The Power of Solar Energy

Lesson 1: What is Renewable Energy?

Objectives

Background

Activity 1: How Does Heat Affect a Turbine?

Activity 2: Demonstrating a Water Wheel

Wrap-up

Objectives 

• Students will define/explain renewable energy resources
• Students will demonstrate how two types of renewable energy systems work.

Background

Renewable energy comes from resources that are easily and continually replenished, such as the sun, wind, and water. In comparison, the fossil fuels (such as oil, coal, and natural gas) that we commonly use for energy, are nonrenewable. Fossil fuels are formed within the earth from ancient decayed plants and animals. These limited resources will eventually dwindle, becoming too expensive or too environmentally damaging to retrieve.

A renewable energy system converts the energy in sunlight, wind, falling water, and other resources into a form we can use, such as heat or electricity. Historically, renewable energy was used exclusively as man's energy source until coal was first used in the 13th century, oil at the end of the 19th century and uranium in the middle of the 20th century.

The most common renewable energy resources are:

• Solar energy—energy from the sun. Solar energy, can be used directly for heating and lighting homes and other buildings, for generating electricity, and for water heating, solar cooling, and a variety of commercial and industrial uses.

• Wind energy—energy from wind. The sun's heat drives the wind, whose energy is captured with wind turbines.

• Geothermal energy—heat energy extracted from reservoirs in the earth’s interior. Old Faithful geyser in Yellowstone National Park is an example of geothermal energy. Heat pumps, another geothermal application, provide heating and cooling for homes by utilizing the earth’s heat.

• Biomass energy—stored energy in plants and trees. Burning a log in your fireplace is an example of biomass energy.

• Hydropower energy—electricity produced from falling water. Most often, hydropower energy is captured through the use of dams on rivers to create large reservoirs of water. Utilities commonly use hydropower to produce electricity for their customers, accounting for about 10 percent of U.S. electric generating capacity. Dams provide electricity by guiding water down inside a pipe, called a penstock, and through a turbine at high speed. Although hydropower does not produce any air emissions, dams—especially large ones—cause serious environmental problems. Hydropower facilities have characteristically high initial investment costs and associated environmental impacts, but also enjoy the benefits of low operating costs, no pollutant emissions, and use of an existing renewable energy resource.

Activity 1: How Does Heat Affect a Turbine? (Source: Laura Haug, Energy Day)

Heat from the sun is a renewable source of energy. Illustrate how solar energy can move a turbine.

Materials:

• Three light bulbs of varying wattage
• Waxed paper
• Lamp
• Ruler
• Heavy thread
• Needle
• Scissors
• Watch with second hand

Method:

1. Cut a circle approximately 6 inches in diameter from the waxed paper.
2. Cut the waxed paper into a spiral with three or four loops.
3. Thread the needle with the thread. Run the needle through the middle of the spiral to make a turbine.
4. Light up the lowest wattage bulb. Hold the turbine about 8 inches over the bulb for about 20 seconds. Count and record the number of rotations.
5. Repeat step 4 for the other two bulbs.

Activity 2: Demonstrating a Water Wheel 
(Source: Laura Haug, Energy Day)

Moving or falling water is a natural, and renewable, source of energy. Make this small water wheel to illustrate how water can make things move.

Materials:

• Empty spool of thread
• Index card
• Thin straw or long nail that will fit inside the spool
• Tape
• Scissors

Method:

1. Cut the index card into strips measuring one inch by one and a half inches.
2. Fold the strips in half and tape to the spool to make paddles.
3. Put the straw or nail through the spool.
4. Hold the wheel under gently running water to see how moving water will turn the wheel.

Wrap-up

Ask your students to investigate how concepts would be applied to designing larger renewable energy systems. How would these basic designs be used to provide electricity? What other design components are needed?

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Next Section: Lesson 2 – Benefits of Solar Energy?