In: Chemistry
The electric usage of LED is 8 watts and incandescent bulbs take up 40 watts. The lifetime of LED bulbs is 25 000 hours and the lifetime for incandescent bulb is 2500 hours. How much energy could be saved each year by replacing incandescent bulbs with LED bulbs? Assume that six 40-watt lamps arer lit an average of three hours a night and they are each replaces with 8 watt LED-bulbs.
time in a year( in hr)=365 *24 hrs=8760 hrs
As the lifetime for incandescent bulb is 2500 hours ,so no of bulbs required each year (replaced)=8760/2500=3.5 =4(approx)
So total bulbs required =6* 4=24 bulbs
Energy consumed by bulb=E=Power(p) *time(t)
Energy consumed by 24 bulbs (each year) =24 * 40 W* (time in a year in seconds)
(time in a year in seconds)=365 days* 24 hr/day *3600 s/hr=31536000 s
Energy consumed by 24 bulbs (each year) =24 * 40 j/s* 31536000 s
(W=j/s) =30274560000J =30274560 KJ
now lets calculate energy consumed by LED( six) in a year= 6* 8W* (time in a year in seconds)
=6* 8 j/s*31536000 s
=1513728000J
=1513728 KJ
energy saved by replacement=energy consumed by bulbs-energy consumed by LED=30274560 KJ-1513728 KJ
=28760832J