In the ENGR 10 lab (E391), there are 75 long light bulbs (P=100 W) and 6 regular
ID: 1767740 • Letter: I
Question
In the ENGR 10 lab (E391), there are 75 long light bulbs (P=100 W) and 6 regular bulbs (P=60 W). How much energy is consumed lighting the lab during the 3 lab periods (9hours). Calculate the amount of energy saved if all bulbs are replaced by CFL (spiral) bulbs (P=25W). Calculate the amount of natural gas (ft3) needed to provide the energy to keep the lights (long + regular) in the E391 lab on overnight for a month (10 hours per day for 30 days)? In other words, how much extra energy (in terms of cubic feet of natural gas) does the school have to purchase when we don
Explanation / Answer
a)
Total power consumed
P=75*100 +6*60
P=7860 Watts
Converting it in to KW
P=7860/1000 =7.86 KW
Energy consumed for 9 hours
E=P*t =7.86*9
E=70.74 KWH
b)
Power consumed by CFL lamps
P=(75+6)*25 =2025 W
Converting it into KW
P=2025/1000 =2.025 KW
Energy consumed for 9 hours
E =2.025*9 =18.225 KWH
Energy saved is
Es =70.74-18.225 =51.515 KWH
c)
Energy consumed for 30 days
E =7.86*10*30
E=2358 KWH
1 KWH =3.41 cubic feet
E=2358*3.41
E=8040.8 cubic feet of natural gas
d)
Energy stored for continous turning ON of lights
E=7.86*30*24
E=5659.2 KWH
E=5659.2*3.41 =19297.9 cubic feet of natural gas
Ertra energy required is
dE =19297.9-8040.8
dE=11257 cubic feet of natural gas