Copyright © 2022 ZeroAvia, Inc.
Amid a major shift in geopolitical dynamics, armed forces are seeking to bolster defense spending, more rapidly pull through innovative and disruptive technologies to adoption, and thus gain strategic advantage over adversaries. At the forefront are technologies such as autonomy, AI, unmanned aerial vehicles, directed energy and advanced materials, all expected to have profound effects on managing the threat landscape.
Fundamental to the deployment of many of these technological innovations are increased computing power and connectivity, driving also a massive increase in the requirement for electrical power. Existing conflicts have begun to show the limitations of batteries in delivering this electrical power in the UAV use case with drone range even determining the proximity of front lines and the size of gray zones between forces.
In tandem, there has been growing interest in hydrogen for defense in recent years, offering strategic and operational advantages across air, land and sea.
This blog series is based on our Hydrogen in Defense white paper, which examines the transformative potential of hydrogen and fuel cell technologies in defense applications and highlights hydrogen technologies’ unique advantages in energy density, stealth, operational flexibility, reduced maintenance cost, and tactical portability.
Hydrogen can support extended defense mission endurance, reduce logistical vulnerabilities, and enable energy independence in contested environments and nation states across the world are testing technologies to explore impacts in the following areas:
Hydrogen fuel cells offer significantly longer operational times compared to traditional lithium-ion batteries, and due to predicted improvements in areas such as fuel cell specific power and cryogenic tank mass fraction, can overtime outperform range offered by existing gas turbine powered platforms.
In our white paper, ZeroAvia analyzed a potential retrofit of a representative Class I(d) (small) tactical 100 kg multirotor drone with a hydrogen-electric powertrain (see figure 1).
The results show that even for a gaseous hydrogen storage fuel cell system, the heaviest hydrogen-electric solution available, the story is dramatically different to batteries, with the ability to increase the range and endurance of the system five-fold at half load. A custom designed drone for hydrogen-electric application could significantly outperform this.
Hydrogen systems produce lower thermal and audible signatures than combustion engines, making them ideal for stealth operations. This is especially valuable in expeditionary warfare, where remaining undetected is critical.
In terms of thermal signature, fuel cells operate at much lower temperatures than typical UAV jet engines, with exhausts three times cooler. This has a significant impact on operational safety, as well as design and maintenance, with increased component lives, and wider, more economical material options. The lower temperature would also mean substantially reduced optical distortion (heat haze) around the vehicle that can betray the presence of hardware in the air or on the ground.
Looking at noise, electrical propulsion systems are much quieter than their combustion equivalents. There is a total elimination of jet engine noise, which for some vehicles means reducing noise levels by up to 85%. With around 10 times lower air flow rates than an equivalent jet engine, hydrogen-electric powertrains would have a reduced plume size (affecting IR cross-section) and associated flow noise.
Hydrogen can be produced anywhere water is available, significantly reducing fuel supply chain challenges. The U.S. Naval Research Laboratory has developed portable hydrogen fuel cell systems like the Hydrogen Small Unit Power (H-SUP), which provide lightweight, quiet, and efficient power for Marines in the field. These systems reduce the logistical burden and increase the autonomy of small units.
In 2023, NATO conducted trials at France’s Gergy military site, led by NATO’s Energy Security Center of Excellence (ENSEC), evaluating 400W and 1,000W hydrogen fuel cells paired with advanced battery systems, showing the benefits of hydrogen fuel cells in boosting energy resilience and simplifying logistics.
Hydrogen-powered vehicles can offer extra available electric power to support onboard autonomous systems and GPS-independent navigation, reducing reliance on vulnerable communication links. The ability to provide plentiful onboard power efficiently opens up freedoms for new greenfield capabilities. Constraints on the design of military vehicles and their supporting systems can be stripped away opening up the possibility of major performance advantage against adversaries.
In addition, increased electrical power can enable the removal of traditional hydraulics/pneumatics, saving significant weight and fuel, while onboard liquid hydrogen storage offers the potential for cryogenic heat sink to keep sensitive instrumentation cool. Compact, rugged cryogenic coolers are already in use to cool embedded sensors, thermal imagers, and high-performance electronics in some defense applications.
Hydrogen adoption across certain defense platforms and infrastructure will enhance capability, reduce costs, and strengthen national security in an increasingly complex threat environment. In further blog posts published in the coming weeks we will explore how hydrogen and fuel cell military applications can improve capability across air, land and sea, as well as improving tactical portability and independence of power and fuel provision. In the next instalment, we will look specifically at Unmanned Aerial Vehicles (UAV) implications.
To download the Hydrogen in Defense white paper, please click here.
