1. Energy Overview

2. Topics Covered Energy Resources and Consumption Energy Concepts
Energy Forms
Power
Units
Conversions
Laws of Thermodynamics
Energy Consumption
History
Industrial Revolution
Exponential Growth
Energy Crisis
Present Global Energy Use
Future Energy Needs

3. Energy Measures Joule (J) – basic unit of energy
Amount of energy used when a 1-watt electrical device is turned on for 1 second
Gigajoule (GJ) – 1 Billion (1x109) Joules
1 GJ = as much energy as 8 Gal of gasoline
Exajoule (EJ) = 1 Billion (1x109) Gigajoules
US uses “quad” = quadrillion Btu= EJ
Btu = British thermal unit = 1 Btu = 1055 J

4. Energy The ability to do work or transfer heat
Most energy comes from the sun’s electromagnetic radiation (carried by photons)

5. Power Power is the rate at which work is done Energy = Power x time
Power = Energy / time

6. Relationship to Joules
Common Energy Units
Unit
Definition
Relationship to Joules
Common Uses
calorie
Amount of energy it takes to raise 1 gram of water 1 o C
1 calorie = J
Energy transfer in ecosystems, human food consumption
Calorie
Food Calorie – always shown with a capital C
1 Calorie = 1000 calories = 1 kilocalorie (kcal)
Food labels, human food consumption
British Thermal Unit
(Btu)
Amount of energy it takes to heat 1 lb of water 1 F
1 Btu = 1055 J
Energy transfer in AC, home and water heaters
Kilo-watt hour
(kWh)
Amount of energy expended by using 1 kilowatt of electricity for 1 hour
1 kWh = 3,600,000 J or 3.6 Megajoules (MJ)
Electrical appliances, kWh per year

7. Relationship to Joules
Unit
Definition
Relationship to Joules
Common Uses
Watt (thermal)
Power produced as heat
One joule of energy transferred or dissipated in one second (J/s)
Nuclear power plants produce heat measured in thermal watts
Watt
(electrical)
Power produced as electricity
same
Kilo
=1,000 = 103
1 kW = 103watts
Mega
=1,000,000= 106
1 MW = 106watts

8. Energy Forms Mechanical Two types: potential and kinetic Thermal
Description
Mechanical
Two types: potential and kinetic
Thermal
Heat is the internal energy in substances – the vibration and movement of the atoms and molecules within substances
Chemical
Stored in bonds between atoms in a molecule
Electrical
Results from the motion of electrons
Nuclear
Stored in the nuclei of atoms; it is released by splitting or joining atoms
Electromagnetic
Travels by waves

9. First Law of Thermodynamics
Energy is neither created nor destroyed. (Just like matter)
Ex: Potential energy in a piece of firewood is converted into heat energy.

10. Second Law of Thermodynamics
When energy is transformed, the quantity of energy remains the same, but its ability to do work diminishes.

11. Entropy Second Law of Thermodynamics
All Systems move toward randomness, unless new energy from an outside system is added
Entropy – Randomness
Your room!
A log being burnt
A pot of boiling water

12. Energy Efficiency
Ratio of the amount of work that is done to the total amount of energy that’s introduced into the system initially.
Ex: Fireplace that’s 70% efficient might use 2 kg of firewood to heat a room to 20˚C (68˚ F). A fireplace that’s 10% efficient would require 14 kg to reach 20˚C (68˚ F).

13. Energy Efficiency 2 Chemical energy  Electricity
Coal-burning power plant can convert 1 metric ton of coal containing 24,000 megajoules (MJ) into 8400 MJ of electricity.
8400 MJ is 35% of 24,000 MJ, the process is 35% efficient. (65% is lost as heat)
10% is lost as heat and sound in powerlines – 90% efficient
Incandescent bulbs are 5% efficient.
Total energy efficiency:
x x =  1.6% efficient
Coal  Electricity x Transport x light bulb efficiency = overall efficiency

14. Energy Quality
The ease at which an energy source can be used for work.
High-quality energy source has a convenient, concentrated form.
Ex: Gasoline is good quality because it’s concentrated 44 MJ/kg and easy to convert to work
Wood 20 MJ/kg more difficult to convert to work

15. Energy Use Americans use 10,000 watts of energy continuously 24/365
Most of our energy comes from nonrenewable sources (finite)
2 Types
Fossil Fuels – ancient solar energy stored in chem. Bonds is burned and harness heat energy
Nuclear – Radioactive Materials

16. Pre-Industrial Revolution: Wood
Industrial Revolution: Coal
Middle of 20thCentury: Petroleum
Late 20thCentury: Natural Gas and Coal

17. Worldwide Energy Use Each Country is Different – Use based on:
What’s available
What’s affordable
Environmental Impacts (Developed Countries)
World Use = 495 EJ per year
75 GJ per person per year
3 largest sources - oil, coal and natural gas

18. Developed and cities of developing countries – use fossil fuels
Developing rural areas still use wood, charcoal and animal waste
Commercial Energy Sources – Bought and sold such as coal, oil and natural gas. Sometimes wood, charcoal and animal waste
Subsistence Energy sources – gathered by individuals for their own immediate needs

19. US Energy Use Patterns US has greatest total energy consumption
Canada greatest energy per capita

21. Energy Types and Quality
Best suited for purposes based on
Energy-to-mass ratio
Speed at which they provide/cut off the energy supply
Run a car on coal or firewood? Why or why not?

22. Quantifying Energy Efficiency
2 Processes
Obtaining the fuel
Converting the fuel into work
Energy Return on Energy Investment – EROEI
EROEI = Energy obtained from the fuel / Energy invested to obtain the fuel
Ex: To obtain 100 J of coal from a surface coal mine, 5 J of energy is expended
100 J/5 J = 20

23. Efficiency and Transportation
30% of Energy use in the US is for transportation (movement of people and goods) and uses petroleum
Public ground transportation is more efficient than traveling with one person in a car and air travel.
Energy expended for different modes of transportation in the US
Mode
MJ per passenger-kilometer
Air
2.1
Passenger Car (driver alone)
3.6
Motorcycle
1.1
Train (Amtrak)
Bus
1.7

24. Transportation Contd
½ of all personal vehicles sold are mini-vans, SUVs and pick-up trucks (AKA light trucks)
Poor gas mileage – 20 mpg
Small cars – 45 mpg
2-3% are hybrids – 50 mpg

25. Electricity Generation by coal, natural gas, or wind
No pollutants emitted when used
Pollutants released when fossil fuels are burned
More efficient to transfer to home directly – least transfers – most efficient

27. Grid A network of interconnected transmission lines
Connects power plants and links with users

28. Electricity Efficiency
Coal burning – 35% efficient
Gas combustion – Combined cycle natural gas – 60% efficient
Gas combustion turns first turbine and steam from excess heat turns second turbine
Typical US power plants have 500 megawatt capacity (max output)
Capacity Factor – Fraction of time a plant is operating