Hybrid vehicles, which optimize the use of an electric motor and an internal combustion engine for power needs and energy conservation, may soon take flight with the leadership of a new company, Tigon EnerTec, spun off from CU-Boulder's aerospace engineering sciences department.
An engineering innovation that was initially dismissed by the aerospace community due to weight constraints and a long design cycle, the hybrid engine aircraft system is now gaining momentum thanks to the persistence of CU Professor Jean Koster and some enthusiastic students.
Koster's interest in alternative energy led him to propose the idea as a senior design project for CU students in the fall of 2009: "I realized that we have the (Toyota) Prius on the road, so why can't we have a flying Prius?" he says.
The project, which was partially funded by a NASA workforce development grant, attracted student interest because of the opportunity to be involved in an innovative technology, recalls Cody Humbarger, a BS/MS student in aerospace engineering sciences. Humbarger and three of his classmates were enrolled in the Engineering Entrepreneurship Program and hoping to get involved in a start-up company.
In spring 2010, the seven-student CU team successfully flew a small, remote-controlled hybrid aircraft, which was developed in collaboration with students at Daniel Webster College in New Hampshire. The CU students designed the hybrid propulsion system, while the DWC students, assisted by the University of Massachusetts Lowell, built the airframe according to specifications given by the Colorado team.
"It was exciting," Humbarger says, "and we got a lot of good data from it that we used to make modifications in the design."
General aviation airplanes use an internal combustion engine that is sized for the high-power requirements of takeoff and climbing. But the large engine burns inefficiently much of the time because most of a typical flight is conducted at lower-power cruising speeds. The fuel commonly used in these aircraft also contains high amounts of lead, which has become environmentally unacceptable.
Electric motors, on the other hand, are clean and able to operate at high efficiency over a broader range of power output, although they have a limited range due to the additional weight imposed by battery technology.
"We developed a gearing system that is highly efficient and pretty lightweight," says Koster, who was named CU-Boulder's New Inventor of the Year for 2010. "The pilot can selectively choose between an engine that is powered by conventional fuel, diesel, or even biofuel, in combination with an electric motor that is powered by batteries, photovoltaic cells, or other alternative power sources such as hydrogen."
There are two primary markets for the new, patent-pending Hybrid Electric Integrated Optimized System, known as HELIOS. The first is in small, radio-controlled or autonomous military aircraft used for intelligence, surveillance, and reconnaissance. The electric motor would allow the aircraft to fly quietly when needed, while the internal combustion engine would increase its range of flight.
A second application in general aviation, where engine failure poses a significant danger in single-engine aircraft, also is in the works. Having the ability to continue operating one of the two engines greatly increases safety, while a takeoff and landing mode using the electric engine could help address the FAA's goal of making airports quieter, Koster says.
"The future probably lies in electric aircraft," Koster says, "but battery technology is not yet at the point to make electric aircraft a viable option. The hybrid propulsion system can fulfill a need now and adjustments can be made as battery and solar cell technologies are further developed."
The development of the hybrid propulsion system is moving quickly. Support has been provided by the Renewable and Sustainable Energy Institute, Boulder Innovation Center, eSpace: The Center for Space Entrepreneurship (a joint venture launched by CU and Sierra Nevada Corporation), and the CU Office of Technology Transfer.
"With establishment of eSpace just a few years ago, we envisioned creation of an atmosphere of commercial innovation to complement our basic research activities," says Jeff Forbes, chair of the aerospace department. "It is amazing to me how rapidly this has taken hold. We are really producing a different genre of aerospace engineering graduates."
"It's definitely been working out," says Humbarger, who at 23 years old is chief operating engineer for Tigon EnerTec. "We have a lot of support, so this is a really good opportunity for us."
Koster serves as president of the newly incorporated company, and experienced entrepreneur Les Makepeace came on as its chief executive officer. Humbarger and fellow graduate students Derek Hillery, Eric Serani, and Alec Velazco fill the lead engineering positions.
"There was a lot of synergy going on, and I knew how to link the knots together," Koster says. "I see the students totally excited about this—you can see their hearts are in it. Supporting that passion and excitement to pioneer a new technology and take it to the next level of commercialization is very rewarding to see as an educator."