By Vincent Helmbrecht, European Distributed Energy Resources Laboratories (DERlab) e.V.; Diana Craciun, Research Coordinator, European Distributed Energy Resources Laboratories (DERlab) e.V.; Abraham Ellis, Technicalhead of Renewables Grid Integration, Sandia National Laboratories; Jennifer Granata, Leader of PV Reliability Team, Sandia National Laboratories; Stathis Tselepis, Head of the Photovoltaic Systems and Distributed Generation Department, Centre for Renewable Energy Sources and Saving (CRES),; Anastasios Kyritsis, PV System and DER Department, Centre for Renewable Energy Sources and Saving (CRES),; Nikos Hatziargyriou, CEO, Institute of Communication and Computer Systems - National Technical University of Athens (ICCS-NTUA)
As yet, procedures for long-term tests of photovoltaic modules in outdoor conditions have not been considered by international standardization committees. Although many laboratories perform long-term PV outdoor tests, a commonly agreed and standardized procedure has so far not been adopted. The European Distributed Energy Resources Laboratories’ (DERlab) approach to filling the gap of international standardization has led to the development of a basic protocol that complies with European and international standards, while providing specific common guidelines and procedures for measuring the energy yield of PV modules for at least one year in outdoor conditions. The DERlab procedures for long-term PV module testing are described in this paper, and the range of analyses that can be derived from the data, such as module degradation, are discussed. The paper also presents the DERlab approach to measuring module performance in outdoor conditions, which can be used to complement energy-rating methods suggested in international standards. DERlab has created consistent measuring procedures that allow the direct comparison of the energy yield of solar modules taking into account the site-specific factors of different locations and varying climatic conditions, as well as a maintenance guideline.