POWER – 지속적인 광학 무선 에너지 릴레이

무선 전력

Since the invention of electrical devices, the idea of wireless energy transmission has been the end goal of the industry. This would reduce the need for expensive and often fragile infrastructure like power cables.

Wireless energy transmission will also be needed for space-based solar energy, which is most likely the way to truly power the whole world with renewable energy, as we described in “무한한 청정 에너지를 위한 우주 기반 에너지 솔루션”.

This has, however, been a difficult task so far, with long-distance wireless energy transmission technology still in its infancy.

It has been changing thanks to a new project by DARPA (Defense Advanced Research Projects Agency), the intelligence-scientific-military agency in charge of exploring and testing groundbreaking new technology. Called POWER (Persistent Optical Wireless Energy Relay), this project has achieved power delivery 8.6 kilometers (5.3 miles) away.

“우리는 전력과 거리 측면에서 이전에 보고된 모든 광학 전력 빔 시연을 확실히 뛰어넘었다는 것은 의심의 여지가 없습니다,”
Paul Jaffe – POWER 프로그램 매니저

This is just the first step of a technology that could radically change how energy is transmitted, for both civilian and military applications.

무선 에너지 전송

유도

Wireless energy transfer is becoming a relatively well-mastered technology, but only for short distances. This is usually done with induction, using a magnetic field to transfer the energy and see it converted back into an electrical current.

출처: How2Electronics

The problem is that this sort of energy transmission only works over short distances, ideally less than a meter, which makes it unusable for any long-distance energy transmission.

레이저

To transmit energy over long distances in the air, lasers are a more likely candidate, as coherent light can travel long distances with minimal loss, at least as long as the weather conditions allow.

It is expected that laser-based energy transmission is at its least efficient when close to the ground, as the atmosphere is thicker at this altitude. Still, this is the condition under which the PRAD (POWER Receiver Array Demo) device was tested.

“지면에 비해 직접 위로나 아래로 전력 빔을 보내는 것이 훨씬 쉽습니다. 왜냐하면 통과해야 할 대기가 훨씬 적기 때문입니다. PRAD의 경우, 우리는 대기 효과의 최대 영향을 받는 상황에서 테스트하고자 했습니다.”
Paul Jaffe – POWER 프로그램 매니저

Maybe more importantly, laser light can also relatively easily be reflected by mirrors, allowing for a multi-point relay with minimal losses. This can help transmit energy over even longer distances and bypass obstacles like mountain ranges or the Earth’s curvature, thanks to flying relays.

출처: DARPA

POWER 및 PRAD의 초기 결과

The researcher team recorded more than 800 watts of power delivered during a 30-second transmission from a laser 8.6 kilometers (5.3 miles) away.

Over the course of the test campaign, more than a megajoule of energy was transferred. This is still far from the equivalent of transferring liquid fuel like oil, as 1 gallon of diesel is worth 146 megajoules.

Still, it is a great progress over previous attempts of wireless energy transmission, in both distance and total power, as the previous best results were only 500 watts and a maximum of 1.7 kilometers.

출처: DARPA

혁신적인 수신기

Creating a powerful energy beam with lasers is a well-known technology. Sending that energy through the air, or even reflecting it with a mirror or optical systems, is also a relatively easy task.

Converting the laser’s light back into usable electric power is the difficult part, especially as it needs to limit losses as much as possible.

PRAD used a new receiver technology with a compact aperture for the laser beam to shine into, ensuring very little light escapes once it has entered the receiver.

출처: DARPA

Inside the receiver, a parabolic mirror spread out the laser in a wider cone, reflecting the laser beam onto dozens of photovoltaic cells (solar panels), turning back the light into power.

The receiver was designed by Teravec Technologies, with support from Packet Digital and the Rochester Institute of Technology.

무선 전력의 군사 및 민간 적용

군사

As it stands, the technology’s applications seem to be primarily military-related, hence the involvement of DARPA. It is because military operations might see a lot of circumstances where carrying energy to a given location can be dangerous or even impossible.

These tests mark an important step towards the POWER program’s long-term goal of being able to instantly beam power from a location where it can be easily generated to wherever it’s needed, opening a novel design space for platform capabilities unbounded by fuel limitations.

The technology is scalable to higher power levels and can be integrated into different platforms, such as unmanned aerial vehicles (UAVs), to support the long-term needs of the POWER program.

Another reason for the primarily military focus is that the energy efficiency of the whole system is still low.

The key part is that the transformation of electricity into a laser beam is not without loss, with conversion usually around 50% efficiency, potentially up to 75% in very low temperatures.

Turning that laser back into power will also likely be below 50% efficiency, even with very high-performance solar cells.

So while it can make sense to keep drones flying or supply military equipment, systems like POWER will still waste 50-80% of the initial energy.

In this test, where distance was the focus, and not efficiency, the team measured more than 20% efficiency from the optical power out of the laser to the electrical power out of the receiver at shorter distances.

This sort of inefficiency is not a deal-breaker for the military, as the current alternatives are not much better.

“U.S. Air Force Col. Paul Calhoun noted that he used to fly tankers of fuel to destinations, and in the process burned hundreds of thousands of pounds of fuel to deliver thousands of pounds of fuel.

So clearly our existing paradigm is extraordinarily inefficient.

Paul Jaffe – POWER 프로그램 매니저

So if air refueling is only 1% efficient today, the 20% efficiency of POWER is certainly an improvement.

에너지 전송

Due to these limitations, and also the total volume of energy POWER can transfer, this method is unlikely to replace high-tension power lines any time soon.

This concept could, however, be deployed in another way to power the energy grid. The energy loss is only a problem if the origin point is not so energy-rich that it does not matter.

If we can master the mass production and deployment of solar energy satellites, the 24/7 production of energy from the solar rays in orbit, unimpeded by the atmosphere, would be an order of magnitude more efficient than solar panels on the surface. In that context, the beaming back of energy, either with lasers or microwaves, could still be efficient enough to be economically viable.

POWER 2단계 및 3단계

Now that the power transmission prototype has proved viable, practical tests are next.

Phase 2 will integrate the relay technologies into pods carried on conventional aircraft, culminating in low-power airborne tests.

In a later and final phase 3, the goal is for a laser in a ground facility to beam 10 kilowatts of power to a ground receiver horizontally 200 kilometers away using three aerial relays.

This would demonstrate that we will have a means to deliver energy over very long distances to places that would otherwise be difficult to deliver it to.

Paul Jaffe – POWER 프로그램 매니저

결론

POWER has achieved a level of power transfer efficiency that makes it a viable option to transfer energy to military equipment over long distances, making it more efficient than existing mid-air refueling options.

It will be a good option for airborne military equipment smaller than planes, especially drones, which are quickly becoming a very important part of the military arsenals all over the world, as demonstrated by the war in Ukraine.

Supplying land units deployed forward and potentially cut from supply will also benefit from such power transmission, including land-based drones.

This project is not directly going to impact the prospect of orbital solar energy, but it shows that long-distance energy transmission is no longer a pipe dream.

무선 에너지 전송으로 혜택을 받는 드론 제조업체

If wireless energy transmission becomes commonplace in the US military, it will radically increase the utilization of drones, even more than what is currently planned. So the success of the POWER project is likely to benefit the companies already supplying the USA with military drones.

AeroVironment (AVAV ) is at the forefront of the advanced suicide drones already deployed by the US military, the Switchblade loitering ammunition (loitering refers to the ability of the drone/missile to hover in an area for a while, looking for its target, instead of the direct attack mode of a missile).

출처: AeroVironment

AeroVironment is also offering military reconnaissance drones, 2.2kg tactical drones for infantry, the Nano Air Vehicle, small enough to be held in one hand, and high-altitude pseudo-satellite (HAPS) solar gliders.

On the ground, uncrewed ground vehicles (UGVs) are used for demining, removal of IEDs (Improvised Explosive Devices), SWAT operations, and handling of dangerous materials.

출처: AeroVironment

The company even contributed to the Ingenuity Mars helicopter project, something previously believed to be impossible in the rarefied atmosphere of the red planet.

AeroVironment can then integrate all these systems into a coherent AI-enhanced common control, bringing together all the autonomous systems and relevant data.

출처: AeroVironment

The loitering ammunition is the largest segment ($5B Total Addressable Market – TAM) and is growing rapidly. Overall, the company grew its revenues by 40% in 2023 and expects to keep double-digit revenue growth in the fiscal year 2025.

AeroVironment merged in 2024년 11월 with BlueHalo in an all-stock transaction with an enterprise value of approximately $4.1 billion, almost the same market capitalization as AeroVironment’s. AeroVironment’s shareholders now own ~60.5%, and BlueHalo’s shareholders will own ~39.5% of the combined company.

BlueHalo brings to the company complementary defense-related activities:

• 우주 통신.
• 드론에 대한 직접 에너지 무기 및 전자전 시스템.
• 해양 드론.
• 드론 스웜 제어 및 적 스웜 방어를 위한 AI 도구.

The newly merged company is likely to become an increasingly large defense contractor for future military drone swarms.

최신 AeroVironment (AVAV) 주식 뉴스 및 개발