5 5
DJL

Electric Aircraft - The Thread

Recommended Posts

26 minutes ago, olofscience said:

Hence the search for less flammable battery chemistries, and the LFP research NASA is doing.

It is unlikely that less flammable chemistry will be the answer in any time frame that we are discussing. The answer will have to be better quality control and a more robust design and manufacturing process that is able to achieve certification for aviation use. Since there are currently aircraft in testing I would assume someone has addressed the problem already. But there must be a cost and weight penalty involved. 

Share this post


Link to post
Share on other sites
(edited)

May I suggest that a wise DZO will invest in a half-dozen sets of batteries and re-charge them mid-week? 

By re-charging batteries during off-peak hours, the DZO can save money on electric grid rates.

With solar cells on the hangar roof, the DZO might be able to save even more money .. or sell surplus electricity to neighbours.

Finally, with those half-dozen sets of batteries fully-charged by Saturday morning, they can swap battereis and fly until noon before worrying about re-charging.

Also the time spent swapping batteries might be needed to allow packers to catch up.

I used to work at a DZ that had too much lift capacity with a King Air. After three or four loads, we would run out of tandem rigs. So we stopped jumping for a half-hour while packers caught up, TIs trained and dressed the next batch of students and the pilot refuelled the airplane. The other reason we flew three or four loads back-to-back is that it costs hundreds of dollars to shut down a turbine engine .... wait for it to cool ... then re-start. Every hot-cold cycle costs hundreds of dollars worth of life to a turbine engine. The number of hot-cold cycles becomes increasingly expensive as you approach the end of the over-haul cycle since turbines were originally designed to take-off-cruise-land only two or three times per day ... nothing like 3 to 5 cycles up-down per hour.

Edited by riggerrob
add a sentence
  • Like 2

Share this post


Link to post
Share on other sites

Within our lifetimes the petroleum industry is going to stop refining 100LL aviation gasoline. Then we need an alternative to keep flying.

Consider the Romanian Air Force's dilemma back in the early 1990s. After the fall of communism, Romanian refineries stopped making 100LL and it was prohibitively expensive to import 100LL gasoline from Greece, so the RAF grounded their fleet of I.A.R. 823 trainers. Those trainers were powered by the same Lycoming IO-540 engines as Cessna 182 and 206. Those airplanes sat idle for a decade or so, then were bought up an American dealer and sold on to the warbird crowd, who were wearing out their similar-sized Beechcraft Mentors.

Debate all you want, but DZOs are going to need new a fuel source within the next 20 years.

  • Like 1

Share this post


Link to post
Share on other sites
(edited)
On 11/18/2020 at 5:02 AM, coticj said:

@mdrejhon You keep mentioning massive fuel cost savings. A typical caravan has (the ones we operated) had a fuel burn of 60-70L of Jet A1 per load. Current fuel price my country is 0.41€ per L. This comes to 1.85€ of fuel per person. Sure, the electricity is 4 or more times cheaper. But saving 1.4€ per ticket in a ticket that costs 30€ doesn't seem much.

Good data.   

Doing further research -- right now 0.41 Euro per L is pretty cheap, partially due to covid.  The savings may not be as much fuel wise as expected if your Caravan only burns 60-70L for a full load to 13500 feet.  Canadian/American jump tickets are closer to approximately 25-30 dollars per jump (Perris sells them between $25-$29 depending on quantity and discounts).  But avgas is also cheaper per liter in North America (1gal = ~3.8L). Now searching down for prices, I'm seeing this.

It's pretty clear (excluding maintenance savings) -- that 2020 fuel prices doesn't justify electric very well -- fuel is unusually cheap due to collapse of demand. 

ChartA_25052020

On 11/18/2020 at 5:02 AM, coticj said:

And for the fast charging that you are mentioning. The power consumption would be the same as for a wind tunnel, meaning huge infrastructure investments and massive electricity bills (I don't know if it is the same in US, but in my country the power company charges you for the power you use and the "available power" - for example household 7kw supply costs 5€ monthly and 21kw costs 25€).

That is mitigatable:

- You only need to charge intermittently, rather than continuously
- A ground-scale lithium power bank can help downscale the power utility connection.  Suitable power banks are getting cheaper. 
- Local generation is also viable too (hangertop solar, etc) especially as these are getting incentivized/cheaper.
- Some airports already have good supplies.  Not all dropzones, but some of them already have the necessary supply.  One would only need 1 candidate dropzone to be the first.

You only need a few EV-vehicle-sizes' worth of battery to surge-output into intermittently charging a skydiving plane by perhaps X% (one jump's worth) using only a ~25% depth-of-discharge (the benchmark of shallow discharge needed for a decade(s) lifetime ground battery so you don't have to replace it after three years like a worn smartphone battery).

One need only two or three true-EV-car-equivalents worth of ground lithium batteries (low few hundred kWh), to significantly downsize the necessary utility connection by 50% or more, depending on the charge:idle ratio of the electric airplane charger.  Also, small airports can frequently have significant power supplies already, so cherrypicking the right airport can justify the business case automatically.  It might not be for every airport (at first).

On 11/18/2020 at 5:02 AM, coticj said:

I don't think conversions are the way to go. Most (non Tesla) car manufacturers tried with converting existing models, but all of them found that it is just better to start from scratch.

It's not like a cheap electric vehicle -- an airplane is a much more expensive vehicle where a conversion makes sense sooner than for cars.   

In another industry, my local city (Toronto)'s regional transit agency, Metrolinx, decided to replace a gaspeaker plant plan with a lithium battery farm as the backup/UPS to power an upcoming electric subway called Eglinton Crosstown LRT.  The subway was already under construction when they actually cancelled the gas plant and replaced it with a battery farm.   Clearly, the economics suddenly clicked thanks to the scorching price drops.  Now, to smaller-cost items such as airplane, which are durable assets that can last decades, conversions are always on the table versus re-enginings.

Conversion cost has to be weighed against engine replacement too.  There may come a point where conversion becomes economically feasible, and I expect that to be feasible by 2030s .

On 11/18/2020 at 5:02 AM, coticj said:

stly you keep mentioning the batteries that would be needed for a load + 30min reserve. What kind of battery do you think this would need?

This, I have some data (some confirmed, some unconfirmed), and this is where I need to ask for confirmations.

A very fast lift to 13500ft at near max weight consume approximately ~50 kilowatt-hours for one electric airplane I heard about (not sure if it was a small one or eCaravan sized one) -- need to confirm as I obviously cannot parrot unconfirmed numbers in a Parachutist article.

Also, thermodynamic efficiency of an electric airplane and without gears, is more than twice as high as a turbine.  Electric motors routinely exceed 90% efficiency, while petrol motors are under 50% even before the gear loss (if any gears are used).  So horsepower for horsepower, a lot less horsepower to reach altitude is needed -- one can throttle back the horsepower more for an electric to maintain a brisk climb.  In some cases, efficiency apparently exceeds 3x for some power settings for the same amount of thrust.

The best ones are a good Garrett engine at 50% efficiency, but many aged turbines are only 30% efficiency.  I don't know what the PT engine thermodynamic efficiency is, but it's a lot less than a fresh new Garrett.  Also the turbines is one-third less efficient at full jump altitude (give or take) than at ground.  Electric motors don't degrade as it doesn't need the oxygen to burn fuel, only degradation from less air pressure.  Also, over their lifetimes electric motors don't degrade quite like a turbine gradually does, and fuel mixtures can easily go suboptimal by maintenance issue more easily (i.e. 10% less efficient, here and there).  And you have the additional gear inefficiency.  

When all of this combines up -- I wouldn't be surprised to see the ballpark of 1/3rd to 1/4th efficiency of a Magnix at full jump altitude is quite realistic. 

It's far less -- not sure if it closer to 1/2 as much or 1/5th as much -- but it's quite massively far less.  They certainly remotely didn't need a significant fraction of 750hp of a Magnix to climb fast.  Some questions to be added to interview...

Now, optimizing for minimum-kWh-per-jump which takes a few minutes longer to climb than max-horsepower. Surprisingly less power needed if you're optimizing for the electric sweet spot from what I hear.

Don't forget electric motors can remain far more efficient at nearly all speeds/torques, whereas a turbine has a sweet spot.  So you have more range of adjustment -- pilot can adjust flaps a bit and rev up/down a bit -- to find a different sweet spot electrically than with a turbine, since you no longer need to optimize for the turbine's sweet spot to get the maximum actual climb power possible for a given propeller power. 

Instead, you're optimizing to the sweet spot of watts-per-altitude-gain, milking your electric motor's ginormous near-full-range sweet spot -- so pilot only need to focus on optimizing for aerodynamics.  Which is still briskly fast even below maximum throttle;

Now, we know 1 liter diesel is equivalent to 10 kilowatt-hours in theoretical efficiency.  Real world is only 30% and that's before a lot of losses that aren't applicable to electric -- there's additional losses -- gearing loss, altitude loss, being away from sweet spot, etc.  

This is also consistent with the fact that a 50 liter gas tank only needs 1/5th to 1/10th the battery size for a similar range -- in a gas car versus electric car.  Let's split the middle for automobiles -- a 75 kilowatt-hour EV battery versus a 50 liter gas tank (~500 watt-hours theoretical) for about the same driving range from full-to-empty. 

The new Teslas 4680s are enabling 350 miles on a mere 82 kWh (source).  That's similar to the range of my 50 liter gas tank in my current car, so that gives you the automotive-industry comparision numbers -- 50 liters is theoretically almost 500 kilowatts of electricity in 100% pure joules laws-of-physics.  But we don't get that efficiency out of fuel because of conversion losses.   

Now you're getting the efficiency-split idea, and battery-sizing idea.

So seems 50 kilowatt-hour jump altitude is within a conceivable stone's throw.  I might be off by double, but not by that much more.

Assuming 50kWh, to consume only 33% per lift, requires a 150 kilowatt-hours battery.   

Let's be a bit more generous, and assume it's closer to 75 kilowatt-hours per lift, and we tighten the margin to say, 35%, we'll need a 200 kWh battery.

Earlier 200 kWh battery of a decade ago -- at yesterday's power density 200Wh/kg weighs 1000kg, about 2000 pounds. 

A full Cessna caravan fuel load is ~2224 pounds (source).  

Now, the 4680 is already almost 400 watt-hour per kilogram. (380 Wh/kg, source)

So today, we now already have a required battery half the weight of a full Caravan fuel load for a single jump load at 33% SoC discharge.  But that assumes 50 kWh/lift.

But if we're off by a lot and the power use is closer to 100 kWh/lift, we have to upsize the battery quite a bit, or wait for kWh to become better, then we'll need to wait longer for numbers to make sense. 

Nontheless, the real jump altitude numbers are well within the battery sizing ballparks & mass envelopes achievable.  That said, it is true it is deadweight that eats into jumper capacity.  So first conversion may have fewer jumpers, until battery efficiency improves.

Also, it excludes potential regen recapture from the typical fast dive by a jump pilot (Let's say ~10% -- since the trainer regen recaptured up to 13%) but let's ignore that for simplicity.   And energy consumption to 13500ft may go down too (for a dedicated airframe instead of a re-enginiing/conversion).

Work is being done to keep increasing capacity; including 1000 wH/kg (NASA.gov 1440Wh/kg research as one example).   

Yes, we need the battery safety measures (shock absorption cage etc), which lowers the power density numbers somewhat.  But it really truly seems the numbers are going to be able to check out well before the end of the decade even if we only improve a little bit more (to allow the battery safety structure weights).

Now, a projection example -- imagine the numbers are correct or conservative and it's only 40 kWh per jump cycle after all said and done, and we want a 25% SoC per jump, then we only need 160 kWh battery for a 25% discharge.  The remaining capacity (120 kWh) is more than enough for level flight of 30 minutes, we're simply shallow-SoC simply for battery-longevity consideration (a battery that lasts more than a decade). And let's say at 500 wH/kg by 2030 including battery-safety structures (crush zones, cooling, etc) -- 320kg battery or 700 pounds -- that battery now becomes between one-quarter to one-third a full Caravan tank (2224lbs).  If we settle for 33% SoC cycling, the battery can be downsized even further, but I'm sure we rather see a 25% SoC for one jump just simply because of sheer safety margin -- for cold weather, for battery wear, etc.  Then again, these numbers may be wildly optimistic.

Nontheless it seems the venn diagrams certainly overlap into feasibility, even for the less promising numbers.

I would like to supply a list of questions to Magnix CEO early next year for some Parachutist article, as even I make mistakes, but the battery capacity numbers definitely seems to be checking out for a "one-jump-load-sized" battery.

Please supply additional "hard questions" that I could use to formulate interview questions to ePlane industry contacts (Magnix's CEO has offered to be interviewed for Parachutist) -- I welcome the hard questions.  

Even if that means downsizing some numbers.  But obviously, it's clearly all looking promising.

Edited by mdrejhon
  • Like 1

Share this post


Link to post
Share on other sites
(edited)
On 12/2/2020 at 5:42 PM, riggerrob said:

May I suggest that a wise DZO will invest in a half-dozen sets of batteries and re-charge them mid-week? 

By re-charging batteries during off-peak hours, the DZO can save money on electric grid rates.

With solar cells on the hangar roof, the DZO might be able to save even more money .. or sell surplus electricity to neighbours.

Finally, with those half-dozen sets of batteries fully-charged by Saturday morning, they can swap battereis and fly until noon before worrying about re-charging.

Or use those storage batteries to power the ePlane charger.   There's some losses involved, but it eliminates battery-swapping overhead.

And in theory -- those very same batteries could potentially be hand-portable (~50lbs-100lbs military suitcasey things with handles on them for two people to lift), to be used as dead-heading batteries for loaning the ePlane to other dropzones.   

You unplug the storage-batteries from the ePlane charger, put them into the hold, strap them down as cargo in the main cabin, to power an extended-distance flight between dropzones. 

When at the destination dropzone, these batteries are removed for the duration of the jump operations and trickle-recharged for a few days (the duration of the boogie / event).  These are just cellphone-powerbanks-on-steroids.  Those exist already for military uses, etc. and smaller versions already exist for camping uses, and it's expected they will scale to these sizes for aviation-industry convenience.

On 12/2/2020 at 5:42 PM, riggerrob said:

I used to work at a DZ that had too much lift capacity with a King Air. After three or four loads, we would run out of tandem rigs. So we stopped jumping for a half-hour while packers caught up, TIs trained and dressed the next batch of students and the pilot refuelled the airplane. The other reason we flew three or four loads back-to-back is that it costs hundreds of dollars to shut down a turbine engine .... wait for it to cool ... then re-start. Every hot-cold cycle costs hundreds of dollars worth of life to a turbine engine. The number of hot-cold cycles becomes increasingly expensive as you approach the end of the over-haul cycle since turbines were originally designed to take-off-cruise

Excellent data.

This is generally a non-issue for electric engines.  Amortized over the loads, that's a lot of money that doesn't happen on an ePlane.

Any thermal stress (e.g. loosened cable connections that need to be re-tightened, etc) are a simpler maintenance matter.  And lithium batteries are quickly plummeting in costs.

I just heard recently a 10-gigawatt-hour lithium battery in Australia gets built.  That's more capacity in one battery farm than an entire year's of battery manufacturing just about a decade ago (or so).  The battery factories are strongly scaling up to terawatt-hour-per-year manufacturing.  

Specialized aviation batteries may remain expensive but even at ~25x-50x avation-markup of projected year 2030 cost ($62 -> $1500/kWh-$3000/kWh) would still be only $300K for a battery replacement once every ten+ years. 

That's not too shabby -- that's today's cost of an engine overhaul.  The electric airplane motors never need overhauls themselves (just relatively inexpensive maintenance), so the overhaul expense is shifted to the battery pack instead -- and possibly less frequently.  And could be even less, if the packs are more easily modular/removable, given potential future boom of approved aviation-battery suppliers.

Probably beyond 2030 battery replacement -- even at aviation inflated prices -- will be much cheaper than that.   

So even the major maintenance expense (battery pack replacement every 10-20 years) becomes less cost than the cost of an turbine engine overhaul that is not needed for electric engines as they are good for far beyond life of the airframe.

Now conversion prices are an open question, but as long as they are competitive to engine replacement, it likely becomes an attractive/viable option.

And those batteries will still be good enough to be recycled as solar-storage batteries after no longer good enough for airplanes.

Edited by mdrejhon

Share this post


Link to post
Share on other sites
(edited)
7 hours ago, mdrejhon said:

Please supply additional "hard questions" that I could use to formulate interview questions to ePlane industry contacts

  1. For the MagniX electric caravan they flew this summer, what was the weight of that aircraft?
  2. Are they already using large-bandgap semiconductors? If not, does he think they will help increase efficiency?
  3. Are the batteries actively cooled? Can he share any details on their thermal runaway containment strategy?
Edited by olofscience
  • Like 1

Share this post


Link to post
Share on other sites

A quick back of the envelope calculation regarding recharging with "rooftop" solar.

Assumptions:   The best locations for solar harvest could optimistically assume 6h / day of productive sunlight. The most efficient battery-based system would hope for 80% efficiency of transfer of that energy to a battery.

Thus:   Using the least expensive type of grid-tie panel (~330watt/panel), this would require 32 panels covering 564 sq. ft and take all day to harvest that power:

32 panels X 330w X 6h X 0.8 efficiency = 50,688 watt hours (50.69 KWH).

Thus, it would take a full (ideal) day with a roughly 11,000 watt array to recharge from one load. Solar energy doesn't happen fast, or at "high density."

Share this post


Link to post
Share on other sites

Dear Frogger,

How big a hangar roof do you need to collect enough solar energy to fly a Caravan 3 days per week? ... assuming 25 loads to 12,000' per day ....

Is that a 182-sized hangar roof/

A Caravan-sized roof?

A dozen Caravan-sized roofs?

Remember that the majority of hangars at DZs are occupied by privately-owned, single-engined Cessnas that only fly 1 day per week.

Share this post


Link to post
Share on other sites
(edited)

Dear olofscience,

I do not know the take-off weights of the electric Beaver or electric Caravan that MagniX have flown recently

.MagniX will need another year or two to determine exact weights of their electric conversions. The first batch of electric Caravan conversions will sell to short-haul airlines like Harbour Air and courier companies like UPS. Electric airplanes may become the most efficient way to move passengers and cargo between islands or across mountain ranges.

... but numbers on certified, production airplanes are always quoted at gross weight, standard atmosphere, sea level, 50 degree Fahrenheit temperatures.

Jump planes routinely take-off at gross weight juggling fuel loads with passenger loads to extract the maximum number of dollars per hour of operation.

Similarly, the majority of airliners take-off at gross weight ... juggling fuel, cargo and passengers to generate the maximum number of dollars per flight.

Edited by riggerrob
add a sentence

Share this post


Link to post
Share on other sites
(edited)

Dear mdrejhon,

Aviation electric motors will not be maintenance free.

The first batch will require inspections every day, week, year, 1,000 hours etc. As they prove trouble-free operation, 1,000 hour inspections will be extended to 1,500 ... 2,000 ...2,500 ...3,000, etc. ... similar to ETOPS.

Transport Canada will be super-cautious about extending inspection intervals.

Aviation quality control might have been the best back in 1945, when my grand-uncles returned from serving in the RCAF, but we have major improvements in automotive quality within my lifetime. Now we routinely see new automobiles run 4 years and 100,000 kilometres without maintenance. Cars can only run that long if they are built precisely. Manufacturers build modern cars precisely because they don't want to lose money on warranty repairs.

For example: My friend only recently replaced the Toyota Prius (gasoline-electric hybrid) that he owned for 17 years. He replaced it with an all-electric Chevy Bolt. His wife still drives a middle-aged Prius.

I am currently driving a 13 yeaar old Toyota Matrix, that I bought second-hand 9 years ago. Since then I have only replaced oil, spark plugs, windshield wipers and tires. It has driven 600,000 kilometres with plenty of remaining life. 

So I believe that electric airplanes can fly safely with only slightly-modified electric automobile components. With electric automobiles soon to be manufactured by the millions, economies of scale will soon drive down manufacturing costs.

Edited by riggerrob
add a sentence
  • Like 1

Share this post


Link to post
Share on other sites
10 hours ago, riggerrob said:

 Now we routinely see new automobiles run 4 years and 100,000 kilometres without maintenance. Cars can only run that long if they are built precisely. Manufacturers build modern cars precisely because they don't want to lose money on warranty repairs.

i don't think there are any cars out there that can go that long without maintenance (spark plugs, oil change tires, wipers), but haven't looked at electric ones but they still require wipers and tires.  i know that there is no way you can go that long without an oil change without doing some damage.  i also worked at toyota for a while and can tell you without a doubt there is not much precision going on with some of those vehicles.  i refuse to buy a toyota made in the us because of my time there, subaru all the way from now on.  we took a great japanese product and ruined the quality with putting americans in charge.  they were great for the first few years when the japanese were running upper level management, but then they let americans have some of those jobs, and the quality went to shit when they did.   warranty work is factored into the price.

Share this post


Link to post
Share on other sites
(edited)
On 12/4/2020 at 3:51 AM, olofscience said:
  1. For the MagniX electric caravan they flew this summer, what was the weight of that aircraft?
  2. Are they already using large-bandgap semiconductors? If not, does he think they will help increase efficiency?
  3. Are the batteries actively cooled? Can he share any details on their thermal runaway containment strategy?

Thanks. And @nwt do you have questions too? 

(Don't forget to pre-read my new reply first)

  

On 12/5/2020 at 8:54 PM, riggerrob said:

Aviation electric motors will not be maintenance free.

Right. Just to point out; I never said "maintenance free".   

I did say various synonyms of "much less maintenance" or "lower maintenance". And that they don't require traditional engine overhauls. 

Many subway trains are running on original electric motors for more than 50 years, with a very low % of motor replacements for damaged motors/etc.  Unless defectively designed, the electric motor component generally only require relatively simple maintenance (comparatively speaking)

Sure you still have to maintain them (cleanings, lubricant maintenance, inspecting/refreshing the shaft seals, etc) but they generally don't require the extent of overhaulings that many petroleum motors require.   

With no gears and pistons, the majority of electric motors typically only has one moving assembly (rotor+shaft) and far fewer entries for external contaminants (e.g. dirt, sand, salty sea air, etc).  With no pistons, tailpipe, extraneous orifices, fuel lines, for contaminants to leak in and foul up the system.  Sure you have to worry about the shaft seal and applicable lubricants / protections, etc -- and other things -- but compared to petroleum subsystems, it is much simpler.

(You can still damage the motor like cracked shafts or damaged rotor from a propeller strike during a crash, but let's put those things beyond scope of "maintenance").

Meeting FAA and Transport Canada maintenance requirements is much easier with ePlanes, since there is much fewer parts in an ePlane subsystem, and the individual parts themselves require much simpler/quicker/easier-to-detect maintenance.  

Wire wear and tear is probably even a bigger concern, you don't want cracks to show in wire coverings, potentially later leading to sparks etc. Inspection procedures will be required for that, but at least you're doing that instead of worrying about fuel lines and relateds.

Yes, the maintenance intervals may be the same frequency (legal requirement) but thanks to the simpler maintenance, fewer moving/foulable parts, any legally-required maintenance to the fullest required extent is completeable in less time. Transport Canada and FAA needs to keep us safe, but even the higher-rigorousness (at the beginning) appears to be likely less human-hours of maintenance.  So the total number of human-hours of maintenance is likely far lower.

Edited by mdrejhon

Share this post


Link to post
Share on other sites
(edited)
5 hours ago, mdrejhon said:

Right. Just to point out; I never said "maintenance free".   

The temperatures and pressures they will operate at internally compared to either reciprocating or turbine engines will make seem to be maintenance free in comparison. 

Edited by gowlerk
  • Like 2

Share this post


Link to post
Share on other sites
4 hours ago, gowlerk said:

The temperatures and pressures they will operate at internally compared to either reciprocating or turbine engines will make seem to be maintenance free in comparison. 

Yes, that’s another benefit of electric motors. With high efficiency and no combustibles / atmosphere requirements, there is far less temperature differentials too, to wreak havoc with materials.

Biggest concern is cooling as even ballparks of approximately ~95 percent efficient on 500kW is still 25kW heat, but that is far less waste heat than a turbine, and most electric power needed is much less than that.  Easily cooled by airflow of flight. Also, electric motors in factories are designed to safely operate well above boiling temperatures and the air cooling of 25kW keeps it in operating ballpark.

Share this post


Link to post
Share on other sites
(edited)

Ugh, I made minor measurement-unit boo-boos in my original post that I didn't notice until "Edit Post" time limit expired. 

Such as "watts" vs "kilowatts" and "kilowatts" vs "kilowatt-hours" in a couple of sentences.  However, the post remains exactly the same as before otherwise:

On 12/3/2020 at 8:20 PM, mdrejhon said:

This is also consistent with the fact that a 50 liter gas tank only needs 1/5th to 1/10th the battery size for a similar range -- in a gas car versus electric car.  Let's split the middle for automobiles -- a 75 kilowatt-hour EV battery versus a 50 liter gas tank (~500 watt-hours theoretical) for about the same driving range from full-to-empty.

Self correction:
I meant 500 kilowatts-hours theoretical thermodynamic efficiency.

My point was, rheoretically ask yourself: How the freaking hell can 500 kilowatts-hours-equivalent of liquid unleaded fuel be so well-matched by an 82-kilowatt-hour electric battery in a Tesla for exactly the same 350 mile car range!?  Even aerodynamic efficiency differences of two compact cars don't explain that chasm (my Hyundai compact versus the 4680-based Tesla Model 3).  Simply put, much of this from sheer efficiency of electric.

What this leads, subsystem properly designed, electricity leads to a 5x-10x more efficient system (more "fuel" energy converted to actual useful work instead of heat) when all real-world losses are accounted for. This leads good credibility to that I heard that the equivalent of one near-max-weight trip to typical jump altitude consume a mere 50 kilowatt hours of electricity (give or take).  Automotives don't directly translate to aeronautics, but electricity subsystems are generally more efficient in quite a large number of industries, and will likely translate very well here. 

You get the idea of sheer smaller-battery-requirement and the realisticness of that battery being smaller than a full fuel load.  While battery is not practical for long hauls of A380 lore, the "one-jump-plus-30-min-reserve" battery is potentially perfect for jump planes once they pass the critical 400+ kWh/kg power density threshold. 

On 12/3/2020 at 8:20 PM, mdrejhon said:

Instead, you're optimizing to the sweet spot of watts-per-altitude-gain, milking your electric motor's ginormous near-full-range sweet spot -- so pilot only need to focus on optimizing for aerodynamics.  Which is still briskly fast even below maximum throttle;

Here, I meant "watt-hours-per-unit-of-altitude-gain".  That would be a more accurate phrasing, since that's a more important metric.

Nontheless, most smart readers probably figured out what I actually meant and saw these obvious unit slip-ups.

Edited by mdrejhon

Share this post


Link to post
Share on other sites

i wonder if the newly designed sodium batteries would work here.  apparently, the new cathode design allows for 10,000 recharges while retaining 91% capacity.  i don't know a lot about sodium batteries other than they are unstable, but this should fix that part.  granted, it is just a proof of concept and was done at 122* f, but it shows promise.  it also said something about a 3.6 second recharge time, but not sure what size battery that was. 

Share this post


Link to post
Share on other sites

don't we try to keep the planes in the air and on the ground?  it's not like balls of sodium.  they're safer than lithium batteries. 

also, with a 4 second recharge time and 10000 cycles i think i would risk it and just keep the plane dry on the inside, something we should also be doing if i understand correctly.

Edited by sfzombie13
had a thought

Share this post


Link to post
Share on other sites

It seems there is a lot of activity in a competing technology, fuel cells. Especially with a new thin polymer that can strip the nitrogen away from ammonia, and some innovative way of making ammonia more efficiently. I don’t have the link to post, but it seemed to be real. Ammonia infrastructure is well established and relatively low pressure requirements should make it possible to be distributed by existing gas stations with reasonable investment. Getting hydrogen for a fuel cell from ammonia is a very interesting alternative.
 

It is important to not be tempted to allow batteries to be prematurely declared the technology winner by having government subsidize it exclusively. Should be something like an X-prize for the ability to provide electricity for vehicles by any means whether battery or fuel cell or whatever. 

  • Like 1

Share this post


Link to post
Share on other sites
On 12/4/2020 at 12:51 AM, olofscience said:
  1. Are they already using large-bandgap semiconductors? If not, does he think they will help increase efficiency?

Just a note here - inverter efficiency is already in the high 90s for most designs, so additional efficiencies there are going to have a very small effect on overall efficiency.

Share this post


Link to post
Share on other sites
On 12/8/2020 at 1:49 PM, sfzombie13 said:

i wonder if the newly designed sodium batteries would work here.

Any question that starts "I wonder if this new battery chemistry will . . ." the answer is no.  I first started working with battery chemistries in 1995, and since then I've seen perhaps 40 new chemistries that promised to:
-greatly increase energy density
-greatly increase power density
-greatly decrease cost
-greatly extend life
-be much easier to make
-be much safer

Of them, the only one that has resulted in a viable product is silicon anode for lithium chemistries - and they've been working on that for at least 15 years.  And they're not much better than standard lithium ion despite the promises.  Two _almost_ worked - the salt based Aquion battery and the Ovonics lithium-sulfur battery.  All the other improvements that have come in the battery space have come from incremental refining of existing chemistries.

That being said, batteries today are pretty good, and meet the requirements for electric aircraft.  But even if a new chemistry does turn out to actually have some advantages, we're at least ten years away from seeing it in action in a car (or airplane.)

Quote

4 second recharge time

Keep in mind that a 4 second recharge time for a 100kwhr pack is going to take something like 100 megawatts - the power that a large town (population 100,000) takes.  

 

Share this post


Link to post
Share on other sites
20 minutes ago, wolfriverjoe said:

No, silly.

It's "Curses, foiled again."

You're Canadian. You, of all people, should know this.

 

https://stilettosstoliandscribbles.com/2016/07/14/curses-foiled-again/

Yea, I grew up watching "The Rocky and Bullwinkle Show". But I'll let you in on a secret. It's actually American. I'm pretty sure that Snidely Whiplash was an illegal alien from south of the border.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

5 5