Lithium-ion For Airplanes: No Thanks

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Now that the world is once again swimming in oil and gagged with shale gas, it's hard to imagine that in 1976, no less an august energy player than Exxon thought the world was running out of oil. So it wanted to get into the next big energy thing, which would be rechargeable lithium batteries for electric cars. It launched a well-funded research project and developed a promising design which, according to Seth Fletcher's Bottled Lightning: Superbatteries, Electric Cars and the New Lithium Economy had one big problem: When they sent a sales rep to Chicago to show the batteries, Exxon discovered that the electrolyte was breaking down into a gas that would ignite on contact with air. "So each day, Exxon's man in Chicago would show off the company's breakthrough...then each night in his hotel room, he would carefully twist off the top of each battery and watch as a fireball leaped out." Exxon decided to stick with oil and gas.

Forty years later, lithium batteries are thought to be on the verge of a demand surge, driven by equally strong demand for electric cars. And as sure as cars will be lithium-battery powered, so will airplanes—both as primary power and for starting batteries. It's already happening, in fact. But the ghosts of Exxon's fireballs still haunt the lithium battery industry, even though modern versions are more stable than Exxon's lab models could ever have been. Some aviation battery manufacturers—Concorde is one—are reluctant to aggressively offer lithium-ion for safety and cost reasons, but mostly safety. The FAA has expressed reservations about lithium-ion technology in airplanes and apparently with good reason.

Obviously, the agency has stringent requirements for certification of aircraft lithium batteries, but the industry was surprised to learn that this wasn't enough to prevent a lithium-ion battery from lighting off in a Cessna Citation CJ4 last year. Neither Cessna nor the makers of the cells, A123, would comment on what happened to cause that fire, but Cessna quickly withdrew the batteries from the Citations and the FAA issued an emergency AD. Cessna says it's still committed to Li-ion, but declines to offer details. Ironically, A123's cell technology—lithium-ion nanophosphate—is considered the most stable of the principle lithium chemistries, yet it still notched an aircraft hull fire.

The risk of lithium-ion battery explosions and fires, while low, is complicated by their potential severity. Once it ignites due to thermal runaway, a lithium battery fire is difficult if not impossible to extinguish and it will often lead to a chain reaction, igniting neighboring cells. For airplanes, the nature of the risk is bifurcated. For starting batteries which must be charged in flight, an overcharge/imbalance in one cell can lead to thermal runaway. Li-ion technology is equipped with electronic protection to prevent this and also to keep the batteries from discharging to zero, which will trash them. Primary electric airplanes don't have much risk here, since they're charged on the ground, not in flight.

The second risk relates to cell shorts which, no matter how good the quality control, are thought to occur once in every one to five million cells. A short can lead to thermal runaway. That sounds like a small risk and probably is. But consider this: UPS has suffered two aircraft hull-loss fires in airplanes carrying lithium-ion batteries. Although investigators couldn't pin the source of the fires on the batteries, they were prominently mentioned in the accident reports. One of the airplanes was carrying 81,000 Li-ion batteries.

Knowing what I know about Li-ion, I'm not interested in having one in an airplane I fly, thanks. The technology will get there, I'm sure, but I'm perfectly happy to wait until it's more stable and robust. What's the rush? (I came to this conclusion after one lithium battery expert I spoke to said he found the power outlets in airliners being used to run and charge laptops to be a really bad idea.)

As you can surmise, however, aviation won't drive much primary development in Li-ion. OEMs will figure out better electronics and safety containment systems, but they'll use cells from A123 and other major providers. In fact, that's just what Mid-Continent Instruments and Avionics has just announced it plans to do.

What will push Li-ion technology is the electric vehicle market, which is the next big industrial crap shoot. Companies like A123 are banking on rapid uptake of EVs, this despite a long history of failure of electric cars to compete with internal combustion engines. "This time it will be different," goes the mantra. Maybe so. But see above. Exxon thought the end of the age of oil was in sight 40 years ago, but we have more producible oil and gas than ever. If gas reserves keep growing exponentially and if gas-to-liquid becomes economically practical, electric cars—and the batteries to power them—may have another tough time of it.

In a future blog, I'll examine hybrid technology for aircraft. It's coming, too.

Comments (89)

Paul, for every hull loss due to Li-Ion, I'll raise you thousands and thousands of hull losses to avgas/jet fuel. If nothing else, just think of all the post crash fires pretty much exclusively due to carrying a highly flammable liquid. So that point has very little validity.

Yes, it is different now. This time, electric will succeed. Teslas Model S recentöly released will change the game. Aviation is going to be dragged kicking and screaming into it. It makes extra much sense for aviation as you eliminate pretty much everything we have to struggle with today: TBO, high altitude performance, power-to-weight, price, etc, etc. Electric is the future. Resistance is futile.

Posted by: Adam Frisch | July 18, 2012 10:33 PM    Report this comment

And I for one can not wait to see the back of all these nauseating 20-year ongoing talks of "what shall we replace Avgas with", EPA madmen or or see the back of all big oil companies. What's extra great about electric is that soon we will for the first time be out of the grip of shady war mongering profiteers that held us in a vice due to owning production tools (refineries) and by extension your wallet. Electric can't be controlled like that. We can charge from solar panels, outlets, windmills etc and they can't stop us. Bye, bye, big oil. Nice knowing you.

Posted by: Adam Frisch | July 18, 2012 10:41 PM    Report this comment

I've driven electric autos for daily 14 years now. I've watched the oil industry beat down electrics so we can continue to "choke" to death on their oil. Now they are putting out "mis-information" about lithium or any other challenge to their greed. I've driven on lithium for 4 years now in my converted Pontiac Fiero. There are several variations in lithiums. T%he fire hazard only exists in some versions, but they want us to think all lithiums are bad. They say this while setting on a tank of gas!

Posted by: John Brecher | July 19, 2012 7:02 AM    Report this comment

I thought the fire hazard was from lithium coin cells rather than lithium ion batteries. This is a completely different technology that has lithium metal in use as an electrode. Lithium Ion batteries don't have metal electrodes.

Of course I could easily be wrong on this (or any other) point. Still, when the technology is ready for prime time I hope to have an electric powered sport plane. For now the biggest obstacle I know of is the FAA hasn't yet changed their rules to allow electric powered LSA. This will come along pretty soon and might even allow multiple motors. (Electric motors are a lot more reliable than reciprocating engines.)

Posted by: PAUL MULWITZ | July 19, 2012 7:29 AM    Report this comment

"Lithium Ion batteries don't have metal electrodes."

What makes rechargeable lithium-ion batteries volatile is their electrolytes, which consist of lithium salts dissolved in flammable organic solvents. Coin cells and some smaller cells do have metallic lithium and are very volatile when heated or shorted.

The FAA has quite a list of these going off in aviation settings. They make small-scale but usually not too damaging explosions. A case or two of flashlights rocketing around a cockpit and a device called an Air Buddy personal air purifier lit off in a couple of cabins. Numerous other laptop and PED fires reported.

But in context, the risk per flight or risk per 100,000 hours is quite low, probably in the hundreths. Nonetheless, the consequences of a Li-ion battery can be severe, hence the concern. The fires can be unsupressable by available means.

An ICAO-sponsored study estimated a cargo hull loss every two years due to Li-ion batteries if new regulations regarding packaging and labeling weren't adopted. (They are being adopted.)

NiCads and NiMH and even lead acid turn up in the fire reports, too. But these aren't high-growth technologies, as Li-ion is. Thus the risk escalates. The Chevy Volt, by the way, has Li-ion and had a couple of post crash test fires. Issues with the liquid coolant for the batteries.

Posted by: Paul Bertorelli | July 19, 2012 7:57 AM    Report this comment

The biggest obstacle for electric LSA is likely marketability. When the FAA approves electric standards for certified airplanes, it won't make them any more saleable beyond early adopters until improved batteries come along. And they will.

Same with EVs, The early adopter market is buying now, but it's not anywhere near a mass market. Hate the oil companies all you want, but oil and gas remain the prime movers because they are cheap, effective and available. And, improbably, getting more available.

It's going to be an interesting decade ahead.

Posted by: Paul Bertorelli | July 19, 2012 8:00 AM    Report this comment

Adam I fully agree with you on the Oil industry but just to put things into perspective do you or anyone you know capable of producing the Li-ion batteries in their garage for general use. There is the paradox we will still be subject to some major ball game companies wimps. I read somewhere that the Li-ion batteries can only work for three years before they pack up. True or not seems there are a lot of problems to be overcome and I do believe that the oil companies will start to introduce some of their bought patents, kept in vaults in their deep dark dank dungeons, on water fuelled vehicles.

Posted by: Bruce Savage | July 19, 2012 8:49 AM    Report this comment

Oh I forgot I was watching the ICON A5 and remembered the Socata Rallye 235 E  otherwise known as the tin parachute where if you tried to keep the aircraft in the stall it would float to the ground as if it were a parachute hence the name tin parachute. So I question the statement by ICON that they are the first non stall production aircraft. Sorry I know this is not part of the subject but just wanted to say my piece on that.

Posted by: Bruce Savage | July 19, 2012 8:57 AM    Report this comment

The next lithium battery wave will be lithium-polymer (LiPo). They are already the choice of power for radio control models due to their energy density. They burn even better than the lithium ion. Newer laptops have already moved in that direction. The fact that ceramic "charging vaults" and fire resistant charging bags are popular tells the whole story. Try youtube for plenty of videos of lipo fires.

And yes impact damage can make them "cook off" so post crash fires will still not be a thing of the past!

Posted by: Kevin McCue | July 19, 2012 9:07 AM    Report this comment

Several things have changed since 1976; and I rarely fly any airplane with 81,000 batteries of unverified provenance aboard. I don't have an airplane any more, but I do have a trouble-free li-ion (Super-B) battery in my motorcycle.

There are big differences among the various li-ion batteries on the market, however; and it should be noted that many come with dedicated bench/initial chargers. There's a reason for that, too.

Posted by: Tim Kern | July 19, 2012 9:13 AM    Report this comment

Paul B. The last time I seriously looked into this question the batteries were indeed the biggest obstacle. That was over a year ago. At that time we needed a 2x battery capacity increase to even hope to meet my minimum of 100 mph for 2 hours with 2 seats and normal wing loading (10 lbs/sqft for LSA or 15-20 for normal category aircraft).

ASTM adopted an electric power standard over a year ago. At that time the FAA guys in attendance said they were working on appropriate approvals for electric LSA and would not get in the way.

I guess the fire problem must be solved before we get practical airplanes too.

Posted by: PAUL MULWITZ | July 19, 2012 9:18 AM    Report this comment

Legend Cub is going to introduce their new Super Legend at AirVenture next week. It is going to use a Lithium Iron Phosphate battery in lieu of the more conventional Odyssey PC680 battery they used to use. This saves about 10 pounds. Thus one aviation manufacturer is already going to give Lithium batteries a try. I hope that goes well for them.

Posted by: David Prizio | July 19, 2012 9:54 AM    Report this comment

I once had a lead-acid battery start a fire in my car -- the clutch cable was left un-attached by a highly paid professional mechanic and rubbed against the terminals until it shorted....
So fires in aircraft are likely to continue occasionally what ever the battery flavor.
Where aircraft may get a boost from present R&D is from electric motor technology.
After years when the basic design has been unchanged, there are suddenly new designs, most involving hub drives, which open the way to greater efficiency, especially when linked with clever electronics.
Many seem to be most efficient in small packages, so instead of one motor in the front, eight or more on the wings may be the model in the future.
The battery boys say 10 more years for the next big breakthrough, like they said five years ago....

Posted by: Brian McCulloch | July 19, 2012 10:10 AM    Report this comment

One of the electric manufacturers at Aero told me they thought the battery technology is already here for very light sport, short duration airplanes and/or trainers. I think that's correct, but as I said, it will be an early adopter market.

Mass market will take more energy density. Right now, the typical energy density is running between 110 and 150 Wh/Kg. A company called Envia claims to have a Li-io pouch design capable of 400 Wh/kg. (

If this becomes a commercial reality--and it isn't yet--it will shift things strongly in favor of EVs across all markets. A good thing.

As for the fire risk, Li-ion supporters tend to dismiss it as trivial. Yet despite having a certified system with all the technical horsepower Cessna and A123 could throw at it, a battery still burned. Cessna was concerned enough to pull back.

Why? This gives me pause. I want to know more before even putting one in my motorcycle, which I'd like not to burn up.

Posted by: Paul Bertorelli | July 19, 2012 10:18 AM    Report this comment

I've recently gotten into kayak fishing. For the fish-finder/chartplotter I needed a battery. I had a choice between a 7000mah lead-acid battery that weighs ~5 lbs. Or a 9800mah Li-ion battery that weighs

Posted by: Andrew Upson | July 19, 2012 10:20 AM    Report this comment

I do, however, disagree with the premise that oil as an energy source is stable (cost and avail) as we move forward. We have found that the battery technologies need to be explored. The real issue, however, is that much like any new technologies, great care and protection must be exercised in their use. Imagine the trepidation expressed when internal combustion cars were being introduced. There are nearly 600 internal combustion fire a day in the U.S. alone.....does that concern us? We have simply become accustom to the issues. I do agree that without proper systemic precautions, the battery concern must remain.

Posted by: Ronald Butler | July 19, 2012 10:45 AM    Report this comment

I reckon this kind of tech is going to take over eventually but I can see your point about the difference between stats and real life - you can't do much to predict or mitigate a battery cooking off. Maybe they can be mounted via the underside of wings to facilitate rapid swapping and equally rapid "deployment" in flight in the event of a fire?

Posted by: John Hogan | July 19, 2012 10:57 AM    Report this comment

Ronald, you can't paste links. Our anti-spam software strips it out, so you don't slammed with messages about cheap Rolexes. Just write the link in like this www.linkURL or paste it and strip the http. Should work.

The thing I learned about the 787 battery package that concerns me is that it's lithium cobalt oxide--high energy density but also the most volatile of the chemistries. I imagine that battery is quite large and energetic. I hate to think of it going thermal anywhere, but especially on a long overwater leg.

Posted by: Paul Bertorelli | July 19, 2012 11:13 AM    Report this comment

Paul, when you address hybrid airplanes, here's a question I hope you'll cover: a hybrid Prius's fuel economy advantage comes from regenerative braking, and perhaps a bit of more-efficient operation at parking lot speeds. An airplane doesn't experience the car's equivalent of city traffic, where these advantages take place. Seems to me you add weight, complication and expense for a useless capability. So what true advantages do you get by making a hybrid airplane?

Posted by: John Schubert | July 19, 2012 11:35 AM    Report this comment

John - There are more types of hybrids than what the Prius uses.

The Prius uses a parallel hybrid system. It's a rather Rube Goldberg-esq setup in that you have the IC engine connected to the driveline along with the electric motor. The IC engine is also connected to the batteries via a generator. So the IC engine, or the electric motor can put power to the wheels independently, or simultaneously. And the IC engine can power the wheels, or charge the batteries, or both. Plus they added the regenerative braking to capture a little extra power.

The other main type of hybrid is the series hybrid (used by the Chevy Volt). In this setup the IC engine is never directly connected to the driveline and cannot power the wheels. It is strictly used as a generator to produce electricity that can be fed either directly to the electric motor, or into the batteries. The electric motor is the only thing actually driving the wheels. In this case the IC engine is really only there to provide power once the batteries are drained but you still haven't made it to a charging station.


Posted by: Andrew Upson | July 19, 2012 11:59 AM    Report this comment

The series hybrids are what I would expect to see in an airplane. It's a technology that's been used for decades in trains and submarines. While I'm still not a huge fan it at least makes quite a bit more sense than a parallel hybrid. I still maintain that anyone who thinks a parallel hybrid is a good idea failed thermodynamics.

As the auto industry in Europe has proved you can get better fuel efficiency at much less cost than a parallel hybrid by going with a turbocharged direct injection diesel. If the attempt is to reduce fuel consumption to help keep flying affordable a switch to diesel would be a better choice than a hybrid.

Posted by: Andrew Upson | July 19, 2012 11:59 AM    Report this comment

In looking through the article and posts following the same, a few people seem to think that because " ... Now that the world is once again swimming in oil and gagged with shale gas, ..." there is no need for electric cars or airplanes. But with the number of parts per million of carbon dioxide in the atmosphere steadily increasing, the limit to how much fossil fuel we can burn may well be determined by the ability of the Earth's atmosphere to absorb all the CO2 we, humanity, are producing. So I think we need to keep up the research and development on lithium ion batteries, to solve the problem of fires and explosions without giving up the advantages of said batteries in being able to store more energy than other battery types.

EAA should encourage aircraft homebuilders to experiment with electric aircraft with Li-ion batteries and also, piston-powered planes using ethanol-containing fuels.

Posted by: Alex Kovnat | July 19, 2012 12:13 PM    Report this comment

How sad and funny it is that back in the day everyone told the wright brothers, "if God wanted man to fly, he'd have given them wings!" Then everyone told Doolittle you can't use planes as navy bombers, everyone told the Lockheed engineers the sound barrier couldn't be broken. No one will want a personal computer, hydraulic rams won't ever work for diggers, digital cameras will never replace film, the internet will only be used by a minority of nerds. See a pattern here? Every time a new and innovative technology comes forward, closed minded people claim, "it'll never fork for reason X!!!" I fly 300+ hours per year in a C172 for business. the day I can go electric I will. Anyone here forgetting how many off airport incidents occur due to RUNNING OUT OF GAS? I'd rather have less energy but know to the second how much I've got. And let's not disregard the MTBF on electric motors vs. boxter engines. And let's not forget that electrics are QUIET and the neighbors won't be as pissed now that the planes aren't making a racket, and aren't crashing into their homes from fuel starvation and engine failures. I don't give a crap about the supposed "green" advantages. I care about cost, dropping the barrier of entry for new pilots, and survival for GA, and electrics provide potential for lower cost, safer operation and lower maintenance. If we ignore this technology it will be to our peril.

Posted by: a b | July 19, 2012 12:29 PM    Report this comment

Lets look at a couple of general issues with A/C and EVs. First, one of the big but unspoken issues is what happens with THE major source of tax money if we switch. Highway, aviation and general sales taxes take a big dive with reduction of petroleum fuel use. There is already evidence of government interference with increased fuel economy simply because of this issue. There are decent vehicles sold outside the US that get double the best fuel economy of those sold here. Several sources within the industry and government admit that the loss of tax revenue is a big reason they are not available here.
Second, consider how electricity is sold. Cost is based upon use. The more you use the more it costs. If you have to pay higher tier rates to charge your vehicle (mine is about 54 cents /KWH), the cost savings soon go away. Not to mention the paucity of locations were you can recharge being a big issue.
However, one has to agree that the energy contained and destructive potential of a full load of petroleum fuel is hardly less and issue than that of a charged high capacity battery. Now lets hear from all the global warming/climate change folks about how EVs will solve all the CO2 issues like in China where they generate most of their electricity with coal.

Posted by: DALE RUSH | July 19, 2012 12:30 PM    Report this comment

I have a hard time wrapping my mind around the concept of a "hybrid" airplane. As John mentioned a parallel system works in cars by capturing the kinetic energy normally converted to heat by braking. But simply paying careful attention to flight planning allows the very efficient conversion of kinetic energy (altitude) into distance traveled. So the added weight and complexity of a parallel hybrid system seems to be of little benefit.

Where a series hybrid/electric system could be of huge benefit would be for turbine transport category aircraft for taxing. Turbine engines are horribly inefficient on the ground (due mainly to their inability to idle at low power outputs). To be able to taxi to-from the gate on either battery power saved from braking on the previous landing or generated from a more efficient APU (like a train) could cut fuel use and emissions (and noise) considerably.

That extra power could also shorten takeoff distances.

Posted by: KRIS LARSON | July 19, 2012 12:42 PM    Report this comment

"And let's not forget that electrics are QUIET and ... aren't crashing into their homes from fuel starvation and engine failures. ... I care about cost, ... and electrics provide potential for lower cost, safer operation and lower maintenance."

A large portion of the noise in light GA is from the prop. Yes, noise would be reduced without an IC engine, but don't kid yourself that it'll be nearly silent or that people won't still complain.

Batteries degrade over their life cycle. A full charge that lasts for, lets say, 4 hours when brand new might only last you for 3-3.5 hours after a year or two. Forget that and you'll be in just as much trouble as the guy that short fills his gas tank.

Cost? Right now the battery cost might be halfway tolerable (even if the energy density isn't), but if EV's become widespread that will change. Look up global production of industrial metals and extrapolate from there. Plus as there's more demand on the grid due to EV's the cost for electricty to charge those batteries will go way up.

Lower maintenance? On the electric motor itself, sure. The batteries OTOH are another story. There may not be much until they degrade or fail but then you'll have massive replacement costs.

Safety? That's debateable. Between Li-ion fire risks, and battery degradation affecting duration I don't see a huge benefit. Plus there's nothing about electric power that will change R-LOC, CFIT, VFR into IMC, and other accident rates.

Posted by: Andrew Upson | July 19, 2012 1:00 PM    Report this comment

Andrew, I never took thermodynamics but I can see how a parallel hybrid would help airplanes. The secret is in the different torque curves from electric motors and IC engines. Also, it takes a huge amount of power to get a plane airborne compared to cruise flight.

So, electric motor could be used along with the IC engine (a la Toyota) to accelerate down the runway and also to perform climbs. For cruise a small IC engine could maintain altitude and speed while slowly recharging the batteries for the next climb or takeoff. The only real advantage would be weight of the smaller IC engine and a little fuel savings on takeoff and climb. That means this won't work if you need heavy battery packs to power the electric motor.

Posted by: PAUL MULWITZ | July 19, 2012 1:17 PM    Report this comment

I don't know about the advanced mathematics involved in parallel hybrid power plants. I do know my hybrid Camry passes a lot more gas stations than a pure IC powered one. Mine gets around 35 mpg while the IC only gets around 20.

Perhaps this is similar to the bumble bee. We all know aerodynamic rules say a bumble bee can't fly. So maybe thermodynamics say the Toyota can't get better mileage - but it does.

Posted by: PAUL MULWITZ | July 19, 2012 1:20 PM    Report this comment

Dale Rush tells us:

"Lets look at a couple of general issues with A/C and EVs. First, one of the big but unspoken issues is what happens with THE major source of tax money if we switch. Highway, aviation and general sales taxes take a big dive with reduction of petroleum fuel use. There is already evidence of government interference with increased fuel economy simply because of this issue. "

The reason why our government won't let us have itty-bitty cars with engines ~550 cc or so, is because they don't meet SAFETY regulations. We could have 50+ miles per gallon now, if it weren't for increasingly stringent safety and crashworthiness requirements that make it necessary for cars to be bigger and heavier. We should also note that while older Cessna 182's were respected and loved for being able to carry 4 people plus enough fuel to have a decent range, today's C182 is not as capable in that respect. Reason? More stringent FAA crash safety requirements.

Posted by: Alex Kovnat | July 19, 2012 1:22 PM    Report this comment

If your idea of flying is hour long hops (for training or for fun) then electric may be an option in the near future. Beyond that, though, we're a long way from viable competition with good old liquid hydrocarbons.

I do have to grin at those who think moving from internal combustion to battery electric will somehow divorce them from depending on large businesses. Or maybe they have a plan to make motors, controllers and batteries in their kitchen, who knows?

Posted by: John Wilson | July 19, 2012 1:25 PM    Report this comment

On my Cherokee, I put in a new starter motor, and battery, and it cranked fast enough to taxi and takeoff down the runway-NOT!

How about a truckload of iPhones for power? Well, the gross weight was 8000 lbs, and my bald tires popped the inner tubes.

A recharger would work though, I just need a used 747 to lead the way, with my cord attached, of course, to the airborne charging station. Speed differences mean I just need a steel cable, no electronics are really necessary. Taking the wings off the Cherokee relieves the stress, but I just went back to using mogas, actually!

Posted by: Ron Brown | July 19, 2012 1:32 PM    Report this comment

Paul, my company met with Boeing about the issue of thermal runaway in these systems. If one takes a close look at the systems that we "grandfathered" on the 787, they might be shocked. BTW, thnks for the note on pasting links. I will follow the suggestion. Again, I think that advancements in alternative methods of powering our future are needed. In the case of Li-ion technology, they represent great optins to meet that end. However, there have to be safeties in place to mitigate the effects of the rare failure. It has been my experience that too many in the battery development industry fly through r&d and forget about the drawbacks to the technology. Trainin, planning, and proper fire suppression methods can make all the difference.

Posted by: Ronald Butler | July 19, 2012 1:35 PM    Report this comment

"The Prius uses a parallel hybrid system."

Actually, it's considered a serial-parallel hybrid system because the Toyota drive is quite unique in the world of hybrids--it kind of works in both modes. I actually think it's a marvel of engineering and with four million on the road, it has stood the test of real world operation and has done quite well on durability. In a world with a billion cars, one can argue whether it has gotten beyond the early adopter market. I would say that it has. The Prius gains fuel economy from the regen braking, from slow speed duty cycle in city driving and because it has an Atkinson-cycle engine. Owners report fuel economy in the 45 to 50 MPG range.

On the airplane side, two hybrids are proposed. A pure parallel from Flight Design and a pure serial from Pipistrel. Flight Design wants to gain experience with the hybrid as a means of launching into full electrics because they think the batteries aren't there. Pipistrel thinks the pure serial can deliver sufficient economy to be practical. It's also pursuing pure electrics.

Posted by: Paul Bertorelli | July 19, 2012 1:41 PM    Report this comment

As for dissing EVS, I'm always amused by people who think they're a slam dunk or who think not believing in them is to doubt progress in general. The harsh fact, however, is that EVs have been attempted for more than 100 years.

The main reason they failed is that lead-acid technology limited their appeal, but also because fossil fuels were more available, cheaper and delivered more performance. That's still true today and EV supporters ignore the fact that internal combustion technology continues to advance, too, although not much in aviation.

If new fossil fuel finds sustain further IC development and especially better hybrids, you can marvel at EVs all you want, but they just won't be competitive in the mass market, just as they never have been. Buyers will vote with their wallets, just as they always have.

What could change that, of course, is public policy that attempts to limit CO2 emissions through restrictions or taxes as a climate change initiative. It could come to this, although it will take a mustering of global will that's nowhere in sight at the moment.

Either way, electric airplanes will benefit and they'll come. After all, airplanes are the ultimate niche market.

Posted by: Paul Bertorelli | July 19, 2012 1:52 PM    Report this comment

" If one takes a close look at the systems that we "grandfathered" on the 787, they might be shocked."

I can imagine. Or maybe I don't want to. This is the stuff of accidents that could have been expected, predicted and prevented, but weren't.

I hope they've got good electronics on that 787 battery and good containment, too.

Posted by: Paul Bertorelli | July 19, 2012 1:55 PM    Report this comment

Hmm talking about the Prius Hybrid getting 45 to 50 MPG the Merc C class 220 diesel was able to return 60 to 65 MPG on the open road at 80MPH. Even the diesel Result Megan returns 50 to 60 MPG. So don't be offended if I don't get excited about hybrids. Oh I forgot the American gallon is different to the English gallon so your 50 MPG(A) is actually 62 MPG(E). Pity the aviation industry did not follow the auto industry and designed better vehicles with more efficient engines then we may not be in this position as we find ourselves today.

Well Paul B seems you hit a nerve this has one helluva response well done.

Posted by: Bruce Savage | July 19, 2012 1:56 PM    Report this comment

I know (firsthand)that the battery assemblies that Tesla uses are one of the only, if not THE only, packs approved for air shipment. That means the thermal issues have been dealt with, and to the satisfaction of the international bodies that police these things, engineered away.
Can't be done?
It can.
Robin White

Posted by: ROBIN WHITE | July 19, 2012 2:00 PM    Report this comment

Paul M - I never said the Prius can't get good MPG's. But when you look at lifecycle impacts you see the folly of the Prius, and the truth of laws of thermodynamics. MPG's in the range of 45-50 are unremarkable for a car in the size and performance class of the Prius. The TDI diesels in Europe that are in that same class get 50-70 MPG and cost a lot less to buy (not counting tax incentives that may or may not exist in Europe). Plus those cars don't have the environmental impacts from the battery and electric motor production that the Prius does. A number of years ago I recall reading a study that showed the lifecycle (production, use and disposal) impact of a Prius was worse than a Hummer.

You can't get something for nothing. If you improve performance in one area you pay a penalty somwhere else in terms of weight, complexity, cost, effeciency, etc no matter which way you go. It's a matter of deciding which impact you're most willing to suffer to further your goal.

Posted by: Andrew Upson | July 19, 2012 2:09 PM    Report this comment

Andrew, I yield to your superior knowledge on the life cycle cost point. All I know is my Camry (not a Prius) hybrid is a wonderful car that I think is well into the mainstream of technology rather than an early adopter novelty. Everything about it is equal or superior to the IC only Camry (the best selling car in the world for many years now).

Let me just make a small comment on the future of batteries. I recently attended several international meetings to discuss just this subject - battery powered aircraft. I am convinced we are not quite there yet, but a practical electric sport plane is in the very near future. I don't like what Pipistrel and some others have done with glider class wing loading but a small improvement in battery density will make it all work. It is absolutely incredible how many government and automotive scientists and engineers are working on this issue. I give it only a few years before electric trainers are more popular than IC ones.

Posted by: PAUL MULWITZ | July 19, 2012 2:24 PM    Report this comment

"What could change that, of course, is public policy that attempts to limit CO2 emissions through restrictions or taxes as a climate change initiative."

Which would be idiotic. Of course, given the state of our society that means it probably will happen.

CO2 is a fertilizer. More CO2 means more plant growth, which means more food and construction materials (2x4's). CO2 also has a logarithmic effect on temperatures and becomes asymptotic to a pretty gentle slope of a straight line curve after ~400ppm (IIRC). In other words, we're already past the steep part of the curve to where increasing CO2 will no longer make much of a difference to temperatures.

If Congresscritters were intellectually honest on the topic of "climate change" they'd admit to this and stop with their boondoggles to curb CO2 production. The global climate is so vastly complex that to say we understand even a tiny fraction of how it works is hubris. I remember the story of Icarus.

And all of that ignores the fact that we don't even know if the current global climate is really at an optimum or if warmer or colder would be of a net benefit. Frankly, if I had to choose I prefer a warming world over a cooling world. Cold makes it harder to grow food, and more people die from cold exposure than heat. Plus, warmer climates have been well correlated to increased prosperity so a warmer planet would make it easier to deal with helping those whose locales are harmed by the higher temperatures.

Posted by: Andrew Upson | July 19, 2012 2:30 PM    Report this comment

"All I know is my Camry (not a Prius) hybrid is a wonderful car that I think is well into the mainstream of technology rather than an early adopter novelty. Everything about it is equal or superior to the IC only Camry (the best selling car in the world for many years now). "

I haven't driven the new Camry (IC or hybrid) but I do own a 1997 Camry. It gets around 27-30mpg combined city/hwy. So I'm skeptical of the 20mpg you claim for the new IC Camry. But I haven't looked into them, so you may be right. Still, the extra cost for a hybrid to gain 5-8mpg seems pretty darn steep to me.

The Prius that I have driven (corp. car) was terrible and gas milage in the mid-40's over 3 tanks worth was a pipe dream. High 30's, sure. But my 1992 Civic would do that (until it got over 170k miles anyway), and slug though it was it was still a lot more fun to drive.

Posted by: Andrew Upson | July 19, 2012 2:41 PM    Report this comment

"I do know my hybrid Camry passes a lot more gas stations than a pure IC powered one. Mine gets around 35 mpg while the IC only gets around 20."

Only 20mpg from a 3.something-liter V6? I get that much (and more, if it's all highway) in my V8 Mustang. But then, I can drive sedately during the work week, when I'm in no particular hurry (or just plain can't go fast due to traffic).

Could it be that parallel/series-parallel hybrid cars encourage drivers to drive more sedately than their IC-powered siblings? I recall a test that was done, where a BMW M3 was tasked with simply keeping up with a Prius drive all-out on a track, and the M3 actually returned the better mileage. So it's really more about how you drive.

Posted by: Gary Baluha | July 19, 2012 2:53 PM    Report this comment


The real key, it seems, is matching the propulsion system with your needs. Trains and submarines use series-hybrid technology because their propulsion system is typically running at lower RPMs where they can take advantage of the torque curves vs. IC engines. Where else do we see primarily low-RPM propulsive systems? Why, piston-powered propeller aircraft. So I could see there being an advantage to a series hybrid system. Whether the electric motor is powered by an IC engine or batteries, or something else entirely doesn't matter, so much as efficiency, range, reliability, and safety needs are met.

Posted by: Gary Baluha | July 19, 2012 2:56 PM    Report this comment

BTW, I looked up the price on and the regular IC Camry LE sells for ~$22-23k. The Hybrid for ~$26k. The IC Camry is rated 25 city/35 hwy. The hybrid is 46 city/35 hwy. Lets call it 30mpg on the IC and 40mpg on the hybrid. At 15000 miles/year you'd save ~$425/year on gas with the hybrid. But if you took the extra $3000 the hybrid would cost you to buy it and invested it at a measly 5% (yeah, current stock markets make 5% seem good, not measly, but I've got mutual funds that have averaged >8% over the last 13 years) it would take you 13+ years to break even. That's an awefully long payback time.

Posted by: Andrew Upson | July 19, 2012 3:03 PM    Report this comment

"Whether the electric motor is powered by an IC engine or batteries, or something else entirely doesn't matter, so much as efficiency, range, reliability, and safety needs are met."

Only problem is, do the math on an airplane. To cruise at, say, 150 knots--it needs about 140 HP or 70 percent of a 200 HP engine. Your car needs about 15 percent of its available HP to cruise on the highway, give or take.

The airplane hybrid needs to get that power from somewhere. If it's a serial, it has to generate about 100 KW continuously. That power has to come from somewhere and at 2400 RPM, an aircraft engine is in an efficiency sweet spot. I can see some efficiencies from serial hybrid--maybe 10 percent.

And let's not forget that locomotive serial hybrids exist not for efficiency but practicality. Mechanical drive trains from a diesel to the tractive wheels are heavy and ineffective. (They have been tried.)

Interestingly, since they have no batteries, locomotive hybrids convert regen braking energy into heat and reject it in a big fan grid on top of the locomotive. Prius drivers weep at the thought.

Posted by: Paul Bertorelli | July 19, 2012 3:27 PM    Report this comment

Paul B.: True, I did forget to do that math.

I remember reading a while back about an idea (which was also suggested above) about using electric motors in an aircraft's landing gear for taxiing around the airport, and starting the engines only just before being cleared for takeoff (or with enough time to ensure they're stabilized and running first).

Posted by: Gary Baluha | July 19, 2012 3:53 PM    Report this comment

It is hard to beat gasoline for energy storage.
Yes, gasoline made from oil from the ground emits CO2.
But if we made synthetic gasoline (or other hydrocarbon fuel) using carbon dioxide from the atmosphere and hydrogen from some energy source, the fuel could be carbon neutral.

Nothing is truly carbon neutral at this time, not even batteries.

Posted by: Bill Berson | July 19, 2012 6:52 PM    Report this comment

Bill, How about compressed natural gas (CNG)? That is readily available and cheap too. It doesn't have as much energy density as gasoline or diesel fuel, but there is lots of empty space in airplane wings to store more gallons of lighter fuel. And this stuff is readily available in every small town in the USA. People use it to grill their hamburgers.

Posted by: PAUL MULWITZ | July 19, 2012 8:06 PM    Report this comment

Andrew - My actual numbers with the Camry hybrid are different from the ones you found at Edmonds. It is true in either case that long haul driving on the highways is not the place where the hybrid shines. I use mine to go up and down the mountain on which I live to get to town and back. For longer trips I tend to use my plane instead (at least I hope to do that when it gets out of phase I testing). The plane is a max LSA and gets about the same fuel mileage as the Camry. Alas, it is with 100LL rather than good ol' mogas. On the bright side it doesn't need to follow roads and goes more than twice as fast.

My 97 Camry did get around 20 mpg on the same rough up and down in-town kind of driving. It had a 6 cylinder engine and my foot can get heavy at times. I suppose I am more gentle with the hybrid, but it still does a lot better in the mileage category.

I wouldn't think the hybrid advantage is in the small savings on fuel it gets. The noticeable difference is the range on a tank of gas. Instead of 200+ miles on a 16 gallon tank it gets around 500 miles on a 13 gallon tank. That means a lot fewer stops to refuel.

Posted by: PAUL MULWITZ | July 19, 2012 8:14 PM    Report this comment

@ Andrew Upson - spot on. Outside of Europe, even diesel variants seldom (if ever) make up the higher initial cost over a gasoline engine. I appreciate the people who've spent the money on hybrid cars however - they've basically chosen to contribute to the R&D effort for something that will presumably be more common in future. I guess it's a type of crowd-sourced funding.

I've recently been playing with one of those cool smart-phone-controlled RC Drones and it's got me thinking: Maybe it's a little pie in the sky right now but I can imagine a hybrid scenario in which a small engine generates power centrally, there is some storage via batteries/super-capacitors/whatever and then a bunch of lightweight, recruit-able electric propulsion units around the airframe to use that power as needed. I'm thinking of little electric motors with folding props and maybe electric motors in the wheels. For take-off you'd use more (maybe all) propulsive units and less or none during cruise/descent. It could be a single lever system. I can also think of interesting ways something like this could enhance redundancy and manoeuvrability.

Posted by: John Hogan | July 19, 2012 9:07 PM    Report this comment

Hi Paul M.
I think you may have confused compressed natural gas with propane.
CNG requires a very strong tank to hold the compressed gas (10,000psi) and is probably less suited to aviation for that reason. But propane (C3H8) is a liquid at around 100psi and has been used to power an airplane in the past (search Sport Aviation archive) and of course now powers thousands of trucks as well. I own a propane fueled truck.
Propane is almost like using liquid hydrogen without all the problems of hydrogen storage. In fact, a gallon of liquid propane actually holds more hydrogen atoms than a gallon of liquid hydrogen, believe it or not. I think the carbon slows the hydrogen atoms in propane. Propane is cheap now, but someday it could be made from carbon and hydrogen, as I mentioned, for carbon neutral.

Posted by: Bill Berson | July 19, 2012 11:03 PM    Report this comment

Thank you, Bill. I am indeed somewhat innocent of knowledge when it comes to all the variants of natural gas. There is CNG, LNG, propane, and who knows how many other variants.

For now I think it is impossible to beat gasoline (100LL) for aviation fuel. It does seem like a relatively small change to design a plane to use propane or other low pressure liquified gas. There really is plenty of spare space in airplanes - both the wings and fuselage. This doesn't work so well for cars because the space in cars is much more used up. I do like the idea of trucks running on this stuff. They have enough bulk that a large fuel tank doesn't really matter. I realized a while ago that electric power can work for small planes and cars but trucks probably will not use it until there is something really revolutionary in power technology such as small fusion reactors.

We wouldn't be looking for alternate fuels for GA if not for the environmentalists and their loathing for lead (TEL). As it is we can expect to need a replacement for 100LL in the foreseeable future. It just doesn't matter to those folks that the amount of this fuel used in the LARGE sky means there just isn't any significant accumulation or density of lead in the air because of this. Even if they don't manage to bludgeon the rest of the world into believing their nonsense there is only one plant today that can manufacture TEL and if it gets blown up or otherwise shut down there just won't be any 100LL again.

Posted by: PAUL MULWITZ | July 19, 2012 11:36 PM    Report this comment

"Propane is cheap now, but someday it could be made from carbon and hydrogen, as I mentioned, for carbon neutral."

Good luck with that for the next 100 years. As you know, propane is a byproduct of natural gas processing and gas is plentiful and getting more so. Some in the industry predict a price collapse greater than what has already occurred.

A year ago, gas was at $5/MBtu, last month it was at $1.80, although it's recovered some of that. Hydrogen is between $3 and $10, depending on the source and whose numbers you think are real. Propane is about $5.50, with relatively flat prices that seem likely to come down, given the gas glut.

But natural gas has sparked an astonishing energy transition in power generation. Just since 2005, coal's share of fossil generation has dropped from 70 percent to 52 percent, while natural gas share has gone from 20 percent to 45 percent. This is a huge deal, which not many people who don't follow the energy markets are aware of.

That's why I think all these hydrocarbon discoveries bode ill for the electric car market. Buyers will pay more for "feel good" green only to a certain degree. After that, they'll go with the most efficient choices and the hell with green. No one knows where that threshold is. If gas trends sustain and accelerate and the free market is left to its own devices, why are many people going to want hybrids or electric cars?

Only taxation or climate legislation seems likely to change that.

Posted by: Paul Bertorelli | July 20, 2012 5:07 AM    Report this comment

Paul B. I believe you are correct in general on your transportation energy future ideas. One exception is the hybrid auto issue. This is a technology that really works well for some people (like me). It isn't terribly expensive and it doesn't take any particular effort to use. Pure electric cars are a whole different issue. They have minimal and probably reducing range as the batteries age and require charging on a daily basis. This technology also has a sweet spot for Southern central city dwellers who drive only a few miles per day and don't mind the huge price for the batteries. Still, if your life style benefits from remembering to plug in your car at night rather than finding a gas station every few days or weeks then you might like this approach.

I agree with you that cost is an important part of this whole equation. For light planes the electric power option seems best suited for the primary training scenario. With one battery pack charging while the other is out flying a trainer can stay in use with nearly zero fuel cost. When you compare that to perhaps $30 per hour for avgas you can justify a large initial hardware cost. These planes will probably not be terribly impressive in speed, load capacity, or range but that is not particularly interesting in a primary trainer. The biggest hourly cost will be instructor. Nobody knows if there will be a huge overhaul cost but the motors and electronics won't need much. Batteries are just an unknown for now.

Posted by: PAUL MULWITZ | July 20, 2012 5:34 AM    Report this comment

Battery-powered airplanes face two stubborn hurdles, each rooted in physics and p-chemistry:
1. The weight for each unit of available energy that gets carried aloft.
2. The interval that's required to recharge the battery.
For LSAs that are operated in personal use, these obstacles may not be disqualifying. For applications that require greater payload and/or range, right now they are. The recharge interval is the most damning constraint for commercial use. It's hard to make money with a piece of capital equipment whose available duty cycle is so low.

For the foreseeable future, this Kool Aid has little practical appeal.

Posted by: Tom Yarsley | July 20, 2012 6:24 AM    Report this comment

Thomas, I see all that changing with the next advance in battery technology. I expect higher energy density batteries that cost less than today's offerings. I don't know when this will happen but I think 5 years or less is very likely.

Once the battery obstacle is reduced electric light planes will be much more practical. The recharge time issue is relatively easy to solve. Charge rates can usually be anything you want and spare battery packs are practical if the battery cost is low enough.

I do agree with you that electric planes tend to become less practical as you increase the airplane size and/or performance. The more power you need to achieve your cruise performance and weight lifting capacity the larger the battery packs get. At some point this is overwhelming. That point changes with battery technology improvements, but even though I expect improvements soon they will only be evolutionary rather than revolutionary.

Posted by: PAUL MULWITZ | July 20, 2012 6:33 AM    Report this comment

Paul, charge rates can't quite be anything you want. They vary with chemistry. And there's a difference between energy density and power density. Think of energy density as how much water the glass can contain and power density as how fast you can pour it out.

In Li-ion, high energy density batteries have limitations on how fast they can discharge, which means you need to carry a lot more weight to have endurance. Lower energy density batteries tend to have better power density; you can discharge them fast, but they don't hold as much overall energy.

Complicated tradeoffs, although none are showstoppers, I'd guess.

Posted by: Paul Bertorelli | July 20, 2012 7:02 AM    Report this comment

Propane, if available at a cost competitive with gasoline or Diesel fuel, is a good fuel for applications like school buses, public transit buses, trucks, or cars. But not airplanes. C3H8 is too volatile (i.e., dangerous in crash situations) for that application. I believe that if the price of avgas gets high enough, we should look at modifying aircraft piston engines and fuel systems to run on E30, if not E85 where the gasoline component would be mogas ("motor", i.e. automotive gasoline) whose basic antiknock rating is no higher than 93 if not 87. I'd like to see EAA recognize, in a Theater of the Woods ceremony (those who have been to AirVenture Oshkosh will know what I mean), whoever does the most first-rate job of modifying an aircraft like the C-172 or Piper PA-28-140 or 180, to run on mogas-ethanol blends.

As for electric aircraft: Whichever individual or aircraft manufacturer (i.e. Pipistrel) who does the best job of designing an original aircraft or modifying an existing airframe to run on electric power using batteries (most likely Li-ion), should also receive special recognition from EAA.

EAA AirVenture 2012 starts this weekend. Wish I could be there **sigh**

Posted by: Alex Kovnat | July 20, 2012 7:08 AM    Report this comment

I don't know if propane is the best fuel to manufacture or not. Propane has much more energy per pound than ethanol (more than gasoline also). Propane is octane 120 and has no lead, so should not be discarded as a future fuel contender for aviation just yet.

But my main point was: any liquid fuel is better than batteries for aviation. If legislation prevents the use of natural fossil fuels because of CO2 emissions, than liquid fuel could be made from atmospheric carbon that is carbon neutral.

Posted by: Bill Berson | July 20, 2012 9:17 AM    Report this comment

In late 1960's early 70's a space probe Viking 10 was sent on a lifetime journey carrying a unique battery. I can't remember its weight but it is said to be the size of a grapefruit, will deliver 100Kw, for 10yrs, only problem was the isotopes that were used to generate that power. The question I have is what happened to that technology I mean for all its problems the size and power says it should have been further developed. I do know that Viking 10 was until recently still sending messages back to us from very deep space where solar panels don't work.

If I was a betting man I would wager that this technology interfered with the oil companies and got buried somewhere.

Posted by: Bruce Savage | July 20, 2012 9:25 AM    Report this comment

It's not a battery, exactly, Bruce. It's a plutonium power cell. The technology still exists. The Russians used it for their deep space satellites. The U.S. Galileo probe has plutonium RTGs, also. (Radioisotope thermal generator.)

I don't know if it's 100Kw though. That's a lot of power for a satellite.

Posted by: Paul Bertorelli | July 20, 2012 9:41 AM    Report this comment

You mean it can pop out of the wood work sometime and we will all be flying around with nuclear bombs aboard. The 100 Kw was what was quoted at the time. Imagine with a 150HP aircraft would need only one unit to fly. But then at what cost :-)

Posted by: Bruce Savage | July 20, 2012 9:49 AM    Report this comment

My apologies - I must be in an argumentative mood.

Paul B - The normal rate to charge any battery I have run into is the same as the allowable discharge rate. This is not about the chemistry but rather the electrodes. The problem that must be solved is to have the charger shut off quickly when the charging is completed. There are severe thermal problems that get worse with higher charge rates if you miss this point.

Alex - I don't think you will see the ceremony for anyone using alcohol in airplanes. That is against FAA rules. The FAA has (correctly) determined that ethanol is damaging to airplanes and forbids its use. On the electric airplane front I don't think the EAA recognizes any accomplishments but there are other organizations that do that as well as offer large prizes each year. I'm not sure who they all are but one is called Lindbergh and another CAFE (sp?). Pipistrel has been winning prizes from both of these outfits lately.

Posted by: PAUL MULWITZ | July 20, 2012 10:13 AM    Report this comment

All of this talk about "modifying" airplane engines to run on canned mouse farts (or anything other than 100LL) leaves me asking this question: who will pay the bill that will accompany the modification of MY aircraft engine? The Obama administration already has neutered my perfectly good $4,000 Loran C navigator – imperiously insisting that I should spend another $4,000 (or much more) on a GPS navigator, which will provide no real (and certainly no SOUGHT) increase in service. Soon comes ADS-B, which will leave ATC absolutely blind each time that its airborne or groundbound equipment fails. Priced one of those new ELTs lately? More $$$.

User fees? From where I sit, we already have them – they're just cloaked in the guise of equipment requirements. Now, we’re going to have to “modify” our engines and their associated fuel systems.

Is all of this (or even ANY of this) actually NECESSARY, in the cause of safety? Somebody, please convince me that it is. While you’re at it, please explain to me why by 2020, I’m going to have to spend more on equipment upgrades than what my airplane is worth in today’s marketplace. I’m waxing for Iowa, Kansas, or Nebraska, and a nordo Cub.

Posted by: Tom Yarsley | July 20, 2012 10:19 AM    Report this comment

Bruce - I'll take the other side of that bet. I can't imagine why an oil company would care about batteries at all (unless they could use them on their remote wells).

If Paul B is correct about the plutonium basis for the "Batteries" you mentioned then I would believe it is the plutonium that was the problem. It has two very large problems: It is probably the most poisonous substance known to man; and the US government is even more paranoid about letting anyone have plutonium in any quantity than the Greenies are about lead in the atmosphere.

Posted by: PAUL MULWITZ | July 20, 2012 10:22 AM    Report this comment

One more plutonium comment -

I understand the French have a process for reprocessing spent nuclear fuel rods and recovering the basic material for new reactor fuel. The US government won't even consider allowing use of the French process here because it separates out plutonium (a byproduct of nuclear power reactors and the primary output of breeder reactors) and they just can't stand the notion of allowing any plutonium to be isolated. They have nightmares about terrorists or other bad guys getting their hands on the plutonium and using it the way the US government does - to create nuclear weapons.

The result is we have huge "Cooling ponds" near each nuclear power generating reactor where endless quantities of spent fuel rods are stored. US energy policy (if there is one) is that these must stay there until another solution for this incredibly toxic waste can be found. This is the biggest problem with nuclear power generators and makes our little problem with possible disappearance of 100LL child's play by comparison.

Posted by: PAUL MULWITZ | July 20, 2012 10:30 AM    Report this comment

"This is not about the chemistry but rather the electrodes. "

For Li-ion, the electrodes are the chemistry, Paul. The trick in Li-ion--and where the electrons come from--is to move the ions back and forth between the electrodes. They go one direction in discharge, the other for charging. The more unimpeded their movement, the better it all works.

I'm told by the Li-ion experts I interviewed that the Li-ion charge cycle is a two-stage affair that takes several hours. Short cutting that will result in either a lesser charge or shorter cycle life. You can't make the charge time anything you want. And Li-ion can't do trickle charging and absolutely can't tolerate overcharging, hence the need for electronic protection.

This article explains differences in charging times and this one explains the Li-ion charge cycle.

Key point here is you can't just jack up the current and voltage and charge it in 10 minutes.

Posted by: Paul Bertorelli | July 20, 2012 11:37 AM    Report this comment

Forgot to strip the http.

Posted by: Paul Bertorelli | July 20, 2012 12:02 PM    Report this comment

Paul B. I just took a look at your first referenced article "Best Battery". The first table presents Best Results for load current in terms of "C". What they don't tell you is "C" is the charge rate. The interpretation that works for me (and that I mentioned above) is that it is a good idea to charge your batteries and discharge them at the same rate. This applies pretty much universally to battery chemistries of all types.

If you look at it another way it turns out a light trainer with two battery packs could have one charging while the other one is flying. That would give you constant power so long as you don't try to use more than the battery pack holds on any flight. In actual practice you won't use up the whole pack capacity in a flight because that would mean a dead stick landing.

The common practice in consumer electronics is to charge at much less than the allowable rate. This makes for low cost and generally safe charging appliances but means recharging takes a lot longer than it might.

Posted by: PAUL MULWITZ | July 20, 2012 12:15 PM    Report this comment

Paul M - The nuclear reprocessing issue is a Carter Exec. Order that was never recinded by any succeeding president. In theory Pres. Romney could fix that on Jan 21 (that might be wishful thinking, on at least 2 levels, but what the heck).

There's some pretty cool tech in nukes that under development. Look up travelling wave reactors, and pebble bed reactors.

Also if you look at the trajectory of improvements in battery technology we've gone from 25 W-hrs/kg in Thomas Edison's day to supposedly 400 W-hrs/kg today. Even assuming that high figure is accurate (200 W-hrs/kg is probably more defensible) that's only a 16x improvement in 140 years.

Computers, which follow Moore's Law would see a 16x improvement in speed and capacity roughly every 6 years.

Batteries do not follow Moore's Law as they are constrained by the laws of chemistry, physics and thermodynamics. I would not expect to see battery capacity improve enough to make widespread EV's in GA possible until my (eventual) grandkids are contemplating retirement (my oldest kid is only 8 right now).

We'd need to either see some major game changing technology come along, or a massive acceleration in the pace of battery improvements to see non-IC powered airplanes become mainstream in my lifetime. Less than 10 years from now, nevermind 5, is a pipe-dream.

Posted by: Andrew Upson | July 20, 2012 1:09 PM    Report this comment

Thank you Paul B appreciate you finding the article for me. Methinks there was a typo in the article I read all those years ago and a K came between the 100 and the w.

Posted by: Bruce Savage | July 20, 2012 1:15 PM    Report this comment

Oh, and as far as RTG's go, they only use those on satellites that go out to Mars and beyond. At those distances from the Sun the size of solar array required to power the satellite becomes prohibitive. And the lifespan of an RTG makes it about the only viable power source given how long it takes to go out past Mars to the other planets (or like V-ger outside the solar system entirely).

Posted by: Andrew Upson | July 20, 2012 1:30 PM    Report this comment

Andrew - your long discussion of battery development assumes some kind of slow and steady process. That just isn't the way it is. It takes a considerable amount of research and development to get to a new battery chemistry/technology. It is not just a matter of waiting around for the clock to mark off time for another improvement.

The world is currently full of both government and automotive scientists and engineers devoting their lives to the next battery improvement. There is no way to accurately predict when they will make the next breakthrough, but it seems likely they will accomplish just that. I really think 5 years is a conservative guess for when we will see much better battery technology for automotive and light aircraft use.

Posted by: PAUL MULWITZ | July 20, 2012 2:11 PM    Report this comment

"five years a conservative guess"

Maybe. Maybe not. A lot of it depends on things we can't predict, like how fast EVs will be adopted, whether China decrees them as mandatory to solve its pollution mess, how real the 400 Wh/kg pouch is and whether lithium-air can get off the research bench and into vehicles. Battery researchers say that one is a ways off.

Worth pointing out is that when Pipistrel started with the G2 Electro in 2007, they had 163 Wh/Kg batteries and now, five years later, they have 185 Wh/Kg. People in the industry seem quite reticent to predict doubling capacity over any foreseeable term.

At CAFE, there was a presentation of so-called 10X batteries, but that lab capacity is predicated on just the anodes. The cathode still needs an upgrade. It's unknown if it's commercially feasible and/or when.

But it's all moving forward. Batteries will get there and, in some ways, already are. It's exciting stuff, really.

Posted by: Paul Bertorelli | July 20, 2012 2:30 PM    Report this comment

"your long discussion of battery development assumes some kind of slow and steady process. That just isn't the way it is. It takes a considerable amount of research and development to get to a new battery chemistry/technology. It is not just a matter of waiting around for the clock to mark off time for another improvement."

Except that it is, basically, a slow and steady process. All the work currently being done is great, and will speed up the process a bit compared to when comparitively few people really cared (i.e. more than 10 years ago). But as Paul B stated, in 5 years the Pipistrel batteries increased capacity 13% in 5 years. At that rate it'll be another 35 years before they get over 400W-hrs/kg in a battery that's actually useful outside a controlled lab experiment. Now, they probably won't follow such a straight line progression, but it would be unwise to assume that 13% in 5 years will lead to >100% in another 5 years.

Having read the assesments of those actually in the battery industry I'll take their predictions over yours.

I guess in 5 years we'll see who's right. Meanwhile I'll not be holding my breath.

Posted by: Andrew Upson | July 20, 2012 4:20 PM    Report this comment

The electric radio controlled model aircraft community has found workable charging/discharge rates for the Li-xx batteries. About 10 years ago they were fighting fire hazard issues whilst charging/discharging. Now resolved with smart chargers and ECMs that control discharge cycles. I've seen some photos of damage incurred. They burn like phosphorus, ordinary extinguishers cannot control them.

Some of the planes they fly now are impressive in their flight characteristics and duration. They are all overpowered.

The issue I see in the future is that China has been negotiating contracts around the world for rights to mine lithium. They also have considerable reserves of their own.

We have considerable reserves in the U.S. but we don't mine it any more for environmental reasons.

Posted by: Edd Weninger | July 20, 2012 4:35 PM    Report this comment

By the way, I'd recommend Fletcher's book if you want to gain a realistic understanding of this technology, how fast it will advance and where it's going. Very even-handed treatment.

Posted by: Paul Bertorelli | July 20, 2012 4:48 PM    Report this comment

Swapping battery packs is an interesting option, IF:
1. You're remaining in the local area; always returning to "home base" for the swap operation.
2. The swap is conducted indoors, and does not require the operators to possess Hulk-like strength.

Both of those constraints mean that battery-powered aircraft are limited to essentially LSA-like vehicles, in local operations only. Pretty much like battery-powered cars. You can forget cross-country flight, unless you’re willing to “trade in” your lovingly-cared-for, nearly-new batteries for….. Well, you get the picture. And then, there’s this: how will you know how much of a charge your mystery-swap batteries actually hold? Remember, charge equals endurance… At least a fresh tank of gasoline promises fairly reliable endurance behavior. When your battery-powered car unexpectedly poops out, you can pull over to the side of the road and cry. And call AAA. Still feeling good about charging off into the clouds in an electric airplane (please pardon the pun)? The failure-mode-analysis looks grim.

Posted by: Tom Yarsley | July 21, 2012 7:09 PM    Report this comment

Our aircraft already includes a Li-ion battery! Later-model Diamond DA40 and DA42 aircraft each have a backup battery pack that's used after alternator and main battery failure to power the backup AI and instrument lighting. The Li-ion pack is located just behind the instrument panel.
It must be replaced every 2 years even if never used, and the irony is that Diamond has to ship it from Canada using expensive special handling, since it's not allowed to be shipped by airplane!!! (Yet it's intended to be installed in an airplane!) Go figure...

Posted by: DAVE PASSMORE | July 22, 2012 9:13 AM    Report this comment

Paul Mulwitz wrote on July 20:

> Alex - I don't think you will see
> the ceremony for anyone using
> alcohol in airplanes. That is
> against FAA rules. The FAA has
> (correctly) determined that
> ethanol is damaging to airplanes
> and forbids its use.

Ethanol is indeed damaging to airplane engines and fuel systems, if said engines and fuel systems have not been suitably modified. I believe that EAA should discuss with the FAA the possibility of allowing aircraft so modified, to be authorized to fly as experimental aircraft (The "EA" part of EAA), though not Part 23 certified aircraft until of course, it proves possible for such aircraft to "graduate" from experimental to certification-worthy status.

Posted by: Alex Kovnat | July 23, 2012 7:19 AM    Report this comment

The reason electrics is the only way to go in the long term is because of the almost insane benefits it has as a prime mover. Energy storage will be solved in the future, either with hybrid gensets or new batteries. Whatever it ends up being, the brushless electric motor is unbeatable:

No TBO, no wear, no decrease in performance with altitude, no carb ice, no need for CS speed props, no LOP/ROP, highest power-to-weight ratio of any motor, no mag checks, no run-ups, instant power, nothing that can break, silent and neighbour friendly, no rich cut, no CO-poisoning, no shock cooling, built in fadec, no oil drippings, no stains, no dirty fingers, no vibrations, no leaning, etc etc.

The list goes on and on. No matter what one thinks of energy storage or how the energy should be provided, it's no denying that the electric motor is the future for all air travel.

Posted by: Adam Frisch | July 23, 2012 8:31 PM    Report this comment

Alex, I am afraid I must disagree with your desire to use ethanol in airplanes. This is a horrible idea for just about any reason you can think up.

Ethanol is food. It should be used to feed people rather than fuel airplanes or cars.

Ethanol has less energy per gallon than gasoline. By adding it to fuel you reduce the range of the vehicle so contaminated.

It takes more fossil fuel to produce Ethanol than the fuel displaced by the Ethanol. This means using Ethanol is bad for the environment because of excess fossil fuel use.

Ethanol absorbs water. When it is cooled (e.g. by increased altitude in an airplane) the water comes out of solution and becomes a lump of liquid water at the bottom of the fuel tank. It can freeze and stop fuel flow. It can be pumped to the engine instead of fuel. The net result is the same - a dead stick landing.

Instead of pushing for flying planes on alcohol I think we would do a lot more good by removing the stupid government mandate to use this inferior fuel in cars.

Posted by: PAUL MULWITZ | July 23, 2012 8:49 PM    Report this comment

"'s no denying that the electric motor is the future for all air travel."

Unless you have a 10,875-mile-long extension cord handy, you won't be getting very far into that 1/2-global-range flight powered by magnificent electric motors.

Those motors produce surprisingly little movement without a steady source of power. Do the math - calculate how much juice you'd need to haul 400 people and their belongings half way around the planet. Find ANY source of electrical power that's sufficient. Weigh it. Add its weight to that of the aircraft. Lather; rinse; repeat.

Posted by: Tom Yarsley | July 24, 2012 6:08 AM    Report this comment

Adam - Until batteries get over 1KW-hr/kg there's no hope for them to be at all acceptable in the marketplace. At that energy density you could start to make the case as the electric motor+batteries would have a weight close to IC engine+gas for the same mission.

Maybe that will happen in my (useful) lifetime, but I'm skeptical.

But you'll still have the issue of re-charge time, battery degradation, environmental effects of battery and motor manufacture and disposal, the economics of the batteries and so on that will all work to keep widespread EV's from taking off (pun intended) in GA.

Posted by: Andrew Upson | July 24, 2012 11:31 AM    Report this comment

You guys are not listening to what I'm actually saying. The way the electric motor is powered is incidental - it might be batteries, gensets, APU's, fuel cells, whatever in the future. We don't know yet. But as a prime mover turning the fans or the props, believe me, it will be electric. And sooner than people think.

Let's just look at a twin engine turbine helicopter today, as an example. Today the two gas turbines drive a complicated and prone to failure reduction gearbox that then runs the main rotor. Not only that, another up-geared shaft runs all the way to the back to run tail rotor, adding weight, vibrations and friction. In the future, the main rotor will be driven by an electric motor, the tail rotor by another electric motor and the power generation will be done by gas turbines running generators. This will not only be lighter, but much more safe as if the generators should fail, you still can land on the power in the battery.

Same examples can be made for airplanes. The big thrust producing fan in a fanjet in airlines would be powered by electrics, the hot section in the back would drive a genset and in effect act as APU. By decoupling the power generation from the propulsive stage, you can now gain much more flexibility etc.

It's gonna change, so resistance is futile. Get onboard or be a dinosaur;)

Posted by: Adam Frisch | July 26, 2012 6:00 AM    Report this comment

Gotcha Adam we are going to throw out the heavy drive chain (or shafts) and gear boxes and replace them with electric motors and generators. The motors I know are available at a price but the generators? And how does all this translate to Kw/lb/US$

Posted by: Bruce Savage | July 26, 2012 6:22 AM    Report this comment


So, a winged diesel-electric train with battery back-up, eh? When Boeing and Pratt & Whitney show some interest, so will I. The physics of efficiency don't support it, even on a theoretical basis. Then there's the paradigm of serial multiple points of critical-path failure - which increase the risk of system failure by the square of their count. This could be mitigated to some extent by pooling the power-generation sources' outputs before distributing the power to the various motors. Freewheeling multiple motors driving each fan shaft is another mitigating approach. But any of these will add weight and complexity. I'll grant you this: it stands a better chance of adoption in a rotary-wing vehicle, than in an airplane.

Posted by: Tom Yarsley | July 29, 2012 8:17 AM    Report this comment

Adam Frisch writes:

"The big thrust producing fan in a fanjet in airlines would be powered by electrics, the hot section in the back would drive a genset and in effect act as APU. By decoupling the power generation from the propulsive stage, you can now gain much more flexibility etc. "

If anybody builds an actual flying prototype of the above and brings it to Oshkosh, I would be delighted to look at it in spite of my reservations about its practicality. As an member of the Southeast Michigan automotive engineering community, I have to say that series hybrid electric cars are not in production, but parallel and torque-split hybrid electric cars (the most famous of which is the Prius) have been in production since the late 1990's. The series electric concept, i.e. engine --> generator ---> traction motors ----> drive wheels has been used for Diesel-electric railroad locomotives since the 1930's. But that's because you would have a real Excedrin headache if you were to drive the four or six axles of a Diesel locomotive mechanically.

As for using the series drive concept for helicopters: I was born in Illinois rather than Missouri, but you'll still have to show me.

Posted by: Alex Kovnat | July 31, 2012 1:55 PM    Report this comment

I most certainly have been listening to what you're saying Adam. Up until now it's all been battery based electrics, with maybe an occasional vague reference to other technologies. My arguments against that system, in particular the economic issues, have yet to be addressed by you, over several threads.

As to your other ideas, color me still skeptical. I have a hard time seeing how what you propose would actually be of any benefit to aviation. For that to happen the hybrid-electric system, whether gas turbine or something else, would have to be more fuel effecient (plausible), safer (debateable), less costly (unlikely - and I'm being kind), lighter (show me how and I'll believe you - but I doubt it), be more durable and reliable (some parts, sure, others not so much), reduce maintenance expense (plausible I suppose), and so on.

In theory, everything works in practice. But reality can be a harsh mistress.

Posted by: Andrew Upson | July 31, 2012 6:16 PM    Report this comment

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