Transcript Chapter 1.3 The Energy Cycle

Chapter 1.3
The Energy Cycle
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.
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.
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.
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.
Tidal Energy
• Smallest part of the energy budget
(0.002%)
• Resuts from the sun and moon’s pull on
the Earth’s oceans.
• Powerful enough to slow Earth’s rotation
because of the “tidal bulge”.
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).
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.
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.
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.