# When will electricity become free and wireless?

Free: Never.

Generating electricity costs money.This will not change in the future. So why should the people who make the electricity at a cost give it to you?

Wireless: In the spirit of Tesla, can be received by anyone everywhere?Without a new genius: Never. And I doubt very much that such a genius will ever come.

The bitter truth about electromagnetic waves: they spread evenly in ALL directions.This has a few unpleasant effects:

Let’s assume you’re setting up an “energy transmitter” in your apartment to wirelessly power your phone throughout the apartment.

Such a mobile phone battery typically has an energy content of 5 Wh and lasts for 10 hours.This means a power consumption of your mobile phone of approx. 0.5 W. If you now want to operate your mobile phone at home and want to charge your battery in 10 hours at the same time, then your power transmitter must get about 1 W of electrical energy to your phone.

It should be obvious that your mobile phone has only a limited area available for reception, e.g. 70 mm x 140 mm = 9800 mm2 or 0.0098 m2. However, this area can only be used 100% if the largest area of your mobile phone is directly aligned with the energy transmitter, which is unlikely.Let’s calculate generously with 50%, then your mobile phone has a reception area of approx. 0.0049 m2.

Nothing in this world is perfect – this also applies to the energy receivers of your mobile phone.We would like to generously assume that this 50% of the energy that applies to the receiver antennas also absorbs and can be used for the operation and charging of the battery.

Now you are not always right next to the energy transmitter (then you could take a cable :-)) but you will be moving through the whole apartment.I don’t think it’s an exaggeration that a distance of 3 meters can be achieved.

Now we have all the data together to answer the following question:

How much energy does a transmitter have to emit in order to be able to deliver an output of 1 W for a receiver at a distance of 3 meters with a receiving area of 0.0049 m2 and a reception efficiency of 50%.

I think I have already mentioned that a transmitter of electrical energy emits it evenly in all directions.This means that the transmitter distributes the energy evenly on a ball shell around the transmitter. So we need the surface of a ball shell with a radius of 3 meters.

The formula for the surface of a sphere: [mathA = 4-pi-r-2-[/math.If we insert our 3 meters into this formula, then we come to a surface of 113,0973 m2.

If we now calculate the ratio of the sphere surface to the receiving surface of your mobile phone: [math-frac-113,0973 m-2-0,0049 m-2= 23081,0889[/math), then we know how much more the energy transmitter needs to emit.

Now we only have to multiply the factor 23081.0089 by the 1 W that we want in the mobile phone you want to have again with the factor 2, because we have assumed a reception efficiency of 50% and we get as a result:

46162,1778 W

Wow!Almost 50000 W! Just wow.

So that’s not how it works.What if we shorten the distance? With each halving of the distance, we only need a quarter of the power:

1.5 m: 11540,5444 W

0.75 m : 2885,1316 W

37.5 cm: 721.2840 W

18.75 cm: 180.3210 W

9.375 cm: 45.0803 W

4.6875 cm: 11.2701 W

Strangely, we have hardly reached halfway manageable power, we are moving at the distance on an order of magnitude as it is supported by current wireless charging stations.Really weird.

On the other hand, if we were to set up a transmitter mast every 100 m in the inner cities, each transmitter would have to emit about 12 MW of power.To cover 1 km2, it would then need about 1.2 GW in power or a large nuclear power plant (how was that for free with electricity?). For this, such a solution could of course supply all mobile phones in the reception area and not just yours.

Another solution would be to bundle the radiated performance.You can do this, but the antenna becomes very complex. Over a distance of a few kilometers in the microwave area, this has already been done experimentally and works quite well – with antenna fields of several square meters, which then have to be aligned exactly with each other.

A comparatively simpler solution would be lasers.These are easy to obtain in the required power range (below 10 W) as a semiconductor laser.

But everyone should be able to think for themselves the disadvantages of such a directed solution:

As soon as the target moves, the transmitter must be tracked.This means that the transmitter must constantly know with an extremely high accuracy where the receiver is located in order to be able to radiate the energy there. The transmitter must then also be able to align the laser precisely. This is far from easy from the mechanics alone.

Everyone should know that even simple laser pointers with more than 5 mW are considered so dangerous for the retina that they can only be operated with goggles.Stupid that.

No matter what frequency range you search for, a laser with 2 W is always dangerous for anyone who comes between you and your energy transmitter.In case of doubt, that’s also you. There is a U-company that works on something like this and claims to have it under control up to about 1 W (which supposedly switch off immediately when something gets in the way) but also a 1 W infrared laser like the one using it would be a little too dangerous for me in case of error.

So I do not see a wireless energy supply for the foreseeable future.