Apollo simulator at ESTI

European Solar Test Installation

The European Solar Test Installation (ESTI) is a European reference laboratory for the verification of the power and energy generation of photovoltaic devices. ESTI is located at the JRC’s Ispra site in Italy. It has been the forefront of development of standards for electrical performance of PV products since its launch in the late 1970’s.


ESTI has unique range of class AAA solar simulators for precision cell and module power measurements, as well as outdoor testing facilities.
  • Wacom and Sciencetech continuous solar simulators for areas of up to 30 cm x 30 cm; 
  • Oriel simulator for spectral response
  • High intensity simulator (up to more than 500 suns) for concentrator devices.
  • Pasan IIIB large area pulsed simulator
  • Pasan IIB simulator dedicated to module spectral response and temperature coefficient measurements
  • Apollo large area steady state simulator in a dedicated darkroom (2 m x 2 m test area).
  • Spire large area long-pulse (80 ms) simulator. 
ESTI also operates an outdoor facility for 
  • Flat-plate module and CPV calibrations
  • NOCT tests
  • Energy rating tests
  • Long-term exposure tests.

Traceability of Measurements to Primary Standards

To have legal validity, measurements need to have an unbroken traceability chain to international primary standards and a calculation of uncertainty.  For PV devices the most important and difficult aspect is the irradiance determination, for which ESTI is accredited for three methods.
The global sunlight method and the direct sunlight method transfer the irradiance calibration from two cavity radiometers, which are calibrated every five years against the World Radiometric Reference at the International Pyrheliometer Comparison held in Davos, Switzerland. The solar simulator method makes reference to the international irradiance scale, as represented by a standard lamp.


ESTI's maintains an ISO-17025 compliant laboratory management system and is accredited for the calibration of photovoltaic devices (LAT 225) by the Italian accreditation body ACCREDIA


  • Free-of-charge calibration of reference devices for national laboratories and verification on request of technologies developed in EU programmes
  • Collaborative research with industrial partners on new materials and/or concepts to promote European competitiveness and improved standards. 
  • Funded R&D in shared-cost European programmes
  • Commercial calibration service for external customers, focusing on new technologies and respecting subsidiarity principles.
For the calibration price list or information on services please contact: esti.services@jrc.ec.europa.eu

Large Scale Facade

In 1994 an amorphous silicon array was installed on the façade of the ELSA building housing the European Laboratory for Structural Assessment. At the time it was the largest façade installation in the world using amorphous silicon technology.
The main characteristics are:
Total area: 770m2
Active PV area: 544m2
Nominal peak power after initial degradation: 21kWp
Grid connection via four 5kW SMA inverters
Operation with very little downtime since October 1994

ESTI Meteo On-Line

Comprehensive metrological solar resource data is essential for evaluating the results of ESTI's outdoor exposure testing on PV modules.

The ESTI meteo tower measures and records the following parameters:

Global irradiation on 0, 45, 60 and 90° planes
Diffuse irradiation 
Relative humidity
Wind speed
Wind direction
Rain gauge 
Ambient temperature
Local Barometric Pressure