Wireless power transfer (WPT) or wireless energy transmission is the transmission of electrical energy from a power source to a consuming device, without the use of discrete man-made conductors. WPT use wireless transmitter that uses any of time-varying electric, magnetic, or electromagnetic fields to convey energy to one or wore receivers, where it is converted back to an electrical current and then used.
Wireless power techniques fall into two categories, non-radiative and radiative. In non-radiative techniques, power is typically transferred by magnetic fields using inductive coupling between coils of wire. A current focus is to develop wireless systems to charge mobile and handheld computing devices such as cellphones, digital music players and portable computers without being tethered to a wall plug. Power may also be transferred by electric fields using capacitive coupling between metal electrodes. In radiative far-field techniques, also called power beaming, power is transferred by beams of electromagnetic radiation, like microwaves or laser beams.
WPT has the unique potential to transform war fighting of the future and alleviate the battlefield battery burden for both soldiers and manned and unmanned vehicles on land, air, and undersea. QinetiQ’s Talon robots that were deployed in Afghanistan automatically recharged their batteries when they were docked to an armored vehicle.
Other recent examples are charging of Soldier’s central battery from vehicle seat back as they sit in vehicles, charging of handheld devices through vests, powering helmet-mounted devices through Soldier vest-to-helmet WPT, Soldier helmet-to-goggle WPT to power devices such as night vision, radio devices and defog optics.
In the future advancements in wireless energy transfer will enable distribution of power amongst power sources, multimodal energy harvesters, and loads to occur wirelessly on the Soldier as a platform, so that all carried equipment will be powered and ready for operation at all times without thought to replacing individual equipment power sources.
As a long term goal, the Army is looking to supply troops remotely using wireless systems that could transfer power from a drone to solar panels or other devices that soldiers could plug into on the battlefield, officials said.
US Navy developing undersea wireless technology to recharge UUVs
U.S. Navy started making a big push into unmanned underwater vehicles for a variety of missions, including reconnaissance, mine hunting, ocean floor mapping, and anti-submarine warfare. The future trend is to use electric propulsion as it is more efficient and stealthy. However one of the challenges is of charging them, they need to return to base just so a human can plug it into a charging station.
Electrically powered, they are quiet and can travel great distances from their mother ship. The problem: It’s hard for a floating robot to plug itself into a charging station at sea. To overcome this challenge, the US Navy is now developing methods to recharge underwater unmanned vehicles (UUVs) with the support of undersea wireless technology, in a bid to reduce time between missions and enhance overall utility. The underwater energy transfer programme was performed using data that is transferred wirelessly underwater using underwater optical communications system.
“This type of technology is going to widen the array of missions the Navy can use UUVs for. Having a UUV that can travel long distances gathering intel from ports and areas of the world our surface ships and underwater craft typically can’t go is going to increase the effectiveness of them,” said Dr. Graham Sanborn, Engineer at SSC Pacific. “It’s also going to make missions safer, because service members will no longer need to accompany the machine.”
“Underwater data and energy transfer are expected to multiply the effectiveness of Navy-operated UUVs and other unmanned platforms by providing a vehicle-agnostic method for autonomous underwater energy charging,” said Alex Askari, Naval Surface Warfare Center, Carderock Division (NSWCCD) technical lead.
Carderock Division’s developed technology enables power transmission between underwater systems, such as UUVs. During the main demonstration, the team was successful in transferring power wirelessly from an underwater docking station to a MARV UUV section, and ultimately to the UUV’s battery, which was charged at 2 kilowatts while submerged. The Mid-sized Autonomous Research Vehicle (MARV) UUV is 16.5 feet long and just slightly more than one foot in diameter.
WiTricity engineers have also demonstrated the ability to wirelessly transfer several hundred watts of power through seawater. WiTricity envisions UUVs being recharged simply by floating alongside a dock, larger vessel, or other power source, eliminating the need for tight mechanical coupling and allowing power to be transferred underwater safely, reliably, and efficiently.
A primary obstacle is the difference in conductivity between air and seawater. For example, the technology being developed by the team at SSC Pacific must take into account the fact that seawater starts becoming less conductive at a frequency of 20kHz, according to research published by the Naval Surface Warfare Center Carderock Division.
An additional component of SSC Pacific’s research is developing chargers that are standardized across multiple UUVs. “Currently if the Navy buys one underwater vehicle and some sort of charger it will only work with that brand or that particular type,” explained Dr. Alex Phipps, chief of the advanced integrated circuit technology branch at SSC Pacific. “What we aim to do is capture the common elements that could be reused for multiple vehicles and create a standard that we can give to industry so that anybody that wants to sell a vehicle and work with the Navy can conform to that standard and there’s interoperability across the fleet.”
DHPC Receives Army SBIR Award for Laser-Based Wireless Power Transfer
On May 10, 2017, DHPC has been awarded the ARMY SBIR Phase II contract titled “Laser-Based Wireless Power Transfer”. The objective of this SBIR Phase II is to develop an advanced and safe laser-based wireless power transmission (LBWPT) system capable of beaming laser power over up to several kilometers to a moving platform from ground, fixed or mobile platforms, or from a moving platform to ground. The developed system will be highly reliable and affordable, with additional emphasis on high efficiency and low SWaPC.
Successful development of the LBWPT system will be able to significantly extend the operational availability of a variety of autonomously operating devices and sensors for military and commercial applications, including robotic systems, unmanned aerial systems (UASs), surveillance systems, devices for remote chemical and biological detection, as well as free-space communications systems.
Our innovative development will also reduce warfighters exposure to enemy forces, as well as reduce the risk of uncovering the locations of emplaced powered devices and sensors. LBWPT development may also reduce the on-board battery weight of electrically powered systems, resulting in increased useful payload.
In addition, the LBWPT system will provide a unique capability of remotely supplying power to contaminated sites or inaccessible areas that pose a significant personnel threat, such as nuclear power stations and chemical plants destroyed by natural disasters, such as earthquakes or tsunami, or by actions of terrorists or enemy forces.
DHPC will build a prototype system capable of establishing and maintaining power transfer to a moving receiver. The system’s overall DC source to DC conversion efficiency is expected to reach 20% or better.
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