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IEFE measurement report shows: Swiss-German photovoltaic storage system is among the best on the market

The ZHAW Institute of Energy Systems and Fluid Engineering (IEFE) measured a photovoltaic storage system for the companies KACO new energy and Energy Depot. The results caused a sensation at the Energy Storage Inspection of the Berlin University of Applied Sciences.

IEFE researcher Andreas Schellenberg has measured the battery storage unit and the inverter in the institute's own laboratory.

In 2021, the Berlin University of Applied Sciences (HTW) selected the best photovoltaic electricity storage systems for the fourth time. Included in the latest edition of the Energy Storage Inspection: 20 systems, 15 manufacturers, four nations. One of the systems: The hybrid inverter "blueplanet hybrid 10.0 TL3" from the German manufacturer KACO new energy in combination with the battery storage system "DOMUS 2.5" from the Swiss company Energy Depot.

IEFE for independent measurements

In order for the manufacturers of the storage systems to participate in the electricity storage inspection, an independent measurement report had to be prepared for each system. This is where the ZHAW Institute of Energy Systems and Fluid Engineering (IEFE) comes into play. Andreas Schellenberg is a research assistant in the IEFE research group Electrical Storage Systems and Power Electronics headed by Andreas Heinzelmann. Schellenberg says: "The company Energy Depot approached us with the request to measure their battery system together with the hybrid inverter from KACO new energy."

At the beginning of this year, Schellenberg set to work. In the institute's own battery storage and photovoltaic laboratory, he installed the inverter and the batteries, wired the devices to a photovoltaic simulator, and carried out the complex measurements on the entire system.

"To ensure that our measurements meet international standards, we proceeded strictly according to the efficiency guidelines of the Energy Storage Inspection," says Schellenberg. This means: With the simulator, the IEFE researchers simulated the operation of an entire year and thus all relevant conditions on the basis of prescribed reference points. They identified the key figures they were looking for on battery charging and discharging, on efficiencies or on reaction time to changes in load and production. The result of their efforts: a complete measurement report that IEFE was able to forward to HTW Berlin. "In this way, we made it possible for our partners to participate in the electricity storage inspection. "

"Very good system efficiency" and the best response time

Based on the measurement results of all institutes, HTW Berlin calculated the System Performance Index, or SPI for short, for each of the 20 systems. The result for the system measured by IEFE: an SPI of around 94 percent and thus the third-best value of all applicants – as one of only five systems, the one from KACO new energy and Energy Depot was classified in efficiency class A. Prof. Dr. Volker Quaschning, Professor of Renewable Energy Systems at HTW Berlin and co-author of the study, attests a "very good system efficiency" to the German-Swiss coproduction.

The system measured by IEFE was convincing not only with its very high SPI, but also with its response time. The authors of the study on the Energy Storage Inspection write that the system scores "with an excellent settling time of only 0.3 s". Even though Andreas Schellenberg is aware that he and his colleagues did not work on either the inverter or the battery, he says: "The excellent performance of the system was demonstrated by our measurements."

The inspection as a show case to the public

The measurement results are pleasing in several respects for the parties involved in the collaboration. Andreas Schellenberg says: "It was and is important for KACO new energy and for Energy Depot to be included in the ranking because it is used by private households as well as electrical installers and planners to make decisions." The Energy Storage Inspection shows buyers as well as professionals which systems perform best, Schellenberg says.

Just as for the two manufacturing companies KACO new energy and Energy Depot, it is also a real achievement for the ZHAW Institute of Energy Systems and Fluid Engineering to have been involved in the Energy Storage Inspection. The test institutes involved were the Austrian Institute of Technology (AIT), the Karlsruhe Institute of Technology, TÜV Süd, the University of Kassel – and IEFE.

The ZHAW institute is thus the only one from Switzerland that has taken measurements for HTW Berlin. Franz Baumgartner, head of the ZHAW's Energy and Environmental Engineering bachelor’s degree and photovoltaics expert, says: "Today, with the Energy Storage Inspection, customers and experts receive the results of the best independent institutes on these commercial products, to which IEFE has made a decisive contribution."

Baumgartner is convinced that today's frontrunners will extend their lead in the future when more solar battery systems deliver electricity in hours with low levels of sunshine. "It is great to see companies with roots in Switzerland making a contribution here."