The US successfully transmitted 1.6 kW of electricity wirelessly over a distance of 1km using microwaves

Wireless electricity has been around for a long time. The principle of wireless power transmission is quite simple. The electricity will be converted into microwaves, then focused into a beam and 'shot' to the receiver, a device made from components called rectenna (rectifier antenna). When microwaves are 'fired' and impact the rectenna, the particles will create a DC current.

The NRL team used a 10 GHz microwave beam and set up wireless power transmission tests at two locations: US Army Research Field in Blossom Point, Maryland and HUSIR (Haystack Ultra Wideband Satellite Imaging Radar) at MIT in Massachusetts.

The 10 GHz frequency was chosen because it can transmit in heavy rain conditions but has less than 5% energy loss, and is safe to use for animals or humans.

NRL's wireless power transmission testing in Maryland achieved 60% efficiency. The Massachusetts test achieved lower power than Maryland, but had a higher average power, so it transmitted more energy.

Currently, wireless power transmission technology can be applied by the US Department of Defense to transmit power to soldiers in the field, eliminating the need to transport fuel, which is very vulnerable to attack.

In the future, this technology can be used to transmit electricity on the ground, or from space back to the earth to provide electricity 24/7/365.