PV Laboratory

A photovoltaic research laboratory established by SOLSUM sp. z o.o., one of the market leaders in photovoltaic installations in Poland, has been set up near Nowy Sącz. 

The main measuring apparatus and, at the same time, the most advanced device of the entire laboratory is a Class AAAA solar simulator (the so-called sun chamber), in which it is possible to generate high-quality light with a spectrum similar to sunlight (compliant with the STC standard), which falls on the tested photovoltaic module placed in a specially designed test chamber. STC standard (Standard Test Conditions) are the standard conditions under which photovoltaic modules reaching the market are tested to determine their power and other parameters.

With advanced measuring equipment, you can check the most important parameters and quality of photovoltaic modules which will be faster, cheaper and much more accessible. This class of testing equipment and laboratory facilities can boast only a few centers in Europe. It is also the only laboratory in Poland that is 100% directly powered by RES and completely energy independent thanks to an energy storage system.

The measurement is performed for STC conditions based on reference modules and a measurement procedure developed in the laboratory.

The electronic system of the solar simulator records the parameters from the flash generator lamps, the voltage, current and irradiance signals, and, at the same time, the temperature measurement is carried out.

All parameters related to the measurement can be set in specially developed software. The measurement results are displayed graphically and digitally. Key parameters are calculated from the measured current and voltage signals.

The solar simulator can test photovoltaic modules in mono/polycrystalline silicon, amorphous, CdTe and CIS/CIGS technologies.

The simulator measures the parameters of graph IV (current-voltage curve). This can be achieved at any intensity level from 200 W/m2 to 1200 W/m2 and AM 1.5 spectrum.

In addition, the following parameters can be determined:
ISC – short-circuit current of the module,
IMP – current at the maximum power point,
VOC – open circuit voltage
VMP – voltage at the point of maximum power,
PM – maximum power,
FF – fill factor,
Eff – radiation conversion efficiency

And curve deviation analysis for resistance evaluation:
RS – series resistance
RSH – parallel resistance

According to IEC 60891

Dedicated software is used for data processing and analysis.

View of software interface with measurement results 


The parameter that tells about the quality of cells/modules is the fill factor (FF). This factor is a measure of the quality of a solar cell. It is the available power at the point of maximum power (Pm) divided by the open circuit voltage (VOC) and short circuit current (ISC). The fill factor is directly affected by the values of cell series, shunt resistance and diode losses. Increasing the shunt resistance (Rsh) and decreasing the series resistance (Rs) leads to a higher fill factor, resulting in higher efficiency and bringing the cell’s output power closer to the theoretical maximum. The fill factor typically ranges from 50% to 82% (the higher the better) and shows how much variation in power output can result from cell/module quality.

The sunlight simulator operates in the AAAA measurement class determined in accordance with IEC 60904-09, 2nd edition. The basic technical parameters of the simulator and the parameters that make up the AAAA measurement class are shown in Table 1.

Parameter Value (measurement class)
Maximum module size [cm x cm] 240 x 130
Number of measurements in 1 h 120
Measurement cage size [cm x cm x cm] 465 × 240 × 250
Lamp pulse duration [ms] 15
Range of irradiance [W/m2] 200 ÷ 1000
Lamp lifespan [flash] 40 000
Spectrum < ± 25% (A)
Heterogeneity < ±2% (A)
Short-term instability (STI) < 0.5% (A)
Long-term instability (LTI) < ±2% (A)

Source: SOLSUM’s own materials


Electroluminescence measurement (EL method) of photovoltaic modules – that is, the ability to detect micro cracks and defects in modules.

With the intensive development of the photovoltaic market, modules of different quality are appearing on the market, and previously unheard of phenomena such as PID (potential difference-induced degradation) and LID (light-induced degradation) have begun to be detected on photovoltaic farms, so more and more attention is paid to verifying the quality of purchased modules. In the case of photovoltaic farms, 1-2% of reduced energy production per year means losses of several hundred thousand PLN over the life of such an installation.

Luminescence is a phenomenon involving the emission of electromagnetic radiation by solids and liquids under the influence of an excitation factor. In the case of electroluminescence, the excitation factor is the electric current flowing through the cell. When the PV module is connected to a DC power source, it is possible to observe the process of radiative recombination. As a result, a quantum of energy is produced, which is emitted in the form of an electromagnetic wave of near-infrared wavelength. Solar cells emit weak infrared light when current flows through them. By using high-quality cameras, it is possible to record the emitted radiation.

EL imaging is available with two integrated cameras. The 500 μm pixel resolution camera allows accurate measurement. Inactive areas and components applied to cells, such as busbars, as well as visible defects in cells, busbars and improperly made solder joints are shown as darker components than defect-free areas on the image which allows detection and identification of defects in photovoltaic modules.

Image of modules obtained by EL method, test in SOLSUM laboratory


Modules are manufactured to a mixed tolerance (-+5Wp), so examining the actual power and quality of modules under STC “Standard Test Condition” and assigning them to the appropriate set guarantees optimal performance and long-term trouble-free operation. Studies conducted by independent institutions show that about 5% of photovoltaic modules reach end users with latent defects.

From our long experience (since 2012), we know that most module defects (e.g. microcracks) occur at the stage of loading, unloading and transportation very often from distant Asia and installation. They are invisible to the naked eye and neither the end user, nor the installer is able to detect it at the stage of installation or at the beginning of operation. Then it generates significant costs, reduces energy production and causes faster degradation. By testing photovoltaic modules in our laboratory, we can be sure that our customers will receive only modules of the highest quality and performance, and through research and development work in the field of photovoltaics, this market will grow even faster.

However, what is most important from the point of view of the end customer is: the long-term trouble-free operation of the installation, its highest productivity, whether the power loss of the installation after years is as guaranteed by the manufacturer/vendor at the time of sale, and whether any damage occurred at the stage of installation or operation. This has a major impact on the payback time of the investment and possibly warranty claims. The only way to find this out is to test the modules in the SOLSUM Laboratory using the highest quality certified equipment (solar chamber) and software. Such a procedure gives 100% certainty about the current power of the modules, the degree of power degradation and possible damage invisible to the naked eye.

Below are photos taken during the testing of cells in the “sun chamber” using measuring devices:

Various types of damage and defects that have a negative impact on the production and life of the installation, and are not visible to the naked eye.


Source: SOLSUM’s own materials


Professional test stand for measuring electrical parameters of photovoltaic modules. 

Such a stand allows a complete measurement of an electrical installation in accordance with PN-EN 61557, performs all the necessary measurements required for a photovoltaic installation included in PN-EN 62446, and additionally allows the creation of I – U characteristics, calculation of STC values (standard test conditions) and measurement of power on the AC and DC sides of the inverter/inverter (1-phase). The instrument is designed for demanding operating conditions (up to 1000V, 15 A DC). To significantly increase user safety, the MI 3108 EurotestPV is supplied with a safety probe that ensures safe disconnection of the instrument from the installation every time. The test stand allows, among other things, to perform measurements in photovoltaic installations:

  • Voltage, current, power, energy
  • Insulation resistance
  • Uoc – open circuit voltage and Isc – short circuit current
  • I-U characteristics of strings and photovoltaic modules
  • Irradiance
  • Voltage, current, power, power factor, harmonics.
  • Calculation of performance of photovoltaic modules, inverter, installation efficiency
  • Insulation resistance
  • Continuity of protective conductors
  • Impedance of lines
  • Loop impedance (high current and non-triggered RCD subfunction)
  • RCD testing (type AC, A and B)
  • Ground resistance
  • AC current (load and leakage)
  • TRMS voltage, frequency, phase sequence
  • Power, energy, harmonics
  • Graphical presentation of characteristics: Mapping of I – U string/module characteristics on the instrument’s LCD screen.
  • Power and efficiency measurements: 2 values of voltage and 2 values of current during simultaneous measurement of AC and DC side values in single-phase and three-phase installations.
  • Remote recorder of environmental parameters: Optional device to remotely measure the irradiance and temperature of a PV module while taking measurements

Thermography (thermal imaging) the use of a thermal imaging camera allows the recording of thermal radiation and temperature distribution on the surface under examination, which makes it possible to detect, for example, hot-spots in photovoltaic modules.

Example of an examination with a thermal imaging camera


The combination of electroluminescence testing with current-voltage characterization, thermography, and solar chamber testing along with visual evaluation enables a comprehensive analysis of the module’s condition.

The range of services that the laboratory provides:

  • Measurement of module parameters under STC conditions
  • Detection of micro-cracks, electrically inactive areas
  • Detection of defects in modules, deviations from the factory parameters declared by the manufacturer
  • Diagnostics of modules for parameter decline and failure
  • Measuring module aging by comparing parameters over time periods
  • Warranty diagnostics of modules
  • Module testing and comparison of results as an independent institution
  • Training and consulting activities

We will be happy to cooperate especially with:

  • Owners and users of photovoltaic installations
  • Companies installing photovoltaic installations
  • Scientific units for the purpose of conducting research
  • Local governments, technical schools, universities
  • Manufacturers of photovoltaic modules

Preparation of samples for testing: 

It is acceptable to measure photovoltaic modules made of cells based on monocrystalline and polycrystalline silicon, as well as thin-film modules based on amorphous silicon.

The laboratory performs tests on photovoltaic modules supplied by the customer. In the course of agreeing on the terms of execution of the order, the customer is informed about the requirements for the modules and how to prepare them for testing.

In order to use the services of the laboratory, please contact us by e-mail or telephone.

Contact details:

SOLSUM sp. z o.o.
Nowy Sącz – Świniarsko 821
33-395 Chelmiec
Phone: +48 18 540 91 40

SOLSUM sp. z o.o., whose founder and trend-setting owner in both the commercial and research fields is Pawel Gumulak, is one of the leading Polish companies with more than 8 years of experience in the design and installation of photovoltaic, energy storage and heat pump installations. The company operates throughout Poland, but we have also implemented photovoltaic installations in Europe and Africa. We are also engaged in training activities, with more than 2,000 people having already participated in the SOLSUM Academy. We have established a strategic partnership with the AGH University of Science and Technology in Krakow for work on photovoltaic module research and innovation. In 2020, we launched a photovoltaic laboratory and a 100% energy-independent production and office building – the first project of its kind in Poland. Our company has won many awards and prizes, e.g. Leader of Eco-Entrepreneurship.

If you want to develop yourself, work in one of the most modern companies in Poland, have interesting ideas, knowledge, experience or simply a desire for a non-trivial job and are not afraid of challenges – call or send us your resume to rekrutacja@solsum.pl



M. Frazão, J. A. Silva, K. Lobato, and J. M. Serra, “Electroluminescence of silicon solar cells using a consumer grade digital camera,” Measurement: Journal of the International Measurement Confederation, vol. 99, pp. 7–12, 2017


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