# Kinetic energy and how to accumulate it?

How can you accumulate kinetic energy? For example, when spinning a steel flywheel, we accumulate in it kinetic energy, which is an indispensable attribute of any rotating body. It is equal to half the product of the moment of inertia of the flywheel by the square of the angular velocity.

To what quantities can the kinetic energy be stored in such a flywheel? Increased the angular velocity by 2 times, and the energy increased by 4. Is there a limit to this? You can immediately say that the rotation of the flywheel itself needs to spend some energy. But, if the air is exhausted around the flywheel, its losses will immediately fall by a hundredfold - the supports or bearings "take" quite a bit of their rotation. You can put instead of the usual magnetic bearings. Then the loss of rotation of the flywheel will be almost eliminated. Being overclocked, such a flywheel before its complete stop will rotate for months, and even years. The larger the flywheel, the more it will rotate. The large flywheel - the Earth - has been spinning for about 4 million years, and during this time has slowed down only by 3 times, although the losses, by our standards, are colossal. The moon "brakes" the Earth in its rotation by the tides and ebbs of all the oceans, and these are the powers many times exceeding the powers produced by mankind artificially.

So, we increase the kinetic energy of our steel flywheel. But, at certain turns the flywheel is broken into fragments and it is impossible to accumulate kinetic energy again!..

What prevented to accumulate kinetic energy and disperse the flywheel yet? Yes, the same inertia. Each part of the flywheel tends to move rectilinearly, and here it is "forced" to turn off the straight path, but more and more often. The strength of the flywheel metal interferes with the flight of these particles, but when the mechanical stresses become extremely large, the metal does not stand up and breaks.

The kinetic energy at the same time the wheel has accumulated as much as it did and contained fragments that scattered with speed. Is this a lot or a little? It turns out that this is almost the same as for car batteries, and tens of times more than the best capacitors. But we must remember that this energy is accumulated at the time of the gap, which can not be tolerated! Therefore, this indicator should be reduced at least 2-3 times. It turns out a little.

And if you take the material more steel? Yes, and easier, less density, to reduce the voltage? Then you can expect to accumulate large values of the kinetic energy. But are there any such materials? There are many such materials in modern technology: steel wire, amorphous metal tape (metglass), carbon fibers, Kevlar fibers, and "diamond" fibers.

But flywheels are usually cast or forged. Can I make them from such fibers or tapes? It turns out that it is possible, and in some cases it is even easier than casting or forging. These fibers and tapes need to be wound on the center or hub of the flywheel, almost the same way as we wind the threads onto the reel. Only this center must have the necessary elasticity, the winding should take place with a certain tightness, and the last turn must not be outside but inside the winding. And if this is all done, you can get a super-power flywheel, called a super-flywheel, which will be torn apart safely, without shrapnel.

Here's how and what is best to accumulate kinetic energy, and energy in general. The fact is that progress in creating super-strong materials does not stand still, and the creation of so-called "close-packed" materials of fantastic strength and density has already been predicted. A flywheel of such materials can, for example, serve as an engine, i.e., supply the car with the energy of its entire lifetime, being untwisted yet on the conveyor!