Sustainable Energy, SI Edition
2nd Edition
ISBN: 9781337672092
Author: DUNLAP, Richard A.
Publisher: Cengage Learning
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Chapter 1, Problem 18P
To determine
Find the annual heating cost of the second homeowner.
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Problem 10
A homeowner is trying to decide between a high-efficiency natural gas furnace with an efficiency of 95
percent and a ground-source heat pump with a COP of 3.3. The unit costs of electricity and natural gas are
$0.112/kWh and $1.44/therm (1 therm = 105, 500 kJ). Determine which system will have a lower energy
cost.
Replacing incandescent lights with energy-efficient fluorescent lights can reduce the lighting energy consumption to one-fourth of what it was before. The energy consumed by the lamps is eventually converted to heat, and thus switching to energy-efficient lighting also reduces the cooling load in summer but increases the heating load in winter. Consider a building that is heated by a natural gas furnace with an efficiency of 80 percent and cooled by an air conditioner with a COP of 3.5. If electricity costs $0.12/kWh and natural gas costs $1.40/therm (1 therm = 105,500 kJ), determine if efficient lighting will increase or decrease the total energy cost of the building (a) in summer and (b) in winter.
For a building located in London, England with annual heating degree-days (dd) of 5634, a heating load (heat loss) of 42,000 kj/h, and a design temperature difference of 35° C (20° C indoor), estimate the annual energy consumption. If the building is heated with a furnace with an efficiency of 98%, how much gas is burned to keep the home at 20° C? State yourassumptions.
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Sustainable Energy, SI Edition
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- When 1 cu ft of natural gas is burned, 1,050 Btu of heat are produced. In oneday, a building uses 761,250 Btu of heat. How many cubic feet of gas areburned?arrow_forwardFor a building located in Madrid, Spain with annual heating degree-days (dd) of 4654, a heating load (heat loss) of 30,000 kj/h, and a design temperature difference of 30° C (20° C indoor), estimate the annual energy consumption. If the building is heated with a furnace with an efficiency of 92%, how muchgas is burned to keep the home at 20° C? State your assumptions.arrow_forwardHow do I convert 10649 KWh into (KWh/(m2-yr)?arrow_forward
- 1) Heating the water in a 55-gallon water heater requires about 2.0 x 103 kJ of energy. a) Assume the energy came from natural gas with 80% efficiency; how many grams of natural gas are required? b) Assume the energy came from electricity with 80% efficiency and that the electricity was produced from the combustion of coal with 30% efficiency; how many grams of coal are required? For problem above, calculate how much CO2 in grams is emitted to the atmosphere. For a: Use the balanced equation for the combustion of methane (CH4) to determine how many grams of CO2are produced from the amount of natural gas required. For b: Assume that coal produces 5.25 kJ of energy per gram of CO2 produced. Calculate how much CO2 in grams is produced.arrow_forwardA home is heated with propane with a 100,000 BTU furnace size and 95% efficiency. The monthly heating degree days is 5000. Using the energy estimation discussed in this chapter, estimate the monthly and annual gas consumption to heat the building if the home is to be kept 68°F.arrow_forwardThe Energy Efficiency Rating (EER) of an air-conditioning unit is defined asthe ratio of the heat removed in Btu/hr divided by the energy used in watts. Awindow air conditioner is rated at 5,170 Btu. It uses 470 watts of power. Whatis this unit’s EER?arrow_forward
- The Energy Efficiency Rating (EER) of an air-conditioning unit is defined asthe ratio of the heat removed in Btu/h divided by the energy used in watts.The EEI (Edison Electric Institute) names an air-conditioning unit as anEnergy Star unit if it has an EER of 13 or greater. A 21⁄2-ton air-conditioningunit uses 2.41 kilowatts (2,410 watts) of energy. One ton is equivalent to12,000 Btu/h. Can this unit be termed an Energy Star unit?arrow_forwardConsider a 400-MW, 32 percent efficient coal-fired power plant that uses cooling water withdrawn from a nearby river (with an upstream flow of 10-m3/s and temperature 20 °C) to take care of waste heat. The heat content of the coal is 8,000 Btu/lb, the carbon content is 60% by mass, and the sulfur content is 2% by mass. How much electricity (in kWh/yr) would the plant produce each year? How many pounds per hour of coal would need to be burned at the plant? Estimate the annual carbon emissions from the plant (in metric tons C/year). If the cooling water is only allowed to rise in temperature by 10 °C, what flow rate (in m3/s) from the stream would be required? What would be the river temperature if all the waste heat was transferred to the river water assuming no heat losses during transfer? Estimate the hourly SO2 emissions (in kg/h) from the plant assuming that all the sulfur is oxidized to SO2 during combustion.arrow_forwardI need helparrow_forward
- An inventor claims to have developed a refrigerator that at steady state requires a net power input of 1.1 horsepower to remove 12,000 Btu/h of energy by heat transfer from the freezer compartment at 20°F and discharge energy by heat transfer to a kitchen at 70°F. Evaluate this claim. The inventor's claim isarrow_forwardPlease help solve both for homework.arrow_forwardThe annual average insolation for a fixed solar panel in city A is 350 W/m2. On the other hand, city B has a figure of 300 W/m?. For both locations, the solar panel has the capability to convert 17% of the incident energy into electricity. Average annual electricity in City A is 13 000 kWh with an average cost of $0.4/kWh, while in city B, it is 10 000 kWh at a cost of $0.75/kWh. For City A, a. Determine the area of the solar panel needed in order to suffice the average electrical needs of a residence. b. Determine the area of the solar panel needed in order to suffice the average electrical needs of a residence in City B. c. Determine the price per square meter of solar panel in City A if the device has a lifetime of 20 years. Assume that the electricity costs are constant throughout the period. d. Determine the price per square meter of solar panel in City B if the device has a lifetime of 20 years. Assume that the electricity costs are constant throughout the period.arrow_forward
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