Solar PV Basics

Solar PV basics

Energy One Ltd

By Mathy Mpassy Isinki

Off Grid Energy Solutions Business andTechnical Sales Professional

Heat andlight

The sun delivers its energy in two mainforms:

Solar electric systems convertthe sun’s light energy intoelectricity using photovoltaiccells.

Grid connected (or grid tied) and Off grid (or stand alone)

Types of PV systems:

Grid connected solar PV systems exportexcess energy to the grid;

Off grid solar PV systems store excessenergy into batteries.

Grid connected solar PV systemsbenefit from grid's energy while;Off grid solar PV systems benefit fromenergy stored into batteries.

When the sun is not available:

Photovoltaic (PV) cells are made oflight sensitive semiconductor materialsusing photons to dislodge electrons anddrive an electric current.

Mono-crystalline silicon;Poly- crystalline;Thin films

There are three main type of PV cellstechnology in use:

Crystalline silicon is made from ultrapure silicon material such as the one usedfor semiconductor chips;

Thin films is made by depositing layers ofsemiconductors material onto glass orstainless steel substrate.

Mono-crystalline silicon: 12.5-15%Poly-crystalline silicon: 11-14%Copper Indium Gallium Selenide (CIGS): 10-13%Cadmium Telluride (CdTe): 9-12%Amorphous Silicon (a-Si): 5-7%

Solar cells conversion efficiency:

Crystalline silicon: -0.4 to -0.5CIGS: -0.32 to -0.36CdTe: -0.25a-Si: -0.21

Solar cells temperature coefficient:

Effect of temperature:

PV cells performance declines astemperature rises

Solar PV modules are made of theaggregation of solar cells.

Solar power terms:

Pmax: The maximum power a solarmodule can produce.Vpmax: The voltage at whichmaximum power is produced.Ipmax: The current at which maximumpower is produced.

Voc: The maximum possible voltageacross the solar module when current iszero.Isc: The maximum possible currentflowing through the solar panel whenno load is connected and voltage iszero.

Standard Test Conditions (STC):

Temperature of the cell – 25°C.Solar Irradiance – 1000 Watts persquare meter.

PV modules are connected in series into PVstrings;

PV arrays are formed by the parallelaggregation of PV strings.

Cables that can withstand environmentalconditions are used to interconnect PVstrings and arrays.

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