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How to Figure Solar Panel Output
The usable power from the sun depends on many thing such as weather
conditions, time of year and latitude. When determining
how to figure solar
panel output, there are other inefficiencies that should be taken
into account. This will help you to decide whether solar
power is a good option for powering your home. Whether you want
complete solar home heating or
are only looking for a smaller system such as solar
water heating, it's useful to know what affects solar panel output.
How Much Energy Comes From the Sun?
More solar energy is delivered to earth in one day then all
energy produced by humans in one year. Most energy from the sun
is absorbed by the oceans and land to drive the wind, water and
Factors that Affect Solar Panel Output
Solar panels are a collection of solar cells
connected together to create a panel that's rated according to power output.
Larger panels have more solar cells than smaller panels, and therefore
produce more current and power. However, inefficiencies in and around
the system will reduce this rated power quite drastically. For instance:
- Bright sunshine on a clear day will produce more power than on an
overcast day. Commonly known as the intensity of solar radiation, a
panel can output its rated power when the sunshine is at its brightest.
Clouds can reduce the power output by 70-80%. Snow and leaves can
completely halt the panels from producing any power.
- Solar panels must be kept clear of dust and debris. A layer of dust
on the panel may reduce the output power by up to 30%, even in bright
- The sun's rays are more intense in the summer than in the winter.
The lower solar intensity and the shorter number of daylight hours
during the winter months will reduce the power production.
- The time of day also affects the efficiency of the panels. When
the sun is at its highest point, the rays are most direct to the
earth and the panels produce the most power.
- The length of wire from the panel to the batteries also makes
a difference. The longer the wire, the more resistance will be
present in the electrical circuit which results in less power
being sent to the batteries. Use the appropriate gauge wire for
the peak amount of current expected from the panels. All wires
should be as short as possible.
- Select a charge controller with maximum power point tracking
(MPPT). This device adjusts the voltage and current from the PV
cell and will extract the maximum amount of power.
Solar Panel Output
The amount of power a solar panel can generate depends on the
voltage and current. For these devices, the voltage doesn't vary
much (10 V 16V), but the current increases with more solar cells.
Power is calculated by multiplying the voltage by the current,
ie. power = voltage * current. So the more solar panels
you have, the more current your system generates, and therefore
provides more energy for your home.