Coupling of Simulation Tools - Building Controls Virtual Test Bed Michael Wetter. August, 2010

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1 Acknowledgements Coupling of Simulation Tools - Building Controls Virtual Test Bed Michael Wetter Simulation Research Group Building Technologies Department Energy and Environmental Technologies Division Lawrence Berkeley National Laboratory August, 2010 Prof. Edward A. Lee and Christopher Brooks (University of California at Berkeley), Gregor Henze, Charles Corbin, Anthony Florita and Peter May-Ostendorp (University of Colorado at Boulder), Rui Zhang (Carnegie Mellon), Zhengwei Li (Georgia Institute of Technology), Phil Haves and Andrew McNeill (LBNL). 1

2 Overview Motivation Classification of run-time coupling Building Controls Virtual Test Bed 5

3 Modeling Tools energy airflow controls lighting Fragmentation within domain Little integration across domains No interface to control systems for model-based operation 3

4 Distinct Approaches for Runtime Coupling Problem formulation Equations that model two different systems (e.g., envelope heat transfer & HVAC system): ẋ 1 = f 1 (x 1,x 2 ) ẋ 2 = f 2 (x 2,x 1 ) x 1 (0) = x 1,0 x 2 (0) = x 2,0 Implementations a) Link legacy simulators ẋ 1 = f 1 (x 1,x 2 ) x 1 (0) = x 1,0 Exchange data every few seconds. ẋ 2 = f 2 (x 2,x 1 ) x 2 (0) = x 2,0 E.g.: Building Controls Virtual Test Bed b) Link directly differential equations ẋ = f(x) x(0) = x 0 E.g.: Modelica 4

5 Building Controls Virtual Test Bed (BCVTB) Enable Co-simulation for integrated multidisciplinary analysis Use of domain-specific tools Model-based system-level design Model-based operation Available from Based on Ptolemy II from UC Berkeley. 5

6 Building Controls Virtual Test Bed Open-source middle-ware based on UC Berkeley s Ptolemy II program. Synchronizes and exchanges data as (simulation-)time progresses. building energy TRNSYS airflow Fluent building energy EnergyPlus HVAC & controls Modelica controls Simulink implemented funded in proposal in discussion controls & data analysis MATLAB building energy ESP-r BCVTB wireless networks Ptolemy II hardware in the loop fenestration Window 6 building automation BACnet lighting Radiance real-time data www+xml 6

7 Simple Example: Room Heater Set point + - Controller Plant Controller: Discrete time proportional controller y(k + 1) = max(0, min(1,k p (T set T (k)))) Plant: Room model T (k + 1) = T (k)+ t C UA(T out T (k)) + Q 0 y(k) 7

8 Simple Example: Room Heater Discrete Time Proportional Controller y(k + 1) = max(0, min(1,k p (T set T (k)))) Implementation in Simulink y(k + 1) T (k) 8

9 Simple Example: Room Heater Room model T (k + 1) = T (k)+ t C Implementation in Modelica UA(T out T (k)) + Q 0 y(k) T (k + 1) y(k) 9

10 Simple Example: Room Heater y(k + 1) T (k) y(k) T (k + 1) 10

11 BCVTB Architecture Director Simulator 1 system call system call Simulator 2 BCVTB C library configuration file Actor Actor configuration file BCVTB C library BSD Socket Client TCP/IP BSD Socket Server BSD Socket Server TCP/IP BSD Socket Client

12 Controls in Simulink, Building in EnergyPlus 12

13 Controls in Simulink, Building in EnergyPlus 13

14 Ex: HVAC in Modelica, Building in EnergyPlus PID Q PID ṁ w T X w Rapid virtual prototyping. Path towards embedded computing. Whole building energy analysis. Reuse of 500,000 lines of code. 14

15 Modelica Implementation of VAV System with ASHRAE Standard Sequence of Controls, linked to EnergyPlus DOE Benchmark Bldg. Variable Air Volume Flow (VAV) System Terminal reheat. Finite state machine for supervisory mode transition. Local loop control with P and PI controllers. Original system model 1200 components 4,300 equations 150 state variables 15

16 Modelica Implementation of VAV System with ASHRAE Standard Sequence of Controls, linked to EnergyPlus DOE Benchmark Bldg. Can execute realistic supervisory and local loop control in Modelica linked to EnergyPlus through cosimulation. R&D Needs: Support for rapid virtual prototyping. Robustness of DAE solver. Computing time. Packaging to make technology easier accessible to non-experts. Scope of validated model library (HVAC & control components and systems). Code generation to link design to operation. 16

17 Radiance 1. Read line from weather data file 2. Parse line and pass useful data System command calls a c-shell script to run Radiance 4. Plot result Illuminance vs. time (January 1-7) 17

18 Radiance Script Arguments Arguments from BCVTB Radiance Commands Output 18

19 Control in BCVTB 19

20 BACnet Enables simulation and/or data analysis coupled to Building Automation Systems. Can read to and write from BACnet devices. BCVTB input tokens BACnet reader (or BACnet writer) output tokens BACnet stack* xml configuration file * BACnet stack from (Steve Karg) 20

21 Reusable modules for model-based operation Tool selection depends on required - model resolution - emulation of actual control & operation - dynamics of equipment - analysis capabilities www/xml - smoothness - state initialization Hybrid systems, emulate actual feedback control Discrete time, idealized controls 21

22 Questions? Source code and compiled versions (Windows, Mac & Linux) are available at 22