Chapter 16 Energy Concepts. OBJECTIVES: Describe energy, power and the units used to measure them. Apply the laws of thermodynamics.

Chapter 16Chapter 16

Energy ConceptsEnergy Concepts

OBJECTIVES:OBJECTIVES:

Describe energy, power and the units Describe energy, power and the units used to measure them.used to measure them.

Apply the laws of thermodynamics.Apply the laws of thermodynamics.

ENERGY AND POWERENERGY AND POWER

Energy = ability to do work (transfer heat).Energy = ability to do work (transfer heat). Kinetic energy – motionKinetic energy – motion Potential energy – storedPotential energy – stored joule, calorie, British thermal unit, kilowatt-joule, calorie, British thermal unit, kilowatt-

hourhour Power = ratePower = rate

watt (kW, MW)watt (kW, MW)

Fig. 2-13, p. 44

Low-temperature heat (100°C or less) for space heating

Moderate-temperature heat (100–1,000°C) for industrial processes, cooking, producing

steam, electricity, and hot water

Very high-temperature heat (greater than 2,500°C) for industrial processes and producing electricity to run electrical devices (lights, motors)

Mechanical motion to move vehicles and other things) High-temperature heat (1,000–2,500°C) for industrial processes and producing electricity

Dispersed geothermal energyLow-temperature heat (100°C or lower)

Normal sunlightModerate-velocity windHigh-velocity water flowConcentrated geothermal energyModerate-temperature heat

(100–1,000°C)Wood and crop wastes

High-temperature heat (1,000–2,500°C)Hydrogen gasNatural gasGasolineCoalFood

ElectricityVery high temperature heat (greater than 2,500°C)Nuclear fission (uranium)Nuclear fusion (deuterium)Concentrated sunlightHigh-velocity wind

Source of Energy RelativeEnergy Quality

(usefulness)

Energy Tasks

ENERGY LAWS: TWO RULES WE ENERGY LAWS: TWO RULES WE CANNOT BREAKCANNOT BREAK

1st law of thermodynamics: we cannot 1st law of thermodynamics: we cannot create or destroy energy.create or destroy energy.

2nd law of thermodynamics: energy quality 2nd law of thermodynamics: energy quality always decreases.always decreases.

Chemicalenergy(food)

Solarenergy

WasteHeat

WasteHeat

WasteHeat

WasteHeat

Mechanicalenergy

(moving,thinking,

living)

Chemical energy

(photosynthesis)

Application IApplication IOne pound (lb) of bituminous coal contains 12,000 BTUs of One pound (lb) of bituminous coal contains 12,000 BTUs of

energy. Suppose a coal‑fired power plant needs 3,600 energy. Suppose a coal‑fired power plant needs 3,600 BTU's of heat to produce one kilowatt‑hour of electricity. BTU's of heat to produce one kilowatt‑hour of electricity. This plant has a 1 Megawatt output. Showing all steps, This plant has a 1 Megawatt output. Showing all steps, calculate the following:calculate the following:

A. How much coal is required to produce one kilowatt‑hour of A. How much coal is required to produce one kilowatt‑hour of electricity?electricity?

B. How much coal must be burned to keep the plant at full B. How much coal must be burned to keep the plant at full output for 24 hours?output for 24 hours?

Application IIApplication IIThe conventional gasoline‑powered 2004 Honda Civic is one of the best The conventional gasoline‑powered 2004 Honda Civic is one of the best

gas‑powered cars in its class for mileage. The conventional Honda gas‑powered cars in its class for mileage. The conventional Honda Civic gets 35 MPG during city driving (40 MPG Freeway). When the 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 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 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 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 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 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 driving, plus another 4,000 miles in longer trips that would count as "highway.""highway."

A.) How much would you spend on gas for the hybrid Civic in a year, A.) How much would you spend on gas for the hybrid Civic in a year, assuming gas cost $2.50 a gallon?assuming gas cost $2.50 a gallon?

B.) How much would you spend on gas for the conventional Civic in a B.) How much would you spend on gas for the conventional Civic in a year, assuming gas cost $2.50 a gallon?year, assuming gas cost $2.50 a gallon?

C.) How long would it take for the savings in gas costs to offset the C.) How long would it take for the savings in gas costs to offset the increase in the price of the hybrid Civic?increase in the price of the hybrid Civic?

Application IIApplication II

A.) How much would you spend on gas for the A.) How much would you spend on gas for the hybrid Civic in a year, assuming gas cost hybrid Civic in a year, assuming gas cost $2.50 a gallon?$2.50 a gallon?

Application IIApplication II

B.) How much would you spend on gas for the B.) How much would you spend on gas for the conventional Civic in a year, assuming gas conventional Civic in a year, assuming gas cost $2.50 a gallon?cost $2.50 a gallon?

Application IIApplication II

C.) How long would it take for the savings in C.) How long would it take for the savings in gas costs to offset the increase in the price gas costs to offset the increase in the price of the hybrid Civic?of the hybrid Civic?

FRQFRQAnswer the questions below regarding the heating of a house in the Answer the questions below regarding the heating of a house in the

Midwestern United States. Assume the following.Midwestern United States. Assume the following. The house has 2,000 square feet of living space.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 80,000 BTU’s of heat per square foot are required to heat the house for

winter.winter. Natural gas is available at a cost of $5.00 per thousand cubic feet.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.One cubic foot of natural gas supplies 1,000 BTU’s of heat energy. The furnace in the house is 80 percent efficient.The furnace in the house is 80 percent efficient.

A. Calculate the following, showing all the steps of your calculations, A. Calculate the following, showing all the steps of your calculations, include units.include units. The number of cubic feet of natural gas required to heat the house for one The number of cubic feet of natural gas required to heat the house for one

winter.winter. The cost of heating 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 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.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 C. The residents decide to supplement the heating of the house by using a wood-burning stove. Discuss two environmental impacts, one a wood-burning stove. Discuss two environmental impacts, one positive and one negative, of using the wood-burning stove.positive and one negative, of using the wood-burning stove.

FRQFRQA. Calculate the following, showing all the steps of your calculations, A. Calculate the following, showing all the steps of your calculations,

include units.include units. The number of cubic feet of natural gas required to heat the house for one The number of cubic feet of natural gas required to heat the house for one

winter.winter. The cost of heating the house for one winter.The cost of heating the house for one winter.

OBJECTIVES:OBJECTIVES:

Describe energy, power and the units Describe energy, power and the units used to measure them.used to measure them.

Apply the laws of thermodynamics.Apply the laws of thermodynamics.