Traffic lights are being converted from incandescent bulbs to LED arrays to save

Question

Traffic lights are being converted from incandescent bulbs to LED arrays to save operating and maintenance costs. Typically each incandescent light uses three 100-W bulbs, one for each color R,Y,G,A competing LED array consists of 61 LEDs with each LED requiring 9V and drawing 20mA of current. There are three arrays per light - R,Y,G,A small city has 1560 traffic signals. Since one light is always on 24/7, how much can a city save in one year if the city buys their electricity at 7.2cents per kWh?

Explanation / Answer

a)

Power consumption when there are incandescent bulbs in use:

Since one light of(R,Y,G) is always on so the power consumption in one year is : 100WX365X24 h = 876000 Wh/1000 = 876kWh power consumption.

Total amount spent on the incandescent bulbs : 876kWh*7.2cents per kWh = 6307 cents

b)

Power consumption when there are LED Arrays:

There are three arrays per Light(R,Y,G) , means total LEDs = 61*3 = 183 LEDs

Power consumption for a single LED   ,we have to use the formula:

P (Watts)= Voltage(volts) XCurrent (A)

P = 9 X20X10^-3

P = 180/1000 = 0.18 Watts

So for 183 LEDs power consumption = 183X0.18 = 32.94 Watts

Since one light of(R,Y,G) is always on so the power consumption in one year is = 32.94X365X24 = 288554.4 Wh/1000=288.554kWh power consumption.

Total amount spent on the LEDs : 288.55kWh*7.2cents per kWh = 2077 cents

So the saving is of about : 6307

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.