APWH review

# APWH review - Cost Cost of per Home MBtu Heating1 \$11.0 7...

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Cost per MBtu Cost of Home Heating 1 \$11.0 7 \$1,660 \$18.3 7 \$2,755 \$14.5 1 \$2,177 \$29.3 1 \$3,517 3

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Answers 1. a. 2,000 kcal; b. 8.37 x 10 6 J = 8.37 MJ; c. 7,940 Btu; d. 11.9 minutes. 2. b. The second law of thermodynamics prevents 100 percent conversion of heat to mechanical or electrical energy. A typical coal-fired power plant operates at about 33 percent efficiency, meaning that only one-third of the energy in the coal is converted to electricity. 3. a. 1,941 ccf; b. \$1,748; c. 9.2 years 4. a. 9.57 MBtu; b. 8 percent; c. 1,200 5. a. 2,190 kWh; b. 21.9 percent; c. 45.7 m 2 6. 498 tons 7. a. 4,000; b. Answers vary 8. Battery energy: 4.5 Wh = 4.5 x 10 3 kWh. Cost per kWh: \$1.00 / 4.5 x 10 3 kWh = \$222/kWh. Comparison: Electrical energy from the battery costs \$222 / \$0.10 = 2,220 times as much as that delivered by the power company. 1. 0.750kW x 4hr 2. 0.200kW x 3hr 3. Toaster: 1.150kW x 0.1hr Microwave: 1.3kW x 0.0167hr 4. Wind: 250kW = 0.250MW Nuclear: 1000MW 1000/0.250 = 5. 6.
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APWH review - Cost Cost of per Home MBtu Heating1 \$11.0 7...

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