1. Energy Review
8th grade science

2. What is energy?
Energy is any source of usable power

3. Renewable vs. nonrenewable
Renewable sources are…
Energy sources that are replenished as quickly as they are being used.
Nonrenewable sources are…
Energy sources that can not be replaced as quickly as they are used.

4. Energy sources Renewable Nonrenewable Solar Hydroelectricity
Geothermal
Biomass
Wind
tidal
Coal
Natural gas
Petroleum (oil)
Uranium

5. Solar energy
Solar energy is the energy received by the Earth from the sun in the form of radiation.
Solar panels are called photovoltaic (PV) cells. They convert sunlight directly into electricity.
The PV cells convert the particles of sunlight into electrons of direct current electricity.
The electrons flow out of the PV cells and into an inverter. Here the DC power is converted into alternating current power.
One difference between solar energy and other renewable resources is that solar energy does not require the use of a turbine.

6. Hydro-electric energy
Hydro-electric energy is a source of energy that uses the flow of water to create power.
Some advantages include no waste or pollution. Also, water can be stored for use when needed.
Some disadvantages include negative effects to the ecosystems. Also, dams are expensive to build.
Hydro-electric power uses water from lakes or rivers that is trapped behind a dam. The water is allowed to flow through tunnels to turn the turbines that drive the generators producing electricity.

7. Geothermal power
Geothermal power is the energy produced by heat within the Earth.
Geothermal power requires the use of hot rock, near volcanoes, that heat water underground. This produces steam that turns the turbine driving the generator to produce electricity.
Advantages?
-No pollution
-Power stations are small and don’t impact the environment very much
Disadvantages?
-Hazardous gases and minerals may come up from the ground
-Not many places for power stations

8. Biomass fuel
Biomass fuel is a source of energy that creates power by burning a once living organism (plants) or waste from a living organism (manure).
Biomass fuel uses wood, sugar cane, plant and animal waste, sea weed, or cornstalks that are burned to provide heat. The heat heats the water that makes steam that turns a turbine driving the generator to produce the energy.
It is cheap and demands less of the earth’s resources. However, it creates pollution and is not always available.

9. Wind power
Wind energy is energy created from the movement of air over Earth’s surface.
Wind is created by the sun heating the air in our atmosphere. The wind blows propellers that turn generators that produce electricity.
Wind is free and it does not produce pollution or waste. It is not predictable and is not always a reliable source. It is also noisy and can kill birds.
Wind turbines are giant and require enough room where there is a steady flow of wind in order to produce energy.

10. Fossil fuels
Fossil fuels are nonrenewable energy resources formed from the remains of organisms that lived long ago.
Natural gas, petroleum, and coal are examples.
The coal is crushed and burnt, or the oil or gas are burnt directly to produce heat. The heat heats the water that powers a generator.
It is cheap and easy to transport. However, it produces lots of pollution (increased sulfur into the environment causing acid rain and increased CO2 emissions causing global warming) and will eventually run out.
Obtaining fossil fuels cause oil spills in the ocean (BP spill), destruction of land, and the creation of “sludge” that is harmful to wildlife when put into tailing ponds.

11. Nuclear energy
Nuclear energy is a source of energy that is created when the atoms of radioactive materials are split (nuclear fission).
Uranium atoms are split in a nuclear reactor producing heat in the fuel rods. The heat heats the water that produces steam that turns the turbine, powering the generator.
It is a reliable, inexpensive, and abundant resource. The waste it produces is very dangerous and it costs a lot for safety precautions.

12. Law of conservation of energy
States that energy cannot be created or destroyed.
Conservation means saving our nonrenewable resources.
Why would we want to do this?
How is energy transferred within a system?
It is lost in the form of heat

13. Why not switch to renewable resources?
It is more expensive
People find it hard to change what we have
Not everyone is educated about our energy sources
People do not know the long term effects of using renewable energy sources