SAF isn’t new to us, we’ve been regularly testing our engines with blends of up to 100% SAF for well over a decade.
Pratt & Whitney successfully tested the GTF Advantage engine configuration with 100 percent sustainable fuel. The test took place in their West Palm Beach facility thus marking a key step on the road toward 100 percent SAF operation of GTF-powered aircraft. The test is also a key element of an extensive development program to ready the GTF Advantage for entry into service in 2024, by validating the engine’s performance on 100 percent SAF in thrust transients, starting, and operability. Congratulating Pratt & Whitney on this remarkable feat, we have selected them as our MRO of the Month. We got a chance to speak to Graham Webb, Chief sustainability officer at Pratt & Whitney, about this milestone’s inspirational story.
Pratt & Whitney knows and recognizes the critical role played by SAF for the aviation industry to reach net-zero CO2 emissions by 2050. Hence supporting greater usage of SAF is a core part of our strategy for making aviation more sustainable, says Mr. Webb. While SAF is already certified for use across all of the commercial engines at blends of up to 50% with conventional Jet A/A1 kerosene, there is growing interest in enabling future use of up to 100% SAF blends, for the obvious reason that the more SAF is used, the greater the lifecycle emissions reduction attained.
“We know SAF like the back of our hand,” he continues “SAF isn’t new to us, we’ve been regularly testing our engines with blends of up to 100% SAF for well over a decade, and we have also played an active role in defining the standards which allow SAFs to be widely used today. But with our continued focus on sustainability and addressing the causes of climate change, the urgency of increasing SAF use and availability has never been more important,” he further adds.
Surprisingly, Pratt’s team at the West Palm Beach facility faced no particular operational challenges while using alternative fuel blends compared to standard kerosene. The team tested the engines with various SAF blends up to 100 percent so frequently over a decade, that SAF tests have now become a routine for them.
With our GTF Advantage engine tests, we used 100% Hydroprocessed Esters and Fatty Acids Synthetic Paraffinic Kerosine (HEFA-SPK) derived from renewable sources, and during the test, the engine operated exactly as expected, explains Mr. Webb.
The global demand for GTF engines is on the continuous rise, in such a scenario the teams at Pratt are striving day and night to achieve their target of 100 percent SAF engine, currently, they are in the engine development and validation program for the GTF Advantage engine, targeting customer deliveries by early 2024.
Challenge of scaling up the SAF production!
However, the challenge arises with it comes to procuring enough SAF for the tests. “SAF today is simply not as easy to get hold of as regular kerosene,” comments Mr. Webb. “SAF production accounts for less than 0.01% of global fuel demand today. The 100% HEFA-SPK for our GTF Advantage™ test was supplied by World Energy. Our collaboration with fuel producers like Air bp will help secure access to SAF to meet our testing needs going forward,” he further adds.
Today SAF represents just 0.01% of global aviation fuel use. The expectation is to reach 2% by 2025 and 5% by 2030. The goal in the United States is to double this 2030 figure. The policymakers need to create a level playing field between fossil fuel and SAF to de-risk investment and bridge the initial green premium until economies of scale kick in and bring the cost of SAF down.
Commenting on the scaling up of SAF Mr. Webb replies, “We support policy measures like the SAF Grand Challenge and the Blender’s Tax Credit in the USA, which will help stimulate supply and demand, reducing the cost differential between SAF and conventional jet fuel. Ultimately, we need to see investment fast if we are going to hit the 2030 targets, as SAF plants take 5-6 years to build and commission.”
SAF + efficient propulsion system = sustainable aircraft
SAF is a key enabler for sustainable aviation and is critical to reaching net zero emissions by 2050. The main reason for this is that it provides a “drop-in” solution, which is fully compatible with the existing global aircraft fleet and fuel infrastructure. So considering that tens of thousands of aircraft flying today will still be in service in the decades to come, a drop in SAFs provides the fastest and most mature solution for reducing their lifecycle emissions, by replacing the need for fossil-based kerosene fuel.
“But our pursuit of SAF as an alternative fuel runs in parallel with ongoing efforts to develop ever more efficient aircraft propulsion systems, which will reduce the industry’s overall fuel demand and thus emissions,” comments Mr. Webb. “With the GTF, we see the continued potential to improve efficiency beyond the 16% step change this engine family achieved when it entered service in 2016. For this, we are developing technologies to leverage the geared architecture further, such as ceramic matrix composites (CMCs) and hybrid-electric propulsion, which will enable even better efficiency from future engines,” he further adds.
Other technologies for net-zero!
“We continue to work on a large number of technologies for our future thermal engines, including the geared turbofan architecture of the GTF which has a long runway for growth and evolution,” says Mr. Webb proudly. “For this, we are working to increase bypass ratio with higher gear ratios and increased deployment of composite materials for reducing weight, we are working to increase the temperatures and pressures present in the core of the engine with advanced materials and coatings, aerodynamic, cooling, and sealing technologies,” he further adds.
One of the most exciting areas of innovation is hybrid-electric propulsion technology. The teams at Pratt & Whitney are currently working on a hybrid-electric flight demonstrator— in concert with Collins Aerospace and De Havilland Aircraft of Canada—which is targeting a 30% better fuel efficiency and lower CO2 emissions compared to today’s most advanced turboprop engines. We see many opportunities for hybrid-electric technologies to optimize efficiency and add capability across a range of applications, up to single-aisle passenger aircraft.
Until SAF is more widely available, another important tool for lifecycle emissions reduction is carbon offsetting, or carbon trading mechanisms. Already the use of carbon offsetting has become widespread in the airline industry, and we have seen growing demand from our customers.
“That’s why we introduced a carbon offsetting service for business aviation, helicopter, and regional aviation customers offered as part of our Eagle Service™ Plan (ESP™) or Fleet Management™ Program (FMP™). The offsetting service makes it straightforward for operators to reduce their carbon footprint by allocating funds to renewable energy and forest conservation projects around the world,” exclaims Mr. Webb.
Hydrogen fuel as a power source for aero engines
Hydrogen holds considerable potential for aviation as an energy-rich and zero-carbon fuel, but it also brings considerable challenges in terms of fuel storage, handling, and production. “Fortunately, we at Pratt & Whitney are very experienced with the properties of this fuel, having worked on various hydrogen combustion and fuel cell technologies stretching back over 60 years,” replies Mr. Webb with a sigh.
Current and near-term fuel cell technology capability limits their applications to very small aircraft with limited payload and range. “Our current focus is to develop technologies that could take full advantage of hydrogen’s opportunities. This is the goal of our recently announced HySIITE project (Hydrogen Steam Injected Intercooled Turbine Engine), which we are developing with the support of the U.S. Department of Energy’s ARPA-E program. Using hydrogen combustion, water vapor recovery, and steam injection, HySIITE aims to achieve a 35% improvement in fuel efficiency and an 80% reduction in NOx emissions for single-aisle aircraft,” he adds.
Such a step forward in fuel efficiency could play an important role in making hydrogen economically viable as a fuel source from the standpoint of aircraft makers and operators.
The propulsion system is of course only part of the challenge with hydrogen. Viable service entry will also depend on incorporating the engine into an aircraft designed to carry hydrogen fuel and having a hydrogen delivery infrastructure available at airports. When asked about his opinion on hydrogen as an alternative to SAF, Mr. Webb says, “We do not believe this should lead to an “either/or” conclusion for using SAF or hydrogen. SAF still has a critical role to play toward net-zero CO2 emissions by 2050. It will take time for the infrastructure to develop to support hydrogen flight at scale. SAF can provide emissions reductions in the interim.”
The history of SAF
SAF emerged as a result of industry efforts starting in the early 2000s to develop alternative fuels for aviation. A key instigator was the Commercial Alternatives Aviation Fuels Initiative (CAAFI), a cross-industry organization of which Pratt & Whitney has been a charter member since it began in 2006. Over the following years, ASTM International established the industry-wide specifications for SAF which we use today, and which currently define seven different SAFs for use at blends of up to 50% with regular kerosene. But despite these important recent efforts, it must be said that studies into the use of synthetic fuels in the aviation industry go back decades. For example, one pathway for producing synthetic kerosene today is based on the Fischer-Tropsch process, which was developed in Germany in the 1920s.
“While we will continue our testing program for current and future engines, wider industry action is needed in two main areas. First, industry regulators with support from the OEMs will need to develop, ballot, and release a standard for 100% SAF blends to be used on a “drop-in” basis, making it compatible with existing aircraft and infrastructure,” comments Mr. Webb.
Besides this and more importantly, the aviation industry needs to see a significant scaling up in production capacity for SAF beyond the minuscule levels seen today. Governments will need to collaborate with industry partners to optimize the incentives for investment in infrastructure and help reduce the price differential between SAF and kerosene.
SAF is arguably the most important lever for achieving net-zero emissions for aviation, but it’s not the only tool at our disposal. “As a leading engine maker, we are also focused on continually improving the efficiency of aircraft with advanced propulsion technologies, to reduce overall fuel demand and emissions. And besides SAF, we are also looking at the potential of other alternative fuels, such as hydrogen, which offer the potential for zero-emissions flight,” he explains about the alternative routes to SAF.
The aviation industry’s focus has always been on greater fuel efficiency. Fuel is the first or second largest line-item expense for airlines and our customers have always needed more efficient engines.
The challenge is ensuring that airlines can continue to fly their current fleets well into the future while simultaneously reducing their carbon footprint. “That’s why we are advocating for public-private partnerships to significantly expand the availability of drop-in SAF solutions today, and to fund the next generation propulsion systems technology. We look at this challenge for what it is – an opportunity to both innovate and lead by example as a means to make positive change,” he signs off.
