Helicopter: hybrid propulsion in all its forms
Hybrid propulsion is a key to reducing the carbon footprint of air transport. By combining thermal and electrical energy, aircraft could reduce their fuel consumption by 20%, thereby reducing CO2 emissions. What is hybrid propulsion? What are the opportunities offered by hybridization? Bruno Bellanger, Program Director at Safran Helicopter Engines, presents the first application cases in the helicopter world.
HOW IS HYBRIDIZATION AN ESSENTIAL MEANS TO DECARBONIZE AVIATION?
In the helicopter world, in line with the Group's global strategy, we are working on three complementary areas to reduce our CO2 emissions: the use of alternative fuels, the ultra-efficiency of our combustion engines and hybridization. Hybridization is the combination of thermal and electrical energy, which reduces the fuel consumption of the thermal engine and therefore the CO2 emissions. Our goal is to reduce helicopter fuel consumption by 20 percent by the end of the decade through various hybridization concepts. In addition to this 20%, there will be gains in fuel consumption from our next-generation turbines and gains associated with the use of alternative fuels (Sustainable Aviation Fuels).
HOW CAN AN ELECTRIC MOTOR BE USED TO PROPEL A HELICOPTER?
As for short and medium-haul aircraft, the use of 100% electric propulsion for helicopters is not feasible today. With the exception of small aircraft and for short distances, all-electricity will not be available immediately, given the energy density required to carry out the missions performed by a helicopter. Combustion engines will therefore remain the majority on the market. However, this future generation of more efficient engines will incorporate electric motors that will reduce fuel consumption, reduce noise, improve safety and reduce particulate emissions. It is important to remember that hybridization is multiform! Electrical energy can be used transiently, for different phases of flight and to meet different needs depending on the aircraft model, range and mission.
WHAT ARE THE DIFFERENT HYBRIDIZATION CONCEPTS CURRENTLY BEING DEVELOPED BY SAFRAN HELICOPTER ENGINES?
"Eco mode" is one of the first applications we developed. It applies to twin-engine helicopters. While the takeoff and emergency phases require a lot of energy, in "cruise" flight, the helicopter does not need the full power of both engines to operate. The "Eco mode" consists of putting one of the two engines to sleep during this phase of flight. Thanks to the power supply from an extremely reliable electric motor developed by Safran, the second engine can be restarted manually or automatically very quickly. This function is similar to the "Start and Stop" system found in cars. The Airbus Helicopters RACER demonstrator will be the first to include this system. This is a first form of hybridization that already saves up to 20 percent in fuel consumption, depending on the mission.
For the helicopter, we are also developing "electric boost" systems, which are a form of transient assistance. The electrical energy is used here as a power supplement over a given period of time. This solution brings several advantages, beyond consumption, such as the reduction of noise pollution or particle emissions. It is also a solution that could provide backup power for single-engine helicopters.
Finally, at Safran Helicopter Engines and with other Group companies, we are working on distributed hybrid propulsion systems for vehicles that are a complete departure from today's architectures: VTOLs, vertical takeoff and landing vehicles, and STOLs, horizontal short takeoff and landing vehicles. The EcoPulse, a distributed hybrid propulsion aircraft demonstrator designed by Daher, Safran and Airbus featuring ENGINeUS™ electric motors from Safran Electrical & Power and a turbogenerator from Safran Power Units, is a first example. This vehicle, of the STOL type, is equipped with a turbogenerator, i.e. the association of a combustion engine and a generator, and batteries. The whole powering several electric motors distributed on the two wings. This is an important project that, like all the other hybridization concepts being worked on by Group companies, will provide a better understanding of the contributions of this type of hybrid propulsion to the aircraft of tomorrow.
BEYOND THE REDUCTION OF ENERGY CONSUMPTION, WHAT ARE THE OTHER OPPORTUNITIES OF HYBRIDIZATION?
In addition to the environmental benefits, hybridization also opens up interesting perspectives on maintenance costs, noise emissions and flight safety. On this last point, regulations do not currently allow overflight of European cities for safety reasons in case of engine failure. The addition of an electric motor on this type of aircraft would provide electrical power in case of failure, allowing the pilot to reach a clear area to land safely.