TV Rheinland Announces Major Impact of Climate on Energy Yield

TV Rheinland Evaluates Energy Yield of Solar Modules in Different Climates, Expects Yield Differences of More Than 10% for Individual Module Types

Tempe, Ariz., July 1, 2014. TV 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, the experts at TV Rheinland believe that the yields of different modules and module technologies may differ by more than 10% depending on the respective climate.

The research seeks to determine to which extent climatic factors impact the energy yield of photovoltaic (PV) modules. Besides 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, TV Rheinland PTL 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. TV Rheinland PTL is evaluating a minimum of eight module types over the course of a year in four distinct climate locations, including Davis, Calif., with a warm temperate climate, Tempe, Ariz., with a dry, tropical climate, Toronto, Ontario, with cold, temperate climate, and Thuwal, Kingdom of 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 (600V 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.

To take comparable measurements of the energy yield of individual modules, TV Rheinland constructed five test facilities: Cologne in Germany with a moderate Central European climate, Ancona in Italy with a Mediterranean climate and salty atmosphere, Tempe, Ariz., Chennai in 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 a laboratory examination and performance measurement before they undergo testing under real conditions for 24 months. All modules are then examined in the laboratory again. 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 TV 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.

This 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. Besides energy yield comparisons, investigations are being performed into the effect of dust and sand contamination in desert locations. The research will provide valuable insight into installations in these regions; for example, different cleaning intervals will indicate the best procedures and methods for cleaning solar systems.

For more information, contact Bill Shisler at or visit

About TV Rheinland

Founded in 1872, TV Rheinland is a global leader in independent testing, inspection, and certification services, ensuring quality and safety for people, the environment and technology in nearly all aspects of life. The company maintains a presence in 500 locations spanning 66 countries, employs 18,000 people and has an annual revenue of $2.2 billion (1.6 billion). TV Rheinland inspects technical equipment, products and services, oversees projects and helps to shape processes for a wide variety of companies through its worldwide network of approved labs, testing facilities and education centers. Since 2006, the company has been a member of the United Nations Global Compact to promote sustainability and combat corruption. For more information, visit

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