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Electric Plane Adoption Faces an Uphill Battle Thanks to Physics
n all-electric passenger plane took its first flight this fall, potentially heralding the entry of air travel into the electric age. Or does it? The Eviation Aircraft Alice you see above only cruised at 3,500 feet, traveling at 260 knots (or 300 miles per hour) for eight minutes. (jalopnik.com) और अधिक...Sort type: [Top] [Newest]
I wouldn't fly on one for anything. It is cold at 30k altitude and you know what cold does to batteries.
Ask the city of New York why they cancelled their program to transform their fleet of garbage trucks to battery power. HINT: Their decision was not motivated by the fact that an electric garbage truck cost as much as a fire engine.
The article has the correct conclusion, but has the intermediate numbers completely wrong. The author attempts to quote from some other dim witted reporter about specific energy of Jet fuel. They state it is about 12,600 watt-hours per kilogram. Well not actually correct, Jet Fuel has 43 MJ/kg and a Joule is a watt-second. So 43 million Joules is 11,944 watt-hours. (43,000,000 Joules / 3,600 seconds in an hour) So let's say 12,000 wh/kg
Then they go on to state this is only 1 watt for 1 hour??? No 12,000 watt-hours is 12,000 watts for one hour, or 1 watt for 12,000 hours!
Yes a gas turbine is probably about 35% efficient, though I would argue it is closer to 45% but let's stick with 35% so that 12,000 watt-hours per kilogram is reduced to a useful energy of 4,200 watt-hours per kilogram.
Then we have batteries at a mere 250 watt-hours per kilogram. So Jet fuel is 16.8 times more energy per kilogram of weight required.
But that is not the only drawback - we utilize the energy from the jet engines to keep the passengers and cargo from freezing, and we use it to heat the leading edges of the wings and engine cowls to prevent icing! (we use "bleed air" taken from the compressor stages, which a battery powered plane does not have, hence an additional 20-30% reduction of the battery's available energy is used for these ancillary functions)
Thus not only does an Electric aircraft need to use the scarce battery energy to provide thrust, but also to pressurize, heat the cabin and cargo, and provide necessary anti ice functions by heating the wings/cowls or having icing boots, etc.
So easily that 16.8 ratio for jet fuel vs battery turns into 20 or 25 ratio when you account for needed ancillary energy draw for safe flight! So a 747 which can fly 13 hours on jet fuel, could not even fly for the 45 minute reserve required by the FAA on batteries! (13 hours divided by 20 is 0.65 hours or 39 minutes of flight)
It's a stupid pipe dream made my brainwashed ****** who believe in unicorn farts and fairy dust solutions! (CO2 is NOT the boogeyman it is made out to be, it is the ESSENCE of life for without it there are no plants and without plants there are no animals or oxygen! To be aligned against CO2 is to be against LIFE!)
Then they go on to state this is only 1 watt for 1 hour??? No 12,000 watt-hours is 12,000 watts for one hour, or 1 watt for 12,000 hours!
Yes a gas turbine is probably about 35% efficient, though I would argue it is closer to 45% but let's stick with 35% so that 12,000 watt-hours per kilogram is reduced to a useful energy of 4,200 watt-hours per kilogram.
Then we have batteries at a mere 250 watt-hours per kilogram. So Jet fuel is 16.8 times more energy per kilogram of weight required.
But that is not the only drawback - we utilize the energy from the jet engines to keep the passengers and cargo from freezing, and we use it to heat the leading edges of the wings and engine cowls to prevent icing! (we use "bleed air" taken from the compressor stages, which a battery powered plane does not have, hence an additional 20-30% reduction of the battery's available energy is used for these ancillary functions)
Thus not only does an Electric aircraft need to use the scarce battery energy to provide thrust, but also to pressurize, heat the cabin and cargo, and provide necessary anti ice functions by heating the wings/cowls or having icing boots, etc.
So easily that 16.8 ratio for jet fuel vs battery turns into 20 or 25 ratio when you account for needed ancillary energy draw for safe flight! So a 747 which can fly 13 hours on jet fuel, could not even fly for the 45 minute reserve required by the FAA on batteries! (13 hours divided by 20 is 0.65 hours or 39 minutes of flight)
It's a stupid pipe dream made my brainwashed ****** who believe in unicorn farts and fairy dust solutions! (CO2 is NOT the boogeyman it is made out to be, it is the ESSENCE of life for without it there are no plants and without plants there are no animals or oxygen! To be aligned against CO2 is to be against LIFE!)
I'll give them a pass on 12,000 being pretty close to 12,600, but the next sentence was definitely a head-scratcher - I assume they meant to say "1 w*h is the ability to power 1 Watt for 1 hour" and just mistyped 1 kg of fuel instead of 1 w*h. I have no idea where the author then calculated 13.5 hours and 6200 miles of range without knowing how much power it takes the 747 to sustain the assumed cruising speed and altitude, but those numbers do more or less match Boeing's claimed specs.
So, what ultimately matters (and how the author should have presented it) is how much usable energy is in 1 kg of LiIon batteries vs jet fuel. Using the author's assumptions, we get 4000 w*h (12,000 w*h/kg potential times ~1/3 efficiency) for jet fuel and 125 w*h/kg (250 w*h/kg potential times 1/2 efficiency) for LiIon batteries, or about 3% as much. Thus, the hypothetical electric airplane's range is 3% that of the 747, or... about 24 minutes and 186 miles (300 km), which is about what the other said. I'm inclined to believe he actually did the math right and just botched the write-up.
So, what ultimately matters (and how the author should have presented it) is how much usable energy is in 1 kg of LiIon batteries vs jet fuel. Using the author's assumptions, we get 4000 w*h (12,000 w*h/kg potential times ~1/3 efficiency) for jet fuel and 125 w*h/kg (250 w*h/kg potential times 1/2 efficiency) for LiIon batteries, or about 3% as much. Thus, the hypothetical electric airplane's range is 3% that of the 747, or... about 24 minutes and 186 miles (300 km), which is about what the other said. I'm inclined to believe he actually did the math right and just botched the write-up.
Damn science getting in the way of ideology again. How can we go green if science won’t co-operate? For those of you who do not speak fluent sarcasm that’s sarcasm.
But to be serious the Wright brother’s first flight only lasted about 12 seconds but showed the path forward. Every step is a step forward and maybe some day Electric Planes will be viable.
But to be serious the Wright brother’s first flight only lasted about 12 seconds but showed the path forward. Every step is a step forward and maybe some day Electric Planes will be viable.
Wouldn't one kilogram of jet fuel give you 1 watt of power for 12,600 hours?