There is an interesting illustrated 10-page article regarding the latest electric and hydrogen-powered aircraft that are currently being tested and on the drawing boards in the March/April issue of Flight Journal magazine. (Perhaps your local library subscribes to the magazine. Their website is FlightJournal.com)
What caught my eye were the following two paragraphs:
"Jet fuel has an energy density of about 12,000 watt-hours per kilogram (Wh/kg. Lithium-ion batteries have an energy density at the cell level of about 250 Wh/kg. Battery pack energy is typically 20% lower given the weight penalty for safety features.
Battery efficiency is reportedly improving at about 5-8% a year. NASA has suggested that batteries with 350-Wh/kg energy density at the pack level could be commercially ready by 2030. This would make small, short-range aircraft feasible with up to 19 seats for distances less than 250 miles. If new technology provides commercially adequate charge and charge-cycle times, electric short-range 30-seat aircraft could become feasible."
