Will we transmit energy wirelessly and over long distances?

Periodically, the English press tells us that Tesla - or a glorious unknown American - has just discovered the means of transmitting a significant amount of energy wirelessly and over a long distance. The solution to such a problem would obviously open up to industry and science an absolutely new era and paths so fantastic that no one in the world would be able to calculate the consequences. Just think, a power station emitting electrical waves in all directions; these waves crossing seas and deserts, enclosures, walls and dwellings; each individual equipped with a device capturing these waves, a simple switch to turn and the waves immediately transformed into electric currents operating dynamos ready for all uses: various movements, lighting, heating, in short, everything that allows us, at the Currently, the Electricity fairy, with this difference, however, that none of the new devices would need to be connected to the factory by means of cables or wires, at the very least expensive and unsightly. This is the dream; is it feasible? Let's first see where we are.

Waves and radiation

To make myself better understood, I will allow myself to use a familiar comparison that my readers have already heard. Here is a stone, I throw it into a large basin filled with water; I spent energy, and this energy, which cannot disappear, is immediately transmitted in the form of large concentric undulations. But, note it carefully, this energy, as we move away from the center of shaking, weakens more and more. For what ? Simply because the total sum at the beginning is divided into as many portions as there are molecules affected. It is for a similar reason that the sound emitted by a bell, the light projected by a lamp, weaken with distance. The same is true for a source emitting electric waves: the latter affect increasingly larger spherical surfaces; each point in space thus affected can therefore only receive a tiny part of the energy emitted by the source placed at the center. Physicists and geometers will teach you that in the circumstances, the law of reduction of energy is easy to formulate. Place a square of white paper one meter from a light source; the same paper located two meters away will obviously be less illuminated. In what proportion? Physics will tell you that, in the latter case, the paper being twice as far away, the illumination will be 2 x 2 = 4 times less. The same reasoning is valid for the electric wave. Whatever the power of the device that triggers the wave that causes it, the energy collected at one kilometer will be low, since all of the energy emitted is spread over the surface of a sphere of one kilometer radius. . And it will be quite different for a point located 500 kilometers away. At this last distance, the energy received will be 500 x 500 = 250,000 times lower. If the source is in America, 6,000 kilometers away, we will only collect in France a tiny portion, or the 36 millionth part. And yet, marvelous detail, such is the sensitivity of our current T.S.F stations, that this infinitesimal portion of energy manages to affect them,

Energy sent remotely

— So, you will say, the transmission of energy by wireless is a problem already solved? — But yes, you are absolutely right.

Every time you receive a dispatch from the Eiffel Tower station, you are indeed collecting energy borrowed from the transmitting device, and which has flown through spaces. This observation is not extraordinary: when you heat yourself in the sun, you still benefit from transmitted energy, but, this time, the emitting source is located much further away, and this source must be beautifully powerful since the entire Earth, as we have said, only receives half a billionth part of the heat released by the king star. But, let's come back to our electric waves. A fact, what physicists are currently seeking is not to collect this small portion that we know how to capture, but to store all, or almost all, of the electrical waves caused by the transmitting device.
You are aware that with the help of a magnifying glass or a concave mirror you can concentrate the sun's rays at a point; Wouldn't it be possible to act in a similar way for the energy received wirelessly? Theoretically, the answer is beyond doubt; but practically, the problem becomes more difficult.

The difficulty of the problem

So, indeed. that it holds several tens of thousands of light vibrations in the space of one millimeter, our waves normally used in T.S.F. have a length of 3 or 4 kilometers; therefore, you can see from here the size of the mirrors that would have to be used to concentrate them! The best way would be to use small wavelengths: it is not impossible; we already know how to use electric waves of 250 meters and we can go lower, to 100 meters most certainly, but we would have to get to one or two meters. In these conditions, it would be a game to send waves in such or such direction in the form of a beam, like the light of a lighthouse. Then, no more loss along the way, or, at least, an insignificant loss; and the beam captured on arrival would become susceptible to concentration.

A solution to consider

In what form should the energy thus transmitted be used? Oh ! in many ways; It will be enough for me to give just one example.
Let's run high-frequency alternating currents into a coil, that is to say currents changing direction several thousand times in the interval of a second, and place an iron bar inside the coil. What's going to happen ? We will produce corresponding induction currents in the mass of iron and we will notice that the bar heats up: it is the energy spent which is transformed into heat. Do not cry out; This is not pure theory, and the proof is that this process is currently used in industry for the fusion of metallic masses. With a power of around ten horsepower (approximately 8 kilowatts) and a current of 400,000 periods per second, which corresponds to a wavelength of only 750 meters, you will be able to melt 60 grams of iron in less than a minute. If each of us learned to capture electric waves of the same length, we would be free to repeat the experiment as many times as we liked. at fantastic distances from the emission source
We are not quite there, but you now see in which direction physicists are beginning to move and you understand, this time, that the remote and wireless transmission of energy is far from being a chimera. Believe me, within ten years, perhaps sooner, the problem will be solved.

Abbé TH. MOREUX, Directeur de l'Observatoire de Bourges.