Energy from the Sun
Solar energy is a “renewable resource.” This means that you can use it, and more is being made all the time. As long as the sun is shining, more energy will be there for us to use. Solar energy is collected for heating homes, businesses, and water. It's used to dry out agricultural grains like wheat and corn, herbs, and fruit. People use solar power to heat pools, greenhouses, and arboretums. Solar power charges emergency phones on American highways, keeps streetlights lit, and powers flashing road signs. Builders have even developed solar roof shingles!
Feel the Burn!
Stand in front of a window directly in the sun (this works in winter or summer). You can feel the heat from the sun on your skin, even though you are behind glass. If you keep standing there, you will feel hotter and hotter. Stay as long as you can until you start to feel sweat break out on your skin. Now step away from the window into the shade. Can you feel the temperature difference? This is passive solar energy and it really works to heat sunny rooms.
Solar power can even be made into electricity. This is called “photovoltaics.” Photovoltaic energy is when sunlight is collected by a “solar cell” and then passed through a special “semiconductor” to create an electrical flow. This was actually discovered accidentally by researchers at the telephone company in 1954, who were looking at how silicon reacted to sunlight.
Many solar cells are connected together into larger arrays to collect more power. The more solar cells there are, the more “watts” of energy they collect. Solar cells are not mechanical, so they take no energy to run and no water or cooling to convert sunlight to electricity. They make no waste that has to be thrown away. This is a clean and renewable energy.
The Dark Side of Solar PowerThe only problem with solar power is that it's not always sunny outside! Some places have more cloud cover that blocks sunlight, and of course there is no solar power collection at night. The ideal place for solar power is an area where there is little cloud cover, like a desert or other arid region that has some room for solar collectors to lie out and take in the sunshine. In the United States, the southwestern part of the country has the sunniest climate for solar collection, but homes everywhere can benefit from some solar collection. Even just big, south-facing windows can bring solar heat into a home. This is called passive solar collection.
The Space for SolarThe other problem with solar power is that you need a big area facing the sun to collect it. On a single home, the collection area can be on a rooftop facing the sun, but what about a tall building with many apartments? Or a whole city? It takes space to collect solar power. It is hard for big power companies to collect and sell solar power because sunlight collection takes a lot of space. There were only fourteen known large, solar-electric generating units working in the United States in 2004, all of them in California and Arizona.
Solar science has also only worked out how to make about 25 percent of the sunlight we get into power. Plus the silicon and metals in solar cells are very stiff and hard, so they can't be used for a lot of things that aren't flat. New plastic semiconductors are much more flexible and easier to make, but they only make 10 percent of the sunlight into power. Solar science still has a long way to go to be the endless, clean, free power we hope it will be, but it's getting there!
Have a Windmill Party
At your next party, make windmills! All you need are squares of paper 8.5″ × 8.5″ (Hint: You can use regular copy paper and cut 2.5 inches off the end to make it square. This is a great way to use up junk mail paper that hasn't been folded.) You will need enough squares of paper, thumbtacks, and pencils for each person making a windmill. You will also need some scissors and an adult helper to use them.
After your grownup helper has cut your squares, have everyone color their squares on both sides, with markers or crayons.
Ask your grownup helper to cut each square four times, one cut from each corner to about one inch from the center.
Have everyone take their thumbtack and push it into the pencil just below where the metal eraser band ends. Now pull it out again. That hole is where you will attach your windmill.
To fold your windmill, hold your newly cut square in your left hand between your thumb and forefinger. Try to keep your thumb right in the middle of the square (you'll have to push your hand down into one of the cuts to reach the center with your thumb).
With your right hand take the right corner of each cut section and fold it over in an arch to the center, trapping the tip under your thumb. (Don't crease the paper.)
Do this for all four sections. You have to keep all four tips under your thumb. This is a little tricky, especially if you all start giggling!
Now take your thumbtack and push it through all four tips and the center of your paper and pin it back into your pencil. You may need some help from your grownup helper.
You have made a windmill. Take it outside into the wind and watch it spin!
