Energy can be stored in many ways, but always by converting one type of energy into another. For example, objects in motion have kinetic energy, so energy can be stored in a spinning flywheel. Energy is added to the wheel to make it spin. As long as the wheel is spinning, the energy you added is retained. Then, when you want to use the energy, you can use the spinning wheel to create a current of electrical energy which you can then use for whatever you need. As you use the energy, the wheel slows down, until you have used all the energy you added in the first place, and the wheel stops.

Another way to store energy is through chemical potential energy. When you store energy in chemicals for later use, the structure that you use to store the energy is called a battery. In a battery, chemicals react and release electrons into an electric current, or electrical energy. In this way, the energy stored in the chemicals is converted into usable energy.

There are many, many, many ways for energy to be stored. It can be stored in chemicals that release energy during reactions (like gasoline), it can be stored as heat in an insulated container (like a thermos), it can be stored as motion in a rotating gyroscope, it can be stored as potential from gravity by lifting something up, it can be stored as electrical charge separation in a capacitor, as electrically-available chemical energy in a battery, as fissionable nuclear fuel, as fusible nuclear fuel, as /b>magnetic fields in static magnets, and probably more. In tiny quantities, it can even be stored as antimatter.

There are several ways to store energy. Compounds can store energy chemically, meaning that when compound A is mixed with compound B, they form compounds C and D, which have lower energy. By reacting to form C and D, compounds A and B release energy.

For example, if you react baking soda (compound A) with vinegar (compound B), you will form carbon dioxide (compound C) and sodium acetate (compound D).

This is how batteries work. Chemical reactions inside the battery encourage electrons to move from one end of the battery to another, which allows the battery to power phones, computers, flashlights, and electric cars.

There are other ways to store energy. In dams (or hydroelectric dams) dam , water falls from the top (the reservoir or lake) to the river below. As it falls, it turns a turbine, which produces electricity.

hydroelectric dam

Energy is generally stored in some system that has the ability to lose energy. What I mean by this is that there is usually an energetic phase that gives off energy to become a ground phase. When this is done with electricity in a battery, there are electrons that want to go from one part of battery to the other and can only do that when they are connected, usually with a metal wire. As the electrons pass through the wire, they transfer energy to the wire which is what powers our electronics. But there are a number of other ways to store energy. One of them is in chemically as in fuels. If you burn oil, it goes from a phase where it has tons of energy in the bonds between its atoms to a phase where it has very little energy in those bonds. When fuel is burned completely it leaves behind carbon dioxide and water which are very stable and don’t have much energy to give off.

Energy is also stored chemically in food that we eat. Our body can pull the atoms apart and take the energy in plants, animals, and other organisms. Energy can also be stored by gravity. If you put a rock on a cliff and push it off, it will release the gravitational energy that it stored in the process of bringing it up to the cliff in the first place. In this case, it may not be useful for us, but if we have water that is storing gravitational energy, we can make a hydroelectric plant. In this case, the energy of falling water is used to make electricity. There are many, many other examples since anything that uses energy has to get it from somewhere.

Batteries are one way to store energy. There's a lot of energy lost, though, when the energy is stored in a battery and then the battery is used to give energy to something like our flashlight or our car. Therefore scientists are trying to build better batteries. I remember talking with 2 scientists about this problem in 1973 when we were having dinner at a restaurant near our home in Isla Vista, California.

Wikipedia has a good article about energy storage. It has a picture of a dam that's used to store energy. Energy is released when water comes down out of the dam and turns wheels called turbines, and the energy of the moving turbines is used to make electricity.

People don't need so much energy at night, but some power plants produce the same amount of energy day and night. Wikipedia says some of the extra energy at night is used to make ice, and the ice is used for cooling during the day.

Food has stored energy, and we get energy to work and play and grow, by eating the food.