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All About Solar Panels

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With an industry-standard power output warranty of 25 years, solar panels are a good investment for a business or homeowner working with renewable energy. 

Solar panels, also known as solar modules, capture the sun’s energy before converting it to electricity. Though the technology is advanced, the modules are simple. Using refined silica with the addition of sunlight, we can generate direct current (DC) power. 

It’s important to understand a few pieces of information before purchasing a solar panel. We encourage you to spend a few minutes reading about a solar panel’s specifications below and what they each mean.

The spec sheet of a solar module and what it all means:

All reputable brands of solar modules will have a label on the backplate that lists the information explained on this page. One point to remember is that the specifications of a solar module are determined in a lab under laboratory conditions. Output and performance can vary dramatically in the field depending on irradiance (power of the sun) and temperature.

Maximum Power or Peak Power (Pmax) in watts:

Maximum power (or peak power) is the total power output the module is capable of producing. The Pmax is measured in watts

Open Circuit Voltage (Vmp) in Volts:

Measured in volts, the voltage at maximum power is the module’s voltage when the energy output is the greatest.  When using solar direct appliances or battery charging without a maximum power point tracking (MPPT) charge controller, matching your Vmp to your load or battery bank is essential.

Open Circuit Voltage (Voc) in Volts:

Open circuit voltage is the solar module’s maximum output when connected to an open circuit (i.e., no electrical load is on the circuit). Voc is measured in volts. We use this number to design our module strings to ensure we do not over-voltage our charge controllers, inverters, or solar direct appliances. 

When using this number, it is important to know that Voc increases when temperatures decrease. Be sure to take into account the lowest outdoor temperature when sizing solar modules or strings of modules.

Short Circuit Current (Isc) in amps:

Measured in amps, the short circuit current is the total amps capable of flowing from the solar array under a direct shorted circuit. It is important to size your wire to carry the Isc of your solar array in case of an electrical short.

Max Power Current (Imp or Impp) in Amps:

The maximum power current is the amperage that comes off the module when operating at the Vmp. This number tells us the current coming off the solar module under normal maximum power operation.

For applications that are not using an MPPT charge controller or a
grid tied inverter:

When using solar modules for solar direct applications or for charging batteries with a pulse-width modulation (PWM) controller, you must understand the voltage at which the module operates and choose a module that has a Vmp that works well with your intended use.

For example, when charging a 12 VDC battery bank using a PWM controller, you must choose a solar module with a Vmp of 17 to 20 VDC.

Note: If you have any questions regarding what solar module will work for what application, don’t hesitate to contact Greenwired’s sales staff. We will help you find the best solar panel that will work for you.