Earth Science 4.2 Alternate Energy Sources Alternate Energy Sources

 Key Concepts: What are the advantages of using solar energy? How do nuclear power plants use nuclear fission to produce energy? What is wind powers potential for providing energy in the future? How do hydroelectric, geothermal, and tidal power contribute to our energy resources?

Solar Energy  Solar Energy is by far the Earth’s most abundant energy source  Every second the total energy Earth receives from the sun amounts to more than 10,000 times the total amount of energy used by all human societies in a day  Solar energy has two advantages: the fuel is free and it’s nonpolluting

Solar Energy  The simplest and most widely used solar energy systems are passive solar collectors such as south-facing windows.  As sunlight passes through the glass, objects in the room absorb the heat. These objects radiate the heat, which warms the air.

Solar Energy  More elaborate systems for home heating use an active solar collector.  These roof mounted boxes are usually large panels covered with plastic or glass. The heat they collect can be transferred by circulating air or liquids through the piping.  Solar collectors are also used to heat hot water

Solar Energy  Another type of solar collector uses photovoltaic cells that convert sunlight directly to energy that can be stored in battery systems

Nuclear Energy  Nuclear power meets about 7% of the energy demand of the United States  The fuel for plants comes from radioactive materials that release energy through nuclear fission.  In nuclear fission, the nuclei of heavy atoms such as uranium-235 are bombarded with electrons. The uranium nuclei then split into smaller nuclei and emit neutrons and heat energy.

Nuclear Energy  The neutrons that are emitted then bombard the nuclei of adjacent uranium atoms, producing a chain reaction.  If the reaction continues in an uncontrolled manner, fission releases an enormous amount of energy as an atomic explosion

Nuclear Energy  In a nuclear powerplant however, the fission material is controlled by moving neutron-absorbing rods into or out of the reactor  The result is a controlled nuclear chain reaction that releases great amounts of heat.

Nuclear Energy  At one time, energy experts thought nuclear power would be the solution to all the Earth’s energy needs.  Several issues have developed in the past few years that have slowed the development of nuclear energy  First: the cost of building safe nuclear facilities has increased.  Secondly: serious hazards are associated with the disposal and storage of nuclear waste  Third: Severe accidents in the past few decades, Three Mile Island and Chernobyl, have revealed that nuclear energy facilities have serious safety concerns.

Wind Energy  According to experts, if just the winds of North and South Dakota could be harnessed, they would provide 80% of the electrical energy used in the United States  Some experts estimate that in the next 50 to 60 years, wind power could meet 5 to 10 percent of the country’s demand for energy  Obstacles to development are technical advances, noise pollution, and cost of large tracts of land in populated areas.

Hydroelectric Power  Like wind, moving water has been around for centuries ad used as an energy source  Hydroelectric power is power generated from falling water being used to run turbines that produce electricity  The water held in a reservoir behind a dam is a form of stored energy that can be released through the dam to produce electric power

Geothermal Energy  On a commercial level, Geothermal Energy is harnessed by tapping natural underground reservoirs of steam and hot water.  Hot water is used directly for heating and to turn turbines to generate electric power  On a local level, geothermal energy can be used to reduce heating/cooling costs when it is combined with other systems such as passive or active solar systems. Water beneath the ground can be run through a house foundation to bring the foundation up to a level where less energy is used to heat the house.

Tidal Power  The development of tidal power is an area of energy exploration that is just now being explored for it’s potential to generate power  Tidal power is harnessed by building a dam across the mouth of a bay in coastal areas with a large tidal range. The strong in-out flow of the tides is used to drive turbines much like a hydroelectric dam. These turbines than generate electricity.  Tidal power isn’t economical unless the rate of water flow is enough to generate electricity at a sufficient rate. If the tides are too strong however, they will tear the tidal dams apart.

Tidal Power: Passamaquoddy Bay

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Computer Lab Project:  Create a one page report on one of the following topics Solar Energy and solar collectors Wind Energy and Wind Turbines Geothermal Energy Tidal Power: Passamaquoddy Bay Tidal Project