The importance of flash testing for Energy Yield Assessments

Technical Due Diligence


When carrying out the Energy Yield Assessment of a solar PV plant, accuracy in the yield calculation is key. Improved predictions contribute to better financial planning, project financing, and overall system performance.  

Flash testing of photovoltaic PV modules, which is generally proposed by PV module manufacturers, can be useful in energy yield modelling to more precisely predict the expected energy output of a solar installation. 

What is a flash test 

Flash testing is a method used to assess the electrical characteristics and performance of PV modules. This test is typically performed under standard test conditions (STC1) in a sample of the purchased modules of the same model by applying a short, intense flash of light to simulate sunlight under STC and measuring the electrical response of the module. The electrical characteristics measured are voltage at maximum power, current at maximum power, open circuit voltage, short circuit current, maximum power, and filling factor.  

How can it be used to assess the energy yield of a PV Power Plant? 

The technical specifications of the photovoltaic modules available in the supplier’s data sheet include the peak power of the module under STC conditions. Because of possible manufacturing defects or uncertainties in the panel power measurements, a production guarantee is considered by the manufacturer. The announced peak power is generally lower than the actual power, in order to cover the margin of error. 

Flash tests enable to quickly measure the power output of a PV module and verify whether it meets its rated specifications or not. At the end of these tests, it is relevant to evaluate the statistical parameters that allow conclusions to be inferred from the quantitative data measured in the sample, in particular the standard deviation and the median. 

Comparing the values of the flashed modules with the theoretical values provided in the datasheet, parameters considered in the Energy Yield Assessment can be refined, resulting in a more accurate simulation. These include module quality gain, a parameter used to represent the increase in installed power due to the positive tolerance of the modules, and mismatch losses, resulting from statistical variations in the electrical parameters of modules connected in series with each other at DC current (losses depending not only on the technical parameters of the modules but also on the configuration of the project in question). 

In summary, flash testing plays a crucial role in assessing the electrical performance of PV modules, ensuring accuracy and quality, enabling supplier quality monitoring, and improving pre-construction Energy Yield Assessment (used for project modelling and debt sizing). Moreover, flash tests allow to monitor the degradation of modules (and therefore the PV plant) and to optimize the overall energy yield of a solar installation. Indeed, regular flash testing is recommended to maintain the long-term reliability and efficiency of a photovoltaic system but also for pre-construction yield calculations. 

As part of its Technical Due Diligence services, and in particular in Independent Energy Yield Assessments, Greensolver is able to assist you in analysing the results of the flash tests provided and based on these, formulate the hypotheses required to estimate the current or future yield of your power plant.  

As an example, during the audit of a 15 MWp power plant, Greensolver studied the flash test report carried out on a sample of 10% of the installed modules. This allowed to refine the modeling of the project, improved the expected production and reduced the uncertainty on the project. If the flash test results had not been available to Greensolver for analysis, the yield would have been penalised by 0.90%, equivalent to 148 MWh of annual production!

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Written by Paula Ortega Sacristán, Advisory Consutant and Imane Alil, Advisory Consultant