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NFCRC Tutorial: Energy

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Energy

Energy is defined in Webster's dictionary as "capacity for action or performing work." Any action that occurs in nature is accompanied by a reduction in the overall quality of energy while energy is neither destroyed nor created, but transformed into state(s) or form(s) with an overall lower quality or potential. (Matter may be considered as a special from of energy and should also be included in the energy conservation principle stated above when involving nuclear energy.) Higher forms of energy are harnessed by natural or human processes and are downgraded to lower forms of energy and rendered often useless, thus a continuos depletion of useful energy forms occurs in nature.

The various forms of energy include heat, light, microwaves, electricity, potential energy stored in a body held in a force field, say the gravitational field at an elevation, kinetic energy of a moving object, energy associated with the chemical bonds that hold atoms and molecules together and nuclear energy created by transforming matter into energy.

Energy Use

Energy plays an important role in our lives and its use is a direct measure of the economic well being of a society. The economic health of a country is often measured in terms of the GNP (Gross National Product). Often times, the per capita energy consumption is correlated to the per capita GNP of a country. The following table shows a comparison of the per capita energy consumption of some countries at various levels of economic development and the GNP. The correlation between energy use and per capita GNP, however, does not take into account the energy conservation measures practiced by or instituted in a given country (example, mass transportation), the climatic conditions and the type of economy, that is, whether it is dominated by a service economy, agriculture or industrial production. Note the anomalies between the U. S., Japan and Germany and between Italy and South Korea:

Energy Consumption and Per Capita1,2 and GNP3 (Multiply 106 Btu by 1.0548 to obtain Giga Joules) table energy consumption

Energy is used in almost every human activity in an industrialized society, examples being:

Thus, energy is consumed by us directly as in transportation and household uses as well as indirectly by consuming goods that require energy in their production.

Photo of traffic jam The U.S. consumes the largest amount of energy per capita on a worldwide basis. Its total annual energy consumption was 90.8 quadrillion Btu2 or 95.8x109 Giga Joules in 1995 which corresponds to a per capita annual consumption of 369 million Btu1,2 or 389 Giga Joules (a barrel of oil or 440 lb of a typical bituminous coal contains 5.6 million Btu or 5.9 Giga Joules). The use of energy in the U. S. is mostly concentrated in large metropolitan areas such as Los Angeles. A major use of energy is in automobiles due to the long distance commuting involved. The annual gasoline consumption for the Los Angeles county alone (excluding aviation) in 1995 was 3.457 billion gallons or 0.458 quadrillion Btu or 0.483x109 Giga Joules.4 Electricity and natural gas delivered to this county in 1996 were 60,498 million KWH and 3,573 million therms5,6 or 377 Giga Joules. The per capita energy consumption of electricity, natural gas and gasoline alone, with a population of 9.488 million for the county, is estimated at 108 million Btu or 114 Giga Joules. Note that this energy consumption is at the end user only and represents only a portion of the total energy required by a population. For example, it does not include the energy required for the production of the electricity by the utility or the energy present in the petroleum that goes into the production of the gasoline by the refinery which are significantly higher, nor does it include the energy required to produce the various goods or consumer items that a population consumes.

Energy Sources. Primary sources of energy are fossil fuels such as natural gas, oil, coal and to a lesser extent, nuclear by fission of radioactive elements (in France however, majority of electricity is produced by nuclear), solar in direct heating, in photovoltaic cells, rivers that provide hydroelectricity which in certain regions such as the U. S. Pacific Northwest and in Norway and Sweden is very significant (note that it is the solar energy that actually "drives" the rivers), wind for turning turbines to generate electricity, geothermal, biomass and possibly oil shale in the future.

Energy Conversion. In most current applications, the energy contained in fossil fuels and biomass as the chemical bond energy is harnessed by combustion. These combustion based sources provide as much as 90% of the current energy supply in the U.S. The combustion process, however, produces pollutants and conversion efficiency of the fuel bound energy to electricity with the intermediate step involving combustion is limited by the temperature at which the heat may be utilized. A more efficient and environmentally responsible way of converting this fuel bound energy consists of utilizing fuel cells which convert the fuel bound energy directly into electricity. Fuel cells, however require clean fuels such as natural gas. Dirty fuels such as coal and biomass may be converted to clean fuels by partial combustion or gasification followed by cleaning the gas thus derived, and then either fueling a fuel cell or a gas turbine with the clean gas.

Energy Reserves and Trends1,2. The U.S. has large reserves of coal and supplies both the domestic and the export markets. Coal was the principal source of energy in the U.S. and its use peaked in the 1930s and since then its consumption has been relatively flat with some minor peaks and valleys. Large scale production of oil mostly brought about by the advent of the automobile was responsible for the decline in the steady growth of coal usage. Nuclear energy took off in the late 1950s to early 1960s but its usage flattened off in the 1960s to 1970s with only 10% of the total U.S. energy demand being met by it. In contrast, France meets essentially all its energy demands for generating electricity by Nuclear. Natural gas usage took of in the U.S. in the 1920s and provides a clean burning energy source compared to the other fossil fuels. Finally, solar energy whose use was encouraged in the late 1970s by President Carter never really took off, the monetary incentives for encouraging its use and the research grants were not given the necessary support by subsequent administrations.

Energy use over the next two decades is expected to increase significantly throughout the world, with highest growth rates in Asia. By the year 2015 world energy demand is projected to be around 562 quadrillion Btu or 593x109 Giga Joules. This growth represents more than a 50% increase over the consumption in 1995. Two-thirds of this increase in energy consumption is expected to be due to the developing countries concentrated mostly in Asia where energy growth is projected to be on an average of 4.2% annually, while for industrialized economies it is projected to be 1.3%.

Other than nuclear power, all sources of energy are projected to grow: Oil use is expected to exceed 100 million barrels per day by 2015 which is a growth of 50% over 1995. Coal use is projected to be in excess of 7.3 billion ST or 6.6 billion MT or Mega Grams by 2015 on a world wide basis, compared to 5.1 billion ST or 4.6 billion MT or Mega Grams in 1995. Natural gas usage is expected to increase at 3.1% annually and by 2015 and is projected to be the principal fossil fuel for the world.

Due to these tremendous increases in fossil fuel usage world wide, the carbon emissions to the atmosphere are expected to increase by about 60% by 2015 over the 1990 level.

Energy Use and the Environment. A conflict, thus arises between use of energy and the environment, this conflict brought about for the first time in the life of our planet, in the 20th century by the large scale usage of energy. The harnessing of the energy contained within a fuel by combustion produces pollutants such as oxides of sulfur, oxides of nitrogen and unburned hydrocarbons which are introduced into the atmosphere, the amount depending on the degree of pollution abatement measures incorporated. All fossil fuels also introduce the greenhouse gas carbon dioxide into the atmosphere while nuclear energy produces radioactive waste. In the past, the governing laws for engineering design in the industry had been the application of mass, momentum and energy equations but in the future the environmental impact will be included more and more as one of the laws in the design work.

The importance of minimizing the adverse effects on the environment or what is emitted to the atmosphere may be appreciated by realizing that the earth's surface is covered by a precious layer of air that is only 10 miles or 16 kilo meters in thickness (the troposphere) which is quite thin when compared to the earth's diameter of 8000 miles or 12,800 kilo meters.

Quiz

1. Which of the following energy conversions produces the least amount of pollution?
a) Fossil Fuels
b) Fuel Cells
c) Coal
d) Biomass


2. Which of these produce energy?
a) hot water
b) automobile
c) wind
d) all the above


3. Which country or countries consumes the largest amount of energy per capita?
a) Japan
b) United States
c) Russia
d) Germany
e) The entire continent of Africa


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References:

1.World Energy Consumption at Web Site
2.United States Energy Information Administration
3.California Energy Commission

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