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News article3 February 20202 min read

European Solar Test Installation (ESTI) renews and expands its accreditation

ESTI outdoor at JRC Ispra site
© European Union / European Union

The JRC European Solar Test Installation (ESTI), one of the world’s leading photovoltaics (PV) calibration laboratories, has successfully passed another rigorous certification audit that renews its accreditation, in accordance to ISO/IEC 17025:2017, and extends it to encompass new testing methods.

The latest inclusions in the ESTI accreditation scheme, namely the calibration of bifacial PV devices at Standard Test Conditions (IEC TS 60904-1-2), the power matrix (IEC 61853-1) and the linearity (IEC 60904-10) calibration of PV devices, make ESTI the first certified calibration laboratory worldwide for these three new methods.

With its long-standing expertise in PV testing and calibration, ESTI continues to significantly contribute to, and often lead, the development of international PV standards within the International Electrotechnical Commission (IEC). In addition to assessing the latest PV technology (e.g. bifacial PV modules, which can collect and convert sunlight from both sides, front and rear), such standards introduce new approaches to a more comprehensive performance assessment, such as taking into account the environmental factors PV modules will be subject to upon installation in specific locations.

The latest in a series of standards, IEC 61853, was completed in August 2018 thanks to ESTI leadership. The IEC 61853-1, in particular, describes how to measure the electrical power of a PV device in relation to its temperature and sunlight intensity in order to estimate the energy production in one year.

Reliable data on the electrical power of a PV module in various illumination conditions also requires accurate measurement of the incident light intensity. This is obtained by means of a reference device, which has to comply with IEC 60904-4 and whose output has to be proportional to the illumination level. This property is verified according to the IEC 60904-10, currently under revision under ESTI leadership.

ESTI technical and scientific contribution to IEC 60904-10 has also entailed developing the missing data analysis for one of the methods included in the standard and introducing an advanced method to overcome some of its limitations.


ESTI has been a leader in PV testing and calibration since its opening in 1979. The development of testing and calibration methods to evaluate the performance of PV devices has always been part of ESTI's core activity. Over the years, its considerable amount of research work has provided the foundations for drafting several international standards for performance and quality assessment of PV devices and PV systems.

ESTI was the first laboratory in the world accredited for photovoltaic calibrations and has continued to improve and introduce new methods, extending to new materials and leading the worldwide effort to reduce the uncertainty of solar photovoltaic measurements. Uncertainty expresses how confident any reference laboratory is that the measured quantity is the true value. ESTI has reduced the level of uncertainty from over 2.00% to under 0.48% in recent years.

The accreditation renewal audit is performed by ACCREDIA every four years. It consists of a periodic inspection of the laboratory by national and international experts to ensure ESTI conforms to ISO/IEC17025. During the process, auditors witness an actual calibration in-situ and, together with ESTI staff, assess the Calibration and Measurement Capability (CMC), which tells customers how correct a laboratory can measure.

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Relevant publications

Linearity of photovoltaic devices: quantitative assessment with N-lamp method

Electrical performance of bifacial silicon PV modules under different indoor mounting configurations affecting the rear reflected irradiance


Publication date
3 February 2020