2OBJECTIVES: Describe energy, power and the units used to measure them. Apply the laws of thermodynamics.
3ENERGY AND POWER Energy = ability to do work (transfer heat). Kinetic energy – motionPotential energy – storedjoule, calorie, British thermal unit, kilowatt-hourPower = ratewatt (kW, MW)
4Source of Energy Energy Tasks Relative Energy Quality (usefulness) ElectricityVery high temperature heat(greater than 2,500°C)Nuclear fission (uranium)Nuclear fusion (deuterium)Concentrated sunlightHigh-velocity windVery high-temperature heat (greater than 2,500°C) for industrial processes and producing electricity to run electrical devices (lights, motors)High-temperature heat(1,000–2,500°C)Hydrogen gasNatural gasGasolineCoalFoodMechanical motion to movevehicles and other things)High-temperature heat(1,000–2,500°C) forindustrial processes andproducing electricityNormal sunlightModerate-velocity windHigh-velocity water flowConcentrated geothermal energyModerate-temperature heat(100–1,000°C)Wood and crop wastesModerate-temperature heat(100–1,000°C) forindustrial processes, cooking, producingsteam, electricity, andhot waterFigure 2.13Natural capital: categories of the qualities of different sources of energy. High-quality energy is concentrated and has great ability to perform useful work. Low-quality energy is dispersed and has little ability to do useful work. To avoid unnecessary energy waste, you should match the quality of an energy source with the quality of energy needed to perform a task.Dispersed geothermal energyLow-temperature heat(100°C or lower)Low-temperature heat(100°C or less) forspace heatingFig. 2-13, p. 44
5ENERGY LAWS: TWO RULES WE CANNOT BREAK 1st law of thermodynamics: we cannot create or destroy energy.2nd law of thermodynamics: energy quality always decreases.Mechanical energy (moving, thinking, living)Chemicalenergy(photosynthesis)SolarenergyChemicalenergy(food)WasteHeatWasteHeatWasteHeatWasteHeat
6Application IOne pound (lb) of bituminous coal contains 12,000 BTUs of energy. Suppose a coal‑fired power plant needs 3,600 BTU's of heat to produce one kilowatt‑hour of electricity. This plant has a 1 Megawatt output. Showing all steps, calculate the following:A. How much coal is required to produce one kilowatt‑hour of electricity?B. How much coal must be burned to keep the plant at full output for 24 hours?
7Application IIThe conventional gasoline‑powered 2004 Honda Civic is one of the best gas‑powered cars in its class for mileage. The conventional Honda Civic gets 35 MPG during city driving (40 MPG Freeway). When the exact same car is given a hybrid‑electric engine, mileage is 47 MPG city and 48 MPG Freeway. $21, 000 is the cost of the Honda Civic Hybrid, $16,000 is the cost of the Honda Civic conventional, depending on features. You plan to drive mostly in the city, to and from work and for weekend errands. You expect to drive 8,000 miles a year in city driving, plus another 4,000 miles in longer trips that would count as "highway."A.) How much would you spend on gas for the hybrid Civic in a year, assuming gas cost $2.50 a gallon?B.) How much would you spend on gas for the conventional Civic in a year, assuming gas cost $2.50 a gallon?C.) How long would it take for the savings in gas costs to offset the increase in the price of the hybrid Civic?
8Application IIA.) How much would you spend on gas for the hybrid Civic in a year, assuming gas cost $2.50 a gallon?
9Application IIB.) How much would you spend on gas for the conventional Civic in a year, assuming gas cost $2.50 a gallon?
10Application IIC.) How long would it take for the savings in gas costs to offset the increase in the price of the hybrid Civic?
11FRQAnswer the questions below regarding the heating of a house in the Midwestern United States. Assume the following.The house has 2,000 square feet of living space.80,000 BTU’s of heat per square foot are required to heat the house for winter.Natural gas is available at a cost of $5.00 per thousand cubic feet.One cubic foot of natural gas supplies 1,000 BTU’s of heat energy.The furnace in the house is 80 percent efficient.A. Calculate the following, showing all the steps of your calculations, include units.The number of cubic feet of natural gas required to heat the house for one winter.The cost of heating the house for one winter.B. Identify and describe three actions the residents of the house could take to conserve heat energy and lower the cost of heating the house.C. The residents decide to supplement the heating of the house by using a wood-burning stove. Discuss two environmental impacts, one positive and one negative, of using the wood-burning stove.
12FRQA. Calculate the following, showing all the steps of your calculations, include units.The number of cubic feet of natural gas required to heat the house for one winter.The cost of heating the house for one winter.
13OBJECTIVES: Describe energy, power and the units used to measure them. Apply the laws of thermodynamics.