Installation of 200W solar panel in a house.
India lies in the sunny regions of the world. Most parts of India receive 4–7 kWh (kilowatt-hour)
of solar radiation per square meter per day with 250–300 sunny days in a year. The highest
annual radiation energy is received in western Rajasthan while the north-eastern region of the
country receives the lowest annual radiation.
The features that make it an attractive and a lucrative option include global distribution,
pollution free nature, and the virtually inexhaustible supply.
Fig1: A 270W polycrystalline module
3 key elements in a solar cell form the basis of the technology:
1) Semiconductor which absorbs light and converts it into electron-hole pairs.
2) Semiconductor junction, which separates the photo-generated carriers (electrons and holes)
3) Contacts on the front and back of the cell that allow the current to flow to the external
The two main categories of technology are defined by the choice of the semiconductor:
Either crystalline silicon in a wafer form or thin films of other materials.
A grid interactive roof top solar PV system comprises the following equipment:
1) SPV Power Source
2) Inverter (PCU- Power Conditioning Unit)
3) Mounting Structure
4) AC and DC Cables
5) Earthing equipment /material
6) Junction Boxes or combiners
7) Instruments and protection equipment (disconnect switches and fuses)
1) SPV Power Source:
Solar Panel as in fig 1
2) Inverter (PCU- Power Conditioning Unit)
Fig 2: Solar Power Conditioning Unit
It is the most important component.
1) The inverter converts the DC power of the array into AC.
2) The output of the inverter synchronizes automatically its AC output to the exact AC voltage
and frequency of the grid.
A Solar inverter or PV inverter is a type of electrical inverter that is made to change the direct
current (DC) electricity from a photovoltaic array into alternating current (AC) for use with home
appliances and possibly a utility grid.
Solar inverters may be classified into three broad types:
• Stand-alone inverters, used in isolated systems where the inverter draws its DC energy from
batteries charged by photovoltaic arrays and/or other sources, such as wind turbines, hydro
turbines, or engine generators. Many stand-alone inverters also incorporate integral battery
chargers to replenish the battery from an AC source, when available. Normally these do not
interface in any way with the utility grid, and as such, are not required to have anti-islanding
• Grid tie inverters, which match phase with a utility-supplied sine wave. Grid-tie inverters are
designed to shut down automatically upon loss of utility supply, for safety reasons. They do not
provide backup power during utility outages.
• Battery backup inverters. These are special inverters which are designed to draw energy from
a battery, manage the battery charge via an onboard charger, and export excess energy to the
utility grid. These inverters are capable of supplying AC energy to selected loads during a utility
outage, and are required to have anti-islanding protection.
Protection and Controls:
1. Inverter is provided with islanding protection to isolate it from the grid in case of no supply,
under voltage and over voltage conditions so that in no case there is any chance of accident.
In case of a power cut, the PV module too ceases to provide any power. In such a case, the
backup DG (Diesel Generator) set is utilized.
2. In addition to above, PV systems is provided with adequate rating fuses, fuses on inverter
input side (DC) as well as output side (AC) side for overload and short circuit protection and
disconnecting switches to isolate the DC and AC system during maintenance.
3) Mounting Structure:
The frame is made up of anodized aluminum; its thickness on the surface of the frame is 25
micron. The component frame have four sets of screws and one set of holes connecting to the
ground, completely meet the international authority’s demand.
Fig 3 : Mounting Structure
4) AC and DC Cables:
Fig 4: AC/DC wire concept
5) Earthing equipment /material:
6) Junction Boxes or combiners:
Junction box has good water-proof and sealed functions
7) Instruments and protection equipment (disconnect switches and fuses):
Seal material: Anti-aged EVA (Encapsulated Resin) and anti-climate good TPT (Tedlar-Polyester-
On the solar module, connect the positive home run cable to the positive output cable, and
connect the negative cable to the negative of the home run cable pushing collectors all the way
Fig 5 : Connection b/w wires and their encapsulation
When you have made direct connections, use a digital multimeter to measure the voltage and
current output of the module. Record the measurement results.
• This information is needed to check for solar module wiring mistakes, and it will also be
needed by the electrician who makes the connections to the inverter.
Then the wire is connected to the Solar Power Conditioning Unit, which converts Dc power
of the module into AC which synchronizes automatically its AC output to the exact AC
voltage of the grid.
The devices are connected with the inverter. The extra supply, if left is sent to the grid, for
other’s use, which the producer is paid for, by the government.
Fig 6: Illustration
The power generating capacity of a photovoltaic system is denoted in Kilowatt peak (measured
at standard test conditions of insolation 1000 W/m2
Standard Flow in a house:
Fig 7: Working model and use of excessive power produce to power grid.
Steps to follow:
Step 1: Mounting of the Solar Panels on the roof, tilted at an angle equal to latitude of the place
in south direction. The mounting has been discussed in the Fig 3.
1. Mounting with Bolts
The module must be attached and supported by at least four bolts through the indicated
2. Mounting solar modules with bracket on flat roof and ground
Fasten bracket on flat roof or ground first, fasten solar modules on bracket, use nuts to fasten
bracket. The bracket would endure 20 years, and is made of anticorrosive material.
Temperature zinc steels and Stainless steel is recommended.
The recommended standoff height is 5 cm. If other mounting means are employed this may
affect the UL Listing.
Direction of module installation: PV module are rectangle shaped; PV module array
longitudinal installation (the way that installs the module by long side longitudinal) is mostly
used because the transverse installation (the way that installs the module by long side
transversely) has less rain cleaning ability.
Exercise caution when wiring or handling modules exposed to sunlight. Completely
cover all modules with an opaque material during installation to prevent electricity from
When disconnecting wires connected to a photovoltaic module that is exposed to
sunlight, an electric arc may occur. Arcs can cause burns, start fires or otherwise create
safety problems. Exercise caution when disconnecting wiring on modules exposed to
Do not use mirrors or other hardware to artificially concentrate sunlight on the module.
Use appropriate safety equipment (insulated tools, insulating gloves, etc) approved for
use on electrical installations.
The module should not be shaded at any time of the day.
If the module is in shade it, suffers from shading effect:
Shading effects on Solar PV systems:
From case studies it is known that PV systems with the same nominal power generate quite
different energy yields due to different shading patterns. The common problems are:
1. Reduction of power output: As the insolation is reduced by shading we get a reduced photo
current. As cells are in series connection, the current for all the cells is reduced.
2. Thermal stress on the module: Depending on the level of shading, the PV generator circuit
and the load the voltage of shaded cells might reverse. In this case they operate in the blocking
state as a resistive load. The losses in the individual cell can increase the cell temperature
dramatically and overheating might occur.
In order to overcome some of the problems related to shading, by-pass-diodes are connected
parallel to a number of solar cells. Under normal operating conditions the diodes are blocked as
compared to the voltage generated by the cells. When shading occurs the reversal of the voltage
can be observed in that specific section and now the by-pass diode in parallel will conduct the
current. The results are:
The current of the unshaded section flows through the by-pass diode and the power/voltage
characteristic shows a second local maximum
The shaded cell is only loaded with that fraction of power produced by the remaining unshaded
cells of that section
The use of by-pass diodes results in some drawbacks as well:
• Higher cost for the module production and assembly problems of the by-pass diodes
• Losses in the by-pass diode due to shading
• Matching problems between the solar inverter and the photovoltaic generator because of the
second local power maximum might not be included in the range of operation of the inverter.
Do not install the module near equipment or in locations where flammable gases can be
generated or collected.
Step 2: Testing:
It is best to test the solar array before mounting to avoid having to take it down again. To do
this, turn it over and lay it on the ground face up. Make sure you have enough people helping to
avoid twisting or dropping the solar array.
Using a multimeter set to an appropriate DC Voltage range, measure the voltage between the
two cores of the output cable. It should be equivalent to the open-circuit voltage of onesolar
panel multiplied by the number of solar panels in series. That is, about 20 V for a 12 V system,
40 V for a 24 V system and 80 V for a 48 V system. 80 Volts is a dangerously high voltage, and 40
Volts is enough to give a nasty shock in the wrong circumstances; take care when performing
these measurements and cover the solar array with an opaque material before connecting the
meter if in any doubt.
Once this test is complete it is advisable to make the solar array safe before lifting it into place.
There are two ways of doing this; either cover it with an opaque material or connect the cores of
the output cable together to short-circuit the solar array. This will not cause any damage and is
Step 3: Electrical Installation
There is the grounding hole and grounding marking along either edge of the frame indicating a
ground bonding location. Frames must be grounded and bolts, washer must be of stainless steel.
The wire must have no nick. Make the grounding wire connect to the bolt and tighten it.
Ensure that positive and negative DC wires run closely together avoiding loops.
Completely cover system modules with an opaque material to prevent electricity from
being generated while disconnecting conductors.
Do not touch bare conductors or other potentially energized parts.
Inverter output is mains voltage AC and can be lethal. Treat as for any other mains
Solar arrays generate electricity when exposed to the sun, whether connected to
control equipment or not. Treat solar array output cables as live and cover solar
array when making connections.
The open circuit voltage of a solar array is significantly greater than the system
voltage. For example a 48 Volt array can have an open circuit voltage of nearly 90
Volts, which can be lethal to children, the elderly or anyone with a heart condition.
Batteries can produce currents of hundreds or even thousands of amps giving rise to
the risk of fire. Take great care to protect the battery terminals from shorting by tools
and remove all jewellery.
Use such protections for electrical installation:
Fig 8: Photovoltaic Fuses:
Fig 9: Photovoltaic Fuseholders :
Fig 10: Surge Protective Devices
Fig 11: PV Safety Solutions
Fig 12: Power Electronics Solutions
Fig 13: Wire Management
Lead acid batteries contain dilute sulphuric acid and liberate hydrogen when charging.
Observe the following precautions:
Take great care when filling batteries with electrolyte; wear suitable protective clothing
including eye protection and carry out in a well ventilated area, preferably outdoors.
Do not smoke near batteries and ensure room is well ventilated.
Take care to prevent arcing near battery terminals as explosion may result.
Keep first aid and eyewash equipment close at hand when working on batteries.
Batteries and solar arrays present certain hazards in handling as follows:
Lead acid batteries are extremely heavy. Use appropriate lifting gear and ensure adequate
help is available.
Most solar panels are made from glass. Treat as fragile.
Installing solar arrays may involve working at height. Observe all necessary precautions and
employ the services of a qualified rigger or roofer if necessary.
Batteryless grid type system vs Off grid system:
Batteryless grid- tied systems are simple to understand and design, with only two primary
components: PV modules and an inverter that feeds AC electricity back into the electrical
system to offset some or all of the electricity otherwise purchased from the utility. These
systems are cheaper, easier to install and maintain, and operate more efficiently than battery-
based systems of comparable size. Their main drawback is that when the grid goes down, they
cannot provide any energy for you to use. If the grid in your area is mostly reliable and outages
are infrequent, these systems can offer the best payback for the least price.
Installation of the battery may be as simple as taking a wet-charged or sealed battery out of a
box and placing it on a firm and level surface. Alternatively it may involve mixing acid to the
right concentration and filling the batteries on site.
The batteries need to be mounted such that they are secure, i.e. they can’t fall over, they are
protected from unauthorised access and away from sources of ignition. The room or container
that they are in should be ventilated so as to allow the hydrogen produced by charging to
escape. This applies even to sealed batteries as they are able to vent excess gasses should the
charging system malfunction.
Practically this is most likely to mean one of two things:
• On a solid floor or racking within a locked and well ventilated room.
• In a purpose designed battery box.
It is important that it is possible to gain access to the batteries in order to perform maintenance.
In the case of a sealed battery this means the terminals, but for a vented battery it may mean
access to the level markings on the side and the filling caps.
Sealed batteries of both gel and AGM types are always supplied filled and usually charged. It
may be necessary to give them a refresher charge before putting them into service. This
should be performed with a regulated mains charger if possible. If this can’t be done for any
reason then the system should be used as little as possible for the first 24 hours in order to
allow the batteries to become fully charged.
When batteries are supplied already filled with electrolyte, they are usually charged and are
treated in the same way as described for sealed batteries.
Some wet batteries are supplied dry-charged. This means that they have been charged, the
electrolyte emptied out and the battery dried and sealed. It is important that it remains
sealed if it is to be stored before being put into service. Once it is required, the seals should
be removed and dilute sulphuric acid of the correct specific gravity used to fill the cells to the
filling mark. The acid will usually be supplied with the battery. The battery should then be
allowed to stand for a period of time to allow any air to escape.
A dry charged battery, once filled, will achieve about an 80% state of charge. For this reason it
must be charged before putting into service. Normally this will be specified by the
manufacturer as being at a specific voltage for a particular amount of time. Again it should be
accomplished by means of a mains operated charger if possible, although it may be possible
to use the solar system to provide this charge if the loads are disabled for a certain amount of
Dry uncharged batteries
Sometimes batteries, normally large cells, are supplied in a dry uncharged state. It is critical
that the manufacturer’s instructions are followed to the letter as the initial charge is
important to the formation of the plate structure. Normally they will be filled as with dry-
charged batteries and then subjected to an extended charge, often taking some days. This
must be performed with the correct type of charger and it is advisable to avoid purchasing
batteries in this state if possible. If wet batteries have to be transported by sea or air the best
option is to obtain them in a dry-charged state with the acid in suitable packaging as advised
by your shipping company.
It may sometimes be necessary to mix your own electrolyte from concentrated sulphuric acid
and distilled water. This should be avoided unless absolutely necessary, for instance in
developing countries where it may be impossible to purchase ready made electrolyte and
shipping it from the manufacturer is impractical. It is essential that the sulphuric acid and
distilled water are of the highest purity.
Before you start collect together the following items:
Safety clothing, including a chemical splashes apron, face shield and suitable gloves.
A suitable non-metallic mixing vessel and stirrer. Glass is ideal although you may have to
use whatever is available such as a plastic bucket and wooden stick. I write from
experience on this.
A glass thermometer calibrated from at least 10 - 80º C.
A battery hydrometer, which can be bought from a battery specialist or tool shop.
A container to hold the finished electrolyte. A plastic drum is ideal and should be marked
“Sulphuric acid. Highly corrosive.”
It is important that you always add acid to water and never the other way round. In this way,
you are never diluting concentrated acid, which can cause it to boil explosively with very
serious consequences. Mix a little at a time, add the acid in small amounts and stir
thoroughly. Bear in mind that it will become hot.
Each time you add some acid, check the specific gravity by drawing a little electrolyte into the
hydrometer and expelling it, then drawing in enough just to lift the float. Read off the specific
gravity from the scale and record. Then measure the temperature of the electrolyte and add
0.001 to the reading on the hydrometer for each degree Celsius above the specified