Using a (thick) surface as thermal storage in E+
I have a building with a very thick concrete slab (more than a meter thick, over several thousands square meters of area) and would like to evaluate the potential savings of embedding pipes in the slab and thermally charge it at night to reduce my daytime peak electricity usage.
For example in the summer, a heat pump is providing chilled water to terminal units. I'd like to use the heat pump at night to cool the slab down, then during the day I'd discharge the slab first to limit the electricity used by the heat pump for cooling.
In the winter, the same heat pump (in the heating mode) is provided hot water to terminal units. I'd like to use the heat pump at night to heat the slab, then during the day I'd discharge the slab first to limit the electricity used by the heat pump for heating.
Is there any good way to do this in E+?
Are you looking to model the slab with some sort of thermal storage that is expected to delay the discharge of heat /cooling from the slab till daytime? It sounds like a typical thermally activated slab that is charged at night and continues to radiate through the daytime due to its thermal mass that can be modeled using ZoneHVAC:LowTemperatureRadiant:VariableFlow.
I am looking to use the slab as the thermal storage medium (use its thermal mass). Naively you'd want to use a ZoneHVAC:LowTemperatureRadiant:XXX object, but this is only a demand component. I'd want to sometimes charge the slab, and sometimes use it as a supply equipment, so it'd be part of a PlantEquipmentOperationCoolingLoad for some hours of the day for example (can't do that with the LowTemp object)
So you mean, the slab doesn't necessarily have a flow through it during the night but holds the hot/cold water to be discharged into the terminal equipment during the day before the plant kicks in? Or is it that the discharge flow of hot/cold water from the outlet of the slab is diverted to the terminal equipment for few hours at the start of the day?
In the winter the slab would preheat the return water from the terminal units, before it goes to the heat pump, to reduce the peak power for the HP, and in the summer the same would happen, just with cold water?