Energy extraction via repetitive Penrose process in rotating charged black holes

We study the repetitive Penrose process in a rotating charged black hole described by the Kerr–Sen geometry. We show that the presence of charge reduces the size of the ergoregion but enhances the maximum energy that can be extracted at extremal rotation. By tracking the evolution of the various quantities associated to the black hole under consideration such as mass, spin, and irreducible mass over multiple cycles, we evaluate the total extracted energy and efficiency. Our results show that the Sen parameter increases the total rotational energy capacity of the black hole, creating a larger theoretical reservoir for extraction. However, it simultaneously reduces the efficiency of individual particle decay as well as the overall energy yield per iteration. While the charge parameter allows the energy extraction process to persist over a larger number of cycles and continue at lower spin thresholds, it significantly modifies the limiting behaviour and decreases the magnitude of the extraction compared to the uncharged Kerr case.