If you’ve ever stood on the tarmac, staring up at a commercial jet idling before its departure, you’ve likely felt that quiet mix of awe and concern—wonder at the engineering that moves hundreds of people across continents, and worry about the carbon emissions that come with that power. For my team at the clean-energy engine supply firm, that’s not just a feeling—it’s the core of what we build for our clients. For years, airlines, aircraft manufacturers, and regulators have talked about switching from fossil-fuel gas turbines to clean-energy engines, and while progress has been made, there are still technical barriers holding the industry back. As someone who’s spent the last 12 years designing, testing, and refining low-emission aviation engines, I’ve sat in countless design meetings with Boeing, Airbus, and regional carrier engineering teams, and I’ve seen these challenges up close. Let’s break down the biggest ones, no jargon required, from the perspective of someone who’s in the engine bay every day. Clean-energy Engine
First up, energy density. This is the single biggest technical hurdle we face, and it’s non-negotiable. Gasoline and jet fuel have an energy density of roughly 12,000 watt-hours per kilogram (Wh/kg) for jet-A fuel. The most advanced lithium-ion batteries used in electric vehicles max out around 280 Wh/kg, and even the next-generation solid-state batteries we’re testing only hit about 450 Wh/kg in lab settings. That might sound like a big jump, but compared to jet fuel, it’s a drop in the bucket. Let’s put that in concrete terms: a 737 MAX uses roughly 18,000 kilograms of jet fuel for a transatlantic flight from New York to London. To replace that with current battery tech, you’d need almost 80 times more battery mass than the fuel. That extra weight isn’t just a number—it changes everything about how an airplane flies. More weight means more drag, which means you need even more power to get off the ground, creating a vicious cycle. We’ve tested a 40-seat regional turboprop with our hydrogen fuel cell engines, and even there, the energy density of hydrogen (when stored as a cryogenic liquid) is about 33,000 Wh/kg—higher than jet fuel, right? Wait, no—wait, that’s the energy content of hydrogen itself, but when you store it as a super-cold liquid (to keep it dense enough for flight), you have to add the weight of the insulated tanks and the cooling systems, and suddenly that number drops to around 3,000 Wh/kg, still way lower than jet fuel. It’s a trick we haven’t fully cracked yet: how to store clean energy without weighing down the plane so much that it’s not viable for long-haul flights.
Next, thermal management and reliability at altitude. Aviation engines operate in some of the harshest conditions on Earth: at 35,000 feet, temperatures drop to -40°C, air pressure is a quarter of what it is at sea level, and there’s constant vibration from takeoffs, turbulence, and engine rotation. For our clean-energy engines, whether they run on hydrogen or e-kerosene, heat is a constant problem. Traditional gas turbines burn fuel at thousands of degrees, and they have decades of design experience to handle that heat with air cooling and specialized ceramic coatings. Our hydrogen engines, by contrast, burn fuel at an even higher temperature (hydrogen burns hotter than jet fuel) which sounds like a good thing for efficiency, but it means the metal parts of the engine are getting hotter, and we have to cool them without adding extra weight or using too much power. Also, at high altitude, the air is thin, so combustion is less stable. If the fuel-air mix isn’t exactly right, you get incomplete burning, which wastes fuel and creates more emissions—something we’re trying to eliminate entirely. We tested a prototype hydrogen engine last year in a wind tunnel at sea level, and it ran perfectly, but when we took it up to simulated 35,000 feet, the flame would flicker and sometimes go out entirely. That’s a safety issue airlines can’t accept. We’ve spent months redesigning the fuel injectors to create a more stable flame at low pressure, but we’re still tuning the system to be reliable for thousands of flight hours, not just a handful of test runs.
Then there’s the challenge of power output matching. Large commercial airplanes need enormous thrust: a 777 uses two engines that each produce around 110,000 pounds of thrust at takeoff, enough to power 300+ passengers across the Pacific. Our clean-energy engines can match that power for short periods, but maintaining that level of thrust during long flights, especially in bad weather, is hard. For electric engines, scaling up power means adding more motors or larger motors, but larger motors add more weight and create more thermal issues. For hydrogen engines, the problem is storage: if you need 110,000 pounds of thrust, you need a huge amount of hydrogen, which takes up more space on the plane than fuel tanks. Airlines can’t just carve out the cargo hold for fuel anymore—they need space for passengers, baggage, and freight to make money. We’ve worked with a regional carrier to build a 10-seat plane with our electric engines that works for short flights (under 1 hour), but scaling that up to a 200-seat plane that flies 5 hours is still a gap. It’s not just about making the engine powerful enough; it’s about integrating that power into the plane’s design without sacrificing functionality.
Another barrier is materials compatibility, specifically with hydrogen. Hydrogen is a tiny molecule, and it has a nasty habit of leaking through metal, a phenomenon called hydrogen embrittlement. Over time, hydrogen weakens the structure of steel and aluminum, making the engine parts more likely to crack or fail. That’s a huge safety risk. Traditional jet engines use steel alloys and aluminum parts that have worked for decades, but they can’t handle long-term exposure to hydrogen. We’ve tested different materials: titanium alloys, specialized stainless steels, even composite materials like carbon fiber, but each has tradeoffs. Titanium is strong, but it’s very heavy, which adds to the weight problem we already have. Carbon fiber is light, but it’s not as good at handling the high temperatures our engines produce, and it can degrade over time from constant exposure to fuel. We’re currently testing a new nickel-chromium alloy that we think can resist hydrogen embrittlement, but it’s expensive, and mass production would mean higher costs for airlines. Right now, our clean-energy engines cost about 20% more to build than traditional gas turbines, and that extra cost gets passed on to customers. Airlines operate on thin margins—ticket prices are already tight, and small carriers can’t absorb those extra costs, especially when they’re still recovering from the pandemic. We need to bring that cost down, but developing new materials and scaling up production takes time, and there’s no easy fix there.
Wait, let’s not forget about infrastructure compatibility. Even if we solve all the technical problems with the engine itself, we need a way to refuel or recharge planes quickly at airports around the world. For jet fuel, there’s a global network of pipelines, storage tanks, and fueling trucks that’s been in place for 70 years. For clean fuels like green hydrogen or e-kerosene, that network doesn’t exist. At most airports, there are only a handful of places to refuel a hydrogen-powered plane, and it takes much longer to fuel a plane with hydrogen than with jet fuel—about 2 hours for a wide-body, compared to 45 minutes for jet fuel. That means planes spend less time flying and more time sitting on the tarmac, which hurts airline productivity. We’ve been working with airport operators to design faster fueling systems, but again, that’s another layer of technical and logistical work that goes beyond the engine itself. As an engine supplier, we don’t control airport infrastructure, but we have to design our engines to work with existing (or upcoming) infrastructure as much as possible, which adds more constraints to our design process.
I know all this might sound like we’re a long way from replacing fossil-fuel engines, but let me be clear: we’re making progress, and it’s tangible. Last year, we partnered with a major European airline to test our hydrogen engine on a single-engine regional plane, and it completed 12 successful test flights over the English Channel. We didn’t carry passengers, but the engine ran smoothly at altitude, and we gathered data that’s helped us fix the flame stability issue we were seeing earlier. We’re also working with a group of battery scientists to develop a new solid-state battery with an energy density of 800 Wh/kg, which would be enough to make short-haul electric flights viable in the next 5 years.
As a clean-energy engine supplier, our goal isn’t just to build a better engine—it’s to solve these problems, one technical hurdle at a time. We’re not just a vendor to airlines; we’re a partner, working with them, aircraft manufacturers, and regulators to make sustainable aviation a reality. If you’re an airline, aircraft manufacturer, or operator looking to transition to clean energy and want to discuss how our engines can fit your fleet, I’d invite you to reach out to our team for a confidential consultation. We’ve spent years refining our technology, and we’re ready to help you navigate the technical challenges that come with switching to clean energy.
Open Frame Gas Generator Set References
- International Civil Aviation Organization (ICAO). (2023). Sustainable Aviation Fuels and Technology Roadmap.
- U.S. Department of Energy. (2022). Advanced Aviation Energy Storage Report.
- Airbus. (2021). ZEROe Hydrogen Aircraft Concept Technical Overview.
- Society of Automotive Engineers (SAE). (2023). Hydrogen Embrittlement in Aerospace Engines: Materials and Design Guidelines.
- International Air Transport Association (IATA). (2022). Aviation Carbon Emissions and Technical Solutions Report.
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