Natural Light in DesignNatural Light in DesignUsing simulation tools to explore realistic daylight-responsive solutionsUsing simulation tools to explore realistic daylight-responsive solutions

Christoph Reinhart, Ph.D.Christoph Reinhart, Ph.D.

DaysimDaysim

Daylight Factor Visual Comfort

Daylight Autonomy Avoidance of Direct Sunlight

Overview – Daysim

Required Work FlowSketchUp/ AutoCAD/ Ecotect/ …

Daysim Analysis www.daysim.com

Daysim Simulation Report

falsecolor maps

Daysim Statistics

www.daysim.com

Example I – Single office

⟨ Located in Ottawa Canada

⟨ Taken from Daysim tutorial

Your Task: Use Daysim to:• Calculate daylight autonomy and daylight factor in the offices• Estimate the lighting energy savings from an occupancy sensor.

office building three lighting zones

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4 6 8 10 12 14 16 18 20 22time of day [h]

glob

al ir

raid

atio

n [W

/m2 ]

1hour1 min

Development of a stochastic Model to calculate 1-min irradiances from 1 hour means

Solar Energy Walkenhorst, Reinhart 2002

Short-Time-Step Dynamics of Daylight

Step 1: Normalization

Short-Time-Step Dynamics of Daylight

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4 6 8 10 12 14 16 18 20 22time of day [h]

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Interval 1 Interval 2

2PM to 3PMShort-Time-Step Dynamics of Daylight

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glob

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Short-Time-Step Dynamics of Daylight

Climate data – US DOEClimate data – US DOE

http://www.eere.energy.gov/buildings/energyplus/cfm/weather_data.cfm

Dynamic Daylight Simulations (DDS)As opposed to static DL simulations that only consider one sky condition at a time, dynamic daylight simulationsgenerate annual time series of interior illuminances and/orluminances.

How?

Daylight Coefficients

(1) Division of the Celestial Hemisphere

Eα(x)illuminance atx due to Sα

Sα

x

(2)Calculate Daylight Coefficients

climate Data: i

Energy & Buildings

Reinhart & Herkel 2000

Daylight coefficients: “fastest method & most accurate

dynamic method”

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0 500 1000 1500 2000 2500 3000 3500hours per year

Illum

inan

ce [l

ux]

reference case (12 days)

ADELINE (25 h)

classified weather data (20 h)

ESP-r (3 h)

DaySim (1.5 h)

Comparison of Dynamic Daylight Simulation Methods

Validation II

Daylight Coefficients: “same accuracy as standard Radiance”

Light. Res. & Technology Mardaljevic, 1997

Figure by MIT OCW.

0.0

0.5

P_cell 1N_Skies 725

MBE% -3.2RMSE% 19.8

Nor

m. F

req.

P_cell 2N_Skies 736

MBE% 1.0RMSE% 17.9

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0.5

P_cell 3N_Skies 741

MBE% 12.4RMSE% 19.9

Nor

m. F

req.

P_cell 4N_Skies 744

MBE% 1.7RMSE% 14.2

0.0-100 -50 0

Relative Error (%) Relative Error (%)50 100

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P_cell 5N_Skies 748

MBE% 5.7RMSE% 12.3

Nor

m. F

req.

-100 -50 0 50 100

P_cell 6N_Skies 751

MBE% -1.7RMSE% 11.3

C L E A R G L A Z I N G

Validation III - Venetian Blinds

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0 200 400 600 800 1000illuminance threshold [lux]

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light

Aut

onom

y [%

] measuredsimulated

RADIANCE-based simulation approach

Energy & Buildings Reinhart, Walkenhorst 2001

Validation IV - Translucent Panel

Energy & Buildings Reinhart, Andersen 2005 (in review)

Need for a quality controlled material database.

Summary

Radiance combined with daylight coefficients and Perez sky model can efficiently and reliable calculate DDS. (validated approach – several independent studies –resulting accuracy ~20% rel. error – comparable to staticsimulations)

Radiance Simulation Parameters I

ambient bounces

ambient division

ambient sampling

ambient accuracy

ambient resolution

direct threshold

direct sampling

5 1000 20 0.1 300 0 0

simulation resolution =max scene dimensions x ambient accuracy

ambient resolution

Example:100m x 0.1

300 ~ 3cm (window mullion)

Radiance Simulation Parameters II

Higher raytraing parameters for blinds raytracing detail

ambient bounces

ambient division

ambient sampling

ambient accuracy

ambient resolution

direct threshold

direct sampling

7 1500 100 0.1 300 0 0

10m x 0.1 /300~0.3cm(blind slat)resolutionambient

accuracyambientxensionsceneimum dimmaxaa and ar:

Manual blind control model

work plane sensors

window with blinds) )

) ) )

) ) )

)

) ) )

⟨ Daysim: active (energy conscious) or passive user

⟨ Associate work plan sensor with window

⟨ Note: this step requires to couple individual sensors together.

⟨ Benefit: Direct comparison between daylighting concepts with andwithout movable and/or fixed shading devices

Example I – Single officeDaylight factor simulation

⟨ same results for North and South offices⟨ no daylight on the central aisle

Example I – Single office

⟨ ample amount of daylight in both offices⟨ up to 30% DA on aisle => on/off switch with timer

Daylight Autonomy simulation

Occupacy Sensors

• IR: detect changing heat fields (work best when its cool inside)

• UV: detects changing movements (cannot differentiate between a fax machine and a person)

• wall, celing mounted, integrated in luminaire

• stand alone, connected to BAS

wall mounted

ceiling mounted

Lighting Controls I

Photocell-controlled Dimming with

Occupancy Sensor

Occupancy sensor.

Photocell.

Lighting Controls II

Example I – Single office

⟨ absolute comparison of different control strategies ⟨ reference case is manual on/off switch with venetian blinds

Electric Lighting Use in South facing Office

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manual on/off switch switch-off occupancysensor

on/off occupancysensor

dimming system dimming system withswitch-off occupancy

sensor

dimming system withon/off occupancy

sensor

annu

al e

lect

ric li

ghtin

g us

e [k

Wh/

ft2 yr

]

reference case

Example II - Museum LightingCIE TC3-22 ‘Museum lighting and protection against radiation damage’

category material classification

example of materials

lighting illuminance

limiting annual exposure

I insensitive metal, stone, glass, ceramic

no limit no limit

II low sensitivity canvases, frescos, wood, leather

200 lux 600 000 lux h /yr

III medium sensitivity

watercolor, pastel, various paper

50 lux 150 000 lux h/yr

IV high sensitivity

silk, newspaper, sensitive pigments

50 lux 15 000 lux h/yr

Example II: Seattle Art Museum -Arup Lighting using Daysim3D model of site and building

ARUP Lighting

Source: Matt Franks ‘Daylighting in Museum'shttp://irc.nrc-cnrc.gc.ca/ie/light/RadianceWorkshop2005/PDF/Franks_ArupCaseStudies.pdf

Example II - Seattle Art Museum -Arup Lighting using DaysimSidelit Gallery ARUP Lighting

Example II - Seattle Art Museum -Arup Lighting using DaysimMuseum Open Hours - 1,500,000+ lux-hours ARUP Lighting

Example II - Seattle Art Museum -Arup Lighting using DaysimAutomatic Shading + Switching - 555,000 lh ARUP Lighting

Example III - Classroom

No skylights. Skylights.