Why battery-powered aircraft will never have significant range

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mrinnovation

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Hard to compare anything electric to petroleum. Just one of my trips for the weekend to the drag strip with my cars uses enough energy to make at least one complete bank of batteries (about 60GJ each), that then lasts over 20 years, and can and are being recycled. The electric motors in a Tesla are between 85 and 95 percent efficient compared to my turbocharged V-8's (1UZ-FE) I build running at 25 percent. Only one quart of fuel out of each gallon of gasoline actually is used to produce kinetic energy to roll my car forward, the other three quarts go out the tailpipe as heat and unburnt hydrocarbons. In my Diesel pickup I roll coal all over the place, love it, but once again, each gallon of diesel I burn doing this is equivalent to an entire weeks worth of commutes in a pure electric assuming it is being charged off solar panels on the persons roof. The fact that my engines also need oil in the crankcase, grease, coolant, and contain hundreds of parts versus a modern three phase permanent magnet motor which only has three moving parts, lives about 2 million miles between bearing replacements, and can be rebuilt in an hour using about $150 in parts just adds tot he sillyness of my love of engines.

I won't even get into the amount of damage prospecting for oil, and drilling, refining, distributing the final product produces, but it's in the trillions of dollars per year globally. Every time I hop in my Skyhawk I see the result of a world hooked on petroleum. The skys in my town (Phoenix) can barely be seen through in a plane, even they were clear as a bell in the 70's and 80's. Then the fact that the government also subsidizes the richest industry in the world for hundreds of billions of dollars each year just adds irony to an already hilarious situation. Nah, I'm not going to delude myself, even as a hotrodder, engine junkie, high performance diesel freak, and fast plane nut that any of this is good for anything but my enjoyments. I am certainly not going to defend or support Arabic countries that have supplied most of the oil I have spewed out the tailpipe of any of my hotrods over the last 50 years. Nor am I going to delude myself in to thinking that going to war with any of these countries had anything to do with defense, but rather control of resources.
 

tspear

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There is a time to innovate, but there is also a time to renovate. Innovation that causes far more damage than the status quo (and in this case I mean LiPo batteries and the idiotic idea of putting a ton of batteries in a light airplane just to do a virtue signalling move) is hardly advancing anything except the pollution from rare earth mining and the fortunes of those who speculate in these information (read propaganda) driven markets. We can safely advance by doing things (such as STOP killing off the oceans) that we know - but not being herded like the sheeple from the interwebs to demonize carbon.

When we ignore the science and embrace the technology, I don't call that smart or moving forward.
It is called destructive innovation.
As for batteries, sure they do not do the job now for anything but simple training (even then are currently marginal but do work). But consider the number of technical issues which need to be resolved outside just the energy storage.
Even electric motors need cooling, you need to perform failure analysis and failure mode redundancy for the rest of the power train system.

When you read about the majority of non-dreamers and people advocating electric planes the following is the list of reasons I see most often:
  1. Reduced complexity, MIF is the largest non-pilot category of failures in a plane. EV has the potential to eliminate significant portions of this category.
  2. EV has the potential for much lower OpEx. Note: The current battery tech replacement on most of the available planes is slightly more expensive than the ICE counter part
  3. If you are really interested in the environment, then short term switch to a bio fuel with an ICE engine. There are plenty of choices, most of which will burn lots of cash while you are at it.
Tim
 

Vigilant1

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2. EV has the potential for much lower OpEx. Note: The current battery tech replacement on most of the available planes is slightly more expensive than the ICE counter part.
Hmmm. "Slightly more expensive"?
The last time I ran the numbers, the per-hour amortized cost of the Pipistrel Alpha Electro battery replacement was more than the per hour cost of the Rotax overhaul for that same plane AND all the fuel burned per hour by that plane. Yes, there will be other periodic maintenance costs for the Rotax, but we are also disregarding wear on the electric motor and we haven't paid for the electricity it uses, either.
And that's if the $21,600 battery lasts 700 hours. Pipistrel says we should expect it to last 300-700 cycles. Present users are getting 40 minute cycles. So, the real expected cost just for battery replacement is $46 to $108 per flight hour. That alone should close the issue for anyone running a real flight school in the US who might have considered these electric planes.

At least in this single real-world case, I don't see how the operating expenses in the US are anywhere close to comparable. And the utility difference of the two aircraft is considerable, if we have any plans to leave the zip code where it is based.
 
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8davebarker

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I'd like to ask a question of anyone who has a better technical understanding than I do about nuclear power (nuclear power to generate the electrical power that recharges our homebuilt aircraft batteries, of course).

I understand that one of the biggest issues is cooling the reactor, keeping the heat under control and transferring it safely out of the system.

So most everyone built nuclear plants near the ocean, or some big river system, and use the large bodies of water as the medium to absorb the heat out of some kind of heat exchanger. But as we saw in Japan, the ocean can get angry and cause some major issues.

If you built a reactor cooling system that used a much larger version of a finned "heat sink" (like what is used to cool computer processors) as the final stage of transferring the heat out of the powerplant... essentially an air cooled heat exchanger... just how big would that final heat exchanger have to be for an average sized nuke power plant? 500 x 500 feet? 2000 x 2000 feet? A square mile?

My idea is that a nuke plant in the middle of the desert would be able to take advantage of almost any size solid state air cooled heat exchanger that was required. If you had half a square mile's worth of steel or aluminum cooling fins radiating 150-180 degree heat into the air, you would be able to reject an awful lot of the excess heat.

Tsunami's wouldn't hurt it, and if it was designed properly an earthquake wouldn't hurt it either. You would have a lower number of failure points or brittle solutions. Even in the event of some unforeseen catastrophe, you'd be out in the middle of the desert, instead of near a major population center (you'd poison a bunch of rattlesnakes and coyotes, but you wouldn't kill ten thousand people, or wreck the world's supply of fish, etc.).

We are blessed in the western USA to have an abundance of uninhabited desert, where this would be viable. The land cost is still very low compared to anywhere near a coastline as well.
There are numerous fail safe nuclear power plant designs. Most of which could be located virtually anywhere. The thorium based reactor uses a fan across a small heat exchanger in the molten thorium fluoride salt circuit. In case of emergency or power failure, the fan stops, the frozen thorium salt melts in the heat exchanger and drains into long thin vertical holding tubes. Reaction stops. Also the thorium reactor uses 95% of its fuel. Leaving just a few relative short lived waste products. ( today’s reactors use ~1% of their fuel)
My favorite it the Uranium Hydride reactor. it uses hydrogen gas circulated across uranium pellets. The hydrogen gas slows neutrons which increase the reaction rate. The hydrogen circulates from gas to hydride continuously .The hot gas is used as the working fluid for a turbine or perhaps MHD The plant is small, could be located in a the basement room of a shopping center. When a Terrorist fires a bazooka thru the reactor, the hydrogen vents. ( you can’t make hydrogen radioactive) and the what is left of the reactor shuts down. Because the hydrogen is missing.
There are many other good designs out there. Unlikely any will see the light of day in our ultra left political environment.
 

tallank

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What really makes me scratch my head (and that is easy as there is no longer much hair in the way to blunt effect) is that in a business and hobby where we fret about ounces - or careless people whole pounds - anyone at all would seriously discuss a power delivery system that costs TONS in extra weight to do what the currently available hardware does already?????

Secondly: in a community of people who are analytical by description - why doesn't anyone bother to mention the environmental costs of producing the ever-off-in-the-distance battery technologies that now depend upon rare earth metals that don't even have the known reserves to run all of the projected electric cars that governments are subsidizing into being????

When engine technology is as advanced as it is (and in ground transport is sure as heck IS extremely sophisticated) we can eschew this ridiculous trend of trying to virtue signal in our designs and work to simply focus on making far more efficient both aerodynamically and thermodynamically the things we all know so well work to do what we do?

From an hard core environmental perspective - demonizing carbon is really only an issue when we ignore that the real problem is that we are destroying the ocean's ability to fix carbon in it's natural cycle. While we shouldn't look at releasing more carbon, we should look at absorbing what we COULD absorb by stopping our efforts to screw up the carbon sink that can easily manage at least a globally sustainable level.

If we DO want to stop carbon emissions from our sources, the solution IMHO is to use liquid hydrogen as a fuel - VERY good energy storage density and easily burned in either spark ignition and/or compression ignition engines. Of course, sourcing the H2 will require some green-ness, thinking PV is best.
I was very impressed with your first couple of paraphs until I read the last two. CO2 is a nothing burger for the atmosphere. 93% of the green house gas is water vapor. The "man made CO2" is a small fraction of a percent. Hydrogen IS NOT A FUEL. It is just like electricity, has to be produced and the most efficient way to do that is using Natural Gas. Fuel cells are 40% efficient. It takes energy to produce Hydrogen and then compress it to store it in high pressure tanks. A side note, these tanks can not be steel which the hydrogen will make the steel brittle. Might as well use diesel engines that are 33% efficient.
 

patrickrio

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At a few points earlier in this thread, It has been noted that Radio Control aircraft using electric power are already more powerful, less expensive to buy and operate, and stay in the air longer than their IC versions.

It is also likely that for the light end of gliders that sustainer and self launch capability can now be done less expensively with electric power... The engineering to combine the existing technologies into the best performing inexpensive packages is all that is keeping electric power from widespread adoption for these uses in a manner that reduces IC use for the same task to about nothing. Electric is just going to be better for this.

I suspect that the limitations on US FAR103 ultralights - like the limitation to 5 gallons of fuel - also puts electric right in the vicinity of IC for most styles of flying done in current powered FAR103 airplanes. The things holding back adoption are just the engineering tasks and cost of engineering the best performing electric power packages for the various ultralight flight desires. And also modifying the airframes to use the weight and balance of the batteries to advantage (they can go to almost any extreme corner of the aircraft where they can help) as opposed to the need to keep the changing weight fuel tank located to minimize flight characteristic change. I bet someone will even figure out how to USE the battery weight as a moving mass to improve flight with different pilot weights and even improve flight performance during flight with speed variations, flaps, flight trimming etc.

I think that the current official unrefueled distance record for FAR103 aircraft limited to 5 gallons was set in the 1980s by a Mitchell Wing... I think it is a bit over 300 miles. I bet that someone is shortly going to break this record in an electric powered FAR103 aircraft. It probably won't last more than 5 more years. That plane will likely be easier to fly than the Mitchell Wing, and have greater reliability. It might even make shorter Hamburger Runs something you could do with meal tip size pocket change.... It's initial purchase cost is going to be more - but that is mainly because there are thousands of serviceable IC ultralights sitting unused and ready for someone to buy at liquidation pricing.

BUT for sure, in this class of aircraft, in the not too distant future, the plane with the MOST SIGNIFICANT range will be electric powered. Some lightweight SkyPup owner out there could break this record with one month of time investment and under $3000.

And after this, electric is just going to slowly move into heavier and heavier airplane types as the best option available.
 
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Toobuilder

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RC models, cell phones, self sustainer gliders and 103 types continue to be pointed to as "success" stories for electric. While they are certainly popular among this forum, in reality they are all an example of niche, "toys". A huge segment of the E-AB population is comprised of airplanes designed and used as "transportation" - i.e. Hauling people and things long distances in minimum time. My intimate aviation social circle is probably 20 pilots strong and I cant think of a single one that has a 103 or a glider. ALL of us load up our airplanes with people and stuff and leave town or commute on a regular basis. So great - viable electric 103 or LSA are right on the cusp... "When" can I replace the 540 with electric in my Rocket and still do 750 miles per leg with a 10 minute energy replacement turn, while cruising 200 KTAS and hauling my wife and 100 pounds of "stuff" for a weekend getaway?

How far away are we from the "real airplane" cross country homebuilt mission with electric? Lots of RV, Lancair, Velocity, Berkut, BD-4, Cozy, Glassair, Rocket, Baracuda and GP-4 owners are wondering.
 

BBerson

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Guy in my RC club keeps a log on his batteries. Average is 80 flights before they degrade below his needs.
 

mrinnovation

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How far away are we from the "real airplane" cross country homebuilt mission with electric? Lots of RV, Lancair, Velocity, Berkut, BD-4, Cozy, Glassair, Rocket, Baracuda and GP-4 owners are wondering.
I remember my dad back in the 70's saying we would have flying cars by now, control of gravity, cure for cancer etc. The problem is in my field (Mechanical and electrical engineering) we almost always take the quickest, and most profitable route on any product being designed. Investors want a quick return on money without lengthy R and D cycles of what my investors call "disruptive technologies" or ones that eliminate a good portion of the current economy (Oil, etc). If we had kept to electric back in the early 1900's when cars were already electric (some of the first cars were electric btw), we would already have what you are wanting.

I predict ten years we will see a not only high enough power density in storage but also forms of mini-reactors that will make cross country plausible.
 

Hot Wings

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BUT for sure, in this class of aircraft, in the not too distant future, the plane with the MOST SIGNIFICANT range will be electric powered.
I'll take the other side of that bet.
Part 103 is a strange beast. Been down this path - electric part 103 - a long way. This is one area where energy density/mass of the 'fuel' is a VERY significant limitation due to the way the FAA currently considers battery weight for part 103. As is the math just doesn't work other than for a point design looking more like a MaCcready HPV.
Move up to a plane not limited by part 103 (or even LSA) performance standards and the job becomes much more likely............if range and not overall usability is the goal.

Between now and when we get the elusive 10x increase in battery energy density hybrid power is is the path to range and climb rate for planes with regulation limited performance standards.

Kramer needed the weight allowance for amphibious part 103s to make his work. His Lasair is good real world base from which to build.
 

patrickrio

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I'll take the other side of that bet.
Part 103 is a strange beast. Been down this path - electric part 103 - a long way. This is one area where energy density/mass of the 'fuel' is a VERY significant limitation due to the way the FAA currently considers battery weight for part 103. As is the math just doesn't work other than for a point design looking more like a MaCcready HPV.
Move up to a plane not limited by part 103 (or even LSA) performance standards and the job becomes much more likely............if range and not overall usability is the goal.

Between now and when we get the elusive 10x increase in battery energy density hybrid power is is the path to range and climb rate for planes with regulation limited performance standards.

Kramer needed the weight allowance for amphibious part 103s to make his work. His Lasair is good real world base from which to build.
I think you are likely wrong here, but the only way to know is for someone to do it. I think there is actually a likely fast path to break this record already:

Use an existing SkyPup as the platform. A carefully built SkyPup can weigh about 150lbs empty without the weight of the IC engine (propeller included in the 150lb weight). This means that you could have 104lbs available for motor and battery solution and still be below FAR103 max empty weight of 254lbs. It shouldn't be too hard to go even 400 miles in the SkyPup with an electric power package of this weight.

I think the appropriate course of action is to create a new thread in the "Lightweight" area where a discussion can be had to design the power package necessary and check it's plausibility as to accomplishing the task.

Essentially put the path to success complete with bill of materials, sourcing and cost on the internet to make it easy for some existing SkyPup owner to take up the challenge...
 

Dan Thomas

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RC airplanes have extremely low wing loadings. When you double the size of the aircraft, you cube the weight. That's why we've never seen a homebuilt with a big two-stroke engine that climbs straight up. Comparing electric RC to real airplanes is futile.
 

tspear

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How far away are we from the "real airplane" cross country homebuilt mission with electric? Lots of RV, Lancair, Velocity, Berkut, BD-4, Cozy, Glassair, Rocket, Baracuda and GP-4 owners are wondering.
Probably forty years at the current incremental pace for battery technology gaining 2-4% a year. Two significant unknowns:
1. Charging infrastructure
2. Some break through in energy storage tech. e.g. Solve hydrogen fuel cell thermal issues, solid state batteries, silicon super capacitor....

Based on the money going into #2; I think it will happen. Question is when.

Tim
 

PMD

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I was very impressed with your first couple of paraphs until I read the last two. CO2 is a nothing burger for the atmosphere. 93% of the green house gas is water vapor. The "man made CO2" is a small fraction of a percent. Hydrogen IS NOT A FUEL. It is just like electricity, has to be produced and the most efficient way to do that is using Natural Gas. Fuel cells are 40% efficient. It takes energy to produce Hydrogen and then compress it to store it in high pressure tanks. A side note, these tanks can not be steel which the hydrogen will make the steel brittle. Might as well use diesel engines that are 33% efficient.
There are other ways of making hydrogen from water, not needed (but is cheap) to do so from methane. I am not talking about CNG, I am talking about micro LNG. One of my best friends was the global lead in developing this technology for a Fortune 500 company, and one company I work with has been running aircraft diesel engines on it. They got involved since the project related was intended to use fuel cells, but the energy needed to operate and cool them was greater than the energy they could get by simply burning the H2 in a diesel.

There was another post in this thread about efficiency. SI gassers used to be down around 25%, but they now peak nearer 40% in most advanced designs - about where the average HPCR diesel is today. Cathedral diesels are over 53% thermal efficiency. I have a researcher friend who has run diesels at well over 70% BTE and his work predicts the theoretical limits are somewhere over 90% (with what will some day become public as a truly revolutionary bit of science and tech). The future for aviation diesels is bright indeed - and not anywhere near in the unicorn fart stages of battery electrics.
 

Toobuilder

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...I predict ten years we will see a not only high enough power density in storage but also forms of mini-reactors that will make cross country plausible.
Thats awesome! Continuous 150 KW output for 4+ hours in a 600 pound package. And a 10 minute recharge. Sign me up!
 
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