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Earth’s Changing Environment Lecture 23 Fred’s Utility Bill.
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Transcript of Earth’s Changing Environment Lecture 23 Fred’s Utility Bill.
![Page 1: Earth’s Changing Environment Lecture 23 Fred’s Utility Bill.](https://reader035.fdocuments.us/reader035/viewer/2022062422/56649ec05503460f94bcc4e6/html5/thumbnails/1.jpg)
Earth’s Changing EnvironmentLecture 23
Fred’s Utility Bill
![Page 2: Earth’s Changing Environment Lecture 23 Fred’s Utility Bill.](https://reader035.fdocuments.us/reader035/viewer/2022062422/56649ec05503460f94bcc4e6/html5/thumbnails/2.jpg)
Energy Efficiency
Utility is promoting energy efficiency in two ways.
![Page 3: Earth’s Changing Environment Lecture 23 Fred’s Utility Bill.](https://reader035.fdocuments.us/reader035/viewer/2022062422/56649ec05503460f94bcc4e6/html5/thumbnails/3.jpg)
Space Heating with Natural Gas
Advisory claims that heating with an electric resistance furnace cost $1,400 and heating with natural gas cost $555. This is about 40%.
![Page 4: Earth’s Changing Environment Lecture 23 Fred’s Utility Bill.](https://reader035.fdocuments.us/reader035/viewer/2022062422/56649ec05503460f94bcc4e6/html5/thumbnails/4.jpg)
Energy Use
Energy use shifts with season.
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Cost of Energy
Bill is complicated, but
Electricity costs $0.057/kWh
Gas costs $0.71/ccf
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Furnace Efficiency
80% for gas furnace.
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Air-Conditioner Efficiency - SEER
10% for AC
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Problem and Solution
During February, a San Antonio homeowner used 100 ccf of natural gas for space heating.
Complete combustion of 1 ccf of natural gas releases 1 therm of heat
1 therm = 100,000 Btu of heat. AFUE of the Fred’s furnace = 80. Electric resistance heating releases 3413 Btu
per kWh Natural cost $0.71 per ccf. Electricity costs $0.057 per kWh.
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How much heat did the gas heater supply?
100 ccf 100 therm 100 therm x 0.80 = 80 therm = = 8,000,000 Btu
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What was the cost of the natural gas used?
= 100 ccf x $0.71/ccf = $71
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How much heat would have to be supplied if an electric heater were used? 80 therms = 8,000,000 Btu
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How much electricity would the electric heater use? 8,000,000 Btu / 3413 Btu/kWh = 2,343 kWh
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How much would this electricity cost?
2,343 kWh x $.057 = $134
So the ratio of the cost of the electricity to the cost of natural gas would be $134 / $71 = 1.9
It would cost almost twice as much to heat with electricity!
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How much energy must be supplied at the utility to supply the heater’s electric energy?
2,343 / 0.30 = 7813 kWh 7813 kWh x 3413 Btu/kWh =
26,700,00 Btu = 267 therm So the ratio of the energy
needed to supply electric heating to the energy to supply the gas heat = 267 therm / 100 therm = 2.67
Almost three times as much primary energy is needed to supply electric heat as to supply gas heat.
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Compare the CO2 emission for electric and gas heating
Coal releases 26 tons / QBtu Gas releases 14 tons / QBtu Ratio of CO2 emission coefficients =
26/14 = 1.87 Ratio of CO2 emission =
(Coeff. x Energy)E / (Coeff. x Energy)G = CoeffE / CoeffG x EnergyE / EnergyG = 1.87 x 2.67 = 5.0
Five times as much CO2 is emitted to supply electric heat as to supply gas heat.