Monday, May 17, 2010

Solar Energy For Younger kids

Monday, May 17, 2010

Solar Energy Younger kids

Solar Energy Older kids

Solar Energy Younger kids

1. What's so great about the sun, anyway?

The sun is amazing. Without it, none of us would be here, and there would be no life on earth. It is bigger than anything we can really imagine--a million planet earths would fit inside it! It takes millions of years for the energy from the center of the sun to reach the sun's surface, and then just eight minutes for it to travel the 93 million miles to earth! The sun gives off more energy in one second than people have used since the beginning of time.

But wait, there's more! Plants make food out of sunlight, and then animals eat plants, and then we eat animals (or maybe we just eat plants, if we?re vegetarians). Either way, without sunlight, plants couldn't make food, and there would be nothing for us to eat. Not only could plants not make food without the sun, they also couldn't make oxygen, and no animals could breathe, including us! The sun produces nearly all the heat on the planet, too--without it, the earth would be freezing cold--minus hundreds of degrees Fahrenheit, almost as cold as space. The sun also makes the wind blow and the ocean currents flow. Its heat makes clouds, rain, snow, and all the weather on our planet, too.

2. What does solar energy mean?

Solar energy just means energy (light or heat) that comes from the sun. There are as many different ways to use solar energy as you have ideas in your head. What gets you hot lying on the beach on a summer day? Solar energy. What gets your car hot when it's parked in the sun with the windows closed? Solar energy. What makes your solar calculator go? Solar energy. What makes the giant solar panels on satellites work? Solar energy. What makes plants grow? Rain and... solar energy. What makes the clouds that make the rain? You got it! Solar energy. What sets a blade of glass under a magnifying glass on fire? Yup, solar energy. And on and on.

Check out ThinkQuest's cool history of energy on planet earth.

And if you want to know more about the sun or energy in general, their entire website is pretty cool.

3. Is solar energy new?

No! Solar energy has existed for five billion years, since the sun was born. And humans have been using solar energy for thousands of years. 700 years before the year one, people used simple magnifying glasses to concentrate the light of the sun into beams so hot they caught wood on fire. The Greeks were the first to use solar architecture, over 2,000 years ago. They built their houses so the sun's rays entered during the winter, but weren't able to enter during the summer. Entire cities were built this way! (They were way ahead of us.) The Romans got the idea to put glass in windows, which allowed the sun's light to pass through but trapped its heat. They even built glass greenhouses so they could have fruit and vegetables all winter.

Skipping ahead a few thousand years, in the 1700s someone in Europe figured out you could make water boil by collecting the sun's heat behind a few panes of glass. A solar hot water heater! From the early 1920s to just before WWII, everyone in Florida heated their water with solar hot water heaters.

Using solar panels to turn the sun's light directly into electricity is new, though. That technology was only invented only 50 years ago.

(Most of this information on the history of solar energy use comes from

4. What are different ways we can use solar energy?

A few questions back I said that there were endless ways to use solar energy. That's true, but, to make things easier to think about, all those ways can be divided into two basic categories. First, we can use the sun's energy to heat things--our houses, the water in our houses, the food in a solar cooker, and so on. This is called solar thermal energy. (Thermal means heat, so solar thermal energy just means heat energy from the sun.) The second basic way we can use solar energy is to turn light from the sun directly into electricity, using solar panels. This is usually called photovoltaics, and we?ll talk more about it in the next question.

5. How do solar electric panels work?

Solar electric panels are made up of something called silicon, the same thing that makes up sand. There is more silicon on the planet than almost anything else. Even though you can find silicon almost everywhere, making a solar panel is difficult and expensive. The silicon has to be heated to super high temperatures in a big factory, and then formed into very thin wafers.

When sunlight hits a solar panel, it makes electrons in the silicon move around. (Electrons are teeny tiny specks--they?re way too small for us to see, even under a microscope.) The electrons flow through wires that were built into the solar panel. And presto! We have electricity! We can do whatever we want with this electricity, run a calculator, a CD player, or, if we have big enough solar panels, a satellite! [Solar panels are also called photovoltaic panels. "Photo" means light and "voltaic" means electricity.]

6. What if I want my solar panel to make electricity at night, or on cloudy days?

When the sun stops shining on your solar panel, its electrons stop moving and electricity stops flowing. So what do you do if you want to be able to read or watch television at night? (But you don't watch television, do you?!) What stores the electricity in a flashlight? Right! A battery! And that's exactly what people do with solar panels... they attach batteries. The batteries are big, heavy, rectangular boxes, sort of like car batteries. Electricity from a solar panel flows into attached batteries while the sun shines, and then the stored electricity in the batteries can be used at night, or when the sun is behind the clouds.

7. Where are solar electric panels used?

Have you seen those big orange signs along the highway with flashing messages about an exit being closed or a traffic jam ahead? Ever look on top of those signs? Yup, there are big solar panels up there. Those solar panels are attached to batteries, so the signs stay lit at night. Little solar panels are used on solar calculators (the panel is usually in a little strip across the top). You might have seen solar panels on people's roofs or on poles in front of their houses. And how about in space? You know those flat, black "wings" that stick off satellites and space stations? Yeah, solar panels! Can you think of other places you?ve seen a solar panel, or that would be a smart place for one?

For cool stuff on satellites and space stations, check out:

8. How many solar electric panels would I need to power my house or apartment?

That depends on how much electricity you use in your house, and how much sun shines where you live. You need a lot of panels to power a whole house, though. The first thing you'd have to do, before you "went solar," would be to cut down on your electricity use. Otherwise you'd need so many panels that you'd go broke buying them and you'd have no room to play outside, because everything would be covered in solar panels. The average size of a solar system that completely powers a house is 2,000 watts. That's not a lot of power--just enough to run 20 or 30 light bulbs. (Except that if you were going to run your house off solar panels, you wouldn't use the same old light bulbs you've been using, that mostly make heat and just a little bit of light. You'd use super-efficient, long lasting florescent light bulbs.) To make 2,000 watts of power you need solar panels that are about 24 feet long by 10 feet high. That's about as long as one and-a-half cars and a little higher than most of your ceilings. That's still a lot of panels. But once you get them up, they last for well over 20 years. And since they have no moving parts, they almost never break.

9. Where does most electricity come from?

Have you ever thought about what happens when you flip on the light switch and the light turns on? Electricity is flowing to the light bulb, but where does it come from? In the U.S., most of our electricity is made in giant power plants that burn coal or natural gas, or are powered by large dams or nuclear energy. That electricity sometimes travels a long way from the power plant to your home, often hundreds of miles. If you live in the country, you?ve probably seen giant towers with lots of wires running between them. (If you go close to them, you can sometimes hear them humming--that sound is being made by electrons running through the wires!) From the wires on those giant towers, electricity travels to smaller power lines on poles, which often run along roads or streets. If you live in a city, electricity probably arrives at your house in wires that run underneath the sidewalk.

10. How can I save energy and electricity?

If you're not using a light, or if you're not using the computer, or if you're not watching the TV, turn them off!! Riding your bike or walking or taking the bus or the train instead of getting in a car and driving somewhere saves a lot of energy, too. So does taking shorter showers (that makes me very sad, because I love long showers).

Once you start trying to save energy, you'll find that there are some things in your home that you might not have to use at all. Instead of using a clothes dryer, for example, you can dry your clothes outside in the sun. Instead of playing a computer game, you can go do the dishes. (Just kidding! Sort of.)

Eating food from your own garden, or food that's grown and put into packages near your home also saves energy. (The label on the package usually says where the food comes from.) Reusing and recycling things saves energy, but it saves even more if you don't use them in the first place!

Once you start thinking about it, you'll find there are lots of ways to use less energy. It's even a fun thing to try and do.

11. What is solar cooking?

In the United States, the stoves in our houses run on electricity or gas. In other parts of the world, many people still cook over campfires. One of the many cool things about solar ovens is that they don't need electricity, gas, or wood to work--they cook food using only sunlight! Basically, you put food in a box and trap the sun's heat by covering the box with glass or plastic. (Solar cooking is an example of using solar thermal energy.) And they're easy to make! You can make one with two cardboard boxes, one inside the other, covered with glass or plastic. You can put crumpled-up newspaper between the two boxes to help trap the sun's heat, paint the inside black, and put aluminum foil outside to help reflect more sun into the cooker. Even a simple solar cooker like this one can reach temperatures over 250? F.

Solar cookers are great because they save money and energy, and produce no pollution. People don't have to cut down trees for firewood, and they make no nasty smoke to hurt people's lungs, things that are big problems in countries that don't have as much money as we do. Solar cookers can also be used to make water safe to drink, make doctor's tools safe to use, and heat water for laundry.

The best solar cooking web site we've seen is They have great instructions for making your own cooker, and lots of other cool information.

12. What can I cook in a solar oven?

Anything you can cook in a normal oven--the limit is your imagination. Just remember to use a dark colored pot, and use potholders! Solar ovens get hot!

13. Are there solar energy power plants?

Yes, there are a few. They are usually in hot, dry places, like deserts in California. Many different countries are planning to build more soon, and we're really looking forward to it! (There are basically two different kinds of solar energy power plants. One kind makes electricity using lots and lots of solar electric panels. The other actually makes electricity using the sun's heat--solar thermal energy. Basically, solar thermal power plants use lots of mirrors to focus the sun's rays onto one central area. That heat is used to boil water, and then the steam produced from the boiling water is used to make electricity--just like in a coal or natural gas burning power plant.)

14. How much of the world's energy does the United States use?

Of every 100 people on the planet, 6 live in the United States. If everything were fair and equal, we would use as much of the world's energy as we have people--6 percent. Instead, we use between 25 and 30 % of the world's energy! Each of us uses twice as much energy as the average person in England, two and-a-half times as much as the average person in Japan, and 106 times that of the average person in Bangladesh!. And using too much energy isn't just bad because we're going to run out of it someday. It's also bad because it produces pollution. Per person, people in the United States produce way more "greenhouse gases" than any other people on the planet.

15. If solar energy is so cool, why isn't everybody using it?

Even though humans have been using the sun's energy for thousands of years, photovoltaic (solar electric) technology is still very new, and a lot of times adults don't like to try new things. Even if they are the type of adults who like new things, sometimes it's very hard to switch to a new system once you have another system working already. (We have all those giant coal burning plants built already--what would we do with them if we built solar plants instead?) Solar energy technology is also getting better every year, so a lot of people might not realize that it's become as cool as it has.

Making electricity with solar energy is still more expensive than making it by burning coal, and adults definitely don't like expensive. [Actually, though, if you count how burning coal hurts the environment, and if you count that the government helps pay for electricity made in coal plants, solar energy might not really be more expensive. Some people think that if you counted everything fairly, solar energy would actually cost less than electricity made from burning coal.]

The exciting news is: YOUR generation has a great chance to use solar energy!! If you keep learning and thinking more about energy and how you use it; and learning and thinking more about different kinds of solar energy; and maybe bugging your parents and your teachers and your congress people about it, maybe by the time you're our age, everyone will be using solar energy!

If you want more information, check out our info for older kids!


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