Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
The EMS feature of EnergyPlus allows you to override many model features, but not ALL model features. This is because the list of EMS Actuators for overriding model behavior is based on a pre-defined list by the EnergyPlus development team. For example, you cannot use an actuator to override or reset the temperature at a specific node in an HVAC system. For the actuators related to thermal envelope, there are none that allow you to override information for a construction layer's temperature or enthalpy. Sorry, but it looks like you won't be able to accurately model this kind of dynamic PCM in one EnergyPlus simulation.
As an alternative, you could run two simulations -- one with the PCM always "outside" of the insulation layer (closer to outside air) and one with the PCM layer always "inside" of the insulation layer (closer to the zone). This would also be useful to have these two cases to compare results to what you originally proposed (applying EMS to move the PCM layers dynamically). Maybe if you use a small enough timestep, or if the amount of PCM is small enough to not store lots of heat, then the results between all three cases will be similar enough to overlook the riskiness of applying EMS to move the PCM layer dynamically.
