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

Contents What is EnergyPlus? EnergyPlus capabilities Comparison with ESP-r A simulation tutorial Particular requests? 19/10/2009 2 2

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 19/10/2009 3 3

What is EnergyPlus? Modular and structured code 19/10/2009 4 EP consists of many modules organized in a hierarchical structure EP EngineeringReference 19/10/2009 4 4

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. 19/10/2009 5 5

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. 19/10/2009 6 6

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) 19/10/2009 7 7

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) 19/10/2009 8 8

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) 19/10/2009 9 9

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 19/10/2009 10 Crawley et al. (2005) 10

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 19/10/2009 11 Crawley et al. (2005) 11

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) 19/10/2009 12 12

Simulation tutorial An EnergyPlus simulation requires: An EnergyPlus Weather File (epw) An Input Data File (idf) 19/10/2009 13 13

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: http://apps1.eere.energy.gov/buildings/energyplus/cfm/weather_data.cfm 19/10/2009 14 14

Simulation tutorial Input Data File (idf) Simulation parameters Geometry Construction Internal gains Infiltration/ventilation Daylighting Schedules HVAC systems Passive systems Outputs 19/10/2009 15 15

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 ... 19/10/2009 16 16

Simulation tutorial Input Data File (idf) Geometry 19/10/2009 17 Zones Surfaces Windows Shading surfaces EP InputOutputReference 19/10/2009 17 17

Simulation tutorial Input Data File (idf) Construction 19/10/2009 18 Materials Air gaps Glazing Shading materials Constructions 19/10/2009 18 18

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. 19/10/2009 19 19

Simulation tutorial Input Data File (idf) Infiltration/Ventilation Infiltration flow rate, correlation. Natural ventilation correlation. Airflow network. Mechanical ventilation included in HVAC definition. 19/10/2009 20 20

Simulation tutorial Input Data File (idf) Daylighting 19/10/2009 21 Split-flux method or radiosity method. Reference points. Illuminance setpoints. Electric lighting control. 19/10/2009 21 21

Simulation tutorial Input Data File (idf) Schedules 19/10/2009 22 Internal gains schedules. Infiltration/ventilation schedule. HVAC schedules. 19/10/2009 22 22

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 ... 19/10/2009 23 23

Simulation tutorial Input Data File (idf) Passive systems 19/10/2009 Natural ventilation (airflow network). Earth tube. Ventilated-facades. Evaporative cooling. Green roof. ... 19/10/2009 24 24

Simulation tutorial Input Data File (idf) 19/10/2009 25 Outputs Outdoor air temperature Wall temperatures Wall CHTC Energy consumption .... 19/10/2009 25 25

Simulation tutorial Simulation run and output files Error file (err) Output file (csv) (eso) Output dictionary file (rdd) Building visualization (dxf) 19/10/2009 26 26

Particular requests? 19/10/2009 27 27

Merci de votre attention 28