Revolutions in aircraft design are driven by innovations in propulsion. When new powerplants are invented, they are always first applied to conventional aircraft designs. However, performance advantages usually don’t appear until new aircraft concepts are optimised around the new powerplant.
In the early jet era aircraft like the P-59 Airacomet had minimal performance advantages over pistons, but just 12 years later the F-104 Starfighter was tailored to jet propulsion with revolutionary results.
Electrification of aviation is now at the stage where the jet age was in the late 1940s and early 1950s. New aircraft configurations that weren’t previously feasible are being tailored to the unique benefits of electric propulsion.
As an example, VerdeGo Aero is focusing on providing electric powertrain systems that make electrification of flight practical. Founded in 2017, VerdeGo is developing both hybrid-electric and battery electric powertrains that enable its customers to develop a diverse array of VTOL and fixed-wing aircraft. And the company has termed these powertrains Integrated Distributed Electric Propulsion (IDEP).
What are the Challenges for Battery-Electric Aviation?
While battery-electric aviation has an exciting long-term future, there are significant challenges with batteries for aircraft designed for long range, faster cruise speeds, VTOL missions, and heavy payloads.
As pioneers in electric flight, VerdeGo’s founders are acutely aware of the long-term potential and the near-term challenges for battery powered aircraft, and this has shaped VerdeGo's strategy to develop both hybrid and battery systems depending on the performance requirements of the aircraft.
In mid-2019, VerdeGo Aero and Continental Aerospace Technologies announced a strategic partnership involving both financial investment in VerdeGo, and the application of Continental’s market-leading Jet-A piston engines to drive the generators inside hybrid IDEP systems.
Continental joins Seyer Industries as aerospace industry strategic partners collaborating with VerdeGo on electric propulsion.
“For more than ten years I have been pushing to accelerate the electric flight revolution,” says Erik Lindbergh, Executive Chairman and co-founder of VerdeGo Aero.
“We are now at a point where amazing new aircraft designs are possible, and while batteries can support some market niches, if we want faster progress and certified commercial flight, hybrids are the path forward.”
“Battery technology has made significant advances, but improvements in specific energy have trended at around 5% per year for decades,” reflects Dr. Pat Anderson, CTO and co-founder of VerdeGo Aero. “At this pace it will take many years to advance from 200Wh/kg pack-level energy density, up to 800+ Wh/kg which is where some really exciting battery-electric aircraft designs are possible.
“Fortunately, we don’t have to wait because we can design hybrid systems now that behave like a battery from 20 years in the future.”
Hybrid-Electric Systems: Turbine Hybrid or Piston Hybrid?
One of the unexpected results of VerdeGo’s extensive hybrid-electric research has been the realization that piston hybrids have advantages over turbine hybrids in applications where turbines initially were assumed to be superior.
Many electric aircraft have both a peak power requirement for short durations and a constant cruise power requirement that is significantly lower than the peak.
In this situation, a battery pack can augment the engine/generator system when peak power is required, and the engine/generator powers the aircraft during steady-state cruising flight such that the engine does not have to be sized for the peak power requirements.
Also, while the power density (hp/lb or KW/kg) of a small turbine engine is higher than for a piston engine, the engine is only one element of a hybrid electric system that also includes the generator, battery, power distribution, motors and fuel.
The weight of a total hybrid system designed around a piston engine is not significantly greater than that of a turbine hybrid, especially when the weight of the fuel is factored into the comparison.
When small turbines are compared to Jet-A piston engines, the fuel burn of the piston engine can be 50% lower. This results in a significant reduction of both carbon emissions and direct operating cost.
Additionally, piston engines are quieter than small turbines, and they are significantly cheaper to purchase and maintain.
Using a Jet-A piston engine provides access to the same global fuel source as turbines but with significant improvements in operating cost.
Where’s the Market for Modular IDEP Systems?
VerdeGo’s modular IDEP systems can be configured for a wide array of applications. For example, standard IDEP components can be configured to support peak power levels of more than 1,000hp and continuous power of more than 350hp for VTOL applications using a twin-engine/generator system.
These same components can also be configured for a fixed-wing hybrid system with 700hp for take-off and 500hp for cruise. With the redundancy of twin engine/generator systems and an onboard battery pack, the twin-engine IDEP powertrain architecture has the potential to exceed the reliability of single-turbine systems while being more fuel efficient, quieter and lower-cost than turbine hybrids.
“VerdeGo sees a significant market for hybrid IDEP powertrains to enable new aviation markets for electric flight, decades before battery-electric options are viable,” says Eric Bartsch, CEO and co-founder of VerdeGo Aero.
“The operating economics of our Jet-A piston hybrid IDEP systems are also significantly better than turbine alternatives. Additionally, the high-performance battery technologies inside our hybrids can be used to support some early market niches where battery-electric powertrains already make sense.”
VerdeGo’s hybrid and battery IDEP systems are moving into the prototyping phase of their development programs with “iron bird” full-scale test systems planned to be operational in Q2 2020.
More information from www.verdego.com