a computer aided design of indoor lighting to achieve … a comparative study between them on the...

Journal of Innovation and Research Vol. 1, No.1, May 2018

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Abstract—This paper presents a computer-aided design

of indoor lighting for a computer simulation laboratory

using CFL (FBH 150 ‘T’/218 PL-C18W, 2 PIN) and LED

(13371 BZLOS 18W WH) light sources separately and to

conduct a comparative study between them on the basis of

visibility and energy efficiency. For this purpose, open

source lighting design software ‘Dialux (version 4.13)’ is

used. The design goal is to achieve proper visibility in terms

of average illuminance (lux) level & reduced energy

consumption in terms of Lighting Power Density (LPD) in

compliance with National Lighting Code (NLC-2010) and

Energy Conservation Building Code (ECBC-2016)

guidelines respectively. Results show that, use of LED can

fulfill the set objectives satisfactorily. The cost benefit

analysis of the two design schemes through pay-back period

computation is also presented. Such kind of study can be

useful for better demand side management and can be

extended further through real-life implementation.

Index Terms— Dialux, energy efficiency, lighting design,

lighting power density

I. INTRODUCTION

A. Energy Efficient Lighting

India is a population dense country where around 17% of

total produced energy is consumed yearly for electric lighting.

Hence, there is huge scope to save electricity by proper lighting

design using energy efficient sources. But it should not

compromise the quality and visibility of the lighting

environment. Enormous energy savings are possible using

energy efficient equipment, effective control and careful

design. Usage of lesser number of sources reduces heat gain.

Thus, improving thermal comforts and reducing Heating

Ventilation Air Conditioning (HVAC) load. Electric lighting

design also strongly influences visual performance and visual

comfort by aiming to maintain adequate and appropriate

illumination while controlling reflection and glare [1].

In order to achieve the above requirements the energy

efficient light sources like Light Emitting Diode (LED) and

Compact Fluorescent Lamps (CFL) are preferred now-a-days

over incandescent bulbs. CFLs are miniature version of tubular

fluorescent lamps and works on the principle of gas discharge.

LEDs are small, very efficient solid state light producing

devices. A significant feature of LED is that the light is

directional as opposed to incandescent bulbs which spread the

light more spherically. Due to this feature, use of lenses and

diffusers is mandatory over the LED chips.

LEDs are more efficient than incandescent and fluorescent

light sources. It consumes less electricity and lasts up to more

than 6 times longer than CFLs. The durability and longevity of

LED and CFL bulbs are approximately 50000 hours and 10000

hours respectively. From environmental aspect also, LEDs are

better than the CFLs. A CFL contains small amount of mercury

which is a toxic metal. This metal may be released to the

environment if the bulb is broken or disposed. On the other

hand, LEDs are mercury free and recyclable, hence friendly to

the environment. Although, usage of LEDs is advantageous, the

initial installation cost is higher. However, the invested money

is repaid back to the customer in terms of savings in electricity

bill [2].

B. Computer Aided Design

Lighting design is a very relevant field today which is

primarily directed to provide ‘proper light in proper place in

proper time’ which in turn helps to reduce electricity

consumption in the consumer end. Lighting design can be

carried out either manually or by using dedicated software. In

manual method, ‘Lumen formula’ is usually applied and several

factors, i.e. maintenance factor, utilization factor etc. are to be

taken into account. The process involves manual labour and

time, which can be avoided if the latter one is opted. In our

work, open source lighting design software ‘DIALUX

(Version: 4.13)’ is chosen as the design tool [3]. As efficient

sources, a commercial CFL and a commercial LED luminaires

are selected. As the test room, a newly built Computer

Simulation Laboratory of Calcutta Institute of Engineering And

A computer aided design of indoor lighting to

achieve improved visibility and reduced power

consumption

N. Thander, P. K. Singh, B. Gupta Bakshi

Electrical Engineering Department, Calcutta Institute of Engineering & Management,

Kolkata, India


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Management (C.I.E.M), Kolkata is selected. Thereafter, two

main objectives for the lighting design project are set, viz.

i. Achieving proper average illumination level (lux)

on the working plane as per National Lighting Code

(NLC-2010) standard [4].

ii. Achieving required lighting power density (LPD)

value as per Energy Conservation Building Code

(ECBC-2016) standard [5].This parameter is measured

as the total power consumption for lighting purpose

(Watts) per unit area of the working plane (m2).

In the following sections, the detailed work plan,

methodology and results are presented.

II. ROOM SELECTION AND MEASUREMENT

The main purpose of designing is to achieve the proper

Illumination Level and LPD value as per the NLC-2010 and

ECBC-2016 guidelines respectively. For the test room, a

computer simulation laboratory of our institute (C.I.E.M,

Kolkata) is selected. The dimension of the selected room is

measured as 6.35m x 6.40m x 2.54m. The room has rectangular

plan with false ceiling. Colours of the floor, four concrete walls

and the false ceiling are grey, sky blue and white respectively.

The room is to be used as a new computer simulation laboratory

of Electrical Engineering department. Students will also

conduct their project-related works there. For this purpose, the

room contains several accessories like four long desktop tables,

a big workplace table, a double-sided shelve and 20 desktop

computers and swivel chairs. There are two entry points for the

selected room: two inward left hinged and right hinged doors

on the two walls. The room has no window and is to be

equipped with air-conditioner machine. The details and areal

size of the accessories are tabulated in TABLE 1. For

illumination design, working plane is selected as the surface of

the tables i.e., 0.72m from the ground. As mentioned earlier, the

height of the room is 2.54m. Therefore, considering surface

mounted luminaires, the height of the light sources (ceiling)

from the working plane can be estimated as: (2.54m - 0.72m) =

1.86m.

TABLE 1

ROOM ACCESSORIES

Accessories Length

(m)

Width

(m)

Height

(m)

Surface

Area (m²)

Desktop Table-1 2.85 0.6 0.72 1.71

Desktop Table-2 5.8 0.58 0.72 3.364

Desktop Table-3 5.76 0.6 0.72 3.456

Desktop Table-4 3.7 0.6 0.72 2.22

Work plane

Table 2.8 2.8 0.72 7.84

Double-sided

shelves 2.3 0.4 2.5 -

Swivel chair 0.5 0.5 1 -

Door-1 (left

hinged - 0.935 2.15 -

Door-2 (right

hinged) - 1.13 2.15 -

Size of PC 0.5 0.5 0.5 -

III. LUMINAIRE SELECTION

Artificial light source are measured not only by their visual

comfort characteristics (brightness, colour temperature, colour

rendering index and light distribution) but also by their

efficacy-that is, their effectiveness at converting electricity into

light. Hence, the choice of light source is very important, both

for visual comfort and for energy efficiency [2].

In our work, the height of the room is 2.54m with false

ceiling. Since, the height of the room is comparatively less;

surface mounted light sources are selected for Glare Reduction

and Better Space Utilization. Here, down lighter LEDs of 18W

and CFL luminaire (2xPL-C 18W) are opted as the light

sources. Using these two modern light sources, the computer

aided design is carried out. The software (Dialux) recognizes

the sources by a special extension file (.ies files). These files for

the mentioned luminaires are collected with the assistance of

Illumination Engineering Section of Jadavpur University.

Details of the luminaires can be obtained by opening the .ies

files by software ‘Photometrics Pro’ (trial version).The details

of the luminaires are tabulated in TABLE 2. To illustrate the

light distribution pattern of the two sources, their intensity

distributions are shown in Fig. 1.

(A) (B)

Fig. 1. Intensity distribution diagram of the luminaires: (A) CFL and

(B) LED

TABLE 2

LUMINAIRE DETAILS

PARAMETER 13371 BZLOS 18W

WH (LED)

FBH 150 ‘T’/218

PL-C18W,2 PIN

(CFL)

Lamp type LED CFL ( × 2)

Ballast/ driver Electronic Electronic

Luminaire

lumen 1357.1 lm 2400 lm


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Input power to

the

luminaire

18W 40W

Max. Intensity 514.3 Cd. at H=00, V=00 504.0 Cd. at H=00,

V=00

Manufacture Bajaj Philips

IV. STEPS OF THE DESIGN

To design the lighting for the room using DIALUX,

following algorithm is followed-

STEP-1: The accurate measurements of the room are taken.

STEP-2: Using lighting design software Dialux (version

4.13) [3], the room of given dimension is created.

STEP-3: Now, the accessories of approximate size and

dimensions (as per TABLE 1) are placed at their respective

positions. The accessories are such as Computer Tables and

workplace, Desktop (PC), Chairs, Book-Shelve and Doors.

STEP-4: Maintenance Factor (MF) is referred as Light Loss

Factor (LLF) in Dialux. It is the measure of depreciation of light

output over the time. LLF is affected by many factors like

Temperature, Dirt and Dust over time [6]. Here, the LLF is

taken 0.8.

STEP-5: The co-efficient of utilization (COU) is dependent

on reflectance of the room surfaces and the room geometry. The

COU is a factor used to determine the efficiency of a lighting

fixture in delivering light for a specific application. It is

determined as the ratio of light output from the luminaire that

reaches the work plane to the light output of the lamp alone [6].

Here, the COU is automatically calculated by the software

(DIALUX) from room geometry and the reflectance. The

reflectance values are set as0.5, 0.2 and 0.8 for walls, floor and

the ceiling respectively.

STEP-6: Thereafter, the .ies files of the two luminaires are

selected separately from the database.

STEP-7: The field arrangement is opted for the uniform

distribution of light sources. In this arrangement, the luminaires

are uniformly distributed in the ceiling surface. Dialux carries

out the estimation on the basis of lumen formula and shows the

suggested arrangement (row/column) once the target Lux Level

is set. For our design, the selected room is to be used for

educational purpose. Referring to the National Lighting Code

(NLC-2010), the recommended average light level is found to

be 300 lux which is used as the target value [4].

STEP-8: Finally, the simulation is carried out and result is

generated along with the single sheet output.

V. RESULTS AND DISCUSSIONS

A. Visibility and Energy Consumption

Once the simulation is complete, the illuminated 3-D view of

the room is generated by DIALUX as depicted in Fig. 2 and 3.

Apart from this a single sheet output of the design is obtained

showing the light distribution pattern, average illuminance (lux)

level and the LPD value. The light distribution pattern (iso-lux

diagram) with the two sources is shown in Fig. 4.

As per the National Lighting Code (NLC-2010), the target

average illuminance (lux) level value for

classroom/conference/Lecture training purpose must be greater

than 300 lux and less than 500lux [4]. In our work, as the test

room, a Computer Simulation Laboratory is selected. Hence,

the target light level value for the specific application is set as

300 lux. The light level values achieved using LEDs and CFLs

separately are 422 lux and 302 lux respectively. Therefore, as

per the above result, LEDs are more advantageous over CFLs.

As per Energy Conservation Building Code (ECBC-2016)

standard, the target LPD value for

classroom/conference/Lecture training purpose must be less

than or equal to 15.1 W/m2 [5]. In our work, the LPD value

achieved with CFLs is 19.69W/m2 whereas using LED; the LPD

is reduced to 8.86 W/m2. Hence, use of LED can reduce the

electrical energy consumption for lighting purpose than that

using a CFL. Comparative design output of the two schemes

with respect to the target value is illustrated using bar-cart as

shown in Fig. 5.

B. Payback period analysis

The payback period is the length of the time required to

recover the cost of an investment. This analysis deals with the

investment on CFLs and LEDs separately and the period of time

required recouping the fund expended in the investment. The

calculations are shown in TABLE 3.

TABLE 3

PAYBACK PERIOD ANALYSIS

PARTICULAR(S)

LUMINAIRES

13371 BZLOS

18W

WH (LED)

FBH 150 ‘T’/218

PL-C18W,2 PIN

(CFL)

Power per lamp 18W 18W

Number of lamps 20 40

Operation Schedule

(20 days per month) 3 hours/day 3 hours/day

Total Power Consumption in

Watt (per hour) 20×18 = 360 W 18×40 = 720 W


kilowatt (kW) (per hour)

360/1000 = 0.36

kW

720/1000 = 0.72

kW


kWh (per day)

0.36kW × 3h =

1.08 kWh

0.72kW × 3h =

2.16 kWh


kWh

(per month considering 20

working days)

1.08 kWh × 20 =

21.6 kWh

2.16 kWh × 20 =

43.2 kWh

Per unit Cost of Power

Consumption (approx) Rs.8 Rs.8

The Cost of Total Power

Consumption per month

21.6 kWh × Rs.8 =

Rs.172.8

43.2kWh × Rs.8 =

Rs.345.6


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Maximum Retail Price

(per lamp) Rs.300 Rs.120

MRP for 20 lamps Rs.20 × 300 =

Rs.6000

Rs.40 × 120 =

Rs.4800

From above, the difference in the cost of total power

consumption (per month) for the two light sources is

X= (Rs.345.6 - Rs.172.8) = Rs.172.8

And the difference in total investment is

Y= (Rs.6000 - Rs.4800) = Rs.1200.

Now, the payback period (in months) to recover the cost of

the investment is:

Ypayback perod (months) =

X Hence in our case, installation of LED will have a payback

period of = 1200/172.8=6.944 months = 6 month and 29 days=

7 months (approx). Hence, the payback period to recoup the

cost of investment is 7 months (approx.).

VI. CONCLUSION

In this paper, a computer aided lighting design using LED

and CFL luminaires is presented. After the simulation, a

comparative analysis between the design environments

involving the two mentioned sources is performed. It is

observed that targeted working plane light level (300 lux) has

been well achieved for LED as well as CFL. From energy

efficiency point of view, LED gave better result, as the obtained

LPD (8.86 W/m2) is well below the recommended value (15.1

W/m2). On the other hand, LPD value corresponding to CFL

(19.69 W/m2) is greater than the maximum limit. Hence, it can

be concluded that, use of LED can improve the visibility and

energy efficiency of the system. One drawback of the LED is

higher initial cost. Through pay-back-period analysis, it is

established that, the invested higher initial cost will be

recovered to the consumer through the saving in electricity bill

after a very short period of normal usage (approximately 7

months).This kind of work can be further extended for real life

implementation.

ACKNOWLEDGMENT

The authors are thankful to the Electrical Engineering

Department, Calcutta Institute of Engineering & Management

for cooperation and encouragements. No specific financial

support/sponsorship is received for this work.

Fig. 2:3-D view of the room illuminated by CFL


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Fig. 3:3-D view of the room illuminated by LED

(A) (B)

Fig. 4. Light distribution pattern (iso-lux diagram) of the room illuminated by: (A) CFL, (B) LED


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(A) (B)

Fig. 5. Comparative visibility and LPD of the room illuminated by: (A) CFL, (B) LED

REFERENCES

[1] Robert S. Simpson, Lighting Control

Technology and Applications, Focal Press,

Published 2003,ISBN 0 240 51566 8.

[2] Lighting Handbook Reference and Application

9th edition, Illuminating Engineering Society of

North America (IESNA), ISBN 0-87995-150-8.

[3] Lighting Design Software DIALUX (version

4.13),https://www.dial.de /en /software /dialux /.

[4] National Lighting Code-2010 (SP 72: 2010),

Bureau of Indian Standards, Ministry of

Consumer Affairs, Food and Public Distribution,

Government of India, ICS 01.120:91.160.01,

ETD 24: Illumination Engineering and

Luminaries.

[5] Energy Conservation Building Code-2016,

Bureau of Energy Efficiency, Ministry of Power,

Government of India.

[6] R.H.Simons and A.R.Bean, Lighting

Engineering Applied Calculations, Architectural

Press, Published 2001, ISBN 0 7506 5051 6.

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