Electrical operation behavior and energy efficiency of battery systems in a virtual storage power plant

Significance 

In the current societal set up, energy consumption is on a meteoric rise owing to the current modernization of almost all equipment. Consequently, an energy strain is thereby being imposed on the existing infrastructure and to some extent; the entire ecosystem, hence a change in global energy supply is highly imperative. Renewable energy is a plausible alternative for the future but as of now, the technological expedites available do not allow for such exploitations. Fortunately, applicable alternatives are within reach if one was to consider energy storage. This would come in handy in resolving the current non-congruence energy issues, specifically using lithium ion batteries. This rising interest in battery systems for such applications demands a thorough comprehension of the systems performance for efficient technical and economical optimization. In addition, for an economic and successful operation of battery systems, one must first indulge in a detailed investigation of the systems’ efficiency behavior.

Recently, Christopher Betzin and Matthias Luther from the University of Erlangen-Nuremberg in Germany and in collaboration with Holger Wolfschmidt at Siemens AG carried out an electrical system behavior and energy efficiency analysis of two different Li-ion battery systems. They  assessed the applicability of the two storage systems in primary control reserve power market. Their work is currently published in the research journal, Electrical Power and Energy Systems.

In brief, the two systems were designed for operation in a virtual storage plant with respect to the primary control reserve. Next, the research team analyzed the efficiency of both systems from which, a model to show the impact on the operation and standby behavior was developed. The developed model was then transferred to a simulation framework where it was used to investigate the applicability of the battery systems towards primary control reserve. Lastly, real frequency data of continental European transmission system were used to simulate the behavior of the two systems in order to determine energy losses during operation.

The authors observed that the efficiency measurement for the round-trip efficiency was at one specific state of charge point, which was representative for, the complete state of charge range. Additionally, they noted that the overall battery storage system efficiency showed an insignificant dependency on the state of charge. Furthermore, they recorded that the systems’ efficiency had a decisive influence on the overall efficiency of the battery storage systems and was responsible for the decrease of the latter.

In a nutshell, Christopher Betzin and colleagues presented an in-depth assessment of the electrical and energy efficiency behavior of two different battery storage systems. The standby and the auxiliary losses in the battery systems were determined. In general, they observed that the optimization potential for battery storage systems providing primary control reserve was auspicious. Altogether, primary control reserve is one possible application as grid support service for battery systems and the simulation discussed here help identify strengths and weaknesses of such systems based on the determined efficiencies, and for this case, the results support an optimized operation strategy.

Reference

Christopher Betzin, Holger Wolfschmidt, Matthias Luther. Electrical operation behavior and energy efficiency of battery systems in a virtual storage power plant for primary control reserve. Electrical Power and Energy Systems, volume 97 (2018) page 138–145.

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