Energy coefficients for comparison of aircraft supported by different propulsion systems

• Published in: Energy (Oxford) Vol. 191; p. 116391
• Main Authors: Rohacs, Jozsef, Rohacs, Daniel
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 15.01.2020; Elsevier BV
• Subjects: Aircraft; Aircraft design; batteries; Electric; electric power; Energy; Energy consumption; Energy factors; Energy intensity; Energy use; Energy utilization; flight; Fly by wire control; Hybrid-electric propulsion systems; prediction; Propulsion systems; specific energy; stakeholders; Weight reduction; Electric; Energy use; Energy factors; Aircraft; Energy intensity; Hybrid-electric propulsion systems
• ISSN: 0360-5442; 1873-6785
• DOI: 10.1016/j.energy.2019.116391

Stakeholders envision introduction of electric and hybrid-electric aircraft into operation by 2035. First developments meet a series of challenges caused mostly by deficiencies (like low specific energy) of battery technology. Due to this, electric aircraft will have unacceptably large take-off weight or significantly reduced range. Energy factors (energy used per unit of work performed adapted to electric and hybrid-electric aircraft can support the evaluation of aircraft with different propulsion systems, and prediction of required battery technology and electric energy generation. Using the recommended energy factors, aircraft with different propulsion systems are comparable at the concept inspiration and conceptual design stages of new aircraft design. The results are clear and understandable. Energy intensity (evaluating the “aerodynamic goodness” at cruise flight) is about 10–60% lower (better) for full electric aircraft, but such aircraft have 50–80% less range and 40–230% greater take-off mass than comparable conventionally powered aircraft. Analysis of the used energy factors shows that the full electric small 4-seater aircraft may use less energy for flights up to 750 km range. Total energy used per unit of work done is 15–20% greater than total used energy during aircraft operations. [Display omitted] •Energy factors evaluate the energy used per unit of work performed by aircraft – kJ/pkm or kJ/tkm.•Energy intensity defined for cruise part of flight can be used to compare the aerodynamic goodness of aircraft.•Energy used (consumption) during full flight missions evaluates the efficiency of the aircraft flight operations.•Total energy used estimates all the total life cycle used energy.•These factors can be used to compare the energy efficiency of aircraft as early as the conceptual design stage.