
Australia's first electric aircraft has begun test flights - prostoalex
http://www.abc.net.au/news/2018-01-04/first-electric-plane-passenger-flights-in-australia-to-rottnest/9304424
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magicbuzz
Article gives you the idea that it would be taking pax to Rottnest Island (a
popular tourist destination) but it's only registered as a 'recreational' so
the only ppl going to Rottnest would be pilots themselves or a non-paying pax.

Payload is 200kg so that is basically two people and one suitcase.

30 minutes reserve might be enough for short hops but I've just finished
reading various articles written over the years by Richard Collins (who writes
a lot about safety) and he states that he _always_ had a hard rule of a one
hour reserve.

Still, the operating costs are crazy cheap. If they made a plane that had 3
hours range (2 hrs flying, 1 hr reserve) at 100+ knots with more payload, I'd
be interested.

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bobsil1
Tesla is driving (heh) battery energy density up.

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dogma1138
Not really, also while Tesla does work on batteries it’s more Panasonic which
makes he batteries for Tesla, LG chem and the likes that actually work on
that.

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bobsil1
Tesla drives down cost via scale, it is driving energy density for downstream
segments: EVs, drones, e-planes, et al.

~~~
dogma1138
It doesn’t work like that there are more “denser” batteries than what Tesla
uses, their density isn’t that impressive while they benefit from it its not
something they are driving.

P.S. Drones use LiPo batteries.

~~~
bobsil1
They're driving down mass-market LiIon specific energy cost ($ per Wh/kg) via
Gigafactory. No?

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dogma1138
They are reducing the cost of Wh/Kg maybe but they are not necessarily
increasing the Wh/Kg ratio Tesla isn’t pushing for super high density.

The cost isn’t the issue here it’s the weight a Tesla battery pack is heavy as
fuck and Tesla really hasn’t worked that much on reducing its actual weight
because there are easier paths to make a car lighter.

Drones use LiPos because at these scales LiIon isn’t viable.

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badosu
I wonder if there'd be an increase or loss of carbon footprint compared to
gas, when most of electricity produced in Australia is from coal?

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jfoucher
Coal power plants are roughly as efficient as an internal combustion engine
(around 40%) and considering the power transmission losses, charging losses,
electric engine inefficiencies and so on, any electric vehicle has worse
overall efficiency than the equivalent gas vehicle. Electric vehicles only
make sense from a pollution reduction point of view if the power is generated
from renewable sources.

~~~
pkolaczk
Typical coal power plants have practical electric efficiency 40% but total
energy efficiency is 60-70%, because they produce electricity and _useful
heat_.

Also 40% is a theoretical (lab) value for a non turbocharged diesel engine -
in practice most engines are operated out of their optimal range, they are
turbocharged (a turbo increases power output at the cost of decreasing
compression ratio and thermal efficiency), there are losses in the
transmission, hence efficiency is much lower than 40%.

BTW, in lab, a coal plant with a steam turbine can achieve over 50% electric
efficiency (some reports say even 60% is possible). They are too expensive to
be used on large scale, though.

~~~
seanmcdirmid
How is the useful heat used? I know some places have central heating, so the
hot water is just piped throughout the city, but if not that, what would they
do with it?

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alextheparrot
The term that the original poster didn’t include is “Cogeneration” [0].
Another use case would be desalination in areas without an adequate supply of
freshwater.

[0]
[https://en.m.wikipedia.org/wiki/Cogeneration](https://en.m.wikipedia.org/wiki/Cogeneration)

~~~
seanmcdirmid
Ya, I get that, it just doesn’t seem to be always the case that you’d find
something to do with the heat, especially given proximity of the coal plant to
places that could use it. It wouldn’t seem to work well for Australia, at
first glance (no serious heating needs, no desalination plants).

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pepijndevos
Funny remark about it being silent. In the text they mention that it's silent
when it's gliding. Well, duh... in the video they say it's just silent.

If you look up a video on youtube, you'll hear that the propeller still cause
a lot of noise. So it's only more silent from the ground.

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totalZero
I look forward to the day when solar panels are efficient enough that an
aircraft can appreciably recharge its batteries while gliding.

~~~
chrismorgan
I looked for a figure and found this suggestion for sunny days: 800W/m².

If the plane uses 20kW while flying, this would mean you’d need 25m² of 100%
efficiency solar panels to fly without draining the battery.

10.5m wing span, depth uncertain but looks to be under a metre, and we’re not
even halfway there. The fuselage isn’t suitable for a solar array. The tail,
maybe a bit.

Verdict: ignoring solar panel mass and fragility, you could probably already
design something that would get you another five minutes during your hour of
powered flight time, but I think you’d have to change things up a lot to
increase it much beyond that.

I think if you were trying to do such a thing seriously, you’d try to increase
wing and body top surface area.

Note that the plane can regenerate 2–5kW while gliding, making the propeller
act as a windmill. (Source: [https://www.avweb.com/videos/Video-Pipistrel-
Alpha-Electro-A...](https://www.avweb.com/videos/Video-Pipistrel-Alpha-
Electro-Aero-2015-223855-1.html), [https://www.avweb.com/videos/Video-Flying-
Pipistrels-Electri...](https://www.avweb.com/videos/Video-Flying-Pipistrels-
Electric-Airplane-224345-1.html). Other interesting details in those too.)

~~~
totalZero
Some numbers from the conventional-engine version: [http://pipistrel-
usa.com/models/alpha-trainer-tech.html](http://pipistrel-usa.com/models/alpha-
trainer-tech.html)

The wing area for this aircraft is 9.29m^2, and the glide ratio is 17:1 at
74mph. Let's say you fly for an hour and then glide through a descent of
12,000 feet (ceiling is 18,000 at max weight). That gives you about 90 minutes
of solar absorption time.

Assume we only fly at noon on clear sunny days to get 1kW/m^2 of solar energy
(nice round number). That's 13.9kWh of incident energy on the wings. If we can
capture that at 25% efficiency -- today's best commercial cells are around
here, although about twice the efficiency has been achieved by researchers --
it's 10.5 minutes of additional powered flight, or about 3 minutes of climb.
(I think that 3 minutes of climb yields an added 3660 ft of altitude or 11
minutes of glide.)

4kW from propeller generation during the glide phase yields another 6 minutes
of powered flight.

I agree with your conclusion for this particular aircraft's geometry; it's not
enough to sustain flight indefinitely. Still, other solar aircraft have
demonstrated that sustained solar flight of manned aircraft is possible, and
one such aircraft, Solar Impulse 2, has even circumnavigated the globe (albeit
interrupted by a few stops along the way).

~~~
chrismorgan
That all sounds about right, except for the generation part (see below) which
is but a minor factor anyway.

Indefinite solar-powered flight is understandably not a goal of Pipistrel for
this craft; it will be interesting once it gets to the point where it’s a more
commercially feasible design goal.

I love how you rounded up to 1kW/m² to get a nice round number, then
multiplied by 13.9!

It’s worth noting on the propeller generation point that it’s going to be more
efficient not to use it if you’re trying to maximise range: it will diminish
your glide ratio; it’s mostly for when you actively want to go _down_ , and
might as well retrieve and store most of the lost kinetic energy. If the
Trainer gets 17:1, I’d expect the Electro would get roughly that 17:1 if
merely idling, but lower if regenerating; I don’t care to speculate on the
numbers—I’m not a pilot or an electric car expert and it’ll take me too long
to calculate the actual energy rates involved. But physics more or less
decrees that it can’t regenerate more power than it will take to regain the
additional lost altitude. (I say only “more or less” because of things like
gravity assist manoeuvres, which are fascinating but not applicable to craft
like this.)

I was rather sloppy in the way I brought the regeneration up in my earlier
comment. It was true, but not relevant because of this last paragraph. I
didn’t think it through when I mentioned it at first.

~~~
totalZero
Agreed. It is probably too generous to assume the ideal glide ratio and
simultaneously assume generation via the prop.

Depends on a lot of stuff though. It's not a question of energy creation --
the energy of the system includes energy in the air. Generally freewheeling
generates more drag than a stationary propeller (google "ESC brake vs
freewheel" to see what R/C hobbyists have to say about this). However, you may
have an unusual situation where maintaining the ideal glide velocity requires
braking, and in such a case it is presumably more efficient to brake via the
propeller.

Suffice it to say that even in the ideal case, this particular aircraft would
have trouble maintaining flight via solar power, but other aircraft are
proving that this is a viable possibility.

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TillE
Are there denser ways to store electrical energy? Hydrogen fuel cells maybe?

Seems like you need something much lighter than lithium-ion batteries to even
begin to fill the role of passenger planes.

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kevincox
Hydrogen fuel cells would also make refuelling much faster. In the video they
claimed an hour recharge time for the small plane. While you can get more
parallelism as you add more batteries it still seems like making it much
faster would be beneficial.

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labcomputer
Probably not as much as you'd think, though.

Cars powered by compressed natural gas take longer to fill than gasoline-
powered ones[1]. I can't find it right now, but Edmunds did a long-term test
of a natural gas Honda Civic. One of the persistent complaints was long fill
times at public high-pressure stations. Natural gas has about 4x the energy
density of Hydrogen, so the problem becomes even worse.

~~~
seanmcdirmid
Ya, that explains the huge lineups to fill up natural gas vehicles in
Thailand. They have plenty of gas, but the infrastructure needed to distribute
it is tricky.

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Aardwolf
"Australia's first electric passenger plane takes to the skies"

Well, one passenger, more like a sports plane than an airliner. Still very
awesome :D

~~~
scoggs
Very cool, right? I had a brain fart when I read the title on the front page
thinking it was a self-driving electric plane, for some odd reason, and my
heart skipped a beat.

>It costs about $3 an hour to run the plane's engine, one-tenth the cost of a
fuel engine.

This sounds really great and at only €65,000 ($78196.30USD) it sounds like a
steal that will scale nicely once it can carry the 5+ passengers it intends
to. Someone in the comments mentioned it also sounds like a great idea because
there will be many less moving parts. The plane also switches to more of a
glider-mode once I imagine it's at altitude. A silent ride sounds kind of
peaceful when I think of the drone of a normal plane.

~~~
chrismorgan
Where’s the €65,000 number coming from? I found
[http://www.flypipistrel.com/price-lists/PIPISTREL-ALPHA-
ELEC...](http://www.flypipistrel.com/price-lists/PIPISTREL-ALPHA-
ELECTRO-12-2017.pdf) which suggests €159,000.

That datasheet also says 700 cycles to 75% battery capacity, rather than the
“about 1,000” of this article.

The $3/hour figure doesn’t seem to me to match the other numbers, either: 60kW
for takeoff and 20kW for cruising; let’s ignore takeoff (it’s rounding error)
and just call it 20kW. 20kWh for $3? At residential rates, 20kWh will cost
more like $5. But I don’t know what commercial rates are for electricity;
maybe they do get power that much cheaper than residential persons.

~~~
goodcanadian
Price of electricity varies greatly depending on where you are. My residential
rate is about $0.13/kWh, so completely consistent with the article.

~~~
chrismorgan
Interesting. I was going off my experience in Victoria, combined with quick
searching for Perth which showed about the same rates, then subtracting the
appropriate N% for paying on time (a pricing model that I wish was
illegal—expressing it as penalties for overdue payments would make life much
easier) which generally gets it down to 20–25¢/kWh. 13¢/kWh is _much_ lower
than I’ve ever seen in Australia, not that I’ve looked all over the country.

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kylehotchkiss
This is really exciting. I wonder if batteries will ever be able to power a 50
passenger aircraft, without having to extend the wings out too much to fit
more batteries/lift for the extra weight.

I can't see the 15 hour, 400 passenger flight planes going with batteries in
our lifetimes but it's cool to see things starting to go that way.

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Shivetya
An interesting idea, my question is how high can you fly before temperatures
lower the efficiency of the batteries? Let us assume a pressurized battery
compartment to eliminate the air pressure issues, anyone familiar with the
energy costs to keep cargo areas relatively stable? That might be equivalent
for a battery compartment.

~~~
mveety
Well on pressurized aircraft the cargo areas are generally inside the pressure
vessel so temperatures will be similar to the passenger areas. Also the
batteries will be producing heat when in use, so I would imagine cooling would
be a bigger issue, especially when the plane is baking in the sun at the
airport for the whole day in the summer.

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aphextron
The plane is a Pipistrel Alpha Electro [0]. Designed and built entirely in
Slovenia. Kind of a weird/misleading article as it presents the plane as
Australian.

[0] [http://www.pipistrel.si/plane/alpha-
electro/overview](http://www.pipistrel.si/plane/alpha-electro/overview)

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mey
Additionally I'm not sure I would call a 2 seater, a "passenger plane".

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taneq
Then what would you call the person in the second seat, who isn't flying the
plane?

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aphextron
>Then what would you call the person in the second seat, who isn't flying the
plane?

Instructor. These are designed pretty much exclusively as LSA trainers.

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daurnimator
Touring motor gliders are often sold to couples that want to travel together.
I've known people who own/fly: Dimona H36 and Taifun 17E. I have a family
member who recently purchased a TL Sting S4 (a microlight) for similar
purposes.

~~~
dreamcompiler
Not this one. Pipistrel brings their planes to EAA Oshkosh every year and
their internal combustion planes are marketed as touring motor gliders. But
the electric Alpha Electro is just touted as a training plane because its
range is so short.

~~~
mveety
I don't see how practical it is as a trainer though. At least when I was
learning, those planes wouldn't get much if any downtime. You will still need
more time to charge than it does to just throw some avgas in the plane. Also
it would be impossible to do some parts of your flight training in this plane
because of its tiny endurance.

