In this issue:
- Build a Solar Oven
- Make a Solar Purifier
- Fabulous Facts
- Science Links
Every morning the sun rises, bringing light and heat to the earth, and every evening it sets. It seems so commonplace that we rarely spare a thought for that bright object in the sky. Yet without it, we wouldn't exist!
Unlike the earth, the sun is not a solid--instead, it is a huge ball of gas, composed mainly of hydrogen. Deep in the core of our local star, hydrogen atoms react by nuclear fusion, producing a massive amount of energy that streams in all directions at the speed of light (more than 186,000 miles per second). In just eight minutes, that energy travels 93 million miles to earth.
Energy from the sun comes to us in two ways: heat and light. Heat (thermal energy) is what is used in the projects in this newsletter. Light is used with photovoltaic cells, and is converted into electrical energy. Although there are some limits to using the sun as a power source (because it can only be collected during the day, and there is less sunlight on cloudy days), this giant gas ball at the center of our solar system is an enormous energy resource!
You can use the sun's energy to heat up a tasty treat with this simple solar oven! (Get an adult to help you with the cutting.)
>> Download our Solar Oven Recipes PDF to get ideas for what to make with your solar oven.
What You Need:
The heat from the sun is trapped inside of your pizza box solar oven, and it starts getting very hot. Ovens like this one are called collector boxes, because they collect the sunlight inside. As it sits out in the sun, your oven eventually heats up enough to melt cheese, or cook a hot dog! How does it happen? Rays of light are coming to the earth at an angle. The foil reflects the ray, and bounces it directly into the opening of the box. Once it has gone through the plastic wrap, it heats up the air that is trapped inside. The black paper absorbs the heat at the bottom of the oven, and the newspaper make sure that the heat stays where it is, instead of escaping out the sides of the oven.
Your solar oven will reach about 200° F on a sunny day, and will take longer to heat things than a conventional oven. Although this method will take longer, it is very easy to use, and it is safe to leave alone while the energy from the sun cooks your food. If you do not want to wait long to have a solar-cooked dish, try heating up something that has already been cooked, like leftovers, or a can of soup. Putting solid food in a glass dish and liquids in a heavy plastic zip lock bag works well. You can also pre-heat your oven by setting it in direct sun for up to an hour.
Other recipes you may want to try are making baked potatoes, rice with vegetables, chocolate fondue, s'mores, and roasted apples with cinnamon and sugar. Even on partly cloudy days there may be enough heat and light from the sun to slow cook a special dish. Here are a few tips for having success with your solar oven:
One great thing about solar ovens is how portable they are. Solar ovens are sometimes used in secluded areas of the world, where there is no electricity. Solar ovens are able to provide a way to cook for families in parts of Africa and Asia who do not have electricity, and might have to walk very far to find firewood. You could take a solar oven with you on your next camping trip - simply set it up, and let the sun do the rest. How else would you like to use your solar oven this year?
If you're feeling confident in using the collector box oven, you can experiment with baking bread! Since small amounts will cook more quickly, use a muffin tin to make mini loaves of bread, muffins, or cupcakes. Since the oven is at a lower temperature, baking will usually take between 2-4 hours. You can experiment with a variety of different recipes, as long as you are prepared to leave your solar oven outside for part of the day. Pre-heat your oven for best results.
To experiment with adding more reflective flaps, you could build another oven from a pizza box. This time, add a second or even third flap from cardboard covered in foil. Tape the flaps to the sides of the box, so that they direct light towards the center. This will focus more sunlight on what you are trying to cook, and possibly increase the temperature of the interior of the box. To see if it works, set your original pizza box and the one with extra flaps in direct sunlight. Put a simple dish (such as nachos with chips and grated cheese, a hot dog, or chocolate chips and cream to make fondue) inside each solar oven box, and check each oven every 10 minutes or so to see the results. Does the oven with multiple flaps cook the food faster?
To make a very simple solar oven that requires little preparation, line a large bowl with tin foil, and use a towel to prop it up at an angle towards the sun. This simple oven works because sun is reflected towards one point, about a foot in front of the center of the inside of the bowl. This kind of oven is called a parabolic cooker because the curved sides of the bowl make a kind of parabola. Because sun is being concentrated, be careful not to look directly into the bowl. Be sure to use caution when you take the food out of the bowl, or away from the oven.
This kind of oven works great for toasting a marshmallow! Stick one end of a wooden or metal skewer into the ground, less than a foot away from where the bowl is set up, and put a marshmallow on the other end. The marshmallow will not get as browned as it would over a campfire, but in about 20 minutes you will have a marshmallow that is deliciously gooey on the inside. Experiment more with the solar oven bowl if you like, by positioning it by the pizza box oven, so that it reflects light into the window of the box.
Sun Spot Solar Oven
This Sun Spot solar oven has specially-designed reflective panels to channel sunlight into a black-lined cooking box, which can get up to 500° F! You can make toast, reheat foods, cook steak, or even bake brownies using the cooking bag that's provided. The solar oven is easy to set up and includes instructions with recipe ideas and tips on cooking with solar energy.
You know how to cook food using the sun, but do you think it would be possible to get clean drinking water using solar power? Use heat from the sun to distill or purify salt water into clean water that you can drink. This works because the sun heats the water, and makes it evaporate. If you collect the evaporation, you have salt-free water.
The sun warms the water in the bowl until it evaporates, becoming a gas. When the gas rises, it hits the plastic and condenses there in droplets (just like water vapor condenses into clouds). The droplets roll down the plastic toward the weight and eventually fall into the glass (like rain falling from the sky). The salt is left behind in the bowl, making the water in the glass pure enough to drink.
Find out more about the sun at this NASA website.
Learn more about solar energy, and check out this world map of solar resources.
Check out the wide selection of solar oven recipes from this blog.
To build a slightly larger solar collector oven, visit this site.