University of Liège Faculty of Applied Sciences Thermodynamics Laboratory Workshop “Commissioning and Auditing of Buildings and HVAC Systems” Use of a Global Building-HVAC System Model for Audit Stéphane BERTAGNOLIO Brussels, January 28, 2008

UNIVERSITY OF LIEGE Faculty of Applied Sciences January 28, 2008Commissioning and Auditing of Buildings and HVAC Systems Content Introduction Contribution to audit Modelling Example of use Conclusion

UNIVERSITY OF LIEGE Faculty of Applied Sciences January 28, 2008Commissioning and Auditing of Buildings and HVAC Systems Content Introduction Contribution to audit Modelling Example of use Conclusion

UNIVERSITY OF LIEGE Faculty of Applied Sciences January 28, 2008Commissioning and Auditing of Buildings and HVAC Systems Introduction Starting audit : experimental identification of building heating, cooling and electricity consumptions almost impossible For auditor : difficult to differentiate chiller, pumps, fans, lighting and appliances consumptions  Calculation Method to characterize the audited system Important number of parameters  Rational to use simulation tools rather than global weather indexes Global Building-HVAC system model implemented on EES (Klein, F-Chart Software) Work began in the frame of “AUDITAC” and is continued in the frame of “HARMONAC – WP7”

UNIVERSITY OF LIEGE Faculty of Applied Sciences January 28, 2008Commissioning and Auditing of Buildings and HVAC Systems Content Introduction Contribution to audit Modelling Example of use Conclusion

UNIVERSITY OF LIEGE Faculty of Applied Sciences January 28, 2008Commissioning and Auditing of Buildings and HVAC Systems Contribution to audit Audit  global data  What is Good, Bad or Average performance ? Useful to have benchmarks used as reference to analyse current performances of the audited building Comparison with current consumptions to identify main energy consumers, energy waste and energy saving potentials Realistic considerations : Building behaviour Weather and occupancy loads Comfort requirements Full HVAC system Simulation tool adapted to the needs of auditor  limited number of parameters (envelope, type of HVAC system, …) General tool, not adapted to highlight very specific retrofit opportunities BUT including a large range of HVAC systems

UNIVERSITY OF LIEGE Faculty of Applied Sciences January 28, 2008Commissioning and Auditing of Buildings and HVAC Systems Content Introduction Contribution to audit Modelling Example of use Conclusion

UNIVERSITY OF LIEGE Faculty of Applied Sciences January 28, 2008Commissioning and Auditing of Buildings and HVAC Systems Modelling overview Two main parts : Dynamic Building model and Static HVAC system model Audit  Simplified Model : unique zone with a global HVAC system Compromise between number of influences and simplicity  main phenomena : Envelope and structure dynamic behaviour Internal generated gains Solar gains Infrared losses Ventilation and Heating/Cooling devices

UNIVERSITY OF LIEGE Faculty of Applied Sciences January 28, 2008Commissioning and Auditing of Buildings and HVAC Systems Building Model Mono-zone model based on R-C network R-C “two-port” network parameters adjusted trough frequency characteristic analysis Simplified model  default values are proposed and only general data are asked (U-values, type of thermal mass, …) Calculation of indoor conditions : Temperature, Humidity, CO 2 contamination and comfort indexes PMV/PPD

UNIVERSITY OF LIEGE Faculty of Applied Sciences January 28, 2008Commissioning and Auditing of Buildings and HVAC Systems HVAC system model Classical components of AHU and TU TU : Heating and/or Cooling fan or induction terminal units AHU : AHU components models : recovery system, coils, fans, … Many values are proposed by default (components effectivenesses and pressure drops) or automatically computed (sizing powers)

UNIVERSITY OF LIEGE Faculty of Applied Sciences January 28, 2008Commissioning and Auditing of Buildings and HVAC Systems Control and Plant Simple Proportional control laws chiller and boiler models based on correlations established using physical reference models

UNIVERSITY OF LIEGE Faculty of Applied Sciences January 28, 2008Commissioning and Auditing of Buildings and HVAC Systems Outputs, Inputs & Parameters Main outputs Indoor conditions Global power and energy consumptions HVAC components specific demands Performances of equipments : COP, efficiencies Main Inputs Weather (hourly values) Nominal occupancy loads and occupancy rates Comfort requirements Control laws Main parameters Dimensions, orientation and characteristics of the building envelope HVAC system components actually installed Sizing factors of main HVAC components

UNIVERSITY OF LIEGE Faculty of Applied Sciences January 28, 2008Commissioning and Auditing of Buildings and HVAC Systems Content Introduction Contribution to audit Modelling Example of use Conclusion

UNIVERSITY OF LIEGE Faculty of Applied Sciences January 28, 2008Commissioning and Auditing of Buildings and HVAC Systems Example of use Typical office building Floor area m² 10 floors N/S oriented Two 50% glazed facades Two opaque facades 1000 occupants Medium thermal mass HVAC System CAV Electrical steam hum. H/C Fan coils terminal units Improvements Improved HVAC system Improved building envelope

UNIVERSITY OF LIEGE Faculty of Applied Sciences January 28, 2008Commissioning and Auditing of Buildings and HVAC Systems Simulation results Original Installation  Theoritical consumptions ? Heat : 600 MWh ~ m³ Cool : 520 MWh ~ 160 Mwhe (8%) Elec : 1970 MWhe Auxiliaries : 23% Elec Steam Hum : 15% Appl and Lighting : 53 % Improved HVAC System  Results ? Recovery  Heat : 300 MWh and Elec : 2025 MWhe Adiabatic Hum  Heat : 600 MWh and Elec : 1700 Mwhe Improved building envelope  Results ? Heat : 470 MWh ~ m³ Cool : 620 MWh ~ 190 Mwhe (10%) Elec : 2035MWhe

UNIVERSITY OF LIEGE Faculty of Applied Sciences January 28, 2008Commissioning and Auditing of Buildings and HVAC Systems Simulation results Temperature profiles Heating / Cooling Demands Electrical Power Demands

UNIVERSITY OF LIEGE Faculty of Applied Sciences January 28, 2008Commissioning and Auditing of Buildings and HVAC Systems Content Introduction Contribution to audit Modelling Example of use Conclusion

UNIVERSITY OF LIEGE Faculty of Applied Sciences January 28, 2008Commissioning and Auditing of Buildings and HVAC Systems Conclusion Simulation tool Dynamic R-C building model Static HVAC system model composed of simplified HVAC components models Fully transparent and implemented on EES Helpful for the auditor : To allow comparison between current performances and benchmarks To differentiate and evaluates the different consumers (chiller, fans, pumps, lighting, appliances,…) To identify over-consumptions, energy waste and energy saving potentials Limited quantity of parameters and use of automatically computed or default values Future Additional HVAC components : heating floor, cooling ceiling, … Additional physical phenomena : hygroscopy ? To reduce the number of default values by means of additional sizing calculations…