Embracing Liquid Hydrogen for a Zero-Emission Aviation Future

In 2017, AeroDelft embarked on a visionary journey with a singular goal: to fly from Amsterdam to London without emitting a single gram of CO2. This bold aspiration has now evolved into a pioneering project involving AeroDelft and Teesing, leveraging liquid hydrogen to power electric aircraft—a testament to the potential of emission-free aviation.

The Energy Challenge in Aviation

Aviation is a major contributor to global CO2 emissions, driven by the sector’s reliance on high-energy-density fuels like kerosene. Current battery technologies, such as lithium-ion used in electric vehicles, offer only about 200 watt-hours per kilogram—far from enough when compared to the energy density of kerosene. This discrepancy has led AeroDelft to explore liquid hydrogen (LH2), a choice that addresses the critical need for a more potent energy carrier.

Why Liquid Hydrogen?

Liquid hydrogen presents a solution to the energy density challenge. Compressed as a liquid, hydrogen’s energy potential dramatically increases, making it feasible for aviation use. However, maintaining hydrogen in a liquid state at -250 degrees Celsius introduces complex engineering challenges, from cryogenic storage systems to efficient fuel cell integration. AeroDelft’s collaboration with Teesing is pivotal here, focusing on developing ultra-light aluminum assemblies crucial for the storage and management of liquid hydrogen.

Airbus and the Future of Hydrogen Aviation

Major industry players like Airbus are also betting big on hydrogen, with plans to open a #ZEROe Development Center in Germany to expedite the creation of composite hydrogen system technologies. These advancements are aimed at crafting lightweight, cost-effective hydrogen storage solutions, positioning hydrogen as a central pillar in the future of sustainable aviation.

The Road Ahead

While Airbus explores hybrid-electric systems as an interim solution, the ultimate goal remains clear: a full transition to hydrogen-powered aircraft. This transition requires not only technological innovations but also substantial investments in infrastructure and regulatory adjustments to accommodate new fuel types.

AeroDelft’s Ongoing Innovation

At the heart of AeroDelft’s strategy is the integration of liquid hydrogen systems similar to those used in automotive applications, adapted for aviation’s unique demands. Their prototype developments and test systems signal significant progress towards realizing practical, hydrogen-fueled flight.

As we stand at the cusp of a new era in aviation, the collaboration between AeroDelft and Teesing underscores the transformative potential of liquid hydrogen. This partnership not only propels us towards achieving zero-emission aviation but also exemplifies the innovative spirit necessary to overcome the sector’s most daunting challenges.

Join the Discussion

We invite you to engage with us as we explore the future of aviation, driven by liquid hydrogen. Your insights and support are crucial as we navigate this exciting journey toward a sustainable flying tomorrow.

#AviationInnovation #SustainableAviation #HydrogenPower #AeroDelft #Teesing #ZeroEmissions

The main shortcoming of batteries of the current generation is their low energy density compared to kerosene. For example, the density of lithium-ion (Li-ion) batteries widely used in the automotive sector is about 200 watt-hours per kilogram (Wh/kg). By comparison, the energy density of kerosene is about 50 times higher. Even if Li-Ion has further room for improvement, aircraft electrification needs something much more powerful. AeroDelft did consider and test batteries, but it results in too high a mass, so they abandoned that. There is a belief within the team that batteries are never going to achieve the necessary density either. The energy density of hydrogen is also not naturally sufficient. Existing vehicle systems work with gaseous hydrogen (GH2) and a tank pressure of 350 bar. This is sufficient for small vehicles such as city cars, forklifts and stationary power generators. But for heavier truck traffic, systems that work with gaseous hydrogen at 700 bar refueling pressure are being looked at to create sufficient range while not taking up too much space for the hydrogen tanks. The same thing plays out with an airplane and to an even greater extent - the plane needs more hydrogen than it could carry. Further compression into liquid is then the only option. That means we are talking about a cryogenic system with liquid hydrogen (LH2) at a low operating pressure (about 5 bar). To maintain the cryogenic state, the hydrogen must remain cool: -250 degrees Celsius. This is the challenge that not only AeroDelft with 50 team members is working on: major manufacturers Airbus are also working on zero emission aviation based on hydrogen.

THE ZERO EMISSION AVIATION ROADMAP

Airbus takes electrification of flying seriously: a ZEROe Development Center for hydrogen technologies is set to open in Stade, northern Germany, in 2024. The center will accelerate the development of composite hydrogen system technologies for the storage and distribution of cryogenic liquid hydrogen. They will focus mainly on cryogenic hydrogen tanks based on composite technology to achieve cost-competitive lightweight hydrogen systems. That is, however, a solution that will only be available in the long term (2035 at the earliest). Therefore, Airbus envisions an interim solution in the form of hybrid-electric propulsion. Only hybrid propulsion gives only a 5% improvement in energy efficiency and reduction in CO2 emissions, they expect. And future hybrid and all-electric aircraft will need megawatts of power to operate. This implies huge improvements in power electronics in terms of integration, performance, efficiency and component size and weight. The illustration below shows the energy challenge we face.

AERODELFT'S SYSTEM

Lucille Guda explains that AeroDelft initially created a system based on gaseous hydrogen. That was tested with a separate propeller and works. The similarity to vehicle systems as we know them is great: hydrogen is stored under high pressure and brought to the working pressure of the hydrogen stack in 2 steps. The electronic control and auxiliary systems such as dehumidifiers and humidifiers are all integrated in house. In parallel, they are developing the liquid hydrogen-based tank system. This makes sense because the whole system is almost the same after the liquid hydrogen is converted to gas by a heat exchanger. For the liquid hydrogen system, AeroDelft chose a double-walled aluminum tank. The insulation to keep the hydrogen at -250 degrees Celsius is based on a vacuum between the 2 tank walls.

EVAPORATION OF LIQUID HYDROGEN

Insulating the hydrogen tank is just one of many challenges - another major challenge is to vaporize the liquid hydrogen in a controlled manner so that it can be fed into the fuel cell. Few measurement and control components can withstand cryogenic temperatures while being small and light. And the expansion and contraction of components when the temperature of hydrogen is increased from -250 degrees to ambient temperature also plays a role. Therefore, heating is done in 2 steps: the liquid becomes gaseous with heating tapes. Next comes a tubular heat exchanger that takes care of heating from -250 degrees to ambient temperature, which the pressure regulator after it can handle. The output of this flow meter/regulator is used by the control electronics to keep the system pressure at 3 bar.