Photovoltaic module solar panel location and positioning

electricity from the sun by John Drake II | home

Proper location and set up of photovoltaics modules is

paramount to getting the most wattage from your system.

Location:

Try to locate you solar panels as close to the battery(s)

as possible.

This will reduce the voltage loss which is incurred when

using long wire runs.

If you cannot mount the modules close to the batteries

you have two options.

The first, and nowadays the most expensive, is to use

very heavy wire to minimize voltage drop.

The following link will take you to our page showing wire

gauge recommendations for the incoming wires from

your photovoltaic modules:

Wire loss - Voltage drop charts

Another option would be to wire your modules in series

or series/parallel to increase the output voltage.

Then you would use a Maximum Power Point Tracking

charge controller to bring down the incoming voltage to

the charging voltage of your system.

Many years ago a customer called about a system they

installed for the U.S.G.S. in Nevada.

They said the batteries were not charging, even in full

sun.

The photovoltaic array was about two hundred feet from

a bore hole and the battery bank was about one hundred

feet below the surface along with the seismic monitoring

equipment.

We recommended that they re-wire the photovoltaic array

in series/parallel and put an MPPT charge controller next

to the batteries.

Yup, it worked.

Another very important concern is shading of the solar

panels.

A number of years ago I was re-working a system that

someone else had installed in a commercial nursery.

I asked folks to move some trees in planters away from

the system.

Much of the day the trees cast shadows on the pv modules.

The customer did not think that would make a big difference.

The trees were moved and I put a clamp-on amp meter on

the array output cable.

While he was watching the display on the meter I tossed a

business card on one of the panels.

That took care of convincing him.

One of our systems, 48 volt, will have three sets of arrays.

Each set will consist of four Evergreen 115 watt ribbon

crystal panels.

The four panels will be wired in series in a combiner box

on the roof for a nominal array voltage of 48 volts.

As of today, I have one of the arrays up and running - I hope

to finish this system before I need a walker.

Each array will have its own charge controller.

The first array gets good sunshine throughout the year.

The other two will have some shading in the winter due to

trees on the parkway which can not be removed.

This way the battery bank will get the most power available

year long.

Direction:

Whenever possible, have your panels facing True South.

If you have a pole or ground mount this is much easier

than with a roof mount installation.

You can use a compass along with a map of your area

showing the degrees of declination for your area.

This will allow you to take the compass reading and adjust

for the difference between Magnetic South, which your

compass shows and True South.

The closer your panels face to True South, the more power

they will produce.

Panel Angle Tilt :

The angle of your photovoltaic modules have a definite

effect on power output.

In a perfect world they would always be perpendicular to

the sun - directly facing the sun.

As the seasons change the sun is higher in the horizon

in the summer than in the winter.

The ideal set up is one where you can change the tilt

angle of your panels throughout the year - lower in the

winter than in the summer.

On a roof mount installation this is not practical.

However on a ground or pole mount, this can make a

great deal of difference in the power output of the system.

Most pole mount systems allow "seasonal adjustments"

to the angle of your array.

Some ground mount setups have a notched or slotted

base which allow the rear vertical members to slide back

and forth changing the tilt of the panels.

On a fixed angle array the old rule of thumb is to take

your latitude and add fifteen degrees to it for the angle

of your array.

This is a sorta of happy medium for use throughout the

year.

There is a simple way for aiming your panels.

This also works well for making seasonal adjustments.

Take a flat piece of metal or plastic and attach it to one

of the panel frames or the mounting rack.

Have it so it runs parallel to the panel.

Put a screw or pin in it perpendicular to the face of the

panels.

This way, when the rack is moved it will cast a shadow.

Around noon, adjust the array so the shadow dissapears -

then your panels will be facing directly towards the sun.

A note regarding recreational vehicles.

I have heard people say that having pv panels flat on the

roof is the best of all worlds.

Well, I have a full head of hair, no aches or pains and am

twenty years old.

Do not believe any of the above.

A flat mounted panel will never get near its rated output

unless the sun is directly overhead.

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