I’m investing in dilithium crystals. My stash will be worth tens of dollars in the future.
BJC
BJC
Why battery-powered aircraft will never have significant range
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Well... I guess I'll have to discuss
your opening posts video basically states in the end that the theoretical gains (given basically 3 chemistry generational leaps) is 20 times the amount of energy per unit weight.
So really, your claim we are up against 'theoretical' limits isn't really holding water for me.
The 'hard' leap, Li-S, offers a reduction to 30% of the weight. so given todays best batteries are pushing 250, that gives 833 Wh/kg (It implies in the video the current best are about 300 Wh/kg). Given we are about 50% of theoretical maximum of current Li ion, lets say Li-S is a pessimistic 25%, so about 400 Wh/kg
Like said before, 400 Wh/kg with high teens L/D allow about 400miles, which is (if my memory serves) >80% of small commuter aircraft trips.
In short, for all this hopalla about 'small electric GA revolution' to work, I feel we need one chemistry leap up.
That's a revolution that's hard to predict. It cant really be put on a timeline. But 'impossible'? No. Really no.
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If anyone wants to watch a video about 'hard' limits in engineering, this is an excellent one about rockets
https://www.youtube.com/watch?v=oY3GclS5VUQ&list=FLUhhwmR-846HI4OwqlMocGA&index=131
https://www.youtube.com/watch?v=oY3GclS5VUQ&list=FLUhhwmR-846HI4OwqlMocGA&index=131
autoreply
Well-Known Member
That's highly dependent on how you define "small electric GA revolution". For trainers, local flights etc, battery-powered GA is feasible today.
But going somewhere?
Note that the numbers in the OP are actual energy densities, so including BMS, mounting hardware, insulation etc. Any Li-based system will have to include those and they roughly double battery system weight. Ask Boeing how wise it is to omit some of that stuff.
Even the very best theoretical possible batteries (excluding Li-F) will yield a reasonably efficient airframe (SR22) to have a range of only 145 miles if you don't climb too high. Climb a bit higher or demand half an hour of extra "fuel" and you're still down to dozens of miles of range.
Unless there's something wrong with my math, how could that ever be practical for going distances?
Aesquire
Well-Known Member
Imaginary future batteries will solve all your problems. We've gone from Iron Acid batteries in cars to Lithium chemistry in only a century.
I'll bet you can have practical cross country performance equal to gasoline engines by 2117. Shipstones or Mr Fusion.
The trouble is I'll need to arrange to pay you with the help of an unborn descendant.
I'll bet you can have practical cross country performance equal to gasoline engines by 2117. Shipstones or Mr Fusion.
The trouble is I'll need to arrange to pay you with the help of an unborn descendant.
What Wh/kg are you using for this?
Using the videos numbers, and using your pessimistic 100 Wh/kg, Li-S would be 333Wh/kg, and Li-air would be 1,333 Wh/kg. So I have no idea what numbers your using...
DonEstenan
Member
Marginally possible, not really practical yet. Some improvements (battery capacity & cost) are still needed to make it the preferable choice.
For going distances ... get a hybrid using free-piston linear generator (if/when it finally becomes feasible/practical, hmmmm)
henryk
Well-Known Member
-but... (thrust force=80 kG/kW !!!)
View attachment Сравнение БПЛА .doc
-we should finde moore energy efficiant solutions...
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Presuming that future electrical energy-storage devices, forever, will be chemically-based "batteries" is without foundation. Sure, we're approaching some limits in lithium-based chemical batteries. This is not the ultimate energy-storage technology. It's just the best we have right now.
For current Li-ion types, yes, I agree.
But do note that battery technology isn't really a 'trend' sort of improvement. Its advances in fits and starts with a sudden introduction of new chemical types and lackluster to flat improvements after. Given the titanic amounts of R&D money being thrown at this problem with portable electronics, and soon (gov mandated, note china) large portions of auto industry, its really hard to predict what sort of advances we'll see in 10-20 years.
But do note that battery technology isn't really a 'trend' sort of improvement. Its advances in fits and starts with a sudden introduction of new chemical types and lackluster to flat improvements after. Given the titanic amounts of R&D money being thrown at this problem with portable electronics, and soon (gov mandated, note china) large portions of auto industry, its really hard to predict what sort of advances we'll see in 10-20 years.
most people at my airport fly less than 50 hr a year, and never go farther than 100 mi. for lunch.
Hi,
I will present my electric self launching system in the SSA Convention in Reno.
It will be sold as a kit (almost off the shelf), so you can retrofit most of club class gliders and new ones of course.
"Never" is a strong word.
Certainly will not in the next few years. But a 300km range electric two seater is very near.
Everyone criticize the range of electric cars, when only less than 5% of the time the full tank is used in a petrol car.
With aviation will be the same, is not the range but the mission of the aircraft.
An all battery airplane for leisure flights of less than an hour is possible today, and you can buy it now if you want.
For instruction flight (most of the flights does not last more than an hour) you already have the Pipistrel alpha electro.
Most of the lessons aren`t about managing the petrol engine, so you can do at least 50% of the lessons with electric and lower the operational costs.
There is an Israely company that are developing a battery that charges in 5 minutes, the energy density is not the best, but with that time you need to charge it who cares (in most of uses).
For sailplanes, range is not the most important factor, reliability is. Most of accidents in sailplanes are because the sustainer engine did not start or take too much to do it.
If you have only 80km range with electric, i assure you that 99,95% (K=2) of the times you will arrive to your home base or another nice airfield. If the day is over and you are at 150km of your home, you have to learn to choose the task of the day
ScaleBirdsScott
Well-Known Member
On one hand, yes, chances are we'll find new ways to make energy storage solutions that soundly improve on lithium.
But, as the original video states, we've already discovered the basic elements: we're not finding any hidden new elements/chemicals that are lighter or more efficient unless we totally misunderstand how the universe works.
We can devise alternative ways of extracting energy from materials, but will that really be a battery?
The long term issue is high density, useful, energy containment, not just chemical generation of electricity. I expect that there will be significant advances that Scott and some of the other young HBAers will live to see.
Here is a plea for taking some of your money (if you live in the USA) for reasearch into plasma containment. https://phys.org/news/2013-04-plasma-device-revolutionize-energy-storage.html
Another bit of science trivia here: https://www.csmonitor.com/Science/2014/0423/How-a-lab-accident-could-revolutionize-energy-storage
BJC
Here is a plea for taking some of your money (if you live in the USA) for reasearch into plasma containment. https://phys.org/news/2013-04-plasma-device-revolutionize-energy-storage.html
Another bit of science trivia here: https://www.csmonitor.com/Science/2014/0423/How-a-lab-accident-could-revolutionize-energy-storage
BJC
Yes, and prior to the late 1800's, scientists of the day had already discovered all the basic elements of flight, and determined that mechanical, heavier-than-air flight was a physical impossibility. And continued research found a way.
Some of the big pushes in physics today are in the way the "configuration" of materials can radically alter their physical properties. "Metamaterials", as only one example, can have physical properties vastly different than their component materials. There's no reason some similar discovery can't be found for energy storage. The field is extremely young.
"Will the energy storage device be a battery" is entirely a matter of sematics, and how you define the word. And really, does it matter? As prospective pilots of an a hypothetical electric airplane, are we really caring about the nature of the energy storage device? All we care about is that it stores enough energy for the airplane to perform its design mission, at a low enough weight to allow that mission to be possible. Limiting the boundaries of "what's possible" to "chemical batteries" is foolish, IMHO. A thousand years from now, anything we have today will seem as primitive as the technology of the year 1017 AD seems to us today. More so, since technology advances so much faster as it feeds on itself, allowing further and further reach. To claim we have such perfect current-day understanding of physics and engineering as to never permit significant advancement is high hubris, IMHO.
Someday, very likely in my own lifetime at the rate we're going, there will be an energy-storage device that will allow a practical "cruising" airplane. Will that storage device be a battery? Will it be a "supercapcitor"? Will it be something else as-yet unnamed?
I honestly don't know, and I honestly couldn't care less.
The Lithium-Air battery can in theory be up to 4 or five times the specific energy density of Lithium -ion. (Like the guy said in the video)
https://en.m.wikipedia.org/wiki/Lithium–air_battery
https://en.m.wikipedia.org/wiki/Lithium–air_battery
I once read an old Hot Rod (or similar) magazine from the 50's that discussed the ever increasing speeds of dragsters in the 1/4 mile. The article went on to "prove" (using math) that the absolute limit for tire driven acceleration in 1/4 mile was 167 MPH.
How'd that math work out?
How'd that math work out?
ScaleBirdsScott
Well-Known Member
Only reason I bring up battery as a semantic point is the video from the OP makes it's assumptions basically on that premise.
I agree with you about the ability to make a better power source will be the important thing and considering the limitations of a battery as defined is purely semantics and no one cares whether the source is a pile of lithium or some other mechanism. The point being, the only argument the video makes is that we can reasonably predict the limits of current battery tech as a battery is defined. In that way I feel the video and thread topic is what is hinged on that semantic point.
It's also a good point on the metamaterials, carbon is looking very promising and being atomic number 6 isn't too shabby in terms of potential power density.
Electric to Steam? Simple hot water heater element.....Now there is a storage device, also as is used up one is not carrying the water around. Light weight composite tank, diamond orifices and valves, and at least 150 year old technology. No guts no glory.
Steam has its advantages, as it can unleash absolutely massive energy for short periods without overheating the drive components, like 3 pounds of steam contains enough energy for a Dodge Viper to do a quarter mile drag.
The problem is that steam tech is still very limited and has not taken advantage of new tech. There is no reason, because it has no advantages to fixed industrial installations.
The biggest problem with steam engines is the condenser and heat exchanger.
