Phase Change tab on Materials Dialog.
Phase Change Materials (PCMs) are often impregnated into gypsum board, plaster, concrete or other materials in order to increase the thermal storage capacity of ceilings, walls and floors. Some PCM manufactures also provide mats of pure PCM "pockets" which can be included as layers within constructions.
Example of PCM Mat
By completing a transition between solid and liquid phases PCMs can absorb large quantities of latent heat. The high latent heat storage capacity of these materials works to effectively increase thermal mass which tends to moderate interior temperatures and improve comfort conditions. PCMs are frequently used to reduce the need for mechanical cooling, peak load shifting and improving solar energy utilisation.
DesignBuilder allows you to enter manufacturers phase change properties in the form of a temperature - enthalpy curve on the Phase change tab of the Materials dialog. A set example PCM datasets is provided with the materials database that comes with DesignBuilder.
DesignBuilder supports both types of PCM modelling methods provided by EnergyPlus:
Important note: The Finite Difference solution algorithm must be used to include the effect of material phase change properties in simulations. If you use the CTF algorithm the material will behave as if its PCM option were not selected. Note also that the CTF solution algorithm is the only option available for Heating and Cooling design so the phase change effect of the material will not be seen in these calculations. An error message to this effect will be generated for PCM simulations where the CTF solution method is selected.
Tip: With Learning mode active, the Info panel for the Phase change tab includes a Set PCM Simulation options link which allows a set of default simulation properties recommended for PCM analyses to be quickly loaded.
Recommended simulation parameters for PCM
| Timestep | 12 (higher values should increase accuracy at the expense of longer simulation times) |
| Solution algorithm | 2-Finite difference |
| Difference scheme | 1-Fully implicit first order |
| Space discretisation constant | 3 |
| Relaxation factor | 1 |
| Inside face surface temperature convergence criteria | 0.01 (lower values should increase accuracy at the expense of longer simulation times) |