EnergyPlus applied to urban climate studies

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

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

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 19/10/2009 3

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

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. 19/10/2009 5

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. 19/10/2009 6

7. Comparison with ESP-r Heat conduction through walls Crawley et al. (2005) 19/10/2009 7

8. Comparison with ESP-r Solar calculations, windows and daylighting Crawley et al. (2005) 19/10/2009 8

9. Comparison with ESP-r Indoor energy calculations Crawley et al. (2005) 19/10/2009 9

10. Comparison with ESP-r HVAC systems 19/10/2009 10 Crawley et al. (2005)

11. Comparison with ESP-r Passive and renewable systems 19/10/2009 11 Crawley et al. (2005)

12. Comparison with ESP-r Other characteristics Crawley et al. (2005) 19/10/2009 12

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

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

15. 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

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 • ... 19/10/2009 16

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

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

19. Simulation tutorial Input Data File (idf) • Internal gains • 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

20. 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

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

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

23. Simulation tutorial Input Data File (idf) • HVAC systems • Thermal setpoints. • Mechanical ventilation. • Type of cooling system. • Type of heating system. • Energy efficiency strategies: • Economizers • Heat recovery • ... 19/10/2009 23

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

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

26. 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

27. Particular requests? 19/10/2009 27

28. Merci de votre attention