Energy harvesting – the extraction of energy from the local environment for conversion
to electrical power – is of particular interest for low power wireless devices such as body or
machine mounted sensors. Motion and vibration are a potential energy source, and can be
exploited by inertial devices, which derive electrical power by the damping of the relative movement
of a proof mass mounted in a frame attached to the moving host. Inertial devices using
linear motion of the proof mass, which have been extensively studied and developed, have a
maximum power output limited by the internal travel range of the proof mass. In the current
paper, the potential power of devices using rotating proof masses, powered by linear or
rotational host motion, is analysed. Two new operation modes are introduced: rotationally resonant
devices, and devices driven by continuous rotation. In each case the maximum achievable
power densities are estimated, and these are compared with equivalent expressions for
devices with linear proof mass motion where appropriate. The possibility of using actively
driven, gyroscopic structures is then introduced, and the potential power of such devices is considered.
By avoiding the linear displacement limit and the limited mass of conventional devices,
it is shown that increases in obtainable power are possible if parasitic damping is minimized,
particularly for cases of low linear source amplitude. Finally, issues of implementation are discussed,
with an emphasis on microengineered devices