Storage System Performance

Efficiency of the power conversion path “battery discharging” as a function of the rated output power [1]
System efficiency for a reference year [1]
Energy losses for a reference year [1]

The increase in electricity prices along with a decrease in the price of storage systems has led to a rapid expansion of the photovoltaic (PV) home storage system market, particularly in Germany. In order to be economically viable, PV home storage systems must fulfil certain performance criteria. The overall performance and achievable self-sufficiency ratio of a PV battery home storage system depends on the efficiencies of the system components, the standby consumption, the reaction time of the home storage system as well as the intelligence of the overall system control software. So far, PV home storage system still show very big differences in their performance. However, poor system performance can result in the system being no longer economically viable.

Since 2015, investigations have been carried out in the Battery Technology Center to evaluate and systematically assess the efficiency of PV home storage systems. This was done, among other things, as part of the project Safety First and now as part of the projects Testbench and Perform. For this purpose, the systems are integrated into a hardware-in-the-loop test environment developed at KIT and various tests are carried out, such as determining the available capacity of the storage system or efficiency measurements of the individual components. Among other things, the measurements take place based on reference days for reference households. Furthermore, measurements of the energy conversion paths (battery charging, battery discharging, PV direct feed-in), the battery efficiency and the control performance are carried out according to the efficiency guidelines for home storage systems of the German Energy Storage Association (BVES) and the German Solar Industry Association (BSW Solar).

Thanks to the numerous activities, the Battery Technology Center has gained a high expertise in this field and offers home storage measurements according to the efficiency guidelines for the industry.

Further Information:

Contact: Nina Munzke, Felix Büchle

[1] Munzke, N.; Schwarz, B.; Büchle, F.; Hiller, M. Evaluation of the Efficiency and Resulting Electrical and Economic Losses of Photovoltaic Home Storage Systems. J. Energy Storage 2021, 33, 101724, doi:10.1016/j.est.2020.101724.