FIELD OF INVENTION
The present invention relates to a cloud sensing device to energize motor drive
for sensor based dual axis solar tracker.
BACKGROUND OF THE INVENTION
The conventional way of energy generation is based on fossil fuels, create
pollution and disturb ecological balance. As the solar energy is available free of
cost and abundantly, it can be harnessed to meet the energy needs. The initial
cost of solar energy is, however, quit high. In Photo Voltaic route, this includes
the cost of solar photovoltaic modules and balance of system. Costs must be
reduced in order for the photovoltaic industry to expand further leading to
replacement of diesel, and to enter exports and water pumping markets. Both
the areas of cost reduction of PV modules and balance of systems must be
explored so that the cost of solar energy generation can be brought down and
the PV systems become viable.

It has been observed that in the total solar system, the Solar Photo Voltaic
modules form a major part of the cost. Therefore, efforts are to be made to
maximise energy generation from a specific installed capacity of the SPV system.
Out of several factors affecting the energy generation for a specific installed
capacity of modules, the means for tracking the incident rays from sun plays an
important role. The improvement in the energy generation therefore is
substantially dependent on accurate and consistent sun tracking. It has been
observed that a fixed-array solar module system use about 30 percent more
modules than a two-axis solar tracking system, for generation of equal annual
energy. Inspite of having several such advantages, the use of in prior art solar
trackers is not prevalent particularly in flat panel solar installations due to cost
and complexities of the tracking mechanism.
Tracking of sun for enhancement of power generation allows incidence of sun
ray at a perpendicular direction on the photovoltaic modules which in turn
increases the output significantly.

Domes having multiple sensors with comparator are also known to be used to
drive sun tracking motors (Patent EP81303691.0 dated 13/08/1981). Sensor
devices have- also been used to point the solar absorber to the sun (US4586488
May 6, 1986). Single sensor system with counterweight (US4510385 dated April
9, 1985), sensors with shadow plate (US4672191 dated 09/06/2009) to cast
shadow on the sensor in case of misalignment have been used to align the
position of the sun. To improve the accuracy of the tracker, advanced and
intelligent systems having shape memory element (EP1884724A1 dated
06/02/2008), light guiding element (US20110073748 dated 31/03/2011), optical
sensor holder (KR100904242 dated 25/062009) have been evolved.
These sensor based systems suffer from lack of clarity during low illumination
conditions like during clouds, foggy or rainy season in the daytime. A supporting
system is required to guide these systems under low illumination conditions.
However, for long period of non sunny days, the battery used for powering the
tracking mechanism also gets drained-out and the tracking mechanism fails.

The solar photovoltaic (SPV) modules/ arrays are known to be installed at a fixed
tilt angle at a latitude angle on the supporting structures. This does not produce
optimum output and results in loss due to lack of its full capacity utilisation.
Incorporation of a dual axis tracking mechanism is likely to increase the power
output compared to the existing fixed tilt systems by maximising power through
tracking of Sun. The installed capacity of SPV modules can be reduced or energy
generated can be increased from a specified installed capacity by using a Solar
Tracking mechanism.
Dual axis tracking systems with a high degree of accuracy (~0.01 degrees) and
using complex techniques like Maximum power point tracking (MPPT), and
feeding and feeding Suns path into the Concentrated Photovoltaic (CPV) system
tracking device in flat panel photovoltaic systems, although known, the cost of
such a complex tracking device is so high that only when it is installed on a
~10KW CPV on a single tracking device, that this becomes viable. But this makes
the system very cumbersome and heavy. Consequently, in MPPT, during cloudy
season and at places where dust levels are high, the quantum of power

generation lost in tracking the maximum power point is more than the gain. Also,
in the case of feeding the path of the sun rays in absence of any feedback, the
system is required to be frequently reset as it gets out of focus sometimes and in
absence of feedback, the system does not try to correct itself, reducing the
output.
OBJECTS OF THE INVENTION
It is therefore, an object of the present invention to propose a cloud sensor
device to energize the motor drive of the existing sensor based dual axis solar
tracker during low illumination.
Another object of the present invention is to propose a cloud sensor device to
energize the- motor drive of the existing sensor based dual axis solar tracker
during low illumination which provides fault free operation during different
illumination.

SUMMARY OF THE INVENTION
Flat panel SPV is configured by initially designing a circuit to power two motors
(used in automobile sector) which work on 12V and consume less power and
very rugged. The circuit has two sets of separate LDRs (here LDR2 & LDR3 as
one set and LDR4 & LDR5 as other set) which are facing the sun. The earths
rotation makes sun move ~4 degrees every minute from east to west for a total
of 180 degree movement during daytime. Also, the seasonal movement is + 23.5
degrees~47 degrees during the year.
Hence, the circuit is calibrated to be very sensitive (~1 degree accurate) in east
to west direction and slightly less accurate (~2 degree) from' north to south. The
movement is bidirectional with a single DC motor, making the system very
inexpensive. Also, as the circuit is made out of discreet Electronic components, it
is very rugged and cheap. But, that does not compromise the overall gain from
the system ~25-30%(refer the data/graph given in fig.3).

The system has been monitored for longer duration and it was found that, during
cloudy season, there was continuous hunting for the sun due to higher accuracy.
Initially, the accuracy was reduced, but this reduced the gain and the problem
was not eliminated altogether. Hence, a control circuit was developed to keep
the system operational during normal condition, but to stop the same from
continuous hunting during cloudy season. The system has been kept in filed and
observed for a period of almost one year and it was observed that the gain over
flat panel without tracking is much more.
In the present embodiment, a low illumination sensor device is incorporated,
which disables the tracking during low illumination conditions and saves the
battery from discharging. The tracking is restored as soon as the sunlight
becomes intense.
The present invention is provided with a cloud sensing device to energize motor
drive for sensor based dual axis solar tracker comprising an integrated network
of a plurality of light dependent resistors (LD, LDR1, LDR3, LDR4, LDR5), a
plurality of integrated circuits (1A, 2A, 2B, 3A, 3B), a plurality of transistors (TR1,

TR2, TR3, TR4, TR5, TR6, TR7, TR8, TR9), a plurality of fixed resistance and
variable resistance (R1, R2, VR1, VR3, R3, R4), at least one relay and a 12v
battery. The resistance of the light dependent resistors (LDS) is proportional to
light incident on it and functions at milliamperes, engages the integrated circuit
along with a fixed resistance. The resistors act as a sensor device whose output
is amplified by the IC which in turn operates a transistor to control a relay,
wherein the relay enables the tracking-circuit to get energize the motor to obtain
an amplified output.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
Fig 1: shows a schematic diagram of the dual axis tracker.
Fig.2: shows an electronic circuit for the controller.
Fig.3: shows a graphical presentation of a comparison of Isc of a 12V
.70W SPV module with an without dual axis tracking system.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
The SPV System (1) with dual axis tracking mechanism of the invention,
comprises:
1. Solar photovoltaic module (2) with mounting structure having geared
motors (3, 4) for movement around horizontal and vertical axis.
2. Housing for photoelectric sensors.
3. An electronic controller with battery (6).
The system (1) is shown in Fig.1. The system (1) has two pairs of photoelectric
sensors for control of rotation of DC motors (3, 4) on horizontal and vertical axis.
The chance of its malfunction of the system during cloudy period is eliminated by
incorporating an additional light sensor device to provide illumination level to the
controller (5). This also minimises the power consumption by the tracker motors
(4).

Figure 1 also shows the various components of the Sensor Based Dual Axis
Tracking System with Low Illumination sensor device. The system has SPV
modules which are mounted on a movable structure with arrangement of
rotation about horizontal and vertical axis. It is coupled with two nos. of DC
geared motors (3, 4) for E-W (around vertical axis) and N-S (around horizontal
axis) tracking. While the E-W movement is rotational type, N-S movement is
through a linear actuator arrangement. The movement of the motors is
controlled electronically through ICs by a sensor based circuit (Fig. 2). Since, the
circuit is very sensitive, a low illumination sensor device is mounted horizontally
either in the same housing of the sensors or in an independent housing. The
feedback from the low illumination sensor device to energize the motor drive
during cloudy, foggy or rainy weather and protects the battery from draining.
WORKING OF THE SENSOR DEVICE BASED DUAL AXIS TRACKING
SYSTEM WITH LOW ILLUMINATION SWITCH
The system is based on a photo sensors device (Light dependent resistors-LDRs)
whose resistance is proportional to the light incident on it and functions at

milliamperes (as compared to MPPT which uses the output of the SPV itself and
which requires the output of the system to be shut down during that period).
When an LDR is used in an OPAMP IC Circuit (here IC1) along with a fixed
resistance, it-acts as a sensor device whose output is amplified by the IC which
in turn operates a transistor to control a relay.
The relay ensures that the tracking circuit gets powered only when sufficient
sunlight is available. When clouds are there, and the sunlight is not direct, the
system stops.
When an LDR is used alongwith another LDR, both being kept at an offset angle
from the incident light (Set of LDR2 & LDR3 and LDR4 & LDR5), the output to
the motor is zero when sunlight is incident equally on both the LDRs. As soon as
the movement of the earth changes the direction of the sunlight, the motor gets
the amplified output from the circuit (either positive or negative depending on
the direction of the sun), and system tries to remove the imbalance by moving
the tracker by the motors so that the incident light on the two sets of LDRs
equals. This makes the system face the sun like a sunflower.

WE CLAIM
1. A sensing circuitry device to energize dual motor drive of sensor based
dual axis solar tracker system during low-solar incidence periods, the
device comprising:
- a plurality of light dependent resistors (LD, LDR1, LDR3, LDR4,
LDR5) to receive scattered low-solar incidence, connected to a
plurality of fixed and variable resistance (R1, R2, VR1, VR3, R3, R4)
to generate low milliamperes current and operatably connected to
a plurality of integrated circuits (1A, 2A, 2B, 3A, 3B) to amplify the
miliampere to be fed to a plurality of transistors (TR1, TR2, TR3,
TR4, TR5, TR6, TR7, TR8, TR9) to control a relay, characterized in
that the solar tracker system is operated by said dual motor drive
connected to the ciruitory device, and in that the relay is connected
to the transistor and activates the solar tracking system under low-
sunlight conditions.

2. The device as claimed in claim 1, wherein the plurality of LDRs and VRs
are disposed in the circuitry device to receive scattered low solar
incidence;
3. The device as claimed in claim 1, wherein the LDRs and VRs generate a
low miliampere energy from solar incidence.
4. The device as claimed in claim 1, wherein the generated low ampere
currents are fed to ICs to amplify the current.
5. The device as claimed in claim 1 wherein the amplified current from the
ICs is fed to the transistor to control the relay.
6. The device as claimed in claim 1, wherein the relay activates the controller
of the solar tracker system.

ABSTRACT
A sensing circuitry device to energize dual motor drive of sensor based dual
axis solar tracker system during low-solar incidence periods, the device
comprising a plurality of light dependent resistors (LD, LDR1, LDR3, LDR4,
LDR5) to receive scattered low-solar incidence, connected to a plurality of
fixed and variable resistance (R1, R2, VR1, VR3, R3, R4) to generate low
milliamperes current and connected to a plurality of integrated circuits (1A,
2A, 2B, 3A, 3B) to amplify the miliampere to be fed to a plurality of
transistors (TR1, TR2, TR3, TR4, TR5, TR6, TR7, TR8, TR9) to control a relay,
characterized in that the solar tracker system is operated by said dual motor
drive connected to the circuitry device, and in that the relay is connected to
the transistor and deactivates the solar tracking system under cloudy/low-sunlight conditions.