Energy Saving: Lighting Calculation (Unpredictable But Significant)

When I ask to all my friends, my clients and my customers, are you have been saved energy from lighting system? All of them answered the result of saving from lamps or lighting system was not significant. Why? Because lamps just a little loads compare than others loads (motors, fans, pumps, etc). Yes, that's true. But otherwise, it's FALSE!!!

Why? Let's see the calculation example below after you read where are the energy saving placed.

In Lighting Systems, there are many way's to save the energies if we know and how to do that. I'll try to explain it in details.



Where are the saving placed ?



1. Lighting Control

• Timer Switches to turn off lights after a fixed period has passed
• Occupancy sensor / movement detectors to turn off lights when no movement has been detected for a certain period
• Photoelectric cells / daylight harvesting sensor to control lights near windows. When bright exterior light is available, lamps are turned off or dimmed
• Programmable timers to switch lights on and off at predetermined times
• Dimmable light to maintain a low level of illumination at off-peak periods
• Voltage regulators to optimize the power consumed. Ballast perform this function on fluorescent lighting. Voltage regulators are also available for other lighting types such as high pressure sodium lamps.

2. Types of Lamps

Nowadays, there are a lot of types of lamps. But, we not realize that each of lamps have different characteristic and specification. For the example, the old fluorescent lamp, with T12, usually have rated power up to 40W. Today, with same intensity output of light, you can use T8 with rated power up to 36W. The conclusion is you must know about the characteristic and the specification of lamp that will be used.


3. Reflectors



Around 70% of fluorescent tube's light is directed sideways and upwards to the light fittings surfaces.


High efficiency reflector has a spectral efficiency of over 90%. This means two lamps may be replaced by a single lamps. In this way it's possible to reduce energy costs attributed to lighting by 50% or more.




4. Changing Conventional Ballast (Electromagnetic) With Electronic Ballast

Conventional Ballast have power factor (cos phi) up to 0.45.
Electronic Ballast have power factor (cos phi) up to 0.95.
What are the differences? See the calculation in end of this page.


5. Don't want to change Conventional Ballast (Economics reasons), Use Special Capacitor For Lamps

If you don't want to change Conventional Ballast because you have economic reasons (usually for home application), I have the alternatives. Use Special Capacitor for lamps. This capacitor had special schematic wiring diagram, so why you must use Special Capacitor for lamps.

Conventional Ballast without special capacitor have power factor (cos phi) up to 0.45.
Conventional Ballast with special capacitor have power factor (cos phi) up to 0.95.
What are the differences? See the calculation in end of this page.



Near from the end, The Real Calculation...

When I go with my friend to one of his customer, I just ask for their existing lighting system. They says that using all systems as similar as my design system before I explain my design to them. But they have some systems that still not applicable yet. They said that after used the lighting system, they can save the electrical bills up to 50% / months. I'm aghast with their statement. It's same with my calculation that shown below.

For this calculation, electricity rate was from my region / my country electricity goverment factory. The calculation was only in one point that include two lamps in one housing / fitting. Power of each lamp was 4o Watt, works in 220VAC 50Hz. And applicable for industrial and home applicances.

• USING CONVENTIONAL BALLAST NOR SPECIAL CAPACITOR AND T12 40W LAMP (pf = 0.45)

I = (2 x 40W) : (220 VAC x 0.45) = 0.808 A
P = 0.808 x 220VAC = 177.76 Watt
Electricity used per month (1 kWh = Rp. 480.-)
12 hours / day x 30 days x 177.76 Watt = 63,993.6 Watt.Hours = 63.994 kWh
Electricity bill per month (exclude basic load type value bill):
Rp. 480.- x 63.994 kWh = Rp. 30,716.93

• USING ELECTRONIC BALLAST OR SPECIAL CAPACITOR AND T8 36W LAMP(pf = 0.95)

I = (2 x 36W) : (220 VAC x 0.95) = 0.344 A
P = 0.344 x 220VAC = 75.68 Watt
Electricity used per month (1 kWh = Rp. 480.-)
12 hours / day x 30 days x 84.26 Watt = 27,244.8 Watt.Hours = 27.245 kWh
Electricity bill per month (exclude basic load type value bill):
Rp. 480.- x 30.334 kWh = Rp. 13,077.6

TOTAL SAVING PER MONTH
Rp. 30,716.93 - Rp. 13,077.6 = Rp. 17,639.33

It's means you can save 57.43% / month

If you needs the details, please contact me.