A Brief Solar Introduction
We will attempt to explain the principles behind solar energy (solar
power, photovoltaic’s) in simple terms without putting you to sleep. I
think we can all understand that the sun heats things up. One of the
earliest uses of this solar energy was the creation of a solar shower—A
large enclosed (often black painted) metal bucket filled with water set
upon a roof top. The sun would heat the water and provide hot to warm
showers, at least for the first person cleaning up for the day
متن کامل انگلیسی و ترجمه فارسی در ادامه مطلب
The sun heats things up because sunlight is made up of small particles
of energy called photons (a basic “unit” of light and all other forms of
electromagnetic radiation). These photons are absorbed by objects and
create heat. The heat is the result of electrons in the object moving
around really fast. Think of a bridge in winter and summer. During the
winter the small gaps in the road surface are larger than in the summer.
The electrons are “cold” in the winter when there is not as much
sunlight and stick closer together or contract. In the summer they are
“hot” and expand to get away from each other.
Solar Energy Applied to a Solar Panel [top]
Solar panels are made from a material called silicon. When the solar
energy (the photon) is absorbed they dislodge electrons from the
negatively charged side of the solar (photovoltaic) panel to the
positively charged side. An entire tutorial could be written outlining
the makeup of silicon “doped” with phosphorous and boron which creates
the +/- charged silicon, but for simplicity understand that heated-up
electrons “run around” in search of a “place to rest.” As these
electrons move freely about the electric field (created by photons
hitting the negatively charged silicon that is in contact with the
positively charged silicon), they create current. In between the
positive and negative sides is the electric field or diode that permits
one way traffic flow from negative to positive. The electric field
creates the voltage. Harnessing this voltage by providing a path for
this current to flow freely from the positive side back to the negative
side is how we get power.
Solar Energy – Creating Your System
Solar power is a wonderful use of “free” energy. But if you use it
incorrectly you could damage sensitive electronics such as laptop
computers. It is prudent that you select the right materials and
location to satisfy the requirements for your solar powered system.
Your Basic Solar Needs [top]
The obvious place to start is with the sun! When creating a solar
system think about how much sunlight will come in contact with the solar
cells. If you are creating a permanent location consider where shadows
fall, as this will reduce or eliminate the current provided by the solar
panel. Also, consider geographic and weather related obstacles such as
your latitude, fog, the number of cloudy days, and winter snows. If your
system is portable you need only find the sunniest location to deploy
your solar panel. To create optimal performance you need to consider the
tilt and angle orientation of the solar panels. Solar panels should
always face true south in the Northern Hemisphere, and North in the
Southern Hemisphere. A good rule of thumb is to tilt your panel, from
horizontal, your latitude plus 15o in winter and minus 15o in the
summer. There are many online resources that can help in determining the
best positioning of your solar photovoltaic panels and we encourage you
to look at them.
Selecting the appropriate size solar panel is the next consideration.
There are many variables to consider, including the amount of sunlight
hours, power requirement of your system, and the total hours the system
will be in use per day. The power wheel to the right is not meant to
scare you or have your eyes gloss over. It simply illustrates the
relationship between power (watts), voltage (volts), current (amps), and
How to Calculate and Convert [top]
To calculate this information we suggest you use a solar calculator.
The basic idea is to convert your AC current usage to DC current usage
and then into watts.
• First, you need to convert AC amps to DC amps. Remember this ratio
for converting AC 120V amp units to DC 12V amp units: 1 amp = 10 amps
(for example if your laptop adapter indicates it uses 1.7 input AC amps
per hour that is equal to 17 DC input amps every hour).
• Second, you need to multiply that number by 12 volts to determine the
total watts per hour (in our example 17Ah x 12V = 204 watts).
• The third step is to resolve how many hours the application will be
in use. Multiply the total watts/hr by the total number of hours the
device will be in use per day (for our example let’s use 2 hrs x 204W =
408 watts per day).
• The fourth aspect to consider is the amount of sun hours available to
recharge your batteries. Do you need to have your system keep up with
24/7 use or is there a period of down time between uses? The average sun
hours available during a day are 5 depending on season and latitude.
At 12 volts this tells us for our example to “break even” under perfect
solar conditions we need a solar array that can create a minimum of
408W or 34 DC amps per day. Not accounting for imperfect light
conditions, resistance and any conversion loss this example would
require a solar panel around 110 watts minimum. For applications running
for longer periods of time (permanent) you will also have to calculate
for solar loss, conversion loss, and the size of battery bank needed to
bridge the gap.
NOTE: Most laptops come with DC adapters which are much more efficient
at converting to your laptops DC voltage than from the AC adapter. In
this same example the DC adapter allows the DC input amps to be about
5.5Ah as the laptop uses 65W at 18.5V. That is a far cry from the DC
17Ah required using the AC adapter! To run the laptop for this length of
time you would require at least a 30W panel.
The Next Step
Now that you have an idea of how large a solar panel you require you
can continue to create your solar powered system. There are at least two
more major items you will need and most likely three as well as other
The Solar Controller [top]
The first item is a solar controller. The solar charge controller
regulates the raw voltage produced by the solar panel to a safe level
for the battery bank and then “shuts off” the supply of energy to the
batteries when they are at full charge. The solar panel has no “brain”
to tell it to stop producing electricity—when it is in the sun it will
produce power regardless the need. A large 12 volt panel can produce a
little over 30V at peak operation while smaller panels produce around
18V which is still too high for 12 volt batteries. Without the charge
controller your batteries will be destroyed in short order. It is
recommended that any solar panel over 5 watts have a charge controller
(If you are using small batteries with a panel less than 5 watts you may
also require a controller).
The Battery Bank [top]
So what type of battery is best and how many batteries will you need?
Good question. Every situation is different, but generally speaking you
want to use Deep Cycle Batteries. We prefer AGM maintenance free
batteries over flooded batteries. Maintenance free batteries are sealed
and can be placed into service on their side in a closed unventilated
environment. With sealed AGM batteries you will not have to check the
electrolyte level monthly as you do with the flooded type, which will
save you time and the hassle of adding distilled water and spilling
acid. AGM batteries are generally a little more expensive than the
flooded type, but typically last a longer.
In regards to the number of batteries required this is dependent on the
load applied to the battery bank. We recommend the total amp capacity
of the battery bank be at least twice the draw. Batteries will last a
long time when they are discharged to around 50% and then immediately
brought back to full charge. Deep cycle batteries are capable of
discharging much further, but it is not recommended to do this
frequently. An often overlooked calculation in regards to the size of
battery banks is the number of days the system may be without the
ability to replenish its power—think fog, rain, and snow. You will need
to know how many amps are being used each day under such circumstances
and double the number. For example, if the fog lasts 3 days and your
application requires 50 DC amps per day then you should have at least
300Ah extra capacity beyond your normal system requirements of around
The Inverter [top]
Many solar systems require an inverter or converter to change the
incoming DC voltage to a preferred DC or AC voltage. When selecting an
inverter one of the first questions you should have answered is: What
will be the maximum surge and for how long? When an appliance is first
plugged in it will draw a higher amount of watts for so many seconds
before dropping back to a continuous load. Your inverter needs to be
able to handle the peak watt-hour demand created by the appliance(s)
connected into the inverter. The second consideration is that the
inverter itself will use up some of the systems power to convert the
voltage. It may cost a little more to purchase an efficient inverter,
but in the long run the energy saving will be worth the money spent. A
final consideration is the type of device plugged into the system. A
pure sine wave inverter is best for sensitive electronics such as
The Fundamental Differences Between Types of Solar Panels
Amorphous Solar Technology
Color: black to dark brown in color.
These panels have the widest light spectrum absorption levels. They can
produce current in poor light conditions or earlier and later into the
lunar day. This means while other solar technologies have no output at
all the amorphous panel will have output during these low light
situations. The amorphous panels are typically larger in size when
compared with panels of similar wattage, but are also far less
expensive. These panels are great for low wattage maintenance situations
for keeping batteries in your car, motorcycle, SUV, truck, RV, boat and
tractor in a fully charged state.
Polycrystalline Solar Technology
Color: Shades of dark to light blue.
The polycrystalline panel works best in direct sunlight with proper
south facing installation (in the northern hemisphere). They will
produce 2-3 times more power than a similarly sized amorphous panel
making then far more efficient. Polycrystalline solar panels are ideal
for high wattage installations or where physical space is limited.
Monocrystalline Solar Technology
Color: Shades of dark to light blue.
Similar to polycrystalline units, but different in that each module is
made from a single silicon crystal, and is more efficient, though more
expensive, than the newer and cheaper polycrystalline types. These
panels will last 25-50 years.
Cadmium Indium Gallium Selinide (CIGS) Solar Technology
Color: Greenish brown to black in color.
CIGS solar panels combine the technologies listed above. Like the
amorphous panels, they work well in low light situations and are
efficient like the polycrystalline panels in direct sunlight. These are
most often used in thin film or flexible solar cells.
This solar energy tutorial provided by Impact Battery is intended to be
a brief guide to understanding solar power. Please also consult other
sources to make an informed decision.