cee 243:week 5 introduction to energyplus & model outputs e+ model
TRANSCRIPT
Copyright 2011
EnergyPlus and Model Outputs
CEE 243
CEE 243:Week 5
Introduction to EnergyPlus & Model Outputs
E+ model of Y2E2
James O’Donnell Ph.D.
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EnergyPlus and Model Outputs
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Agenda
1. EnergyPlus Concepts
2. Examples
3. Ideal Industry Integration of Simulation
4. Conclusions
5. Homework
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Big ideas
• creating simulation models requires a process
to model the facility and populate assumptions
about building thermal properties
– Best to create analyses with careful attention to a
well-established process
• E+ allows flexible assumptions and simulation
outputs. This session shows:
– The principles behind EnergyPlus
– Visualization of important E+ Outputs
– Other possible simulation outputs
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EnergyPlus Concepts
• E+ assumes
– Time dependent heat conduction
• Conduction through building surfaces calculated with
conduction transfer functions
• Heat storage and time lags
– Air Migration between zones
• Air exchange follows a nodal model
– Only analyzes what is explicitly described
• Missing wall does not let air in
• Missing roof does not let sun in
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EnergyPlus Concepts (cont’d)
• Heat balance loads calculation (one of two load
calculation methods recommended by
ASHRAE)
• Moisture balance calculation
• Simultaneous building/systems solution
• Sub-hourly time steps
• Modular HVAC system simulation
• WINDOW 6 methodology
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EnergyPlus Concepts (cont’d)
• Simple input/output file structures
• No surface, zone or system limits
– Defaults to 50 coils per HVAC loop
– Can be increased
• Links to other software
– COMIS, wind-induced airflow
– TRNYSYS, Photovoltaics
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EnergyPlus Structure
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Note: these UIs
are not available
in mid-2011
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Integrated Simulation Manager
• Fully integrated simulation of loads,
systems and plant
– Integrated simulation allows capacity limits to
be modeled more realistically
– Provides tighter coupling between the air-
and water-side of the system and plant
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Integrated Simulation Manager (cont’d)
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Note: these arrows
represent two-way
information flow
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Today’s Learning Itinerary
• Run Control
• Geometry
• Internal Loads
• Systems
• Control
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Process to create an EnergyPlus model
BIM
GST
IDF Generator
(LBNL project)
IDF Geometry
IFC Geometry
IDF Setpoints
Schedules
IDF HVAC
systems
IDF Controls
Architectural
drawings
Mechanical
drawings
EPW Weather
file
Field
surveys
Manufacturer
product data
Predicted
data Material
library
Data Format
Legend:
Model or data
Process Tool
Information Flow
Design BIM
Analytical BIM
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Examples
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Examples
1. Example 1: Geometry Only
2. Example 2: Manually modify to add
insulation for one zone
3. Example 3: Load Determination
4. Example 4: HVAC System
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Example Description
• 1 zone building with a door and a window on the south façade.
• Construction Descriptions – Walls, Floors, Ceiling (Cavity Wall)
– Window (Single Pane)
• Create in ArchiCAD
• Save as IFC
• Run Through GST
• GST Output = Energyplus input file.
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Run Control
Assume:
• Design Day (San Jose)
• Design Day Only
• No annual simulation
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Simple Model Setup
• Box model with concrete walls low
thermal mass (Shown in Sketch Up).
– 1 South Facing Window
– 1 South Facing Door
• Necessary Inputs
• Design Day Data (Santa Clara).
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Simple Model 1 Output
• Outputs with an RVI file
• Look at zone temperature
• Conductive heat transfer
• Output Contains OA DB, Zone DB, Perhaps Wall Conductance
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Example 1: Output (2 Two Design Days)
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Example 1: AO DB Temp V Zone DB Temp
Temp (C)
-5
0
5
10
15
20
25
30
35
Environment:Outdoor Dry Bulb [C](Hourly) TESTZONE_001:Zone/Sys Air Temperature [C](Hourly)
Note: zone temp swings far
from assumed functional
intent of 23oC ~= 74oF
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Simple Model 2
• Add insulation to the walls
• Add Triple Glazing
• Compare with previous results
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Example 2: Output (2 Design Days)
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0
5
10
15
20
25
30
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Tem
pe
ratu
re C
Example 2: AO DB Temp V Zone DB Temp
Environment:Outdoor Dry Bulb [C](Hourly) TESTZONE_001:Zone/Sys Air Temperature [C](Hourly)
Note: zone temp stays
close to assumed functional
intent of 23oC ~= 74oF
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Simple Model 3
• Zone sizing
• System sizing
• Highlight Max heating and cooling loads
and max heating Load
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Simple Model 3 Outputs: Zone Sizing
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0
2000000
4000000
6000000
8000000
10000000
12000000
14000000
Sen
sib
le L
oad
(W
)
Zone Sensible Load: Alternative 1
TESTZONE_001:Zone/Sys Sensible Heating Energy [J](Hourly) TESTZONE_001:Zone/Sys Sensible Cooling Energy [J](Hourly)
Note: heating in winter
Note: cooling in summer
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Example 3: Impact of moving building from San Jose to San Francisco
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0
2000000
4000000
6000000
8000000
10000000
12000000
14000000
Lo
ad (
J)
Design Days: Zone Sensible Loads
TESTZONE_001:Zone/Sys Sensible Heating Energy [J](Hourly) TESTZONE_001:Zone/Sys Sensible Cooling Energy [J](Hourly)
Note: heating in winter
slightly less
Note: cooling in summer
slightly less
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Systems Definition
• Engineering Description (On Board)
• E+ Description (On Board)
• Additional inputs
– Setpoint Schedules,
– Branches etc.
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Example 4: System Temperatures
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0
5
10
15
20
25
Tem
pe
ratu
re C
System Dry Bulb Temperatures
Environment:Outdoor Dry Bulb [C](Hourly)AIR LOOP INLET NODE:System Node Temp[C](Hourly)COOLING COIL AIR INLET NODE:System Node Temp[C](Hourly)ZONE 1 NODE:System Node Temp[C](Hourly)ZONE 1 DAMPER INLET NODE:System Node Temp[C](Hourly)
Note: outdoor air temp in
winter is cold
Note: higher air loop inlet temp
during occupied hours
Note: space loads raise
cooling coil inlet temp
above air loop inlet temp
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Output Tables
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End Uses
Electricity
[GJ]
Natural Gas
[GJ]
Other Fuel
[GJ]
District
Cooling [GJ]
District
Heating [GJ] Water [m3]
Heating 0 0 0 0 0 0
Cooling 0 0 0 0 0 0
Interior
Lighting 0.31 0 0 0 0 0
Exterior
Lighting 0 0 0 0 0 0
Interior
Equipment 0.53 0 0 0 0 0
Exterior
Equipment 0 0 0 0 0 0
Fans 0.27 0 0 0 0 0
Pumps 0.06 0 0 0 0 0
Heat
Rejection 0 0 0 0 0 0
Humidificatio
n 0 0 0 0 0 0
Heat
Recovery 0 0 0 0 0 0
Water
Systems 0 0 0 0 0 0
Refrigeration 0 0 0 0 0 0
Generators 0 0 0 0 0 0
Total End
Uses 1.16 0 0 0 0 0
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E+ Outputs
• Variables
• Meters
• Geometry
• Reports
• Daylighting
• Fuel and Environmental
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Conclusions
• Overview of EnergyPlus
• How to request EnergyPlus outputs
• How to read EnergyPlus outputs
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Homework
• Look at E+ Getting Started Guide
Tutorials 1 & 2
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CEE 243: Week 5
E+ model of Y2E2
James O’Donnell Ph.D
Material Courtesy of Tobias Maile Ph.D
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EnergyPlus and Model Outputs
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Agenda
• Geometry model
• HVAC model
• Homework
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• complex processes associated with
analytical model development
• Current simulation tools require many
assumptions and work-arounds to
address current limitations
Big Ideas
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Creating an EnergyPlus model
BIM
GST
IDF Generator
(LBNL project)
IDF Geometry
IFC Geometry
IDF Setpoints
Schedules
IDF HVAC
systems
IDF Controls
Architectural
drawings
Mechanical
drawings
EPW Weather
file
Field
surveys
Manufacturer
product data
Predicted
data Material
library
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Geometry
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Y2E2 ArchiCAD Screenshot of design model
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Office
s
Corrido
r
Atria
Conference
Restrooms
IT-room
Electrical
room
Class room
Storage
Kitchen
AHU1
AHU2 AHU3
2nd floor room layout: Note: spaces have functions
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Boundary for air
handler unit
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2nd floor zoning (simplified model)
Radiators
Active beams (AHU1)
Fan coil units Active beams (AHU3)
Active beams (AHU2)
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Geometric features
• “Real” 3D geometry (simplified)
• Thermal zones based on HVAC equipment type
• “Air walls” to separate atria from other zones – assumed
walls with high thermal conductivity
• Geometric features have construction and material
definitions used in energy analysis
• Shading devices (roofs & on south façade)
• Simplified E+ windows (no “Window6” files)
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DXF screenshot of analytical model
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Note: missing
elements that
must be added
manually back to
analytical model
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Manual additions to geometry model
• Atria windows do not get across (triangular)
• Roof windows (skylights) do not get across (limitation in
ArchiCAD)
• Other manual corrections (window to wall relationships,
etc.)
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Constructions and materials
• Define construction including
material layers with thickness
in ArchiCAD
• IDFGenerator looks up
material name in E+
database and assigns
material parameters (e.g.,
density)
• Direction of material layer
matter (turn asymmetric
constructions around)
– From outside the zone into it
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Air
systems
Radiant slab
PV
VAV reheat
CAV Active
beams
Fume
hoods
Radiators
Radiators
Radiators
CAV Active
beams
CAV Active
beams
FC
units
FC
units
FC
units
Server
rack
Tempered
cold water
system
Tempered
hot water
system
Main
cold
water
system
Main
hot
water
system
CoGen
hot
steam
CoGen
chilled
water
HVAC system
overview
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Geometry simplifications/assumptions
• Beams and columns are ignored
• All zones are full height (no plenum spaces)
• Inconsistent 2D drawings
-> Alignment of elements between floors
• No internal doors (insignificant)
• No internal shading devices (blinds)
• Manual windows are always closed
• 3rd-5th level space boundaries are ignored
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2nd and 3rd level space boundaries
Space 005(#1415)
Space 001
Space 003
Space 004
Space 005(#1415)
Space 001Space 003
Space 004
Space boundary
Wall 010
Wall 011
Wall 004
Wall 001
Wall 012Gap due to the wall-butt-print
Source: IAI - Implementation guideline for 2nd level space boundaries 44
2nd Level space boundary
#1: interior to interior
2nd Level space
boundary #2
1st Level space
boundary #1:
interior to exterior
3nd Level space
boundary #1
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HVAC
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HVAC assumptions/simplifications
• No pressure is modeled
• Natural ventilation (simplified for now)
– ZoneVentilation object
• CV/VAV approximation
• AHU simplification (supply and return difference cannot
be modeled in E+)
• Main and tempered water loops are separate in E+ but
connected in reality
• Steam connection simplification (no heat exchanger
steam to hot water available in E+)
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HVAC air system – typical offices
CAV
Active beam
Zone 1
Active beam
Zone 2
AHU
Atrium
Cooling Coil
Cooling Coil Cooling Coil Heating Coil Heating Coil
Simplification for E+:
• E+ can only model
either CAV or
Active Beam
• Since air flow for
active beams is
constant this
assumption is
probably not
problematic
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AHU simplifications
Fan
Zone 1
Zone 2
ACB
ACB
Coil Plenum
Outside Air
Mixer
Coils
Heat Recovery
Outside
Simplification for E+:
• Closed loop
• Supply air flow = exhaust airflow
• Heat recovery efficiency needs
to be reduced
• Exhaust fan parameters adjusted Fan
Outside
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Steam supply simplification
District hot water
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Actual Model
To zone equipment To zone equipment
Main and tempered water loops
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Simplified analytical model for E+
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Update input
IDF Geometry
IDF Setpoints
Schedules
IDF HVAC
systems
IDF Controls
EPW Weather
file
Observed data
(Y2E2)
Predicted
data
Space Air Temp
Setpoint
Estimated plug
loads and lighting
Outside Air Temp
Wetbulb Temp or
Relative Humidity
Wind direction and
speed
Direct and diffuse
solar radiation
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Outputs: Annual (2009) Energy Use
0
1,000,000
2,000,000
3,000,000
4,000,000
5,000,000
6,000,000
7,000,000
8,000,000
9,000,000
10,000,000
COOLING ELECTRICTY HEATING
MEASURED SIMULATED
MJ
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Note: causes of
discrepancies not
yet understood
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Output: Monthly Energy Consumption
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
800,000
900,000
1,000,000
Jan 2009 Feb 2009 Mar 2009 Apr 2009 May 2009 Jun 2009 Jul 2009 Aug 2009 Sep 2009 Oct 2009 Nov 2009 Dec 2009
MEA-COOLING MEA-ELECTRICTY MEA-HEATING
SIM-COOLING SIM-ELECTRICTY SIM-HEATING
MJ
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Measured heating
inverse of cooling
Measured –
simulated gaps
Measured –
simulated gaps
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• complex processes associated with
analytical model development
• Current simulation tools require many
assumptions and work-arounds to
address current limitations
Big Ideas
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