A system for generating power from a low grade heat source includes a heat source inlet, heat sink inlet, heat exchanger unit, and a heat engine. The heat source inlet conveys a flow of a heated fluid into the system. The heat sink inlet conveys a flow of a cooled fluid into the system. The heat exchanger unit is configured to rotate. A portion of the heat exchanger unit alternates between thermal contact with the heated fluid and thermal contact with the cooled fluid in response to being rotated. The heat engine is configured to generate power in response to the heat exchanger unit being rotated.