An energy recovery device including: at least one capacitor with variable capacitance, the capacitor including a fixed electrode, a dielectric layer, and a liquid electrode; and a mechanism to inject an electric charge into the capacitor and to remove the electric charge therefrom, including a charge injection electrode forming a portion of the second face positioned upstream from the fixed electrode in the direction of displacement of the liquid electrode, and a charge removal electrode forming a portion of the second face positioned downstream from the fixed electrode in the direction of displacement of the liquid electrode.