World Energy SourcesChapter 8, section 8.1

Read pages 307-317 (top half of page) and 322-328

Goals: Understand primary and secondary, renewable

and non-renewable energy sources Understand, interpret, and sketch Sankey

diagrams Understand energy density of fuel sources and

specific examples Describe basic features of fossil fuel power

stations as well as wind generators, and hydroelectric (solar power cells and nuclear power will come during/after our quantum and nuclear unit)

Solve problems related to energy, energy density, and, specifically, wind power generation.

Energy Sources Primary Energy: Fuel in its initial form;

one that has not been transformed prior to being used by a consumer• Some form of fossil fuel (chemical potential

energy): Coal Crude oil Natural gas

• Wind (kinetic energy) Converted to electricity (wind generator) used to do work (windmill)

Energy Sources Secondary Energy:

• Energy sources produced from primary energy sources

Electricity—most important secondary source

unleaded gasoline Hydrogen

THE primary source… Nearly all sources of energy are

originally derived from the radiation from the sun in one way or another.

Radiation from the sun is used in photosynthesis by plants

Plants also remove carbon dioxide from the atmosphere, and are what is known as “Carbon stores” as a result.

Renewable vs. Non-renewable Non-Renewable Energy Source:

• The energy source will eventually be completely used up and will run out.

• Even if there is still some of the energy source left, it will not be cost-effective to use it, so it essentially has been “used up”

• Examples: Coal; oil; natural gas; nuclear materials

Renewable Energy Sources:• The source of the energy cannot be

“used up”• The source of the energy is replenished

so that there is a relatively constant supply of the source.

• Examples: Solar power (photovoltaic cells) hydroelectric power Wind; biofuels Tides and waves

Renewable vs. Non-renewable

World energy consumption What do you predict would be the

breakdown of the world’s energy copnsumption of the following fuels:• Hydroelectric• Nuclear• Natural gas• Coal• Oil• Other renewables

How about the US?

World energy consumption

https://ourfiniteworld.com/2015/06/23/bp-data-suggests-we-are-reaching-peak-energy-demand/

Energy Density Specific Energy

• The amount of energy that can be released per kilogram of fuel

• Units J·kg-1

Energy Density• The amount of energy that can be

released per cubic meter of fuel• Units J·m-3

𝑺𝒑𝒆𝒄𝒊𝒇𝒊𝒄 𝒆𝒏𝒆𝒓𝒈𝒚=𝒆𝒏𝒆𝒓𝒈𝒚 𝒓𝒆𝒍𝒆𝒂𝒔𝒆𝒅𝒎𝒂𝒔𝒔𝒐𝒇 𝒇𝒖𝒆𝒍

Energy Densities of some common fuels (table on p. 311)

Fuel Type Specific Energy / MJ·kg-1

Energy density / MJ·m-3

wood 16 104

coal 20-60 (20-60) x 106 petrol (gasoline) 45 35 x 106

Natural gas (at 1 atm) 55 3.5 x 104

Uranium (U-235) 8 x 107 1.5 x 1015 Deuterium (Fusion) 3 x 108 6 x 1015

Water falling through 100 m in a hydroelectric plant

10-3 103

Sample Problem 1 A fossil-fuel power station has an

efficiency of 25% and generates 1200 MW of useful electrical power. The specific energy of the fossil fuel is 52 MJ·kg-1 . Calculate the mass of fuel consumed each second.