SOL 6.2

Renewable energy sources= sources that are constantly being supplied. Examples: sunlight, wind, trees

Solar energy= energy from the sun The sun constantly gives off energy in the form of light and heat. Solar energy is the source of most other renewable energy resources.

In one day, the Earth receives enough solar energy to meet the energy needs of the entire world for 40 years!

Solar energy does not cause pollution. It will not run out for billions of years.

Solar energy is only available when the sun is shining. A backup energy source must be available on cloudy days and at night. The energy received from the sun is very spread out. To obtain enough power, it is necessary to collect this energy from a huge area.

We have different ways of collecting the sun's energy. Improving technologies to capture and use solar energy will help meet future energy needs.

Solar Plants= rows of mirrors focus the sun's rays to heat a tank of water. The water boils, making steam that can be used to generate electricity.

Solar Cells= consists of a “sandwich” of very thin layers of the element silicon and other materials. The upper and lower parts of the sandwich have negative and positive charges like a battery. When the light hits the cell, electrons move across the layers producing an electric current. Used to power calculators, lights, telephones, and other small devices.

It would take more than 5,000 solar cells the size of your palm to produce enough electricity to power a typical American home.

What are solar cells made of and how do they work?

Wind= can be used to turn a turbine and generate electricity. Wind power plants are called “wind farms” and consist of many windmills. The windmills together generate large amounts of electric power. Wind farms now produce less than 1% of the world's electricity, but it is the fastest- growing energy source.

Wind energy is free and does not cause pollution. Wind energy is not ideal for all locations. Few places have winds that blow steadily enough to produce enough electricity. But, as fossil fuels become more scarce, wind farms will become more important.

Flowing Water= flowing water can turn a turbine and generate electricity in the same way as steam or wind. A dam across a river blocks the flow of water creating a reservoir. Water flows through tunnels at the bottom of the dam and the moving water turns the turbines connected to a generator.

Hydroelectric power= electricity produced by flowing water. It is the most widely used source of renewable energy in the world today. It is inexpensive and does not create air pollution.

In the United States, most suitable rivers have already been dammed, and dams can have negative effects on the environment.

Biomass fuels= fuels made from things that were once alive. Examples: wood, leaves, food wastes, manure. Burning breaks down complicated molecules in these fuels, releasing energy.

Biomass materials can also be converted into other fuels. Example: corn, sugar cane and other crops can be used to make alcohol. Alcohol + gasoline = gasohol Gasohol can be used as fuel for cars and trucks.

When bacteria decompose waste materials, they convert the waste into methane gas. The methane gas produced in some landfills is used for heating buildings.

Biomass fuels are not widely used today because producing alcohol and methane in large quantities can be expensive. Although wood is renewable, it takes time for trees to grow. In the future, biomass fuels may play a larger role.

What are the advantages and disadvantages of biomass fuels?

Geothermal energy= In certain regions such as Iceland and New Zealand, magma heats underground water to boiling temperatures. The hot water and steam are valuable sources of energy.

In Reykjavik, Iceland, 90% of homes are heated by water warmed underground.

Geothermal energy is an unlimited source of cheap energy. Unfortunately, there are only a few places where magma comes close to Earth's surface. In other places, deep, expensive wells must be drilled.

 Geothermal Energy is heat energy from inside of Earth that creates steam that we can change into electricity.

Hydrogen power= burning hydrogen as a fuel to produce electricity. ideal sounding, but it is very expensive to get pure hydrogen since most is combined with oxygen in the form of water. (Uses more energy than is produced.) Pros: It burns cleanly; creates no smoke, smog or acid rain. It can be easily transported through pipelines and it exists on Earth in large supply.

If scientists find a way to use excess electricity from solar power plants to separate the hydrogen, then in the future, hydrogen power could be an important source of energy.

Which of the renewable sources of energy is most likely to be used in your community in 100 years? Give reasons to support your answer.

Line up 15 dominoes to form a triangle. Knock over the first domino so that it falls against the second row of dominoes. Observe the results. Set up the dominoes again, but then remove the dominoes in the third row from the lineup. Knock over the first domino again and observe what happens.

Suppose each domino produced a large amount of energy when it fell over. Why might it be helpful to remove the dominoes as you did in Step 3?

Nucleus= the central core of an atom that contains the protons and neutrons. The reactions that involve nuclei, called nuclear reactions, involve tremendous amounts of energy. (Think the Sun!) These reactions convert matter into energy. There are 2 types: fission and fusion.

Albert Einstein developed a formula that describes the relationship between energy and matter. E = mc² This equation states that when matter is changed into energy, an enormous amount of energy is released.

Nuclear Fission=the splitting of an atom's nucleus into 2 smaller nuclei as a result of a neutron striking it. When the nucleus splits, the mass is slightly smaller because of energy being released (a LOT of energy) and more neutrons being released. This can create a nuclear chain reaction (think domino effect) if released neutrons continue to strike other nuclei. With each step in the chain, the energy increases rapidly.

If not controlled, this can cause a huge explosion. If controlled, the energy is released as heat, which can be used to generate electricity.

Controlled nuclear fission reactions take place inside nuclear power plants. The heat from the reactions is used to change water into steam. The steam then turns the blades of the turbine to generate electricity. A nuclear power plant has 2 main parts: reactor vessel and heat exchanger.

Reactor vessel= where nuclear fission occurs using fuel rods. The reactions are controlled using control rods. Heat exchanger= Where water passes through to create steam to run the electrical generator.

Today nuclear power plants produce 20% of the United State's energy and more than 70% in France.

Fuel rods can melt and cause explosions. This condition is called a meltdown. Radioactive materials can escape into the environment. (ex. soil can be contaminated with radioactive waste, which can be damaging to living things for many thousands of years) Scientists spend a lot of money to make nuclear power plants safe which can make nuclear energy more expensive than they once thought.

Nuclear fusion= the combining of 2 nuclei to produce a single larger nucleus. Mass is converted into energy. Fusion can produce more energy than fission. Fuel for nuclear fusion is readily available (water contains one of the kinds of hydrogen needed) It would also be safer and less polluting than fission.

Scientists have not yet been able to control a large-scale fusion reaction. Biggest problem is temperature. In the sun, it occurs at 15 million degrees Celsius--This would be impossible to control on Earth. Extremely powerful magnetic fields can contain a fusion reaction, but they take more energy to generate than the fusion produces.

What are 2 reasons that people have not been able to use nuclear fusion as an energy source?