Is electric propulsion worth it?

[Aviator168]

I did some numbers on Randall Fishman's aircraft. He indicated that it costs $10,000 to replace the battery packs. For each full charge, the battery packs can provide 2 hours of flight time. If translated to gas usage, it would be $12 @ today's gas price. Randall also claims the battery has 800 cycles. That would be 800 flights of 2 hours and about $9,600 for gas if an ICE of the same power output is used. That's about the price of replacing the battery pack. I have not include the cost of charging the battery and the maintenance of the ICE. For the sake of the conversation, let's say they are about the same, give and take a few. Here is the kicker, the electric motor is a lot less expensive than a gas engine and virtually no maintenance required, especially when the power of the engine goes up. Your thoughts?

 

[N8053H]

While its true the cost of maintenance is lower using electric. But to say the electric motor has virtually no maintenance really is not correct. Sure it has less then a combustion engine but it will still have maintenance.
The cost of batteries has always been an issue. One must also remember as the batteries age they are not as efficient.

Tony

 

[danmoser]

I did some numbers on Randall Fishman's aircraft. He indicated that it costs $10,000 to replace the battery packs. For each full charge, the battery packs can provide 2 hours of flight time. If translated to gas usage, it would be $12 @ today's gas price. Randall also claims the battery has 800 cycles. That would be 800 flights of 2 hours and about $9,600 for gas if an ICE of the same power output is used. That's about the price of replacing the battery pack. I have not include the cost of charging the battery and the maintenance of the ICE. For the sake of the conversation, let's say they are about the same, give and take a few. Here is the kicker, the electric motor is a lot less expensive than a gas engine and virtually no maintenance required, especially when the power of the engine goes up. Your thoughts?

Electraflyer's 5.6 kWh Li-Ion battery costs $8,500 .. which is ~1,500 $/kWh.
At the other end of the spectrum, LG-Chem batteries used in the Chevy Volt & other e-cars cost ~250 $/kWh. .. that's 6 times cheaper!
The LG-Chems are about 50% heavier, but are a bit more robust in terms of charge-discharge & balancing.

RC LiPo batteries are as lightweight as Electraflyer's, and somewhere in between on cost at ~$500 $/kWh, and they can put out very high power for short periods.
However, their longevity and robustness are questionable.. reports are widely varied.

Tesla is now entering a joint venture with Panasonic to manufacture e-car batteries in the US.. the economics of electric propulsion just keeps getting better!!

 

[haiqu]

Simple answer: No. Not even for cars.

 

[Aesquire]

I think in the near future it's "practical" for self launch sailplanes, but you need better batteries before it's good enough for a recreational flyer.

Green Flight Challenge: It Might Look Like a Quickie… – CAFE Foundation Blog

A hybrid may be almost practical. I think because of the typical flight profile for GA planes a light, robust super capacitor would be ideal.


So, my not so humble opinion is almost, but not yet.....

 

[Sockmonkey]

It does have the advantage that you can use multiple smaller engines and props when ground clearance is an issue with a minimal increase in complexity over a single engine.
I like the idea of a hybrid setup. It's easy to make it so the ICE is sized for cruise and use a small battery pack for additional "burst" power on takeoff.

 

[danmoser]

I did some numbers on Randall Fishman's aircraft. He indicated that it costs $10,000 to replace the battery packs. For each full charge, the battery packs can provide 2 hours of flight time. If translated to gas usage, it would be $12 @ today's gas price. Randall also claims the battery has 800 cycles. That would be 800 flights of 2 hours and about $9,600 for gas if an ICE of the same power output is used. That's about the price of replacing the battery pack. I have not include the cost of charging the battery and the maintenance of the ICE. For the sake of the conversation, let's say they are about the same, give and take a few. Here is the kicker, the electric motor is a lot less expensive than a gas engine and virtually no maintenance required, especially when the power of the engine goes up. Your thoughts?

Whether electric propulsion is "worth it" or not really depends on what "it" is.
According to this:
Cost of Power from Batteries and Other Sources - Battery University
..the cost of power to recharge the battery is about 1/5 the cost of current technology Lithium-chemistry battery replacement, on a per hour of use time basis.
This is almost a wash with gasoline-ICE engines on life-cycle cost per flight hour basis today.
So the cost of battery recharging power is very low..
And rapid advancements in battery technology are continually lowering their cost and extending their useful lifetime.

It has already been worth it for RC planes.
It is now worth it for motorgliders and ultralights.
It will soon be worth it for LSAs and other light aircraft.
It may never be worth it for commercial airliners.

 

[BBerson]

The cost of battery replacement is a big issue.
The manufacturers will not guarantee the number of charge cycles. You can't trust their numbers.

With RC models it is not uncommon to see a battery fail in say 10 flights. Nobody keeps track, they just buy a spare battery.
The ESC (electronic speed controller) often fails. The motors fail. All because in aviation (model or full scale) the power is often pushed beyond the limit of the battery, ESC, motor.
Replacement cost hardly matters for $10-50 electric models.
But the giant scale guys are mostly returning to gasoline power.

One of my RC students had his ESC fail on first flight. Very frustrating getting a new part from the company and waiting a month.

The glow fuel trainer goes years after year with only minor adjustments.

Dale Kramer (electric experimenter) does a cycle test on a sample battery in real load conditions before he spends
$ thousands on batteries..

 

[autoreply]

It has already been worth it for RC planes.
It is now worth it for motorgliders and ultralights.
It will soon be worth it for LSAs and other light aircraft.
It may never be worth it for commercial airliners.

Nice summation. I'd add the "it will never be worth it for any decent (100 mile) range.

But most importantly, they work. Reliability in service for the few electric planes is a few orders of magnitude better as their reciprocating brothers and sisters. Especially for some missions (powered sailplanes) that's a huge win.

 

[Dana]

Also consider charge time, which in most cases makes cross country flight impractical. Even if you have high amp electric service available, it's still hours to recharge vs. minutes to fill a gas tank.

Dana

 

[Dana]

Also consider charge time, which in most cases makes cross country flight impractical. Even if you have high amp electric service available, it's still hours to recharge vs. minutes to fill a gas tank.

Dana

 

[Aesquire]

I've looked at the lowest end on Electrics... it's a money issue there too.

Looking only at ultralight trikes, Pt. 103 legal. In particular, one you can soar with and not just cruise the local valley.

With 5 gallons of fuel, range is not awe inspiring, but call it a max of 2 hours @ 45mph?

Which is what is claimed for the Electra Flyer Trike.

ElectraFlyer.com - Price List

Electric runs about $!0k for chassis, wing, motor. PLUS battery pack & charger $9-9.5K. Total just under $20k for comparable range. Add an extra $9K for a spare battery and you have a pretty good day of local soaring. Or a 35 mile out... and return, then soaring in the afternoon.

A comparable IC version would be the ATF from Northwing.

North Wing · Light Sport Aircraft, Ultralight Trike & Wing Prices · Amateur Build Kits

$13-14K complete with engine.

So..... less than twice the price ( impressive for bleeding edge tech ) and the recharge time problem, but much quieter, and you get to play holier than thou.

I don't know what tech snobbery is worth to You, so do your own math. ( It's worth SOMETHING, or no one would build a "your trigger word here" .)

 

[Brian Clayton]

My opinion....no. While I dont have a electric airplane, I do have a factory s10 I converted from lead acid to LiFePo batteries (208 45ah cells). I will admit its neat. The parts cost was about 12,500, range is 90-100 miles. I wouldnt do it again, it was a waste of time, energy and money. And it is still eating all of those. The only way full electric will ever become more than a play pretty is for the batteries to come way down in price and for the related electric controls to become a lot more robust (they like to flake out for no reason). I relate it to buying all of the gas for a vehicle up front, whether you use it or not. Just my opinion, but I am not sold that it is the way of the future. Too many things to go wrong.

 

[philn]

Were not there yet but but on the verge of batteries that hold 2 to 4 times the charge of existing batteries and costing around $100 $/kW.

hhttp://thinkprogress.org/climate/2014/08/31/3476807/tesla-electric-car-battery-breakthrough/

 

[JamesG]

Yeah, its IF the hype and promise of graphine holds up. It is a potential game changer for a lot of things but esp. electric aircraft because besides the ridiculous storage capacity per weight, it can be structural and photovoltaic-ally self charging at the same time.

 

[danmoser]

I've looked at the lowest end on Electrics... it's a money issue there too.

Looking only at ultralight trikes, Pt. 103 legal. In particular, one you can soar with and not just cruise the local valley.

With 5 gallons of fuel, range is not awe inspiring, but call it a max of 2 hours @ 45mph?

Which is what is claimed for the Electra Flyer Trike.

ElectraFlyer.com - Price List

Electric runs about $!0k for chassis, wing, motor. PLUS battery pack & charger $9-9.5K. Total just under $20k for comparable range. Add an extra $9K for a spare battery and you have a pretty good day of local soaring. Or a 35 mile out... and return, then soaring in the afternoon.

A comparable IC version would be the ATF from Northwing.

North Wing · Light Sport Aircraft, Ultralight Trike & Wing Prices · Amateur Build Kits

$13-14K complete with engine.

So..... less than twice the price ( impressive for bleeding edge tech ) and the recharge time problem, but much quieter, and you get to play holier than thou.

I don't know what tech snobbery is worth to You, so do your own math. ( It's worth SOMETHING, or no one would build a "your trigger word here" .)

It's not about tech snobbery or holier than thou.

Look at an operating cost comparison, not just initial purchase, it is an increasingly compelling story for electric propulsion .. electrical energy recharge cost is a small fraction of gasoline fuel cost per kWh.

Look at maintenance and replacement costs.. batteries don't last forever, but neither do piston rings, starters, heads, cranks, rods, spark plugs, belts, cams, gaskets, hoses, oil pumps, fuel pumps, ignition systems, exhaust systems. etc.

Look at the reliability of cold in-flight restarts (like motorgliders) .. huge advantage for electrics there... instant full power available.

Look how many carb-icing accidents could be avoided.

Look at the very low vibration and noise of electric motors, allowing a more pleasant piloting experience on light, high-powered aircraft, with less critical engine mounting and more propeller choices .. better relations with airport neighbors too.

Look at high altitude performance.. gasoline engines loose power when they gain altitude.. electric power is essentially unaffected by altitude .. more power to clear mountains, avoid weather, and/or operate out of higher elevation airfields.

And future prospects for better battery technology with lower initial costs & longer lifetimes are excellent, so your performance and economics get better every year.

I used to turn my nose up at electric plane prospects too, but advancing technology keeps making electric planes more and more appealing.
So much so that I recently decided to go to electric propulsion on my motorglider project.

Electric propulsion is obviously not for every airplane, or every aircraft mission today .. particularly long-range, long-duration.. but fuel cell advances in a few years may change all that too.

Electric planes are here now, and their implementation is growing fast .. stubborn attitudes about their worth will either change, or become increasingly incorrect.
Keep saying "not yet," and you may be left behind.

 

[BJC]

"Worth it" is a personal judgement, not a financial analysis.

I live on a residential airpark, and would love to have an electric powered airplane capable of taking off and flying reliably for at least 45 minutes under power with a reasonable (for me) cost. Nothing out there currently meets my wants, so my answer to your question is "Not at this time, but I expect that it will be within a few years."

 

[danmoser]

"Worth it" is a personal judgement, not a financial analysis.

I live on a residential airpark, and would love to have an electric powered airplane capable of taking off and flying reliably for at least 45 minutes under power with a reasonable (for me) cost. Nothing out there currently meets my wants, so my answer to your question is "Not at this time, but I expect that it will be within a few years."

Any personal judgement of the worth of electric propulsion ought to at least include some sort of financial analysis .. unless you're filthy rich, and money is no object.

I know of some who plan to install electric propulsion on aerobatic airplanes .. a somewhat surprisingly good fit.
No inverted fuel systems, fuel sloshing, CG shifting, or serious cooling issues.
Also, precise and instantaneous control of torque & RPM is big advantage.
Usually, aerobatic pilots fly for only about 10-15 minutes at time anyway, with a long period of time in between flights to rest & recharge both the human pilot and the inanimate batteries..
Power-to-weight is very important... more so than range & endurance requirements.

If you have a strict range and/or endurance requirement, the suitability of electric propulsion depends mostly on the aerodynamic efficiency of your particular aircraft.
On an "average" airplane, you may be able to fly for up to an hour with current Lithium-based battery technology.
An e-powered sailplane can fly much longer than that, and can take advantage of thermal, ridge, or wave lift to extend its potential endurance to several hours.
A vintage biplane is probably too aerodynamically inefficient to fly any more than 30 minutes on electric power, and is probably not able to utilize lift to any significant degree to extend its endurance.

 

[BJC]

Any personal judgement of the worth of electric propulsion ought to at least include some sort of financial analysis .. unless you're filthy rich, and money is no object.

By "financial analysis" I was referring to benefit to cost ratio / break-even time / point of net benefit / etc. They all require a defined dollar value on the benefit stream resulting from the expenditure. My point is that the "benefit" of an expenditure for a personal airplane is a personal judgement.

We agree that cost is always a factor, and that it limits options for most of us.

 

[crytes]

In my opinion for electric to be viable with current technology would require use of hydrogen fuel cells which should solve both the problems of range and "recharge times", and if you utilize photovoltaic surfaces and contain the "exhaust" you can use a second smaller cell to reverse the process and potentially extend your distance or allow you to "Recharge" in the sun in the event you have to stop at an airfield without hydrogen service. Capaciter banks can also be used to increase power for take off and climb and allow a smaller power cell for continuous power.