Let me add some real numbers from the world of electric motorcycles!
Instead of electric cars, IMHO electric motorcycle development in past 5 years show how battery capacity has changed without liquid cooling as they need to keep volume, weight, and cost down.
Here is a snapshot of the 2013 Zero powertrain battery specification.
View attachment 66860
The 2013 battery with BMS is 42 lbs and 2.8KWhr (132Whr/Kg)
The new 2018 battery with BMS is 42 lbs and 3.6KWhr (188 Whr/Kg)
The volume & weight of the battery pack is the same year over year as the frame remained the same. This is a 42% increase over 5 years.
I have yet to see an aircraft using a Nissan Leaf or BMW i3 powertrain but the egull and its derivatives have flown with the 2013 Zero powertrain. Also the Windward Goshawk will use the new Zero powertrain. There is a Belite here on HBA that is using zero too.
A few remarks:I just watched the video, and they really phrase things in the worst possible way to make the energy densities look low. But if you just keep track of the statements it makes, it really should have the complete opposite conclusion for batteries.
Statements on the left are from the video, the right is the equivalent statement about density:
Lithium ion with the same energy can theoretically be 50% of the weight of current batteries = Lithium ion can have 2x the density of current batteries
Lithium sulfur can weigh 30% of the Lithium ion = Lithium sulfur is 3x the density of the theoretical maximum of lithium ion (6x current batteries).
Lithium oxygen is 25% weight of lithium sulfur = 4x the density (24x current batteries).
Lithium fluorine (if possible) is 5% weight of lithium oxygen = 10 x the density (240x current batteries).
So the theoretical limit of batteries, using the video's own numbers, is 60,000 Wh/kg. Even ignoring lithium fluorine, you'd still get 6,000 Wh/kg as the theoretical maximum. I have no idea how he gets the 5% number at the end of the comparisons, it's not consistent with the comparisons before that. That's still 20x current, or 5,000 Wh/kg.
With the most pessimistic, out of nowhere 5% current figure, the Hummelbird that needs 20kW to fly for an hour? That's 8.8 lbs of battery, or 3.2 lbs less than the gasoline that would be needed.
Even if the development only got as far as lithium sulfur, at 1,500 Wh/kg, the Hummelbird would need 29 lbs. of batteries for an hour. Assuming a 25 lb electric motor plus 10 lbs of controller and wiring replaces the 85 lb 1/2 VW plus full 6 gallon tank, you would have 2.7 hours with batteries instead of 3 hours with gas at the exact same weight.
I can't vouch for these figures, I got them from the video and they didn't list sources. The video is inconsistent, and uses percentages in a way that supports the most pessimistic view of batteries in a biased way at best. And his math sucks. But the end result is that batteries theoretical limits are well in the range that will be useful.
It's likely to be a long wait to get to these limits, but his conclusion isn't consistent with his data in any way.
I wouldn't quality either as practical (for going the distance). Did I screw up the math? If not, would you qualify the best theoretical possible as practical?Even with the currently non-existing Li-O batteries, that SR22-like airframe would only have a range of 235 km, or about 145 miles at a modest 70 kts or so. While the Binder EB29 with half it's TOW in batteries would do a mighty 2200 km (1380 miles), that would be a flight of over 24 hours, cruising at a comfy 50 mph if there is no wind.
24x todays capacity is still 6000 Wh/kg, which is more than the effective energy density of gasoline when you take motor efficiency into question.A few remarks:
Battery energy density will be about half of the batteries number. You need a BMS, protection, barriers etc. These are actual numbers from real airframes.
If we ignore Lithium Fluorine (which only raison d'être is to prove that Darwinism will extinguish the fearless and stupid) we get roughly this:
24 times current battery density, which leads to:
I wouldn't quality either as practical (for going the distance). Did I screw up the math? If not, would you qualify the best theoretical possible as practical?
Lets assume that batteries alone cannot make up for the power demands of a practical cruising aircraft at this time.We've seen more and more discussion on HBA about battery-powered aircraft and hybrids. I've been arguing that it's fundamentally impossible to get range up enough for a practical airframe to be solely powered by batteries, necessitating hybrid aircraft powered by chemical means (piston generator, fuel cell).
Bottomline; for range hybrids will be the future
Check you math and sources. For gas as in Methane (55.5 MJ/kg) you would be correct. But gas as in gasoline (46.4 MJ/kg), which at 30% efficiency is 13.8MJ/kg. At 90%, current batteries (252 Wh/kg) provide 0.8MJ/kg. The rest of the numbers I covered in my other posts.So gas at about 30% efficiency gives about 16.5MJ/Kg. Current tech chemical batter at 90% efficiency gives about 1.8MJ/Kg. Better but very difficult (not yet built) chemical battery at 90% efficiency gives about 2.7MJ/Kg. Best but not at all practical (almost certainly will never be built) chemical battery at 90% efficiency gives about 4.5MJ/Kg.
(1) yes, given pipistrel is already doing this. Although I feel that it is the noise/gas price issue specifically in europe that's driving it. In the USA, I still think ICE has the edge.Lets assume that batteries alone cannot make up for the power demands of a practical cruising aircraft at this time.
(1) Is it practical to use battery powered aircraft such as the EMG-6 as trainer aircraft? (Considering that in practice you would have several battery packs to enable you to swap and go)
(2) For cruising two seat aircraft would a electric motor powered hybrid glider be practical?
(3) Is it better to have a fossil fuel propeller driven auxiliary engine to supplement the electric motors or is it better to use on-board electrical generation to supplement battery power?
(4) Batteries and solar?