A facility uses 150 KL/Yr of hot water. If the hot water is set at 55 degree C and the input water averages 20 degree C, What is the annual energy required to heat the water?
Calculate the annual operating cost if the water is heated by an electric heater (Efficiency=0.90), and a gas water heater efficiency = 0.70. Electricity cost is Rs. 7/Kwh and gas is Rs. 1/Kwh.
Q = m x Cp x Delta T
= 150000 L/Yr x 1 Kg/L x 4.186 KJ/degree C-Kg x 35 degree C
= 21976500 KJ/Yr
Kwh/Yr = 21976500/3600 = 6104.58 Kwh/Yr
For the electric water heater:
Operating Cost, Rs/Yr = 6104.58 Kwh/Yr x Rs. 7/ 0.90 = Rs.47480/Yr
For the gas water heater:
Operating Cost, Rs/Yr = 6104.58 Kwh/Yr x Rs. 1/ 0.70 = Rs.8720.82/Yr
Savings = 47480 - 8720 = Rs. 38760
Gas is definitely cheaper. Thanks for the proof.
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