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This paper presents the design of a cost effective, hybrid energy harvesting circuit combining a solar cell and a rectenna capable to harvest ambient electromagnetic energy. Electromagnetic analysis is used to model and optimize the designed circuits in order to allow the antenna and solar cell to share the same area leading to a compact structure. Nonlinear harmonic balance optimization is used to maximize the RF-to-DC conversion efficiency of the rectenna circuitry in the presence of the solar cell and both wideband and multiband topologies are presented. Furthermore, a low cost and flexible polyethylene terephthalate PET substrate and a flexible amorphous silicon solar cell are chosen, providing for both a low cost and conformal structure. A prototype able to generate a maximum DC power of 56 mW when the solar cell is illuminated with 100 mW/cm2 solar irradiance, and a dual band rectenna demonstrating an efficiency of 15% around 850 MHz and 1850 MHz when illuminated by a microwave signal of available power is presented.