Energy Notes

BHS Environmental Science

Mr. Walker

Electricity: Energy on Demand

• People use electric energy to power their homes and devices.
• Electricity is the flow of electrons, which are tiny charged particles that whirl around the nucleus of an atom. To generate electricity you have to set electrons in motion.
• One way to do this is to move an electrically conductive material such as copper wire through a magnetic field.
• Most power plants use fossil fuels to make energy.

Fossil Fuels:

• Fossil Fuels: coal, oil, and natural gas are the remains of organisms that lived millions of years ago. Fossil fuels are rich in carbon compounds, which contain a lot of stored energy in their molecular bonds. Burning the fossil fuels release this energy in the form of heat, which provides the energy to produce electricity.
• Electric Generator: A device for converting mechanical energy into electricity.

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Dwindling Supplies of Fossil Fuels

• Fossil Fuel supplies are limited and we are using these resources much faster than they can be replaced by nature.
• Much of Earth’s oil may be used up in your lifetime.
• Only one fossil fuel-coal-exists in relative abundance.
• The environment is threatened by exhaust from power plants and motor vehicles, by oil spills, and by strip mining for coal. Large amounts of carbon dioxide released when fossil fuel are burned could have world wide impacts by changing the earths climate.

Renewable and Nonrenewable Energy Resources

• Renewable resources are those that are continually produced. They include wind, sunlight, water etc. They are so abundant that they are considered to be inexhaustible.
• Nonrenewable resources are resources which can be used up and are in a finite amount.
• They take millions of years to make more of the resource. Examples include coal, oil, and gasoline.

Nuclear Energy

• -Nuclear Energy: The energy that exists within the nucleus of an atom
• -Nuclear Fission: When subatomic bonds are broken apart huge amounts of energy are released.
• -Nuclear Fusion: This occurs when lightweight atomic nuclei combine to form a heavier nucleus, releasing huge amounts of energy in the process. It is basically the opposite of nuclear fission. Nuclear fusion is the process that powers the stars, including our sun.

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Example of Fission

• An example of fission is the explosion of an atomic bomb. Neutrons from a Uranium-235 nucleus are split or fission. These neutrons then cause other atoms to undergo nuclear fission in a process called a chain reaction. This chain reaction releases a lot of nuclear energy which is released as heat.
• Nuclear Power plants also use Fission to produce electricity.
• Heat is used to boil water at very high temperatures, creating high pressure steam that can be used to drive an electric generator.

How a nuclear power plant works:

• 1. Energy is released by the nuclear reaction heats water in the pressurized primary circuit to a very high temperature.
• 2. The superheated water is pumped to a heat exchanger, which transfers the heat of the primary circuit to the secondary circuit.
• 3. Water in the secondary circuit flashes into high-pressure steam
• 4. Steam is directed against a turbine, setting it in motion.
• 5. The turbine sets the generator in motion, generating electricity.

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Advantages of Nuclear Energy

• Nuclear materials have a lot of energy which can be used.
• Well designed reactors can run for years without having to be refueled or shut down for anything other than minor maintenance.
• Nuclear energy does not produce gases such as carbon dioxide.

Disadvantages of Nuclear Power plants

• It produces radioactive waste. No US facility is ready for the permanent disposal of its nuclear waste. Each powerplant has its own temporary storage facilities.
• Nuclear fuel is in relatively short supply (100-200 year supply)
• Nuclear energy is very expensive. Powerplants are large and complex.
• Safety issues. If the reaction gets out of control, the enormous heat it generates may destroy the reactor building and spew the radioactive products into the air.
• Chernobyl 1986
• Ural Mountains 1957
• Three mile island USA 1979

Nuclear Fusion

• -Nuclear Fusion: This occurs when lightweight atomic nuclei combine to form a heavier nucleus, releasing huge amounts of energy in the process.
• It is basically the opposite of nuclear fission. Nuclear fusion is the process that powers the stars, including our sun.
• For Fusion to occur, the atomic nuclei must be heated to extremely high temperatures (100,000,000 Celcius) and be maintained at very high concentrations, and be properly confined. Maintaining the high temperature, high concentration, and properly confining this reaction is extremely difficult and may take decades to do or may never happen.

Conserving Energy

• Americans use twice the electricity as Europeans.
• Conservation means using materials, resources, and energy wisely.
• Methods for conserving energy:
• Turning down our home thermostat in the winter and putting on a sweater.
• Using a fan rather than an air conditioner.
• Walking or biking instead of driving a car.
• Using a high efficiency car and appliances.

Energy for the Future: Solar Energy

• Solar Energy is energy from the sun.
• Passive Solar Energy: Sunlight is used to heat buildings directly without pumps or fans. Homes have energy efficient windows that face south so that the house absorbs as much heat as possible from the sun.
• Solar water heating: Makes use of solar collectors to capture the sun’s energy. Water or antifreeze mixtures absorb the sun’s energy as it flows through the solar collectors.
• The hot liquid is then pumped through a heat exchanger, where it heats water for the home or building. The liquid forms a closed loop that efficiently transfers the suns energy to the water we use for bathing, washing dishes and even swimming.
• Solar Cells: Also called Photovoltaics, they are devices that convert the sun’s energy directly into electricity. Sunlight falls on a solar panel causing it to release electrons. The electrons flow through a circuit that is completed when another semiconductor in the solar cell absorbs electrons and passes them on to the first cell.

Energy for the Future: Wind Energy

• Wind is an indirect form of solar energy. The sun heats the surface of the earth unevenly putting the atmosphere into turbulent motion. Tremendous energy is contained in the wind.
• This energy can be captured with a turbine that is connected to an electric generator. A windmill is an example of a device that captures the energy of wind.
• The biggest disadvantage of wind energy is that few regions have winds strong or consistent enough to make wind generators economical. The blades of wind turbines can interfere with microwave communications such as radar.

Energy for the Future: Hydroelectricity

• Today water is used to generate electricity. Water must fall a considerable distance to push a heavy turbine and a generator. Dams provide this distance.
• Water has many advantages. It is clean and renewable and leaves no waste. The reservoirs that form behind the dams offer recreational activities and provide drinking water. The dams also control flooding.
• Disadvantages include a disruption to the river ecosystem and the cost of Dam construction is high. Also, electricity from hydroelectricity is an option limited to areas that have rivers and streams.

Energy for the Future: Geothermal Energy

• The interior of the Earth is a very hot place. In some places, the heat lies very close to the surface. Such places are sources of geothermal energy-the heat inside the earth. This heat can be used to drive electric generators, similar to the way in which fossil fuels and nuclear energy drive electric generators. One method is called the hot dry rock method.
• Two holes a short distance apart are drilled into a hot rock deposit
• Water is pumped down one hole at high pressure, fracturing the rock
• Heated by the rock, water returns to the surface through the second hole as high pressure steam. The steam is routed to a turbine, which turns a generator.
• The major problem is that Earth processes replace the heat very slowly. Some locations use up the available geothermal energy very quickly. Another disadvantage is that geothermal energy can be tapped in only a few places, so its availability is limited.

Energy for the Future: Biomass

• Biomass is the organic matter in plants or plant products. Biomass is an important source of energy worldwide, especially in the form of wood. Much of the world, wood is the major source of energy. In the US, the use of wood for heating homes has increased as people have tried to conserve fossil fuels. Burning biomass for fuel, however, has the disadvantage of producing carbon dioxide and noxious smoke.
• Waste to Energy: A lot of Biomass exists as waste material. Paper and pulp industry generates more than half of the energy it uses from its own waste products. The Hawaiian sugar industry burns sugar cane to generate electricity.

Energy for the Future: Liquid Fuels from Biomass

• Liquid fuels can be derived from certain types of biomass. For example, methanol, a type of alcohol, can be derived from wood.
• Ethanol, another type of alcohol, can be derived from corn, fruit, or agricultural waste.
• Cars and trucks can run quite well on either methanol or ethanol with little modification.
• An advantage is that Alcohol products are cleaner burning than gasoline or diesel fuels

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