Illumination

Illumination Design

Illumination Design

ByEngr. Amando D.Lanuza, PEE

Presentor:

A newly passed Professional Electrical Engineer 12 years in government service as

City Electrical Engineer. A former OFW A former Barangay Electrician 3 time IIEE Chapter President of

IIEE Sorsogon

INTRODUCTION Light- is a form of radiant energy

from natural sources(e.g. sun and stars), and artificial sources (e.g. candle and electric lamps). It travels in a form of an electromagnetic wave, so it has wavelength and a known speed. Like other electromagnetic radiation, it can be reflected and refracted.

Lighting – is the application of light to illuminate objects, surfaces, scenes, pictures and people

Lighting on the other hand is the application of light to illuminate objects, surfaces, scenes, pictures and people.

Lighting concepts and

Units

Luminous flux (Ø)- All the radiated power emitted by a light source.

Luminous intensity - The visible radiant intensity in a particular direction. The unit of measurement is the candela ( cd )

Illuminance (E)- is a measure of the amount of light falling on a surface. Unit of measurement is lux (lx)

Luminous Efficacy (ŋ)

Luminous efficacy indicates the efficiency of the light source with which the electrical power consumed is converted into light. The unit of measurement is lumens per watt ( lm/W).

Lighting System Design

The design for indoor lighting system general illumination is considered to be more of an art than a science and it involves many variable factors.

Factors for indoor lighting includes: Size and shapes of the space. Types of finishes on ceilings, walls

and floors. The details of the construction The economic consideration of both

the initial and operating cost. The compatability of the lighting

system with the architectural design. The type of activities that will be

carried out in a particular area.

Objectives and design consideration: Determination of required level of illumination.

Quality required Quantity required Area atmosphere Area description and Use Selection of System Luminaire.

Determination of required level of illumination

See table for recommended illumination level for different types of occupancies by Illuminating Engineering Society of North America (IESNA)

Quality of Light

Pertains to the distribution of brightness in the lighting installation. Involves the comfort of seeing the environment . Factors to consider are , brightness, contrast or luminance ratio, glare, diffuseness and color.

Quantity required

The quantity of light involves adequate level of illumination for the average person under normal condition.

Area Atmosphere Analyze the environment in which the

lighting system will operate. For example, are dirt, water vapor, explosive gasses or corrosive vapor present?

Area description and use: A complete description is required

for each area to be lighted, this includes physical characteristics such as room dimensions, room reflectance and work location.

Selection of system luminaire Selection of the type of luminare for

a given application depends upon the requirements and conditions stated above.

Determining Average Illuminance

The average illuminance level can be determined when a given number of luminaires used in a space is known. Likewise, the number of luminaires can be determined given the average illuminance level.

Within the room, the illuminance is determined based on the horizontal plane, which is considered as the work plane. The work plane is measured at the height of the visual task. In the office this would generally be at a height of 0.75 meter above the floor, the average height of an office table. In the corridors , the work plane is usually considered to be the floor.

The general equation for the illuminance in a work place is:

Ø(TOTAL) x CU x LLF E WP = ------------------------------ A WP

Where: E wp - Work plane

illuminance, lx Ø(TOTAL) – total system lamp

lumen output, (lm). CU – coefficient of utilization. LLF- light loss factor A wp – area of work plane , m²

Work plane illuminance,Ewp : The average maintained luminous

flux that hits the work plane per unit area. The unit of measurement is lx.

Total system lamp lumen output , Ø total:

refers to the quantity of light produced by all lamps that are lighting a space.

Coefficient of utilization ,CU: The ratio of the lumens that

reaches the work plane to the total lumens given off by the lighting system

All the lumens from the lamps in a lighting system generally do not reach the work plane. Some of them are absorbed by the floors, walls and ceilings before reaching the work plane. The fraction of luminous flux emitted by the lamps that reaches the work plane in a space is the coefficient of utilization. If 50% of the light given off by the lamp reaches the work plane, then CU is 0.50, in some cases the CU can be grater than 1.0 for rooms with higher reflectances and lamps with higher efficacy.

Light Loss Factor (LLF): is the ratio of

illuminance when it reaches the lower level( just before corrective action takes place) to the initial level. The total light loss is the product of all the individual factors that contribute to the loss of light. It is also known as the maintenance factor.

Light Loss Factor (LLF) equation is:

LLF = LLD x LDD x RSDD where : LLD - Lamp Lumen Depreciation

Factor The depreciation of lumen

output of lamp through life. LDD- Lamp Dirt Depreciation Factor With the passage of time, dirt accumulates on lamps

resulting to loss of light.

RSDD- Room Surface Dirt Depreciation Factor:

With the passage of time, the accumulation of dirt on the surface of the room further reduces the amount of light that reaches the work plane

Indoor Lighting Calculation The Lumen Method: This method is used to

design general overall lighting of the room. This method calculates the illuminance that represents the average of the values at all points over the entire work plane of the room.

The average illuminace of the work plane (E)

TILL x CU x LLF E = ---------------------- Area Where : TILL = total initial lamp lumens

Sample simplified calculation Find out if two -36WT8

fluorescent lamp is enough to illuminate a typical dining room with dimension 3m x 4m , assuming the CU is 0.65 and LLF is 0.95 .

Solution: Looking at the manufacturer’s data of

36WT8 fluorescent lamp, luminous flux is 3350 lm.

using the formula: TILL x CU x LLF 2 x 3350 xo.65 x

0.95 E = -------------- = --------------- --------= Area 3 m x

4m

= 334.78 lux

Looking at the Table: Recommended level of illumination by IESNA for Dining rooms is 540 lux.

Therefore: 2 -36WT8 FL is not

enough Use 3 - sets

Uniformity of Light: The average illumination at

work plane is directly related to the maximum spacing of the luminaire to the mounting height ratio represented by:

S ratio = ----- MH Where : S = spacing of light fixtures MH = mounting height

Assume that the mounting height of lighting fixture is 3 meters from the floor. What is the maximum spacing of fluorescent.

Recommende spacing and mounting height ratio:

Type of light s/mh Ratio

Direct concentrating 0.40 Direct spread 1.20 Diffused

1.30 Semi –direct/ indirect 1.50

Using the formula: s

ratio = ------ = mh

s = 3 x 0.40 = 1.2m

An office room having a dimension of 8 m x 20 m

Is to be lighted with a maintained illumination. How many 3- lamp 36wFL parabolic troffer are required .

From the formula:

illumination x area N =

---------------------------------------- lamp per fixture x lumen x

CUx LLF

Looking at the manufacturer’s data of 36watts fluorescent lamp , luminous flux = 335000 lumens.

Recommended illumination level for offices is 1600m lux

Assume CU = 0.65 LLF= 0.85

Substituting values:

1600 (8 x 20) N = --------------------------- 3 x 3350 x 1.0 x 0.95

N = 26.8 use : 24 sets or 28 to

make it symmetrical

The design of lighting system requires knowledge of basic lighting terms combined simple mathematical or graphical presentation and technics.

The methods and calculation in the lighting system design presented in this presentation are based on the recommended procedures of Illuminating Engineering Society of North America (IESNA) .The formula presented are only meant to be a general overview on illumination design calculation.