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

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

Sun

earth

54.4x1020 kJoules of the sun’s energy strikes the earths surface each year

Energy from the earth

SO what is a joule??Force = mass x acceleration

f = m x a

a = velocity / time = dv/dt

velocity = distance / time

a= distance / time2

Work = force x distance

W = f x d

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

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

What is the total human energy utilization compared to the Sun’s energy striking the earth?

Worldwide energy use and how do we use fuels 1993 2003

Oil 34.1% (44%)

Coal 24.1% (25%)

natural gas 17.4% (26%)

Biomass 14.7% (0.2%)

Hydro 5.5% (2.4%)

Nuclear 4.1% (2.2%)

energy use/y Population (1993)

world 382 x1018 joules 4.87x109

Indust.world 347 x1018 joules 1.22x109

Developingworld 35 x1018 joules 3.65x109

Where are the global energy reserves

Figure 1.5 Spiro

page 10

oil

Middle East

Asia and Australia including China

Former USSR

0200

400600800

1000

12001400

1978 1988 1998 2008

109 b

arre

ls

world

US

Fraction of US oil reserves compared to the global total (British petroleum web site, 2007)

BP 2007 OIL RESERVES IN BILLIONS OF BARRELS

Saudi Arabia 264.2

Iran 138.4

Iraq 115.0

Kuwait 101.5

United Arab Emirates 97.8

Venezuela 87.0

Russian Federation 79.4

Kazakhstan 39.8

US 29.4

Canada 27.7

Total 980.3GLOBAL TOTAL 1237.9

Where are the global energy reserves

Natural gas

Middle East

Asia and Australia including China

Former USSR

Where are the global energy reserves

Coal

China

Australia

Former USSR

                                              

       

http://www.theglobaleducationproject.org/earth/energy-supply.php

Earth’s nonrenewable energy resources (1980) estimated stock consumption

(world)/yearx 1021 J x1018J

petroleum 10 135

Natural gas 10 60

coal 250 90

oilshale 2,000 0

uranium 20 6.3(non-breadingwater reactors)

Thorium and 10,000 0Uranium(in breeder react)

Deuterium and Li 1010 0in sea water forfusion

how long will the oil last??1980 estimate of reserves Oil

1x1022 J

Proved reserves of oil are generally taken to be those quantities that geological and engineering information indicates with reasonable certainty can be recovered in the future from known reservoirs under existing economic and geological conditions.

Where does a number like this come from?

how long will the oil last??Let’s look at a 2004 Christian Science Monitor article:

World wide proven Oil reserves = 1.1 to 1.3 x1012 barrels

BP 2007 estimate was 1238 billion barrels

= 1.24 x1012

1 barrel of oil = 42 US gallons or 159 liters

If hydrocarbons have a density of 0.9 kg/liter

1 barrel = 159 x 0.9 x 1000 grams

= 1.43x105 grams oil /barrel

= 1.43x105 grams oil /barrel

We will see later that one gram of oilgives off 44 kJoules/g when it isburned

We said there were 1.2x1012 barrelsknown reserves

This means that we have 1.43x105 x 1.24x1012 x 44 x1000 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 = ??

Newer 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 burnBurning “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 tons 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 temperatures

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.) requires494 kJ/mol

When when water forms, however, we get energy back from the formation of H2O because new bonds are formed. Which ones??

Fuel energyThe 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 kJ/mole

We need 2 moles of H2 so this requires 864 k joules/mole

To break a mole of O2 requires492 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/moleH-H 432

O=O 492

O-H 460

C-H 360

C=O 799

C-C 347

C-Caromatic 519

N=O 632

Fuel energyLet’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 molesheat mole mole gram CO2 perkJ O2 fuel fuel 1000kJ

hydrogen 482 482 241 120 02H2+O2 2H2O

Gas 810 405 810 52 1.2CH4 + 2O2CO2 +2H2O

Petroleum 2120 407 610 44 1.6 2 (-CH2-)+ 3O22CO2 +2H2O

Coal 4332 409 512 39 2.04 (-CH-)+ 5O24CO2 +2H2O

Ethanol 1257 419 1257 27 1.6 C2H5OH + 3O22CO2 +3H2O

wood 447 447 447 15 2.2(-CHOH-) + O2CO2 +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 tonnes/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

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.