Energy plays a major role in the long-run growth of the economy and is crucial in productivity of commercial sector. The core reason of this vitality is its cost-effectiveness, which is the reason why advanced economies focus on the idea of utilization of electrical energy in most efficient ways. Alongside Economic prosperity, Human development is dependent fundamentally on energy too. In a nut shell, Energy is the hub of progress. In Pakistan, massive electricity depletion has occurred due to demand supply gap leading to blackouts in residential areas and most importantly caused rigorous damage to the commercial sector. Prime solution to this problem is the application of the passive building design that conserves energy usage in buildings by smart technologies.

Artificial lighting consume one-fifth of global electrical energy [1] while 50-70% of general usage lighting is provided by conventional incandescent lamps (ICL) [2] that are 90-95% ineffectual. Energy preserving while upholding the required lighting level is a perplexing undertaking in designing lighting systems for buildings. Lighting is an immensely colossal growing source of energy demand and Green House Gas (GHG) emission. For artificial lighting most prevalent sources are the Incandescent Lamps (IL) and compact fluorescent lamps (CFL). IL is inept, converts 90% of electrical energy into heat [3] and short bulb life. CFLs are more efficient than incandescent bulbs in terms of energy saving [4] and durability but they contain hazardous material mercury [5], slow replications and recycling problems. This leads to a distinctive lighting technology called Light Emitting Diodes (LED). LEDs lights have the potential to overcome many such issues as they are good on low power consumption, diligent switching [6] minimal cost incurred on maintenance, better efficiency (lumen/ Watt), long-lifetime, high tolerance to moisture, no radiations, no recycling issues like CFLs and no inapt lamp failure as in the case of incandescent and eco cordial. Life Cycle Assessment has been used to understand the environmental impacts associated with each phase of the bulb’s life. Where life cycle analyses have been conducted in the past, the long lifetimes of LED and CFL lamps are show to offset the manufacturing and disposal impacts as fewer lamps are required [7-9]. So, conventional light bulbs are replaced with LED for energy preserving, financial perspectives [10] better performance, high moderation to moisture, cool operation elongated life and are highly efficient.

The luminous level for work place is defined by Lux, lumen /watts and foot-candle. Table 1 shows the recommended illumination level for indoor lighting design for different environments.

Table 1: Recommended illumination level.

In proposed strategy first of all site for the project is selected and its indoor area is measured. By using Lux meter the existing illumination level of CFLS is measured. Obtained illumination level is matched with international standards of Illuminating Engineering Society of North America (IESNA). For the area under consideration a new lighting scheme is developed by using measurements of selected area and adding the standards for that specific environment to simulation software DIALUX 4.11. As per design, the hardware is installed and illumination level is measured for LED lights by using Lux meter and results are compared with that of CFL lights prior to installation of LED lights.

In order to check how viable the lightning scheme is, energy savings and cost savings calculations is being made. Finally payback period is calculated to justify the implementation of new lighting scheme.

Case study

The case study is based on 8th floor (7th level) of a commercial building which majorly comprises of offices is operated 12 hours in a day in 1 shift. The area of the 8th floor (7th level) is 11115 ft2. The floor has 21 number of offices, 2 AHU rooms, 2 Stair lobbies, washrooms, 1 data room, 1 electric room, 1 smoke stop lobby, and a store on its 8th floor (7th level). Total lighting load on this Floor is 10.930 KW. The floor was installed with 405 TBS (Tube Rod) lights and 26 CFL (Compact Fluorescent Lamps) suspended 2 ft below from roof. The illumination level on different test points with conventional bulbs (Tube lights and Energy savers) is measured by Lux meter and recorded as in Table 2.

Table 2: Formulates total watts consumed by existing electrical scheme being used.

Office type 01

Height of room: 12.000 ft., Mounting height: 10.000 ft., Light loss factor: 0.80, Values in foot-candles, Scale 1:48 (Table 3). Specific connected load: 0.93 W/sq.ft.=0.16 W/sq.ft./10 fc(Ground area: 224.99 sq. ft.) (Table 4).

Table 3: Data of work plane-1.

Table 4: /strong> Luminaire parts list-1.

Office type 02

Height of room: 12.000 ft., Mounting height: 10.000 ft., Light loss factor: 0.80, Values in foot-candles, Scale 1:87 (Table 5). Specific connected load: 1.06 W/sq.ft.=0.15 W/sq.ft./10 fc (Ground area: 396.01 sq.ft.) (Table 6).

Table 5: Data of work plane-2.

Table 6: Luminaire parts list-2.

Office type 03

Height of room: 12.000 ft., Mounting height: 10.000 ft., Light loss factor: 0.80, Values in foot-candles, Scale 1:62 (Table 7). Specific connected load: 0.89 W/sq.ft.=0.14 W/sq.ft./10 fc (Ground area: 315.01 sq.ft.) (Table 8).

Table 7: Data of work plane-3.

Table 8: Luminaire parts list-3.

Office type 04

Height of room: 12.000 ft., Mounting height: 10.000 ft., Light loss factor: 0.80, Values in foot-candles, Scale 1:91 (Table 9). Specific connected load: 0.90 W/sq.ft.=0.14 W/sq.ft./10 fc (Ground area: 621.01 sq.ft.) (Table 10).

Table 9: Data of work plane-4.

Table 10: Luminaire parts list-4.

Corridor

Height of room: 12.000 ft., Mounting height: 10.00 ft., Light loss factor: 0.80, Values in foot-candles, Scale 1:242 (Table 11). Specific connected load: 0.68 W/sq.ft.=0.32 W/sq.ft. /10fc (Ground area: 518.38 sq.ft.) (Table 12).

Table 11: Data of work plane-5.

Table 12: Luminaire parts list-5.

Figures above exhibit the layout design of LED luminaries for various types of offices under consideration and state the lux levels on different points in foot-candles. Figure 1 shows design layout of Incubator office 01 consist of 6 LED lights of 35 watt each, Figure 2 shows Incubator office type 02 consist of 12 LED lights of 35 watts each, Figure 3 shows Incubator office type 3 consist of 8 LED lights of 35 watt each, Figure 4 shows Incubator office type 04 consist of 16 LED lights of 35 watt, Figure 5 shows layout design of corridor consist of 10 LED lights of 35 watt each. Above All the figures shows the detailed luminary layout for the installation of lights and distance between them horizontally and vertically along with detail of work plane. Similar calculations are made using DIALUX 4.11 for the other miscellaneous rooms i.e., AHU rooms, Lift lobby washrooms, Data room, two stairs, electric room, smoke store lobby and store room.

Figure 1: Layout design of incubator office type 01 by using DIALUX 4.11.

Figure 2: Layout design of incubator office type 02 by using DIALUX 4.11.

Figure 3: Layout design of incubator office type 03 by using DIALUX 4.11.

Figure 4: Layout design of incubator office type 04 by using DIALUX 4.11.

Figure 5: Layout design of corridor by using DIALUX 4.11.

The lighting load of the floor was 10.930 KW which has been replaced with 8.15 KW new lighting load LED lights. The lights have been installed at the height of 10 ft from ground and the illumination level is recorded by Lux meter in foot-candle on work plane (3.00 ft.). The result shows that the lighting level in 8th floor (level 7) has very much improved after installation of LED lights (Table 13).

Table 13: Conventional bulbs vs. LED lights.

Before installation of LED lights the floor was installed with 431 traditional bulbs with lighting load of 10.930 KW. To achieve the recommended illumination level and energy savings through an efficient lighting design and use of LEDs, these conventional bulbs were replaced with LED lights with lighting load of 8.15 KW while fixtures are not replaced. New LED lights are installed in existing fixtures. The wattage of luminaries and installation cost incurred on traditional and LED bulbs is shown in Table 13.

Financial effects

Light usage profile (full load):

Air cooling energy savings=97.86 × 0.19=18.59

Total lighting load with air cooling energy savings=97.86-18.59=79.26

The site is being operated 12 hrs/day and rate of electricity/unit is taken as PKR 12.06.

Annual cost of electricity consumed by conventional bulbs=131.16 × 12.06 × 365 = 577354 PKR

Annual cost of electricity consumed by LED lights=79.26 × 12.06 × 365= 348895 PKR

X = Annual Cost Saving/Year=228639 PKR

Initial investment:

On conventional bulbs=1299900 PKR

On LED lights (excluding fixture cost)=605000 PKR

Y= Difference of Installation Cost=694900 PKR

Simple pay back period (SPBP)

SPBP =Y/X =3.03 years

LEDs are the future technology highly promoted for their low energy consumption, long life, efficiency, reliability, and ease of use in improved and innovative designs and having potential to save energy. Case study for a commercial building Arfa Software Technology Park, Lahore using LEDs is carried out that shows 40% of energy saving and financial savings of 170617 PKR per year with payback period of 3.03 years. The results show that LEDs are best recommended for general lighting application and white LEDs are replacing incandescent and compact fluorescent lamps. The major disadvantage associated with LED lights is that the installation cost of these devices is still at higher side; however this issue can be resolved by replacing just the LEDs and not the fixtures as we have done in this project.