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U4735x Environmental Science for Decision Makers
Lectures 9, 10,and 11: Energy and Public Policy.
Walter Pitman
Many of the slides for this lecture are published in the following documents:
BP Statistical Review of World Energy (pdf, 2.2MB).
Appendices: Conversion Factors and Definitions (pdf, 36KB)
Energy in its various forms (i.e. heat, chemical, radiant) represents the ability to perform work, and is thus expressed in units of work.
Work is defined as a force applied over some distance.
In the metric system, units of energy are the joule and the erg.
1 joule = energy required when 1 newton of force acts through 1 meter. (One newton is the force that accelerated a 1-kilogram mass by 1 meter per second per second.)
1 erg = energy required when 1 dyne acts through 1 centimeter. (One dyne is the force that accelerates a 1-gram mass by 1 centimeter per second per second.)
1 joule = 10 ergs
4.186 joules = 1 calories of heat
Power is the rate at which energy is used, that is, released or converted from one form to another. The unit of power is the watt.
1 watt = 1 joule per second
1 kilowatt = 1000 joules per second
1 megawatt = 1000 kilowatts
When solar radiation is absorbed by air, water, land, etc., radiant energy is converted to heat energy. The resulting amount of heat can be described in terms of calories or joules.
The rate at which solar radiation travels through some cross-sectional area, or the rate at which it is absorbed by some surface, is called flux. The flux of energy may be described in terms of watts per square meter, joules per square meter per minute, or calories per square centimeter per minute.
The world uses primary energy at a rate of about 12,000,000,000,000 Watts or 12.0 Terrawatts or 2000 Watts per person, 24 hours a day, each day, etc...
About 87% of this is obtained from hydro-carbons:
primary energy: oil, gas, coal, nuclear, hydro.
hydrocarbons: oil, gas, and coal.
or 1800 Watts per person, 24 hours a day, each day, etc...
Most of the energy we obtain from fossil fuels is obtained by burning them.
Of this, much is absorbed in the ocean and elsewhere but a net of about 10 x 109 tonnes is added to the atmosphere.
The reserves of oil and gas are particularly perilous.
We will speak of Proven Reserves which 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 operating conditions.
We will also speak of R/P ratio (Reserves/Production). If the reserves remaining at the end of any year are divided by the production in that year, the result is the length of time that those remaining reserves would last if production were to continue at that level.
At the present rate,of usage, the known proven reserves of oil, gas, and coal, combined in an energy package, would last 111 years.
This is an oversimplified and optimistic view, since much energy is lost in converting from one type of energy to another. For example, oil burning electrical generators operate at about 33% efficiency, i.e. you only get out (as electrical energy) 1/3 of the energy you put in.
Oil.
The Persian Gulf nations have ~65.4% of the proven oil reserves. OPEC nations have 79%.
37% of the oil the world uses comes from OPEC.
29% of the total oil the U.S. uses comes from OPEC.
20% of U.S. oil imports come from the Persian Gulf countries.
Gas.
The Persian Gulf States have 36% of the proven natural gas reserves.
The former Soviet Union has 39.2% of the proven gas reserves.
Persian Gulf consumes what it produces, which is small.
Charts of natural gas production by area and natural gas R/P ratios.
1 tonne of oil ~ 1.5 tonnes hard coal: anthricite and bituminous.
1 tonne of oil ~ 3.0 tonnes soft coal: sub-bituminous and lignite.
World Reserves Hard Coal Soft Coal
(tonnes oil equiv)26% North America 120,222 x 106 tonnes 137,561 x 106 29.7% Asia Pacific 189,347 x 106 tonnes 103,124 x 106 36% EUR & Eurasia. 144,874 x 106 tonnes 210,496 x 106 World Reserves tonnes oil equiv 501,062 x 106
Proven Reserves: 1047.7 x 109 bbls.
at 7.33 bbl/tonne = 142.9 x 109 tonnes.
Proven Reserves: 155.78 x 1012 m3.
one billion cubic meters = 0.9 million tonnes oil equivalent.
So, proven reserves = 140.22 x 109 tonnes oil equivalent.
World total annual use of oil, gas, coal: 8.202 x 109 tonnes oil equivalent.
At the present rate of usage, the proven reserves will last 97.8 years.
Charts of World energy consumption and Regional consumption pattern 2000.
The total mass of all land plants is about 1800x109 tonnes.
9/10 of this is in the world's forests.
Land plants are estimated to recycle about 400x109 tonnes of CO2 per year.
The oceans also contain a large amount of CO2 which is constantly being released and reabsorbed - recycling about the same as land plants.
In addition, about 20-24x109 tonnes of CO2 is released into the atmosphere each year by the burning of fossil fuels.
Deforestation removes about 200,000 km2 per year reducing the potential net takeup of CO2 by 10x109 tonnes per year.
So the effective potential addition of CO2 to the atmosphere is 30-34x109 tonnes of CO2/year.
It is estimated that 1/3 is absorbed by the oceans and about 1/3 is added to the atmosphere.
The fate of the remaining 1/3 is a mystery.
The recycling of CO2 by animals is considered to be negligible.
The CO2 concentration in the atmosphere before human interference was about 270 ppm by volume.
It is now increasing at about 1.5ppm/year.
Updated September 30, 2003
