Lighting with Artificial Light

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Lighting with Artificial Light

The basics of lighting

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What is light?

Coloured objects only appear coloured if their colours are present in the spectrum of the light source.

The visible part of electromagnetic radiation, which is made up of oscillating quanta of energy

Speed of light: 2.98 x 10

⁸

m/s, i.e. around 300,000 km/s

Light spectrum: 380 nanometres (violet) to 780 nanometres (red)

White sunlight is the sum of all the colours of the light spectrum

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The eye – ”our camera”

There are around 130 million visual cells in the

human eye, divided into two types: rods and cones

Rods are sensitive to brightness, Cones are for colour vision

Adaptation: adjustment of the eye to higher or lower levels of illuminance

Dark adaptation takes longer than light adaptation

80 percent of all the information we receive is provided by our eyes.

Fotolia.com: Bonnie C. Marquette

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Hier könnte eine Bildunterschrift stehen.

From fire to LED

300,000 years ago: man starts using fire as a source of heat and light

Around 260 B.C.: construction of the Lighthouse of Alexandria

1783: gas is extracted from coal for use in street lights

1879: invention of the incandescent lamp

1880s: appearance of early fluorescent lamps

1995: presentation of the first LED delivering white light

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Lighting terminology and variables

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Variable Explanation Unit Abbreviation Symbol

Luminous flux rate of light emitted by a lamp

lumen lm

Luminous intensity luminous flux in one direction

candela cd I

Luminous efficacy luminous flux per watt

lumen/watt lm/W

Luminance perceived brightness of a surface

candela/

square metre

cd/m

²

L

Illuminance luminous flux on a given surface

lux lx E Reflectance luminous flux

reflected by a surface

percent p p

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Lighting quality features are interrelated.

Factors of good lighting

Visual performance, determined by

lighting level

glare limitation

Visual comfort, determined by

colour rendering

brightness distribution

Visual ambience, determined by

direction of light/modelling

light colour

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Quality features for visual performance

Lighting level

illuminance

reflectance (e.g. walls)

The lower the reflectance, the higher the illuminance needs to be

Glare limitation

direct glare

reflected glare

Glare causes discomfort and can interfere with visual performance

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Illuminance – standards

Illuminance is stipulated in standards, e.g.

DIN EN 12464-1 for indoor workplaces

DIN EN 13201-2 for street lighting

Examples of illuminance (measured in lux, lx)

office 500 lx car park 15 lx

precision engineering 1,000 lx kitchen 500 lx

operation cavity 100,000 lx stairs 150 lx

By comparison: daylight illuminance

cloudless summer‘s day 100,000 lx

overcast winter‘s day 3,000 lx

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Illuminance – maintained illuminance

Soiling and ageing of luminaires, lamps and room surfaces cause the

illuminance of an installation to decrease in the course of its operating life.

So new installations need to be designed for a higher illuminance (= value on installation).

Maintained illuminance values (= average on the assessment plane) are set out in standards.

Illuminance must not fall below the maintained illuminance value.

Maintenance factors are defined by designers and operators to calculate illuminance on installation. They take account of the type of luminaires and lamps used as well as the risk of soiling and maintenance intervals.

Formula for planning:

maintained illuminance = maintenance factor x illuminance on installation

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Glare limitation – direct glare

Direct glare is caused by

excessively high luminance

general-diffuse lamps

incorrectly positioned luminaires

How to avoid glare:

shield lamps

position luminaires correctly

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Glare limitation – reflected glare

Reflected glare is caused

by excessively luminous lamps, luminaires or windows

at reflective or shiny surfaces

(e.g. wet roads, computer screens) Example: luminance limit

Positive display VDU,

mean luminance 1,000 cd/m

²

How to reduce reflected glare:

select correct luminaires and lamps

ensure favourable arrangement of light sources

reduce luminance of surfaces that are reflected

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Quality features for visual comfort

Harmonious distribution of brightness

supports vision by creating a balanced pattern of luminance

lends structure to a room

Good colour rendering

facilitates accurate identification of colours

influences the climate and atmosphere of a room

The colour rendering index R

_a

indicates how well lamps render natural colours (optimal value R

_a

= 100).

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Quality features for visual ambience

Light colours

warm white (< 3,300 kelvin)

neutral white (3,300 – 5,300 K)

daylight white (> 5,300 K)

Direction of light

direct (directional) light

diffuse (non-directional) light

Modelling

gives objects depth

emphasises surface structures

Tip for agreeable contrasts: balanced mix of diffuse and directional light

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Light colour and colour rendering characteristics

The colour rendering quality of a lamp is determined by the spectral composition of its lamps.

Lamps of the same light colour can emit light with a different spectral composition.

So it is not possible to draw conclusions about colour rendering from light colour.

Colour coding of lamps

Every lamp has a colour code. It consists of three digits and indicates the lamp‘s colour rendering index and light colour

1st digit: colour rendering performance, e.g. 9 for R

_a

range 90-100

2nd + 3rd digit: colour temperature, e.g. 27 for 2,700 K

Example: fluorescent lamp with colour code 830

This fluorescent lamp has a good R

_a

index between 80 and 90 and a warm

white light colour of 3,000 K.

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There are basically three types of light sources:

Thermal radiators: incandescent and halogen lamps

Discharge lamps: fluorescent, high- and low-pressure lamps

Solid-state light emitters: LEDs und OLEDs (organic light-emitting diodes) All three types are available in a wide variety of models and variants.

Overview of lamps/light sources

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Light sources: technical variables

From watt to kelvin

Technical ratings facilitate lamp selection:

power rating unit: watt (W)

luminous flux unit: lumen (lm)

efficiency/luminous efficacy unit: lumen per watt (lm/W)

colour rendering unit: colour rendering index (R

_a

)

colour temperature unit: kelvin (K)

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Light colour and colour temperature warm white < 3,300 K

neutral white 3,300 – 5,300 K

daylight white > 5,300 K

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Luminaires: arrangement and characteristics

1. Requirements

Application, e.g. interior or exterior luminaire

Type and number of lamps

Structural type, e.g. open/closed luminaire

Type of mounting, e.g. recessed luminaire

2. Characteristics

lighting characteristics

electrical characteristics

mechanical characteristics

exterior design

First plan, then select.

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Luminaires: technical variables

Lighting characteristics, e.g.

luminous flux distribution

luminous intensity distribution

luminance distribution

light output ratio

Electrical characteristics, e.g.

electrical reliability

ballasts

radio interference suppression

class of protection

degree of protection (Ingress Protection)

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Luminaires: modern control

Operating devices

electronic ballasts

transformers/capacitors

startes and igniters

Lighting management

Electronic lighting control depending on:

daylight incidence

precence

room use

Simple operation, e.g. with

A presence detector alone cuts energy consumption by up to

10%.The energy saving with daylight-dependent regulation

can be as high as 35%.

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Basics of planning

Well-planned lighting

takes account of user requirements

complies with relevant standards

is energy-efficient

Information required for planning:

room plans/ground plan

colours/reflectances (walls, ceilings)

function of rooms/visual tasks

furnishings/arrangement of machines

operating conditions (dust, moisture)

for roads: installation geometry and reflective properties of the road surface

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Lighting costs

Lighting costs comprise:

initial outlay (acquisition, installation)

operating costs

Operating costs comprise:

maintenance costs (lamp replacement, labour costs)

electricity costs

Electricity costs account for as much as 70% of the total costs of a lighting installation.

The use of efficient lighting technology saves energy and money.

Example: Electricity costs

Energy-saving lamp (11 Watt)

0.011 kW 8,000 h 0.18 euro =

15.84 euro/year

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Enery-efficient lighting

Factors for energy-saving lighting are:

efficient light sources, e.g. LEDs

luminaires with a high light output ration and optimal luminous intensity distribution

lighting management geared to requirement

daylight utilisation

Optimal lighting = maximum quality + minimum consumption Savings potential of of interior lighting: up to 75% less electricity

Enery consumed for lighting is one of the factors used to assess the energy

efficiency of buildings (standard: DIN V 18599).

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Lighting and the environment

EU sets standards

In the European Union (EU), requirements have been defined at the highest level for

climate protection

nature conservation

health and safety

sustainability

Relevant directives include:

Ecodesign ErP Directive (Energy related Products)

EPBD Directive (Energy Performance of Buildings Directive)

The EU aims to reduce its energy consumption by 20% ^{by 2020.}

Efficient lighting will help achieve this target.

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Further information

Further information on the subject is provided

in the booklet licht.wissen 01

„Lighting with Artificial Light“ (62 pages)

This and other booklets in the licht-wissen series are available as free pdf downloads at

www.licht.de/en

More information on lighting:

Deutsche Lichttechnische Gesellschaft (LiTG), www.litg.de

Standards on the subject of light and lighting:

Beuth-Verlag, www.beuth.de

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Publisher

licht.de

Fördergemeinschaft Gutes Licht Lyoner Straße 9

60528 Frankfurt am Main [email protected]

www.licht.de

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