Hi.
I'm Amy Beaudet from the altE Store.
Thank you for watching our video series.
This third video is called Solar Electric Components , and we're going to break it down
into multiple parts to keep it manageable.
If you missed our earlier videos, I recommend you go back and watch the earlier ones in
the series to get a good foundation.We re-going to go over some of main components in a solar
electric system; the solar modules, batteries.
Keep in mind that technology is moving forward at an incredible rate, so I'm going to make
some generalities that are true today, but there are likely to be exceptions to most
rules discussed.Before we go further, I want to go over a quick reminder on wiring in series
vs parallel.
Wiring panels in series, where the negative of one is wire to the positive of the other,
results in the current staying the same, but the voltage increases.
Two panels in parallel, where the two positives are wired together and the two negatives are
wired together, results in the voltage staying the same and current increasing.
It s important to note that regardless of the way it is wired, the power, or watts,
remains the same.
Since watts equals volts x amps, it doesn't matter if it is series or parallel.
Likewise, when batteries are wired in series, their voltage increases, and when wired in
parallel, amp hours are increased.
You'll often see multiple rows of panels or batteries wired in series, each row is a string.
You can then wire multiple strings in parallel.
This allows you to get both higher voltage (with series strings) and higher amps or amp
hours (with parallel).
In this example of 2 parallel rows of 4 batteries wired in series is called 2 strings of 4.
You can see that wiring (4) 12V batteries in series equals 48V, and wiring those 2 strings
in parallel doubles the amp hours to 160ah.
The power of this array is 160ah x 48V, which equals 7680 watt hours.Let's start with the
solar panels, or PV Modules.
Solar panels generate DC electricity when exposed to sunlight via the Photovoltaic Effect,
first observed by a French physicist in 1839.
A simple explanation is that the photons from sunlight are absorbed by a semiconductor material,
generally silicon.
The negatively charged electrons are knocked loose from their atoms, and flow from the
negative side to the positive side to recombine with available holes there.
This creates a direct current flow.
This flow of electrons can then be used to either directly power a DC device, like a
pump or a fan, it can be used to charge a battery bank, or it can be inverted to AC
power to use in your home.Each solar cell generates about 1/2V.
That's not much for practical use.
So multiple cells are wired together in series to create higher voltage, creating a solar
module, commonly referred to as a solar panel.
A typical 12V solar panel has 36 cells in series.
The larger a solar cell is, the higher the current.
So the cells of a 200W panel are generally bigger than a 100W panel.
Multiple solar modules wired together then creates a solar array.
You can see the difference in the look of a 12V module compared to a 24V module.
As with anything, there are exceptions.
We do have some 12V modules that have 72 cells, but the cells are wired in 2 parallel strings
of 36 in series, creating the 12V.Each module has a label on the back, stating their specs.
Here s an example of a Kyocera 140W 12V module.
It lists the rated outputs for the panel, as well as any certification it has.
The ratings are actual outputs under standard test conditions, so the numbers you measure
in the real world may be slightly different.
Let s go over each of the specs for a solar module.Open Circuit Voltage is the voltage
you will measure when nothing but a voltmeter is connected to the solar panel.
This is the highest voltage the module will output at 77 degrees Fahrenheit with the sunlight
intensity at 1000 watts per square meter, which are just a few of the details of standard
test conditions, or STC.
The voltage will be higher when it is colder out, and lower when it is hotter.
Short Circuit Current is the amps output with no load on the panel.
It is the highest current possible at STC.
There are times when the output could be higher, for instance when the sun is coming out from
behind a cloud, you can see the silver lining , where the edge of the cloud is magnifying
the sunlight, causing the intensity to be brighter than STC.
This brings us to the two specs which are when the module is connected to a load, so
more real world conditions.
But still at the temperature and brightness listed under STC.
Maximum Power Voltage is the actual voltage the module will output when connected, and
Maximum Power Current is the amps output while under load.PV modules were originally designed
to charge battery systems, so it is typical to see panels listed for what voltage battery
bank it is able to charge.
Nominal voltage is a shorthand grouping term, originally based on battery voltages (for
example, 12V, 24V, 48V).
To charge a 48V battery bank, you simply wire four 12V modules or 2 24V modules in series
to add up to 48V.
In general, you can determine what nominal voltage the module is by the number of cells
on the panel.
A 12V nominal panel usually has 36 cells, and its Open Circuit voltage is about 22 volts,
and its Maximum Power voltage is around 17 volts.
However, as grid-tied solar systems that don't use batteries have become more popular, you
start to see different size nominal panels that don t logically line up with battery
bank sizes.
The most popular size modules used in grid-tied systems today are 60 cell, 20V modules.
The wattage of available panels has been increasing, and many manufactures are achieving that by
increasing the number of cells, increasing the voltage of the panels.
As you recall, watts equals volts times amps, so increasing the volts while maintaining
the same amps increases the watts.
As such, there are 80 cells and higher available these days.Let s move off PV modules onto
batteries.
Solar panels have no way to store power, you use it or lose it.
Batteries allow you to store power to use later, by using the power generated by the
module or other power source to charge the batteries.
Batteries used in a solar system MUST be deep cycle batteries.
These are made very differently from car batteries.
A car battery has the internal plates designed to send a short, high current blast to start
the engine.
It then gets recharged quickly by the alternator to send another short blast hours later.
A deep cycle battery is designed differently.
It is designed to be gradually charged and discharged over a course of hours.
If you try to use a car battery for an off-grid system, it will work for a short amount of
time, but you will very quickly kill the batteries.
PV systems can have many batteries, each of them can weigh 50, 100 pounds, or much more.
Additionally, there are losses inherent in batteries as they convert electrical energy
to chemical and back to electrical: 5-15% of energy lost to storage and extraction.
Additionally, you should never use more than 50% of the rated capacity, or you will quickly
reduce the battery s ability to hold a charge, and have to replace the bank.
These losses need to be taken into account when calculating the size of your battery
bank.
When selecting
a battery for your system, there are 2 primary types of batteries available, flooded or sealed.
A flooded lead acid battery has removable vents that you must remove to check the specific
gravity of the acid and add water on a regular schedule, usually once a month.
Because it is not sealed, it is designed to output the hydrogen gas that is created during
its charging process.
Therefore the battery bank MUST be properly vented to the outside.
If you are looking to have flooded batteries shipped, be aware that they are considered
hazardous material by the Department of Transportation, so additional precautions and expenses may
be required.
The advantage of these flooded batteries is that they are less expensive than a typical
sealed battery, and a well maintained flooded battery will generally last longer than a
typical sealed battery.
But if you neglect the battery and do not handle the maintenance, you will quickly have
a dead battery bank on you hands.
Sealed Lead Acid batteries are most commonly available as either AGM or Gel.
This refers to the form of the electrolyte.
An AGM battery has the electrolyte in a spongey mat, and the gel batteries have a thicker
gel that keeps itself distributed within the battery.
There are pros and cons to each of these designs that we won t get into, but in general , both
types of sealed batteries are very similar.
The biggest pro of sealed batteries is that since they are sealed, they won't spill or
outgas.
This makes it a safer option than flooded batteries.
They also don t require the monthly maintenance, just occasionally inspect them to see that
they look to be in good shape.
Sealed batteries are an excellent choice for battery backup systems that aren't charged
and discharged every day, but require a long standby period.
They also do better in extreme cold.
The downside to the sealed batteries is that they tend to be more expensive than a flooded
battery, and have a shorter life than a well maintained flooded battery.
But it you are not able or willing to maintain a flooded battery, sealed is definitely the
way to go.
Just as Watts = Volts x Amps, Watt hours = Volts x Amp hours.
This will come in handy when we size our battery bank.
Many people ask how long they can run things from a battery.
This depends on how deeply you discharge the battery, known as depth of discharge, and
how quickly you are drawing current out of the battery.
If you are drawing 2 amps out of a battery for 4 hours, this is using 8 amp-hours.
As I mentioned before, you don t want to use more than of the stored power in a battery,
so the most power you want to take out of a 92 amp hour battery is 46ah.
So if you are running that same 2 amps for 23 hours, you would have drained the 92 ah
battery to 50% depth of discharge.
The amount of power that a battery can store varies based on a number of variables, including
how fast you charge and discharge the battery.
In this example, you see that if you charge and/or discharge the battery over 5 hours
and a rate of 49 amps, it can store half the power than if you did the same over the course
of 100 hours at 4.6A. Most batteries are rated at 20 hours, basically how much power you
can use during a day.
If you are using power faster or slower than 20 hours, you must adjust the sizing accordingly.
The amount of power that a battery can store varies based on a number of variables, including
how fast you charge and discharge the battery.
In this example, you see that if you charge and/or discharge the battery over 5 hours
and a rate of 49 amps, it can store half the power than if you did the same over the course
of 100 hours at 4.6A. Most batteries are rated at 20 hours, basically how much power you
can use during a day.
If you are using power faster or slower than 20 hours, you must adjust the sizing accordingly.When
selecting a battery, you must decide between flooded or sealed, what voltage battery, and
how many amp hours.
You need to keep in mind the size and weight of the batteries, will they fit in your available
space?
Also note what terminals they have to connect the battery cables.Check out our website for
a great selection of solar panels and deep cycle batteries available.
Also watch more of our Video Series on our web site, including part 2 where we cover
charge controllers and inverters.
We've got a team of highly trained Technical Sales Reps available to help you plan your
system, give us a call.And please check out our website, altestore.com, where we are making
renewable, do-able.