High-precision measurement technology from the laboratory is making its way into industry: Ingenieurbüro Mencke und Tegtmeyer GmbH (IB-MuT) has brought the large-area reference solar cell “BigRef”, pre-developed by the Institute for Solar Energy Research (ISFH), to market maturity.

BigRef – Large-area reference solar cell for measuring and adjusting the irradiance of solar simulators in photovoltaics

In research and development as well as in production of solar cells and photovoltaic modules, these have to be measured accurately under a wide range of illumination conditions. For this purpose, solar simulators are usually used, which simulate the light of the sun and enable measurements in the laboratory under realistic light conditions. For precise measurements, the light conditions in the solar simulator must be known exactly. With the BigRef, the irradiance and homogeneity of the light fields in the solar simulators can be accurately determined.

The BigRef is currently the only rugged encapsulated large-area (160 × 160 mm²) reference solar cell available on the market. The unique design of the BigRef, which utilizes techniques like Ethylene-vinyl acetate encapsulation from photovoltaic module construction, results in extremely good thermal coupling to the base plate and thus excellent temperature control capability of the sensor. This is essential for precise calibration of constant-light solar simulators and spectral responsivity measurement systems.

The biggest advantage of the BigRef, however, is its size. Commercially available solar cells with edge lengths of currently around 160 mm are used as the active sensor element. Typical encapsulated reference solar cells available on the market have an edge length of only 20 mm. In contrast, photovoltaic modules currently achieve sizes of up to 1.3 × 2.2 m². The light fields of solar simulators for modules are correspondingly large. To measure their homogeneity, the irradiated area must be scanned and a homogeneity correction must be performed. The smaller the reference solar cell used for this purpose, the greater the effort. When calibrating the irradiance of solar simulators for single solar cells, a large-area reference solar cell has the advantage that a homogeneity correction can even be omitted completely. This not only simplifies the calibration procedure, but also leads to a lower measurement uncertainty.

The development of the BigRef is a continuation of the joint work in the “Uniform Sun” project, which was funded by the Central Innovation Program for SMEs (ZIM) and focused on the development of a full-size photovoltaic module for measuring the light field homogeneity of large-area solar simulators for photovoltaic modules.

The BigRef is available from IB-MuT and can be calibrated at the solar cell calibration laboratory of ISFH CalTeC with respect to irradiance, current-voltage characteristic, linearity and spectral responsivity.

Ingenieurbüro Mencke und Tegtmeyer GmbH is a company in Lower Saxony with 18 employees that has been working on the improvement and quality enhancement of PV modules and systems since 1993. IB-MuT develops robust and highly accurate calibrated silicon solar irradiance sensors, which are used by leading manufacturers of PV monitoring systems and inverters worldwide. Another field of activity is the development and production of measuring systems for photovoltaic research and industry.

The Lower-Saxony-based Institute for Solar Energy Research ISFH conducts with currently 158 employees in two departments research on innovative technologies for solar energy utilization. The photovoltaics department develops new industry-oriented solar cell technologies and highly efficient photovoltaic modules that can be industrialized. The ISFH is a member of the Forschungsverbund Erneuerbare Energien (FVEE) and the Deutsche Industrieforschungsgemeinschaft Konrad Zuse e.V. (Zuse-Gemeinschaft) as well as an affiliated institute of the Leibniz Universität Hannover.

Dr. Karsten Bothe
Head of Solar Cell Calibration Laboratory
Phone: +49 (0) 5151 999 425
Fax: +49 (0) 5151 999 400
Mobile: +49 (0) 176 151 999 02
eMail: k.bothe@isfh.de