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Physics--World Energy Sources

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Yunji Jiang

on 24 April 2012

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Transcript of Physics--World Energy Sources

World Energy Sources
The End
Energy density provides a comparison between different types of fuels
Types of World Energy Sources
Energy Density
Growth of Power Production of Various Sources
Alvin, Andrew, Dave, Kenny, Yunji
It is defined as:
energy density = energy released from fuel (
J
) /mass of fuel consumed (
kg
)
The greater the mass of the fuel that needs to be transported, the greater the cost; thus, energy density affects the fuel choice
especially
when
transportation
is considered.
Renewable Sources
Hydroelectric
Photovoltaic
Active Solar Heaters
Wind
Biofuels
Non-renewable Sources
Coal
Oil
Natural Gas
Nuclear
Rate of Power Consumption
Growth of Energy Production in the Last 50 Years
Power consumption is conventionally measured as million tonnes of oil equivalent (Mtoe)
1 Mtoe = 4.1868 x 10^16 Ws (Watt Seconds)
Therefore, 1 Mtoe = 41868 TW
Sample Calculation:
According to a statistical review of world energy consumption provided by BP Global:
(http://www.bp.com/sectionbodycopy.do?categoryId=7500&contentId=7068481
)

Energy consumption in 1965 = 3766.9 Mtoe
Therefore, (3766.9 Mtoe)(41868) = 1.5771 x 10^8 TW
Now carrying on this same
calculation for the next four
decades and a half...
Table of Annual Power Consumption Rates From 1965 to 2010
items marked in yelllow indicate years in which momentary drops in consumption can be observed
they may represent periods in which external factors overcame regular, net consumption
e.g. a successful activist program
however, overall, the consumption is of a net increase nature
Determining the Rate of Power Production (Consumption)
the relationship is in fact, linear
using two data points on the line of best fit:
(1967, 180000000 TW) and (2011, 480000000 TW)
we determine the gradient:
(480000000 TW - 180000000 TW)/
(2011 - 1967)
= 6.8182 x 10^6 TW/a
1. Energy production has been and continues to be economically and financially viable with significant investments in research and technology over the past 50 years.
2. World population and urban sprawl has increased significantly in the past 50 years, driving up the demand and desire for increased energy production.
3. Despite efforts to reduce our reliance on non-renewable energy sources stemming from the 80s, production has increased and there has been little change to our consumption.
Millions of tonnes of oil equivalent
Megawatts
- The carbon-based fuels that we use have increased dramatically since the initial production

-Nuclear and hydroelectric power has been growing, but extremely slowly

-Although there has been a rapid increase in new energy technologies, they are relatively new

-Solar, wind, biofuels, and geothermal sources are only in the development stages
Energy production
Fuel
a substance that can release energy by changing its chemical or nuclear structure.
In other words, it is the amount of energy that can be extracted per kilogram of FUEL! Take a look:
How Does Energy Density Influence our Fuel Choices?
How do we calculate energy density?
Suppose we have a situation where water is falling from a height of 75m and is used to drive a turbine to produce electricity. Assuming that all of the gravitational energy was converted into mechanical energy, the energy density of this system would be :
9.81m⁄s^2 (75m)
Prezi isn't very nice with equations is it..
Now let's consider nuclear energy: if the energy released from a typical fission reaction involving uranium-235 is 200 MeV, what is the energy density of uranium-235?

-Remember that the units of energy density is J/kg
-One kg of uranium is 1000g/235gmol^-1, or 4.26 moles of uranium
-The number of fission reactions from each nucleus is 4.26mol(6.02 x 10^23)=2.57 x 10^24 nuclei.
-So the total amount of energy produced by 1kg of uranium 235 is:
2.57x10^24(200x10^6eV)(1.6x10^-19J/eV)
Which is approximately 8.2x10^13 J/kg
Example: burning fossil fuels- the energy density is simply the heat of combustion. This applies to anything involving combustion.
In nuclear fission reactions, mass in directly converted into energy- E=mc^2
When considering fuel choices, it is important to balance the factor of energy density with other factors like renewability, pollution, efficiency and cost.
Hydroelectricity for example is clean and renewable, but has a very low energy density compared to burning of fossil fuels.
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