The Sun As a Source of Heat

Introduction

So you have decided to make the sun work for you. The sun is a source of light, heat, and energy. Before you can make the sun work for you, you must understand some basic things about the sun.

The temperature of the sun is very, very hot, (millions of degrees). However, the sun is so far away, most of the temperature is scattered in the air before it reaches the earth to warm it. Luckily for the earth, and us, would burn up. If you want to use the heat from the sun, first you must find a way to collect as much sunlight as possible. Then, you must concentrate the sun over the surface you wish to heat. As you heat the surface, you will want to trap the heat, and keep it from escaping.

Okay, now what do you want to heat? Well, when you cook food you are only heating it long enough to make it soft, and tasty if it is raw, and to make it warm or hot if it is cold. You heat or cook food.

Also, your teacher at school always told you that some things have germs on them. Germs are invisible and they can make you sick. Heat can kill germs. If I can kill the germs in water or wash with heated water then germs on things I use can be killed. Germs are everywhere and unavoidable. I must repeat- killing of germs on dirty clothes, dirty hands and all things, germs must be killed many times a day, everyday.

As you know the sun is hottest when it is directly overhead. This is usually from 10 am-2pm. Before that, and after the sun is visible, but it is not so hot when it reaches the earth. In the very early morning the sun starts low in the sky, and slowly gets higher, and higher. When it reaches it highest point, then starts getting lower with time.

Your aim to always make it appear as though the sun is directly over head. You must be clever to do this. As you know the sun is always moving. if there is any interference (anything that stands between you and the sun to block the heat, the amount of sun that can be collected will be reduced. Anything, like clouds, bad weather like rain, shadows create problems. All these problems you must solve or else the sun will not work for you. You will learn to create many ways to create the best conditions for the sun to work for you.

1. What do I want to heat and why use the Sun?

You can heat anything as long as it fits into the container where you trap the heat and concentrate it on what you intend to heat. You should clean whatever you put inside your mouth or on open wounds so that the germs do not enter the body and make you sick. Heated water can kill germs and it is very necessary to remove germs. Use the sun to get heat free of cost. You can even clean the water itself by heating it. It does not have to boil to kill the germs. It just needs to be very hot to touch. Heating water is easier than cooking with the sun. Water exposed to sun can reach a high temperature if it is in something that holds heat or absorbs it well. Dark colors or black color is the best surface. Of course, you will learn later the importance of covering water to keep the heat from escaping. Remember question #4-How do I keep the heat from escaping?

One more thing, right now too many people use wood for heating and cooking. That is not a good thing. In some areas, it is difficult to find wood, there is less and less each day. if we don't reduce using it, your children will not have wood , and they can not enjoy the shade of the trees and their beauty. What a pity! Also, wood burning produces smoke. It gets into your lungs and makes it hard to breathe. It can damage your lungs. Use less wood and protect your health and that of your children.

2. How do I collect heat from the sun?

The temperature you can collect from the sun is limited only by the size of the collector you use to concentrate the sun's heat. The larger the collector, the more heat you collect, but you can get into trouble if it is too large or too small. I'll let you experiment to find out what I mean. This is the answer to the second question.

3. How do you get as much heat as possible?

The size of your heater or cooker is important. The larger the area used to collect the sun, the more sun is collected. The larger the space to fit what you are heating or cooking, the more heat or cooking. There is one more very important factor-concentration. The more directly the sun shines on what you are heating or cooking the hotter it will get. If you can concentrate the sun the hotter it will be. In other words, you want to reduce the scattering of the sunlight. Just think on a hot day, the sun is beating down on you. It is so hot, no shade. On the same day, it is much cooler in shade under a tree because the tree scatters the sunlight. The opposite is true if you concentrate the sunlight. It will be hotter. Shiny surfaces, help concentrate the sunlight as you collect it. Shinny surfaces like metal, mirrors, and aluminum, shinny tin (polished tin, copper, etc.) Can you think of others?

When the shinny surface catches the sunlight, the light hits one surface and bounces onto another (trying to get away; If the sunlight is surrounded then it can not escape. It is captured or concentrated. If some sunlight gets away, no mine, you'll get more. The more of the sun is concentrated, the higher temperature you can obtain.

4. What do I do, to keep the heat from escaping or how do I contain it?

One easy way to keep anything from escaping is to trap it. Once the heat is inside something put a cover over it. The cover can be clear plastic (it must be the kind that only melts at high temperatures) or use a glass. You want to use something you can see through so that the sunlight can continue to go through and add more heat.

Also to increase the amount of heat inside use something to hold it or absorb it. Dark colors or black colors do this very well. What you are heating will hold more heat if it is dark. If it is a pot, it will get hotter if it is black and sits on something black. One more thing, metal holds heat and absorbs it. It also will transfer all of heat to another metal. So, metal sitting on metal will transfer heat to whatever it is in contact with it (water, food, whatever). One last thing. If you can create an air space between the walls of your structure you place whatever you are heating, it will help keep he heat in.

So in summary collect the heat from the sun. It will give it to you free. Concentrate the heat to get a high temperature. Finally, trap the heat to keep it from escaping until you are finished heating whatever you need. Just remember you are not the first to try it. People in Asia, other places in Africa, America (north and south have been experimenting for 100's of years. From time to time they forget about it, but whenever, the fuel for heating is less, expensive, or causes problems they go back to the sun. Not only is it free, but does not create health problems. The designs to collect, concentrate and trap the heat from the sun are many. Some ideas for heating with the sun others have used will be shared here. None of these are perfect. If you understand the basic ideas about the sun, you can improve upon these ideas or create your own. It is easy. Share your ideas with a friend. In the US, they say two heads are better than one. Even, a child can contribute ideas when he or she understands how the sun works.

Basic shapes used for collecting the sun's heat

Box shape

It is really a box. The thing being heated is inside the box

2. Concentrate (Surround the Sun)

CONCENTRATOR OVEN

The collector surrounds the thing being heated. It is placed above it. Support the collector with a structure on which it can rest.

3. Flat collector

The collector and the thing being heated are kept separate.

It is possible to combine the different shapes to increase the temperature. Remember the collector must be a shiny surface to collect the sunlight and bounce it onto the thing being heated.

Now, if you believe it is a good thing to cook or heat anything with sun, lets see your ideas on how to make the sun work for you. Do you still remember the basic things about the sun you read about when you first started. if you don't remember, then make a short review of the beginning. How well you make the sun work for you is left up to you. You must decide how you will collect the sun and concentrate its heat.

How to make a Concentrator Collector

1. Gather Materials

Glass window or plastic- the size of the opening of your box - allow sunlight in and keeps the heat from escaping

Dark cooking pot- use glass or plastics

Big cardboard box (or wood or whatever material you want to put the food inside).

Remember, the heavier the material, the heavier the cooker and the harder to move about.

Some extra cardboard for making the reflector, and for insulation

Aluminum foil - enough to cover your collector or shiny surface the bigger the collector the more

foil; the more expensive to make the cooker.

Crumpled newspaper- to keep the heat from escaping through the inside of your box

String-to hold the sides of your collector together; Also a needle to thread the string through holes you make in the part of the reflector; can be used to hold aluminum foil in place

Knife or Scissors-to cut cardboard or string or newspaper

A black plastic bag- to place under whatever you heat

Metal tray or flat lid-to place under whatever you heat

Cut 4 triangles

All sides must be the same length
and fit between flaps. See drawing

Sewing the triangles into place with and thread. All four.

Sew the bottom of box to make it strong. Make two holes opposite one another, and thread through and make a knot; and then cut the thread.

Prepare a narrow shelf to sit the glass on all 4 sides inside the box near the top of the opening. Be sure they are at the same height and are level.

Place tray in the box of your box and cover with a black plastic bag or cloth. Place the plastic (clear ) or glass over the pot. Place glass over the opening of the box. To be

sure it rests secure on the narrow shelf on all four sides and is flat. make sure no air can get inside the box to avoid losing the heat.

Place the box flat on the ground or tilt the box until the sun is concentrated on whatever you are cooking or heating. You should see the sun when you look through the glass focus on what you are cooking.

Do not open the box until cooking is done.

Adjust the position of the box so that the sun remains concentrated on whatever is cooking or is being heated. Check from time to time.

To preserve your box and protect it from water cover it with plastic or keep it dry.

To keep up with your cooker decorate it. Let the children help.

Keep your aluminum foil or shiny surface clean.

You can take the box apart to store in flat in a small place away from children.

Go to the Hyperlinks for Different Solar Cooker Designs