IF YOU use wireless internet, you may have noticed that there is a lot of it around.

Almost every square metre of space in cities is covered by multiple wifi router ranges.

The proliferation of overlapping, jealously password-protected wifi provision rakes in profits for internet companies that are able to charge several separate people who could instead share the cost and use of a single wifi router.

This failure of the market to produce the most efficient and cheap solution will not surprise anyone.

The energy use by wifi networks is relatively low compared to powering a screen or a kettle, but it is not negligible, especially because the networks function 24 hours a day.

Estimates vary, but an online energy calculator suggests a router might use about 10 per cent of the energy of a laptop, but would be on for a lot longer.

The energy use occurs because wifi routers emit radio waves constantly in order to allow the connection of devices to the internet.

A device, once connected, emits its own radio waves in order to send and receive data from the router.

We are bathed in a rich soup of these waves. Every wave-emitting device releases signals in all directions (like a light bulb, rather than a laser pointer), so that the space around us is full of electromagnetic vibrations carrying information backwards and forwards through the air, the walls and our bodies.

At first glance that’s surprising, but there’s no reason that it should be alarming. There has been no evidence of harm by exposure to these waves.

Visible light is also an electromagnetic wave. The constant movement of light through the air doesn’t normally bother us, nor are we usually concerned about light from lightbulbs hitting our bodies.

The difference between light and the waves that are used for wireless internet is the length of the wave and how many waves pass through a point in space in one second.

Light waves are much more energetic than wifi waves and the lengths of the waves are much shorter, so many more travel through space in any given time. 

The only known risk posed by electromagnetism is the result of too much energy hitting our cells and causing damage.

This is what happens when UV light, which is even higher energy than visible light, lands on the skin.

It’s the high energy of the light that damages the structures in skin cells and causes sunburn.

If light reaches all the way into the cell and damages the DNA in the nucleus, UV light can also cause skin cancer.

Wifi waves are a hundred thousand times less energetic and therefore less damaging than visible light, so there should be no cause for alarm.

Nevertheless, wifi waves are fascinating. We can’t see or feel them and without devices to scan for them, we would have no idea that they are there.

Yet their capacity to transfer data is astonishing. The length of a wifi wave is either 6cm or 12cm depending on the system used, meaning that the data that you are transferring as you download files or stream videos is passing through the space around you via a wave on a scale that you can imagine holding.

Of course, you can’t “hold a wave,” but the length of these waves is what makes them so effective in the home.

At short to medium range, they pass through normal objects and walls with next to no disturbance, thanks in part to the fact that many objects are smaller than the waves themselves.

In order to read the information in wifi waves engineers have designed antennae to record and decode them.

The miniaturisation of electronics has required strategies to be devised to produce antennae that are much smaller than the waves they capture.

The size of the wave somewhat defines the size that is needed for the antenna to be effective.

The simplest antennae work by comparing the magnetic field along the length of a metal wire that’s similar to the length of the wave. 

Electromagnetic waves are also used to transmit data from radio stations and walkie-talkies.

The lengths of waves used for radio stations are around three metres, much bigger than wifi waves. That’s why you need to plug in a pair of headphones to listen to FM radio on your phone.

The wire of the headphones is required in order to act as a long enough antenna to “catch the waves” and decode the signal carrying the radio station.

The greater length of radio-carrying waves makes them even more effective at travelling through buildings, trees and rock, although with enough stuff in the way, for example in a tunnel or a thick metal box, the waves can be totally blocked.

In an age when we desperately need to find ways to reduce energy consumption and waste, the tiny but persistent drip of energy from every router and radio wave transmitter into the world suggests the potential for change.

Instead of reading and decoding the data contained in radio signals like a regular antenna, what if a device could simply absorb the waves emitted by radio towers and devices and harvest the energy?

This is the vision that has driven scientists in Florida to design a proof-of-principle device that does exactly that.

The device is 16cm square, and currently capable of powering an LED by scavenging energy from a call on a mobile phone.

The challenge will be to miniaturise the system, and enhance its efficiency and range.

By doing that, it might be possible to mop up some of the waste energy and use it to generate power that can be used by other wireless devices.

Although the bigger solutions to generation of sustainable energy and reduction of its waste will be in more revolutionary technologies, this approach to the reduction of profligate energy waste is a step in the right direction.