Shaping the future of hybrid electric propulsion

28 July 2014, 11:45 p.m. EDT
by Lawrence Garrett, AIAA web editor

shaping_Future_Hybrid_Electric_Panel_28Jul14

“A Future with Hybrid Electric Propulsion Systems – Opportunities and Challenges,” at AIAA’s Propulsion & Energy Forum on Monday morning.

The aviation industry is a vital component of the U.S. economy, and hybrid electric propulsion systems are likely to be a key element of the aerospace industry’s future: That was the primary message delivered by of a panel of industry experts who met to discuss “A Future with Hybrid Electric Propulsion Systems – Opportunities and Challenges,” at AIAA’s Propulsion & Energy Forum on Monday morning.

Moderating the panel was Rubén Del Rosario, manager of the Fixed Wing Project at NASA Glenn Research Center. He said the aviation industry accounts for $1.3 trillion in economic activity, providing over 10 million jobs for the U.S. alone and accounting for more than 5% of the total U.S. gross domestic product. He added that the commercial aviation industry is “probably the only one that provides the U.S. with a substantially positive trade balance with the rest of the world.”

Despite these positive numbers, Del Rosario cautioned that “not all is well, and aviation is facing major challenges.” If left unaddressed, these issues will significantly impede the industry’s future growth. Touching on some of the environmental impacts of aviation, Del Rosario cited the enormous amount of jet fuel that U.S. commercial carriers and DOD have burned – costing a total of $73 billion in 2008, for example. He also noted that more than 250 million tons of CO2 are released each year into the atmosphere in the U.S., and reducing that amount will be “a “monumental challenge,” he said.

Nateri Madavan, deputy project scientist at NASA Glenn, discussed hybrid electric propulsion and “what we hope to get from this exciting technology.” He said that NASA is all about improving efficiency and environmental compatibility while sustaining the growth of commercial aviation through early-stage research and the initial development of “game-changing technologies and concepts” for fixed wing aircraft and propulsion systems. He added, “Our focus is very long-term: Gen N+3, three generations from now.” Madavan also said NASA has identified hybrid gas electric propulsion as a very important technology and is making substantial investments in this area.

Kevin Daffey, global head of electrical power and control systems for Rolls-Royce, shared the European perspective, touching on the electronic revolution in hybrid propulsion systems. Among the advantages of hybrid systems, he said, are greater operational flexibility, reduced losses, and fuel reductions of up to 50% relative to conventional mechanical propulsion systems. Daffey compared the aerospace propulsion industry to that of Marine propulsion, “the quiet revolution at sea.” Since 1999, he said, “every single cruise ship that has been built has been electric,” suggesting that the aerospace industry should “go and look at the Marine industry – there’s a lot of things we can learn there.” He added, “superconductivity is probably where the future will be.”

Marty Bradley, Technical Fellow at Boeing Commercial Airplanes, and chair of the AIAA Green Engineering Program Committee, discussed progress on Boeing’s hybrid electric transport project, focusing on the subsonic ultra-green aircraft research – or SUGAR – Volt concept and the project’s numerous challenges, primarily the impact of energy costs. SUGAR Volt, with a 1750-horsepower electric motor, meets NASA’s fuel burn goal; increasing the motor size and battery weight continues to decrease fuel burn but also consumes more total energy. Bradley said the Boeing team put together an energy-cost approach that looked at battery costs and battery life, and “it’s really battery life divided by cost that turns out to be the important ratio.” He said Boeing is looking at a range of technologies – not just hybrid electric – including aviation biofuels, fuel cell demonstrator airplane flight tests, and flight testing of hydrogen fueled aircraft.

John Nairus, chief engineer in the Power & Controls Division of the Air Force Research Laboratory, discussed the challenges in getting aircraft to do more than they can do today, when the Air Force is already challenged to get today’s capabilities airborne. Regarding electric initiatives, he said their efforts focus mainly on the smart use of energy, and that “the Air Force’s hybrid-electric propulsion focus is Group 1-3 UAS”– unmanned aircraft systems.

Neil Garrigan, executive manager of aviation advanced technology at GE Aviation, gave his company’s perspective on the challenges of hybrid technology. He said that “electrification is here, with more to come,” and that continuous technology and product improvements are needed to enable growth. Revolutionary changes, he said, will require "order of magnitude" improvements that some people “have referred to as miracles.” Garrigan concluded by saying they have to go back to basics, because electric machines have been around for a long time. But these advances are “something we need to go after,” and “we, collectively as an industry,” along with government, should prepare to “shape the future of flight, and do this together. It’s pretty exciting,” he said.

To view the entire session, visit AIAA's livestream channel.