The best storage system under 8kWh is built by RCT Power

Berlin University of Applied Sciences (HTW) has published the results of their 2018 electricity storage survey (Stromspeicher-Inspektion 2018): The best storage system under 8kWh is built by RCT Power.

How efficient are PV storage systems that are available on the German market? The research team from HTW Berlin was looking for a conclusive answer to that question.

The team examined the performance data of 20 storage systems with a storage capacity of up to 10.5 kWh. In accordance with the efficiency guidelines established by the German Solar Association and German Energy Storage Association the research team then determined the System Performance Index (SPI) for every system. The SPI takes into account all energy loss mechanisms. The 2018 electricity storage survey thus provides a realistic view of the actual performance of the tested storage systems.

Thomas Hauser, Managing Director of RCT Power GmbH, explains why the study is so important for his company.

Mr Hauser, did you expect this result? 

Well, yes, we did expect to be among the top-ranked systems in the survey as our system did compete with an advantage. Both the battery and the inverter are from RCT Power. As a German manufacturer, we can ,therefore, offer a complete system with perfectly matched components. To be top ranked in the category storage systems up to 8 kWh is obviously a nice confirmation of our work, especially as we submitted external data for the survey.

External data? Can you explain this term in more detail?

Sure. We considered the survey a great opportunity to find out how our system compares to our competitors. RCT Power had asked the renowned University of Applied Sciences (BFH -TI) in Bern, Switzerland to perform the system measurements in accordance with efficiency guidelines set by the German Solar Association and German Energy Storage Association. Their test results were then submitted to the HTW Berlin.

And the result was probably excellent ...

Exactly. Our RCT Power System, which consists of the Power Storage DC 6.0 and the Power Battery 5.7, is, according to the summary comments of the examiners, "one of the best systems measured so far in our laboratory". All test results were above average and the BFH-TI team attested the RCT Power System for high conversion efficiency and extremely accurate and fast control.

In the overall ranking of the 2018 electricity storage survey, RCT Power came only in at second. Why?

The participants were able to submit systems with a usable storage capacity of up to 10.5 kWh. And as you may know, the system voltage increases with the usable capacity of the battery when battery modules are connected in series, The higher the voltage, the higher the conversion efficiency which in turn has a direct effect on the SPI value. Therefore a direct comparison of systems with different usable storage capacity is not really possible. We entered the survey with a system with a storage capacity of 5.1 kWh and still took 2nd place overall. Our SPI of 90,7% was significantly above the participant average SPI of 88.1%. According to our efficiency measurements for the systems using our storage Power Battery 7.6, 9.6 and 11.5 and the implicit increasing battery voltages, 1-2% higher SPI values can be realised. We are proud of these performance figures.

Why did RCT Power "only" enter with the 5.1 kWh system?

That was a conscious decision. It is the most popular system size on the market. Storage systems between 5 and 8 kWh are ideal for residential buildings. We wanted to know if an independent test would confirm our development strategy of rethinking storage technology. Rethinking is exactly what we did. We have rethought the storage technology with the best engineers. The result is a flexible and reliable storage solution that impresses above all with its simplicity. Looking at the results of the HTW Berlin comparative study of solar storage systems we feel completely vindicated in our strategy and highly motivated to continue in exactly the same way.

> Read the study of HTW Berlin (PDF)