Energy and Society
What is meant when we are told to conserve energy?
How is this different from the physics idea of the conservation of energy?
How does Oil, wind, solar etc relate physics to energy in today’s society?
Why are the major sources of energy in the USA from Coal, oil and natural gas?
These are known as hydrocarbons…what does this mean?
Hydrocarbons are VERY efficient sources of energy
This means that the energy required to break the hydrocarbon bond is less
than the energy produced in the reaction
This is not true for most reactions in chemistry
Why are hydrocarbons good for creating energy?
Hydrocarbons react with oxygen
CH4 + 2O2 à CO2 + 2H2O + energy (methane)
C3H8 + 5O2 à 3CO2 + 4H2O + energy (propane)
C8H18 + 25O2 à 16CO2 +18H2O + energy (gasoline)
What are the products for ALL these reactions?
What are some side affects using hydrocarbons?
Why should we be concerned about CO2?
Natural component of the atmosphere--> balance
excess CO2 destroys balance --> reflect heat back to earth
Global warming--> yea or nay
Global Warming
Earth is warming
Question is WHY is it warming
Natural Cycle on earth or Human caused cycle
CO2 levels in atmosphere is shown to be the cause of the warming trend
Historic values 260-290 ppm
Today’s values ~370 ppm
Where is the CO2 coming from?
Possible outcomes of warming climate
Rising sea levels due to glaciers melting
Global sea levels have risen by about 0.1 inch (2.8 millimeters) a year over the
past decade.
If all the ice on Greenland were to melt into the North Atlantic Ocean, global sea
levels would rise by about 21.3 feet (6.5 meters)
Energy Resources
Coal
Oil
Natural Gas
Methane
Wind
Water
Solar
Biogas
Hydrogen
Waste to energy
Nuclear
Which of these are renewable and which are non-renewable?
Coal
Accumulate plant debris
Where does coal form?
Compaction and leaching
removes oxygen and hydrogen & leaves carbon
What are the stages of coal formation
Initial compaction--> peat
Shallow burial
increases temperature--> lignite
Increase pressure and temp.
Increases C--> bituminous coal
Metamorphism--> anthracite
C135H96O9NS --> aprox. Formula
Coal is a hydrocarbon
Problems with using coal?
Very dirty
releases sulfur into atmosphere
Centralia Pennsylvania
Fire started 1962
Due to burning trash in an old coal pit..caught vein.
Several times they thought it was out but wasn’t…started burning underground.
For 20 years flooded mine and tried all methods to extinguish but can’t
By the early 80’s the fire had affected 200 acres & CO levels reached life threatening levels
1983: Studies suggest the fire could burn for another century
Other Hydrocarbons
CH4 (methane)
natural gas (90% is methane)
Oil
These hydrocarbons are created from ancient plankton
Microscopic animals and plants that float in water
More efficient source of energy than coal
Formation of oil and gas difficult due to environment
Accumulation and creation
Must have large quantities of material
requires high pressure and temperatures
takes millions of years
How does oil and natural gas form
Burial of organic matter…often in muds
Heat and pressure break material down to form petroleum
Due to fluid nature these substances migrate upwards to porous rocks (sandstones)
Can continue to migrate upwards unless it becomes “trapped”
How does this happen?
Traps
Coal, Natural gas/methane can be used directly from source
Oil must be distilled to be useful
What are some side affects of using hydrocarbons?
Drawbacks
Sulfur Release (pollution)
CO2 production
limited resource
What are some alternative energy sources?
Pros and Cons for each?
Nuclear Energy
How does it work?
Harness energy created by fission reactions
Fission--> split atoms and create smaller atoms--> excess mass converted to energy
reaction is controlled by water (cools)
energy produced heats other water and drives turbines creating energy
Problems?
Nuclear proliferation
Meltdowns
coolant is interrupted and excessive heat is generated
Waste products
how to dispose of them
where to dispose of them
short term vs. long term
Solar Power
Uses IR radiation and silicon
silicon is excited by IR radiation and releases electrons
creates a “flow” of energy
Problems?
Difficult to create pure enough silicon
not overly efficient (only 10-20% of radiant energy)
Hydrogen fuel cells
Uses an oxidation reduction reactions to generate energy
Oxidize Hydrogen 2H2 + 4OH- --> 4H2O + 4 e-
Reduce Oxygen O2 + H2O + 4e- --> 4OH-
Moving electrons from hydrogen side to oxygen side creates a flow of electricity
Problems?
Wind and water power
how does do they work
Best locations
Problems?
Waste to energy plants?
What are they
Biogas
Used to be:
animal waste or landfill
60% methane, 30% carbon dioxide
Some here though mostly Asia
Now:
Bio-diesel created by corn, grass etc
CO2 out = CO2 in
Problems?