we will see significant shortages by 2015 Carbon cycle Oil Petroleum and gas

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					        Energy
• Energy production and
  consumption, Agriculture and
  Chemical Manufacturing
  underlie most environmental
  issues
• freons-stratospheric O3
  depletion
• CO2-global warming
• Agricultural run off
  contaminating water ways
• Urban smog and aerosols
• PCB contamination of the
  Great Lakes in the US
• Acid rain and acid aerosols
 Energy from the earth
54.4x1020 kJoules of the sun’s energy
strikes the earths surface each year




                        Sun


       earth
                Of this ~30% is reflected
                back to into space
                (albedo)
                One Joule = 4.2 calories.
                It takes ~2000 K- calories
                to feed a human each day
                What fraction of the
                earth’s energy striking the
                earth, if turned into food,
                could feed the planet
SO what is a joule??
 Force = mass x acceleration
 f=mxa
 a = D velocity / D time = dv/dt
 velocity = D distance / D time
 a= D distance / D time2

 Work = force x distance
 W=fxd
 W= m x a x d and W = m x d2 /t2
 Work and energy have the same units
 (The First Law U2 - U1 = q - w )
 a joule is defined as accelerating 1
 kg of mass at 1 meter/sec2 for a
 distance of 1 meter
 A watt is a unit of power = 1
 joule/second or energy/time
What is the total human energy
utilization compared to the
Sun’s energy striking the earth?
 54.4x1020 kJoules of the sun’s energy
 strikes the earths surface each year
 # of kJ striking the earth/year, minus
 reflection (albedo   =0.3)= total energy
 54.4x1020 x 0.7= 38.1x1020 kJoules
 what fraction of total sun’s energy
 absorbed by the earth is used by
 human activity ?
  people use 3.7 x10 17 kJoules/year
 3.7 x10 17 / 38.1x1020 = 0.001 = 0.1%
  so if we harnessed 1/1000th of the
 sun’s energy we could supply all of our
 needs
Worldwide energy use and
how do we use fuels (1993)
        Oil           34.1%
        Coal          24.1%
        natural gas   17.4%
        Biomass       14.7%
        Hydro             5.5%
        Nuclear           4.1%

       energy use/y          Population
         (1993)
 world 382 x1018 joules      4.87x109
 Indust.
 world 347 x1018 joules          1.22x109
 Developing
 world 35 x1018 joules       3.65x109
Where are the global energy
reserves
  oil
        Figure 1.5 SpiroFormer USSR


        page 10


                       Middle East




                               Asia and
                               Australia
                               including
                               China
Where are the global energy
reserves

 Natural gas


               Former USSR




               Middle East



                         Asia and
                         Australia
                         including
                         China
Where are the global energy
reserves

 Coal


                  Former USSR



                    China




                        Australia
Earth’s nonrenewable energy
resources (1980)
              estimated stock   consumption
                                (world)/year
                     x 1021 J    x1018J
petroleum            10         135
Natural gas          10         60
coal                 250        90
oilshale             2,000      0
uranium              20         6.3
(non-breading
water reactors)
Thorium and          10,000      0
Uranium
(in breeder react)
Deuterium and Li     1010        0
in sea water for
fusion
Worldwide energy use and
how do we used fuels
how long will the oil last??
1980 estimate of reserves Oil
            1x1022 J
Where does a number like this come
from? Let’s look at a 2004 Christian
Science Monitor article:
World wide proven Oil reserves = 1.1 to
1.3 x1012 barrels
1 barrel of oil = 42 US gallons or 158.99
liters
If hydrocarbons have a density of 0.9
kg/liter
1 barrel = 158.99x 0.9x1000 grams
= 1.43x105 grams oil /barrel
= 1.43x105 grams oil /barrel

We will see later that one gram of oil
gives off 44 kJoules/g when it is
burned

We said there were 1.2x1012 barrels
known reserves

This means that we have 1.43x105 x
1.2x1012 x 44 x10000 joules of oil=

~0.8x1022 joules
WE SAID THE 1980 ESTIMATE

1x1022 joules
1x1022 joules in reserves


1980 estimate of oil usage /year
            1.35x1020 J/year


Estimate the # years of oil left if we
used at the above rate from 1980 to
1990 and 2x’s the 1980 rate after 1990
= ??
New data
WE use globally (2004)about

 30x109 barrels/year
If we have
1.2 x1012 in reserve or

1200 x 109 in reserve

Others say World wide oil reserves
have grown 15% between 1999 and
2004 and have grown by a factor of 5
since WWII
These estimates place the global
reserves at ~3x1012 barrels and
suggest that we have only used 25% of
the total oil on the planet

What we know is that major
importers are not waiting around
to see who is right!!!
The US, China, Japan are
scrambling to tie down interests
in Russia, West Africa, Iraq, Iran
and Libya
What happens to the fuel we
burn
Burning “old” carbon: fossil fuels add CO2
to the atmosphere that has been buried as
carbon under the earths surface eons
ago.
Burning “new”: biomass fuels puts CO2
in the atmosphere that has just recently
been remove from the atmosphere by
plants. These kinds of fuels would be
considered green house neutral.
Given the exponential increase in our
use of fossil fuels, one must ask, how
much longer this can go on?
Some people in the automotive industry
said in 2000 (conversation of Kamens
with D. Schuetzle of Ford) we will see
significant shortages by 2015
Carbon cycle
Oil
Petroleum and gas deposits come
from the seas.
Oceans produce 25- 50 billion tones of
reduced carbon annually.
Most is recycled to the atmosphere as
CO2. A very small fraction settles to the
bottom where oxidation is negligible
 here it is compacted with clay and
sand particles
Anaerobic bacteria digest the bacterial
digestible matter, releasing O2 and N2.
The hydrocarbons most resistant are
the hydrocarbon based lipids and these
persist and are found in their cell
membranes indicating that bacteria
process organic debris in the oceans
and over the eons turned it into oil
oil
Coal
Coal formation is land or terrestrial
based
Woody plants 200 million years ago, as
they are now, are composed of
cellulose and lignins. Bacteria can
digest the cellulose over time but
lignins are resistant
In swamps the lignins accumulate
under water and are compacted into
peat
Crustal upheavals buried the peat and
subjected it to huge pressures and
temperatuers

peat   coal over time
Coal formation




            In swamps the lignins
            accumulate under water
            and are compacted into
            peat   coal over time
Coal formation
 Fuel energy
When we burn a fuel where does the
energy reside?
Let s take hydrogen in water as an
example. If we were to react H2 with O2 to
form water, we would 1st have to break the
hydrogen bonds and the oxygen bonds
This takes energy; in the case of H2 it
takes 432 kJ/mole
 (~100,000 calories/mole) for H2 2H.
100,000 calories will supply you with
many minutes of food energy??
To break O2 to O. (O2  2O.) requires
494 kJ/mol
When when water forms, however, we
get energy back from the formation of H2O
because new bonds are formed. Which
ones??
    Fuel energy
The equation for the combination of
hydrogen and oxygen if say we were to
burn hydrogen would be
      2H2 + O2  2H2O
To break a mole of H2 bonds requires 432
We need 2 moles of H2 so this requires
864 joules
To break a mole of O2 requires
492 kJ/mol; so the total energy required to
break 2H2 and O2 apart is 1356 kJ
To form water we need to form two O-H
bonds. When one OH bond forms it
releases 460 kJ/mole
But there are two water molecules that
from = 2x 460x2= 1840 kJ/mole
So how much energy is released?
Energy from breaking other
bonds (enthalpy)

             kJ/mole
      H-H      432
      O=O      492
      O-H      460
      C-H      360
      C=O      799
      C-C      347
      C-C
      aromatic 519
      N=O      632
    Fuel energy
Let’s do the same thing for burning
methane gas; the reaction is methane +
oxygen
      CH4 + 2O2  CO2 + 2H2O
We calculated before that to form one
mole of H2O we get 920 kJ, so for two
moles we get 1840 kJ/mole; to form CO2,
which also releases energy, we need to
form two C=O bonds {O=C=O} or 2x
799kJ. This gives a total formation
energy of 1840 + 1598kJ
But for this process, we 1st have to break
 4 carbon- hydrogen bonds; why?? This
requires 410 kJ/mole/bond or 1640 kJ
The total energy release is the energy
      forming bonds - break bonds
 3438kJ – 2628kJ = 810 kJ excess
energy
Combustion energies from
different fuels (kJ)
         react. per per  per  moles
         heat mole mole gram CO2 per
         kJ     O2  fuel fuel 1000kJ
hydrogen 482   482 241     120    0
2H2+O2 2H2O
Gas       810 405 810      52    1.2
CH4 + 2O2CO2 +2H2O

Petroleum 2120 407 610 44        1.6
2 (-CH2-)+ 3O22CO2 +2H2O
Coal        4332 409 512   39    2.0
4 (-CH-)+ 5O24CO2 +2H2O

Ethanol   1257 419 1257 27       1.6
C2H5OH + 3O22CO2 +3H2O
 wood       447 447   447 15     2.2
(-CHOH-) + O2CO2 +2H2O
    A Homework problem
Assume as students, that you each use
1000 Watts of power for 12 hours each
day (lights, computers, class room air
conditioning, etc, travel).

Much of this energy in Thailand and China
is generated from coal. Assume that the
process is only 50% efficient, and if you
use 1000 Watts it really requires 2000
Watts of coal power.

 Calculate how much CO2 is going into the
atmosphere to maintain you at this level of
energy consumption for each year and put
your answer in metric tones/year CO2.
                       Hint
1 watt = 1 joule/sec

Estimate the total number of joules used
per year if you are using 2000 watts for 12
hours each day

The combustion table gives you the mole
of CO2 evolved from burring 1000 kJ of
coal.

Convert this to the total moles of CO2
given off per year for 2000 watts at 12
hours each day

Convert to metric tonnes of CO2 per year

One metic tonne equals 1000kg

				
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posted:11/4/2012
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