Development of a new Building
Energy Model in TEB
Bruno Bueno
Grégoire Pigeon
Contents
1. Objective
2. Model description
3. Simulation-based model evaluation
4. Next steps
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Objective
Objective
•
Combine the knowledge accumulated in building energy and urban climate studies
to investigate the interactions between buildings and the urban environment.
•
Develop a building energy model (BEM) to integrate these interactions into TEB.
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Model description
Overview
Building energy model
Calculates the building energy demand.
Multi-storey buildings are represented by an internal thermal mass.
The model includes:
Solar radiation through windows
Heat storage in building structure.
Heat conduction through the enclosure
Infiltration and ventilation.
Internal heat gains.
DOE 2010
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Overview
Heating, Ventilation, Air-Conditioning (HVAC) energy model
Calculate building energy consumption and waste heat emissions.
Two options:
•
•
Ideal HVAC system
Infinite capacity and constant efficiency.
The system supplies the required energy to meet the sensible and latent building demand.
Real HVAC system
The system capacity and efficiency depend on indoor conditions, outdoor conditions, and partload performance.
The model solves the latent energy balance of the building and calculates indoor air humidity.
It calculates fan energy consumption.
System parameters can be “autosized”.
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Building model physics
Indoor surface energy balance
Heat balance method.
Separation between convection and radiation heat components. .
Calculation of view factors between indoor surfaces.
Transient heat conduction through massive materials.
Steady-state heat conduction through windows.
Solar transmitted is initially absorbed by the thermal mass.
INDOOR
DOE 2010
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Building model physics
Indoor air energy balance
•
Calculates the dynamic evolution of air temperature and air humidity.
•
Calculates sensible and latent building energy demand
•
The sensible and latent energy balances are composed of:
–
Convection from indoor surfaces.
–
Internal heat gains.
–
Infiltration/ventilation.
–
HVAC system .
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HVAC system physics
Energy supplied by the system
Two options:
•
Ideal HVAC system
Supply energy is the same as the energy demand of the building.
•
Real HVAC system
Model calculations at each timestep:
•
System capacity.
•
Supply air temperature.
•
Supply air humidity:
•
Cooling: air dehumidification.
•
Heating: no air dehumidification.
•
Supplied energy.
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HVAC system physics
Energy consumed by the system
Qconsumed,cool = Qsupplied,cool / COP
Qconsumed,heat = Qsupplied,heat / heat
Waste heat emissions
Qwaste,cool = Qsupplied,cool +Qconsumed ,cool
Qwaste,heat = Qconsumed ,heat Qsupplied,heat
Sensible and latent waste heat split
Type of condenser :
•
Air condenser
•
Water condenser
Sensible waste heat.
Latent waste heat.
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Effect on the outdoor energy balance
The original TEB outdoor energy balance is now affected by:
•
Waste heat emissions from the HVAC system.
•
Infiltration/ventilation from the building.
•
Effect of windows on solar reflections, heat storage, convection and radiation heat exchange.
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Simulation-based model
evaluation
Simulation-based model evaluation
Evaluation of BEM indoor energy performance
•
Comparison between BEM and an equivalent
building energy model defined in EnergyPlus.
•
Case study corresponding to the experiment
CAPITOUL carried out in Toulouse between
Feb 2004 and Feb 2005.
N
Building
Shading
Adaptation of the building/shading
morphology to the TEB parameters
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Statistical comparison BEM - EP
Annual Root Mean Square Error
Variable
RMSE
Indoor wall temperature
0.33 K
Floor surface temperature
0.28 K
Ceiling surface temperature
0.74 K
Mass surface temperature
0.31 K
Indoor air temperature
0.23 K
Solar heat transmission
18.78 W/m2 (bld)
Building cooling energy demand
8.26 W/m2 (bld)
Building heating energy demand
4.41 W/m2 (bld)
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Graphical comparison BEM - EP
Monthly averaged diurnal cycle in summer(15/07-15/08) and in winter(15/01-15/02).
Indoor air temperature
Indoor air specific humidity
Mass surface temperature
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Graphical comparison BEM - EP
Monthly averaged diurnal cycle in summer(15/07-15/08) and in winter(15/01-15/02).
Cooling energy demand
Cooling energy consumption
Heating energy demand
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Next steps
Next steps
•
Evaluate BEM-TEB with field data.
•
Introduce a selection of passive and active building systems into BEM
Examples: solar protections, natural ventilation, heat recovery, economizer, VAV
systems.
•
Use the building data-base provided by CSTB to:
•
Create urban covers with different model inputs for different urban configurations.
•
Simulate these urban covers for present and future climates.
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Merci
Model inputs
.
Building inputs
Internal heat gain:
Symbol
Example
QIN
= 5.05 W m-2
Radiant fraction of internal heat gain: QIN_FRAD
= 0.2
Latent fraction of internal heat gain:
QIN_FLAT
= 0.2
Window Solar Heat Gain Coefficient:
SHGC
= 0.78
Window U-factor:
U_WIN
= 0.2 W m-2 K-1
Facade glazing ratio:
GR
= 0.3
Floor height:
FLOOR_HEIGHT = 3.0 m
Infiltration air flow rate:
INF
= 0.7 ACH
Ventilation air flow rate:
V_VENT
= 0.0 ACH
Mass and floor layer thickness:
D_FLOOR
= 0.1 m
Mass and floor layer conductivity:
TC_FLOOR
= 1.15 W m-1 K-1
Mass and floor layer capacity:
HC_FLOOR
= 1580000 J m-3 K-1
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Model inputs
. HVAC inputs
Symbol
Example
Fraction of waste heat released into the canyon:
F_WASTE_CAN
= 0.5
Cooling setpoint:
TCOOL_TARGET = 300.16 K
Relative humidity setpoint:
HR_TARGET
= 0.5
Flag to autosize the HVAC system:
AUTOSIZE
= .F.
Maximum outdoor air temperature for sizing calcs: T_SIZE_MAX
= 302.05K
Minimum outdoor air temperature for sizing calcs:
T_SIZE_MIN
= 268.96 K
Rated COP of the cooling system:
COP_RAT
= 2.5
Type of cooling coil:
HCOOL_COIL
= 'DXCOIL'
Type of condenser:
HCOOL_COND
= 'AIR'
Rated cooling system capacity:
CAP_SYS_RAT
= 125.0 W m-2
Rated cooling system air flow rate:
M_SYS_RAT
= 0.0069 kg s-1 m-2
Cooling coil apparatus dew-point:
T_ADP
= 285.66 K
Heating setpoint:
THEAT_TARGET
= 292.16
Type of heating coil
HHEAT_COIL
= 'IDEAL'
Heating system capacity:
CAP_SYS_HEAT
= 100 W m-2
Efficiency of the heating system:
EFF_HEAT
= 0.9
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HVAC system
Sensible and latent waste heat split
In BEM, the user selects the type of condenser of the HVAC system:
•
Air condensed
•
Water condensed
Sensible waste heat.
Latent waste heat.
Outdoor urban air temperature
•
•
•
Outdoor urban air specific humidity
Difference between an air-condensed and a water-condensed system.
Monthly averaged diurnal cycle in summer (15/07 - 15/08).
Case study corresponding to the experiment carried out in Toulouse between Feb. 2004
and Feb. 2005 (CAPITOUL).
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