Modeling PCM-Enhanced Insulation System in. EnergyPlus. Thermal Mass IV. Som Shrestha, PhD, BEMP. December 5, 2010

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1 Modeling PCM-Enhanced Insulation System in EnergyPlus Thermal Mass IV Som Shrestha, PhD, BEMP December 5, 2010

2 EnergyPlus Developed by DOE EERE BTP Whole building energy analysis and thermal load simulation program Learn more and download EnergyPlus Version 6.0.0: EnergyPlus Helpdesk: EnergyPlus Support Group at Yahoo: 2 Managed by UT-Battelle

3 EnergyPlus GUIs can be used to generate building model Not necessary to develop building system/plant model to evaluate performance of various envelope systems Actual weather data can be used Has option for input and output in SI or IP units 3 Managed by UT-Battelle

4 What information is needed for a building envelope model? Materials Construction Surfaces Zones Building 4 Managed by UT-Battelle

5 Additional input required for modeling materials with PCM IP Units SI Units 5 Managed by UT-Battelle

6 Additional input required for modeling PCM-enhanced material 300 Temperature - Enthalpy Curve (PCM only) 120 Temperature - Enthalpy Curve (Cellulose with 20% PCM) Enthalpy, kj/kg Enthalpy, kj/kg Temperature, C Temperature, C 6 Managed by UT-Battelle

7 Additional input required for modeling PCM-enhanced material The table must cover the entire temperature range that will be seen by the material in the simulation. 7 Managed by UT-Battelle

8 HeatBalanceAlgorithms in EnergyPlus ConductionTransferFunction ConductionFiniteDifference ConductionFiniteDifferenceSimplified Transfer Function method ignores the variable thermal properties If the Simplified solution algorithm is being used and there is a surface that should be simulated with the detailed node arrangement, it should be specified with Construction:UseHBAlgorithmCondFDDetailed 8 Managed by UT-Battelle

9 Check the reasonableness of the results while using Finite Difference method 55 Annual Heating/Cooling Load 50 GJ Check the error message: EnergyPlus Completed Successfully: Warning; Inside surface heat balance did not converge with Max Temp Difference [C] = vs Max Allowed Temp Diff [C] =2.000E- 003 Compare the result with the result from simulation using TransferFunction algorithm 9 Managed by UT-Battelle Transfor Function Finite Difference with PCM

10 Timestep vs. computation time Suggested minimum number of timesteps in hour for Conduction Finite Difference solutions is 20 If the requested timestep is not evenly divisible into 60, the nearest evenly divisible timestep will be used In some cases, lower number of time steps will not necessarily reduce the computation time (lower number of time steps higher delta T between the time steps (higher than Temperature Convergence Tolerance) more iterations) 10 Managed by UT-Battelle

11 Temperature distribution Inside PCM wall can also be evaluated Layer Interface Temperature Outside Surface 1" Inside PCM Outside Surface OSB ½ C " Inside PCM 3" Inside PCM Inside Surface 1" Inside PCM 2" Inside PCM 3" Inside PCM Gypsum Board 5/8" Inside Surface 0:00 6:00 12:00 18:00 0:00 Inside layer temperature can be calculated using CondFD heat balance algorithm. 11 Managed by UT-Battelle

12 Parametric study is convenient in EnergyPlus Parametric objects can be used in a single file as an alternative of maintaining a group of files with small differences Parametric:SetValueForRun Parametric:Logic Parametric:RunControl Parametric:FileNameSuffix Simulation of a group of input files can also be performed using multiple weather files 12 Managed by UT-Battelle

13 What is the equivalent thermal performance of PCM-enhanced insulation system! Depends upon: Location Building geometry, orientation, material configuration Heating/cooling set point temperature schedule Season of the year Based on annual heating + cooling load or energy cost? Heating/cooling equipment efficiency Whole building or a particular wall 13 Managed by UT-Battelle

14 Benchmarking EnergyPlus against ZEBRA Data Zero Energy Building Research Alliance (ZEBRA) founded by the ORNL, Schaad Companies, TVA, and many industry partners to showcase energy savings potential of advanced and dynamic envelope systems, ground and air source heat pump, energyefficient appliances etc. PCM-enhanced cellulose insulation is used in one house. Each building is equipped with over 200 sensors. 14 Managed by UT-Battelle

15 Properties of microencapsulated PCM and PCM-enhanced cellulose are being evaluated Test Wall Rotatable Guarded Hot Box T Outside Heat Flow Meter Apparatus 1" Cellulose + PCM T T 1" 24" 24" 1" T 24" Cellulose T 2" 15 Managed by UT-Battelle T HFT Inside Wall Configuration

16 Other important materials properties were also evaluated Thermal conductivity Thermal emittance and solar reflectance of exposed surfaces UV, Visible and IR transmittance and SHGC of windows The study will benchmark E+ against field data 16 Managed by UT-Battelle

17 Summary EnergyPlus is a convenient tool to evaluate performance of building materials mixed with PCM Finite difference heat balance method must be selected to simulate materials with variable thermal properties To evaluate the performance of PCM, finite difference heat balance should be used in all simulations Parametric study is convenient in newer version of EnergyPlus (Version 4.0 onward) Data collected at ZEBRA building will help benchmark EnergyPlus output 17 Managed by UT-Battelle

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