The Energy Cycle

1
Chapter 1.3

• The Energy Cycle

2
The Energy Cycle

• The movement of energy into and out of the Earth
  system.
• Different than the previous cycles we have
  learned about.
• More like a scale.
• When you measure on a scale you want the two
  sides to balance.
• What is on one side should equal what is on the
  other side.

3
The Energy Cycle Continued

• The amount of energy entering a system should
  equal the amount of energy leaving a system.
• If a system were to take in more energy than it
  released, the system would increase in
  temperature.
• If it released more energy than it took in,
  temperatures would decrease.
• Because of this balance-scale nature, scientists
  refer to the energy cycle as the energy budget
• There are 3 main sources of energy in the energy
  budget solar energy, geothermal energy, and
  tidal energy.

4
Solar Energy

• Most of the energy that enters the Earth
  system(99.985) system comes from the Sun.
• Solar energy drives the winds, ocean currents,
  and waves.
• It is also the source of the energy that causes
  rocks to weather and soil to form.

5
Geothermal Energy

• Heat from within the Earth (0.013)
• Geothermal energy is responsible for driving the
  tectonic plates, powering volcanoes, geysers and
  earthquakes, and also contributes to rock
  formation.

6
Tidal Energy

• Smallest part of the energy budget (0.002)
• Resuts from the sun and moons pull on the
  Earths oceans.
• Powerful enough to slow Earths rotation because
  of the tidal bulge.

7
Maintaining the Balance

• Incoming energy must go somewhere.
• About 40 of it is reflected back into space.
• Albedo
• The percentage of energy that is reflected
  without being changed.
• A forest has a low albedo (5-10 reflected).
• A snow field has a high albedo (80-90 reflected).

8
The Laws of Thermodynamics

• Energy follows predictable rules that explain
  what it will do.
• Thermodynamics is the branch of physics that
  deals with how heat energy is converted into
  other forms of energy.
• The laws of thermodynamics deals with how energy
  will flow.

9
First Law of Thermodynamics

• Energy can never be created or destroyed, only
  changed from one form to another.
• Example)
• Solar energy is stored in plants which die and
  eventually become fossil fuels.
• Fossil fuels are burned at electrical power
  plants and generate electricity, which can then
  power a light bulb.

10
Second Law of Thermodynamics

• When energy changes, it is converted from a more
  useful, more concentrated form to a less useful,
  less concentrated form.
• Unlike water which can convert from liquid to
  solid back to liquid without harm, energy cannot
  be recycled completely.
• Some energy will always be lost, usually in the
  form of heat.