1. Energy Sources: Overview

2. What is Energy? Definition Units The Value of Energy
“The capacity to do work.” What is work?
“Movement that occurs against a restraining force.”
Work = force x distance
Many types/forms of energy
Heat, light, sound, electrical, kinetic, etc
Heat energy
Due to random movement of atoms/molecules
Heat flow between two bodies in thermal contact is determined by their relative temperature. Temperature is measure of “average” heat content.
Units
SI unit: joule, J.
Older unit: calorie, cal. 1 cal = J.
Food calories are really kilocalories
The Value of Energy
We do not value energy, just the services it provides (heat, transportation, light, movement, etc)

3. Uses of Energy Energy Sectors Utilities Transportation Agriculture
Power plants (generation of electricity)
Electricity is distributed and used in homes and businesses
Heat, light, power to appliances, etc
Transportation
Travel powered by combustion engines
Agriculture
Tractors and other labor-saving devices
Industrial
Manufacture of materials
Energy to provide other goods and services required by society
Domestic
Home heating
Backup generators

4. Comparison of Energy Sources
What Criteria to Use?
Cost
Internal vs external costs
Resources
Nonrenewable
Renewable
Exhaustible
Impact on environment/health
Versatility
Variety of potential uses
Energy content
How measured?
Per unit mass
Per unit volume

5. Environmental Impact
In what ways does our energy system impact our environment? List as many as you can.
Recovery & Refinement
Mining
Dam construction
Waste generation
Transport & Storage
Spills, leaks
Energy Production
Air pollution
Thermal pollution
Waste Disposal
Spent fuel (esp nuclear)

6. Energy Sources What are our main sources of energy? Fossil fuels
Oil, natural gas, coal
Nonrenewable
Environmental impacts?
Nuclear fission
Sources: uranium, plutonium
Hydroelectric power
Ultimate sources: the sun (the hydrologic cycle)
Renewable
Other sources
Solar heating, solar power, photovoltaics, geothermal, tidal, biomass energy, wind energy

7. Energy Production by Source (2003)
Global
OECD Countries
OECD = Organization for Economic Cooperation and Development
30 member countries committed to democracy and a market economy
all members are “first world” countries, including the US, the EC, Australia, and Canada.

8. Energy Production by Region (2003)
Global
OECD Countries

9. US Energy Sources: Historical Trends
Transitions: wood  coal  petroleum
Current main sources in US:
Petroleum
Natural Gas
Coal
Nuclear fission
Hydroelectric

10. US Energy Flow (2000)

11. Electricity Production
Questions
How is it produced?
Why is electricity so useful?
Usefulness of electricity
Many electrical appliances
Readily converted to other forms of energy with high efficiency
Mechanical (electric motors), heat, light, etc
Methods of Production
Fossil fuel combustion
Nuclear power
Hydroelectric power
Other
Geothermal power, solar power, wind turbines, fuel cells & batteries
Storage
Main problem (cannot be easily stored)
What are the main methods of electricity storage?
Chemical (storage batteries; hydrogen generation)
Capacitors
Mechanical batteries
Hydroelectric storage

12. Importance of Electric Motors
Replaced steam-mechanical engines (figure on the left)
Inefficient
Lots of energy lost to friction
Less than 10% efficiency
Entire assembly must be running
Prone to failure
Failure anywhere in transmission line shut down the entire apparatus
Inflexible
Could not control power at individual stations
Dangerous
Lots of moving parts
Cumbersome
Noisy

13. Electricity Production

14. Thermoelectric Power Types of Thermoelectric Power Plants
How is the heat generated?
Combustion of chemical energy sources
Based on energy produced by a combustion reaction
King Coal
Nuclear power plants
Based on nuclear fission

15. Thermoelectric Power Plants

16. Heat Engines Question What is a heat engine?
A heat engine is any device designed to convert thermal energy into mechanical energy
The thermal energy can originate from a variety of other energy sources (chemical energy, nuclear energy, etc)
Conversion is usually due to the thermal expansion of a gas
Examples
Thermoelectric power plant
Internal combustion engines in motor vehicles
[Reverse heat engines: refrigerators (heat pumps).]

17. Internal Combustion Engines (ICEs)
Four-stroke cycle engines
Also called Otto cycle engines
ICEs: pistons moved by expansion due to fuel combustion
Intake stroke
Compression stroke
Power stroke
Exhaust stroke

18. Efficiency of Heat Engines
Source of the Energy
Where does the energy come from in chemical/nuclear reactions?
Energy Transformations
What are the energy transformations that occur in a power plant?
Efficiency of Transformations
Can they be 100% efficient? Why or why not? If not, what limits the ultimate efficiency?
Thermodynamics
First Law of Thermodynamics
Energy can be neither created nor destroyed.
“There is no such thing as a free lunch.”
Second Law of Thermodynamics
The total entropy (“randomness”) of the universe can never decrease.
“You can’t break even.”
Maximum efficiency
of a heat engine is