TÜV Rheinland announces major impact of climate on energy yield

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German testing and certification company TÜV Rheinland is investigating the impact of different climates around the world on the energy yield of solar modules used for electricity generation.

Based on the analyses performed to date, analysts at TÜV Rheinland say the yields of different modules and module technologies may differ by more than 10% depending on the respective climate.

TÜV Rheinland is seeking to determine to which extent climatic factors impact the energy yield of PV modules. In addition to temperature and sunlight, climatic factors include humidity and precipitation as well as the potential detrimental effects of sand and salty air.

In addition to evaluating modules and their potential variability in performance, TÜV Rheinland Photovoltaic Testing Laboratory evaluates PV systems to investigate the interoperability of the modules and the potential induced degradation (PID) in various climates through its Comparative Energy Yield program. TÜV Rheinland PTL is evaluating a minimum of eight module types over the course of a year in four distinct climate locations, including Davis, California, with a warm temperate climate, Tempe, Arizona, with a dry, tropical climate, Toronto, Ontario, with cold, temperate climate, and Thuwal, Saudi Arabia, with a very warm, humid climate.

The system-level approach offered in the Comparative Energy Yield program captures interoperability of the modules within a given system voltage (600 V is typical for North America and Saudi Arabia).

"This offers a unique comparison of the PID effect, module mismatch, wiring and connections, and soiling issues prevalent in many field-installed systems today," the company said.

To take comparable measurements of the energy yield of individual modules, TÜV Rheinland constructed five test facilities in Cologne, Germany, with a moderate Central European climate; Ancona, Italy, with a Mediterranean climate and salty atmosphere; Tempe, Arizona; Chennai, India, with a subtropical climate; and a test facility in the Arabian Desert where sandstorms occur.

Field investigations are currently being performed on 17 module types, including thin-film and crystalline modules, from 13 manufacturers. They are subjected to laboratory examinations and performance measurements before they undergo testing under real conditions for 24 months. All modules are then examined again in the laboratory. The special features of the various PV modules based on different designs and materials are being analyzed with regard to their performance and climate effects, seasonal effects, low-light behavior, temperature behavior and spectral behavior.

In the comparative yield analyses performed so far at TÜV Rheinland’s outdoor test facility in Cologne, yield differences of up to 5% have already been identified for different crystalline modules when compared with the measurements taken as a reference in the laboratory, which also results in corresponding differences in returns. The differences are even greater when the measured thin-film modules are included.

The TÜV Rheinland program provides participating manufacturers with reliable indications of how their modules perform in different climatic conditions and what effect the respective climate has on yield. In addition to the results of the module comparison measurements, module manufacturers will also receive information about ways to improve their product technology.

In addition to energy yield comparisons, TÜV Rheinland is examining the effect of dust and sand contamination in desert locations. The company says the research will provide valuable insight into installations in these regions, such as how different cleaning intervals will indicate the best procedures and methods for cleaning solar systems.