Originally Posted by
MathFox
Well, the batteries only need to supply that 90 MW during climb (and climb power is lower than take-off power), so you can drain the batteries with 90 MW in about 10 minutes, requiring a 15.000 kwh battery, which would cost about 3 million dollar at your quoted price. Not that much compared to the list price of a 747.
I agree, but once we get to our cruising altitude, how about a destination?
Originally Posted by
ion_berkley
vapilot2004
No disagreement from me, but I do think that you also need to take into account losses. The thermal efficiency of an aircraft turbofan is pretty poor compared with an electric motor....
Agreed, Ion_B. I believe it's around ~90% for our best electric motors, ~40% for the best we have in turbo fans.
Say, 2 to 1 to keep it simple, and we are left with perhaps a 20 to 1 ratio on the delta between aviation fuel and battery power, with the efficiency factored in, regarding energy to weight ratios.
empirically stated a 100kWh Tesla can easily drive 300 miles. Try that on 2.5 gallons of Kerosene or gas.
True again, although add two or three stone's worth of go juice and we get the same range using current tech on the ground. Put it in the air however and the mission at hand becomes all about the weight, yes?
Replacing the 120 metric tonnes of fuel at 20X the weight for a long range flight seems truly unreachable even on a massive aircraft. A short haul sector for a narrow body works out to around 160 tonnes of batteries in an aircraft designed for a
max fuel load of well under a quarter of that weight with a MTOW of half, let alone trip fuel where we get the same energy out of a mere 8 tonnes of kerosene.
With batteries being currently impractical, for cost and weight reasons, leaving aside energy management and replenishment times and costs, hybrid-electric propulsion seems like a great place to start...as demonstrated in our conversation starter, which has a cousin under development in the US as well.
There are people who are trying to sequester hydrogen without the high compression and heavy steel tanks. That would be the magic bullet for aircraft hybrids like the subject of our discussion. H2 > Fuel Cell > Ducted Electric Fans would be brilliant.