Why battery-powered aircraft will never have significant range

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Dan Thomas

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With our current understanding of aerodynamics, this indicates that battery powered airplanes should all have long skinny wings and egg shaped fuselages, and amazingly... that's what they look like. In contrast with all the Unobtanium wannabee tech stuff we see every day, all of the common sense and data on energy density perfectly support the current (glider-looking) electric airplane designs, and the actual flight results on these airplanes prove out that they work to a modest degree.
They're the same shape they'd be if they had to fly on a 20-hp lawn tractor engine. Like a motorglider. Nothing new here at all, like you say.
 

Dan Thomas

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The electric propulsion has 2 characteristics that might be really valuable, besides 'green craze':

- high power to weight ratio for the electric motor: this means that for a short 'hop' the propulsion system might be lighter than conventional ICE. Think case that the aircraft needs to fly only 20 - 30 minutes ( e.g. commuting to work)
The electric motor is called a "motor" because it converts energy into motion. An ICE is called an "engine" because it has to make that energy by chemically converting fuel into heat. Now we run into some inconvenient facts that have been addressed before:

Storing electricity costs weight, and has safety issues for some battery types. Electricity storage is a lot heavier than chemical (gasoline/diesel) storage and it's much slower to "refuel." Electricity generation, which has to happen somewhere before you can charge those batteries, has a whole bunch of efficiency losses between generation and its conversion into motion, so the electric is not innocent of wastage.
 

dog

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The electric motor is called a "motor" because it converts energy into motion. An ICE is called an "engine" because it has to make that energy by chemically converting fuel into heat. Now we run into some inconvenient facts that have been addressed before:

Storing electricity costs weight, and has safety issues for some battery types. Electricity storage is a lot heavier than chemical (gasoline/diesel) storage and it's much slower to "refuel." Electricity generation, which has to happen somewhere before you can charge those batteries, has a whole bunch of efficiency losses between generation and its conversion into motion, so the electric is not innocent of wastage.
Ya we know all that.
Its just that this thread very inconvienienly
labels battery electric as happening never.
So ICE is dead developmentaly,going nowhere
fast.Physics ya know,efficiency maxed out for ICE,fuel dangerous and imcreasingly unpopular,
did you just say lead? pouring down on all the inocent little taxpayers.
And electric I planes are an inevitability.
Check the date ,2021.The battery problems are
bieng addressed apace.Good news every day.
One of the key technologys just starting to have a profound impact on the development
of many things is the ability to image in real time what is happening at the atomic scale.
And a very recent development of an optical
microscope that has nearly the same power as
an elecron microscope is going to make development that much more affordable and
quicker,no need to pull a vacume etc.
And its a tide that floats all boats,so maybe just, there will be a new ultra super perfectium
that will stand up to 100/1 compression ratios,and burn so hot that instead of CO and CO2,it will rain down little diamonds.
Hope that makes you happy.
 

Dusan

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Canada
Electricity storage is a lot heavier than chemical (gasoline/diesel) storage ...
That is not quite true: a gasoline ICE engine uses about 15 pounds of air for every pound of gasoline burned. Luckily the air is not needed to be stored on board the aircraft. Current batteries store all the reactants inside.

Electricity generation, which has to happen somewhere before you can charge those batteries, has a whole bunch of efficiency losses between generation and its conversion into motion, so the electric is not innocent of wastage.
It is much more effective to produce electricity at a coal power plant - efficiency about 60%; transmission, conversion, charging batteries, discharging, conversion for the motor, everything is close to 90% - than to use an ICE and burn gasoline at 30% efficiency. This assuming electricity is produced by coal only. Also the gasoline needs to be refined and transported to the pump, and transporting fuel is much less efficient than transporting electricity.
 

BBerson

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My last sailplane (1980's technology) had a 45-1 L/D with the long wingtips on it. The airplane carried 40 gallons of water ballast, which would equal the weight of a pretty large battery. At 1102 pounds gross weight, that means less than 25 pounds of thrust would fly it in that condition, at about 60 knots. One of you genius-level guys can estimate how big of a battery/motor combination it would need to take off, climb to a thousand meters, and then cruise at that max efficiency for X miles. I'm guessing that 250 pounds of battery and 60 pounds of motor and prop would deliver a lot of range.
It isn't that easy to take a pure sailplane and add an engine for efficient flight. Sailplanes are generally heavy per seat and adding an engine, prop and three wheels makes it far heavier. To climb at a high rate you need significant hp. That's why tow planes have big engines. We don't see many large motor gliders for high speed cruising. Too rough and the wife will not go a second time.
 

Dan Thomas

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It is much more effective to produce electricity at a coal power plant - efficiency about 60%; transmission, conversion, charging batteries, discharging, conversion for the motor, everything is close to 90% - than to use an ICE and burn gasoline at 30% efficiency. This assuming electricity is produced by coal only. Also the gasoline needs to be refined and transported to the pump, and transporting fuel is much less efficient than transporting electricity.
That coal has to be mined and transported. It has to be moved into the plant, and the coke removed. That's plenty of loss right there. The spent steam has to be cooled to condensation for pumping back into the boilers. More lost energy. Besides that, when you take 90% of something that's 90% efficient, you end up with 81%. Do that a few more times, representing each stage of power delivery and conversion, and you don't have much left. So everything involved has to be very efficient, and that costs lots of money.
Lost In Transmission: How Much Electricity Disappears Between A Power Plant And Your Plug?

Yes, I know, oil has to be extracted, transported, refined, and the resulting fuel transported as well. It involves losses at every stage. I'm merely pointing out that the proponents of electric vehicles are either ignorant of the sources of power and the losses entailed, along with various sorts of pollution, or they're conveniently avoiding those issues because they hurt their cause.
 

Dan Thomas

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And electric I planes are an inevitability.
Check the date ,2021.The battery problems are
bieng addressed apace.Good news every day.
Hope that makes you happy.
It does not make me happy. The stuff you are citing is from sources that have suspect motives. We have already addressed the limits of battery technology, limits that will take some fantastic new technology to resolve, and fantastic new technologies are not known for being inexpensive or for their immediate availability. This is not the digital world, where Moore's Law says that the tech doubles every two years or something. Your computer doesn't have to fly. Nor does your cellphone. Flying demands LOTS of energy, not a 3 GB processor.

Wishful thinking will not get you an electric airplane.
 

John.Roo

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Letohrad / Czech Republic
Obviously, there are here two hardly reconcilable groups.
ICE vs EM.
Both teams have logical arguments based on their preferences, experience and requirements.

I would like to say that each team can stay on their side.... however decission about future aviation propulsion systems is not on us. Most of arguments here are valid and we could apply same arguments on electric vs ICE cars.
So if it is logical and obvious that electric propulsion systems are not ecological, heavy, long to re-charge etc. why do we see governament step by step making life of "normal" car owners difficult? This has nothing to do with logic or ecology.
Do you beleive that AVGAS or MOGAS will be available forever because governament gets money from each gallon? Australia (Victoria state) is nice example that you can get good money also from electric cars just applying tax/fee on each km.
  • Road-user charge of 2.5 cents/km for zero emissions cars and 2 cents/km for plug-in hybrid cars starts on 1 July.
.

Sport aviation is actualy in ""shadow".
For example AVGAS is the only remaining lead-containing transportation fuel.
Old planes are burning gallons of this fuel and nobody really care. How long?
Change to MOGAS? Possible, but did you noticed some catalyst system installed in exhaust on Rotax engines? 915iS has fuel consumption over 40 litters of MOGAS / hour on full power. Really? This consumption will be acceptable today when car producers are forced to report totally unrealistic fuel consumptions and super low emisions?

I personally don´t beleive that pilots are as a group politically strong enough to keep actual status quo forever.
Don´t understand me wrong - I would wish to use 80-100 hp Rotax engine forever (reliable, low fuel consumption, easy to maintain) but this is just not realistic. Changes in automotive industry will affect aviation - before or later. We can accept that and try to do something or we can enjoy current "sport aviation friendly time" and wish that this prediction was wrong...
 

dog

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Battery teck is close to bieng viable for some
aviation aplications.
Things like a 600kw electric fuel cell in a Piper
Malibu might put an end run around battery and ICE all in one move.Thats turboprop power
at turboprop prices,which for a first iteration gives huge room for improvment in cost and performance.
Currently batteryies are improving at about 5%
per year,or more over the last 10 years.
And it is entirely within the realms of possibility
to expect that radical improvments of five,ten,
or 100 times the current energy density,especialy with a capacitive storage system.Moores law is pesimistic if applied to
energy density over the long haul.
ICE got nothing more to give,just going to get more expensive,more regulated,less popular,
an industry with huge wealth and power left
facing its own inevitable replacement without
the good grace to help the sucession of societies energy needs along.
The universe is an energy gradient.
There is more power in more forms than any
ambition can use,and we are just getting some
direct access and control of that.And as impatient as I am to have some for ME NOW,
I know that its likely to cause all kinds of trouble.
Funny how bits of the Pyramid texts and the Epic of Gilgamesh and other ancient writings
are pertinent to our times.
Everything and nothing changes.
 

Appowner

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I remember the big hoopla 20 years ago about "it" coming and changing the way we moved around. "Bigger than the internet," they said. The Segway. And how big did that go over? Finally died last year. I'm either living in some remote part of the world, or there were never many takers for it. Other than in videos, I've seen them used exactly once, a group of four or five being rented by tourists.

Hoopla. Hype. We all fall for it until we get old and experienced enough to spot baseless claims and start being skeptical. At least most of us reach that point. Some can be fooled endlessly.
OK, a short aside. I spent a lot of time in Bethesda Naval Hospital (Cancer). Bethesda is the main hospital for military amputees treatment and recovery among other things.

One day as I sat in the main lobby I watched a Quad amputee (yes, all four of them) cruise by on a Segway. Inspirational to say the least.
 

Appowner

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nuclear batteries. not sure if this is an April 1st video or not.
Interesting concept. But does this mean instead of storing the deadly waste in a single location we'll end up storing tiny bits of it all over the world?
 

patrickrio

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Aug 15, 2020
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Some other areas that are different with electric aircraft that may end up adding to their efficiency in comparison to IC aircraft:

1. weight and thrust location variability. Since the motor weighs very little, and can be located very separately from the batteries, weight and thrust location are not tied to each other like in IC engines. Thrust can be located to reduce effect on laminar flow and also potentially still avoid turbulent air in front of prop more easily than IC. Weight can be located wherever it needs to be to make airframe part locations like wings and pilot pod more efficient.

2. it is easier to drop propeller rpm using less weight increase and without losing other efficiencies using electric motors as compared to IC. You might be able to use a very large diameter prop turned at 400rpm, for example. Already done on sunseeker 2 but not really investigated fully for low HP motor applications yet.

3. Motors have less vibration and force pulses than IC. Thinner, less structurally robust props and drive trains (if you even have one) are possible... as well as larger prop diameters.

4. Easier to put a variable speed prop on something with less pulse/vibration and turning lower rpm... and just easier in general to locate necessary variable prop mechanics near an electric motor.

5. cooling drag loss can be dramatically reduced from IC installations... especially as batteries evolve to need less cooling and motors get more energy efficient with lower hp needs.

Based on utilizing the above to best effect, I suspect that a high efficiency electric motor aircraft will end up having some noticeable differences from both gliders and IC aircraft once their benefits are maximized.
 

TLAR

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I live by two very large lakes formed by building dams across the Tennessee and Cumberland rivers.
I wondered when skiboats would go electric.
Sure enough Nautique has developed an electric version!
It will be nice to hear silence and hulls slapping the water
Oh, the base price is $292,000.
Stick electric up your ass
 

TLAR

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The shift from ff to electric is all about shifting mass amounts of money from one group to another group.
Wealth redistribution.
It is purely a Money grab.
 

DennisK

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Location
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ICE got nothing more to give,just going to get more expensive,more regulated,less popular,
an industry with huge wealth and power left
facing its own inevitable replacement without
the good grace to help the sucession of societies energy needs along.
Actually ICE does still have plenty of room for improvement, they've just been complacent because they had a highly profitable business with little competition. Opposed piston engines are one interesting category for further R&D. And there's a company called Alfadan that's working on a new 4 cylinder inline with higher displacement than has been possible thus far, due to a dynamic balancing issue caused by asymmetry of the up and down strokes of the cylinders with simple connecting rods to the crankshaft. The youtube channel "driving 4 answers" has a good video on it.

On the electric side, there's an interesting company called FreeLTech which has achieved 7.5kWh/kg and 62kW/kg, and may be able to reach 20kWh/kg. Sounds too good to be true, but they're probably not lying. Though we'll probably never see it either, because the physical mechanism that it's based on has been independently discovered many times over the past 100 years and every time it gets buried again. They call it "charge clusters", but everyone who discovers it gives it a new name. Ball lightning is the naturally occurring version.
 

Dan Thomas

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...why do we see governament step by step making life of "normal" car owners difficult? This has nothing to do with logic or ecology.
Political pressure from climate change activists. They demand an end to fossil fuels right now, not understanding the devastation of such a move. For one thing, it would leave a country with a badly disabled military, and guess what comes of that? The UK is committed to all electric military stuff ASAP. Tanks, planes, everything. Tell me how that makes sense.
 
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