Modular, stackable PCM-based thermal battery apparatus

A thermal battery assembly includes a modules configured to be stacked vertically on top of each other. The modules includes an electronics module; a first tank module; and a second tank module. A base defines a bottom of the stack and is configured to receive thereon the lowermost module of the stack for supporting the stack on a floor. Each tank module includes a phase change material (PCM); a heat exchanger assembly with heat exchangers immersed in the phase change material, a first set thereof defining a PCM charging circuit, and a second set defining a PCM discharging circuit; a first exterior connection port configured for fluid communication with an inflow of the PCM discharging circuit and a second exterior connection port configured for fluid communication with an outflow of the PCM discharging circuit. Heating or cooling capacity can be increased by adding another tank module to the stack.