**Notes/thanks/other declarations**

I would like to thank my professor from the Technical University of Berlin, Mrs. Lydia Scholz, who introduced me to this issue and helped me focus more on this area during my studies. Last but not least, my thanks go to my partner Antreas for his patience and understanding during writing.

*Energy Storage Efficiency DOI: http://dx.doi.org/10.5772/intechopen.109851*
