TESLA PHOTOVOLTICS
SOLAR ENERGY : An
Overview
[Type the document subtitle]
Anum Pervez
Tesla provides a secure solution to your power future, here is a small overview of technology being
implemented by The Company.
Table of Contents
ABSTRACT:................................................................................................................................................. 5
Chapter 1 : THE PHOTOVOVTIC THEORY: ..................................................................................................... 6
1.1
BASIC PHENOMINA: ...................................................................................................................... 7
1.1
MATERIALS EMPOLOYED: ............................................................................................................. 7
1.2
CORE OPERATIONS:....................................................................................................................... 7
1.3
SOLAR CELL: .................................................................................................................................. 7
1.4
THE CONVENTIONAL SOLAR CELLS STRUCTURE ........................................................................... 7
1.5
SOLAR PANEL: ............................................................................................................................... 8
1.6
TYPES OF SOLAR PANAL: ............................................................................................................... 8
1.6.1
POLYCRYSTALLINE MODULES................................................................................................ 8
1.6.2
MONOCRYSTALLINE MODULES ............................................................................................. 9
1.6.3
AMPORPHOUS / THIN FILMS MODULES .............................................................................. 9
1.7
MODULE PERFORMANCE CHARCTERISTIC:................................................................................. 10
1.8.1.
STANDARD TEST CONDITIONS (STC): .................................................................................. 10
1.8.3.
OPEN CIRCUIT VOLTAGE VOC ............................................................................................. 10
1.8.4.
SHORT CIRCUIT CURRENT ISC ............................................................................................. 11
1.8.5.
RATED PEAK POWER PMAXX .............................................................................................. 11
1.8.6.
MAXIMUM POWER VOLTAGE OR MAXIMUM POWER POINT VOLTAGE (VPM): ............... 11
1.8.7.
MAXIMUM POWER CURRENT OR MAXIMUM POWER POINT CURRENT (IPM): ................ 11
1.8.8.
FILL FACTOR ........................................................................................................................ 11
1.8.9.
OPTIMAL RESISTANCE ......................................................................................................... 12
1.8.10.
EFFICIENCY .......................................................................................................................... 12
1.8.11.
NOMINAL MODULE EFFICIENCY: ........................................................................................ 12
1.8.12.
RELATIVE MODULE EFFICIENCY: ......................................................................................... 12
Chapter 2: SOLAR POWER SYSTEM COMPONENTS: ................................................................................... 13
2.1.
COMPONENTS: ............................................................................................................................ 13
2.2.
SOLAR ENERGY FLOW: ................................................................................................................ 13
Chapter 3: THE CHARGE CONTROLLERS...................................................................................................... 14
3.1.
CHARGE CONTROLLER: ............................................................................................................... 14
3.2.
REQUIREMENT OF A CHARGE CONTROLLER WITH A SOLAR PANEL:.......................................... 14
3.3.
MAXIMUM POWER POINT TRACKING (MPPT): .......................................................................... 14
2
3.4
TYPES OF CHARGE CONTROLLERS ............................................................................................... 15
3.4.1.
FABRICATION BASED: .......................................................................................................... 15
3.4.2.
OPERATION BASED TYPES ................................................................................................... 15
3.5.
ADDITIONAL FEATURES:.............................................................................................................. 15
Chapter 4: INVERTERS: ................................................................................................................................ 17
4.1 SOLAR INVERTERS: ............................................................................................................................ 17
4.2 WORKING PRINCIPLE: ....................................................................................................................... 17
4.3 TYPES OF INVERTERS:........................................................................................................................ 17
4.3.1..................................................................................................................................................... 17
4.3.3
Battery backup/Hybrid inverters ........................................................................................ 18
Chapter 5: SOLAR BATTARIES ..................................................................................................................... 19
5.1
DEEP-CYCLE BATTERIES: .............................................................................................................. 19
5.2 TYPES OF BATTARIES: ....................................................................................................................... 19
5.2.1 RV or Marine type battaries:...................................................................................................... 19
5.2.2 Standard Flooded Deep Cycle Battery: ...................................................................................... 19
5.2.3 Gel Batteries:............................................................................................................................. 20
5.2.4 Absorbed Glass Mat (AVG) batteries : ..................................................................................... 20
5.3 SELECTING BATTERY SIZE. ................................................................................................................ 20
5.4 BATTERY WIRING SCHEMETICS: ....................................................................................................... 20
5.4.1 Parallel connection:................................................................................................................... 20
5.4.2 Series Connection: ..................................................................................................................... 21
5.4.4 Series – Parallel connections:.................................................................................................... 21
Chapter 6: SOLAR CABLES: .......................................................................................................................... 22
6.1 CABLE SIZING:.................................................................................................................................... 22
6.2 SIGNIFICANCE OF CABLE SIZING....................................................................................................... 22
6.3 WIRE TYPES: ..................................................................................................................................... 22
6.4 FUNDAMENTAL CONCIDERATION:................................................................................................... 22
6.4.1 Cable Size: .................................................................................................................................. 22
6.4.2 Current Rating: ........................................................................................................................... 22
6.4.2 Voltage Output:.......................................................................................................................... 23
6.4.3 Distance:..................................................................................................................................... 23
6.5 CALCULATING THE WIRE SPECIFICATION: ........................................................................................ 23
3
6.5.1 Interpreting the cable sizing: ..................................................................................................... 23
Chapter 7: SOLAR ENERGY SYSTEM SIZING................................................................................................. 24
7.1 DETERMINE POWER CONSUMPTION DEMANDS .............................................................................. 24
7.2 SIZE THE PHOTOVOLTIC MODULES ................................................................................................... 24
7.2.1 Calculate the total Watt-peak rating needed for PV modules:.................................................. 24
7.3 INVERTER SIZING ............................................................................................................................... 25
7.4 BATTERY SIZING ................................................................................................................................ 25
7.5
SOLAR CHARGE CONTROLLER SIZING ......................................................................................... 26
Chapter 8 :BENEFITS OF INSTALLING AN ALTERNATIVE SOLAR ENGERY SYSTEM: ..................................... 27
4
ABSTRACT:
The solar cells are the electrical devices that convert the energy device that converts the energy
of light directly into electricity by the photovoltaic effect. It is a form of photoelectric cell which, when
exposed to light, can generate and support an electric current without being attached to any external
voltage source. These solar cells are then connected, packed and assemble to make solar cells /
photovoltaic module. Solar panels are then fabricated by the series electrical connection of photovoltaic
modules. The solar power system is composed of solar panels which produce DC electricity, batteries to
store that electricity, controller which controls the voltage been supplied to the battery. Inverter employed
to convert DC to AC which is provided to the load, and power cables through which power is transmitted.
5
Chapter 1 : THE PHOTOVOVTIC THEORY:
2
Silicon is fundamentally a non-conductor
unless it’s doped by impurities, i.e. adding
element from group 3 or 5 having either 3
or 5 electrons in valance shell. So now
the element having 5 electrons will let its
4 electrons to create bond while the 5th
one will be a free electron making an Ntype semiconductor, similarly a hole is
created when 3rd group element is doped
producing a P-type
1
3
;2
These two when combined, due to
the combination of electron-hole
pair at junction of electron hole pair
at the junction, an interior electric
field built-up, which acts as diode.
Almost 95% of Photovoltaic cells
.
are made of materials called
semiconductors such as silicon, the
second most abundant element on
earth, the outermost shell of silicon
has 4 valance electrons, which
pairs up with another Silicon atom
to gain stability.
THE PHOTOVOLTIC
THEORY
4
When light, in the form of photons, hits
our solar cell, its energy breaks apart
electron-hole pairs, consequentially
producing free electrons and holes.
These electrons then flow in external
circuits to produce electric current,
6
electric field causes a voltage which
imparts power, the product of the two.
1.1 BASIC PHENOMINA:
Photovoltaic’s (PV) is a method
of generating
electrical
power by
converting solar
radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect.
Photovoltaic power generation employs solar panels composed of a number of solar
cells containing a photovoltaic material.
1.1 MATERIALS EMPOLOYED:
Materials presently used for photovoltaic’s include monocrystalline silicon, polycrystalline
silicon, amorphous silicon, cadmium telluride, and copper indium gallium selenide/sulfide.
1.2 CORE OPERATIONS:
The operation of a photovoltaic (PV) cell requires 3 basic attributes:
1. The absorption of light, generating either electron-hole pairs.
2. The separation of charge carriers of opposite types.
3.
The separate extraction of those carriers to an external circuit.
1.3 SOLAR CELL:
Solar cells are the basic building block of solar panels. Solar cells are often electrically
connected and encapsulated as a module. Photovoltaic modules often have a sheet of glass on the
front side, allowing light to pass while protecting the semiconductor wafers from abrasion and
impact due to wind-driven debris, rain, hail, etc. Solar cells are also usually connected in series in
modules, creating an additive voltage.
1.4 THE CONVENTIONAL SOLAR CELLS STRUCTURE
The silicon solar cells are consisting from:
1. Front silver grid;
2. Antireflection coating (ARC);
3. Emitter
region
of
semiconductor
(n-type);
р-n junction which is situated between p and n
regions.
4. Base region of semiconductor (p-type);
Figure 1: Solar Cell Internal Structure
7
5. Back surface field (BSF);
6. Aluminum rear contact ;
7. Rear silver – aluminum contact.
1.5 SOLAR PANEL:
Assemblies of photovoltaic cells are used to make solar modules which generate electrical power
from sunlight. Multiple cells in an integrated group, all oriented
in one plane, constitute a solar photovoltaic panel .The
electrical energy generated from solar modules is referred to
as solar power. Electrical connections are made in series to
achieve a desired output voltage and/or in parallel to provide a
desired current capability. The conducting wires that take the
current off the modules may contain silver, copper or other non-
Figure 2: Solar panel
magnetic conductive transition metals.
1.6 TYPES OF SOLAR PANAL:
Solar panels generally are of 3 types owing to the silicone allotrope being employed in its
fabrication.
1.6.1
POLYCRYSTALLINE MODULES
Polycrystalline or multicrystalline modules are composed of a
number of different crystals, fused together to make a single cell
.They have long been the most popular type of solar module,
due to the lower cost in manufacturing the cells.
As shown in the figure 3, the construction of these different
crystals gives the solar panel a visible crystal grain. They are
Figure 3:Polycrystalline Modules
slightly cheaper to produce than Mono panels, but are also less
efficient. This is because the crystal grain boundaries can trap electrons, which results in lower
efficiency.
8
Table 1: Merits and Demerits of Polycrystalline Modules
Cost effective to manufacture
Not as efficient as mono
Good efficiency
Has more silicon - high embodied energy
Commonly available - easy to replace
Takes up small area on roof
1.6.2 MONOCRYSTALLINE MODULES
Monocrystalline is constructed using one single crystal, cut from
ingots. This diamond shaped modules gives the solar panel a uniform
appearance across the entire module. They are still more expensive
than polycrystalline, but can be up to 2% more efficient.
Figure 4: Monocrystalline Module
Table 2:Merits and Demerits of Monocrystalline Modules
Most efficient module available
More expensive to produce
Most popular technology on market
Has more silicon - high embodied energy
Commonly available - easy to replace
Takes up small area on roof
1.6.3
AMPORPHOUS / THIN FILMS MODULES
The manufacture of these panels is highly automated - silicon is
sprayed onto the substrate as a gas called vapour deposition which
means that the silicon wafer is approx 1 micron thick as compared to
approx 200 microns for mono and poly. This means that the panel
uses less energy to produce therefore will pay itself back from an
energy point of view in a shorter time. However, it also means that
9
Figure 5 : Thin Film Modules
the panels are far less efficient than mono or poly about 5-6% efficiency.
Table 3: Merits and Demerits of Thin Film Modules
Partially shade tolerant
Poor efficiency (6%)
More effective in hotter climate
Takes up more space for same output
Uses less silicon - low embodied energy
New technology - less proven reliability
No aluminum frame - low embodied energy
Less popular - harder to replace
1.7 MODULE PERFORMANCE CHARCTERISTIC:
1.8.1. STANDARD TEST CONDITIONS (STC): Module performance is generally rated
under standard test conditions (STC) which are; irradiance of 1,000 W/m²,
solar spectrum of AM 1.5 and module temperature at 25°C.
1.8.2. NOMINAL VOLTAGE: refers to the voltage of the battery that the module is best
suited to charge. The actual voltage output of the module changes as lighting,
temperature and load conditions
change, so there is never one
specific voltage at which the
module operates. Nominal voltage
allows users, at a glance, to make
sure the module is compatible
with a given system.
1.8.3. OPEN CIRCUIT VOLTAGE VOC is
the maximum voltage that the module
Figure 6: V-I Charachteristics for Solar Cell
can produce when not connected to an electrical circuit or system. VOC can be
measured with a meter directly on an illuminated module's terminals or on its
disconnected cable.
10
1.8.4. SHORT CIRCUIT CURRENT ISC : is the maximum current that flows when the
panel voltage is zero i.e. zero load resistance.
1.8.5. RATED PEAK POWER PMAXX: is the maximum output under standard test
conditions, at the knee of the V-I curve shown. This is the maximum power a solar
panel can produce
1.8.6. MAXIMUM POWER VOLTAGE OR MAXIMUM POWER POINT VOLTAGE (VPM):
The voltage at which maximum power is produced by a solar panel, i.e. at the knee
of V-I graph.
1.8.7. MAXIMUM POWER CURRENT OR MAXIMUM POWER POINT CURRENT (IPM):
The current at which the maximum power is produced.
1.8.8. FILL FACTOR: it is defined as the ratio of the actual maximum obtainable power to
the product of the open circuit voltage and short circuit current.
This is a key parameter in evaluating the performance of solar cells. Typical commercial
solar cells have a fill factor > 0.70. Grade B cells have a fill factor usually between 0.4 to
0.7. Cells with a high fill factor have a low equivalent series resistance and a
high equivalent shunt resistance, so less of the current produced by the cell is dissipated
in internal losses.
11
1.8.9. OPTIMAL RESISTANCE: The optimal resistance is the ratio of voltage to current
determined from the maximum power point. At this point, the load resistance is
equal to the solar panel internal resistance.
1.8.10. EFFICIENCY: The efficiency of a solar cell is the ratio of maximum electrical
power Pmax to the input power incident by light i.e.; the optical power Pin:
1.8.11. NOMINAL MODULE EFFICIENCY: This is the conversion efficiency that is
observed
when
the
module
is
subjected
to
light
with
intensity
1kW/m2 under standard conditions is called nominal efficiency. It can be obtained
from the manufacturer's data sheet.
1.8.12. RELATIVE MODULE EFFICIENCY: If the conditions differ from the standard
testing condition, the nominal module efficiency must be multiplied by relative
module efficiency, ηrel. This factor is dependent on changes in temperature, intensity
of the incoming light and ratio of diffuse radiation to direct radiation. Values for
the relative efficiency can be obtained from manufacturer's data.
12
Chapter 2: SOLAR POWER SYSTEM COMPONENTS:
2.1. COMPONENTS:
The solar power system consists of 5 main parts:

Solar panel

Charge controller

Solar batteries

Inverter

Solar cable
2.2. SOLAR ENERGY FLOW:
Figure 7: Solar Energy Components and Flow
13
Chapter 3: THE CHARGE CONTROLLERS
3.1. CHARGE CONTROLLER:
A charge controller, charge regulator or battery regulator limits
the rate at which electric current is added to or drawn from
electric batteries. It prevents overcharging against overvoltage,
which can reduce battery performance or lifespan, It may also
prevent completely draining a battery, as it perform controlled
discharges,
to
protect
Figure 8: Control Charger
battery life. Another important
functionality is that it provides central point for connecting load, panel and battery. They are
rated as the maximum current they can process from solar array.
3.2. REQUIREMENT OF A CHARGE CONTROLLER WITH A SOLAR PANEL:
Solar panels of rating 12V usually outputs a voltage of about 17-20V in considering all the
environmental factors like heavy haze, cloud cover, or high temperatures which can hinder
sunlight’s functioning. The charge controller regulates this 16 to 20 volts output of the panel
down to what the battery needs at the time. More over it also equalizes the battery, i.e., bring all
the cells in the battery at the same voltage level. Also it aids user to get the maximum power out
of the solar panel i.e.; Maximum Power Point Tracking MPPT.
3.3. MAXIMUM POWER POINT TRACKING (MPPT):
It is a technique that, solar battery chargers use to get the maximum possible power from solar
panels . It is the purpose of the MPPT system to sample the output of the cells and apply the
proper resistance to obtain maximum power for any given environmental conditions. MPPT
devices are typically integrated into an converter system that provides voltage or current
conversion, filtering, and regulation for driving various loads, including power grids, batteries, or
motors.
14
3.4 TYPES OF CHARGE CONTROLLERS:
3.4.1. FABRICATION BASED:

Stage Controllers: which rely on relays or shunt transistors to control the voltage in one
or two steps. These essentially just short or disconnect the solar panel when a certain
voltage is reached. Despite of their low cost, it is not feasible to implement for practical
purposes.

3-stage/ PWM Controllers: Instead of a steady output from the controller, it sends out a
series of pulses to the battery. The controller constantly checks the status of the battery
and determines the pulse with modulation accordingly, so if a battery is full, it will send a
pulse with short ON time, and vice versa.

Maximum power point tracking (MPPT), The Power point tracker is a high frequency
DC to DC converter. They take the DC input from the solar panels, change it to high
frequency AC, and convert it back down to a different DC voltage and current to exactly
match the panels to the batteries. MPPT's operate at very high audio frequencies, usually
in the 20-80 kHz range.
3.4.2. OPERATION BASED TYPES

Series charge controller: it disables further current flow into batteries when they are
full

Shunt charge controller: It diverts excess electricity to an auxiliary or shunt Load,
such as an electric water heater, when batteries are full.
3.5. ADDITIONAL FEATURES:
Many charge controllers also come with Low Voltage Disconnect (LVD) and Battery
Temperature compensation (BTC)
15

Low Voltage Disconnect (LVD): permits connecting load to LVD terminal which are Voltage
sensitive, i.e. if batteries voltage drops too far the load disconnects, thereby preventing
damage to both battery and load

Battery Temperature compensation (BTC):
it adjusts the charge rated based on the
temperature of the battery since they are sensitive to temperature variation below about 75F.
16
Chapter 4: INVERTERS:
An inverter is an electrical power converter that changes direct current (DC) to alternating current (AC).
4.1 SOLAR INVERTERS:
A solar inverter, converts the variable direct current (DC) output of a photovoltaic (PV) solar panel into
a frequency alternating (AC) that can be fed into a commercial electrical grid or used by a local, offgrid electrical network.
4.2 WORKING PRINCIPLE:
In one simple inverter circuit, DC power is connected to
a transformer through the center tap of the primary winding. A
switch is rapidly switched back and forth to allow current to
flow back to the DC source following two alternate paths
through one end of the primary winding and then the other.
The alternation of the direction of current in the primary
Figure 9: Inverter's Working Principle
winding of the transformer produces alternating current (AC)
in the secondary circuit.
4.3 TYPES OF INVERTERS:
4.3.1. Stand-alone/Off Grid inverters: used in isolated
systems where the inverter draws its DC energy from
batteries charged by photovoltaic arrays totally
disconnecting from the electric utility company. They
can also be used for providing emergency backup
power in case of load shedding, to homes or industries
that currently use the power from an electric company.
Inverters with the built-in AC charger option are
particularly well suited to providing seamless backup
Figure 10 : Stand Alone Inverters
power. The off grid inverter is a three-in-one system
integrating the controlling of battery charging/discharging, inverting and load dumping.
17
4.3.2 Grid-tie/On Grid inverters, Inverters which are connected to electric supply company and do
not use a battery bank. They match phase with a utility-supplied sine wave and pull
electricity from the grid when needed, then push the
excess electricity back into the grid when the local
customer isn't using the full capacity being generated
by Solar panels .It reduces or even eliminates the
customer's electric bills while providing appropriate
energy. 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 failure.
4.3.3
Figure 11 :On Grid Inverters
Battery backup/Hybrid inverters: 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 primarily used for grid-tie
purposes but also have the added feature that they provide backup
power to your home / office when the electric utility fails.
Hybrid inverters mostly have two modes

Figure 12 : Hybrid Inverters
Load Shedding mode:
The load normally connected to grid and solar charges the batteries. In case of load
shedding, the load is automatically switched to solar.

Energy saving mode :
The system sense and cutoff the load from grid and connect it to solar as soon as it is
available also observing the battery level. If battery levels drop below 60%, the load
again gets connected to grid and solar starts charging the battery. When battery is charged
to 80% it again supplies power to load.
18
Chapter 5: SOLAR BATTARIES
Solar batteries are an essential part of photovoltaic system, as it stores the power been generated
by the panel. Solar panels only outputs power when the sun shines is shining, but the electricity
is needed when there is no sun ,hence batteries are connected in series or parallel depending
upon current/ voltage requirement to provides the necessary backup time when there is no
sunlight or for the on-grid system when the external power cease. The batteries mostly used are
the deep discharge batteries.
5.1 DEEP-CYCLE BATTERIES:
A deep-cycle battery is a lead-acid battery designed to be regularly deeply discharged using most
of its capacity. They are so designed that they can be charged and discharge hundreds or
thousands of time. A deep-cycle battery is designed to discharge between 50% and 80% of its
capacity. Although these batteries can be cycled down to a 20% charge, the best lifespan it is
advisable to keep the average cycle at about 50% discharge. These batteries are rated in AmpsHours (ah), that the amount of current in amps that can be continuously provided for an hour.
5.2 TYPES OF BATTARIES:
5.2.1 RV or Marine type batteries:
RV or Marine type deep cycle batteries are basically for boats & campers and are suitable for
only very small systems. They can be used but do not really have the capacity for continuous
service with many charge/discharge cycles for many years. They are more expensive than deep
cycle recreational batteries but are the least expensive choice for a small system on a budget.
5.2.2 Standard Flooded Deep Cycle Battery:
These are Lead acid batteries that have caps to add water. Many manufacturers make these types
for Solar Energy use. They are reasonably priced and work well for many years. All flooded
batteries release gas when charged and should not be used indoors. If installed in an enclosure, a
venting system should be used to vent out the gases which can be explosive.
19
5.2.3 Gel Batteries:
These are the sealed batteries have gel type semi liquid electrolyte inside the battery these are
generally maintenance-free gel cell batteries, require no venting as no gas is produced during
charging process, so they can be placed indoor. This makes them more reliable and long living as
batteries perform better in a constant temperature. These batteries typically cost more.
5.2.4 Absorbed Glass Mat (AVG) batteries:
Absorbed Glass Mat batteries are the best available for Solar Power use. A woven glass mat is
used between the plates to hold the electrolyte. They are leak/spill proof, do not out gas when
charging, and have superior performance. They have all the advantages of the sealed gel types
and are higher quality, maintain voltage better, self discharge slower, and last longer. They are
more expensive, yet efficient.
5.3 SELECTING BATTERY SIZE.
All of following factors should be looked at, and one requiring the largest capacity will dictate
battery size:

Required storage capacity

Maximum charge/discharge rate

Minimum temperature at which they used
5.4 BATTERY WIRING SCHEMETICS:
3 schemes have been used to wire batteries to gain desreable output:
5.4.1 Parallel Connection:
For higher current requirement parralel connections
are used, in which all the positive terminals of a group
of battaries are connected and seperately, all the
negetive terminals are connected. The volatge of all
the batteries remains as of single battary but the
amp/hours rating equal to the sum of individual ones.
This is commonly used with 12V battery-Inverter
system.
Figure 13 : Parallel Connections
20
5.4.2 Series Connection:
In these batteries are connected to positive
terminal of one to the negative of next , to gain
large voltage i.e. sum of voltage of all the batteries
whereas battery bank has a same currrent ratting as
of single battaey.generally is used in 24V battaryInverter system.
Figure 14 : Series Connection
5.4.4 Series – Parallel connections:
This is the combination of both the techniques ,
which is done often to get a higher current and
voltage battery bank out of several small low
voltage battaries.
Figure 15 : Series- Prarllel Connections
21
Chapter 6: SOLAR CABLES:
Solar
cable is
the
in photovoltaic power
interconnection
generation.
A
cable
used
solar
cable
interconnects solar panels and other electrical components
in the photovoltaic system. Solar cables are designed to
be UV resistant and weather resistant. It can be used within
Figure 16 : Solar Cables
a large temperature range and are generally laid outside.
6.1 CABLE SIZING:
Cable sizing is the process of selecting appropriate sizes for electrical power cable conductors
typically described in terms of cross-sectional area, American Wire Gauge (AWG), and depends
mainly upon the maximum output power and distance of the source from the device.
6.2 SIGNIFICANCE OF CABLE SIZING
The proper sizing of cables is important to ensure that the cable can:

Operate continuously under full load without being damaged

Provide the load with a suitable voltage and avoid excessive voltage drops

Withstand the worst short circuits currents flowing through the cable
6.3 WIRE TYPES:

single stranded conductor

multi stranded conductor
6.4 FUNDAMENTAL CONCIDERATION:
6.4.1 Cable Size:
Cable size is measured in gauge or referred to as AWG (American Wire Gauge).Increasing
gauge numbers, bigger gauge numbers; indicate decreasing, smaller, wire diameters
6.4.2 Current Rating:
Wire is rated according to amps, the number of amps that can safely pass along it. The higher the
current (amps), the thicker the wire, the lower the gauge.
22
6.4.2 Voltage Output:
The output voltage required is considered while selecting a desired cable.
6.4.3 Distance:
Distance from the solar panel to the battery should be consider as increased distance will impart
a great Voltage Drop, as a consequence of which current get increased as they inversely related
by ohms law. Increased distance requires increasingly heavier wiring.
6.5 CALCULATING THE WIRE SPECIFICATION:
Cable Sizing Charts are used as reference for
selecting a cable precisely. We select a cable of
appropriate gauge while already knowing the
output required voltage, current and distance
from the panel to battery.
6.5.1 Interpreting the cable sizing:
A typical wire sizing chart is shown in fig, it’s
for the 12V output with 5% losses, the top most
row for the wire gauge and left most column for
the current in amps, the numbers in between
shows the distance in feet. So for example, for a
12V, 10A system at a distance of 40’, we will
select a cable of #8.
23
Figure 17 :Cable Sizing Chart
Chapter 7: SOLAR ENERGY SYSTEM SIZING
7.1 DETERMINE POWER CONSUMPTION DEMANDS
The foremost step in designing a solar energy system is to find out the total power and energy
consumption of all loads that need to be supplied by the solar system, it requires two basic
calculations.
7.1.1 Calculate total Watt-hours per day for each appliance used: Add the Watt-hours
needed for all appliances together to get the total Watt-hours per day which must be delivered to
the appliances.
7.1.2 Calculate total Watt-hours per day needed from the PV modules: Multiply the total
appliances Watt-hours per day times 1.3 i.e. The energy lost in the system get the total Watthours per day which must be provided by the panels.
7.2 SIZE THE PHOTOVOLTIC MODULES
Different size of PV modules will produce different amount of power. To find out the sizing
of PV module, the total peak watt produced needs. The peak watt (Wp) produced depends on
size of the PV module and climate of site location. We have to consider “panel generation
factor” which is different in each site location. , the panel generation factor used in Tesla is is
4.5. To determine the sizing of PV modules, calculate as follows:
7.2.1 Calculate the total Watt-peak rating needed for PV modules: Divide the total Watt-hours
per day needed from the PV modules by 4.5 to get the total Watt-peak rating needed for the PV
panels needed to operate the appliances.
7.2.2 Calculate the number of PV panels for the system: Divide the answer obtained by the
rated output Watt-peak of the PV modules available to you. Increase any fractional part of result
to the next highest full number and that will be the number of PV modules required.
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Result of the calculation is the minimum number of PV panels. If more PV modules are installed,
the system will perform better and battery life will be improved. If fewer PV modules are used,
the system may not work at all during cloudy periods and battery life will be shortened.
7.3 INVERTER SIZING
An inverter is used in the system where AC power output is needed. The input rating of the
inverter should never be lower than the total watt of appliances. The inverter must have the same
nominal voltage as your battery.
For stand-alone systems, the inverter must be large enough to handle the total amount of
Watts you will be using at one time. The inverter size should be 25-30% bigger than total Watts
of appliances. In case of appliance type is motor or compressor then inverter size should be
minimum 3 times the capacity of those appliances and must be added to the inverter capacity to
handle surge current during starting.
For grid tie systems or grid connected systems, the input rating of the inverter should be same
as PV array rating to allow for safe and efficient operation.
7.4 BATTERY SIZING
The battery type recommended for using in solar PV system is deep cycle battery. Deep cycle
battery is specifically designed for to be discharged to low energy level and rapid recharged or
cycle charged and discharged day after day for years. The battery should be large enough to store
sufficient energy to operate the appliances at night and cloudy days. To find out the size of
battery, calculate as follows:
Calculate total Watt-hours per day used by appliances.
Divide the total Watt-hours per day used by 0.85 for battery loss.
Divide the answer obtained in item 4.2 by 0.6 for depth of discharge.
Divide the answer obtained in item 4.3 by the nominal battery voltage.
Multiply the answer obtained in item 4.4 with days of autonomy (the number of days the
system will operate when there is no power produced by PV panels) to get the required Amperehour capacity of deep-cycle battery.
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Battery Capacity (Ah) = Total Watt-hours per day used by appliances x Days of autonomy
(0.85 x 0.6 x nominal battery voltage)
7.5 SOLAR CHARGE CONTROLLER SIZING
The solar charge controller is typically rated against Amperage and Voltage capacities. Select
the solar charge controller to match the voltage of PV array and batteries and then identify which
type of solar charge controller is right for your application. Make sure that solar charge controller
has enough capacity to handle the current from PV array.
For the series charge controller type, the sizing of controller depends on the total PV input
current which is delivered to the controller and also depends on PV panel configuration i.e.series
or parallel configuration.
According to standard practice, the sizing of solar charge controller is to take the short circuit
current (Isc) of the PV array, and multiply it by 1.3
Solar charge controller rating = Total short circuit current of PV array x 1.3
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Chapter 8: BENEFITS OF INSTALLING AN ALTERNATIVE SOLAR ENGERY
SYSTEM:
1. It significantly reduces the cost of bringing power to a remote site, when compared to
what the utility company will charge.
2. No ongoing monthly bill from the utility company.
3. Pollution free power from a solar generating system that is free of surges, spikes,
brownouts and blackouts that can damage or shorten the life of appliances.
4. It reduces power poles that spoil the natural environment, thus enhancing the beauty and
resale value of your property.
5. Solar power is a renewable and natural resource.
6. Solar power is non-polluting. Unlike oil, solar power does not emit greenhouse gases or
carcinogens into the air.
7. Solar cells require little maintenance.
8. Solar cells can last a lifetime.
9. Solar power is silent.
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