Photovoltaic Electric Principles

Explain how a solar cell converts sunlight into electric power

➔This is known as the photovoltaic effect.

➔No “moving parts,” non-mechanical

➔ The current produced is DC (Direct Current) and is then converted by an inverter to AC
(Alternating Current) power.

➔This can happen with various materials, but crystalline silicon is most popular and economical.

➔ Silicon cells are made by adding impurities, this process is known as ‘doping’, which increases
Silicon’s ability to allow electric flow.

➔P-type material has positive charge

➔ N-type material is a semiconductor that has free electrons, or negatively charged

➔The region between the two differently charged materials is known as the p-n junction,
➔Photons (from sunlight) striking a PV cell give electrons the energy to move freely, which
induces the flow of electrical current.

➔The electrons move from the negatively charged material to the positively charged material
creating a build up of voltage in the p-n junction

➔The cells are wired together in a series string between cells to build the voltage up in the
panel/module.

Solar Cells

➔ Limited voltage to about 0.5 volts per cell (this is the Voc of the cell)

➔ Cells are place in a module in a series only and in a series/parallel configuration to get
the desired module voltage (12V, 24V, 48V) and current characteristics. Current
characteristics would depend on how many series strings are wired in parallel together,
i.e. increasing the amps/current.

➔Cells are typically sorted by grade and electrical properties to be used in different
qualities of modules.

➔The maximum Isc is dependent on the type of cell and surface area.

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