DARPA Shatters Wireless Power Transmission Records, Advances Toward Energy Web Vision

 

Persistent Optical Wireless Energy Relay program achieves 800-watt transmission over 8.6 kilometers, bringing Tesla's century-old dream closer to reality

By Claude Anthropic and Stephen Pendergast
IEEE Spectrum | July 14, 2025

The Defense Advanced Research Projects Agency (DARPA) has achieved a breakthrough in wireless power transmission, setting new records for both power delivery and transmission distance that could revolutionize how energy reaches remote military operations and disaster zones.

In recent tests conducted at the U.S. Army's White Sands Missile Range in New Mexico, DARPA's Persistent Optical Wireless Energy Relay (POWER) program successfully transmitted more than 800 watts of power across 8.6 kilometers (5.3 miles) for 30 seconds using optical laser technology. The achievement represents a quantum leap from previous demonstrations, obliterating earlier records of 230 watts transmitted over 1.7 kilometers.

"It is beyond a doubt that we absolutely obliterated all previously reported optical power beaming demonstrations for power and distance," said Paul Jaffe, POWER program manager at DARPA's Tactical Technology Office, after the results were confirmed.

Breaking the Power-Distance Barrier

The POWER Receiver Array Demo (PRAD) system that achieved this milestone employs a novel receiver design featuring a compact aperture that captures incoming laser light with minimal loss. Inside the spherical receiver, the laser beam strikes a parabolic mirror that reflects the light onto dozens of photovoltaic cells arranged around the device's interior, converting the optical energy back into usable electricity.

System Efficiency and Performance Metrics

The demonstration achieved more than 20 percent efficiency from laser output to electrical power at shorter distances, though DARPA didn't disclose the efficiency at the full 5.3-mile range, where the number is likely lower. This means the 800 watts received was just a slice of the total beam energy fired downrange, with several kilowatts likely transmitted to achieve the 800-watt delivery.

Future receivers would have lighter parts as well as specialized photovoltaic cells optimized for the wavelengths of light being used, which can be more than double or even triple the efficiency of a typical solar cell, according to program manager Jaffe. The current system's rapid three-month development timeline necessitated trade-offs that future designs will address.

The demonstration transferred more than a megajoule of energy over the course of the test campaign. While impressive, the achieved efficiency is still far below the 95% efficiency that most electrical transfer systems have, highlighting the fundamental challenge of wireless power transmission.

Atmospheric Effects and Environmental Challenges

Both the transmitter and receiver were positioned on the ground, requiring the beam to travel through the thickest part of the atmosphere, making the results particularly impressive. "It's a lot easier to send a power beam directly up or down relative to the ground because there is so much less atmosphere to fight through," Jaffe explains. "For PRAD, we wanted to test under the maximum impact of atmospheric effects."

Atmospheric propagation presents multiple challenges for laser power beaming. Atmospheric scattering and absorption can degrade performance, though for many applications the beam has a strong vertical component or operates at reasonable altitude above ground level, either of which reduces atmospheric problems. Water vapor and aerosols absorb and scatter laser energy, with absorption coefficients varying significantly based on humidity and atmospheric conditions.

The choice of testing in New Mexico's high-altitude desert environment, while providing clear atmospheric conditions, may not reflect operational challenges in humid or particulate-rich environments that military forces often encounter.

To commemorate their achievement, the POWER team used some of the wirelessly transmitted energy to make popcorn—a playful homage to the 1985 film "Real Genius," where students thwart a plot to weaponize high-energy lasers.

Three-Phase Vision for Wireless Energy Web

DARPA's POWER program, launched in 2023, envisions a comprehensive wireless energy network that could transform military logistics and humanitarian operations. The program has selected three industry teams—led by RTX Corporation, Draper Laboratory, and BEAM Company—to develop the critical relay technologies needed for this ambitious vision.

Phase One, currently underway, focuses on benchtop demonstrations of relay technologies expected to last 20 months with an optional three-month extension. Phase Two will integrate these relay systems onto conventional aircraft for low-power airborne demonstrations using pod-mounted equipment.

The program's ultimate goal, to be demonstrated in Phase Three, is transmitting 10 kilowatts of optical energy across 200 kilometers using three airborne relay nodes. These relays, potentially carried by high-altitude platforms operating around 60,000 feet, would create an optical backbone for long-range, high-throughput power transmission.

"Each of the selected teams proposed unique technical approaches to the power beaming relay problem, ranging from novel combinations of existing technologies to high-risk, high-reward technological innovations," Jaffe explained.

Military and Humanitarian Applications

The implications of successful wireless power transmission extend far beyond the laboratory. Traditional military supply chains dedicate enormous resources to fuel transport, with soldiers often reduced to manually hauling fuel containers across hostile terrain—a vulnerability that wireless power could eliminate.

For military applications, the technology could enable:

• Extended-range unmanned systems: Drones and other platforms could operate indefinitely without fuel constraints, limited only by mechanical wear
• Resilient forward operating bases: Remote installations could receive power from distant, secure generation facilities
• Rapid disaster response: Emergency operations could be powered without establishing ground infrastructure
• Space-based solar power: Future orbital platforms could beam collected solar energy to Earth-based receivers

Key Technology Partners and System Integration

The record-setting receiver was designed by Teravec Technologies, led by principal investigator Raymond Hoheisel, with support from Packet Digital and the Rochester Institute of Technology. Teravec Technologies specializes in innovative laser power beaming solutions and has been selected by both DARPA and NASA for advanced power beaming receiver development. The company's receiver technology is modular and scalable for 10-100 kW applications, with the current technology demonstrator developed within just three months.

Packet Digital, a battery and power system company, contributed expertise in autonomous systems power management, particularly for unmanned aircraft systems (UAS). The Rochester Institute of Technology provided academic research support for the receiver development.

The broader DARPA-led team brought together industry and government partners, including the U.S. Naval Research Laboratory and the High Energy Laser Systems Test Facility (HELSTF) at the U.S. Army's White Sands Missile Range, where the tests were conducted.

For the program's three-phase development, DARPA has selected industry teams led by RTX Corporation, Draper Laboratory, and BEAM Company to develop the critical relay technologies. Each team proposed unique technical approaches ranging from novel combinations of existing technologies to high-risk, high-reward technological innovations.

Safety and Operational Considerations

High-power laser systems like those used in the POWER program present significant safety challenges that must be addressed for operational deployment. Class 4 lasers, the highest and most dangerous classification, can cause immediate eye damage and present fire hazards if the beam contacts flammable substances.

The system includes built-in safety measures to shut off transmission if anything crosses the beam's path. However, infrared laser beams are invisible to the naked eye, complicating safety protocols. The eye focuses visible and near-infrared light onto the retina, where laser energy can be concentrated to intensities up to 200,000 times higher than at the point where the beam enters the eye.

For operational deployments, protective eyewear and controlled access areas would be essential. The program's emphasis on high-altitude relay operations helps mitigate some safety concerns by keeping high-power beams well above ground level during normal operations.

Technical Challenges and Future Prospects

Despite the recent success, significant technical hurdles remain. The program must address multiple efficiency bottlenecks in the power transmission chain:

Laser Generation Efficiency: Current laser systems typically achieve 20-50% electrical-to-optical conversion efficiency, though fiber lasers can reach up to 75% at very low temperatures.

Atmospheric Transmission: Beam attenuation occurs through several mechanisms:

• Molecular absorption by water vapor (particularly strong at 1.45 μm wavelength)
• Aerosol scattering (Mie scattering) from particles comparable to the laser wavelength
• Rayleigh scattering from air molecules
• Thermal blooming effects at high power densities

Optical-to-Electrical Conversion: The PRAD receiver achieved over 20% efficiency at shorter distances, but specialized photovoltaic cells optimized for specific laser wavelengths can potentially achieve 40-70% efficiency—significantly higher than conventional solar cells' 15-22% efficiency.

Beam Quality Maintenance: The relay systems under development aim to maintain high beam quality through wavefront correction and enable throttleable energy harvesting. Previous strategies required each relay to convert light to electricity and back to light, proving inefficient with multiple conversion losses. The new approach uses optical strategies to route light from relay to relay, avoiding these conversion penalties.

Atmospheric effects cause beam attenuation, particularly in the dense lower atmosphere, which is why the program emphasizes high-altitude relay networks operating around 60,000 feet to minimize atmospheric losses and enhance relay survivability. The recent ground-to-ground demonstration faced maximum atmospheric interference, making the achievement even more impressive.

Industry Response and Next Steps

The record-setting demonstration has already sparked increased industry interest in power beaming technologies. DARPA held an Industry Day on May 29, 2025, to promote partnerships for Phase Two development and attract innovative approaches to integrated relay systems.

The program's success builds on decades of theoretical work dating back to Nikola Tesla's early experiments with wireless power transmission. Modern advances in laser technology, photovoltaics, and beam control have finally made Tesla's century-old vision technically feasible.

Professor Paul Mitcheson from Imperial College London's Control and Power Research Group emphasizes the fundamental difference between power beaming and communications: "In broadcast television or radio, the objective is to propagate the signal as widely as possible. That's exactly what you don't want to do when you're beaming power. The goal is to beam the signal straight into a receiver with as little loss as possible."

With Phase One risk reduction complete, the POWER program now advances toward airborne demonstrations that could prove the viability of wireless energy networks. If successful, the technology could reshape not only military operations but civilian applications ranging from remote area electrification to space-based solar power systems.

The recent achievements represent more than technical milestones—they mark progress toward a future where energy constraints no longer limit the deployment of critical systems in remote or dangerous locations, potentially transforming both defense capabilities and humanitarian response efforts worldwide.

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