building energy performance modelling and simulation 4

1

2012/2013

© ČVUT v Praze, FSv K125 prof.Kabele

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


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2012/2013


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

(IEA 1994, ASHRAE Handbook 2009) 125BEPM,MEB,MEC 30 prof.Karel Kabele

Considerations for program selection

(IEA 1994, ASHRAE Handbook 2009)

• 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 31 prof.Karel Kabele

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2012/2013


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…“


Iterative process

Set out detailed procedure

Create reference model and select design alternatives

Simulate / Analyse

QA checks on results

Design team meeting

Check assumptions Discuss details

Define new / refined objects

Revise reference model?

Analyse additional design alternatives?

Report

Create new / revised model(s)

Yes

Yes

No

No

Typical modeling procedure Typical modeling procedure

(CIBSE 1998) Figure courtesy of CIBSE, www.cibse.org 125BEPM,MEB,MEC 33 prof.Karel Kabele

http://www.cibse.org/

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2012/2013


Accuracy

External errors

Improper use of the program (user mistakes and misinterpretation)

Internal errors

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


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. Perform Good Housekeeping (regular back-up and effective archiving)

III. Set up an error log book and document each and every error found

IV. 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. If possible, have a second person check the work carried out

VII. 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 37 prof.Karel Kabele

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2012/2013


ESP-R Building simulation sw


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 non-commercial work subject to the terms of this open source licence agreement.

• UNIX, Cygwin, Windows

prof.Karel Kabele 39

http://www.esru.strath.ac.uk/

125BEPM,MEB,MEC

6

2012/2013


ESP-r architecture

prof.Karel Kabele 40

Project manager

Climate

Material

Construction

Plant components

Event profiles

Optical properties

Databases maintenace

Model editor

Zones

Networks •Plant •Vent/Hydro •Electrical •Contaminants

Controls

Simulation controler

Results analysis

•Timestep •Save level •From -To •Results file dir •Monitor •…

•Graphs •Timestep rep. •Enquire about •Plant results •IEQ •Electrical •CFD •Sensitivity •IPV

125BEPM,MEB,MEC

ESP-r interface


7

2012/2013


LOW - ENERGY OFFICE BUILDING

Case study


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 ???


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2012/2013


Case Study Description


Czech building regulations Building envelope requirements

Indoor environment requirements

Indoor resultant temperature

winter 18-24 °C

summer 20-28 °C

Relative humidity 30-70%

Alternative U wall

[W/m2K]

U window

[W/m2K]

1 DEM (Demanded) 0,38 1,7

2 REC (Recommended) 0,25 1,2

3 LE (Low-energy) 0,15 0,8

Computer modelling

Fig. 3. ESP-r model of the building

Fig. 3. ESP-r model of the building


• ESP-r 3 zones model • 2 office rooms 4 x 6 x 3 m

• Corridor 2 x 6 x 3 m

• Heating and cooling system • heating 0 - 500W,

• cooling 0 - 2500W

• 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 / m2

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2012/2013


Simulation


-20

-10

0

10

20

30

40

1

408

815

1222

1629

2036

2443

2850

3257

3664

4071

4478

4885

5292

5699

6106

6513

6920

7327

7734

8141

8548

Te

[°C

]

-20

-10

0

10

20

30

40

1

408

815

1222

1629

2036

2443

2850

3257

3664

4071

4478

4885

5292

5699

6106

6513

6920

7327

7734

8141

8548

Te

[°C

]

• Annual simulation in Czech climate conditions

• Building energy and environmental performance

Results

DEMandedDEManded

RECommendedRECommended

LowLow--EnergyEnergy


Annual energy consumption

Potřeba energie na chlazení

-8261

-5479

-7733

-5005

-7078

-4457

-9000

-8000

-7000

-6000

-5000

-4000

-3000

-2000

-1000

0

Jih Sever

kWh/a

Nízkoenergetická Doporučená Požadovaná

COOLING

SOUTH NORTH

Potřeba energie na vytápění

22,41

69,45

32,24

79,89

32,12

85,72

0

10

20

30

40

50

60

70

80

90

100

Jih Sever

kWh/a


HEATING

SOUTH NORTH Office

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2012/2013


Results • Total energy consumption

CoolingCooling

HeatingHeating


Roční potřeba energie na vytápění a chlazení

10000

10500

11000

11500

12000

12500

13000

13500

14000

14500


kWh/a

Chlazení Vytápění

ANNUAL ENERGY CONSUMPTION

LE REC DEM

Results • Indoor temperature

Temperatures

-20

-10

0

10

20

30

40

00

h3

0

06

h3

0

12

h3

0

18

h3

0

00

h3

0

06

h3

0

12

h3

0

18

h3

0

00

h3

0

06

h3

0

12

h3

0

18

h3

0

00

h3

0

06

h3

0

12

h3

0

18

h3

0

00

h3

0

06

h3

0

12

h3

0

Řada1

Řada2

Řada4Alternative Room 1 Corridor Room 2

LE 27,52 30,84 29,08

DEM 27,54 30,78 29,08

REC 27,76 30,79 29,05


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 max

Tair min Tair Room 1Tair Room 1

Tair Room2Tair Room2

TeTe

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2012/2013


Results

• 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


0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Comfort 9,7% 16,9% 15,6%

Acceptable 44,3% 40,5% 41,3%

Discomfort 46% 43% 43%

LE DEM REC

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.


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2012/2013


LOW-ENERGY BUILDING ENERGY SYSTEM MODELLING

Case study


Introduction

• Low Energy Buildings ? < 50 kWh/m2/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?


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2012/2013


Low Energy Building


ArchitecturalArchitectural conceptconcept ZoningZoning

GreenhouseGreenhouse

Thermal insulationThermal insulation

Air tightness of the envelopeAir tightness of the envelope

Energy system conceptEnergy system concept –– Controlled ventilationControlled ventilation

–– WarmWarm--air heatingair heating

–– Solar energy utilisationSolar energy utilisation


Principles of solar energy Principles of solar energy utilisationutilisation

Active solar water Active solar water collectorscollectors

Passive solar gains via Passive solar gains via glazed balconiesglazed balconies

Gains from greenhouse Gains from greenhouse –– midterm accumulation midterm accumulation into the gravel into the gravel accumulator below the accumulator below the building.building.

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2012/2013



Midterm solar energy Midterm solar energy accumulationaccumulation

GreenhouseGreenhouse airair warmingwarming upup

LoadingLoading of of thethe accumulatoraccumulator

UnloadingUnloading of of thethe accumulatoraccumulator

AdditionalAdditional heatheat sourcesource


Problem descriptionProblem description

BoundaryBoundary conditionsconditions

Geometry Geometry

ClimateClimate

FreshFresh airair volumevolume

RequiredRequired outputoutput of of thethe systemsystem

OptimisationOptimisation criterionscriterions

AnnualAnnual energy energy consumptionconsumption

OutputOutput of of thethe additionaladditional heatheat sourcesource

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2012/2013



Modelling of energy performance

Modelling Modelling tooltool selectionselection criterionscriterions

DynamicDynamic modellingmodelling

HeatHeat transfer transfer coefficientscoefficients

ESPESP--r, TRNSYSr, TRNSYS

Model Model in in ESPESP--rr

Zonal model describing building and Zonal model describing building and energy systemenergy system … … why why 2 model2 modelss??

EnergEnergyy systsysteemm

BuildingBuilding

+

Building model


Input:

10 zones, construction, shading elements, operational schedule

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2012/2013


Model of active solar system with mid-term heat

accumulation


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


SimulationSimulation Climate databaseClimate database: :

Test reference Test reference yearyear Time periodTime period 1 1 yearyear Time step of the output Time step of the output 1 1 hourhour Time step of the calculationTime step of the calculation 1 minut1 minutee

Building: What?

Energy demand for heating How? 1x simulation loop Output: Heating output

Energy system WhatWhat?? Annual energy consumptionAnnual energy consumption HowHow?? Virtual experimentsVirtual experiments ••Loading air variationLoading air variation ••Accumulation mass of the gravelAccumulation mass of the gravel OutputOutput?? Design of the elementsDesign of the elements

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2012/2013


Simulation results


Annual energy consumption

Heating energy consumptionimpact of accumulator

100%

56%

52%

53%

47%

47%

44%

0%

20%

40%

60%

80%

100%

120%

0 1 2 3 4 5 6

Virtual experiment Nr.

Virtual experiment

0 without accumulator

1-3 change of the loading air volume 100 to 2000 m3/h

4-6 change of gravel mass 50 to180 t

Energetický systémEnergetický systém

Temperature in the accumulator

100% = 11,4MWh =410EUR/year

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


building energy performance modelling and simulation 4

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