Understanding Solar Energy

Solar Engineering
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preparation by s.r.kushero
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a centre for application of renewable energy preparation by s.r.kushero email : Care.@care-india.com http://www.care-india.com

Solar Engineering
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Solar power might be a solution
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Solar Engineering BASIC

How much sunshine will I need? How many solar panels you will need based on the
amount of sunshine available daily in your area

Using solar power to produce electricity is not the same
as using solar t produce h t S l th
i l to d heat. Solar thermal principles
l i i l It is presumed that at "peak sun", 1000 W/m² of power
peak sun W/m
reaches the surface of the earth.
are applied to produce hot fluids or air.
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One hour of full sun provides 1000 Wh per m² = 1
Photovoltaic principles are used to produce electricity. A
kWh/m² -representing the solar energy received in one
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solar panel (PV panel) is made of the natural element
element,
silicon, which becomes charged electrically when hour on a cloudless summer day on a one-square meter
subjected to sun light. surface directed towards the sun.

Solar panels are directed at solar south in the northern To put this in some other perspective, the Indian
p
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hemisphere and solar north in the southern hemisphere Department of E
D t t f Energy i di t
indicates th amount of solar
the t f l
(these are slightly different than magnetic compass energy that hits the surface of the earth every +/- hour is
greater than the total amount of energy that the entire
north-south directions) at an angle dictated by the
geographic location and latitude of where they are to be human population requires in a year. Another
perspective is that roughly 100 miles square of solar
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installed.
installed
panels placed in the southwestern U.S. could power the

WHOLE United States .
Typically, the angle of the solar array is set within a
range of between site-latitude-plus 15 degrees and site-
The intensity of the Sun's radiation changes with the
latitude-minus 15 degrees, depending on whether a
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hour of th d
h f the day, ti
time of th year and weather conditions.
f the d th diti
slight winter or summer bias is desirable in the system.
To be able to make calculations in planning a system,
the total amount of solar radiation energy is expressed in
Many solar arrays are placed at an angle equal to the hours of full sunlight per m², or Peak Sun Hours. This
site latitude with no bias for seasonal periods. term, Peak Sun Hours, represents the average amount
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of sun available per day throughout the year.


Solar Engineering Solar Radiation In India
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Solar Radiation : Sunshine across INDIA
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A color coded map of INDIA that displays the

daily average hours of solar radiation
(sunshine). This information will assist you in
calculating the number of solar panels you
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will need for your solar power system. a
short explanation of Watts, Watt Hours, and
Amp Hours
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Solar Engineering BASIC

Electrical charge is consolidated in the PV panel and directed to the output terminals to produce low
voltage (Direct Current) - usually 6 to 24 volts The most common output is intended for nominal 12
volts.
volts, with an effective output usually up to 17 volts.
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A 12 volt nominal output is the reference voltage, but the operating voltage can be 17 volts or higher
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much like your car alternator charges your 12 volt battery at well over 12 volts. So there's a difference
between the reference voltage and the actual operating voltage.
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Solar Engineering
PV system

Q. What is a PV system?
A. PV technology produces electricity directly from electrons freed by the interaction of
sunlight with a solar panel made of semiconductor material. Th power provided i
li ht ith l l d f i d t t i l The id d is
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direct current (DC) electricity. The basic building block is known as a cell. Many cells
put together are known as a module, and many modules assembled together form an
array. A PV system will consist of an array of modules generating DC electricity, an
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inverter, and sometimes battery storage back up with charge controller.

Q. How much electricity will a system p
y y produce?
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A. The amount of power produced will depend upon how large the system is. In Mumbai
the average residential customer purchases 5,500 kilowatt-hours (kWh) per year.
There is enough sunshine falling upon on the average home to produce this and a
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system can be designed to offset all electrical needs. The cost to accomplish a 100%
ff %

system may be prohibitive and sometimes it makes more sense to simply reduce or
'shave' your consumption. Some utilities use tiered rates when they charge for
consumption which means that the more energy you use the higher is the cost per
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kilo-watt-hour. The most economically feasible size is usually between 50% and 75%
of your annual household needs.
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Solar Engineering FREE electricity

At today's prices a single solar panel, rated at 1 Watts sells for about Rs.150-
Rs.250 depending on brand.

If your system uses several of these panels, this would seem to be quite
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expensive.
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The good news is that today's solar panels have a life expectancy of 25 to 30
today s
years or more. And just think, they'll be making FREE electricity that whole time!
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Solar Engineering Manual

The Basics f Solar Power f P d i
Th B i of S l P for Producing El t i it
Electricity

Understanding Parts of a Solar Energy System Overview of the individual components required
to assemble a solar power system and produce free electricity from the sun for energy
p y p y gy
independence.
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1.Solar Panels which generate the electricity,
2.Charge Controller to control battery charging,
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3.the Power Inverter that makes 220 volts AC from the batteries to run your appliances,
4.Storage batteries which store the excess power for use when the sun is weak or not available,
5. AC generators for back-up power.
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Solar Engineering System Overview

For electricity from the sun. You will need one or more
Solar Panels a Charger Controller a Power Inverter
Panels, Controller, Inverter,
and of course, Batteries.
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The first component needed is one or more Solar Panels.
They supply the electricity and charge the batteries. A
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very small system could get away with a couple 80 watt
panels but figure at least 4 to 8 for a small to medium
system..
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A Charge Controller. is needed to prevent overcharging
of the batteries. Proper charging will prevent damage
and increase the life and performance of the batteries.
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The Power Inverter is the heart of the system It makes
system.
220 volts AC from the 12 volts DC stored in the batteries.

It can also charge the batteries if connected to a
generator or the AC line.
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Last are the storage Batteries. They store the electrical
power in the form of a chemical reaction. Without storage
you would only have power when the sun was shining or
the generator was running.
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Solar Engineering Solar Power : Components

A Solar Power energy system can be used by anyone to Charge Controllers
supply all their electrical needs, provide back-up power, This device is necessary to protect the batteries from over
or even just as a supplement to the normal electrical grid charging and supply them with the proper amount of
connection to a utility company. It is ideal for remote energy to promote long battery life.
locations where power is unavailable or too expensive to
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hook-up to. Power Inverters
The power inverter converts your storage battery power
Solar Panels into the 220 volts AC that runs your appliances. It is the
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The S Solar Panels tutorial will give you a simple heart of your solar energy system Unless you only run 12
system.
explanation of this most basic electric power generator volt DC appliances you will need a power inverter to supply
for solar energy systems. Fixed, Adjustable, and your AC.
Tracking type mounting systems are also covered.
Getting power from the sun's energy is not only Free, but
gp gy y , Storage Batteries
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it's Fun to setup a solar energy system and be your own Without Storage Batteries to store energy you would only
utility company have power when the sun was shining or the generator as
running. Here we discuss 4 major categories of batteries
for solar power systems. The batteries in your system are
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very important. The care & feeding section of this tutorial is
a must read to ensure long battery life and good

performance.

AC Generators
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Even the largest Solar Energy System would not have
enough power for many consecutive days of no sun. The
AC Generator tutorial will tell you what size generator you'll
need
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Solar Engineering
Solar Panels

Solar panels generate free power from the sun by converting sunlight to electricity with no moving
parts, zero emissions, and no maintenance. The solar panel, the first component of a electric solar
e e gy sys e , s co ec o o
energy system, is a collection of individual silicon cells that generate electricity from sunlight. The
d dua s co ce s a ge e a e e ec c y o su g e
photons (light particles) produce an electrical current as they strike the surface of the thin silicon
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wafers.
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A single solar cell produces only about 1/2 ( 5) of a volt However a typical 12 volt panel about 25
(.5) volt. However,
inches by 54 inches will contain 36 cells wired in series to produce about 17 volts peak output.

If the solar panel can be configured for 24 volt output, there will be 72 cells so the two 12 volt groups
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of 36 each can be wired in series, usually with a jumper, allowing the solar panel to output 24 volts.
When under load (charging batteries for example), this voltage drops to 12 to 14 volts (for a 12 volt
configuration) resulting in 75 to 100 watts for a panel of this size.
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Multiple solar panels can be wired in parallel to increase current capacity (more power) and wired in

series to increase voltage for 24, 48, or even higher voltage systems. The advantage of using a higher
voltage output at the solar panels is that smaller wire sizes can be used to transfer the electric power
from the solar panel array to the charge controller & batteries Since copper has gone up considerably
batteries.
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in the last few years, purchasing large copper wiring and cables is quite expensive. (that's why
pennies are made of mostly zinc today).
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Solar Engineering Solar Panels

An
A eco-friendly electric generator. S l
f i dl l ti t Solar panelsl
generate free power from the sun by converting
sunlight to electricity with no moving parts, zero
emissions, and no maintenance. The solar panel,
the first component of a electric solar energy
system, is a collection of individual silicon cells that
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generate electricity from sunlight.
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The photons (light particles) produce an electrical
current as they strike the surface of the thin silicon
wafers. A single solar cell produces only about 1/2
(.5) of a volt.
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However, a typical 12 volt panel about 25 inches by
54 inches will contain 36 cells wired in series to Multiple solar panels can be wired in parallel to
produce about 17 volts peak output. increase current capacity (more power) and wired
in series to increase voltage for 24, 48, or even
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higher lt
hi h voltage systems.
t
If the solar panel can be configured for 24 volt

The advantage of using a higher voltage output at
output, there will be 72 cells so the two 12 volt the solar panels is that smaller wire sizes can be
groups of 36 each can be wired in series, usually used to transfer the electric power from the solar
with a jumper allowing the solar panel to output 24
jumper,
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panel array to the charge controller & batteries
batteries.
volts. When under load (charging batteries for Since copper has gone up considerably in the last
example), this voltage drops to 12 to 14 volts (for a few years, purchasing large copper wiring and
12 volt configuration) resulting in 75 to 100 watts for cables is quite expensive. (that's why pennies are
a panel of this size. made of mostly zinc
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Solar Engineering Solar Panels : TYPES

Amorphous solar panels : These are not really
Monocrystalline solar panels : The most
crystals, but a thin layer of silicon deposited on a
efficient and expensive solar panels are base material such as metal or glass to create
made with Monocrystalline cells These
cells. the solar panel. These Amorphous solar panels
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solar cells use very pure silicon and are much cheaper, but their energy efficiency is
involve a complicated crystal growth also much less so more square footage is
process. Long silicon rods are produced
g required to produce the same amount of power
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which are cut into slices of .2 to .4 mm as the Monocrystalline or Polycrystalline type of
solar panel. Amorphous solar panels can even
thick discs or wafers which are then
be made into long sheets of roofing material to
processed into individual cells that are cover large areas of a south facing roof surface.
wired together in the solar panel
panel.
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Polycrystalline solar panels : Often called
Multi-crystalline, solar panels made with
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Polycrystalline cells are a little less expensive &

slightly less efficient than Monocrystalline cells
because the cells are not grown in single crystals
but in a large block of many crystals. This is what
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gives them that striking shattered glass
appearance. Like Monocrystalline cells, they are
also then sliced into wafers to produce the
individual cells that make up the solar panel.
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Solar Engineering Solar Panels : Wattage

The output of a solar panel is usually stated Since the intensity of sunlight contacting
in watts, and the wattage is determined by the solar panel varies throughout the day,
multiplying the rated voltage by the rated
u p y g e a ed o age e a ed we use the term "peak sun hours“ as a
e e e pea su ou s
amperage. method to smooth out the variations into a
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daily average
The formula for wattage is VOLTS times
Early morning and late-in-the-day sunlight
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AMPS equals WATTS
WATTS.
produces less power than the mid-day sun.

So for example, a 12 volt 60 watt solar panel Naturally, cloudy days will produce less
measuring about 20 X 44 inches has a rated p
power than bright sunny days as well.
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voltage of 17.1 and a rated 3.5 amperage.
When planning a system your
VxA=W geographical area is rated in average peak
sun hours per day based on yearly sun
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17.1
17 1 volts times 3 5 amps equals 60 watts
3.5
data.

If an average of 6 hours of peak sun per day Average peak sun hours for various
is available in an area, then the above solar g g p
geographical areas is listed in the above
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panel can produce an average 360 watt section.
hours of power per day; 60w times 6 hrs. =
360 watt-hours.
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Solar Engineering Solar Panels Wiring

Series
S i
Solar panels can be wired in series or in parallel to increase
voltage or amperage respectively, and they can be wired
both in series and in parallel to increase both volts and
amps.
amps
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Series wiring refers to connecting the positive terminal of +
one panel to the negative terminal of another. The resulting -
outer positive and negative terminals will produce voltage
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the sum of the two panels, but the amperage stays the same Parallel
as one panel. So two 12 volt/3.5 amp panels wired in series
produces 24 volts at 3.5 amps. Four of these wired in series
would produce 48 volts at 3.5 amps.
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Parallel wiring refers to connecting positive terminals to
positive terminals and negative to negative. The result is that +
voltage stays the same, but amperage becomes the sum of
-
the number of panels. So two 12 volt/3.5 amp panels wired
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in parallel would produce 12 volts at 7 amps. Four panels Series/parallel
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would produce 12 volts at 14 amps.

Series/parallel wiring refers to doing both of the above -
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increasing volts and amps t achieve th d i d voltage as
i i lt d to hi the desired lt
in 24 or 48 volt systems. The following diagram reflects this.
In addition, the four panels below can then be wired in
parallel to another four and so on to make a larger array.
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Solar Engineering Solar Installation : Location

Where a building is at a considerable distance from the public electricity supply (or grid)
- in remote or mountainous areas – PV may be the preferred possibility for generating
electricity, or PV may be used together with wind, diesel generators and/or
hydroelectric power In such off-grid circumstances batteries are usually used
power. off grid
to store the electric power.
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In locations near the grid however feeding the grid using PV panels is more practical
grid, however, practical,
and leads to optimum use of the investment in the photovoltaic system. This requires

both regulatory and commercial preparation, including net-metering and feed-in
agreements. To provide for possible power failure, some grid tied systems are set up to
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allow local use disconnected from the grid. Most photovoltaics are grid connected. In
the event the grid fails, the local system must not feed the grid to prevent the possible
creation of dangerous islanding.
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Solar Engineering Solar Panels : Placement

Shading Shadows
Sh di & Sh d Temperature & Wi d l di considerations
T t Wind loading id ti

When deciding on a location for your solar As previously discussed, you want to mount
panels, make sure no shadows will fall on the solar panels in a sunny and non-shaded location
p y
solar panel array during peak sunlight hours to get maximum sun. But, heat build-up is also a
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(say, 9am to 4pm). Not only will shading of the problem. Because the efficiency of solar panels
solar panels significantly reduce their output, but decreases as temperature increases, the solar
also could cause damage. Some solar panel p
panel mounting system should allow for spacing
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manufacturers advertise panels that can around the individual solar panels for air
withstand shading but they use internal diodes circulation. The idea is to allow air cooling in the
which in themselves reduce the power hot sun to reduce the temperature of the solar
somewhat. I recommend simply choosing a good p
panels. Another consideration is wind loading. By
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location to start with, even if it means cutting allowing air to flow around the solar panels, not
down a few trees or otherwise removing only will they remain cooler,
obstacles.
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Solar Engineering Efficiency Losses

In all systems there are losses due to such things as voltage losses as the electricity is
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carried across the wires, batteries and inverters not being 100 percent efficient, and other
factors. These efficiency losses vary from component to component, and from system to
system and can be as high as 25 percent.
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Solar Engineering Solar Panels : Mountings

Types of Solar Panel Array Mountings

: Fixed, Adjustable, & Tracking Fixed solar panel
mounts : If you use th most simple and l
t the t i l d least expensive
t i
type of solar panel mounting system, it will be completely
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stationary. The solar panels should always face the
equator. (due south in the northern hemisphere). Don't
forget that true south varies from magnetic south. This
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can make a huge difference. For example, true south in
eastern Washington state is 161 on a compass instead
of 180. The angle of inclination (tilt) in degrees should be
set to about your latitude. Slightly more than your latitude
will favor the winter sun and slightly less will favor the
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summer sun. (for a seasonal cabin for example).

Adjustable solar panel mounts : The angle of inclination
( )
(tilt) of an adjustable solar panel mount can be changed
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2 or more times during the year to account for the lower

angle of the sun in winter as the earth orbits the sun
causing seasonal change. A good rule of thumb is
latitude + 15 degrees in the winter and latitude – 15
degrees in the summer This will increase overall solar
summer.
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panel output by approximately 25%. I adjust my solar
panel array 4 times per year. (Shown here in its summer
position). An easy approach that works pretty good is to
set the tilt for the winter position in about mid October
and b k t summer position i mid.
d back to iti in id
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Solar Engineering Charge Controller

A charge controller monitors the battery's state
battery s state- Many charge controllers also offer Low Voltage
of-charge to insure that when the battery needs Disconnect (LVD) and Battery Temperature
charge-current it gets it, and also insures the Compensation (BTC) as an optional feature. The
battery isn't over-charged. Connecting a solar LVD feature permits connecting loads to the LVD
panel to a battery without a regulator seriously terminals which are then voltage sensitive. If the
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risks damaging the battery and potentially battery voltage drops too far the loads are
causing a safety concern.
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disconnected - preventing
potential damage to both the battery and the
Charge controllers (or often called charge loads. BTC adjusts the charge rate based on the
regulator) are rated based on the amount of
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temperature of the battery since batteries are
amperage they can process from a solar array. If sensitive to
a controller is rated at 20 amps it means that you temperature variations above and below about
can connect up to 20 amps of solar panel output 75 F degrees.
current to this one controller. The most advanced
charge controllers utilize a charging principal
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referred to as Pulse-Width-Modulation (PWM) - To Load Switched
which insures the most efficient battery charging
and extends the life of the battery.
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Even more advanced controllers also include
Maximum Power Point Tracking (MPPT) which

maximizes the amount of current going into the
battery from the solar array by lowering the To Load Always On
panel's output voltage, which increases the
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charging amps to the battery - because if a panel From Solar Panel
can produce 60 watts with 17.2 volts and 3.5
amps, then if the voltage is lowered to say 14
volts then the amperage increases to 4.28 (14v
X 4.28 amps = 60 watts) resulting in a 19%
increase in charging amps for this example
example.
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Solar Engineering Connections

After you connect the Solar Panels to the input Connecting the Batteries
terminals of the Charge Controller using the
above chart, you can use the same size wire to The batteries are last. They will also require very
connect the Charge Controller output to the large cables like the large battery cables in cars.
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batteries since these wires will carry no more The full current to the loads and also the full
current than the solar panel wires and will charging current flow thru the entire battery
probably be located pretty close to the batteries bank. Connect all the batteries with large high
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anyway. quality cables. Check out the Battery Wiring
Diagrams tutorial for examples of Series and
Connecting the Power Inverter Parallel wiring techniques that allow the use of
battery voltages of 2, 4, 6, or 12 volts. Our new
The Power Inverter is next Both the Power
next.
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Battery Bank Designer tool will show you how to
Inverter and the Batteries require the largest
connect the batteries for these various voltage
wires in the system. During operation, the AC
produced by the Power Inverter draws
considerable amps from the batteries Not only
batteries.
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are very large wires required, but they should not

exceed 6 feet in length to reach the batteries.
These wires are like the large battery cables in
cars.
cars Use the largest size possible An AC
possible.
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appliance drawing 10 amps (like a microwave or
vacuum cleaner) will require 100 amps at 12
volts DC. Even large cables will get warm. Don't
skimp here
here.
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Solar Engineering Wire & Cables

To prevent dangerous overheating or inefficient Battery Wiring Diagrams
transfer of power, the wires and cables in a solar Learn how to use series and parallel wiring
power system must be correctly sized. A
convenient chart to determine wire size based on techniques to obtain exactly the power and
solar panel power output and the distance voltage you want using 2, 4, 6,or 12 volt
between the solar panels and the batteries. For batteries.
batteries Series wiring parallel wiring and
wiring,
using series/parallel combinations show you
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safety and good performance of your solar
power system you will have to use the how to build your battery bank into any
appropriate size wires when connecting the
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components of your system
system.

Meters & Monitors
This tutorial explains the importance of
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monitoring your solar energy system With the
system.
included voltage chart, you can easily determine
the basic level of charge on your batteries using
just a simple voltmeter. Taking proper care of
y
your batteries will ensure good system
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performance

Power Requirements
This tutorial is a little more advanced but
advanced,
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explains more about voltage, current, power, and
Ohm's Law. Find out about the relationship
between AC amps and DC amps. The
importance of energy conservation for a solar
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power system is also covered.


Solar Engineering Battery

During planning, all of these factors are looked at, and The Deep Cycle batteries used are designed to be
discharged and then re-charged hundreds or thousands
the one requiring the largest capacity will dictate the of times. These batteries are rated in Amp Hours (ah) -
battery size. One of the biggest mistakes made by those usually at 20 hours and 100 hours. Simply stated, amp
just starting out is not understanding the relationship hours refers to the amount of current - in amps - which
between amps and amp-hour requirements of 120 volt can be supplied by the battery over the period of hours.
AC items versus the effects on their DC low voltage
batteries. For example, say you have a 24 volt nominal
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system and an inverter powering a load of 3 amps, For example, a 350ah battery could supply 17.5
120VAC, which has a duty cycle of 4 hours per day. You continuous amps over 20 hours or 35 continuous amps
would have a 12 amp hour load (3A X 4 hrs=12 ah). for 10 hours. To quickly express the total watts
However, in order to determine the true drain on your potentially available in a 6 volt 360ah battery; 360ah
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batteries you have to divide your nominal battery voltage times the nominal 6 volts equals 2160 watts or 2 16kWh
2.16kWh
(24v) into the voltage of the load (120v), which is 5, and (kilowatt-hours).
then multiply this times your
Like solar panels, batteries are wired in series and/or
120vac amp hours (5 x 12 ah). So in this case the parallel to increase voltage to the desired level and
calculation would be 60 amp hours drained from your
p y increase amp hours.
p
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batteries - not the 12 ah. Another simple way is to take
the total watt-hours of your 120VAC device and divide The battery should have sufficient amp hour capacity to
by nominal system voltage. supply needed power during the longest expected
period "no sun" or extremely cloudy conditions. A lead-
Using the above example; 3 amps x 120 volts x 4 hours acid battery should be sized at least 20% larger than
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= 1440 watt hours divided by 24 DC volts = 60 amp
watt-hours this amount If there is a source of back up power such
amount. back-up power,
hours. Lead-acid batteries are the most common in PV as a standby generator along with a battery charger, the

systems because their initial cost is lower and because battery bank does not have to be sized for worst case
they are readily available nearly everywhere in the world. weather conditions. The size of the battery bank
There are many different sizes and designs of lead-acid required will depend on the storage capacity required,
batteries, but the most important designation is that they the maximum discharge rate, the maximum charge rate,
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are d deep cycle b tt i
l batteries. L d id b tt i
Lead-acid batteries are and th minimum t
d the i i temperature at which th b tt i will
t t hi h the batteries ill
available in both wet-cell (requires maintenance) and be used.
sealed no-maintenance versions. AGM and Gel-cell
deep-cycle batteries are also popular because they are
maintenance free and they last a lot longer.
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Solar Engineering Battery Wiring Diagrams
Wiring up your battery bank. Use 2, 4, 6, or 12
volt b tt i
lt batteries t b ild a system voltage of 12
to build t lt f 12,
24, or 48 volts using series and parallel wiring
with just 4 clicks. Battery bank capacities from
300 Amp/Hours to over 4000 Amp/Hours

•AWG (American Wire Gauge)
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Based on the distance to your solar panel array
& the amount of amperage your panels put out.
Configurations are possible for Amp/Hour
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capacities from as little as 300 Amp/Hours to
over 4000.

To use the Designer, follow these 4 simple
steps : Click 2, 4, 6, or 12 volt batteries to build
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your Battery
1.Battery Bank.
2. Select the closest Amp/Hour rating for 1
Battery.
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3.
3 Choose your System Battery Bank voltage voltage.
(your inverter input voltage)

4. Select the size of the Battery Bank capacity
in Amp/Hours.
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To determine the Amp/Hour capacity you will
need, use System Sizing Estimator which will
calculate the Amp/Hour capacity of your battery
bank and also the number of solar panels
required.
required
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Solar Engineering Battery Bank

Configurations are possible for AmpHour
capacities from as little as 300 AmpHours to over
4000.
4000 To use the Designer follow these 4 simple
Designer,
steps :
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1.Battery Bank. Batteries come in various
individual sizes. They can be connected to
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increase th system voltage.
i the t lt
2. Select the closest Amp/Hour rating for 1
battery.
To determine the total Amp/Hour capacity of
p p y
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your battery bank you must use the rating for 1
battery.
3. Choose your System Battery Bank voltage.
(your inverter input voltage) The System Voltage
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is the combined voltage of the entire battery

bank.
The Solar Panels, the Charge Controller, and the
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Inverter will all use this voltage
voltage.
4. Select the size of the Battery Bank capacity in
Amp/Hours.This is the total capacity required to
run your solar energy system.
“



Storage Batteries : the fuel tank of your solar power
Industrial strength : Flooded, Gel, and AGM sealed
system
batteries
Without batteries to store energy you would only have power when
the sun was shining or the generator was running. This tutorial The next 3 types are the heavier industrial type batteries.
describes the 4 basic types of batteries & provides some good tips They are all also considered Deep Cycle and are usually Lead
on the care & feeding of your batteries tomaximize their performance Acid types with much thicker internal plates that can withstand
and life. many deep discharge cycles. These next 3 are all designed for
RGY “ MAD EASY

alternative energy systems.
1) RV / Marine / Golf Cart : RV or Marine type deep cycle batteries 2) Flooded types : These are Lead acid batteries that have caps to add
are basically for boats & campers and are suitable for only very water. Many manufacturers make these types for Solar Energy use.
small systems. They can be used but do not really have the capacity Trojan, Surrette, and Deka are probably the most well known. They are
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for continous service with many charge/discharge cycles for many reasonably priced and work well f many years. All fl d d b tt i
bl i d d k ll for flooded batteries
years. Regular or Car type batteries should not be used at all release gas when charged and should not be used indoors. If installed
because they cannot be discharged very much without internal in an enclosure, a venting system should be used to vent out the gases
damage. A very popular battery for small systems is the Golf Cart which can be explosive.
battery.
3) Gel : Not to be confused with maintenance free batteries, sealed gel
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They are somewhat more expensive th
Th h t i than d
deep cycle recreational
l ti l batteries have no vents and will not release gas during the charging
batteries but are probably the least expensive choice for a small process like flooded batteries do. Venting is therefore not required and
system on a budget. they can be used indoors. This is a big advantage because it allows the
batteries to maintain a more constant temperature and perform better.

4) AGM : Absorbed Glass Mat batteries are in my opinion the best
) G bso bed G ass at batte es a e y op o t e
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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. The Sun Xtender
series by Concorde Battery is an excellent example of AGM batteries.
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They are more expensive, but you usually get what you pay for. You
will find this type of battery used in airplanes, hospitals, and remote
telephone/cell tower installations.
“



Care and Feeding
As a technician, I used to say that if you are not comfortable,
then neither is your equipment. I was mostly referring to
temperature and humidity In fact battery capacity ratings are
humidity.
usually specified at 77 degrees F. As batteries get colder
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their voltage drops and performance suffers.
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This is
Thi i one major reason I prefer AGM b tt i
j f batteries
because they can be stored indoors where the temperatures
vary less. Another important thing to consider is how deeply
you discharge your batteries. This is known as the DOD
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(depth of discharge). In other words, how low you let the
voltage drop before the next charge cycle. Most battery
ratings talk about 50% or so, but they will last longer if you
keep them as charged as possible. I like the 70% range.
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Lead acid batteries like to be fully charged. They will last
much longer if you do not discharge them too deeply. This is
known as shallow cycling and greatly extends their life.
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However, they can withstand discharges down to 20% or so,
but I wouldn't do it too often
“


Solar Engineering Wire & Cables

To connect the components of a Solar
Energy System, you will need to use correct
wire sizes to ensure low loss of energy and
to prevent overheating and possible damage
or even fire Below is a chart showing the
fire.
equired wire size for wire lengths to connect
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the solar panels to the Charge Controller.
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Use these numbers for a 12 volt system to
achieve a 3% or less voltage drop.

The top row represents the Wire gauge size,
the left column the number of amps the solar
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panels are rated at, and the grid cells show
the distances in feet between the Solar
Panels and the Charge Controller.
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This chart shows wire distances for a 3%

voltage drop or less. NOTE : This chart is an approximate
distance reference and is a little
conservative. For a much more accurate
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These distances are calc lated for a 12 volt
calculated olt
system. Multiply distances by 2 for a 24 volt wire sizing, use our new Wire Size
system. Multiply distances by 4 for a 48 volt Calculator tool. It can calculate wire size
system. using 3%, 4%, or 5% losses plus you can
select 12, 24, or 48 volt systems
, , y
“

.

Solar Engineering Wire chart

Wire chart for connecting 12 Volt solar panels to the Charge Controller

#12 #10 #8 #6 #4 #3 #2 #1 #1/0 #2/0
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4 22.7 36.3 57.8 91.6 146 184 232 292 369 465
6 15.2 24.2 38.6 61.1 97.4 122 155 195 246 310
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8 11.4
11 4 18.2
18 2 28.9
28 9 45.8
45 8 73.1
73 1 91.8
91 8 116 146 184 233
10 9.1 14.5 23.1 36.7 58.4 73.5 92.8 117 148 186
12 7.6 12.1 19.3 30.6 48.7 61.2 77.3 97.4 123 155
14 6.5 10.4 16.5 26.2 41.7 52.5 66.3 83.5 105 133
16 5.7 9.1 14.5 22.9 36.5 45.9 58.0 73.0 92.0 116
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18 5.1 8.1 12.9 20.4 32.5 40.8 51.6 64.9 81.9 103
20 4.6 7.3 11.6 18.3 29.2 36.7 46.4 58.4 73.8 93.1
25 3.6 5.8 9.3 14.7 23.4 29.4 37.1 46.8 59.1 74.5
30 3.1 4.8 7.7 12.2 19.5 24.5 30.9 38.9 49.2 62.1
35 2.6
26 4.2
42 6.6
66 10.5
10 5 16.7
16 7 20.9
20 9 26.5
26 5 33.4
33 4 42.2
42 2 53.2
53 2
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40 2.3 3.6 5.8 9.2 14.6 18.4 23.2 29.2 36.9 46.5

If you have 3 solar panels rated at 6 amps each, mounted 30 feet from the Charge Controller, then you would
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move down the chart to 18 amps (3 panels * 6 amps), and across to 32.5 (closest to 30), and then up the chart
to #4. You would need at least #4 gauge wire (awg) to move 18 amps 30 feet with a minimum voltage drop of
3% or less, an acceptable loss. If you can't find the exact numbers, choose either a larger gauge wire (smaller
number) or select a distance longer than your actual distance.
“


Solar Engineering Inverter

Motors and power supplies usually run warmer and less
An inverter is a device which changes DC power efficiently on mod-sine wave power. Some things, like
stored in a battery to standard 120/240 VAC fans, amplifiers, and cheap fluorescent lights, give off an
electricity (also referred to as 110/220). Most audible buzz on modified sine wave power. However,
solar power systems generate DC current which modified sine wave inverters make the conversion from
is stored in batteries. DC to AC very efficiently. They are relatively
y y y y
inexpensive, and many of the electrical devices we use
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Nearly all lighting, appliances, motors, etc., are every day work fine on them.
designed to use ac power, so it takes an inverter
to make the switch from battery-stored DC to Sine wave inverters can virtually operate anything. Your
standard power (120 VAC, 60 Hz).
p ( , )
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utility company provides sine wave power, so a sine
wave inverter is equal to or even better than utility
supplied power. A sine wave inverter can "clean up"
In an inverter, direct current (DC) is switched utility or generator supplied power because of its internal
back and forth to produce alternating current processing. Inverters are made with various internal
(AC). Then it is transformed, filtered, stepped, features and many permit external equipment interface.
y p q p
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etc.
etc to get it to an acceptable output waveform
waveform. Common internal features are internal battery chargers
The more processing, the cleaner and quieter which can rapidly charge batteries when an AC source
the output, but the lower the efficiency of the such as a generator or utility power is connected to the
conversion. The goal becomes to produce a inverter's INPUT terminals. Auto-transfer switching is
waveform that is acceptable to all loads without also a common internal feature which enables switching
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sacrificing too much power into the conversion from either one AC source to another and/or f
f ih h d/ from utility
ili
process. power to inverter power for designated loads.

Inverters come in two basic output designs - sine Battery temperature compensation, internal relays to
wave and modified sine wave. Most 120VAC control loads, automatic remote generator starting /
, g g
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devices can use the modified sine wave, but stopping and many other programmable features are
there are some notable exceptions. Devices available. Most inverters produce 120VAC, but can be
such as laser printers which use triacs and/or equipped with a step-up transformer to produce
silicon controlled rectifiers are damaged when 120/240VAC. Some inverters can be series or parallel
p
provided mod-sine wave power.
p "stacked-interfaced" to produce 120/240VAC or to
“

increase the available amperage.


Solar Engineering The Power Inverter

Square Wave power inverters :

This is the least expensive and least desirable
Unless you plan on using battery power for type. The square wave it produces is inefficient
everything,
everything you will need a Power Inverter Since
Inverter. and is hard on many types of equipment These
equipment.
the majority of modern conveniences all run on inverters are usually fairly inexpensive, 500 watts
RGY “ MAD EASY

220 volts AC, the Power Inverter will be the heart or less, and use an automotive cigarette lighter
of your Solar Energy System. It not only converts plug-in. Don't even consider one of these types
the low voltage DC to the 220 volts AC that runs of power inverters for a home system.
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most appliances, but also can charge the
batteries if connected to the utility grid or a AC Modified Sine Wave power inverters :
Generator as in the case of a totally independent
stand-alone solar power system. This is probably the most popular and
economical type of power inverter. It produces
yp p p
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an AC waveform somewhere between a square
wave and a pure sine wave. Modified Sine Wave
inverters, sometimes called Quasi-Sine Wave
inverters are not real expensive and work well in
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all but the most demanding applications and
even most computers work well with a Modified

Sine Wave inverter. However, there are
exceptions. Some appliances that use motor
speed controls or that use timers may not work
p y
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quite right with a Modified Sine Wave inverter.
And since more and more consumer products
are using speed controls & timers, I would only
recommend this type of inverter for smaller
installations such as a camping cabin
cabin.
“



True Sine Wave power inverters :
A True Sine Wave power inverter produces the closest Grid Tie Power I
G id Ti P Inverters
t
to a pure sine wave of all power inverters and in many If you are connected to normal Utility company
cases produces cleaner power than the utility company power and just want to add some Free Sun Power
itself. It will run practically any type of AC equipment electricity to reduce your electric bill and you do not
and is also the most expensive Many True Sine Wave
expensive. need a totally independent system, it is possible that
power inverters are computer controlled and will a Grid Tie power inverter will suit your needs. With a
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automatically turn on and off as AC loads ask for Grid Tie power inverter, whatever electricity that
service. I believe they are well worth the extra cost. I your solar panels produce will reduce the amount
use a True Sine Wave power inverter myself and find supplied by the utility company, in effect lowering
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that its t
th t it automatic capabilities makes it seem more lik
ti biliti k like your bill And if you are producing more power than
bill. And,
Utility Company power. The Xantrex 2500 watt power you are using, you can actually sell the extra power
inverter back to the utility company! For this type of setup a
much smaller battery bank can be installed just to
cover short term outages from a few minutes to an
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I use has a search feature and checks every couple of
hour or two. In fact, if you don't have frequent long
seconds for anything that wants AC, then it powers up
term power outages and don't need back-up power,
automatically. You just flick on a light switch (or
then you will not need any batteries at all. (But,
whatever) and it works. When you turn off the light or
really, what utility company never fails? :)
the refrigerator kicks off for example, the power
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inverter shuts d
i t h t down t save b tt
to battery power.

While the Modified Sine Wave inverter (sometimes
called a Quasi Sine Wave inverter) is nearly half the
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price of a True Sine Wave inverter I would still
inverter,
recommend using a True Sine Wave inverter if you
want to supply automatic power to a normal home
using a wide variety of electrical devices. Also, most
appliances run more efficiently and use less power
“

with a T
ih True Si
Sine W
Wave i inverter as opposed to a
d
Modified Sine Wave power inverter.



Power Inverter considerations.
The Power Inverter is connected directly to the
batteries and the ain AC breaker panel to supply Input voltages. Should I use a 12, 24, or 48 volt
power f from ththe b tt i
batteries t to th the l d
loads Inverter?
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appliances). Check out Wires & Cables for more
info on the necessary wire size for installing one The main consideration when deciding on the
or use our new Wire Size Calculator. The Power input voltage (from your battery bank) of your
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Inverter converts th l
I t t the low oltage DC t 220 volts
lt to lt Inverter is the distance between your solar panel
AC. Power Inverters are available for use on 12, array and your battery bank. The higher the
24, or 48 volt battery bank configurations. Most voltage, the lower the current and the smaller the
Power Inverters can also charge the batteries if (expensive) cables need to be. Of course, when
you decide on a system voltage the Solar
voltage,
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connected t th AC li
t d to the line. Alt
Alternatively, th AC
ti l the
line input could be your own AC Generator in the Panels, Inverter, and Battery Bank all need to
case of a stand-alone solar power system. When use the same voltage. More detailed information
using a AC Generator to charge the batteries, on voltage & current is explained in the tutorial
on Power & Watts To help decide on which
Watts.
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voltage to use, check out our Wire Size

the Power Inverter transfers the AC Generator Calculator which can tell you what size wire is
power to the loads via a relay. This way the AC needed to connect the solar panels to your
Generator not only charges the batteries but also equipment area You can try all 3 different
area.
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supplies your AC power while it is running. If voltages to see the change that it can make in
your Generator is at least 5000 watts, you can wire size.
charge your batteries and have extra AC power
at the same time.
“



Two i
T inverters can b i t ll d i a configuration
t be installed in fi ti
known as stacking that can provide more power
or higher voltage. If two compatible inverters are
stacked in series you can double the output
voltage. This would be the technique to use to
provide 220/240 volts AC. On the other hand, if
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you configure them in parallel, you can double
your power. Two 4000 watt inverters in parallel
would give you 8000 watts (8KW) of Electricity
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For a small system on a budget, a 2000 to 3000
watt Modified Sine Wave power inverter will do
the job for around Rs.2200 to Rs.1500. Expect to
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pay up t R 1000 more f a T
to Rs.1000 for True Si
Sine WWave
power inverter if you want to be able to run
anything and have the automatic features. These
higher quality Power Inverters are computer
controlled and once set-up can control your 220
set up,
ANDING SO

volts AC, battery charging, and even auto-start

compatible AC Generators; all automatically. If
your goal is to provide real home power, A True
Sine Wave inverter is really your best choice.
“UNDERSTA

The extra cost, in the long run, is a good
investment in performance and reliability. For a
small seasonal use cabin, a Modified Sine Wave Inverter Stacking: Using multiple inverters
inverter would probably do the job.
“


Solar Engineering How to Determine

How many solar panels and batteries
I'll need?
This will depend on how much electricity
p y
you are going to need and how many days
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you plan to be able to run on just battery
power alone (no sun at all). To assist you
in determining the size system you will
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need,
need our System Sizing Estimator will
help you calculate the number of solar
panels you'll need and what size battery
bank is required. We also provide a
Battery Bank Designer tool to show you
y g y
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how to wire your battery bank for a 12, 24,
or 48 volt system.

What kind of wires or cables will I need
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to hook all this stuff together?

The Wires & Cables tutorial covers this
q
question and provides a handy chart to
p y
“UNDERSTA

calculate the required wire sizes based on
the voltage of your system and the
distances between components. Also, our
new Wire Size Calculator tool will
calculate wires sizes for you
you.
“


Solar Engineering Solar power system configuration

System Size 2.100kW 3.150kW 4.200kW 5.250k
Generation(*Day/KW ) 8 - 10 12 -16 16 - 21 20 -25
Generation (*Annual/Kw) 2,900 - 3,690 4,300 - 5,100 5,800 - 6,500 7,300 – 8
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Solar Module 175watts (12) 175watts (18) 175watts(24) 75watts (30)
Inverter 2500 3300 3800 5000A
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*KWh
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This small energy efficient home uses
gy
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Solar Panels (6nos) * 80 W

Charge Controller 60 amp
Inverter 2500W Puresine wave
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Batteries. (15 nos)* 105 AH
“


Solar Engineering Solar power system configuration

System Size 2.160kW 3.240kW 4.320kW 5.040kW

Generation kWh/Day 8 -10 12 - 16 16 - 21 20 -25
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Generation kWh/annum 2,900 -3,690 4,300 - 5,100 5,800 - 6,500 7,300 - 8000
Solar Module (Watt) Mono 180 Mono 180 Mono 180 Mono 180
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(x 12) (x 18) (x 24) (x 30)
Inverter 2500 2500 3300 4500 5000A
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5.4KWh
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3.2KWh
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“


Solar Engineering Largest Global Photovoltaic Power Plants
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“


Solar Engineering Global Solar Photovoltaic Installation

Install Wp/capit
off on off on Total Module kW h/kWp yr
kW·h/kWp·yr Feed in
Feed-in Tariff
Country or R i
C t Region ed
d a
grid grid grid grid 2007 Price Insolation EU¢/kW·h
Report Nat. Int. 2007 Total
Δ Δ Σ Σ €/Wp

World 127.9 2,130 2,258 662.3 7,178 7,841 2.5–11.2 800–2,902 0–59.3

Germany 35 1,100 1,135 35 3,827 3,862 46.8 4.0–5.3 1,000–1,300[28] 51.8–56.8

Japan[29][27] 1.562 208.8 210.4 90.15 1,829 1,919 15 2.96 1,200–1,600 Ended(2005)
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United States 55 151.5 206.5 325 505.5 830.5 2.8 2.98 900–2,150[28] 1.2–31.04(CA)

Spain] 22 490 512 29.8 625.2 655 15.1 3.0–4.5 1,600–2,200 18.38–44.04
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Italy 0.3 69.9 70.2 13.1 107.1 120.2 2.1 3.2–3.6 1,400–2,200 36.0–49.0

Australia 5.91 6.28 12.19 66.45 16.04 82.49 4.1 4.5–5.4 1,450–2,902[33] 0–26.4(SA'08)

South Korea 0 42.87 42.87 5.943 71.66 77.60 1.6 3.50–3.84 1,500–1,600 56.5–59.3

France 0.993 30.31 31.30 22.55 52.68 75.23 1.2 3.2–5.1 1,100–2,000 30.0–55.0
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Netherland 0.582 1.023 1.605 5.3 48 53.3 3.3 3.3–4.5 1,000–1,200 1.21–9.7

Switzerland 0.2 6.3 6.5 3.6 32.6 36.2 4.9 3.18–3.30 1,200–2,000 9.53–50.8

Austria 0.055 2.061 2.116 3.224 24.48 27.70 3.4 3.6–4.3 1,200–2,000 >0
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Canada[ 3.888
3 888 1.403
1 403 5.291
5 291 22.86
22 86 2.911
2 911 25.78
25 78 0.8
08 3.76
3 76 900–1,750
900 1 750 0–29.48(ON)
0 29 48(ON)

Mexico] 0.869 0.15 1.019 20.45 0.3 20.75 0.2 5.44–6.42 1,700–2,600 None

United Kingdom 0.16 3.65 3.81 1.47 16.62 18.09 0.3 3.67–5.72 900–1,300 0–11.74(exprt)

Portugal 0.2 14.25 14.45 2.841 15.03 17.87 1.7 1,600–2,200
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Norway 0.32 0.004 0.324 7.86 0.132 7.992 1.7 11.2 800–950 None

Sweden 0.271 1.121 1.392 4.566 1.676 6.242 0.7 3.24–7.02 900–1,050 None

Denmark 0.05 0.125 0.175 0.385 2.69 3.075 0.6 5.36–8.04 900–1,100 None

Israel 0.5
05 0 0.5
05 1.794
1 794 0.025
0 025 1.819
1 819 0.3
03 4.3
43 2,200–2,400
2 200 2 400 13.13–16.40
13 13 16 40
“


Solar Engineering Payback

Energy Payback Time and Energy Returned on Energy Invested

The energy payback time is the time required to produce an amount of energy as great as what was
consumed during production. The energy payback time is determined from a life cycle analysis of
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energy.

Another key indicator of environmental performance, tightly related to the energy payback time, is
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the ratio of electricity generated divided by the energy required to build and maintain the equipment.
This ratio is called the energy returned on energy invested (EROEI). Of course, little is gained if it
takes as much energy to produce the modules as they produce in their lifetimes.
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This should not be confused with the economic return on investment, which varies according to local
energy prices, subsidies available and metering techniques. Life-cycle analyses show that the
energy intensity of typical solar photovoltaic technologies is rapidly evolving. In 2000 the energy
payback time was estimated as 8 to 11 years[75], but more recent studies suggest that technological
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progress h reduced thi t 1 5 t 3 5 years f crystalline silicon PV systems
has d d this to 1.5 to 3.5 for t lli ili t

Thin film technologies now have energy pay-back times in the range of 1-1.5 years (S.EuropeWith
lifetimes of such systems of at least 30 years, the EROEI is in the range of 10 to 30.
“UNDERSTA

They thus generate enough energy over their lifetimes to reproduce themselves many times (6-31
reproductions, the EROEI is a bit lower) depending on what type of material, balance of system (or
BOS), and the geographic location of the system.
“


Solar Engineering Average cost in Paisa/kWh over 20 years for solar power panels

Paisa per kilowatt-hour of electricity generated by a photovoltaic system as function of the investment cost and the efficiency,
p yg y p y y,
assuming some accounting parameters such as cost of capital and depreciation period. The row headings on the left show the
total cost, per peak kilowatt (kWp), of a photovoltaic installation.
The column headings across the top refer to the annual energy output in kilowatt-hours expected from each installed peak
kilowatt. This varies by geographic region because the average insolation depends on the average cloudiness and the thickness
of atmosphere traversed by the sunlight. It also depends on the path of the sun relative to the panel and the horizon.
Panels can be mounted at an angle based on latitude, which can add to total energy output.[65] Solar tracking can also be
utilized to access even more perpendicular sunlight, thereby raising the total energy output. The calculated values in the table
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reflect the total cost in Paisa per kilowatt-hour produced. They assume a 10% total capital cost (for instance 4% interest rate, 1%
operating and maintenance cost, and depreciation of the capital outlay over 20 years).
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2400 2200 2000 1800 1600 1400 1200 1000 800
Cost kWh/kWp• kWh/kWp• kWh/kWp• kWh/kWp kWh/kWp kWh/kWp kWh/kWp kWh/kWp kWh/kWp
y y y •y •y •y •y •y •y
10000 Rs/kWp 0.8 0.9 1.0 1.1 1.3 1.4 1.7 2.0 2.5
30000 Rs/kWp 2.5 2.7 3.0 3.3 3.8 4.3 5.0 6.0 7.5
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50000 Rs/kWp 4.2 4.5 5.0 5.6 6.3 7.1 8.3 10.0 12.5
70000 Rs/kWp 5.8 6.4 7.0 7.8 8.8 10.0 11.7 14.0 17.5
90000 Rs/kWp 7.5 8.2 9.0 10.0 11.3 12.9 15.0 18.0 22.5
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110000 Rs/kWp
/ 9.2
92 10.0
10 0 11.0
11 0 12.2
12 2 13.8
13 8 15.7
1 18.3
18 3 22.0
22 0 27.5
2

130000 Rs/kWp 10.8 11.8 13.0 14.4 16.3 18.6 21.7 26.0 32.5
150000 Rs/kWp 12.5 13.6 15.0 16.7 18.8 21.4 25.0 30.0 37.5
170000 Rs/kWp 14.2 15.5 17.0 18.9 21.3 24.3 28.3 34.0 42.5
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190000 Rs/kWp 15.8 17.3 19.0 21.1 23.8 27.1 31.7 38.0 47.5
210000 Rs/kWp 17.5 19.1 21.0 23.3 26.3 30.0 35.0 42.0 52.5
230000 Rs/kWp 19.2 20.9 23.0 25.6 28.8 32.9 38.3 46.0 57.5
250000 R /kW
Rs/kWp 20.8
20 8 22.7
22 7 25.0
25 0 27.8
27 8 31.3
31 3 35.7
35 7 41.7
41 7 50.0
50 0 62.5
62 5
“


Solar Engineering Pros : Cons
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Solar Engineering Environmental impacts

Unlike fossil fuel based technologies, solar power does not lead to any harmful
emissions during operation, but the production of the panels leads to some amount
of pollution. This is often referred to as the energy input to output ratio. In some
analysis, if the energy input to produce it is higher than the output it produces it
RGY “ MAD EASY

can be considered environmentally more harmful than beneficial.
DE

Also, placement of photovoltaics affects the environment. If they are located where
f ff f
photosynthesizing plants would normally grow, they simply substitute one
potentially renewable resource (biomass) for another
OLAR ENER

It should be noted, however, that the biomass cycle converts solar radiation
energy to electrical energy (plants make electricity? check again) with significantly
less efficiency than photovoltaic cells alone. And if they are placed on the sides of
y p y p
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buildings (such as in Manchester) or fences, or rooftops (as long as plants would

not normally be placed there), or in the desert they are purely additive to the
renewable power base.
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Solar Engineering Greenhouse gases

Life cycle greenhouse gas emissions are now in the range of 25-32
g/kWh and this could decrease to 15 g/kWh in the future
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For comparison, a combined cycle gas-fired power plant emits some 400
DE

g/kWh and a coal-fired power plant 915 g/kWh and with carbon capture
and storage some 200 g/kWh.

Only nuclear power and wind are better emitting 6-25 g/kWh and 11
better,
OLAR ENER

g/kWh on average. Using renewable energy sources in manufacturing
and transportation would further drop photovoltaic emissions.
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Solar Engineering Cadmium

One issue that has often raised concerns is the use of cadmium in cadmium
telluride solar cells (CdTe is only used in a few types of PV panels). Cadmium in
its metallic form is a toxic substance that has the tendency to accumulate in
ecological food chains.
RGY “ MAD EASY

The amount of cadmium used in thin-film PV modules is relatively small (5-10
y (
DE

g/m²) and with proper emission control techniques in place the cadmium
emissions from module production can be almost zero. Current PV technologies
lead to cadmium emissions of 0.3-0.9 microgram/kWh over the whole life-
cycle.[74] Most of these emissions actually arise through the use of coal power
OLAR ENER

for the manufacturing of the modules, and coal and lignite combustion leads to
much higher emissions of cadmium.
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Life-cycle cadmium emissions f
Lif l d i i i from coal i 3 1 microgram/kWh, li it 6 2 and
l is 3.1 i /kWh lignite 6.2, d
natural gas 0.2 microgram/kWh. Note that if electricity produced by photovoltaic

panels were used to manufacture the modules instead of electricity from
burning coal, cadmium emissions from coal power usage in the manufacturing
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process could be entirely eliminated
“


Solar Engineering Disadvantages

1. Cost may not cover lifespan savings unless a preferential feed-in tariff is offered
by the grid network. But this depends on location and energy prices.
RGY “ MAD EASY

2. Solar electricity is often initially more expensive than electricity generated by other
sources.
DE

3. Solar electricity is not available at night and is less available in cloudy weather
conditions from conventional silicon based technologies. Therefore, a storage or
complementary power system is required. However, the use of germanium in
OLAR ENER

amorphous silicon-germanium thin film solar cells provides residual power
generating capacity at night due to background infrared radiation.

4.
4 Limited power density: Average daily insolation in the contiguous U S is 3-7 and
U.S. 3 7
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on average lower in Europe.

5. Solar cells produce DC which must be converted to AC (using a grid tie inverter)
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when used in currently existing distribution grids. This incurs an energy loss of 4-
f
12%.
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Solar Engineering Advantages

1. The 89 petawatts of sunlight reaching the earth's surface is plentiful - almost 6,000
times more than the 15 terawatts of average power consumed by humans.
Additionally, solar electric generation has the highest power density (global mean of
170 W/m²) among renewable energies
energies.
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2. Solar power is pollution free during use. Production end wastes and emissions are
manageable using existing p
g g g pollution controls. End-of-use recycling technologies are
y g g
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under development.

3. Facilities can operate with little maintenance or intervention after initial setup.
OLAR ENER

4. Solar electric generation is economically superior where grid connection or fuel
transport is difficult, costly or impossible. Examples include satellites, island
communities, remote locations and ocean vessels.
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Solar Engineering Advantages

5. When grid-connected, solar electric generation can displace the highest cost
electricity during times of peak demand (in most climatic regions), can reduce grid
loading, and can eliminate the need for local battery power for use in times of
darkness and high local demand; such application is encouraged by net metering.
RGY “ MAD EASY

Time-of-use net metering can be highly favorable to small photovoltaic systems.
DE

6. Grid-connected solar electricity can b
6 G id t d l l t i it be used ld locally th
ll thus reducing
d i
transmission/distribution losses (transmission losses were approximately 7.2% in
1995).
OLAR ENER

7. Once the initial capital cost of building a solar power plant has been spent,
operating costs are extremely low compared to existing power technologies.
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8. C
Compared to f fossil and nuclear energy sources, very little research-money has

been invested in the development of solar cells, so there is much room for
improvement. Nevertheless, experimental high efficiency solar cells already have
efficiencies of over 40% and efficiencies are rapidly rising while mass production
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costs are rapidly falling.
“


Solar Engineering Photovoltaics research institutes

1. Some universities and institutes which have a photovoltaics research department.
2. Solar Energy Materials Research Group (http://emat-solar.lbl.gov/) at Lawrence Berkeley National Laboratory
3. The Center for Functional Nanomaterials (http://www.bnl.gov/cfn/) at Brookhaven National Laboratory
4. Solar Energy Laboratory (http://www.soton.ac.uk/~solar) at University of Southampton
5. National Renewable Energy Laboratory NREL (http://www.nrel.gov)
6. Energy & Environmental Technology Application Center (http://www.e2tac.org/) at the College of Nanoscale Science
RGY “ MAD EASY

and Engineering SUNY at Albany
7. Institut für Solare Energiesysteme ISE (http://www.ise.fhg.de) at the Fraunhofer Institute
8. Energy research Centre of the Netherlands (ECN) (http://www.ecn.nl/en/zon/)
DE

9.
9 Imperial College London: Experimental Solid State Physics (http://www.imperial.ac.uk/research/exss/)
(http://www imperial ac uk/research/exss/)
10. Instituto de Energía Solar (http://www.ies.upm.es/) , at Universidad Politécnica de Madrid (http://www.upm.es/)
11. Centre for Renewable Energy Systems Technology (http://www.lboro.ac.uk/departments/el/research/crest/) , at
Loughborough University (http://www.lboro.ac.uk)
12. School of Photovoltaic and Renewable Energy Engineering at The University of New South Wales
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13.
13 Centre for Sustainable Energy Systems (http://solar anu edu au) at the Australian National University
(http://solar.anu.edu.au)
14. Ecole Polytechnique Fédérale de Lausanne (http://www.epfl.ch/) Prof. Graetzel invented dye sensitized cells here
15. Advanced Energy Systems (http://www.hut.fi/Units/AES) at Helsinki University of Technology
16. Institute of Materials Research, Salford University (http://www.imr.salford.ac.uk/)
17. The Centre for Electronic Devices and Materials (http://www.shu.ac.uk/research/meri/electronic/) at Sheffield Hallam
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University
18. The Centre for Advanced Investigations on Electric Engineering (http://www.sees.cinvestav.mx/) at The National Polytechnic

Institute of Mexico
19. The Solar Caliometry Lab (http://me.queensu.ca/people/harrison/research/solar/index.htm) at Queen's University
20. Institute of microtechnology (http://www2.unine.ch/pv) at University of Neuchatel Switzerland (http://www2.unine.ch)
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21.
21 University of Konstanz (http://www uni-konstanz de/photovoltaics/)
(http://www.uni-konstanz.de/photovoltaics/)
22. Arizona State University Photovoltaic Testing Laboratory (http://www.poly.asu.edu/ptl/)
23. Institute of Energy Conversion (http://www.udel.edu/iec) at University of Delaware (http://www.udel.edu)
24. World Alliance for Decentralized Energy (http://www.localpower.org)
25. Florida Solar Energy Center at University of Central Florida (http://www.ucf.edu)
26.
26 Linz I tit t for Organic S l C ll (LIOS) (htt //
Li Institute f O i Solar Cells (http://www.lios.at)
li t)
“


Solar Engineering

This Solar Home runs a freezer, computer,
27 inch color tv, microwave, and assorted
other lights and devices In the winter I run
devices.
RGY “ MAD EASY

my generator for 45 to 60 minutes per day
to charge the batteries up to about 90%.
DE

Since some winter days are sunny the
sunny,
generator is not used every day.
OLAR ENER

For a small to medium sized Solar Energy System, a 4KW to 7KW watt
generator will work nicely. The price range is Rs. 50,000 to 200,000
depending on brand & features You can spend much more on Auto-Start
features. Auto Start
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capability, diesel fueled, or propane fueled generators but I believe only

large systems would make these generators economical. Although you can
buy a 7000 watt model with electric start at Home Depot for Rs. 300,000
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and after almost 5 years of use, realize it is bigger than your need. Still, it's
nice to have the extra power.
“


Solar Engineering Frequently Asked Questions

How much do PV cells degrade with rising/falling
How do I know what size PV system I need?
temperature?
The best indicator for sizing a PV system is your
The electrical outputs of PV cells are specified for a
historical electrical usage, or the number of kilowatt
given temperature (usually +25C). The behaviour when
hours (kWh) you consume each year. It is especially
the temperature rises above or falls below the optimum
p p important to determine an annual average for your kWh
given by the manufacturer depends upon the physical
usage, because many families experience seasonal
RGY “ MAD EASY

properties of the photovoltaic material used. As a general
spikes in usage. This average gives you a starting point
rule, the output will drop. For precise information on a
for comparing the energy output of various systems.
particular cell or module, see the manufacturer's data
sheet.
DE

What is Net Metering? ?
What are Building Integrated photovoltaics? If you take the AC output of your inverter and run it to the
mains coming from your utility power meter, any excess
BIPV or 'Building Integrated PhotoVoltaics' is an industry
power you generate will feed back into the utility grid and
buzz phrase, which indicates photovoltaic modules
drive your power meter backwards. This is called Net
integrated into various construction materials Solar roof
materials.
OLAR ENER

Metering. Effectively, you will be paid the going retail
tiles are an example. Similar combination materials can
price for your electricity up to the amount of energy you
be used on any other well illuminated surface.
use per billing period. Any excess energy you generate
will be credited at a lower rate, or perhaps not at all.
What is a Solar Tracker?
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A Solar Tracker is a device which aims a solar panel In many countries, all PV electricity generated is
directly at the sun in order to maximize energy output.

purchased by the utility company at a rate higher than
The mechanisms for achieving this can be as varied as the tariff applied for consumed electricity. In this case, a
human ingenuity allows. dedicated metering exists for PV generation, plus a
second metering for domestic consumption. Each applies
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What happens if the sun doesn't shine? different tariffs. So, in this case, not only the excess
Your PV system will continue to produce electricity electricity is remunerated, but so too is the total amount
during cloudy weather at a slower rate. At night or during of PV production.
inclement weather, additional electricity is provided to
y
your home through your utility connection.
g y y
“


Solar Engineering
Frequently Asked Question
Can I sell excess solar electricity back to my utility? How do grid connected PV systems work?
Electric utilities in many countries give retail credit to solar customers Solar electric systems use PV technology to convert sunlight into
who feed excess solar electricity back to the power grid. Known as electricity during daylight hours. If your home or office requires more
"net metering," this utility policy is implemented by letting your electricity than can be provided by your PV system, the balance is
electric meter spin backwards when you feed excess electricity into
the grid. In many countries, all PV electricity generated is purchased provided through your utility connection.
by the utility company at a rate higher than the tariff applied for
consumed electricity. I thi case, a d di t d metering exists f PV
d l t i it In this dedicated t i i t for Isn't PV electricity expensive?
generation, plus a second metering for domestic consumption. Each
RGY “ MAD EASY

applies different tariffs. So, in this case, not only is the excess No. The cost of PV technology has dropped dramatically in the past
electricity remunerated, but so too is the total amount of PV ten years and, thanks to government incentives or subsidies, a PV
production. system may be your most cost-effective power solution.
DE

Does my grid connected PV system have to include batteries? What is a grid connected PV system?
No. Batteries are only essential if you want 'back-up' power in the Grid connected means that your system is connected to the utility
case of a utility outage. Otherwise, your grid connected PV system lines, or the "grid". A grid connected PV system is designed to meet
will send any excess generated electricity back to the utility, using
the utility grid (rather than batteries) as the storage medium. all, or a portion of your daily energy needs. This connection enables
you to obtain the balance of your electricity from your local utility. It
also allows you to send excess solar electricity back to your power
What is an Inverter?
OLAR ENER

company for later use
use.
An electrical device which converts direct current [DC] to alternating
current [AC]. Solar cells produce a direct current. Unfortunately,
most of the electrical devices we commonly use expect a standard I already have utility power, so why should I choose PV?
AC power supply. An inverter takes the DC from the solar cells and Photovoltaic systems allow you to lock your electricity rates at
creates a useable form of AC. Besides doing this, an inverter may today's prices. With fossil fuels likely to become more expensive in
also be connected to the electric grid and/or a battery backup
syste
system. the future, purchasing a PV system today is a smart economic move.
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In some countries, there is the possibility of enjoying f
f feed-in tariffs,
ff
or investment incentives. PV systems also offer greater self-
Can I use a grid connected PV system as a back-up source

during a utility power outage? sufficiency, reduce dependence on imported oil and are far better for
the environment than power from conventional power plants.
A grid connected PV system can continue to provide electricity to
your home during an outage if it has an inverter and batteries.
How long has PV been around?
g
“UNDERSTA

What is photovoltaic technology? PV has been used as the primary source of electricity on satellites
Solar electric systems use a technology called photovoltaics, or PV, since the 1950s. Since the 1970s, PV has been used more and more
that converts sunlight into electricity. PV cells are made from for "earth-based" applications as costs declined tenfold. Today, the
semiconductive material, usually silicon. They are silent and non- PV industry is a billion dollar per year industry with primary markets
polluting, utilise a source of energy that renews itself, and require no in developing countries. In many countries, PV is the most reliable
special training to operate. and least costly form of electricity available.
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Solar Engineering
Contact Us
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**For Soft and hard copies or consultancy :

centre for application of renewable energy
Navi Mumbai 400706 (India)
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email :care@ care-india.com
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