The interior light of refrigerator is
provided by incandescent lamps whose
switches are actuated by opening of
refrigerator door. Consider a refrigerator
whose 40 W light bulb remains on
continuously as results of malfunction of
the switch. If the refrigerator has a
coefficient of performance of 1.3 and the
cost of electricity is rupees & per kWh. find power consumption for one year
Answers
From calculations, we can assume that the energy-saving bulb does not justify its cost.
Explanation:
The interior lighting of refrigerators is usually provided by incandescent lamps whose switches are actuated by the opening of the refrigerator door. Consider a refrigerator whose 40-W lightbulb remains on about 60 h per year. It is proposed to replace the lightbulb by an energy-efficient bulb that consumes only 18 W but costs $25$25 to purchase and install. If the refrigerator has a coefficient of performance of 1.3 and the cost of electricity is 8 cents per kWh, determine if the energy savings of the proposed lightbulb justify its cost.
We are given that:
Power of light = 40 W
Coefficient of performance = 1.3
Solution:
EL = (W1 - W2 )Δt
EL = (40 - 18)x 60 = 1320 Wh
EL = 1.32 KWh
Refrigerator energy ER = EL = COPR
ER = 1.32 / 1.3 = 1.02 KWh
Total energy = EL + ER = 1.32 + 1.02 = 2.34 KWh
Money saved = Cost x E(total) = 2.34 x 0.08 = 0.19$ per year
Time = Cost / money saved
Time = 25 / 0.19 = 132 year
Theus, The energy saving bulb does not justify its cost.