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Alternative Fuel Sources





Nuclear Energy      
 
(Chernobyl Nuclear Power Plant, former USSR;  http://www.chernobyl.co.uk/)

Nuclear energy provides 7.6% of the US energy needs.  The primary sources that are used to produce a nuclear reaction are Uranium-235 and Plutonium-239.  Nuclear energy is generated by the splitting of the nucleus of an atom, called nuclear fission.  When the nucleus divides energy is released in the form of heat and light.  Nuclear fission provides a vast amount of energy, that when released slowly, can be harnessed to produce electricity.  The fission of an atom of uranium liberates about 10 million times as much energy as the combustion of an atom of carbon from coal. 


Disadvantages:

Some of the disadvantages to nuclear power plants are that they are relatively expensive to construct and maintain, they produce hazardous nuclear waste, and there is the potential for enormous nuclear disasters.  The waste produced from a nuclear reaction is highly toxic and can not be recycled.  It has to be stored in a secured location where it will not effect the environment.  The largest concern about nuclear energy, however, is the possibility of a nuclear disaster.  One such disaster occurred at the Chernobyl nuclear power plant in the former USSR.

On April 26th, 1986, the Chernobyl nuclear power plant's number four reactor exploded, sending a radioactive cloud across much of Europe. Following the explosion, radioactivity with an intensity equivalent to 500 of the bombs that destroyed Hiroshima at the end of World War II was measured in the atmosphere. According to unofficial statistics, at least 15,000 people have died as a direct result of the explosion. The power station is still seen by critics as a time bomb, and work has been carried out ever since to try and make the site safe.


Hydroelectric Energy

(Ice Harbor Dam, Snake River, Washington;  http://www.eia.doe.gov/fuelrenewable.html)

Hydroelectric energy provides roughly 3.8% of the US energy needs.  It is currently the largest source of renewable energy.  Hydroelectric energy is a very efficient source of energy and does not release any greenhouse gases.  Electricity is generated by water flowing downhill and turning the blades of turbines.  The three types of hydroelectric energy generators are impoundment, diversion, and pumped storage.  An impoundment generator is when a dam is built to contain and direct the flow of water to spin the turbines.  A diversion hydroelectric energy generator is when a channel is constructed to divert part of a river to flow downhill through a turbine.  Pumped storage generators actually pump water back uphill so that it can be stored as potential energy to be used later.

Disadvantages:

In order to harness this large source of energy, dams and turbines must be constructed.  The construction of dams floods the area of land upstream, thus greatly altering the surrounding ecosystem. 

Biomass Energy


(A common landfill;  http://www.eia.doe.gov/cneaf/solar.renewables/page/mswaste/msw.html)


Biomass energy provides 3.2% of the energy used by the US.  Biomass energy is organic matter, many of which are waste products, that are used as fuel sources.  There are many different types of sources of biomass energy that can be used such as:  wood, plants, residue from agriculture or forestry, and the organic component of municipal and industrial wastes.  Many biomass energy sources can be converted directly into liquid fuels for our transportation needs.  Today, wood is still are largest biomass energy resource.

Table B6. Average Heat Content of Selected Biomass Fuels
Fuel Type
Heat Content
Units
Agricultural Byproducts 8.248  Million Btu/Short Ton
Black Liquor 11.758  Million Btu/Short Ton
Digester Gas 0.619  Million Btu/Thousand Cubic Feet
Landfill Gas 0.490  Million Btu/Thousand Cubic Feet
Methane 0.841  Million Btu/Thousand Cubic Feet
Municipal Solid Waste 9.945  Million Btu/Short Ton
Paper Pellets 13.029  Million Btu/Short Ton
Peat 8.000  Million Btu/Short Ton
Railroad Ties 12.618  Million Btu/Short Ton
Sludge Waste 7.512  Million Btu/Short Ton
Sludge Wood 10.071  Million Btu/Short Ton
Solid Byproducts 25.830  Million Btu/Short Ton
Spent Sulfite Liquor 12.720  Million Btu/Short Ton
Tires 26.865  Million Btu/Short Ton
Utility Poles 12.500  Million Btu/Short Ton
Waste Alcohol 3.800  Million Btu/Barrel
Wood/Wood Waste 9.961  Million Btu/Short Ton
   Source: Energy Information Administration, Form EIA-860B (1999), "Annual Electric Generator Report - Nonutility 1999."

Disadvantages:

Biomass energy is not the cleanest source of energy.  Most biomass sources are waste products that are not used, many of which produce a considerable amount of greenhouse gases.

Geothermal Energy

(Geothermal energy pumps;  http://www.eia.doe.gov/cneaf/solar.renewables/page/heatpumps/heatpumps.html)
Geothermal energy provides 0.3% of the total energy sources used by the US.  It costs roughly 4-8 cents per kilowatt-hour and creates very little harmful air emissions.  Geothermal energy is energy derived from the natural heat of the Earth.  The earth's temperature varies widely, and geothermal energy is usable for a wide range of temperatures from room temperature to well over 300° F.  Electricity is produced by pumping water into the ground where it is converted to steam using the natural heat of the Earth.  The steam is then used to spin a turbine which produces electricity.  Several different systems have been created to maximize efficiency and to fit the varying geothermal energy locations.  Three of which are displayed below.

       
(http://www.nrel.gov/geothermal/geoelectricity.html)
Disadvantages:

Geothermal energy can only be used in areas where reservoirs are found in geothermal systems, which are regionally localized geologic settings, where the Earth's naturally occurring heat flow is near enough to the Earth’s surface to bring steam or hot water to the surface.  Thus, geothermal energy can not meet every energy need.  Also, geothermal energy produces only a small amount of electricity compared to other alternative fuel sources.

Solar Energy

(http://www.eia.doe.gov/cneaf/solar.renewables/page/solarthermal/solarthermal.html)

Solar energy provides for 0.07% of the US energy needs.  Photovoltaic devices use semiconducting materials to convert sunlight directly into electricity.  When sunlight is absorbed by these materials, the solar energy knocks electrons loose from their atoms, allowing the electrons to flow through the material to produce electricity.  Sunlight is an almost endless source of energy and is relatively cheap.  The Earth receives 1370 watts/m² of sunlight.  Solar energy is commonly used to generate electricity, or heat homes and pools.

Disadvantages:

The main disadvantage of solar energy is its limited time of use.  It is not an efficient energy source at night or during overcast days.  The amount of electricity produced by solar energy depends on the amount of light emitted by the sun.  If the light emissions are obstructed from reaching the photovoltaic receptors, no electricity is generated.  Also, solar energy is seasonally dependent.  More sunlight reaches the Earth during the summer months then the winter months because of longer daylight.  So solar energy is not as efficient during the winter.


Wind Energy

(http://www.eia.doe.gov/cneaf/solar.renewables/page/wind/wind.html)
    Wind energy provides only 0.04% of the total energy usage of the US.  •Winds are created by the uneven heating of the atmosphere by the sun, irregularities of the Earth's surface, and the rotation of the Earth.  Wind energy provides one of the cheapest available sources of energy with a cost of only about 4-6 cents per kilowatt-hour.  Wind energy is harnessed and converted to electricity by three bladed wind turbines.  The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity.

Disadvantages:

The main disadvantage of wind energy is that good wind sites are in remote locations.  These sites are often situated miles away from the citys that could use the electricity.  Long stretches of power lines are needed to connect each city to the wind energy generators.