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Combined solar simulator: A solar simulator illuminates hybrid collectors – so-called PVT collectors – under laboratory conditions with a light spectrum similar to the sun.
© TÜV Rheinland
Standards and testing procedures
02.04.2013

The diagram shows the structure of an optimised glazed hybrid collector.
© Fraunhofer ISE

Photovoltaic modules, thermal solar collectors and hybrid collectors can be tested in the solar testing centre at TÜV Rheinland.
© TÜV Rheinland

Uniform testing of hybrid collectors

The existing standards for photovoltaic modules are insufficient for hybrid collectors. Therefore researchers are now developing new testing procedures for these so-called PVT collectors, which produce both electricity and heat. The new guidelines are intended to make the operation of the systems and the yield forecasts more secure.

There are already standards and testing methods for photovoltaic modules and solar thermal collectors. However, when combining both technologies new problems occur – everywhere where fluids are inside and electricity flows. This is one reason why hybrid collectors are still very much a niche product in the market. “Without suitable standards for reliably testing their safety, the products will struggle to establish themselves,” says Willi Bihler, Managing Director of Solarzentrum Allgäu.
A new research consortium is therefore investigating possibilities for the standardisation of multifunctional photovoltaic solar thermal collectors. The aim is to develop a testing basis so that innovative products can utilise solar energy even more efficiently in future. In addition to Solarzentrum Allgäu and TÜV Rheinland, Düsseldorf University of Applied Sciences and the Fraunhofer Institute for Solar Energy Systems (ISE) are also involved in the project. The results of the research project shall then be incorporated in the work of national and international standardisation committees.

“The current safety provisions for photovoltaic modules are insufficient for analysing the interaction between the electrical and water-conducting parts contained in thermal collectors,” explains Ulrich Fritzsche, Project Manager at TÜV Rheinland. There are various photovoltaic and solar thermal standards for certifying different construction types. “However, we now need to precisely determine which modifications are required here as a result of the interaction between the two technologies.”

More output through cooling

PVT collectors are a new technology that increases the efficiency of conventional photovoltaic modules and utilises previously unused heat. The output of photovoltaic modules reduces as the temperature of the solar cells increases. PVT collectors, on the other hand, actively remove the heat and utilise it for heating purposes. A positive side effect is that the cells are cooled.

Glazed PVT collectors are covered with an additional glass pane to make even better use of the heat. This substantially increases the temperature, which in turn impacts on the materials and components used. The heat development in collectors enclosed with a glass pane places considerable stress on, for example, the electrical systems.

During the course of the project, the researchers are therefore defining a testing procedure and necessary characteristic values in order to be able to describe the construction types and the performance capability of PVT collectors under different operating conditions. This is intended to reliably ensure the quality and safety of collectors and thus improve the framework for introducing this technology.
The German Ministry of Economics and Technology is funding the research project until autumn 2014.

Type approval of PV modules

TÜV Rheinland tests the safety, performance capability, economic efficiency, quality and durability of solar energy systems. For example in its “solar simulator” test rig, photovoltaic modules and solar and PVT collectors are illuminated with a light spectrum similar to the sun under laboratory conditions. In the laboratory the researchers also test whether leakage current occurs and whether the electrical safety is guaranteed.
In accordance with the International Electrotechnical Commission (IEC), the 61215 standard has become established as the certification mark for photovoltaic modules with crystalline silicon cells. This takes into account all parameters responsible for ageing modules. The certification distinguishes between radiation, thermal and mechanical stresses.
In 2008 a comparable standard, IEC 61646, was brought out for thin-film modules, which takes into account their particular properties and the degradation behaviour caused by radiation influences.

Double use of roofs

In addition, the researchers from Fraunhofer ISE have also developed a PVT collector that can efficiently generate solar heat. The BINE-Projektinfo brochure (10/2012) “Using solar roofs twice over” presents the project in detail.

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Technical laboratory test rigs
TÜV Rheinland Energie und Umwelt GmbH