A power generator comprises a casing (110) that in use is deployed in an environment in which the casing is subjected to an excitation motion such as wave motion. A series of masses (101, 103a-c) is located within the casing, wherein at least a first mass is coupled to the casing by a first spring (102), each of the masses is coupled to at least one adjacent mass by a respective spring, and wherein the casing and the series of masses bring a motion of the power generator into resonance with the excitation motion. A plurality of electric machines each comprising a stator and a field source are each associated with a corresponding mass such that a relative motion of a mass and associated electric machine generates electrical power. A power takeoff circuit receives generated electrical power from the plurality of electric machines and outputs electrical power from the power generator.

A power generator comprises a casing (110) that in use is deployed in an environment in which the casing is subjected to an excitation motion such as wave motion. A series of masses (101, 103a-c) is located within the casing, wherein at least a first mass is coupled to the casing by a first spring (102), each of the masses is coupled to at least one adjacent mass by a respective spring, and wherein the casing and the series of masses bring a motion of the power generator into resonance with the excitation motion. A plurality of electric machines each comprising a stator and a field source are each associated with a corresponding mass such that a relative motion of a mass and associated electric machine generates electrical power. A power takeoff circuit receives generated electrical power from the plurality of electric machines and outputs electrical power from the power generator.

A wave power generator comprises a buoyant casing (500) intended to float in a body of water. An electric machine (103) located within the casing has an armature and a field source, the electric machine having a fixed part coupled to the casing and a moving part. A counterweight assembly (104) is movable within the casing, comprising the moving part of the electric machine and wherein a relative movement of the counterweight assembly and the fixed part of the electric machine generates electric power. Power storage (400) stores power generated by the electric machine and a control system (200) determines a bi-directional energy flow between the power storage and the armature, wherein energy is returned to the electric machine to drive a motion of the counterweight assembly anti-symmetrically to a motion of the casing.