TECHNICAL FIELD OF THE INVENTION
This invention relates generally to a system and method of solar tracking. More particularly the present invention relates to an improved electromechanical device for capturing solar radiation and a method thereof.
BACKGROUND AND THE PRIOR ART
Solar tracking devices are used for improve solar PV productivity by harnessing maximum solar energy and also used at radiation measurement station. Many companies manufacture solar trackers with both single axis and dual axis tracking of sun. Generally, solar tracker has characteristics as herein given below:
1. Track the device in horizontal and vertical axis of the sun with very complex mechanical and electrical design and considerable cost.
2. Auto correction facility is lacking for error occurred due to Gear deterioration, weather condition etc.
3. Most of the solar tracker used linear actuators based on an integrated stepper motor and lead screw combination.
Some of the prior arts in the present field of invention are as follows:
US8111460 provides a solar tracking skylight system for illumination, primarily including a light guide, a solar tracking controller, a two-axis tracking mechanism, an energy converter and energy storage system, and a weather protective cover. The system uses the solar tracking controller to detect the direction of the light, thereby enabling the two-axis tracking mechanism to move toward the light to facilitate the light guide in collecting light and diffusing it indoors for illumination use. The protective cover provides waterproofing, and the energy converter and energy storage system is used to store electrical energy generated by the solar energy panel for system use. External power is not needed for the system to operate and provide indoor lighting, thereby achieving the objective of saving energy and reducing carbon emissions.
US4195905 provides an automatic biaxial sun tracking mechanism for use with solar energy utilization devices. Said devices are mounted on said invention, said devices forming no specific part of said invention. The invention is comprised of three principal parts: (1) a polar shaft, (2) a declination disk, and a mount structure for positioning and supporting said solar energy utilization devices. Operation of the invention is as follows: Said declination disk, which is rotatably connected to said polar shaft, causes said mount structure, which is pivotly connected to said polar shaft and also has moving contact with said declination disk, to move in its proper declination course while said mount structure simultaneously moves in its proper right ascension course about the longitudinal axis of said polar shaft. The invention may incorporate compensating means to improve tracking accuracy. Proper operating movements are provided by suitable gearing and drive mechanisms. Said mount structure for positioning and supporting said solar energy utilization devices has three principal configurations in order to provide adequate options for receiver target location, said receiver target location being either integral with said solar energy utilization device (moving target) or external to said solar energy utilization device (stationary target).
US4548195 Automatic alignment adjustments are incorporated into the tracking control program of a concentrating solar collector apparatus to skew the alignment of aspheric, non-parabolic reflectors slightly off the half angle between the sun and fixed receivers. The automatic alignment adjustments are predetermined for each day of the year specific to the latitude of the installation and provide flexibility in the location of the reflector's pivot axes and in the design of the reflector's support framing system, reduce tracking error efficiency losses, and allow replicated reflectors and standardized support framing systems to be utilized over a wide range of latitudes.
WO2009105291 provides a solar collector tracking system is provided for maintaining orientation of multiple solar collectors to the sun to provide optimal focusing of solar radiation on a receiver. The system includes a local controller circuit board that contains a sun-tracking algorithm to control the movement of multiple solar collectors to keep them optimally focused
on the sun. The system also comprises a separate motor controller for each collector in data line connection with the local controller, and a motor for each collector in power connection with its motor controller. This isolates the local controller from the motor and protects the circuit board against power surges. The local controller allows effective field maintenance using field-replaceable components. Its circuit board is preassembled in a rugged, weather-proof cabinet to minimize the time and work required to prepare and install it in the field. The typical service life of this durable local controller is expected to be 30 years.
The prior arts provide for error arising due to mechanical and electrical inefficiency in sun tracking. Therefore there is a need to provide an improvement over the prior arts. The present invention therefore provides an improved electromechanical device for capturing solar radiation. It can be used in any type of application like solar PV, Solar Thermal, Solar Radiation Measuring station, Natural Lighting etc.
OBJECTS OF THE INVENTION
A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.
Another object of the present invention is to provide an improved electromechanical device for capturing solar radiation.
Another object of the present invention is to provide a method of capturing solar radiation using an improved electromechanical device.
Another object of the present invention is to prevent error during sun tracking.
Another object of the present invention is to provide a simple device for sun tracking.
Yet another object of the present invention is to provider an error free and efficient device.
These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
There is provided an improved electromechanical device for capturing solar radiation.
According to one embodiment of the present invention, there is provided device comprising a two axis solar tracker means; a plurality of stepper motors adapted to power and control said solar tracker means; a microcontroller integrated to said stepper motors; a plurality of optical switching means adapted to provide a reference position to said stepper motors; a gear arrangement integrated to said stepper motor thereby providing torque required; a real time clock means integrated to said microcontroller to provide day, date and time data to said microcontroller; a power supply means for providing supply to said solar tracker; a driver circuitry for interfacing said stepper motor to said microcontroller; a plurality of payloads adapted to withstand payloads, said payload rotatably connected to said solar tracker means; wherein said microcontroller preprogrammed to facilitate automatic correction on receiving input from said real time clock and configured to compensate for errors thereby mitigating effect due to sun-earth relative movement and following direction of the sun to strap maximum solar energy.
Other embodiment of the present invention provides a method of capturing solar radiation using an improved electromechanical device, said method comprising the steps of providing power supply to a solar tracker using a power supply means; activating communication link between a microcontroller unit and real time clock; providing command signals to a plurality of stepper motor for setting reference points; calculating solar azimuth and zenith angles using a microcontroller taking day, date and time data from a real time clock; comparing reference zenith and azimuth angles with actual values, repeating said step of comparison till zenith angle becomes greater than 90 degrees and further generating stepper motor command signals using said microcontroller and following direction of the sun to strap maximum solar energy.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.
Fig 1 illustrates the flowchart providing method steps used in the present invention.
Fig 2 illustrates the schematic diagram of two axis solar tracker.
Fig 3 illustrates the circuitry used in the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Accordingly in the present invention provides a device with accurate solar tracking with payload (up to 7 Kg under normal wind, temperature and pressure condition) and it may used in solar PV panel or solar radiation measurement station for radiation data collection. Aim behind invention is to mitigate the effect due to sun-earth relative movement hence follow optimum direction of the sun to strap maximum solar energy.
The invention evolve reliable and less complex mechanical and electrical design to lower the mechanical forces by wind or bad weather conditions hence better accuracy and cost effective. The device has a proper gear arrangement instead of linear actuator which used in prior patents. Open loop control and optical switches are used to compensate the error occurs due to imperfect drive guide.
Commonly available parts of old used computers are deployed to reduce fabrication cost. The device is microcontroller programmed and has no sensor incorporated for measuring the accurate position of the sun.
The device calculates the azimuth and zenith angle by pre- programming done in microcontroller and payloads connected to device moves accordingly.
The present invention is a cost effective electromechanical device that orients various payloads like Solar PV module, radiation measurement sensor etc towards the sun's direction. The device consists mainly:
1. Two numbers of stepper motors
2. Gear trains
3. Microcontroller unit
4. Real Time Clock (RTC)
5. Motor driving circuit
6. Optical switches
7. Power supply
Figure 2 shows Solar tracker chassis (1), Stepper motor-1 (2), Gear (3), Belt (4), Solar tracker base (5), Optical switch (6), Power supply (7), Stepper Motor-2 (8), Rotating shaft (9), Microcontroller unit (10), Support plate (11).
A solar tracker is devices that orient various payloads toward the sun direction. A 2-axis tracker consists of mechanical structure of the solar tracker, two no. of stepper motors, gear trains, micro-controller unit, motor driving circuit, optical switches, RTC and a power supply.
Mechanical structure is designed to allow payload attached at it have 360° freedom. Stepper motors acts as electro-mechanical actuators to drive solar tracker load. Two nos. stepper motors are used in the solar tracker structure. Motor 1 provides solar tracker payload horizontal motion and aligns it according to azimuth angle whereas motor 2 provides solar tracker payload vertical motion and aligns payload according to zenith angle hence orienting payload toward the sun. To increase the torque of the stepper motors gear train is provided in the mechanical structure. Structure has provision for accommodating microcontroller unit, RTC, motor driving circuit, optical switches and power supply.
Horizontal and vertical motion of the solar tracker payload is provided by stepper motor. A stepper motor is an electromechanical device which converts electrical pulses into discrete mechanical movements. The shaft or spindle of a stepper motor rotates in discrete step increments when electrical command pulses are applied to it in the proper sequence. The sequence of the applied pulses is directly related to the direction of motor shafts rotation. The speed of the motor shafts rotation is directly related to the frequency of the input pulses and the length of rotation is directly related to the number of input pulses applied. A stepper motor can be a good choice whenever controlled movement is required and a holding torque is required. In this solar tracker stepper motors capabilities are utilized to have an open loop control mechanism to convert digital logic into the mechanical movements. Stepper motor also provides the required holding torque for the solar tracker payload.
Electric command pulses for stepper motor rotation and control are generated in microcontroller assembly. These are generated by calculation of the azimuth and zenith angle through empirical formulas. Microcontroller uses the day, date, time, latitude and longitude for the calculation of the azimuth and zenith angle. RTC is used for providing day, date and time. Microcontroller communicates with RTC through I2C Communication and gets the required inputs for the calculation. Microcontroller has limited capability in term of sourcing or sinking the current and hence command pulses from the microcontroller are not capable of driving stepper motor. To interface the stepper motor with the microcontroller a driver circuit is used.
The driving circuit after several levels of amplification supplies the required command signals for the stepper motor. For the creation of reference point for the calculation of command signal for the stepper motor 2 optical switches are used in the solar tracker. Optical switches are placed on the horizontal and vertical shafts in order to get vertical and horizontal reference points. They communicate through voltage signal to microcontroller and set the reference point for further calculations. The solar tracker needs 5V and 3.3V power supply for its operation. These voltages are provided by the power supply in the solar tracker.
PROCESS FLOW
1) AC supply provided to the power supply which converts it to 5V and 3.3V as per requirements of the solar tracker.
2) Microcontroller unit and RTC are activated and starts communicating.
3) Microcontroller unit initiates the command signals to the vertical stepper motor and keep on rotating it till the vertical optical switch operates and sends voltage signal to stop stepper motor.

4) Microcontroller unit initiates the command signals to the horizontal stepper motor and keep on rotating it till the horizontal optical switch operates and sends voltage signal to stop stepper motor.
5) After setting of reference points in step 3 and 4 microcontroller communicates with RTC to get the day, date and time.

6) Calculations are done by microcontroller and solar azimuth and zenith angles are calculated.
7) Stepper motor command signals are generated by comparing the actual and reference zenith and azimuth angles.
8) This process keeps on repeating till zenith angle becomes greater than 90°. After zenith angle reaches 90° tracker comes back to its original position and auto correct its error.
Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. However, all such modifications are deemed to be within the scope of the claims.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.

WE CLAIM:
1. An improved electromechanical device for capturing solar radiation, said device
comprising:
a two axis solar tracker means;
a plurality of stepper motors adapted to power and control said solar tracker means;
a microcontroller integrated to said stepper motors;
a plurality of optical switching means adapted to provide a reference position to said stepper motors;
a gear arrangement integrated to said stepper motor thereby providing torque required;
a real time clock means integrated to said microcontroller to provide day, date and time data to said microcontroller;
a power supply means for providing supply to said solar tracker;
a driver circuitry for interfacing said stepper motor to said microcontroller;
a plurality of payloads adapted to withstand payloads, said payload rotatably connected to said solar tracker means;
wherein said microcontroller preprogrammed to facilitate automatic correction on receiving input from said real time clock and configured to compensate for errors thereby mitigating effect due to sun-earth relative movement and following direction of the sun to strap maximum solar energy.
2. Device as claimed in claim 1 wherein said microcontroller is preprogrammed to measure position of sun by calculating azimuth angle and zenith angle.
3. Device as claimed in claim 1 wherein said payload is configured to undergo a rotation of 360 degree.
4. Device as claimed in claim 1 wherein said stepper motor configured to provide solar tracker payload horizontal motion and align it according to azimuth angle.
5. Device as claimed in claim 1 wherein said stepper motor adapted to provide vertical motion to said solar tracker payload and align according to zenith angle thereby orienting payload toward the sun.
6. A method of capturing solar radiation using an improved electromechanical device, said method comprising the steps of:
providing power supply to a solar tracker using a power supply means;
activating communication link between a microcontroller unit and real time clock;
providing command signals to a plurality of stepper motor for setting reference points;
calculating solar azimuth and zenith angles using a microcontroller taking day, date and time data from a real time clock;
comparing reference zenith and azimuth angles with actual values, repeating said step of comparison till zenith angle becomes greater than 90 degrees and further generating stepper motor command signals using said microcontroller and following direction of the sun to strap maximum solar energy.
7. An improved electromechanical device for capturing solar radiation as herein described and illustrated with reference to given description read along with the accompanying drawings.
8. A method of capturing solar radiation using an improved electromechanical device as herein described and illustrated with reference to given description read along with the accompanying drawings.