No-coverage answer
There is no information in the Taygetan contact material to answer this question. While the material discusses Tartaria, civilisation resets, and pre-existing advanced infrastructure at length, the specific claim that architectural arches in old cities functioned as battery storage or energy devices is never addressed. The transcripts do not discuss the electrical or energy-storage properties of arched architecture, nor do they connect specific European or global city structures to Tartarian origins in this way.
For the general Taygetan account of Tartaria and the civilisation reset, see the answers to "What is Tartaria and was it real?" and "What caused the Tartarian mud floods?"
Sources: None. Searched all 834+ transcripts and enhanced topic index. No coverage found.