Claims:We claim:
1) A hydraulic based sun-tracking system comprising:
a plurality of plungers enclosing small cylinders of same size wherein the small cylinders are connected in parallel to each other;
a hydraulic system connected to the plungers for alternately filling fluid in the plungers; and
a plurality of large hydraulic cylinders fluidically connected to the small cylinders and each large cylinder enclosing a sliding cylindrical RAM; wherein a solar panel having plurality of sensors are mounted on the sliding cylindrical RAM.

2) The hydraulic based sun-tracking system as claimed in claim 1 wherein acapacity fluid tank is placed over each plunger to generate an alternate and equal amount of force on the small cylinders.

3) The hydraulic based sun-tracking system as claimed in claim 1 wherein the sensors control the movement of the solar panel in north-south and east-west directions.

4) The hydraulic based sun-tracking system as claimed in claim 1 wherein the fluid could be water or oil or any other liquid that is non evaporative in nature.

5) The hydraulic based sun-tracking system as claimed in claim 1 wherein the sensors are connected to a control circuit for operating relays.
6) A method of operating hydraulic based sun-tracking system as claimed in any of the preceding claims, comprising:
generating force on plungers by filling a fluid tank;
exerting the generated force on the sliding cylindrical RAMs of two large hydraulic cylinders; wherein the force is alternately exerted on each of the two large hydraulic cylinders causing the movement of the solar panels.

, Description:Field of the Invention
Present invention relates to a sun-tracking system and more particularly relates to capturing the maximum sun radiation and increase the photovoltaic (PV) panel output using a dual axis sun tracker. Dual axis sun tracking system keeps the PV panel facing towards the sun in both east-west and north-south direction.
Background of the Invention
Figure 1 shows a sun tracking system of prior art, wherein it is observed that in summer, the sun is at zenith (on head) and gradually shifted towards the south up to 23.5 degrees in winter season. This variation in sun path decreases the incident sun radiation and as a result the PV panel output also decreases. To capture the maximum sun radiation or increases the PV panel output, a dual axis sun tracker is required. Dual axis sun tracking system keeps the PV panel facing towards the sun in both east-west and north-south direction.
According to present invention, sun tracking is evolving on the basis of the design of a hydraulic press. The system of present invention is very economical and efficient. Dual axis sun tracking system which tracks at sun continuously throughout a day. Present invention helps to acquire maximum solar incident radiation in order to convert it into a useful form. Incident radiation of the sun can convert into electricity by using PV panel and heat energy by using solar concentrator. If the same design of hydraulic press introduces directly to achieve sun tracking operation, there are several disadvantages/limitations associated therewith. These limitations are:-
A certain movement of sliding RAM is required to track the sun from east to west direction and north to south direction. It is acceptable; a desired force can be generated by applying a small force, only changing the ratio of area of sliding RAM and plunger. An important fact associate with a design, an amount of force generated is inversely proportional to the displacement of sliding RAM. Therefore the machine is either able to lift a large amount of PV panel for a small distance in the desired direction or ability to lift a less amount of PV panel for a large distance in desired direction. A constant force F1 is applied on both the plunger. In figure 2 (a), the sliding RAM brings a large amount of weight W for a height h with a one complete movement of the plunger. In figure 2b, the sliding RAM brings a less amount of weight (W’) for a height (h’) with a one complete movement of the plunger. It is because the net movement of sliding RAM depends on the amount of oil displaced by the plunger. Due to a difference in size of two cylinders, both the sliding RAM gives an asymmetric response in terms of height and weight.
Example 1: For a system as shown in figure 2a, a set of gearbox is connected to a sliding RAM to increase the resultant movement of connecting rod to achieve a desired movement of PV panel. In a gear box (shown in figure 3), a rack 1 is connected to a sliding RAM and a rack 2 is connected to a connecting rod. This may helpful to get the desired PV panel movement with an extra force applying on a plunger. This extra force is required to compensate a decrease in load carrying capacity of a system.
Another arrangement is made to achieve a desired height and weight of sliding RAM. Movement of sliding RAM depends on the displacement of oil by plunger. If the ratio of volume of both the cylinders is 1, the system gives a desired movement of PV panel. For a same input force, the height of the small diameter cylinder must be increased to maintain the equal volume (as shown in figure 2c). Thus, at the same input force a desired weight, carried by a RAM up to the required height. This system has lots of limitations which are discussed later.
For a system as shown in figure 2b, this system is able to give a desired movement of PV panel but inefficient to hold a large weight. To increase the load carrying capacity of a system, an extra force is required.
In both the examples, it is observed that to achieve a desired sun tracking operation, an extra force is required. Extra force means an extra weight applies on a plunger.
sun tracking based on the concept of hydraulic press and hydraulic lift:
One of the simplest forms of sun tracking system is designed on the basis of hydraulic press (as shown in figure 4). This is the existing patent technology, but has some limitations as itinvolves the movement of PV panel from east to west direction to track the sun by the help of hydraulic system. In this hydraulic system, a small water tank has fitted with a plunger. This water tank has filled by the pump placed in a water storage tank. When the small water tank is completely filled with water, it exerts a downward force on the plunger and moves the plunger in a downward direction. The force offered by the plunger will be multiplied at the sliding RAM. A large force moves the sliding RAM in upward direction and hence the PV panel connected to the sliding RAM through a connecting rod start to move in the direction of East to West. The downward movement of plunger due to a force offered by water is controlled either by a solenoid valve or by limiting the amount of water in a water tank. Solenoid valve controlling is preferred because to lift a fixed amount of weight a fixed amount of force is required. In the evening when the plunger reaches its final position and switch operates. In order to bring the sun tracker to its initial position a solenoid valve opens and the water store in a water tank drag in a storage water tank. And the plunger and sliding RAM regain its initial position. Again in the early morning to start a sun tracking, a pump starts for a fixed time period to pour water into a water tank.
What is required is a hydraulic sun tracking system with following features:
1. Dual axis sun tracking system which helps to increase the conversion efficiency of PV panel
2. Low maintenance required and low cost
3. High accuracy of sun tracker
4. Less energy consumption during operation
5. Acquire less land space for installation
6. Fit for any kind of solar application, e.g., solar water heating, solar stiller etc.
Limitation of this system:
1. It is required to keep the volume of both cylinders are same to obtain a desired movement.
2. A large difference in the ratio of the diameter of sliding RAM and plunger cannot be maintained. Because long height of plunger is undesirable this increases the efforts of pump (figure 2c) at the cost of increased energy consumption.
3. The design offers a small Force multiplication factor.
Therefore there arises a need to develop a hydraulic based sun-tracking system. The system includes a plurality of plungers enclosing small cylinders of same size wherein the small cylinders are connected in parallel to each other. A hydraulic system is connected to the plungers for alternately filling the fluid in the plungers anda plurality of large hydraulic cylinders fluidically are connected to the small cylinders and each large cylinder encloses a sliding cylindrical RAM. A solar panel having plurality of sensors are mounted on the sliding cylindrical RAM.
In another aspect the invention provides a method of operating hydraulic based sun-tracking system. The method includes steps of generating force on plungers by filling the fluid tank;exerting the generated force on the sliding cylindrical RAMs of two large hydraulic cylinders; wherein the force is alternately exerted on each of the two large hydraulic cylinders causing the movement of the solar panels.

Brief Description of Drawings of the Invention:
Fig.1 shows position of the sun in summer, the sun is at zenith (on head) and gradually shifted towards the south up to 23.5 degrees in winter season.
Fig.2 shows two cylinders having a different diameter connected to each other in conventional hydraulic press/lift.
Fig.2a shows a set of gearbox that is connected to a sliding RAM to increase the resultant movement of connecting rod to achieve a desired movement of PV panel.
Fig.2b shows a system that is able to give a desired movement of PV panel but inefficient to hold a large weight.
Fig.2c shows the increasing height of the small diameter cylinder to maintain the equal volume for same input force.
Fig.3 shows a gear box that is used to achieve the desired PV panel movement.
Fig.4 shows single axis hydraulic sun tracker.
Fig.5 shows three dimensional view of hydraulic sun tracker.
Fig.6 shows two dimensional view of hydraulic sun tracker.
Fig.7a shows morning position of hydraulic sun tracker.
Fig. 7 b shows afternoon position of hydraulic sun tracker.
Fig. 7 c shows evening position of hydraulic sun tracker.
Fig. 8a shows initial position of hydraulic sun tracker.
Fig. 8b shows intermediate position of hydraulic sun tracker.
Fig. 8c shows noon position of hydraulic sun tracker.
Fig. 8d shows intermediate position of hydraulic sun tracker.
Fig. 8e shows final position of hydraulic sun tracker.
Fig. 9a shows sensor connection in relay circuits.
Fig. 9b shows turn ON position one of sensors.
Fig. 9c shows turn ON position two of sensors.
Fig. 9d shows turn OFF position of sensors.
Fig. 10a shows position of sensors in a fixed sensor unit.
Fig. 10b shows position of sensors in a movable sensor unit.

Detail Description
Hydraulic type solar tracking system performs the sun tracking operation effectively using an innovative hydraulic press. According to present invention, a conventional hydraulic press/lift is modified technically into a very efficient machine which operates at less operating force. A hydraulic press is a machine which is designed on the basis of Pascal’s law (Law of transmission of fluid pressure). On this machine, an applied small force is converted into a large force.
Two cylinders having a different diameter connected to each other (as shown in figure 2). A sliding RAM moves in a large diameter cylinder and plunger operated in a small diameter cylinder. Let ‘A’ be the area of sliding RAM and ‘a’ be the area of the plunger. Area of sliding RAM is greater than the area of the plunger, i.e., A>a. If F is the force applied to the plunger then corresponding pressure intensely developed is P= (F/a). According to Pascal’s law; in an enclosed chamber and for an incompressible fluid, a pressure is constant at every point inside the chamber. Then at constant pressure, force on a RAM increases with decrease in area of cylinder.
F=P.a or P1=F1/a……………………. (1)
Similarly,
F=P.A or P2=F2/A……………………… (2)
And P1=P2=P, according to Pascal’s law
Equate equation 1 & 2
F1/a=F2/A then,
F2=F1. (A/a)……………………………. (3)
Accordingly, if W is the total weight lifted by the RAM, then F2=W= P.A and hence W=F. (A/a). From equation 3, it is seen that by applying a small force F1 on the plunger a large force F2=W may be developed at the RAM. By suitably adjusting the area of the plunger and the RAM even a small force may be multiplied many times.
The system of the present invention works on a concept of hydraulic press/lift, a large weight, carried by a large hydraulic cylinder by applying a small weight on the small hydraulic cylinder (as shown in figure 2). A piston area of a large hydraulic cylinder is two times the piston area of the small hydraulic cylinder. Therefore, according to Bernoulli’s theorem, a force exerted at piston of large hydraulic cylinder is twice the force applied by the piston of the small hydraulic cylinder. A main cylinder piston is operated by sequential operation of two mini cylinders. Amount of PV panel carried out by a main hydraulic cylinder depends on the amount of force generated at the piston (sliding RAM) of the main cylinder. Under this arrangement, an amount of force generated by a piston (plunger) of small cylinder which is delivered to a main hydraulic cylinder. A ratio of force is generated depends on the ratio of an area of the main cylinder piston (sliding RAM) and small cylinder piston (plunger). Thus the resultant force is generated at main cylinder sliding RAM depends on the amount of weight applied to the plunger of the small hydraulic cylinder.
As shown in Figure 6, hydraulic based sun tracking system is an innovative kind of dual-axis sun tracking system. Sun tracking mechanism involves the movement of sliding RAM (22) and(28) of two large hydraulic cylinders (21) and (27) which are alternately operated by a plunger of two small hydraulic cylinders (7) and (7’) of the same size. The alternate operation of these two small cylinders will be controlled by the solenoid valves (9), (9’), (10) and (10’). The alternate dragging and pumping of fluid between both the fluid tanks through the DC fluid pump generate a force alternately on both the plungers. Turning ON and OFF of DC fluid pump depends on the operation of the switch (33) and (33’) and control circuit (41). Two separate, alternate and equal amount of force generated on a plunger as a result of placing an equal size and capacity of the fluid tank (5) and (5’) over a plunger (7) and (7’) which are used for storingthe fluid (40). If water is taken as fluid, quantity of water may reduce in summer season due to evaporation and requires checking periodically the availability of desired quantity of water in a tank. To overcome this problem, a fluid/oil having a property similar to the water and non-evaporative by its nature can be used. The amount of force generated by these two alternately operated plungers (8) and (8’) gets multiplied and exerts on sliding RAMs of two large hydraulic cylinders. Sliding RAMs are connected to a PV panel frame (39) on which the PV panel (34) installed through connecting rod (29) and (30). The linear displacement of sliding RAM will be appearing as an angular displacement of PV panel assembly. Amount of angular displacement of PV panel in a desired axis (east-west and north-south) will be control of the solenoid valves (15) and (16) and light sensors (42) and (42’).
The working of a hydraulic based sun tracking system understands by the help of a simplified 2D diagram of modified hydraulic press (as shown in figure 6). Two small cylinders (7) and (7’) having a same size connected parallel to each other to a hydraulic system. Both the hydraulic system having two ports, one is an input port (37) and (37’) and another is output port (38) and (38’). A solenoid valves (10) and (10’) are connected to input ports and solenoid valves (9) and (9’) are connected to output ports of both the small cylinders. Two large hydraulic cylinders (21) and (27) are also connected to the same channel. It also has two input ports (35) and (35’) and two solenoid valves (15) and (16) connected to the ports. Similarly, two another solenoid valves (20) and (24) connected to the output port (36) and (36’) of main cylinders. A sliding RAM (28) is attached with a cylinder (27) having height 1/4th to the sliding RAM (22) attached with a cylinder (21). The size of a large cylinder and its diameter to height ratio depends on the amount of lift force required. It depends on the location at which they are connected to the PV panel assembly frame and the amount of weight requires carrying (as shown in figure 5).
Connection of various sensors used in control circuit with the solenoid valves shown in figure 9 a. The entire sensors used in a control unit working as a light activated switch. When a sun light strike on the light sensor, a control circuit operates the relays. LDR (Light Dependent Resistor) is used as a light sensor. Control unit involves two sensing units (220) and (270) and each unit having a two light sensor (as shown in the figure, 10 a and b). Sensor unit (220) is fixed on a stand (2) includes a light sensor (200) and (210) (as shown in the figure, 5).
Light sensor (200) is used to activate the entire sensing system to control sun tracking operation during light hours and in the absence of sun light it turns OFF the remaining sensors in order to save the energy (as shown in figure. 10a and b). It also closes the solenoid valve (20) which remains ON to transfer all the fluid (32) from cylinder (21) to oil tank (1).
Light sensor (210) is used to control the downward movement of sliding RAM (28) by opening the solenoid valve (24)and controls the movement of PV panel in the north-south direction up to 23.5° south position. A metal sheet partition (230) is used to provide a sun shade for sensor (210) during afternoon hours. The sensor (210) is in a fixed position and available in the sun light till noon (as shown in figure 10a). During that duration the relay circuit (310) is in operation and the relay circuit (320) remains deactivated (as shown in figure 9b). From afternoon to evening, sensor (210) goes into the dark a relay circuit (320) comes into operation and (310) remains deactivated. Both the relay circuits (310) and (320) operate by the common control signal generated by the light sensor (250) but the sequential input supply has provided by the relay circuit (300) controls by a light sensor (210) (as shown in figure 9c).
Another sensing unit (270) is placed on the PV panel (34) and move along with the PV panel (as shown in figure 10b). It also includes two sensors (240) and (250) which are used to detect the position of sun in east-west and north-south direction. In figure 9b, Light sensor (240) is used to control the upward movement of sliding RAM (22) by the opening of the inlet solenoid valve (15). This sensor helps the PV panel to track the sun in the east - west direction. A metal sheet partition (260) placed parallel to the light sensor (240) provides sun shade from the east direction (as shown in figure 10b). It means that whenever the sun becomes perpendicular to the sensor, light allow to fall on the sensor (240) and it opens the solenoid valve (15).
Light sensor (250) provides a north-south tracking operation of PV panel. From morning to noon it operates the relay (310) for 0°-23.5°south and from afternoon to evening it operates the relay (320) for 23.5° south - 0° position. When sun disappears in the evening, sensor (200) feels a dark. Control circuit operates the relay 1 and switches its output to its default position. In this terminal, the connected solenoid valve (20) has open and transfers all the working fluid (32) into the oil tank (1).
Initially, PV panel assembly is available in a position (as shown in figure 7a). In this position, hydraulic cylinder (21) remains in uncharged position or can say that in bottom position. On the other hand, hydraulic cylinder (27) has completely charged with oil (filled with oil) and sliding RAM (28) is available at top position. The PV panel assembly is in the rest position and has a facing towards the east direction. All the relay control circuits available as in turn OFF position, except of relay circuit 1. Similarly, all the solenoid valves are in the closed position except valve (20) as shown in figure 9d.
Two small cylinders (7) and (7’) are used to charge the hydraulic cylinders (21) and(27). The charging and discharging of both the small hydraulic cylinders has done alternately (as shown in a series of figure 8a, figure 8b, figure 8c, figure 8d and figure 8e). The alternate downward operation of both the plunger (8) and (8’) of small cylinders causes to move, sliding RAM (22) or both (22) and (28) in an upward direction. The upward movement of sliding RAMs is a result of force generated by the alternate downward movement of plungers. But the downward movement of sliding RAMs is a result of an opening the solenoid valves and force exerted by the weight of PV panels in a downward direction.
At a time only one small hydraulic cylinder remains in charge position. Suppose, hydraulic cylinder (7) has charged with oil and a plunger is in top position. Initially no downward force exerts on the plunger due to the empty water tank (5). As a result of that the plunger (8’) of hydraulic cylinder (7’) is placed at bottom position because of force exert on plunger due to fill water tank (5’) (as shown in figure 8a).
In the early morning when the first sunlight strikes on the light sensor (200), it triggers the relay (280) to activate the sun tracking process (as shown in figure 9a). The control circuit begins the dual axis sun tracking operation with the activation of the two relay circuits (290) and (300) of the sensor unit (270) and (220). Both the sensors (240) and (210) begin the continuous monitoring of the sun position. A metal sheet partition (240) is made to provide a shed on sensor (240) from east direction. It allows only direct sun radiation to fall on the sensor (240). When the incident light falls on it, relay (290) operates the solenoid valve (15) and allows flowing of oil (32) from the small hydraulic cylinders (7) in to the large hydraulic cylinder (21). At the same time switch (33’) gets ON and turns ON the fluid pump (13’) and a solenoid valve (9) and(10’). Fluid pump start to pump all the water of the tank (5’) into the other water tank (5) and parallel to that oil starts flowing towards the small hydraulic cylinder (7’) from the oil tank (1). Increase in weight of the water tank (5) exerts a downward force on a plunger (8). All the fluid/oil of small hydraulic cylinder (7) has transferred into a large hydraulic cylinder (21). Thus, sliding RAM (22) begins to move in an upward direction and rotates the PV panel assembly in the east - west direction. The displacement of sliding RAM (22) depends on the volume of a cylinder (21) capture by the transferred fluid. Similarly, a plunger (7) touches the switch (33) which turns ON the fluid pump (13) as well as the solenoid valves (9’) and (10). Again, the water starts transferring from tank (5) to tank (5’) and the force begins to develop on the plunger (8’). If the sensor (240), sense a sun light, relay (290) operates a solenoid valve (15) again (as shown in figure 9b). This causes the movement of oil from hydraulic cylinder (7’) to large hydraulic cylinder (21). And the hydraulic cylinder (7) charges again from the oil tank (1). In this way, sun tracking operation is carried out for whole day.
In parallel operation, sensor (210) of the relay circuit (300) works under bright condition till noon. The output of the relay (300) has connected to the relay circuit (310). A common sensor (250) connects to both the relay circuit (310) and (320). Relay (300) serves both the relay circuits sequentially. From morning to noon hours, Sensor (250) works for the relay (310) as a light activated switch and from noon to evening hours it serves the relay (320) as a dark activated switch.
When a sunlight sensing by a sensor (250), a relay (310) operates a solenoid valve (24) connected to it. With the opening of a solenoid valve (24), a sliding RAM (28) displaces in a downward direction and transfer the oil of cylinder (27) into the oil tank (1). As a result, PV panel assembly tilted toward the South direction. In this manner, the process goes on till afternoon.
In figure 7 b, the current position of hydraulic sun tracking system stated about the axial position of PV panel assembly. PV panel assembly positioned as tilted towards the south at an angle of 23.5 degrees and in east-west axis positioned as 0 degrees. Now the operation of both the small hydraulic cylinder becomes faster as earlier because the amount of oil is also required for the upward movement of sliding RAM (28) of hydraulic cylinder (27).
From noon to evening hours, Sensor (210) works under dark conditions, output of relay (300) switch to its default position at which the relay circuit (320) is connected (as shown in figure 9c). This activates the relay (320) and deactivates the relay (310). A control circuit for relay (320) uses a sensor (250) as a dark activated switch. During these hours, sun again changes its trajectory and moving towards 0 degrees from 23.5 degrees south. Under this circumstance, relay circuit (320) faces dark on its sensor (250) and operates the solenoid valve (16) to allow the flow of oil into the hydraulic cylinder (27) (as shown in figure 9d). This causes the upward movement of sliding RAM to perpendicularly orient the PV panels towards the sun.
In the evening, the PV panel assembly finally obtains a position (as shown in figure 7c). At last when the sensor (200) sense a dark in the evening, relay switches output to its default terminal and turn ON the solenoid valve (20) (as shown in figure 9d). When the valve gets open, oil from the hydraulic cylinder (21) move towards the oil tank (1). Sliding RAM (22) acquired a bottom position in a hydraulic cylinder (21). This is the beginning position of PV panel assembly from where the next day sun tracking operation would start.