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You can answer to the guestions either in English or in Finnish Seppo Valkealahti

EE.REF.310, Solar Power Systems
Examination, 5.5.2023

a)
b)

c)

a)

1)
e)

b)

Fxtra-terrestrial solar irradiance on the Earth varies annually from 1322 to 1414 W/m?. Why
does it vary?

How and why does the solar irradiance on a plane perpendicular to the coming irradiance at
the ground level vary on a sunny day?

How can you estimate (calculate) the solar irradiance on the earth surface during a clear sky
day?

What are the valenee and conduction band structures in commercially available
semiconductor based solar PV cells (Si and thin film cells)?

How is the energy of solar radiation converted into electrical energy in these solar PV cells?
How does the absorption probability of photons behave in these solar PV cells as a function
of photon energy?

Explain the lightning sphere method and how it is used in the design of solar PV power plants.
A solar PV power plant is to be installed on the roof of a single-family house with a gable
roof in a place where lightning protection is needed against the effects of displacement current
induced in solar generator wires by distant and nearby lightning strikes. as well as direct
lightning strikes (there is an open area around the house). What kind of lightning protection
system is needed for the solar PV power plant?

PV module has 80 series connected identical silicon PV cells and four bypass diodes each protecting
20 series connected PV cells. Each PV cell has a short circuit current of 8 A and an open circuit
voltage of 600 mV in standard test conditions (STC).

a)
b)

b)

Draw current and power of the PV module as a function of voltage in STC conditions.

Draw current and power of the PV module as a function of voltage in STC temperature when
eight of the PV cells protected by one bypass diode are partially shaded receiving an irradiance
of 125 W/m? and the rest of the cells receive clear sky irradiance of 500 W/m?.

Draw current and power of the PV module as a function of voltage in case b), when two of
the bypass diodes are broken and fully nonconductive.

How are single and polycrystalline silicon PV cells made from molten pure silicon raw
material?

What are the main electrical characteristics of solar PV modules and how are they determined
for modules under different operating conditions?