An apparatus for generating power includes a fluid chamber configured to receive borehole fluid, one or more conductive coils surrounding the fluid chamber, a reciprocating magnetic shuttle disposed in the fluid chamber and dividing the fluid chamber into a first volume and a second volume, a first conduit connected to the first volume, and a second conduit connected to the second volume, the first conduit and the second conduit extending from a tubular conduit to an annulus. The apparatus includes a switching assembly configured to alternate between a first operating state where the first volume is in fluid communication with the annulus and a second operating state where the first volume is in fluid communication with the tubular conduit, to alternate a direction of differential pressure between the first volume and the second volume and cause the magnetic shuttle to move in a reciprocating motion and generate an electric current.