Abstract: A system (27) for reducing the temperature of cooling oil for a power transformer (12) includes a heat exchanger (44) interposed in the cooling oil system. The heat exchanger (44) relies upon a liquid-to-liquid exchange of heat from the heated oil to a coolant flowing through the heat exchanger. In one embodiment, the coolant provided to the heat exchanger is obtained from an absorption chiller (65). Heat energy is provided to the chiller (65) from a heat storage device (80). In a specific embodiment, the heat storage source (80) can be a phase change material device. In a preferred cooling system, a programmable controller (55) determines the activation and operation of the system. The controller (55) can sense transformer or cooling oil temperature to trigger activation. In a preferred embodiment, the controller (55) compares a current temperature history against a temperature profile to anticipate increased cooling requirements.

Abstract: A heat exchanger for a phase change material including a container holding the phase change material, a tube surrounding the container to define an annular space therebetween, and preferably divider walls within that annular space to create a circuitous path for heat exchange fluid to be routed in multiple passes along the length of the container when passing from the top of the annular space to the bottom of the annular space. When the heat exchanger is operated in a melt cycle, multiple heat energy transfer elements positioned within the lower portion of the container and extending through the phase change material are heatable to a sufficiently high temperature to initiate melting of the phase change material. The heat energy transfer elements are preferably electrical resistance heated rods or coils, or tubes through which is routed high temperature fluid.