1. Energy, Power and Climate Change
Energy Sources and Consumption
Fossil Fuels

2. Energy Conversions
Production of electrical power often starts with the release of thermal energy from a fuel
Conversion of energy into work requires a cyclical process, and energy is lost to the surroundings
Lost energy is unavailable and is known as degraded energy

3. Efficiency

4. Sankey Diagrams: Electrical Power Production

5. Renewable vs. Nonrenewable Energy Sources
Renewable resources - cannot be used up
Examples:
Hydro (dams/tides)
Solar (Photovoltaic cells, solar heaters)
Wind
Biofuels
Geothermal

6. Non-renewable resources - can be used up and eventually run out
Examples:
Fossil fuels - coal, oil, natural gas
Nuclear

7. Other things to consider:
Nuclear power sources are non-renewable, but supply available can make the source effectively renewable
A fuel can be managed in a renewable or nonrenewable way - for example, we can replant trees at the same rate that they are cut down

8. Possible sources of energy:
Sun’s radiated energy
Gravitational energy of the Sun and the Moon
Nuclear energy stored within atoms
Earth’s internal heat energy

9. Energy Density:
Can be used to compare fuels (including transportation costs)
Energy liberated per unit mass of fuel consumed
Measured in J kg-1

10. Comparison of Energy Sources

11. World’s Energy Consumption

12. Energy Sources used to Generate Electricity
Renewables include hydro (16.2%), combustible renewables (1.0%), and other (wind, solar, geothermal) (0.8%)

13. Fossil Fuels Coal, oil and natural gas
Accumulations of dead matter exposed to high temperatures and pressures over millions of years
Coal - plant matter in swamps
Oil - dead marine matter
Natural gas - by-product of oil production

14. Historical and Geographical Factors
Industrial Revolution - large scale manufacturing
Textiles, steam engine, iron and steel
Increased rate of energy usage
Industries developed near fossil fuel deposits
Growth of cities, increased cost due to transportation of fuels

15. Energy Transformations
Solar energy converted by photosynthesis into living plant matter
Plant matter converted to fossil fuels
Fuel burned and converted to thermal energy
Thermal energy converts water to steam
Steam turns turbines

16. Flow Chart

17. Rate of Fuel Consumption By Power Stations
Calculate the typical rate (in kg per hour and tons per hour) at which coal must be supplied to a 500 coal MW fired power station. (Coal power stations have a typical efficiency of 35%, and coal has an energy density of 33 MJ per kg).

18. How much power must be released from the fuel?
You need 500 MW or 5 x 108 J s-1
Coal is 35% efficient, so…….
Energy in = 1.43 x 109 J s-1

19. How much coal do you need?
If the energy density of coal is 33 MJ per kg (or 3.3 x 107 J kg-1), then:

20. Efficiencies of Fossil Fuels
Typical Efficiency
Current Maximum Efficiency
Coal
35%
42%
Natural Gas
45%
52%
Oil
38%

21. Advantages of Fossil Fuels
Very high “energy density” (a lot of energy released from a small mass)
Easy to transport
Cheap when compared to other sources of energy
Power plants can be built anywhere with good transport links and water availability
Can be used directly in the home to provide heating

22. Disadvantages of Fossil Fuels
Combustion products produce pollution, esp. acid rain
Combustion products produce greenhouse gases
Extraction of fossil fuels can damage the environment
Nonrenewable
Coal-fired plants require large amounts of fuel