AIR - Air NZ.

**Doug** · 17-09-2021, 09:38 AM

Originally Posted by mikelee

bio fuel will not be practical for a while I reckon, I believe some kind of hybrid, with battery power, will be more likely. After all, planes don't have to worry about stop and go, like a car, so just need to use battery for take off and landing to maximise fuel saving.

Gasoline energy density is 47.5 MJ/kg. A lithium-ion battery pack has about 0.3 MJ/kg . Gasoline thus has about 100 times the energy density of a lithium-ion battery.
Battery planes unlikely for long distance travel with current technology.

**causecelebre** · 17-09-2021, 09:50 AM

AIR loves a good greenwash

**Beagle** · 17-09-2021, 09:56 AM

Originally Posted by Doug

Gasoline energy density is 47.5 MJ/kg. A lithium-ion battery pack has about 0.3 MJ/kg . Gasoline thus has about 100 times the energy density of a lithium-ion battery.
Battery planes unlikely for long distance travel with current technology.

Interesting. Can you unpack that for me a bit more ?
If I put 60 liters of fuel in my car I might drive for 600 km's. I understand petrol weigh's about 0.75 kg a liter so 60 x 0.75 = 45 kg fuel = 600 km's.
Some EV's with 600 kg lithium ion battery packs are doing up to 600 km's range. 600 / 45 = 13 times the weight to expend the same amount of energy, not 100 ?
What am I not understanding here ?

**Zaphod** · 17-09-2021, 09:58 AM

Originally Posted by Doug

Gasoline energy density is 47.5 MJ/kg. A lithium-ion battery pack has about 0.3 MJ/kg . Gasoline thus has about 100 times the energy density of a lithium-ion battery.
Battery planes unlikely for long distance travel with current technology.

Adding to the above, the weight of fuel on the aircraft also reduces through the course of the flight, while the battery packs will continue to weigh the same amount throughout.

Short domestic flights might work, but it will be interesting to see the detailed economics of a battery powered aircraft given the lower number of seats, lower cargo capacity, decreased availability for service (mostly related to charging times), and higher aircraft cost.

**Poet** · 17-09-2021, 10:04 AM

Originally Posted by Beagle

Interesting. Can you unpack that for me a bit more ?
If I put 60 liters of fuel in my car I might drive for 600 km's. I understand petrol weigh's about 0.75 kg a liter so 60 x 0.75 = 45 kg fuel = 600 km's.
Some EV's with 600 kg lithium ion battery packs are doing up to 600 km's range. 600 / 45 = 13 times the weight to expend the same amount of energy, not 100 ?
What am I not understanding here ?

One factor here will be the fact that electric can take advantage of a higher degree of regeneration compared to petrol, and of course electric motor has much greater conversion efficiency than ICE (60% vs 20%)

**Dassets** · 17-09-2021, 10:06 AM

Worse. Plus add in 45 mins minimum plus alternate for IFR. Then for that Cessna Caravan $500t usd or nzd? for a charger at each airport. Probably no more than 200km apart. This is just impossible . To fly it to Auckland Wellington 2 recharges say total flight time of 8hrs. To bring it in dismantle. To sell it overseas dismantle.

**dobby41** · 17-09-2021, 10:13 AM

Originally Posted by Dassets

Worse. Plus add in 45 mins minimum plus alternate for IFR. Then for that Cessna Caravan $500t usd or nzd? for a charger at each airport. Probably no more than 200km apart. This is just impossible . To fly it to Auckland Wellington 2 recharges say total flight time of 8hrs. To bring it it dismantle. To sell it overseas dismantle.

Impossible today is old hat tomorrow.

**Zaphod** · 17-09-2021, 10:17 AM

Originally Posted by Beagle

Interesting. Can you unpack that for me a bit more ?
If I put 60 liters of fuel in my car I might drive for 600 km's. I understand petrol weigh's about 0.75 kg a liter so 60 x 0.75 = 45 kg fuel = 600 km's.
Some EV's with 600 kg lithium ion battery packs are doing up to 600 km's range. 600 / 45 = 13 times the weight to expend the same amount of energy, not 100 ?
What am I not understanding here ?

The density figures provided by Doug give you an idea of how much energy can be packed into a given space and explains why the battery pack used in a vehicle is so much larger than a fuel tank. Electric vehicles store much smaller amounts of energy on board, but are generally more efficient at using that stored energy. Basically, the calculations you've made above don't reflect all of the variables involved and might not be the best way to draw energy use comparisons between the two. It gets pretty complicated!