FIELD OF INVENTION
The present invention generally relates to solar photovoltaic (SPV) system having
SPV-arrays to provide solar energy and power the utilities. More particularly, the
invention relates to a load-controllable solar photovoltic system to constantly maintain
critical loads and switch off the non-critical loads depending on power availability.
BACKGROUND OF THE INVENTION
The solar photovoltaic (SPV) systems having an array of SPV-cells are known which
provide power to utilities by using solar energy. However, the solar insolation varies
from place to place and hour to hour in a day. Accordingly, a stand alone SPV system
for any load is usually overdesigned so that the power supplied to the load is
independent of the sunlight available at that place. This requires usage of a very large
battery back up for the SPV system, and increases the cost of the system. However,
by prioritizing the load into essential and optional categories, it is possible to optimize
the system configuration, for example, where the load is required to operate in day
only. This can be done by controlling the operation of the loads depending upon the
availability of the sunlight.
US patent publication no. 2002/0108648 A1 by Nixon et al, entitled "Solar Power
Management system" discloses a SPV system, wherein the main emphasis has been
given on ensuring that the correct polarity of the SPV modules getting connected to a
controller Box.
US patent publication 2008/0036440A1, teaches a microprocessor controlled
Maximum Power Point Tracked for smaller loads through programming.

US patent no. 6037758 to Richard Perez, disclosed a load controller and method to
enhance Effective capacity of a Photovoltaic Power Supply. In this case the emphasis
is given on grid connected load and its management through an algorithm so that SPV
system can maximize its output. However, it is noted that for discrete and independent
standalone loads powered through an SPV array, the prior art teaches very little
technical information.
OBJECTS OF INVENTION
It is therefore an object of the invention to propose a load-controllable solar photovoltic
system to constantly maintain critical loads and switch off the non-critical loads
depending on power availability, which eliminates the disadvantage of prior art.
Another object of the invention is to propose a load-controllable solar photovoltic
system to constantly maintain critical loads and switch off the non-critical loads
depending on power availability, which allows reduction in the size of battery back-up
vis a vis the manufacturing cost of the system.
SUMMARY OF THE INVENTION
According to the invention, a load priority controller for a SPV -system is provided.
The load controller segregates the loads in five priorities and gives the highest priority
to emergency lights. The solar modules and the loads are configured, interconnected,
and disposed such that at noontime, all the loads are supported by the generated
electricity by the solar modules. A sensor module keeps on monitoring the sun
radiation and depending on the intensity of the sun radiation from morning to

noontime; the loads are switched on sequentially so that at the noontime all the loads
are on. In the afternoon, the loads are switched off in a reverse sequence. The system
works fully on automatic mode. The low priority loads can also be supported by normal
electric supply on availability. According to the invention, a Load priority controller is
provided for the solar SPV arrays. The controller for the SPV Arrays electronically
tracks the power generated by the array and switches on/off the load in 5 steps
depending upon the output from the array, thereby maximizing the power usage from
array without increasing the size of the battery. The system is thus enabled to support
only the critical load with highest priority.
BRIEF DESCRIPTION OF THE ACCOPANYING DRAWINGS
Figure 1- Shows a schematic diagram of a load controller solar photovoltic system
according to the invention.
Figure 2- Shows a circuit diagram of a load- controllable SPV system of Fig-1.
DETAILED DESCRIPTION OF THE INVENTION
For a typical load priority controller, the specification of the constituting components
are given below:
1. SPV Array:
2. Inverter/charge controller:
3. Load Priority Control Module: Consists of
i) Input Points for Inverter, Line AC and sensor module
ii) Control circuitry for multistep step load priority controller
iii) Sensing and switching circuitry

iv) Relays for connecting and disconnecting loads
4 at least one solar intensity sensor.
5. Loads: multiple
A schematic representation of a load priority SPV system is shown in Fig. 1. In this
system, the loads are segregated for example into five priorities (L1, L2, L3, L4, L5).
Depending on the intensity of the sun from morning to noontime, the loads are
switched on sequentially and at noontime all the different loads are on. Similarly, in the
evening, the loads are switched off in a reverse sequence depending on their priority.
The load with highest priority is kept always on during daytime and supported by the
batteries. During clouds depending on the amount of shading, the loads are selected
accordingly. The circuit schematic is shown in Fig. 2. A sensor module (1) monitor the
solar intensity and connects the loads through a plurality of relay (R1, R2, R3, R4, R5)
depending on the intensity and priority. If the intensity is low, then only load (L1)
through the relay (R1) is kept connected. As soon as the intensity is sufficient to feed
loads L2,L3,L4 and L5, they are also switched on sequentially through relays (R2, R3,
R4 and R5) and so on. Similarly, the relays (R1, R2, R3, R4, and R5) are switched off
in reverse order, if the intensity becomes lower at any time. The load transfer is fully
automatic. The lower priority loads is supported by normal electricity (grid supply) if
available at that location. The grid supply on its availability is connected to normally
open contacts of the relays (R1, R2, R3, R4 and R5).

WE CLAIM:
1. A load-controllable solar photovoltic system to constantly maintain critical loads and
switch off the non-critical loads depending on power availability, comprising:
- an array of solar photovolic modules interconnected and disposed in a frame such
that the frame when positioned to face the sun allows the array to receive intensity of
sunlight and produce solar energy;
- at least one inverter being connected to the solar photovoltic (SPV) supply a sensor
module to constantly monitor the solar intensity; and a multi-step priority control
module to automatically switch on or switch off the critical and non-critical loads based
on inputs from the sensor module.

2. The system as claimed in claim 1, wherein the multi-step load priority control
module comprises an input port for establishing connection with the inverter, a control
circuit means, a switching means, and a plurality of relays for connection or
disconnection of the critical and non-critical loads.
3. -A load-controllable solar photovoltic system to constantly maintain critical loads
and switch off the non-critical loads depending on power availability as substantially
described and illustrated herein with reference to the accompanying drawings

A load-controllable solar photovoltic system to constantly maintain critical loads and
switch off the non-critical loads depending on power availability, comprising an array
of solar photovolic modules interconnected and disposed in a frame such that the
frame when positioned to face the sun allows the array to receive intensity of sunlight
and produce solar energy; at least one invester acting as a charger being operably
connected at one end to the solar photovoltic (SPV) supply, and at the other end to a
grid supply line; a sensor module to constantly solar intensity; and multi-step priority
control module to automatically switch on or switch off the critical and non-critical
loads based o inputs from the sensor module.