1. EnergyPlus applied to urban climate studies
Bruno Bueno
Supervisor: Grégoire Pigeon 1

2. Contents What is EnergyPlus? EnergyPlus capabilities
Comparison with ESP-r
A simulation tutorial
Particular requests?
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3. What is EnergyPlus?
EP is a detailed building energy simulation program
It allows the calculation of:
Building energy demand: minimum heating and cooling energy necessary to maintain thermal control setpoints
System energy consumption: heating and cooling energy actually used by an HVAC system
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4. What is EnergyPlus? Modular and structured code 19/10/2009 4
EP consists of many modules organized in a hierarchical structure
EP EngineeringReference
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5. EnergyPlus capabilities
Summary
Heat balance based calculations.
Transfer function method for transient heat conduction through walls (less computationally expensive than the alternative finite difference method).
Specific models for HVAC systems, passive systems, and daylight.
Detailed models for external heat transfer calculations:
Convection.
Solar radiation, including shadows and reflections from other buildings.
LW radiation with the sky, including reduction of the SVF in an urban environment.
Integrated solution manager. Building and systems are solved simultaneously instead of sequentially.
Extensively evaluation according to building simulation standards.
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6. EnergyPlus capabilities
Limitation in the outdoor surface energy balance
EnergyPlus simplifies the calculation of longwave radiation between a building surface and the surrounding urban surfaces, assuming that the latter are at outdoor air temperature.
Differences with Urban Canopy Models
EnergyPlus uses a correlation that provides values of convective heat transfer coefficients one order of magnitude lower than UCM's correlations.
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7. Comparison with ESP-r Heat conduction through walls EP ESP-r
Transfer functions x
Finite differences
User-selectable outside surface convection algorithm
Crawley et al. (2005)
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8. Comparison with ESP-r Solar calculations, windows and daylighting EP
Insolation distribution computed each time-step x
Self –shading by adjacent zones
Diffuse and LW shading
Dirt correction factor for glass solar
Interior illumination from windows and skylights
Stepped or dimming electric lighting controls
User-specified daylighting control
Radiosity interior light interreflection calculation
Crawley et al. (2005)
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9. Comparison with ESP-r Indoor energy calculations EP ESP-r 19/10/2009 9
Heat balance calculation x
Floating room temperatures
Convection dependent on temperature, air-flow, user-selectable
Internal thermal mass
Inside radiation view factors
Building moisture absorption/desorption
Crawley et al. (2005)
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10. Comparison with ESP-r HVAC systems 19/10/2009 10 EP ESP-r
Simultaneous and coupled load, system, plant simulation x
Automatic sizing
Discrete HVAC components including part-load performance
Idealized HVAC systems
User-configurable HVAC systems, including main configurations: VAV, Fancoil, low-temperature radiant
Cooling tower; air-cooled condenser
Economizer
Water side economizer
Heat recovery
Domestic water heating
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Crawley et al. (2005) 10

11. Comparison with ESP-r Passive and renewable systems 19/10/2009 11 EP
Internal and external shading devices x
User-specified shading control
Movable insulation
Phase change materials
Building integrated photovoltaic system coupled with thermal
Natural ventilation; multizone airflow
Trombe wall
Ground heat exchanger
Solar thermal collectors
Green roof
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Crawley et al. (2005) 11

12. Comparison with ESP-r Other characteristics EP ESP-r 19/10/2009 12
Weather data processing and editing x
User-selectable report format
Extensive validation
Available source code
Open source license
Crawley et al. (2005)
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13. Simulation tutorial An EnergyPlus simulation requires:
An EnergyPlus Weather File (epw)
An Input Data File (idf)
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14. Simulation tutorial EnergyPlus Weather File (epw)
An epw file contains hourly values of meteorological variables for a typical meteorological year:
Air temperature, relative humidity, dew-point temperature.
Direct and diffuse solar radiation, incoming LW radiation.
Atmospheric pressure, wind speed and direction.
Presence of rain, snow, etc.
This typical meteorological year is derived from many years of hourly weather data measurements at meteorological stations (generally airports).
epw files can be downloaded from:
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15. Simulation tutorial Input Data File (idf) Simulation parameters
Geometry
Construction
Internal gains
Infiltration/ventilation
Daylighting
Schedules
HVAC systems
Passive systems
Outputs
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16. Simulation tutorial Input Data File (idf) Simulation parameters
Location, type of terrain, building orientation
Convergence tolerance values
Timestep
Solar distribution, convection algorithms,
heat conduction algorithm
Run period
...
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17. Simulation tutorial Input Data File (idf) Geometry 19/10/2009 17 Zones
Surfaces
Windows
Shading surfaces
EP InputOutputReference
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18. Simulation tutorial Input Data File (idf) Construction 19/10/2009 18
Materials
Air gaps
Glazing
Shading materials
Constructions
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19. Simulation tutorial Input Data File (idf) Internal gains 19/10/2009 19
People: latent fraction, radiant fraction, activity.
Lights: radiant fraction, Watts per zone area.
Equipment: radiant fraction, Watts per zone area.
Other equipment.
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20. Simulation tutorial Input Data File (idf) Infiltration/Ventilation
Infiltration flow rate, correlation.
Natural ventilation correlation.
Airflow network.
Mechanical ventilation included in HVAC definition.
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21. Simulation tutorial Input Data File (idf) Daylighting 19/10/2009 21
Split-flux method or radiosity method.
Reference points.
Illuminance setpoints.
Electric lighting control.
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22. Simulation tutorial Input Data File (idf) Schedules 19/10/2009 22
Internal gains schedules.
Infiltration/ventilation schedule.
HVAC schedules.
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23. Simulation tutorial Input Data File (idf) HVAC systems 19/10/2009 23
Thermal setpoints.
Mechanical ventilation.
Type of cooling system.
Type of heating system.
Energy efficiency strategies:
Economizers
Heat recovery
...
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24. Simulation tutorial Input Data File (idf) Passive systems 19/10/2009
Natural ventilation (airflow network).
Earth tube.
Ventilated-facades.
Evaporative cooling.
Green roof.
...
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25. Simulation tutorial Input Data File (idf) 19/10/2009 25 Outputs
Outdoor air temperature
Wall temperatures
Wall CHTC
Energy consumption
....
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26. Simulation tutorial Simulation run and output files Error file (err)
Output file (csv) (eso)
Output dictionary file (rdd)
Building visualization (dxf)
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27. Particular requests?
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28. Merci de votre attention28