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 Slide: 2/20 28/01/2011

1/4 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. Slide: 4/20 28/01/2011

2/4 Model description

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. Overview DOE 2010 Slide: 6/20 28/01/2011

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 part- load 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 Slide: 7/20 28/01/2011

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. DOE 2010 Slide: 8/20 28/01/2011 INDOOR

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. Building model physics pic2 Slide: 9/20 28/01/2011

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. environmaster.com Slide: 10/20 28/01/2011

HVAC system physics Energy consumed by the system Waste heat emissions Sensible and latent waste heat split Type of condenser : Air condenser Sensible waste heat. Water condenser Latent waste heat. home.howstuffworks.com Slide: 11/20 28/01/2011

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. Effect on the outdoor energy balance pic2 Slide: 12/20 28/01/2011

3/4 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 N Adaptation of the building/shading morphology to the TEB parameters Building Shading Slide: 14/20 28/01/2011

Statistical comparison BEM - EP Annual Root Mean Square Error VariableRMSE Indoor wall temperature0.33 K Floor surface temperature0.28 K Ceiling surface temperature0.74 K Mass surface temperature0.31 K Indoor air temperature0.23 K Solar heat transmission18.78 W/m 2 (bld) Building cooling energy demand8.26 W/m 2 (bld) Building heating energy demand4.41 W/m 2 (bld) Slide: 15/20 28/01/2011

Graphical comparison BEM - EP Slide: 16/20 28/01/2011 Indoor air temperature Indoor air specific humidity Mass surface temperature Monthly averaged diurnal cycle in summer(15/07-15/08) and in winter(15/01-15/02).

Graphical comparison BEM - EP Slide: 17/20 28/01/2011 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

4/4 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. Slide: 19/20 28/01/2011

Merci

Model inputs. 21 Building inputs Symbol Example Internal heat gain: 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 = J m-3 K-1

Model inputs. 22 HVAC inputs Symbol Example Fraction of waste heat released into the canyon: F_WASTE_CAN = 0.5 Cooling setpoint: TCOOL_TARGET = 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 = K Minimum outdoor air temperature for sizing calcs: T_SIZE_MIN = 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 = W m-2 Rated cooling system air flow rate: M_SYS_RAT = kg s-1 m-2 Cooling coil apparatus dew-point: T_ADP = K Heating setpoint: THEAT_TARGET = 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

HVAC system Sensible and latent waste heat split In BEM, the user selects the type of condenser of the HVAC system: Air condensed Sensible waste heat. Water condensed Latent waste heat. 23 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/ /08). Case study corresponding to the experiment carried out in Toulouse between Feb and Feb (CAPITOUL).