At some point during your lifetime, you could find yourself without potable water. Consider an island surrounded by saltwater or the dirty water of a river. Solar energy could save your life. Try constructing a solar still. Prepare saltwater by adding salt to clean water. Pour this saltwater into a large bowl until you cover a fourth of its capacity. Now, place an empty cup in the middle of the bowl. The top of the cup must be well above the water's surface. Cover the bowl with well-secured plastic wrap. Put a stone or heavy object on the plastic, just over the cup. This will create a curved depression that will help collect evaporated water. Place your solar still under the sun. After a couple of hours, observe the cup. Evaporated water will have risen to the top and dropped into the cup. Taste the water from the cup to determine whether it remains salty or pure.
The juice of citrus fruits can produce electrical energy. Prove this hypothesis with the following experiment. You need a lemon, a 2-inch copper nail, a 2-inch galvanized nail, a small light bulb and two pieces of copper wire. Press the lemon with your hand in rolling movements until the juice has spread inside of it. Now, insert the nails into the fruit 2 inches apart. Ensure that the tip of each nail is in the center of the fruit without touching the other nail. Strip the wires on both ends, and use electrical tape to attach one end of each wire to the positive and one to the negative electrodes of the light bulb. Firmly wrap the other ends of the wires, one to the galvanized nail and the other to the copper nail. Once both wires are connected, the light bulb will turn on.
Under certain conditions, decaying garbage produces gas. This provides a good way to recycle organic waste while generating combustion through the decomposition process. Verify this assertion with this simple experiment. You will need a pack of beans, some water and eight clear plastic bags that can be tightly sealed. Leave most of the beans immersed in water the whole night. Keep the rest of the beans dry. Take six bags and put 10 soaked beans into each one of them. Close the bags tightly. Place 10 dry beans into the remaining two bags following the same procedure. Distribute the bags as follows: two bags with wet beans in a sunny place, two similar bags in a shaded, warm place and the remaining two bags with soaked beans in an absolutely dark environment. Observe and take notes daily for a week. The water and beans will have generated gas. Keep the two bags of 10 dry beans with yourself, to keep as a control batch. Compare your results with the control bag so that you can assess the changes on the other bags in your experiment.
A solar water heater is based on a device called a collector. It collects solar energy to heat water. Many use this method in their homes. You can build a simple collector with a shoebox, black paint, 10 feet of flexible black tubing, tape, two cans and a rectangular piece of window glass large enough to cover the top of the box. Paint the interior of the box black. Install the tube in an "S" shape inside the box, and let both ends out through two holes in the sides of the box. Now, cover the box with the piece of glass and secure it with tape to avoid temperature loss. The collector is ready. Leave the device under the sun. Put both cans under each tube opening. Fill one of the cans with water and put one tube end into this can. Create a siphon effect by sucking from the other end to start the water flowing. You will see how the energy of sun heats the water.