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Photovoltaic modules

Two photovoltaic modules are installed at IEK-8 at Forschungszentrum Jülich to measure their radiation dependent energy yield by tracking the maximum power point in the recorded I-U-Curve.

Module I: SolarWorld SW 235-poly, polycrystalline

Module II: Solarmodul First solar FS-380, thin-film

PVM ©B. Pospichal
Photovoltaic modules installed at JOYCE (front: Module I, back; Module II)

Principle - Photovoltaic

Photovoltaic modules convert radiation into electrical energy based on the so called photovoltaic effect (described by Einstein 1905). The photovoltaic effect is the stimulation of an electron to a higher energy state caused by absorption of light. Photovoltaic modules are based on semiconductors since their valence- and conduction band are completely separated, but the band gap is in the range of the energy of a photon. Thus, the photovoltaic effect causes electrons to migrate from the individual molecule structure to the conduction band. These electrons are so called free electrons. They are able to move randomly inside the crystal structure of the semiconductor. In order to produce electricity, which means to collect the excited electrons on the one side and “holes” on the other side, the semiconductors are p- and n-doped. In case of a silicon based module p-doping means to include atoms of the 3. main group and n-doping to include atoms of the 5. main group. In the region of contact, electrons of the n-doped layer move towards the p-doped layer and induce an electric field (depletion area). After a very short time this electric field reaches an equilibrium state since no more electrons can migrate to the p-doped layer. Now the free electrons are accelerated towards the positive depletion area due to this electric field. Thus, the negative charge is trapped in the conduction band in the n-doped layer and the positive charge is trapped in the p-doped layer. This induces an electric potential difference, which can be tapped from the solar module.

Principle - Yield measurements

The I-V curve (current voltage characteristic) of the modules is measured by a progressive increasing of the consumer resistance and simultaneous I-V measurements. The produced energy is released via a radiator.

Measurement modes

  • Measurements with 1 minute temporal resolution (voltages, maximum current, irradiance, modue temperature)

Data availability

Data are available on request, please fill the data request sheet and send it to

Dataset Temporal resolution File size Filename Retrieval / Remarks
PVM data 1 minute 1 file per day (15-20 MB) detailsYYYYMMDD.txt.gz contains data from both modules

Current observations at quicklook archive

Measurement examples

Poly module Irradiance
Example time series of PVM observations (left: Quicklook for the polycristalline module, right: Irradiance and efficiency)

PVM History

Period Installation angle Place Project Installed
5. October 2016 - 02.01.2017 30°, southward Forschungszentrum Jülich ET-CC yes
03.01.2017 - 10.06.2020 not installed (roof renovations)
10.06.2020 - today 30°, southward Forschungszentrum Jülich yes

Technical specifications

Parameter SolarWorld SW 235-poly First Solar - FS-380
STC power 235 Wp 80 Wp
Current 7.85 A 1.65 A
Voltage 30.2 V 48.5 V
Short circuit current 8.35 A 1.88 A
Open circuit voltage 37 V 60.8 V
System voltage 1000 V 1000 V
Dimensions 1675 mm x 1001 mm x 31 mm 1200 mm x 600 mm x 7 mm
Weight 21.2 kg 12 kg
pvm.txt · Last modified: 2021/03/01 11:18 by bpospich