FYPSim is a framework that enables the modeling of various energy harvesting technologies and the sizing of energy storage technologies at the system level with application to wireless sensor networks. In this paper, we present the specific features of FYPSim related to energy harvesting exploiting indoor solar, indoor air flow, and indoor radio frequency energy sources. We also describe the models used for modeling hybrid energy harvesting and battery management. Our experimental results illustrate how FYPSim can be used to evaluate the above technologies in combination with Li-Ion batteries and supercapacitors.