Lecture 5

Pr inc ip les of Model ing for Cyber-Phys ica l Systems

Instructor: Madhur Behl

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 1

Building Energy Simulation

Introduction to EnergyPlus

1/Ugw

1/Ugi

1/Ugo

Cgo

Cgi

Tgo

Tg

Tgi

Tz

Q.rad,e

1/Uei1/Uew1/Ueo

Ceo Cei

Ta

Teo Tei

Q.sol,e

Q.solt/2

1/Uci

1/Ucw

1/UcoCci

Cci

Ta

Q.sol,c

Q.rad,c

Ta

Q.conv + Q.

sens

1/Uii 1/Uiw 1/Uio

Cii Cio

Tci

Tco

1/Uwin Tii Tio

Q.solt/2

Q.rad,g

[ExternalWalls]

Ti

[Ceiling]

[Floor]

[InternalWalls]

[Windows]

How to find the values of the parameters ?

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 2

Previously..

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 3

Given the disturbances and inputs, the model should predict the zone temperature.

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 4

Parameter estimation is a search

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 5

Need a good starting point to avoid local minima.

Compute nominal values of the parameters.

For our model:EnergyPlus == A real building

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 6

What is EnergyPlus ?

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 7

EnergyPlus is an energy analysis and thermal load simulation program

User Building DescriptionFile

Building energy simulation

Heating/Cooling Load Calculation

Data outputs

https://github.com/NREL/EnergyPlus

io files

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 8

Weather data

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 9

• Data include

• temperature,

• humidity,

• solar,

• wind,

• rain, and

• snow flags, etc.

• Hourly data typical, can be sub-hourly • Interpolated for EnergyPlus time steps

TMY: Typical Meteorological Year data

EnergyPlus workflow and building description

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 10

Envelope Constructions, loadsschedules, etc.

HVAC templatesor custom systems

Run, compare, report, QAQC, and parametric

analysis

EnergyPlus –SimulationArchitecture

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 11

More than an engine or a single tool

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 12

• Whole building energy simulation.• Peak load calculation and equipment

design.• Sub-hourly, user-definable time steps.• Advanced fenestration models.• Illuminance and glare calculations.• Component-based HVAC.• Built-in HVAC and lighting control

strategies.• Functional Mockup Interface.• Standard summary and detailed output

reports.

Integrated simulation manager

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 13

Building systems simulation manager

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 14

Authoring tools: Third party interfaces

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 15

Zone and Air System Integration

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 16

Sum of convective

internal loads

Convective heat transfer

from zone surfaces

Infiltration of outside air

Inter zone air mixing

HVAC air system

Building envelope hierarchy

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 17

Site>> Building

>> Zones>> Surfaces

>> Constructions>> Materials

Energy Plus Demo

Principles of Modeling for CPS – Fall 2018 Madhur Behl madhur.behl@virginia.edu 18