A renewable energy systems optimised for a specific application in one location may be inadequate in another location even if the application and user requirements are identical. The enormous variations between RES, which are the result of design options, user requirements and local climatic conditions, make it difficult to compare RES and the operation of the components which have been selected. Without comparison it is not easy to analyse the performance of components and systems and draw conclusions on the most suitable products and operating strategies. But only recommendations which take the specific conditions of use into account and are based on conclusions drawn from measurements of RES operation provide guidance to planners, users and operators.

As a first step, a method is required how to evaluate the data of monitored renewable energy systems (RES) in such a way that the operating conditions and performance of individual components and the system as a whole can be analysed and compared. It is then necessary to classify RES into a number of distinct categories in which the components are used in a similar manner and are subjected to the same combination of stress factors. Only RES belonging to the same category of use can be compared in a meaningful manner. Recommendations on how to design and operate a RES and how to test components and select the most suitable product can be made for each category. A particular RES has to be assigned to the categories which best reflect the overall conditions of use of the components and the recommendations for each category are then used as recommendations for the components and the system as a whole.

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