PURPOSE: To save space and curtail a construction cost by setting a plant barge of a sea water temperature difference power plant to be a semi-, sub-type forming into one body a heat exchanger occupying the greater part of the plant and an underwater lower hull.

CONSTITUTION: As shown in the figures, this plant barge, which is set in a semi-, sub-type, comprises the part above the sea surface and the part immersed underseas. Underwater lower hulls 1 and 1' almost symmetrical to each other. Cold water picked out of the deep sea is supplied to a comdenser 6 through an intake valve 2, a sea water intake 3 of the lower hull 1, a filter space 4 and a pump 5. The medium discharged from the turbine 11 of a dynamo is condensed into liquid after heat- exchange with the cold water, sent to an evaporator 6' through a pump 8' and evaporated into steam to drive the turbine 11 after heat exchange with warm water collected from the surface of the sea. The lower hulls are built in a dual structure so as to obtain buoyancy and insulate heat.