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For kids: Electricity from the sun

A California school district is one of the first in the nation to 'go solar.'

By Keely ParrackCorrespondent of The Christian Science Monitor / November 4, 2008

Sunshiny day: At Walnut Grove Elementary School in Pleasanton, Calif., students gather around a solar oven.

Keely Parrack

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Pleasanton, Calif.

You may have heard a lot lately about solar and other earth-friendly energies. So what's so cool about solar power? Well, for one thing, Earth receives as much energy from the sun in one hour as the world uses in one year!

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For thousands of years, humans have taken advantage of the sun's energy for growing crops, drying clothes, sunbathing, and more. Yet it is only relatively recently that people figured out how to harness the sun's rays and transform this free, clean, and renewable energy into electricity.

Journey toward harnessing the sun

About 1861, Auguste Mouchout, a French inventor, made the first solar-powered motor. It was a glass-enclosed iron cauldron. When sunlight passed through the glass, the water heated up and created steam, which powered the engine. Many moving things such as trains used steam-powered engines in those days. But steam normally came from water heated by burning coal. As coal became cheaper in France, the French government decided that although Mouchout's invention worked well, it was too expensive to produce. This was true for many solar inventions that followed.

Albert Einstein won the Nobel Prize in Physics in 1921 for his research on the "photoelectric effect," a phenomenon that helped scientists see how light could be converted into electric current. In 1940, American engineer Russell Ohl discovered that light shining on a cracked crystal caused a small electric current. This led to his creation of the first silicon solar cell, but it produced only a small amount of electricity.

In 1954, scientists Gerald Pearson, Daryl Chapin, and Calvin Fuller developed the first silicon solar cell capable of making a measurable amount of solar power. But compared with coal and oil, making electricity from solar power was just too expensive.

In fact, it wasn't a scientific breakthrough that helped solar to become more readily available, but mass orders of solar photovoltaic cells (PVs) from countries such as Japan and Germany. Their governments started solar rooftop programs (Japan in 1994 and Germany in 2000) to improve environmental protection. After that, people in both countries began demanding more solar panels, which caused the price of PVs to drop. When solar cells are cheaper, more people, organizations, and governments can afford to use them.

Solar schools

Earlier this year, the Pleasanton Unified School District in California became one of the first and largest school districts to "go solar."

Solar s’mores

With your own solar oven, you can make ooey-gooey s'mores with sunlight!

(This version of the oven was inspired by Mrs. Kato at Walnut Grove Elementary School.)

What you will need:

• One large piece of cardboard, or two pieces of poster board taped together to make one long piece

• Aluminum foil

• Bucket or medium-size cardboard box

• 2 graham crackers

• Marshmallows

• Zippered plastic bag

• Part of a chocolate bar

Directions:

Have an adult help you to…

1. Cover one side of the cardboard or poster board with aluminum foil.

2. Fold the cardboard or poster board to make a cone shape. The foil should be on the inside of the cone.

3. Put the small end of the cone into a bucket or cardboard box. (Be sure that the cone's small end is large enough to encompass a s'more.)

4. Place a graham cracker topped with a marshmallow or two inside the plastic bag, zip it up, and place it in the bucket or box at the bottom of the cone.

5. Make sure the sun shines directly into your oven.

6. Check the graham cracker and marshmallows every 10 minutes.

7. When the marshmallows start to melt, add the chocolate, reseal the bag, and put it back in your oven.

8. Continue checking your s'more every 10 minutes. When the chocolate is melted, remove the s'more and top it with the second graham cracker.

Voilà! You've cooked a tasty treat using only the sun's rays.

To read more about solar ovens and what happened when other kids experimented with them, visit the PBS Kids Zoom website at http://pbskids.org/zoom/activities/sci/solarcookers.html.

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