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RegGuheert
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Eviation Battery-Electric Commuter Aircraft

Tue Feb 27, 2018 2:27 pm

Eviation Aircraft website

InsideEVs has an article about Eviation, which is working to build a battery-electric commuter plane:
InsideEVs wrote:The company first showed the mock-up at the 2017 Paris Air Show and was present at the recent Singapore Airshow with a promise of first flights this year. Commercialization is to begin in 2019.

Eviation recently signed a deal worth over $1 million with South Korean battery manufacturer Kokam to provide 900 kWh battery packs, required for the range of the craft.. Batteries are to be highly energy dense at 260 Wh/kg.

Specifications (as of February 27, 2018):

- Seats: 9 passengers plus 2 crew members
- Cabin: Unpressurized
- Service ceiling: 12,000 ft.
- Cruise altitude: 10,000 ft.
- Cruise speed: 240 knots
- Range + IFR reserve: 650 miles
- VNE: 289 knots
- Approach speed: 100 knots
- Energy pack: 900 kWh Li-ion
- Length: 12.2 m
- Wingspan: 16.12 m
- MTOW: 6350 kg
- Propulsion: 3 X pusher propeller (one at tail and one on each wingtip)
- Powerplants: 3 X 260 kW

Here is a video (which appears to be an advertisement for 3D printing):



For reference, here is a link to the 27-Ah Kokam NMC cell which is likely what is being used in the battery.

Edit 2018-02-28: Added link to Kokam Batteries NMC cell.
Last edited by RegGuheert on Wed Feb 28, 2018 1:16 pm, edited 1 time in total.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

LeftieBiker
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Re: Eviation Battery-Electric Commuter Aircraft

Tue Feb 27, 2018 2:47 pm

You'd think that pasenger planes would be a perfect platform for serial hybrids. The ICE(s) could provide extra power for takeoff and climbing, and then either throttle way back or shut down as needed in flight. 90% less noise, and if the batteries are charged on the ground, 90% less fuel used.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

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RegGuheert
Posts: 6332
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Re: Eviation Battery-Electric Commuter Aircraft

Tue Feb 27, 2018 3:09 pm

I have to say that this looks like an interesting start, but there are three specifications which will greatly limit the application of this plane for commercial travel:

1) Range of only 650 miles (including the reserve).
2) Cruise speed of only 240 knots. A slow airspeeds greatly reduces the range when flying into a strong headwind.
3) Only nine passengers. Nine passengers to pay for all airplane expenses and two crew members means the seats will be very expensive.

That said, I think it is pretty cool that this is being developed. If they execute and catch the wave of battery technology at the right point, the capabilities of battery-electric commercial aircraft could improve rather quickly.

For reference, I will note that the Boeing 737 had nearly three times the range, about twice the airspeed and could carry around 13 times as many passengers when it was introduced in 1967.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

GRA
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Location: East side of San Francisco Bay

Re: Eviation Battery-Electric Commuter Aircraft

Tue Feb 27, 2018 5:22 pm

RegGuheert wrote:I have to say that this looks like an interesting start, but there are three specifications which will greatly limit the application of this plane for commercial travel:

1) Range of only 650 miles (including the reserve).

Not an issue for a commuter a/c, as legs are typically under 400 miles for even a twin turboprop regional airliner, and this is a lot smaller than that.

RegGuheert wrote:2) Cruise speed of only 240 knots. A slow airspeeds greatly reduces the range when flying into a strong headwind.

Less of an issue as above, and any speed disadvantage may be reduced or eliminated depending on climb speed and maneuverability.

RegGuheert wrote:3) Only nine passengers. Nine passengers to pay for all airplane expenses and two crew members means the seats will be very expensive.

Not uncommon for a small commuter, but yeah, 19 seats (you need a flight attendant for 20+ pax) would have lower seat-mile costs.
This would seem to be aimed at a similar market to say a Queen Air, falling somewhere between a Caravan and a Malibu in capability, but with multiple 'engines'.

RegGuheert wrote:That said, I think it is pretty cool that this is being developed. If they execute and catch the wave of battery technology at the right point, the capabilities of battery-electric commercial aircraft could improve rather quickly.

For reference, I will note that the Boeing 737 had nearly three times the range, about twice the airspeed and could carry around 13 times as many passengers when it was introduced in 1967.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

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RegGuheert
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Re: Eviation Battery-Electric Commuter Aircraft

Tue Feb 27, 2018 5:49 pm

GRA wrote:
RegGuheert wrote:I have to say that this looks like an interesting start, but there are three specifications which will greatly limit the application of this plane for commercial travel:

1) Range of only 650 miles (including the reserve).

Not an issue for a commuter a/c, as legs are typically under 400 miles for even a twin turboprop regional airliner, and this is a lot smaller than that.
Who are you and what have you done with GRA? :)

So you think there will be no problem to fly 400 miles in 0 F (or lower) weather flying into 100 MPH headwinds (do wind speeds get that high at 10,000 feet?)? In other words, all the things that affect BEVs on the ground are worse in the air: the wind speeds are higher and the temperatures are colder, plus you have to provide for de-icing. And in commercial service, you can't just tell your passengers you are going to go without heat.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

GRA
Posts: 9510
Joined: Mon Sep 19, 2011 1:49 pm
Location: East side of San Francisco Bay

Re: Eviation Battery-Electric Commuter Aircraft

Tue Feb 27, 2018 6:07 pm

RegGuheert wrote:
GRA wrote:
RegGuheert wrote:I have to say that this looks like an interesting start, but there are three specifications which will greatly limit the application of this plane for commercial travel:

1) Range of only 650 miles (including the reserve).

Not an issue for a commuter a/c, as legs are typically under 400 miles for even a twin turboprop regional airliner, and this is a lot smaller than that.
Who are you and what have you done with GRA? :)

So you think there will be no problem to fly 400 miles in 0 F (or lower) weather flying into 100 MPH headwinds (do wind speeds get that high at 10,000 feet?)? In other words, all the things that affect BEVs on the ground are worse in the air: the wind speeds are higher and the temperatures are colder, plus you have to provide for de-icing. And in commercial service, you can't just tell your passengers you are going to go without heat.

I expect an a/c like this will fly legs of 250 miles or (much) less, which is typical for that speed range/size, so 650 miles max. is plenty. Beyond that, faster cruise speeds, higher cruise altitudes which require cabin pressurization, and greater capacity are the norm.

Winds can hit 100+ knots in the vicinity of ground chokepoints (for many years, the 6,288' summit of Mt. Washington in New Hampshire held the record for highest ground windspeed recorded at 231 mph (200 knots) in 1934), but outside of a hurricane I doubt they'd ever see anything like that in unobstructed air; they're well below the jet stream. Think more like Milwaukee to Grand Rapids across Lake Michigan, or at most Chicago to Detroit for these a/c. BTW, IFR reserve is fuel to designated divert airfield plus 45 minutes holding.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

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RegGuheert
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Re: Eviation Battery-Electric Commuter Aircraft

Wed Feb 28, 2018 1:06 pm

I missed a couple of interesting things about the battery system yesterday:
Eviation wrote:Ultra-light design

Our battery takes up 65% of the aircraft’s weight, and it takes a state-of-the-art all composite body, to makeup for that.
Eviation wrote:High energy density battery system

Combining Lithium-ion for high power needs and a proprietary Aluminum-Air system for range, hitting the 400Wh/kg mark and more.
That second part is the really interesting part. So the 900 kWh Li-ion battery is only part of an overall battery system that apparently achieves a specific energy of 400 Wh/kg. The other part is a metal-air system based on aluminum. It will be interesting to learn the specifics about that. part.

So let's do some math to try to determine the mass and specific energy of this Li-ion battery.

Assumptions:
- The "battery takes up 65% of the aircraft’s weight" is referring to empty weight, not MTOW which is what is given.
- Each passenger and crew member with bags has a weight of 100 kg.
- The specific energy of the 900 kWh battery pack is 200 Wh/kg.

Calculations:
- OEW (Operating Empty Weight) = MTOW - (Number of passengers and crew) * (weight of passengers and crew) = 6350 kg - 11 * 100 kg = 5250 kg
- Battery Overall Weight = 0.65 * OEW = 0.65 * 5250 kg = 3400 kg
- Weight of Li-ion battery = 900 kWh * 1000 Wh/kWh / 200 Wh/kg = 4500 kg (!)

Full stop. According to my calculations, the mass of the Li-ion battery by itself is already 71% of the MTOW. In other words, their numbers do not add up even if I try to use MTOW instead of OEW. There is no weight left over to add a metal-air battery. In fact, there is barely is any weight left over to add anything. If the passengers and their bags sat directly on the battery with nothing else, we would only be 750 kg below MTOW. It seems clear at this point that the MTOW will be significantly higher than what is listed here, perhaps close to double.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

User avatar
RegGuheert
Posts: 6332
Joined: Mon Mar 19, 2012 4:12 am
Delivery Date: 16 Mar 2012
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Location: Northern VA

Re: Eviation Battery-Electric Commuter Aircraft

Wed Feb 28, 2018 1:48 pm

According to a comment on the InsideEVs article, the metal-air battery is being provided by Phinergy. According to their website, aluminum has a specific energy of 8 kWh/kg.

I'm wondering if that battery is being used only to provide the IFR reserve and will NOT be used in normal flying.

Assuming the metal-air battery is added to the 900-kWh, 200 Wh/kg Li-ion battery, let's calculate it's mass and capacity, assuming 8 kg/kWh:

(900 kWh + MetalAirCapacity kWh) * 1000 Wh/kWh / 400 Wh/kg = 900 kWh * 1000 Wh/kWh / 200 Wh/kg + MetalAirCapacity kWh * 1000 Wh/kWh / 8000 Wh/kg

(20 * MetalAirCapacity - MetalAirCapacity) kWh * 1000 Wh/kWh / 8000 Wh/kg = 2250 kg

19 * MetalAirCapacity kWh = 2250 kg * 8000 Wh/kg /1000 Wh/kWh = 18,000 kWh

MetalAirCapacity = 950 kWh

MetalAirMass = MetalAirCapacity * 8 kg/kWh = 118 kg

Since it will likely need more than just the aluminum, lets estimate the mass of the metal-air battery to be about 200 kg.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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