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”.
bsdsolutions.com
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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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