US Navy wirelessly beamed 1.6kW of power using microwaves

A team of researchers at the U.S. Naval Research Laboratory (NRL) has successfully demonstrated wireless transmission of power over a distance of one kilometer (0.621 miles), the U.S. Navy said in a press release. 

The idea of beaming energy wireless has been around for decades, but it is gaining steam again as humanity looks to change its ways of harnessing energy. While the concept of setting up solar farms on other planets and beaming back power to the Earth is still far from reality, the U.S. military could ensure energy security for its troops as it looks to cut its dependence on fossil fuels. 

The SCOPE-M Project

With the interest of the U.S. military in mind, the Office of the Undersecretary of Defense for Research and Engineering’s Operational Energy Capability Improvement funded a project at NRL to trial a point-to-point transfer of electrical energy using microwaves and called it "Safe and COntinuous Power bEaming – Microwave (SCOPE-M)". 

Within 12 months of the project, the team of researchers at the NRL demonstrated a terrestrial application of the technology by beaming power at not just one but two locations, one at the U.S. Army Research Field in Maryland, and the other at The Haystack Ultrawideband Satellite Imaging Radar (HUSIR) transmitter at the Massachusetts Institute of Technology (MIT).

Both installations used the 10GigaHertz microwave beam since the technology is well known to be safe for humans, animals, as well as birds and yet inexpensive to operate. 

Paul Jaffe, Power Beaming and Space Solar Lead at the project said that during previous experiments with laser powering, the engineers had to build systems that would stop the beams from transmitting if something crossed their path. However, since the power density in 10 GHz frequency was intrinsically safe, such systems were not needed in the SCOPE-M project. 

How was it done? 

The principle used to transmit electricity is straightforward. Electricity is first converted into microwaves and then transmitted as a tight beam towards the receiver, which is equipped with a rectenna or rectifying antenna. In wireless energy transmission systems, a rectenna is an antenna with a rectifier diode that can convert electromagnetic energy into direct current. 

By installing these systems, the team at NRL was successful in transmitting power wirelessly at both locations. At Maryland, the researchers managed to transmit 1.6kW of energy, well above their target of 60 percent. At MIT, although the team did not manage the same peak power, the average power transmitted was higher, resulting in the delivery of more energy.

"Although SCOPE-M was a terrestrial power beaming link, it was a good proof of concept for a space power beaming link," said Brian Tierney, electronics engineer at the project. "The main benefit of space to Earth power beaming for the DOD is to mitigate the reliance on the fuel supply for troops, which can be vulnerable to attack."