A piezoelectric-photovoltaic hybrid structure is described, having a plurality of superposed layers including a photovoltaic layer and a piezoelectric substrate. A method of forming such a structure is also described, including the steps of providing a piezoelectric substrate and superposing a photovoltaic layer over the substrate. A power conversion system is described, comprising such a hybrid structure with a first circuit connected to the piezoelectric substrate and a second circuit connected to the photovoltaic layer. Also discussed is a method of generating, storing, distributing, or consuming electrical energy, involving the use of such a system in connection with a distribution circuit or network, electrical load, or energy storage device.; A further power conversion system is described where the piezoelectric and photovoltaic circuits are connected to a single, or a respective, DC-DC converter. A set of such power conversion systems may be connected in series at their output terminals.