A stirling engine is disclosed. The engine includes at least two fluid chambers; a displacer, which may be rotary; and a movable seal. At least one displacer may be included in each of the at least two fluid chambers. The movable seal separates the at least two fluid chambers. In a further aspect, a stirling engine may include any one of at least one heat source, at least one heat sink, at least one converter, or any combination of any two or more of the preceding.