PhotoClass – Towards an energy-based parameter for photovoltaic classification

Dr. Karsten Bothe
Abteilungsleiter PV: Verträge und IP
Tel.: +49(0)5151-999 425

The photovoltaic world market volume was about 50 billion Euros in 2012. Thus every percent uncertainty in energy yield estimation leads to a financial uncertainty of 500 million Euros. The current efficiency and peak power characterisation under STC does not allow for differentiation according to the most relevant parameter in the marketplace which is energy production under specific climatic conditions. This is particularly relevant in Europe where PV systems of different technologies are operated in a wide range of climatic conditions.

The project addresses the following scientific and technical objectives:

  • A metric (energy based) for PV efficiency will be developed and its uncertainty budget will be assessed. Standardised environmental data-sets will be defined for Europe and beyond.
  • Robust and improved characterisation methods with accuracy sufficient for the parameters necessary for the new metric (e.g. spectrally resolved angular dependency of the responsivity, low light performance, and temperature dependency) will be developed. This will include solving metrological challenges for new PV technologies.
  • The measurement uncertainty for the absolute measurement of the natural and simulator irradiation conditions, spectrally and angularly resolved, will be reduced. The upper limit of the measured wavelength will be extended from 1050 nm to 2000 nm.
  • The spectrally and angularly resolved measurements of solar devices will be validated by comparison with integral measurements. Primary traceability and harmonisation of indoor/outdoor characterisation methods will be established through a NMI level intercomparison.
  • New reference devices will be developed for an accurate SI traceable calibration process from the cell to the solar park. In addition, procedures for their application will be developed.


PTB – Physikalisch-Technische Bundesanstalt (Germany), INTA – Instituto Nacional de Técnica Aeroespacial (Spain), JRC – Joint Research Centre (European Commission), LNE – Laboratoire national de métrologie et d’essais (France), VTT/MIKES – Technical Research Centre of Finland Ltd (Finland), NPL Management Limited (United Kingdom), VSL B.V. (Netherlands), SUPSI – Scuola Universitaria Professionale della Svizzera Italiana (Switzerland), TÜV Rheinland Energie und Umwelt GmbH (Germany), Fraunhofer ISE (Germany), Loughborough University (United Kingdom), ISFH (Germany)

Duration of the project

01.05.2014 – 30.04.2017