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You can answer to the guestions either in English or in Finnish.

53117 Solar Power Systems
Examination, 9.5.2019

Answer to each guestion 1, 2, 3 and 4 should fit into one page of a common writing paper.

a)
b)

c)

a)

b)
c)

Explain the parameter Learning Rate used to describe the development of a technology.or a
product. What has been the Learning Rated of solar PV modules since the year 2000?

What has been the global development of solar PV power during the last ten years or so in
terms of investment cost and production capacity?

What is the lightning sphere method and how is it used?

Why certain material are called direct or indirect band cap semiconductors? What kind of PV
cells can be made by using those materials and why?

Explain and define the parameter Air Mass number.

What are the key parameters describing the electrical properties of PV modules and how can
you estimate the guality of the modules?

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)

c)

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/n? and the rest of the cells receive clear sky irradiance of 500 W/nf.

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 does partial shading caused by clouds effect the operation (1-U and P-U curves) of a
typical small string generator of around 20 PV modules connected in series? Note that PV
modules always have bypass diodes.

Write the energy balance eguation for a PV module. What kind of heat transfer losses can take
place from the PV module?

How large and fast output power fluctuations can take place in PV generators during typical
days? What can be the largest and lowest PV generator power with respect to its nominal
power corresponding to the STC irradiance of 1 KW/m??