Exam text content

 

Calculator is not need/allowed in the exam. Seppo Valkealahti
Remember to give feedback in the Kaiku-system to get the final grade.
You can answer to the guestions either in English or in Finnish.

DEE-53117 Solar Power Systems
Examination, 16.11.2015

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

1.a) What are the main differences of light absorption in direct and indirect band gap
semiconductor materials. How do the differences affect to the light absorption

a
coefficients of these semiconductors?

b) What are the heat transfer mechanisms affecting to the temperature of a PV module?
Write the energy balance eguation by which the PV module temperature changes can be
calculated under changing operating conditions.

2. Define the following concepts (with one or two sentences).
a) Airmass.

b) Depletion region.

 

e) Lightning sphere.

d) Spectral response of solar cell.

3. a) Howcan a PV cell heat up to create a hot spot in a PV module?

b) How can PV cells be protected against hot spot heating in a PV module?

4. Three strings of twenty series connected silicon PV cells have short circuit currents of 2.0 A,
4.0 A and 4.0 A.

a) Draw the current-voltage and power-voltage curves of the PV strings.

b) Draw the current-voltage and power-voltage curves of a PV system, when the three PV
strings are connected in parallel.

c) Draw the current-voltage and power-voltage curves of a PV system, when the three PV
strings are connected in series.

d) Draw the current-voltage and power-voltage curves of a PV system, when the three PV
strings are connected in series and each string is protected with a bypass diode connected
in parallel with it.