- Free Tutorials -
Lets give you some
solid basics about off-grid solar power -
by introducing some of the big topics
Click on the
topics to jump to that subject.
a solar panel and how does it make electricity?
Grid VS. Grid Tie system
Mounting solar panels
up solar arrays
What is a solar panel and how does it make electricity?
Photovoltaic (PV) solar panel is a semiconductor device
that is made the same way that transistors
and computer chips are made. It is the exact same material
-Silicon Carbide with trace amounts of other
chemicals which enable the silicon (glass) to make
electricity from sunlight that hits it. The "photons" of
light from the sun -liberate electrons from the atoms in
the panel's layers and these are collected by a metal grid
on either side of the panel. One side is positive and the
other negative. The trace amounts of other chemicals in
the silicon give it a negative or positive affinity. These
different layers are on top of each other in the panel.
Over many decades, the efficiency of the panel will go
down a bit. That said, it will produce over 75% of it's
original output for at least 30 years.
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What are Off-Grid and Grid-Tie Solar power systems?
-Tie" system is one which is directly connected with the
commercial power lines. There are normally no batteries to
store power for cloudy days in a grid-tie system. The
advantage is that you don't need to buy batteries. the dis-advantage
is that your system will be shut down during general power
outages and you will still need a generator for emergency
power. Grid-tie systems "spin the meter backwards" during
the day and feed power into the commercial power system.
In the evening, you draw power from the power lines as
Thus, you only pay for the differential between what you
made during the day and what you used at night.
Grid-tie system require a NABCEP certified installer and
inspection by the power company before use.
With an off-grid
battery-based system, you are autonomous from the
commercial power lines. Your system charges a bank of
batteries during the day and you use that power at night.
Homeowners are allowed to do electrical work on their own
homes in most jurisdictions. Thus, you could build an
off-grid system without an electrical inspection in most
areas. As well, you can build any size off-grid system.
You might build one only to power your freezers... or
power a weekender cabin. You can also build portable
off-grid systems on a trailer.
The downside to off-grid is that you need to buy batteries
every 10 years or so. If you don't use no-maintenance
batteries, you'll also need to keep them topped-off - so
there is a little maintenance involved.
People who just want to cut
their electrical bill often opt for grid-tie systems.
Those who want to go "off-grid" and be totally
self-sufficient opt for off-grid battery-based systems.
Federal tax incentives give credit for both types. The tax
credit is only for the actual hardware and not labor.
Since grid-tie systems normally require a professional
installer, a much smaller parts of your investment
qualifies for the tax credit with grid-tie.
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Charge Controllers - What are they?
A Charge controller is
the device that regulates the charging of your battery
bank in an off-grid system. It is just like a battery
charger for an automotive battery- but its a lot
smarter. These controllers monitor the output of your
solar panel array and charge the batteries in several
stages. Batteries are best charged more heavily at first
and less strongly as they top-off.
MMPT type charge controllers are the latest technology and
are able to convert 30%-40% more power from the solar
panels into actual battery charging current (compared to
the older traditional type chargers. They optimize the
battery charging - almost continuously. MPPT stands for
Maximum Power Point Tracking. The charge controller
must know what the battery bank voltage is. This is set by
jumpers on the controller or on the LCD screen of the
controller. Each controller has a maximum current it can
handle and a maximum voltage input. Having the ability to
take a higher voltage from the solar array, it allows you
to configure the solar panels for a higher voltage -so
that you loose less power on the wire run from the panels
to the charge controller. Many controllers also store data
from each day. You can also install remote control "heads"
so that you can control it from inside the house.
The higher the battery bank
voltage you are using, the more power a given charge
controller can handle from the solar array. That's because
since the controller has a fixed maximum current in amps,
when you multiply the battery voltage by that maximum
current- you get the total wattage it can handle. The
higher that battery voltage, the more watts of panels it
can handle. Amps X Volts = Watts. Typically, you use
either 12 /24 or 48 volt battery banks. 24 volts is a good
balance an popular battery bank voltage.
Cost for medium-sized
charge controllers ranges from $250-$550. This is for
systems around 2000W. For small systems of under 1000W,
you might choose a traditional charge controller of much
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Batteries used for solar applications are always "Deep-Cycle" batteries.
This means that the battery can be charged and dis-charged
down to about 20% of it's total capacity without damage.
Realize that car batteries are designed to give just a
high pulse of power to start the motor. Deep-Cycle
batteries are used for trolling motors and ranch
applications etc. Deep-cycle batteries come in two types,
wet-cell and AGM. Wet-Cell batteries are the typical type
we see in cars. The "electrolyte" (batttery acid) is a
liquid. AGM (absorbed glass mat) batteries use a gelled
electrolyte. These are more expensive and are used where
you might spill battery acid (electric cars etc). Either
type can be used for solar systems.
Battery quality is determined
by the size and thickness of the lead plates and the
volume of electrolyte. You are paying a price for the
lead, so the bigger they are, the more they cost. With
wet-cells, you might use golf cart batteries, trolling
marine batteries or industrial wet-cell batteries from
fork-lifts etc. You should go down to your local
industrial battery supplier and see what the best value he
has is. You can configure batteries into any voltage
"bank" you choose, so really, you can get whatever the
best value is and then configure it using jumpers to your
desired voltage. The larger the batteries you buy, the
less jumpers you will need, so this saves time and money.
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The decisions you will have to make are- what battery bank
voltage I want, and how much power do I need in Amp-hours
total. Each battery is rated in Volts and Amp-Hours.
The typical battery bank voltages are 12 /24 /48. If you
don't need 12 volts DC for appliances like RV appliances
or radio equipment, you can and should go with a higher
voltage system. Why? Because you loose less in the same
wires with higher voltage and your wires are expensive
(copper). You'll need thicker and costlier wires for a 12
volt system. 24 volts is a good compromise voltage. Also,
other components like the inverter are available easily
for 24 volts. 48 volt inverters are un-common... less
Second decision is how many amp-hours total do you need.
Well, you take your solar panels total wattage, divide by
24 (if that's your battery voltage) and multiply that by
25. This gives you several days of operation off batteries
if it is rainy. I'm writing this on a laptop powered by
solar batteries after 4 days of no sun.
So, now you
have to wire up the batteries for your desired voltage and
amp-hours total. Batteries add up their voltage when you
wire them in series (plus to minus) and add up their
amp-hours when wired in parallel (positive to positive and
negative to negative). So, you first make a first bank of
individual batteries in series to get your desired voltage
(2 if they are 12 Volt and 4 if they are 6 volt to get 24
volts). The amp hours of that "bank" are the amp-hours of
one individual battery. (REMEMBER: you cannot mix
batteries of different types or age in the same system).
Now you have to clone that first configuration as many
times as it takes to add up the amp-hours for your total
system. You then wire these clone banks in parallel to get
your desired amp-hour total. I show exactly how to do this
in the video. You have to be VERY careful wiring these
banks. You have to wear safety glasses, no jewelry and
tape all the handles of your tools with electrical tape. I
don't suggest you attempt this after only reading this
briefing. This is the only dangerous part of building a
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Inverters are the electrical device that converts the DC
power from your batteries into AC power for your household
appliances. These come in two varieties : Sine-wave and
modified sine-wave. Sine-wave inverters are more expensive
and slightly less efficient. They must be used to delicate
equipment such as stereos, TV's, tower computers and all
things that have an electrical motor in them (Freezers,
vacuums etc). Modified sine-wave inverters are the common
ones you see on store shelves used for making AC power in
autos and RV's. These are around 97% efficient and are
quite inexpensive. They are good for light bulbs, laptop
power adapters.. and non-critical applications. Typically,
you might use both types in one system. You get what you
pay for, so if you buy a cheap sine-wave inverter, it will
probably not perform like you expect. With the modified
sine-wave units, there is less difference between cheap
and expensive. You need to calculate the total wattage of
all the appliances you want to power on solar. Then get
inverters which can easily power them. Remember, your
battery bank can only deliver about 1/4 of it's total
amp-hours continuously, so
if you are using say 24 volt batteries and have 500 amp
hours of them, 24 X 500 = 12,000 watts available.
1/4 of 12,000 watts is 3000 watts. So, you cannot draw
more than 3000 watts with your inverters continuously
without damaging the batteries. You'd like to draw less!
The less you draw, the longer they will last.
Calculating what you should
buy is determined by either your maximum budget or your
power needs (if you have unlimited $$) You will typically
make less than- or just enough for your needs. I show the
exact methods for calculating your outlays on each
hardware item in the full course.
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Photovoltaic solar panels come in many types. The most
The first two types are used to make rigid solar panels
that are used in 90% of all solar installations. They look
very similar, but the poly-crystalline have a
multi-faceted look to the individual cells themselves.
Both are about the same efficiency. This is about 16%.
This means that you can get well over 300 watts per square
meter of panel area. Typically though, a 200Watt panel is
about 16 square feet.
Poly and mono crystal panels are of high-quality and very
preferable for standard PV installations.
panels are made by coating glass with photovoltaic
material. These are cheaper to produce and have some
issues with longevity and consistency of output over time.
If made by well-known manufacturers, they can be a good
choice. You'd like a warranty!
Thin Film technology is the latest craze. It uses only
10% of the materials as a traditional panel and can be
used on unconventional surfaces (such as roofing tiles).
Thin Film panels are becoming available and when made by
reputable companies, they are a good option.
The most important things to desire in a solar panel is
a good value, a warranty and a reputable manufacturer.
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Individual panels are assembled into arrays using panel
mounts. Panel mounts allow you to raise the the panels up
into the sun's path and away from harm. They allow you to
secure the rather weak frames that panels are made with
-and rigidify them for weather resistance. It is possible
to construct panel frames from treated wood or metal. As
well, you can buy commercial mounting frames from
companies such as Zomeworks. Professional mounting frames
can me ordered so they mount on schedule 40 metal pipe.
This is a very popular mounting arrangement. The mounting
frames should allow for adjusting the angle of the
panels to face the sun in different seasons. Many people
use angle-iron with perforated holes which the panels can
be screwed to. Panels are pre-drilled with mounting holes.
When designing frames, these should be your criteria:
not-unwieldy... able to me handled by installers
You need to choose your location for full sun exposure-
then design panel frames to fit that location. If you have
tree shading, you'll need to raise the panels up into the
tree canopy. The angle adjustability needs to be from at
least 45 degrees to the ground and fully parallel to the
ground for northern latitudes. If you cannot adjust the
angle, you should set them so as to be fully facing the
Winter sun mid-day. This is because you need to favor the
Winter sun's lesser hours. In Summer, you'll still get
good sun coverage. Modern panels have a coating so they
make good energy from off-axis sunlight.
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up Solar Panel Arrays
Wiring up solar panels into "arrays" is
very similar to wiring up the battery banks. This is
because the BIG rule applies. Wiring in series adds up the
voltage and wiring in parallel adds up the current. Series
is like in a flashlight.. negative to positive again and
again. Parallel is wiring positive to positive and
negative to negative.
The process is this:
You select the battery bank voltage you want to go with
first. Then you select your charge controller- one that it
big enough to easily handle all your solar panels. You
will have spent about 50% of your total budget on panels
themselves. You then check your charge controller and KNOW
it's maximum voltage in. You then wire up a bank... a
set.. of panels- usually 2-5 in a series "string". You
then clone these sets until all panels are gone. Of
course, you'd buy the right amount of panels so that you
have full sets. The total voltage of these individual sets
have to be at least 50% more than the battery bank voltage
to a maximum of about 20% less than the charge controller
maximum input voltage. You HAVE to be 50% higher than the
battery bank, but that's easy because individual panels
are now normally 29 Volts. If you need to get further from
the batteries and CC to get full sun, you should go to a
higher voltage. The higher the voltage, the less loss in
the run to the batteries.
You will have to buy MC connector jumper cables or
adapters to configure the panels correctly. Ask your
dealer exactly which you'll need. they are "genedered" for
plus and minus, so wiring sets in parallel requires cable
adapters or soldering. It's fairly complex. I show you all
the normal wiring situations in the video.
You should run the output of the panel array down to a dis-connect
box at the mounting stand's base. This can be a typical AC
disconnect. You may use flexible blue conduit or grey
electrical PVC for the run from array to box. This allows
you to dis-connect the array from the other equipment when
you are working on it.
Another AC dis-connect box is
used at the input to the battery box. This is a good place
to install a Lightening arrestor. (also all covered in the
Remember, panels CANNOT be
turned off when in the sun. You should NOT connect the
connectors together while they are in full sun. This will
cause a spark and damage the metal inside the connectors.
Do your wiring in the evening.. at sundown. You can also
cover them all with cardboard. You only do the connections
Note: When the sun comes back out from behind a cloud,
there is a temporary magnification effect while it
emerges. This can result in a short-term rise in voltage
and current from your system. You will see this on your
charge controller meter when it happens. This is why you
leave a little "headroom" in the voltage your panels are
wired up to provide - so as to not exceed the maximum
voltage input specification of the charge controller. The
charge controller (MPPT) will convert all the extra
voltage from the panels into charging current at the
desired battery bank voltage you are configured for. You
set the charge controller for the battery bank voltage
you've chosen- with either jumpers or selections on a
menu- depending on your brand/type.
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Lead-Acid deep-cycle batteries
require maintenance. Batteries with liquid electrolyte
(sulfuric acid) require
filling periodically... just like a car battery does. The
more you charge and discharge them, the more they need to
be topped-off. You check the acid level by removing the
battery's caps and visually checking the level.
You need to have safety glasses on. You might as well use
rubber gloves. Some people are more sensitive to sulfuric
acid than others. You will be topping-off the batteries
with distilled water. Never add battery acid.
NEVER let the electrolyte get below the tops of the actual
battery lead plates. Use a plastic funnel to fill the
battery cells. DO NOT wear metal jewelry or a watch when
doing this. Also, the acid will eat through cotton
clothes. Wear old clothes. Slowly fill each cell to about
3/4 inch from the top. Do not fill them all the way to the
top. Acid will bubble out during charging. If you see your
charge controller voltage go up to 15V or more when
charging, it is a good indicator that your batteries are
low. Don't let it get to this stage. Check them every few
Wipe off any spilled acid
or water on the battery tops with a disposable cloth. You
should also consider spraying anti-corrosion spray on the
battery terminals. An old trick is to put two shiny
pennies near the terminal. These will draw off any
corrosion and can be replaced when shot. There are also
treated red and green anti-corrosion disks that you can
buy and they go under the terminals.
Once a year, check
tightness of all connections... they loosen up sometimes.
Put electrical tape over all your tool handles so they
cannot short the batteries out if you drop them.
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solar panel array needs to be as perpendicular the the sun
as possible. There are two paths involved.
First is that the sun's path across the sky changes from
season to season. The second is that the sun moves from
east to west during the day.
Your panel array needs to be adjustable for seasonal
change. The sun's path is nearly overhead in Summer in
North America and quite a bit lower in Winter. Thus, we
are talking about the panel's angle to the horizon.
You can do these seasonal adjustments a few times a year.
The more you do them, the more energy you will make.
Really, twice a year is fine. This is because the panels
have a coating on them that captures off-axis light well.
In Summer in the northern hemisphere, your panels will be
almost horizontal in southern latitudes and somewhat less
than that as you move north. If you are roof mounting
panels and cannot adjust them, you should position them
for the Winter sun angle. Winter has fewer hours of
sunlight and you are indoors more using more energy... so
favor the Winter. The course teaches you exactly how to
mount and adjust them for your location.
As far as tracking for the
sun's daily movement, you can buy tracking mounts, but
since the panels are so good at making energy from
off-axis light, the payback period for the extra cost of
the trackers is too long in my opinion. I opt for fixed
mount panels. You do want to mount the panel array so that
it is due south.
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If you are wondering about the economics of building a
solar system, read my page on that.
This is about the cost break-down when building.
When you are designing your system, you may be coming at
it from three possible positions:
1. You have an un-limited
budget and want to make ALL your current power needs with
2. You have a budget limit and want to make as much power
as you can inside that budget.
3. You want to power a specific set of appliances or a
cabin (small system design).
In each situation, you will
be spending about 50% on your panels themselves, 10% on
the Inverter, 5% on the charge controller, 25% on
batteries and 10% on the hardware and wire. As panel
prices drop (they are), you'll spend a slightly lower
percent of the money on the panels themselves.
If you have an unlimited
budget, know that to generate 1KWH of power a month, it
takes 6 watts of solar panels (with 5 hours of sun a day).
Check your electric bill and multiply by 6. Then look
online for package deals on equipment at that level. With
the limited budget, take 50% of your money and see how
many panels you can get. Shop for best price and name
brand. Then talk to the vendors about the rest of the
stuff you'll need. They will be super-happy to configure
all the parts required - inside your budget.
If you are making a small system for a cabin or dedicated
application, you'll need to do an energy budget.
The videos tell you exactly how to make this calculation.
It's not difficult but beyond the scope of this lesson.
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I hope this gave you some real insight into the process of
building your own system. My goal is to get you to the
level where you'll understand all the concepts involved
and how they are applied in the field. If you can handle
small tools comfortably and could build a small backyard
project, you can absolutely do this. Start with a
small system and add to it later. I often build small
systems just for emergency power or powering refrigerators
/ freezers in power outages. The full course gives
you all the skills required to build a system of any size.
Best of luck with your solar projects!
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