POWER – Persistenter Optischer Drahtloser Energie‑Relay

Drahtlose Energie

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.

Drahtlose Energieübertragung wird auch für weltraumgestützte Solarenergie benötigt, die wahrscheinlich der Weg ist, die ganze Welt mit erneuerbarer Energie zu versorgen, wie wir in „Space-Based Energy Solutions For Endless Clean Energy“ beschrieben haben.

Dies war jedoch bisher eine schwierige Aufgabe, da die Technologie der langfristigen drahtlosen Energieübertragung noch in den Kinderschuhen steckt.

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.

“Es besteht kein Zweifel, dass wir alle bisher gemeldeten Demonstrationen optischer Energieübertragung in Bezug auf Leistung und Entfernung vollständig übertroffen haben,”

Paul Jaffe – POWER program manager

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

Drahtlose Energieübertragung

Induktion

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.

Quelle: 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.

Laser

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.

“Es ist viel einfacher, einen Energiestrahl direkt nach oben oder unten relativ zum Boden zu senden, weil dabei viel weniger Atmosphäre zu durchdringen ist. Für PRAD wollten wir unter dem maximalen Einfluss atmosphärischer Effekte testen.”

Paul Jaffe – POWER program manager

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.

Quelle: DARPA

POWER & PRAD’s Erste Ergebnisse

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.

Dennoch ist es ein großer Fortschritt gegenüber früheren Versuchen der drahtlosen Energieübertragung, sowohl in Bezug auf die Entfernung als auch die Gesamtleistung, da die bisherigen besten Ergebnisse nur 500 Watt und maximal 1,7 Kilometer betrugen.

Quelle: DARPA

Innovativer Empfänger

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.

Quelle: 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.

Militärische und zivile Anwendungen von drahtloser Energie

Militär

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.

Ein weiterer Grund für den primär militärischen Fokus ist, dass die Energieeffizienz des Gesamtsystems noch niedrig ist.

Der entscheidende Teil ist, dass die Umwandlung von Strom in einen Laserstrahl nicht verlustfrei ist, wobei die Umwandlung üblicherweise etwa 50 % Effizienz beträgt und bei sehr niedrigen Temperaturen bis zu 75 % erreichen kann.

Die Rückumwandlung dieses Lasers in Energie wird wahrscheinlich ebenfalls unter 50 % Effizienz liegen, selbst bei sehr leistungsstarken Solarzellen.

Während es also sinnvoll sein kann, Drohnen in Betrieb zu halten oder militärische Ausrüstung zu versorgen, werden Systeme wie POWER weiterhin 50–80 % der ursprünglichen Energie verschwenden.

In diesem Test, bei dem die Entfernung im Vordergrund stand und nicht die Effizienz, maß das Team eine Effizienz von über 20 % vom optischen Ausgangsleistung des Lasers bis zur elektrischen Leistung des Empfängers bei kürzeren Distanzen.

Diese Art von Ineffizienz ist für das Militär kein Ausschlusskriterium, da die derzeitigen Alternativen nicht viel besser sind.

„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 program manager

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

Energieübertragung

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 Phase 2 & 3

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 program manager

Fazit

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.

Drohnenhersteller, die von drahtloser Energieübertragung profitieren

AeroVironment Inc.

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 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).

Quelle: 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.

Quelle: 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.

Quelle: 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 November 2024 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:

• Weltraumkommunikation.
• Direktenergie‑Waffen und elektronische Kriegssysteme gegen Drohnen.
• Maritime Drohnen.
• KI‑Werkzeuge für die Steuerung von Drohnenschwärmen und die Abwehr feindlicher Schwärme.

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

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