Abstract: An energy conversion device may include a shaft including a first portion and a second portion wherein the first portion of the shaft is configured to rotate relative to the second portion of the shaft. A rotor may be coupled to the first portion of the shaft and a stator may be coupled to the second portion of the shaft. A first one-way bearing may be coupled to the first portion of the shaft and configured to transfer rotational input to the first portion of the shaft in a first direction. A second one-way bearing may be coupled to the second portion of the shaft and configured to transfer rotational input to the second portion of the shaft in a second direction opposite the first direction.