Could you create a battery powered plane?

  • #1
Robert Hearne
6
1
After watching a video on YouTube, I recently became interested in the dynamics and physic's of why we aren't using electrical powered planes instead of burning thousands of fossil fuels every day. After doing a bit of my own research, I found the problem. When we increase the weight, we have to increase the lift. Which would require more power. Needing more power means we need more batteries. Contradicting itself, meaning we would increase the weight, then increase the power, and have to go back and forth in a never ending cycle of power and weight.

I think what scientist are looking at is trying to find a more efficient type of engine that can sustain a high power while still being light and not using a lot of energy. In this scenario I'm not super concerned about the flight time being more than an hour. And I am no scientist myself, just a person with an interest in aeronautical engineering. So my knowledge of batteries and how they work is pretty off; but I definitely enjoy learning and I was wondering if anyone could give me a summed of version of the problem at hand here. As to why scientist aren't looking at making lighter or more efficient batteries.
 

Answers and Replies

  • #2
Drakkith
Staff Emeritus
Science Advisor
22,062
6,145
I think what scientist are looking at is trying to find a more efficient type of engine that can sustain a high power while still being light and not using a lot of energy.

Perhaps, but the main problem with batteries is that they aren't particularly energy-dense. The energy density of jet fuel is much greater than batteries, which is why modern airliners can fly thousands of miles without having to refuel.

According to this wiki article, jet fuel is about 20-40 times more energy dense than lithium-ion batteries. This means that you need 20-40 times more mass in the form of batteries to get the same energy as you do from jet fuel. This also corresponds to a comparable increase in volume as well.

I was wondering if anyone could give me a summed of version of the problem at hand here. As to why scientist aren't looking at making lighter or more efficient batteries.

They are. It is a very active area of research. It's just really difficult.
 
  • Like
Likes sysprog, Klystron, russ_watters and 1 other person
  • #3
Robert Hearne
6
1
Perhaps, but the main problem with batteries is that they aren't particularly energy-dense. The energy density of jet fuel is much greater than batteries, which is why modern airliners can fly thousands of miles without having to refuel.

According to this wiki article, jet fuel is about 20-40 times more energy dense than lithium-ion batteries. This means that you need 20-40 times more mass in the form of batteries to get the same energy as you do from jet fuel. This also corresponds to a comparable increase in volume as well.



They are. It is a very active area of research. It's just really difficult.
Are you aware of any websites or files that may have any valuable information on something like the research they are doing on making batteries more efficient? To my understanding, that's why this whole "electric plane" concept contradicts itself, is because using the modern batteries we have today we would need so many to meet the sufficient power. And by the time we met that requirement, we would need more because the weight would drastically go up. So I am interested to find something on the topic of making batteries way more efficient but haven't found much of anything that seems worth reading.
 
  • #5
jrmichler
Mentor
1,904
2,402
The Pipistrel Alpha Electro is FAA certified and in production: https://www.pipistrel-usa.com/alpha-electro/. Total flight time on a full charge is 1 hour plus 30 minute reserve. Not good enough to take on a trip, but very cost effective for training purposes and bug smashing.
 
  • Like
Likes sysprog, Klystron and berkeman
  • #6
cjl
Science Advisor
1,967
551
In addition to the jet fuel being very energy dense, jet engines are very power dense. For their size and weight, jet engines make an incredible amount of power, and electric motors tend to be much larger and heavier. Also, jet fuel gets consumed as it's used. This has the benefit of making the aircraft get lighter throughout the trip, allowing it to run more and more efficiently as the tanks drain. Batteries do not get lighter as they get discharged, so even if you had the same total energy available (and the same engine/motor efficiency), the jet would go further.

The one advantage batteries have is that electric motors are much more efficient than jets, but this is nowhere near enough to make up for the energy and power density differences in favor of the jets right now. If you could get batteries up to perhaps a quarter of the energy density of jet fuel, electric aircraft would become viable for a lot of the shorter trips out there, and if you could get up to half, it would become pretty competitive across the board.
 
  • Like
Likes sysprog and Klystron
  • #7
22,229
5,129
Jets are excellent at creating thrust. In the case of an electric engine for a plane, what type of thrust generation would be visualized?
 
  • #8
CWatters
Science Advisor
Homework Helper
Gold Member
10,545
2,317
Jets are excellent at creating thrust. In the case of an electric engine for a plane, what type of thrust generation would be visualized?
Most jet engines these days are high bypass types. Most of the air doesn't go through the engine core, it goes around it in a duct. So an electric "jet" would probabky be an extension of that concept eg a ducted fan.
 
  • #9
cjl
Science Advisor
1,967
551
As Cwatters said, a ducted fan that basically looks just like a jet engine but with the core replaced with an electric motor would be a good choice. The power requirements are enormous though, which is why I was talking about the power density of electric motors not being sufficient currently.
 
  • #10
jackwhirl
234
153
I found a Thesis on the topic. Mr. Bjarnholt's analysis follows the same general thinking mentioned above, with highlights of specific avenues for potential improvements.
---
You mention fossil fuels in your question. Is it fair to say that your interest in battery powered aircraft is out of concern for the environment? If so, let me offer some alternatives you might also find interesting:
 
  • #11
Drakkith
Staff Emeritus
Science Advisor
22,062
6,145
Airships (Seriously!)

Interesting. I'll have to look into how much fuel is required to move an airship versus an aircraft.
 
  • #12
Robert Hearne
6
1
I found a Thesis on the topic. Mr. Bjarnholt's analysis follows the same general thinking mentioned above, with highlights of specific avenues for potential improvements.
---
You mention fossil fuels in your question. Is it fair to say that your interest in battery powered aircraft is out of concern for the environment? If so, let me offer some alternatives you might also find interesting:
I will definitely look into that. Thank you for the information. And I guess you could say I'm looking into the environment. I've just always had a passion for aeronautical engineering and as technology progresses, I am not sure really what I want to do specifically or how I can make a difference. I wouldn't mind just working on and designing airplanes but I think it would be really cool to have an impact on the world. I'm looking into Embry Riddle after I graduate, but I'm only 17.
 
  • #13
Robert Hearne
6
1
The Pipistrel Alpha Electro is FAA certified and in production: https://www.pipistrel-usa.com/alpha-electro/. Total flight time on a full charge is 1 hour plus 30 minute reserve. Not good enough to take on a trip, but very cost effective for training purposes and bug smashing.
I've looked into that link and contacted them. Much appreciated! They sent me some files with all there information and it was very neat to look at. Now, I am curious if any of this could be dilated on a much bigger scale for passenger and commercial planes.
 
  • #14
boneh3ad
Science Advisor
Insights Author
Gold Member
3,379
1,123
There are a lot of problems for electrical airplanes large enough to carry people, but there was a group that build a pair of solar-powered planes called Solar Impulse that ran on battery power through the night. That's as close as I can think of to actually doing this.

There was a NOVA episode about it, too, though you can't watch it unless you are a subscriber.
 
  • #15
Robert Hearne
6
1
There are a lot of problems for electrical airplanes large enough to carry people, but there was a group that build a pair of solar-powered planes called Solar Impulse that ran on battery power through the night. That's as close as I can think of to actually doing this.

There was a NOVA episode about it, too, though you can't watch it unless you are a subscriber.
I've looked into the Solar Impulse, but I'm more interested in something that is only battery operated. Finding a type of battery or batteries that can sustain enough energy to power an aircraft for a full flight and be recharged after landing.
 
  • #16
CWatters
Science Advisor
Homework Helper
Gold Member
10,545
2,317
The energy volume density and the energy mass density of batteries is a problem for electric cars let alone planes. Cars really need batteries to improve by a factor of 4 to solve most of their issues. Hate to think how much they need to improve to make something like a short haul 100 seat airliner viable. Perhaps a factor of 100 or more? Someone must have written a paper on this?
 
  • #17
Robert Hearne
6
1
The energy volume density and the energy mass density of batteries is a problem for electric cars let alone planes. Cars really need batteries to improve by a factor of 4 to solve most of their issues. Hate to think how much they need to improve to make something like a short haul 100 seat airliner viable. Perhaps a factor of 100 or more? Someone must have written a paper on this?

Pipistrel created a two seater electrical plane. I have contacted them and asked for some information which i have received and looked into. Here is the link that I received : https://www.pipistrel-usa.com/alpha-electro/
 
  • #18
gleem
Science Advisor
Education Advisor
2,045
1,465
Not only is energy density an issue in batteries an issue of batteries but also charge rates so that a vehicle can get moving again in a reasonable amount of time.

There are new approaches to battery design such as the nano electrofuel flow battery It promises to help with both problems. It promised an increase in energy density by a factor of two up to 750 whr/kg. Recharging is accomplished by exchanging the charged fluid in the battery which would be like filling the fuel tanks of a conventional aircraft. An additional benefit is the recharging i.e.,exchange of fluids, seems to have minimal affect on the life of the battery.

http://aviationweek.com/future-aero...m=email&elq2=e245fe4e69784587b19b08bfe5c0f5c0

The podcast below discusses the current state of the electrification of aircraft. Although purely electric power may only be relevant to smaller aircraft its use in hybrid form with turbines offers great possibilities.

http://aviationweek.com/future-aerospace/podcast-leading-edge-electric-propulsion-hypersonics

One manufacturer is getting ready to test a 9 passenger full electric regional aircraft with Li-polymer batteries like the one used on Solar Impulse 2 that flew around the world.

http://aviationweek.com/awinbizav/batteries-ready-power-electric-regional-aircraft-says-eviation

You might want to subscribe to Aviation Week Daily Digest (free) for a summary of Aerospace news http://aviationweek.com/newsletters/signup to follow developments.
 
  • #19
cjl
Science Advisor
1,967
551
Charge rate is less of a concern with aircraft, honestly. You can charge most lithium batteries at 1C (1hr total charge time) pretty easily, and you can go a bit faster if you want, which is already in the range of commercial aircraft turnaround times. The power requirements will be tremendous of course, but the actual batteries are already capable of it.
 
  • #20
gleem
Science Advisor
Education Advisor
2,045
1,465
Charge rate is less of a concern with aircraft, honestly. You can charge most lithium batteries at 1C (1hr total charge time) pretty easily, and you can go a bit faster if you want, which is already in the range of commercial aircraft turnaround times. The power requirements will be tremendous of course, but the actual batteries are already capable of it.

I think the charging concern is primarily for the short hop urban commuter services where the aircraft turnaround has to be quick. Also isn't fast charging hard on the batteries and cause them to degrade faster?

One additional point in favor of E planes is that the operating cost looks to be much lower as low as $200/hr vs $600/hr for gas engines.much of which is due to the reduced cost of maintenance.
 
  • #21
lordvon
13
1
I think what scientist are looking at is trying to find a more efficient type of engine that can sustain a high power while still being light and not using a lot of energy. In this scenario I'm not super concerned about the flight time being more than an hour. And I am no scientist myself, just a person with an interest in aeronautical engineering. So my knowledge of batteries and how they work is pretty off; but I definitely enjoy learning and I was wondering if anyone could give me a summed of version of the problem at hand here. As to why scientist aren't looking at making lighter or more efficient batteries.

Lots of work is going into developing better batteries. "New breakthrough battery" headlines occur often, but a real breakthrough has to meet many criteria. I am no battery expert but here are some things that new batteries fail on: safety (resistance to spontaneously exploding after fatigue), capacity, max voltage, economics of production, charge rate, discharge rate.
 
  • #22
CWatters
Science Advisor
Homework Helper
Gold Member
10,545
2,317
Here is the scale of the problem..

The specific density of Avgas is much better than that of a modern battery. For reference..

BP Avgas 44.65 MJ/kg
Tesla Series 3 battery 168 Wh/kg or 0.6MJ/kg

To carry the same energy using Tesla Series 3 batteries instead of Avgas the battery would weigh 44.65/0.6 = 74 times as much.

A 747/400 carries 165,000 kgs of fuel. To carry the same amount of energy it would need a battery weighing 12,200,000 Kg which is totally impractical.

In addition the 747 gets lighter as it burns fuel so the power and energy required reduces as a flight progresses. The electric version would have to carry the weight of the battery for the whole flight.

Even if you adjust for the greater efficiency of an electric motor you still have a massive problem.

PS: I've been flying electric powered model aircraft since 1984. I think since then there has been a factor of 3 or 4 improvement in energy density. Even if energy density doubles every 10 years it might still take 50 years to match Avgas. It needs major push..
 
  • #23
etudiant
Gold Member
1,238
128
There is an effort currently in the UK to convert a small passenger commuter transport to electric power.
The aircraft flies an island hop route involving very short distances, so the range deficiency of electrics is less problematical.
A BBC report on the project is here:
https://www.bbc.com/news/uk-scotland-north-east-orkney-shetland-45876604

This is a reasonable next step in this development effort.
 
  • #24
gleem
Science Advisor
Education Advisor
2,045
1,465
We have been assuming that electric aircraft will be using Li - ion batteries or some equivalent and have neglected to consider fuel cells. The company Alaka'i Technologies is in the process of certifying a five person (incl. pilot) eVTOL and expects to complete the process by next year. It is a 4000 lb aircraft with inter urban flights as its main function with a range of 300 mi. It will carry 600 L of liquid hydrogen. With an energy density of 147 Mj/kg even at a 50% efficiency it is better than avgas.

https://aviationweek.com/future-aer...m=email&elq2=3dabbfddf7b546dd92a03834a361ed03
 
  • Like
Likes diogenesNY, russ_watters and CWatters
  • #25
36,170
13,161
We have been assuming that electric aircraft will be using Li - ion batteries or some equivalent and have neglected to consider fuel cells.
Well, the topic says battery powered.
Hydrogen has a great energy per mass but a poor energy per volume. It needs larger tanks (which have a mass, too). It also needs a cryogenic system or has to be kept under high pressure, increasing the mass again. It is still an interesting option to reduce CO2 emissions from air travel if the hydrogen comes from CO2-neutral sources.
 
  • Like
Likes russ_watters
  • #27
Check out Lilium, who have flight tested an electric jet, albeit a small one.

In terms of batteries, a metal air battery - perhaps Li-air or Na-air - can theoretically get close to fossil fuel levels of energy density but they are devilish to build and nobody has productionized one, so the jury is still out on whether this is practical beyond the lab.
 
  • #28
CWatters
Science Advisor
Homework Helper
Gold Member
10,545
2,317
Quite a few companies are working on drone like air taxis. However conventional wisdom is that planes are more efficient than helicopters.
 
  • #29
russ_watters
Mentor
21,950
8,984
Quite a few companies are working on drone like air taxis. However conventional wisdom is that planes are more efficient than helicopters.
Short and slow trips like that are the only domain where electric air travel is ever likely to be feasible because the energy requirements are low. Also, as far as I know, there's no such thing as an electric jet, so large and fast passenger aircraft are likely never to be electric powered.

Hydrogen is a potential solution; not as a carrier of clean electricity, but a carrier of clean combustion.

I don't see anything particularly problematic for hydrogen passenger jets. The main practical problems are the cryogenics and volumetric energy density, both of which decrease as the size of the plane is increased.

The main obstacle is cost.
 
  • #30
essenmein
657
295
Check out Lilium, who have flight tested an electric jet, albeit a small one.

In terms of batteries, a metal air battery - perhaps Li-air or Na-air - can theoretically get close to fossil fuel levels of energy density but they are devilish to build and nobody has productionized one, so the jury is still out on whether this is practical beyond the lab.

Metal air batteries while technically interesting are in no way a solution to any power source where CO2 reduction is the goal. The battery it self may not produce CO2, but "recharging" it absolutely does, and a lot of it.

Aluminium + oxygen (from air) = Al2O3 + electricity (In reality a bit more complicated, but basically the idea)

then to get that Aluminium back:

2Al2O3 + 3C + electricity = 4Al + 3CO2.
 
  • #31
cjl
Science Advisor
1,967
551
Quite a few companies are working on drone like air taxis. However conventional wisdom is that planes are more efficient than helicopters.
I'm not sure I'd call that conventional wisdom so much as a nearly inevitable consequence of the different ways aircraft and helicopters make lift.
 
  • Like
Likes russ_watters
  • #33
Metal air batteries while technically interesting are in no way a solution to any power source where CO2 reduction is the goal. The battery it self may not produce CO2, but "recharging" it absolutely does, and a lot of it.

It is an aspect of metal-air that is usually ignored, for sure, @essenmein. The focus on energy density is the single goal, the CO2 generation is rarely discussed. I'm not bullish on them in any event, controlling the oxidation so the materials do not quickly degrade appears to be an intractable problem.
 
  • #34
etudiant
Gold Member
1,238
128
The offset to the CO2 generated during the battery recharge is that the overall internal combustion energy efficiency is abysmal, well under 10% for cars. That gives battery powered vehicles a huge leg up, even if the charging process is inefficient.
 
  • #35
cjl
Science Advisor
1,967
551
The offset to the CO2 generated during the battery recharge is that the overall internal combustion energy efficiency is abysmal, well under 10% for cars. That gives battery powered vehicles a huge leg up, even if the charging process is inefficient.
No, most cars are on the order of 20-25% efficient, with peak thermal efficiencies on some modern engines getting up into the 40s.
 

Suggested for: Could you create a battery powered plane?

  • Last Post
Replies
6
Views
1K
Replies
16
Views
2K
  • Last Post
Replies
11
Views
2K
  • Last Post
Replies
0
Views
114
Replies
1
Views
452
Replies
5
Views
172
  • Last Post
Replies
5
Views
744
Replies
2
Views
537
Replies
7
Views
514
Replies
19
Views
780
Top