We Need a New Flight Path for Decarbonizing Aviation

By Doug Arent, NREL Executive Director, Strategic Public-Private Partnerships

Like a pilot correcting for turbulence, aviation is adapting to a bold new horizon of action and possibility.

Cutting-edge technologies are unlocking options for lowering greenhouse gas emissions across the industry, one that has been called among the most difficult to decarbonize. Low-carbon fuels and energy carriers, ultra-efficient aircraft, resilient airport infrastructure — these innovations provide actionable pathways that didn’t even exist a few years ago.

But they arrive amid a flurry of urgent climate pressures and societal obligations.

Flight demand is growing rapidly around the world. Experts predict aviation-related carbon emissions — currently 2.5% of global emissions — could double by 2050 if unabated. Communities are calling for energy and environmental justice, and a world where everyone can access the benefits of clean, affordable energy and mobility. The clock for climate action is ticking.

In the face of change and opportunity, what kind of strategy is needed to advance the industry’s efforts toward a more resilient, sustainable flight path?

Given rapid advances in fuels, aircraft, and airports, we need a holistic framework for conceptualizing low-carbon aviation energy.

NREL considers fuels (including electricity, hydrogen, and sustainable aviation fuel), airports, and aircraft to be the three pillars of a sustainable aviation ecosystem. That framework also involves system interdependencies, including energy justice, the overarching sustainable aviation ecosystem, energy solutions, communications, the transportation network, and human systems.

Aviation Is An Energy Ecosystem

Here at the National Renewable Energy Laboratory (NREL), we understand sustainable aviation as a holistic system — better still, as a vibrant ecosystem, with its web of resources, stakeholders, services, and rules that together comprise the whole.

In this energy ecosystem, sustainable fuels, ground infrastructure, and aircraft are not isolated components. Rather they are set amid a system of interdependencies, all of which we must understand, model, and optimize if we hope to achieve a truly sustainable future for flight. For example:

· What aviation fuels and energy carriers best suit a given flight path to maximize emissions savings? How can we scale their production, lower their carbon intensity, and accelerate their approval for commercial use?

· Can airports, bases, and vertiports securely and resiliently deliver multiple forms of energy to meet an ever-changing demand profile?

· Can future aircraft better connect rural communities with urban cores? If so, what advances do we need in their energy components? And how can we be confident airports have the energy supplies needed to support them?

These questions are but a handful of hundreds we must ask along our path to aviation decarbonization. It’s for this reason that NREL developed its Roadmap Toward a Sustainable Aviation Ecosystem.

Decarbonizing aviation means navigating an array of competing demands, priorities, and requirements. A comprehensive, coordinated sustainable aviation strategy is essential for paving the way for research, development, demonstration, and deployment — leading to solutions for decarbonizing aviation.

How To Power Our Planes — Sustainable Aviation Fuels, Hydrogen, Electricity

Today, fuel combustion typically contributes 90% of total carbon emissions in aviation. For that reason, the industry is pivoting to more sustainable energy carriers, such as low-carbon sustainable aviation fuels, hydrogen, and electricity stored in batteries.

With the potential for deep reductions in life cycle greenhouse gas emissions, these advanced energy carriers are critical for decarbonizing flight by mid-century. In many cases, they also offer advantages in terms of resiliency, performance, and accessibility.

Multiple pathways to achieve net-zero energy delivery between 2020 and 2050. Sustainable aviation fuel is a viable energy pathway as early as 2020 and as far forward as 2050 and beyond, and is applicable for commuter, regional, short-, medium-, and long-haul flights. Electricity is a viable energy pathway as early as 2025 for commuter flights, as early as 2035 for regional flights, and as early as 2045 for short-haul flights. Hydrogen fuel cell is a viable energy pathway as early as 2035 for reg
New technologies are changing the future of aviation by providing actionable pathways for lowering greenhouse gas emissions in a sector that is among the most difficult to decarbonize.

Still, some options are only now being developed. Others, including sustainable aviation fuels, are already making headway into the market, but they require working in lockstep to reduce development, regulatory, economic, and infrastructure risks while rapidly accelerating their production and distribution.

To support these transitions, NREL offers end-to-end expertise in developing and demonstrating low- and net-zero-carbon aviation energy. From field to fuel, electron to molecule, and bench to pilot scales, we are already leading critical R&D:

· As a leader of the SAFFiRE project, NREL is helping turn corn stover — agricultural waste — into profitable sustainable aviation fuel that is cheaper than Jet A and could reduce carbon intensity by up to 84%.

· Researchers are assessing the power requirements for an increase in electric planes, which could lower noise and expand mobility options for rural communities.

Integrated, Decarbonized Ground Aviation Infrastructure

Without a doubt, deploying low-carbon fuels is a priority. But ground operations represent 9%–20% of all aviation carbon emissions. Airports, bases, and vertiports are ripe with opportunities for lowering emissions while boosting the resiliency of operations and nearby communities.

Airports are mobility and cargo hubs, servicing millions of travelers and goods every year at more than 5,000 locations across the United States. Airports are quickly becoming community energy hubs, too. By using acres of underutilized land for renewable energy generation, airports can support increasingly electrified buildings, ground vehicles, and aircraft. That could enable them to supply and store clean energy for nearby communities during off-peak hours and natural disasters.

NREL analysis and modeling can resiliently decarbonize airports, military bases, and vertiports to seamlessly integrate them with ground-based transportation systems.

But just like advanced fuels, effectively decarbonizing ground infrastructure raises questions on how to manage added electricity loads, ensure operation amid outages, coordinate diverse energy sources, and prevent cyberattacks.

NREL modeling links the numerous elements of the airport energy landscape, giving planners a birds-eye view of energy demand as it grows and evolves with changing regulations, technologies, and consumer habits:

· NREL helps model and analyze the critical operational capabilities across airports — steps necessary for meeting net-zero carbon emissions goals.

· NREL is analyzing the integration of increased electrification at airports across the country, helping support the energy needs of future electric aircraft and those of airports and surrounding communities.

· NREL has leading research on power system decarbonization, evaluating the requirements to deliver reliable, affordable, and clean power across the nation.

Sustainable Aircraft of the Future

Aircraft of the future will transcend the fossil fuel-based approach of today’s aircraft fleet. From supersonic aircraft to electric vertical takeoff and landing vehicles to turbine airplanes tuned to maximize efficiency — advanced aircraft are transforming our airspaces and helping service providers address the changing needs of investors, communities, and consumers.

The slate of emerging technologies is quite broad:

· Ultra-high-efficient motors and controllers

· Enhancements to existing powertrain components

· Next-generation powertrain systems built for decarbonized “fuels”

· Energy-dense batteries

· Liquid/gaseous fuel storage

· Lightweight material composites.

These technologies give us unprecedented precision to tailor aircraft design and fuels to their duty cycles, harnessing every ounce of efficiency and carbon savings. New aircraft may afford lower-emission taxi service between an airport and an urban core. They may make flights from rural areas more economical, offering communities easier access to the opportunities available in cities.

As with fuels and ground infrastructure, NREL develops systems and components needed to support advanced aircraft designs:

· Researchers have demonstrated high-flow-rate hydrogen fueling, laying the groundwork for supplying next-gen hydrogen for heavy-duty applications like planes.

· NREL is helping develop lightweight and ultraefficient electric motors, propulsion systems, and thermal management technologies across a range of applications — from commercial aviation to smaller takeoff and landing vehicles.

Amid Rapidly Shifting Terrain, We Need Crystal-Clear Focus

Since the Wright brothers flew the first airplane in Kitty Hawk, North Carolina, the aviation industry has evolved into a safe, modern, and reliable system that continues to improve its efficiency, service, accessibility, and sustainability. Aviation is a pillar of communities across the country, connecting cities and fostering the trade of goods and ideas. But aviation is also a source of noise and localized emissions.

Without a doubt, decarbonizing aviation will be a colossal task. The aviation ecosystem is incredibly complex. But by pooling our talents, sharing resources, and developing new analyses, we can decipher and create the best flight path for tackling even the toughest energy challenges.

NREL is committed to asking the right research questions, wielding the best tools to pen data-driven answers, and forming the partnerships needed to guide energy technologies smoothly onto the tarmac. Using a holistic assessment — crossing passenger and freight movements, urban and rural geographies — we can implement a coordinated strategy to evolve and accelerate aviation decarbonization.

That way, our success might be measured in more than the carbon intensity of a seat from New York to Barcelona or from Chadron, Nebraska, to Denver International Airport. It might be visible in the newfound affordability, accessibility, and resiliency of the entire aviation ecosystem.

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