When a freight ship is in a harbor, a Diesel engine generator is operated to supply electric energy in the ship. Exhaust gas from the Diesel engine causes air pollution in the harbor area. In order to solve the air pollution, we have tried to develop a heat recovery system with Stirling engine generators since 2005. In this paper, we report results of our research project related the heat recovery system and the Stirling engine generators. Also we discuss about technical subjects for practical use.