another object of the system of the present disclosure is to continuously track the solar concentrators with respect to the solar movements, under any environmental conditions.
Another object of the system of the present disclosure is to achieve the tracking of the solar concentrators through solar image processing.
Another object of the present disclosure to provide an intelligent system, for tracking of the solar movements, that is self-sufficient and economical.

Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.
SUMMARY
In accordance with the present disclosure,
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The system of the present disclosure will now be described with the help of the accompanying drawings, in which:
Figure 1A illustrates a schematic representation of a solar tracking system in accordance with an embodiment of the present disclosure;
Figure IB illustrates the movements of a solar concentrator in accordance with an embodiment of the system of Figure 1A;
Figure 1C illustrates a schematic representation of a solar image as captured by an image capturing device in accordance with an embodiment of the system of Figure 1A; and
Figure 2 a schematic representation of a solar tracking system in accordance with another embodiment of the present disclosure;
DETAILED DESCRIPTION
The system of the present disclosure will now be described with reference to the embodiments shown in the accompanying drawings. The embodiments do not

limit the scope and ambit of the disclosure. The description relates purely to the example and preferred embodiments of the disclosed system and its suggested applications.
The system herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known parameters and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the example should not be construed as limiting the scope of the embodiments herein.
In accordance with the present disclosure, solar sensors, thermal imaging device/s and/or thermocouple sensors are mounted on parabolic concentrators and/or solar receivers, and based on the signals from the solar sensors and thermal image capturing device/s, a control device controls a set of actuators and driving means to control the movement of the parabolic concentrators thereby forming a closed-loop automated tracking system.
Referring to Figure 1A, a schematic representation of a solar tracking system 10 in accordance with an embodiment of the present disclosure is illustrated. The system 10 comprises a flexible arcuate solar concentrator 100, an image capturing device 120 operatively coupled to the solar concentrator 100, an upper actuator 130 and a lower actuator 140 both operatively coupled to the solar concentrator 100, a driving means 150 operatively coupled to the solar concentrator 100, a solar sensor 160 co-operating with the solar concentrator 100 and a control device 200 (shown in Fig 2). The solar concentrator 100, the image capturing device 120, the upper actuator 130 and the lower actuator 140,

and the driving means 150, are all mounted on a supporting structure. The solar sensor 160 is mounted rigidly with its axis parallel to the parabolic axis of the concentrator 100. A receiver 110 is located at a predetermined distance from the supporting structure and is mounted on a stand. Solar radiations 170 are reflected by the reflecting surface of the solar concentrator 100 as reflected rays 180 towards the receiver 110. The optical axis of the image capturing device 120 is aligned with the normal of the receiver aperture in order to get a clear image of the receiver 110 and a focus (not shown in figure) of the reflected beam 180. The control device 200 is adapted to receive input signals from the receiver 110, the image capturing device 120 and the solar sensor 160 and generate feedback signals for the driving means 150 and the actuators 130,140. Additionally, a plurality of thermocouple sensors 190 are mounted on the surface of the receiver 110. In accordance with another embodiment, thermocouple sensors 190 can be employed to determine the location of the focus on the receiver 110. Based on the intensity of the focus, the thermocouple sensors 190 generate signals which are used for calculating the position of the focus on the receiver 110.
Referring to Figure IB, the movements of a solar concentrator 100 in accordance with an embodiment of the system 10 of Figure 1A is illustrated. The dish rotation direction 150b for daily tracking and the direction of movements 130b,140b of upper and lower actuators, based on the seasonal lateral movement of the sun's position with respect to the earth, is illustrated.
Referring to Figure 1C, a schematic representation of a solar image as captured by an image capturing device in accordance with an embodiment of the system 10 of Figure 1 A, is illustrated. In an ideal situation, the receiver and the focus of the reflected beam are superimposed on one another. The figure also shows the location of the thermocouple sensors 190 mounted on the receiver 110.

Referring to Figure 2, a schematic representation of a solar tracking system 20 in accordance with another embodiment of the present disclosure is illustrated. The system 20 comprises a plurality of flexible arcuate solar concentrators 200 interfaced with a single control device 280 and operatively coupled to a single driving means 250 for East-West (E-W) or daily tracking, so that the cost of the overall tracking system 20 can be minimized. Further, each solar concentrator 200 is operatively coupled to an upper actuator 230 and a lower actuator 240. All the solar concentrators 200 are connected through a connecting member 270. In accordance with one embodiment, the connecting member 270 is made up of aluminum. A receiver 210 is located at a predetermined distance from the solar concentrators 200. An image capturing device 220 is operatively coupled to each concentrator 200, to capture the image of a focus of the reflected beam from the solar concentrator 200 and the receiver 210 aperture. In accordance with one embodiment, the image capturing device 220 is a thermal image capturing device. The actuators 230,240 adjust the concentrators 200 according to the seasonal lateral movement of the sun with respect to the earth. The control device 280 is adapted to receive images of the focus from each of the image capturing device 220, to determine the centroid of the focus and compare it with the predetermined center of the receiver. Any offset present in the vertical axis is calculated and accordingly a signal is generated by the control device 280 to move the respective actuators 230,240 and driving means 250 to accurately align the image of the focus of the reflected beam and the receiver aperture for optimum results. Images taken from each image capturing device are generally converted into grey scale to get different pixel value according to brightness at different points on the receiver 210. Typically, a pixel contains 256 values and varies from 0 to 255; the brightest pixel will have a value of 255. In order to avoid any background noise, different methods can be used to filter the image of the focus of the reflected beam. In accordance with one embodiment, the smaller focus area is neglected and only the bigger focus area

is used for processing and for determining the centroid of the focus of the reflected beam. Additionally, the background noise causing low brightness of the image is avoided by using a threshold pixel value, which in accordance with one embodiment is 225, whereby all pixel values less than 225 will be neglected. Any offset in the vertical axis direction is adjusted and corrected by the lower actuator 240 and upper actuator 230. Referring to Figure 1C, when the centroid of the focus area of the reflected beam is located in the first/second quadrant, the control device 280 is generates a signal, whereby the upper actuator 230 pushes and lower actuator 240 pulls the dish in order to adjust and overcome the offset in vertical axis direction. Similarly, an opposite signal will be generated by the control device 280 when the centroid is in the third/fourth quadrant. Similar approach is followed to nullify any offset in the horizontal axis direction with the help of the driving means 250. Since all the solar concentrators 200 are connected with the connecting member 270 and powered with a common driving means 250, an output signal for daily tracking is generated by calculating an average signal from all the solar sensors 260 of all the concentrators 200. The system 20 embodies the use of one solar sensor 260 for daily tracking, if optics of the concentrators 200 and the installation of the concentrators 200 are accurate. This process will be continued to give the most optimized position of all the connected concentrators 200.
In accordance with one embodiment, a method for tracking the solar
concentrators comprises the following steps:
(i) starting operation of the control device 280 at a set time automatically;
(ii) moving the concentrators 200 towards a position, typically the position of the sun in the evening, by the driving means 250 to capture images of a focus of the sunlight reflected by the solar concentrators 200 on the receiver 210;
(iii) stopping the solar concentrators 200 when the focus is detected by the thermal image capturing device 220 and/or the thermocouple sensors;

(iv) moving the concentrators 200 through the driving means 250 according to
the signal of the solar sensors 260 for daily tracking till sunset. (v) processing the images to determine the centroid of the focus area by the thermal image device 220 or to determine the position of the focus area on the receiver 210 through the thermocouple sensors; (vi) comparing the centroid of the focus area with the center of the receiver 210
to calculate the offset in the vertical-axis; (vii) moving the actuators 230,240 to overcome the offset, if any offset is
present in the vertical-axis; (viii) modifying the radius of curvature of the concentrators 200 to form a
circle like image on the receiver 210. (ix) if no focus area is detected by the thermal imaging device 220 and/or the thermocouple sensors, then moving the concentrators 200 via the driving means 250 according to a timer logic wherein, in accordance with one embodiment of the timer logic, the concentrators 200 are rotated by an angle of fifteen degrees (15°) per hour and resuming the tracking as soon as the focus area is detected by the thermal imaging device 220 and/or the thermocouple sensors; (x) repeating steps (iv) to (ix) till sunset;
(xi) moving the concentrators 200 towards a home position, typically a morning position, after the sunset and waiting for the next day starting time;
In accordance with the aforementioned method, the shape of the solar concentrators 200 is changed, whereby the concentrators 200 can have different parabolic equations for each day. Both the upper and lower actuators 230,240 are used for changing the shape of the concentrators 200, thereby making the focus circular in shape and bringing the focus, at the center of the receiver 210.

Thus, the tracking system of the present disclosure is not only intelligent and self-sufficient, but also economical and affordable.
Although the above described system and the method is a preferred embodiment, other configurations of the system are included in the scope of the present disclosure.
TECHNICAL ADVANCEMENTS AND ECONOMIC SIGNIFICANCE
The technical advancements offered by the system and method of the present disclosure include the realization of:
• absorbing maximum solar energy;
• continuously tracking the solar concentrators with respect to the solar movements;
• enabling maximum sunlight to be incident on solar concentrators;
• continuously tracking the solar concentrators with respect to the solar movements under any environmental conditions;
• tracking of solar concentrators through solar image processing; and
• an intelligent self-sufficient and economical system for tracking of the solar movements.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results.
Any discussion of materials, devices, or the like that has been included in this specification is solely for the purpose of providing a context for the invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the invention as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the invention, unless there is a statement in the specification specific to the contrary.
The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

We Claim:
1) A tracking system for a solar thermal plant, said plant comprising a plurality
of flexible arcuate solar concentrators, at least one receiver adapted to
receive concentrated sunlight reflected by the solar concentrators, at least
one driving means operatively coupled to the solar concentrators to angularly
displace each of the solar concentrators, a plurality of actuators operatively
coupled to each of the solar concentrators to modify radius of curvature of
each of the solar concentrators, at least one solar sensor co-operating with
each of the solar concentrators, and at least one image capturing device
operatively coupled to each of the solar concentrators, the image capturing
device adapted to focus sunlight on the receiver,
said system characterized in that:
• a control device is provided which is adapted to receive input signals from the receiver, the image capturing device and the solar sensors and generate feedback signals for the driving means and the actuators, said control device comprising a selector adapted to switch between a dynamic logic and a set logic based on said signals received from the receiver, the image capturing device and the solar sensors in real time,
■ said dynamic logic adapted to control the driving means and the actuators to facilitate a circle like image to be focused on the receiver; and
■ said set logic adapted to control the driving means to displace each of the solar concentrators by a set driving speed when the focus is not adequately captured by the image capturing device.
2) The system as claimed in claim 1, wherein the optical axis of the image
capturing device is aligned with the normal of the receiver.

3) The system as claimed in claim 1, wherein the image capturing device is at least one of a thermal image capturing device and a plurality of thermocouple sensors.
4) The system as claimed in claim 1, wherein the axis of the solar sensor is parallel to the parabolic axis of the solar concentrator.
5) The system as claimed in claim 1, wherein said control device comprises at least one processor.
6) The system as claimed in claim 1, wherein said set driving speed corresponds to angular displacement of fifteen degrees per hour.
7) A method for tracking sunlight incident on a plurality of flexible arcuate solar concentrators of a solar thermal plant, said method comprising the following steps:
a. initiating tracking at a pre-determined time;
b. angularly displacing at least one of the solar concentrators towards a pre
determined position;
c. capturing an image of a focus of concentrated sunlight reflected by the
solar concentrator on a receiver;
d. switching between a dynamic logic and a set logic in real time, wherein
• execution of said dynamic logic comprises:
■ processing said image to determine the centroid of said focus;
■ comparing said centroid with the pre-determined center of said receiver to calculate the offset in the vertical axis;
■ angularly displacing the solar concentrator to nullify the offset in the vertical axis; and

■ modifying the radius of curvature of the solar concentrator to facilitate a circle like image to be formed on the receiver; and • execution of said set logic comprises displacing each of the solar concentrators by a set driving speed when the focus is not adequately captured by the image capturing device;
e. repeating steps from c and d for a pre-determined duration; and
f. angularly displacing the solar concentrator towards a home position upon
expiry of said pre-determined duration.
8) The method as claimed in claim 6, wherein said pre-determined position corresponds to position of the sun in the evening.
9) The method as claimed in claim 6, wherein said pre-determined duration corresponds to time from sunrise till sunset.
10) The method as claimed in claim 6, wherein said home position corresponds
to position of the sun in the morning.