HVAC system modeling using EcosimPro: A digital twin for advanced control studies & virtual commisioning simulations

Abstract

At the European Organization for Nuclear Research (CERN), the upper management has increased its focus on environmental matters within the last couple of years. The Energy Management Panel has selected three main strategies to minimize environmental damage: “increase efficiency, use less, and recover waste energy.”

New projects have been allocated resources, and within the Industrial Control Systems group, a Ph.D. project is currently underway on energy-optimal control. It investigates the possibilities of deploying advanced controls, namely model-based predictive control (MPC) on cooling- and HVAC plants at CERN, to increase energy efficiency and reduce power consumption. As many of the cooling systems at CERN are critical, some even af-fecting beam availability if not operating, it is not straightforward to intervene in cooling plants that already are operating satisfactorily but not fully utilizing an energy-efficient operation.

In conjunction with the Ph.D. project, a pilot project was launched, ultimately aiming to deploy an MPC controller on a HVAC plant at CERN. A virtual commissioning envi-ronment was considered essential for the succession because the MPC can be tested and validated using a digital twin.

In this thesis, the development and validation of a high-fidelity plant model are carried out for use in the pilot project. Previous use cases where virtual commissioning has been performed were investigated, and available data from the as-built documentation and op-erational data were used to parametrize the model. A different set of data were used to cross-validate the model.

A two-step validation study was performed on the model to determine its applicability to be valid for a summer scenario. Finally, the model was handed over for use in the Ph.D. project to ultimately perform virtual commissioning proving good results which can be used to evaluate the performance of the MPC, validate it, and aid future decisions regard-ing the deployment on the pilot plant.

Full text

HVAC SYSTEM MODELING USING ECOSIMPRO:
A DIGITAL TWIN FOR ADVANCED CONTROL STUDIES
& VIRTUAL COMMISSIONING SIMULATIONS
LASSE AHRENDSEN
Industrial Control Systems Group, Controls Engineering Section
Beams Department
CERN-THESIS-2022-376
15/06/2022

ABSTRACT

ACKNOWLEDGMENTS
Lasse Ahrendsen

REFERENCES

LIST OF FIGURES & TABLES

CONTENTS
ABSTRACT ........................................................................................................................................ iii
ACKNOWLEDGMENTS ..................................................................................................................... iv
REFERENCES ....................................................................................................................................... v
LIST OF FIGURES & TABLES ............................................................................................................ vii
1 INTRODUCTION ........................................................................................................ 1
1.1 CERN ....................................................................................................................................... 1
1.2 Problem statement ................................................................................................................ 2
1.3 Problem formulation ............................................................................................................ 4
1.4 Delimitation ........................................................................................................................... 4
2 BACKGROUND ........................................................................................................... 5
2.1 Research at CERN and the Laboratory .............................................................................. 5
2.1.1 LHC at the accelerator complex ................................................................................................... 5
2.2 Simulation & advanced control ......................................................................................... 9
2.2.1 Virtual commissioning: previous cases ...................................................................................... 9
2.2.2 Modelling & simulation with EcosimPro ................................................................................ 13
2.2.3 Advanced control with model-based predictive control ....................................................... 15
3 METHODOLOGY & DATA .................................................................................... 17
3.1 Workflow.............................................................................................................................. 18
3.2 Data used & methodical approach .................................................................................. 19
3.2.1 As-built documentation .............................................................................................................. 19
3.2.2 Historic control system data ....................................................................................................... 20
3.2.3 Running experiments in open-loop .......................................................................................... 21
3.3 Validation studies ............................................................................................................... 22
3.3.1 Statistical measures ..................................................................................................................... 22
4 MODEL DEVELOPMENT ....................................................................................... 24
4.1 Introduction to the pilot plant of SR1 ............................................................................. 24

4.1.1 SR1 facility .................................................................................................................................... 24
4.1.2 The air handling units of the SR1 plant ................................................................................... 27
4.2 Building the model ............................................................................................................. 31
4.3 Parameter identification & estimation ........................................................................... 34
4.3.1 Setting up the simulation monitor ............................................................................................ 34
4.3.2 Fan, airflows & pressure drops in the system network ......................................................... 36
4.3.3 Air dampers ................................................................................................................................... 40
4.3.4 Heat exchanger & control valve ................................................................................................. 46
4.3.5 Summary of the model development work ............................................................................. 49
5 SIMULATION RESULTS AND DISCUSSION ................................................... 50
5.1 Open-loop simulation for model validation ................................................................. 50
5.1.1 Plots ................................................................................................................................................ 50
5.1.2 RMSE & MAPE ............................................................................................................................ 57
5.1.3 Interpretation of the open-loop simulation ............................................................................. 57
5.2 Closed-loop simulation for model validation ............................................................... 59
5.2.1 Plots ................................................................................................................................................ 59
5.2.2 Interpretation of the closed-loop simulation .......................................................................... 64
5.3 Applicability of the developed plant model ................................................................. 65
5.4 Virtual commissioning simulation .................................................................................. 67
5.4.1 Plots ................................................................................................................................................ 67
5.4.2 Review on the virtual commissioning simulation results .................................................... 72
6 CONCLUSION ........................................................................................................... 74
6.1 Perspectives & future work .............................................................................................. 75

1
INTRODUCTION
1.1 CERN

1.2 Problem statement

1.3 Problem formulation
Research question
Objective
1.4 Delimitation

2
BACKGROUND
2.1 Research at CERN and the Laboratory
2.1.1 LHC at the accelerator complex

Main contributing technologies

2.2 Simulation & advanced control
2.2.1 Virtual commissioning: previous cases
The CMS cavern case

The WHR case

Summary

2.2.2 Modelling & simulation with EcosimPro
▪
▪
▪ -
-
-

Use of EcosimPro in the context of the thesis

2.2.3 Advanced control with model-based predictive control
The MPC concept

3
METHODOLOGY & DATA

3.1 Workflow

3.2 Data used & methodical approach
▪
▪
▪ -
3.2.1 As-built documentation

3.2.2 Historic control system data
Extraction of datasets

3.2.3 Running experiments in open-loop

3.3 Validation studies
▪
▪
3.3.1 Statistical measures

4
MODEL DEVELOPMENT
4.1 Introduction to the pilot plant of SR1
4.1.1 SR1 facility

4.1.2 The air handling units of the SR1 plant
▪
▪
▪

4.2 Building the model

4.3 Parameter identification & estimation
4.3.1 Setting up the simulation monitor

▪
▪ o -
-
-
▪
▪ o -
-
-
-
-
▪
▪ o -
-
-
-
-
▪ o -
-

4.3.2 Fan, airflows & pressure drops in the system network

4.3.3 Air dampers

Minimum fresh air flow damper

Exhaust air dampers

4.3.4 Heat exchanger & control valve
Heat exchanger model
▪
▪
▪

Control valve
Measures to solve the discovered problems
▪
▪

4.3.5 Summary of the model development work

5
SIMULATION RESULTS AND DISCUSSION
5.1 Open-loop simulation for model validation
5.1.1 Plots

5.1.2 RMSE & MAPE
5.1.3 Interpretation of the open-loop simulation
Air temperature measurements

5.2 Closed-loop simulation for model validation
5.2.1 Plots

5.2.2 Interpretation of the closed-loop simulation

5.3 Applicability of the developed plant model
Validation

5.4 Virtual commissioning simulation
[°𝑪]
5.4.1 Plots

5.4.2 Review on the virtual commissioning simulation results
▪
▪
▪
▪

Summary

6
CONCLUSION

6.1 Perspectives & future work
HVAC libraries in EcosimPro
Diagnostics module for AHUs