1. Chapter 25
Energy Sources

2. 25-1 Fossil Fuels
Petroleum or crude oil, is a liquid source of energy made from the remains of plants and animals. It along with natural gas, and coal are called fossil fuels. When plants and animals died, they were covered with layers of sand, mud and volcanic ash. Heat, pressure and bacteria acted on these buried organisms turning them into fossil fuels.

3. 25-1 Fractional Distillation
Plants and animals contain large amounts of hydrogen and carbon, therefore, petroleum is made mostly of these elements. The compounds are called hydrocarbons.
There are different hydrocarbon compounds and they must be separated in order to use the chemical energy stored in petroleum. The method used to separate hydrocarbon compounds is called fractional distillation. Crude oil is pumped into the chamber and then it is heated. Each hydrocarbon compound boils at a different temperature thus allowing them to be separated.

4. 25-1 The good and bad of Fossil Fuels
You use petroleum every day for electricity and transportation but not all the effects of petroleum usage are helpful to you or the environment. Burning petroleum in cars and at electric power plants gives off smoke as well as carbon monoxide and other chemicals. These particles and compounds affect the quality of the air you breathe.

5. 25-1 Other Fossil Fuels Natural gas, like petroleum, is a fossil fuel.
It is often found lying above liquid petroleum below Earth's surface and is extracted with petroleum.
Natural gas is mostly methane CH4 but it also contains smaller amounts of hydrocarbons such as propane C3H8 and butane C4H10. Carbon dioxide and water are given off as chemical byproducts of the combustion of these products.

6. 25-1 Coal Coal is a solid fossil fuel made from the remains of plants.
About 1/4th of the world's supply of coal is in the U.S.
It is sometimes mined near the surface but is more commonly mined several hundred feet underground. The quality of coal depends on its age and on the type of plant life from which it formed.

7. 25-1 Fuel Conservation
Fossil fuel reserves are decreasing as our population and industrial demands are increasing.
At our current rate of consumption, the U.S. may be out of oil in less than 100 years. Coal is more plentiful but like petroleum it is a nonrenewable resource.
All fossil fuels are nonrenewable resources- they cannot be replaced after they are used.

8. 25-2 Nuclear Energy
A nuclear reactor uses the energy from a controlled nuclear fission chain reaction to generate electricity.
Once the core of the reactor contains fuel (uranium oxide) a chain reaction starts from a single uranium atom splitting in two which releases 2 neutrons. In 3 milliseconds, 1 billion neutrons would be produced. The reactor would be out of control. Rods containing boron or cadmium are inserted in the reactor to capture more neutrons and slow down the chain reaction. The core is surrounded by water that cools it. The heated water is used to produce the energy. The entire building is built with steel lined concrete to prevent the escape of radiation from the reactor.

9. 25-2 Nuclear generation of Electricity
Nuclear fission reactors currently supply over 20% of our nation’s electricity.
One advantage of nuclear energy is that it is less harmful to the environment than the use of fossil fuels.
There are disadvantages to nuclear reactors.
- the water must be cooled before being returned to streams/rivers or it will damage the ecosystem.
- there is a risk of the escape of harmful radiation. Nuclear reactors have elaborate systems of safeguards to ensure this doesn’t happen. Strict safety precautions and highly trained workers prevent most accidents but there is always a potential

10. 25-2 Nuclear Waste Disposal
Because the fission products have long half-lives, they must be stored in containers that will last the duration of the period of radioactive decay, which can be as long as tens of thousands of years.
After about 3 years there is not enough fissionable U-235 left in the fuel pellets to sustain the chain reaction. These used fuel pellets are called “spent” fuel. This spent fuel and left over uranium are termed nuclear waste.
After spent fuel is removed from a reactor, it is stored in a deep, heavily insulated pool of water. Waste must be disposed of in extremely durable containers.

11. 25-2 Fusion Power
Imagine the amount of energy the sun must give off to hear Earth 93 million miles away. The process that created the sun is thermonuclear fusion.
Thermonuclear fusion is the joining together of small nuclei at high temperatures.
If we could make this happen in a laboratory, we would likely have the answer to Earth’s energy problems.
The temperature needed to carry out a nuclear fusion reaction is over one million degrees Celsius.
Hydrogen is the most abundant element in our universe and the products of nuclear fusion are not radioactive. Someday nuclear fusion may provide a permanent and economical way to generate electricity.

12. 25-3 Breeder Reactors
A breeder reactor is a nuclear reactor that produces, or “breeds,” new fuel as it operates. In a breeder reactor, some of the neutrons produced by the fission of U-235 are absorbed by the U-238 nuclei while other neutrons cause fission of U-235.
The U-239 nuclei decays in several days to form Pu-239 which is fissionable. After operating several years, a breeder reactor can produce twice as much fissionable fuel than it started with.
It posses the same risks as other nuclear reactors.

13. 25-4 Alternative Energy sources
Using fossil fuels and nuclear fission for our energy needs has many disadvantages. Both methods are used to boil water to produce steam. Other materials can be burned to give off energy as well.
Biomass is renewable organic matter such as wood, sugar cane fibers, rice hulls and animal manure. Biomass can be burned to convert the stored chemical energy to thermal energy.
Biomass burning is probably the oldest use of natural resources for human needs.

14. 25-4 Solar Energy The sun is Earth’s only source of NEW energy.
Methods of collecting and using solar energy are usually divided into two categories, passive and active solar energy.
Passive solar heating is the direct use of the sun’s energy in maintaining comfortable indoor temperatures.
In active solar heating, solar panels collect and store solar energy. A device used to convert solar energy into electricity is the photovoltaic cell, also called the solar cell.
This method of producing electricity is more expensive on a large scale than the use of nonrenewable fuels. Solar energy is a pollution free resource that is becoming more economical as technology develops

15. 25-4 Hydroelectricity

16. 25-4 Hydroelectricity
Near the base of hydroelectric dams, water is allowed to rush out through tunnels.
The rushing water spins a turbine, rotating the shaft of an electric generator to produce electricity.
Hydroelectric power plants are a very efficient way to produce electricity with almost no pollution.
After the initial cost of building a dam and power plant, the electricity is relatively cheap. However, artificial dams can disturb the balance of natural ecosystems.

17. 25-4 Tidal Energy

18. 25-4 Tidal Energy
A kind of hydroelectric power can be generated by ocean tides. The moving water can be trapped at high tide by building a dam at the opening of a river or bay. The flowing water at low tides spins a turbine, which operates an electric generator. Energy generated by tidal motion is called tidal energy.
There are only a few places on Earth where the difference between high and low tide is large enough to be an efficient energy source.

19. 25-4 Wind energy

20. 25-4 Wind energy
A windmill is a turbine that is turned by the wind instead of steam or water. The windmill spins and rotates and electric generator to produce electricity.
Only a few places on Earth consistently have enough wind to rely on wind power to meet their energy needs.
Wind generators do not use up any resources, they do not pollute the atmosphere or water but they do change the appearance of a landscape.

21. 25-4 Geothermal Energy

22. 25-4 Geothermal Energy
Beneath the surface of Earth lies hot gases and molten rock which give off heat. This heat or thermal energy from inside Earth is called geothermal energy.
In some places, Earth’s crust has cracks or thin spots in it. These areas allow some of the geothermal energy to rise up near the surface of Earth. EX: volcanoes, geysers shoot steam and hot water i.e. “Old Faithful”
Wells can be drilled to pump out hot water that ranges in temperature from degrees. The steam can be used to rotate turbines and turn electric generators. There are only certain places on Earth where geothermal energy is accessible as an economical energy resource.