BUILDING ENERGY PERFORMANCE MODELLING AND SIMULATION 4

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1 BUILDING ENERGY PERFORMANCE MODELLING AND SIMULATION 4 125BEPM,MEB,MEC prof.karel Kabele 27 When to use simulation in building energy performance analysis? Early phase of building conceptual design to predict energy performance of the alternative solutions to support designer decision process (building shape, initial facade and shading, HVAC concept) Modeling non-standard building elements and systems (double-facade, atrium, natural ventilation, renewables, solar technologies, intgrated HVAC systems) Investigation of the operational breakdowns and set-up of control systems (HVAC, adaptive control, self-learning systems, ) Indoor environment quality prediction (temperatures, air flow patterns, PMV,PPD) Analysis of energy saving measures to energy use Operation cost calculation and consequently cost distribution among users at multiuser single meter buildings 125BEPM,MEB,MEC prof.karel Kabele 29 1

2 Considerations for program selection Program documentation Ease of use Compatibility with other packages Flexibility Available support Existence of user forums for exchange of experiences Validity of the program Use approval 125BEPM,MEB,MEC prof.karel Kabele (IEA 1994, ASHRAE Handbook 2009) 30 Considerations for program selection Existence of application examples similar to those for which it is required Guidance for its use when carrying out specific performance assessments Sensitivity Versatility Cost of program Speed and cost of analysis Ease of use 125BEPM,MEB,MEC prof.karel Kabele (IEA 1994, ASHRAE Handbook 2009) 31 2

3 Basic principle of modelling and simulation approach Problem analysis identification of the zones, systems,plant components and their dependencies Assignment definition Boundary condition definition Definition of detail scale and model range Proper tool selection Sensitivity analysis Results validation Virtual laboratory is not design tool 125BEPM,MEB,MEC prof.karel Kabele 32 Typical modeling procedure Set out detailed procedure Create reference model and select design alternatives Iterative process Simulate / Analyse QA checks on results Create new / revised model(s) Design team meeting Check assumptions Discuss details Define new / refined objects Revise reference model? No Analyse additional design alternatives? No Report (CIBSE 1998) 125BEPM,MEB,MEC prof.karel Kabele Figure courtesy of CIBSE, 33 Yes Yes 3

4 Accuracy External errors Internal errors Improper use of the program (user mistakes and misinterpretation) Weaknesses inherent in the program itself Follow Good Practice principles User friendly interface Good quality input databases Validated and Tested program Program sensitive to the design options considered 125BEPM,MEB,MEC prof.karel Kabele 34 Good practice principles (QA) for Software users I. Document modeling assumptions and the procedures used and approaches taken to generate and evolve the model II. III. IV. Perform Good Housekeeping (regular back-up and effective archiving) Set up an error log book and document each and every error found Always check the input files thoroughly V. Always carry out a test run and look for unexpected results; if routine checks are available use these to identify possible errors VI. VII. If possible, have a second person check the work carried out Create a database of results from previous projects to be used for comparison VIII. For frequently used materials and components, create databases IX. Give logical and meaningful names to input parameters (e.g. operation schedule, zoning etc) X. Give logical and meaningful names to simulation files with different parameter testing or iteration (e.g. operation schedule, zoning etc) (IEA 1994) 125BEPM,MEB,MEC prof.karel Kabele 37 4

5 Building simulation sw ESP-R 125BEPM,MEB,MEC prof.karel Kabele 38 ESP-r ESP-r (Environmental Systems Performance; r for research ) Dynamic, whole building simulation finite volume, finite difference sw based on heat balance method. Academic, research /non commercial Developed at ESRU, Dept.of Mech. Eng. University of Strathclyde, Glasgow, UK by prof. Joseph Clarke and his team since 1974 ESP-r is released under the terms of the GNU General Public License. It can be used for commercial or noncommercial work subject to the terms of this open source licence agreement. UNIX, Cygwin, Windows 125BEPM,MEB,MEC prof.karel Kabele 39 5

6 Databases maintenace Climate Material Construction Plant components Event profiles Optical properties 125BEPM,MEB,MEC ESP-r architecture Model editor Zones Networks Plant Vent/Hydro Electrical Contamina nts Controls Project manager Simulation controler Timestep Save level From -To Results file dir Monitor Results analysis Graphs Timestep rep. Enquire about Plant results IEQ Electrical CFD Sensitivity IPV prof.karel Kabele 40 ESP-r interface 125BEPM,MEB,MEC prof.karel Kabele 41 6

7 Case study LOW - ENERGY OFFICE BUILDING 125BEPM,MEB,MEC prof.karel Kabele 42 Case Study Description Architect s request: low-energy sustainable office building comfort indoor environment office rooms for 1-3 persons, oriented south-north Architect s question: What is the best U-value for building envelope??? 125BEPM,MEB,MEC prof.karel Kabele 43 7

8 Case Study Description Czech building regulations Building envelope requirements Alternative U wall [W/m 2 K] U window [W/m 2 K] 1 DEM (Demanded) 0,38 1,7 2 REC (Recommended) 0,25 1,2 3 LE (Low-energy) 0,15 0,8 Indoor environment requirements Indoor resultant temperature winter C summer C Relative humidity 30-70% 125BEPM,MEB,MEC prof.karel Kabele 44 ESP-r 3 zones model 2 office rooms 4 x 6 x 3 m Corridor 2 x 6 x 3 m Computer modelling Heating and cooling system heating 0-500W, cooling W mix of 75 % convection, 25% radiation pre-heat and pre-cool controller sensing mix of zone db temperature and MRT set points: heating 20 C; cooling 26 C Ventilation system working hours 1 ac/hr non-working hours 0,2 ac/hr Casual gains (working time 8-17) Occupancy 140 W/per Equipment 200W/comp Lighting (500 lx): 35 W / m 2 Fig. 3. ESP-r model of the building 125BEPM,MEB,MEC prof.karel Kabele 45 8

9 kwh/a Te [ C] kwh/a Simulation Annual simulation in Czech climate conditions Building energy and environmental performance BEPM,MEB,MEC prof.karel Kabele 46 Results Annual energy consumption Potřeba energie na vytápění ,72 79, , ,24 32, , Jih Sever Office HEATING SOUTH NORTH Nízkoenergetická Doporučená Požadovaná Potřeba energie na chlazení COOLING Jih SOUTH Sever NORTH Nízkoenergetická Doporučená Požadovaná DEManded RECommended Low-Energy 125BEPM,MEB,MEC prof.karel Kabele 47 9

10 kwh/a 00h30 06h30 12h30 18h30 00h30 06h30 12h30 18h30 00h30 06h30 12h30 18h30 00h30 06h30 12h30 18h30 00h30 06h30 12h30 Results Total energy consumption Roční potřeba energie na vytápění a chlazení ANNUAL ENERGY CONSUMPTION LE REC DEM Nízkoenergetická Doporučená Požadovaná Chlazení Cooling Heating Vytápění 125BEPM,MEB,MEC prof.karel Kabele 48 Indoor temperature Tair max Results Alternative Room 1 Corridor Room 2 LE 27,52 30,84 29,08 DEM 27,54 30,78 29,08 REC 27,76 30,79 29, Temperatures Řa Řa Řa Tair min Alternative Room 1 Corridor Room 2 LE 19,07 18,92 19,11 DEM 19,07 18,66 19,19 REC 19,01 18,81 19,12 Tair Room 1 Tair Room2 Te 125BEPM,MEB,MEC prof.karel Kabele 49 10

11 IEQ analysis Annual distribution of PMV during working time according to ČSN EN ISO 7730 Comfort -0,5<PMV<0,5 Acceptable -1<PMV<1 Discomfort PMV<-1 or PMV>1 Results 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% LE DEM REC Comfort 9,7% 16,9% 15,6% Acceptable 44,3% 40,5% 41,3% Discomfort 46% 43% 43% 125BEPM,MEB,MEC prof.karel Kabele 50 Conclusion Presented case study has shown a possible utilization of integrated simulation supporting the early conceptual design phase The recommendation based on this approach is to continue in designing alternative DEM - demanded U-values The reason, why the results of the thermal comfort evaluation are so unsatisfactory (more than 40% of working time is PMV>1) is due to the relatively high summer temperature set point (+26 C) in connection with settled clothing value and activity of the occupants. 125BEPM,MEB,MEC prof.karel Kabele 51 11

12 Case study LOW-ENERGY BUILDING ENERGY SYSTEM MODELLING 125BEPM,MEB,MEC prof.karel Kabele 53 Introduction Low Energy Buildings? < 50 kwh/m 2 /a perfect thermal insulation of the building envelope design and control of heating systems warm-air heating systems. solar energy utilisation long-term energy accumulation How to design? 125BEPM,MEB,MEC prof.karel Kabele 54 12

13 Low Energy Building Architectural concept Zoning Greenhouse Thermal insulation Air tightness of the envelope Energy system concept Controlled ventilation Warm-air air heating Solar energy utilisation 125BEPM,MEB,MEC prof.karel Kabele 55 Principles of solar energy utilisation Active solar water collectors Passive solar gains via glazed balconies Gains from greenhouse midterm accumulation into the gravel accumulator below the building. 125BEPM,MEB,MEC prof.karel Kabele 56 13

14 Midterm solar energy accumulation Greenhouse air warming up Loading of the accumulator Unloading of the accumulator Additional heat source 125BEPM,MEB,MEC prof.karel Kabele 57 Problem description Boundary conditions Geometry Climate Fresh air volume Required output of the system Optimisation criterions Annual energy consumption Output of the additional heat source 125BEPM,MEB,MEC prof.karel Kabele 58 14

15 Modelling of energy performance Energy system Modelling tool selection criterions Dynamic modelling Heat transfer coefficients ESP-r, TRNSYS Model in ESP-r Zonal model describing building and energy system why 2 models? Building + 125BEPM,MEB,MEC prof.karel Kabele 59 Building model Input: 10 zones, construction, shading elements, operational schedule 125BEPM,MEB,MEC prof.karel Kabele 60 15

16 ESP-r model HVAC system divided into 5 thermal zones roof air solar collector greenhouse air solar collector gravel heat accumulator heat exchanger air heater Model of active solar system with mid-term heat accumulation 125BEPM,MEB,MEC prof.karel Kabele 61 Simulation Climate database: Test reference year Time period 1 year Time step of the output 1 hour Time step of the calculation 1 minute Building: What? Energy demand for heating How? 1x simulation loop Output: Heating output Energy system What? Annual energy consumption How? Virtual experiments Loading air variation Accumulation mass of the gravel Output? Design of the elements 125BEPM,MEB,MEC prof.karel Kabele 62 16

17 Simulation results Annual energy consumption Heating energy consumption impact of accumulator 100% = 11,4MWh =410EUR/year 120% 100% 80% 60% 40% 20% 0% 100% 56% 52% 53% 47% 47% Virtual experiment Nr. 44% Virtual experiment 0 without accumulator 1-3 change of the loading air volume 100 to 2000 m 3 /h 4-6 change of gravel mass 50 to180 t Energetický systém Temperature in the accumulator 125BEPM,MEB,MEC prof.karel Kabele 63 Conclusions Virtual experiments confirmed that use of preheating of fresh air supply in gravel accumulator, located below the building contributes positively into the energy balance. Use of simple preheating of fresh air supply in gravel accumulator decreases annual energy consumption for ventilation air to approx. 50%. Virtual experiments did not confirm significant influence of design parameters to the collecting and accumulating of solar energy in simulated configuration of collectors and accumulator size. The solar energy contribution is in this case very small and most of the accumulator energy gain is given by relative constant earth temperature below the building. In all of simulated virtual experiments was the accumulator mass temperature during the year in the range 12 C to 16 C 125BEPM,MEB,MEC prof.karel Kabele 64 17