6. PV Modules

Technical Terms related to PV Modules

Isc

Short circuit current - will be considered to size the conductor

Imp

Maximum Power current - or the maximum current produced by the PV module
varies based on intensity of the sunlight striking on the module

Voc

Open circuit voltage - need to determine the maximum system voltage - voltage value in the absence of current value - while connecting in parallel this voltage will be considered

Vmp

Maximum Power Voltage - This voltage drops while the temperature increases - Operating voltage of the cell, this value is related to the current value of the 

Mpp

Max power point ( Vmp x Imp)
Used to size the system


Change in Voltage based on temperature
Change in Current based on Irradiance

Solar PV Cell Production

Solar Cell is bacically a semi-conductor  *  In presence of Solar light that will become a conductor

Silicon is the major element used for manufacturing the Solar PV Cell. Silicon is basically an insulator. while manufacturing the cells, silicon gas goes through the doping process.Boron and Phosphorous used in dopping process.

Boron introduces in the first process,Phosphorous induces to manufacturing cell

Negative - Phosphorous - Extra Electrons

Positive   - Boron           - Extra Holes
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              Types of Modules
     ___________________I________________
          I                                             I                                     I
Crystalline                          Hetero-Junction                      Thin Film
          I                                                                                   l
Mono crystalline                                                                                 Amorphous core
Multi Crystalline                                                                 Cadmium Telluride


Crystalline
Most commonly used type of module
More Efficiency from 11 to 14W/SqFt.



Mono crystalline
Uniform molecular structure
More Efficient
Multi Crystalline 
Many structure
Less Efficient


Irradiance - Intensity of radiation striking the earth considered in W/Sqm or kW/Sqm

Power per Unit area will be depends on:-

• Location of module related to sun
• Time of the year
• weather condition

Edge of Cloud Effect
Cloud pass over PV Array and prevents the sun from striking the array

W/Sqm and time curve
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*
*

• The Solar PV Modules are designed for constant output voltage and varying current, depends on the irradiance.
• As soon as the ambient light will fall on the Module, the voltage is produced between the terminals.
• Standard Test condition (STC) Irradiance value is 1000W/Sqm.
• Pyronometer is used to measure the irradiance value.
• Irradiance value will be indicated as kWH/Sqmtr.
• PV Designer will calculate the value based on day month and year of irradiation

Pyronometer

Consider peak sun hour @ 4Hr

850w/SqM x 4 Hrs = 3400W/SqM

Dividing the value by one peak sun

                          3400W/SqM/Day        =   3.4Hrs/Day
                            1000w/SqM

Reference Material
Fundamental understanding of irradiance value based on location and time can be refer from NREL Website - "rredc.nrel.gov/solar/pubs/redbook"

NREL Redbook