Energy Density



The higher the energy density of in fuel, the more the energy can be transported or stored in the same amount of mass. Energy density in fuel in context can also be called the specific energy of fuel. In general, however, engines that uses a fuel with high energy density will yield less energy due to inefficiency and thermodynamic aspects. So the fuel consumption of the engine is much greater.(Wikipedia)

Therefore the choice in using a higher density and lower energy density is due to the the needed use of energy consumption. For example, because kerosene has a relatively high energy density (46.3MJ/kg), it is commonly used as jet fuel. Additionally, because kerosene has a high energy density, it is able to effectively power our other uses of energy including kerosene heaters, lamps stoves and lanterns (End Times Report).

For the human body, fats are energy sources with a relatively high energy density as well (38.9MJ/kg). Therefore, this is why fats are common intakes into the digestive system and provide as energy stores for the human body (Wikipedia). Saturated fats (the "bad" fats) tend to give off more energy compared to unsaturated fats (the "good fats") for a given number of carbon atoms (Wikipedia). However, excessive levels of saturated fats are harmful for the human body and can cause problems such as heart diseases.

Energy Densities of Some Fuels:
Storage Type
Energy Density By Mass (MJ/kg)

Simple Compounds

Hydrogen
142
Methane
55.5
Methanol
22.7
Ethanol
29.7

Fossil Fuels

Coal, anthracite
31.4
Diesel
45.3
Gasoline, automotive
45.8
Gasoline, aviation
43.1
Kerosene
46.3
Oil, crude(petroleum)
41.9
Oil, heating
42.5

Foods

Carbohydrates
17.2
Fats
38.9
Proteins
17.2

Biomass Fuels

Charcoal
29.0
Cotton Husk
16.0
Dung, air dry
12.0
Peat
14.6
Rice Straw
15.2
Wood, green
10.9
Wood, air dry
15.5
Wood, oven dry
20.0
Sugar Cane
19.0
Source: Hypertexbook.com


Fuel Use Proportions


85% OF ALL ENERGY IN THE WORLD COMES FROM FOSSIL FUELS
-OIL MAKES UP 45% OF THIS

-COAL MAKES UP 62% OF THIS IN 1950, IN 1998 DROPPED TO 28%
BPStatReview2007WorldConsumptionEnergy.gif

Advantages and Disadvantages of various energy sources




Source
Advantages
Disadvantages
Coal
  • Inexpensive
  • Easy to recover
  • One of the most abundant energy sources
  • Versatile; can be burned directly, transformed into liquid, gas, or feedstock
  • Inexpensive compared to other energy sources
  • Good for recreational use (charcoal for barbequing, drawing)
  • Can be used to produce ultra-clean fuel
  • Can lower overall amount of greenhouse gases (liquification or gasification)
  • Leading source of electricity today
  • Reduces dependence on foreign oil
  • By-product of burning (ash) can be used for concrete and roadways

  • Source of pollution: emits waste, SO2 , Nitrogen Oxide, ash
  • Coal mining mars the landscape
  • Liquification, gasification require large amounts of water
  • Physical transport is difficult
  • Technology to process to liquid or gas is not fully developed
  • Solid is more difficult to burn than liquid or gases
  • Not renewable in this millennium
  • High water content reduces heating value
  • Dirty industry—leads to health problems
  • Dirty coal creates more pollution and emissions
  • Requires expensive air pollution controls (e.g. mercury, sulfur dioxide)
  • Significant contributor to acid rain and global warming
  • Requires extensive transportation system
Nuclear
  • Fuel is inexpensive
  • Energy generation is the most concentrated source
  • Waste is more compact than any other source
  • Extensive scientific basis for the cycle
  • Easy to transport as new fuel
  • No greenhouse or acid rain effects
  • Requires larger capital cost because of emergency, containment, radioactive waste and storage systems
  • Requires resolution of the long-term high level waste storage issue in most countries
  • Potential nuclear proliferation issue



Natural Gas / Oil
  • Good distribution system for current use levels
  • Easy to obtain
  • Better as space heating energy source
  • Burns clean compared to cola, oil (less polluting)
  • 70% less carbon dioxide compared to other fossil fuels
  • helps improve quality of air and water (not a pollutant)
  • does not produce ashes after energy release
  • has high heating value of 24,000 Btu per pound
  • inexpensive compared to coal
  • no odor until added

  • not a renewable source
  • finite resource trapped in the earth (some experts disagree)
  • inability to recover all in-place gas from a producible deposit because of unfavorable economics and lack of technology (It costs more to recover the remaining natural gas because of flow, access, etc.)
  • Very limited availability as shown by shortages during winters several years ago
  • Could be major contributor to global warming
  • Expensive for energy generation
  • Large price swings with supply and demand

Wind
  • Continuous sources of energy
  • Clean source of energy
  • No emissions into the atmosphere
  • Does not add to thermal burden of the earth
  • Produces no health-damaging air pollution or acid rain
  • Land can be sued to produce energy and grow crops simultaneously
  • Economical
  • Benefits local communities (jobs, revenue)
  • Wind is free if available
  • Good source for periodic water pumping demands of farms as used earlier in 1900's
  • Generation and maintenance costs have decreased. Wind is proving to be a reasonable cost renewable source.
  • Well suited to rural areas.
  • Need 3x the amount of installed generation to meet demand
  • Limited to windy areas.
  • Limited to small generator size; need many towers.
  • Need expensive energy storage (e.g. batteries)
  • Highly climate dependent - wind can damage equipment during windstorms or not turn during still summer days.
  • Can affect endangered birds, however tower design can reduce impact.
  • For most locations, wind power density is low
  • Wind velocity must be greater than 7 mph to be usable in most areas
  • Problem exists in variation of power density and duration (not reliable)
  • Need better ways to store energy
  • Land consumption

Solar
  • Sunlight is free when available
  • No pollution
  • Often an excellent supplement to other renewable sources
  • Versatile--is used for powering items as diverse as solar cars and satellites

  • Limited to sunny areas throughout the world (demand can be highest when least available, e.g winter solar heating)
  • Does require special materials for mirrors/panels that can affect environment
  • Current technology requires large amounts of land for small amounts of energy generation
Biomass
  • Could create jobs because smaller plants would be used
  • Theoretically inexhaustible fuel source
  • When direct combustion of plant mass is not used to generate energy (i.e. fermentation, pyrolysis, etc. are used instead), there is minimal environmental impact
  • Alcohols and other fuels produced by biomass are efficient, viable, and relatively clean-burning
  • Available throughout the world

  • Inefficient if small plants are used
  • Could contribute a great deal to global warming and particulate pollution if directly burned
  • Still an expensive source, both in terms of producing the biomass and converting it to alcohols
  • On a small scale there is most likely a net loss of energy--energy must be put in to grow the plant mass




Hydrogen

* The must abundant element in the universe is Hydrogen
  • Combines easily with oxygen to produce water and energy

  • Very costly to produce
  • Takes more energy to produce hydrogen then energy that could be recovered.
Nuclear Energy
  • Clear power with no atmospheric emissions
  • Useful source of energy
  • Fuel can be recycled
  • Low cost power for today’s consumption
  • Viable form of energy in countries that do not have access to other forms of fuel
  • Hydrogen and tritium could be used as fuel source
  • Higher energy output per unit mass than most other energy sources

  • Potential of high risk disaster (Chernobyl)
  • Waste produced with nowhere to put it
  • Waste produced from nuclear weapons not in use
  • Earthquakes can cause damage and leaks at plants
  • Contamination of the environment (long term)
  • Useful lifetime of a nuclear power plant
  • Plant construction is highly politicized




Bibliography:
-ADVANTAGES AND DISADVANTAGES OF ENERGY SOURCES:
http://www.spsu.edu/tmgt/vasa-sideris/MGNT4125/ADVANTAGES_AND_DISADVANTAGES_OF_ENERGY_SOURCES.htm

-BP Statistical Review of World Energy
-Comparisons of various energy sources. December 14, 2005.
<http://www.nucleartourist.com/basics/why.htm>

-Elert, Glenn. "Chemical Potential Energy." Hypertextbook.com. 2008. The Physics Hypertextbook. 02 Apr. 2009
http://hypertextbook.com/physics/matter/energy-chemical/.

-"Energy density -." Wikipedia, the free encyclopedia. 30 Mar. 2009. Wikimedia Foundation, Inc. 02 Apr. 2009
<http://en.wikipedia.org/wiki/Energy_density>.

-"Fat." Wikipedia, the free encyclopedia. 31 Mar. 2009. Wikimedia Foundation, Inc. 02 Apr. 2009
<http://en.wikipedia.org/wiki/Fat.>

-"Kerosene Fuel Primer." End Times Report - Home Page. 02 Apr. 2009
http://www.endtimesreport.com/kerosene_fuel_primer.html.
- Renewable Energy (Wikipedia)
<http://en.wikipedia.org/wii/Renewable_energy>











Authored by: Victor Gunawan, Chakrit Prasatwattana, Siddharth Sundarajan, Bob Scholten