Australia's first electric aircraft has begun test flights | Hacker News Reader

Australia's first electric aircraft has begun test flights

abc.net.au

105 pointsprostoalex74 comments

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.

Tesla is driving (heh) battery energy density up.

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.

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

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.

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

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.

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?

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.

Second this. This is a common misconception a lot of consumers do not know.

You would find it very hard, if not impossible, to run an ICE car at 40% efficient for normal driving. The same can not be said for a coal plant. So if the coal plant averages 35% and the ICE car averages 25%, that leaves some room for a coal-driven electric car to be more efficient. The conversion from grid power to mechanical power only needs to be over 70% efficient. If anything, that sounds easy to beat. Any counters?

I we say all three of: charging, motor controller and motor are about 90% efficient, that's already 72% efficiency from grid power to mechanical. So maybe not that easy.

While a 90% efficient motor is quite good, a 90% controller and a 90% charger is not. I would expect them to be closer to 95%. But I have to back down from easy, according to [1], some Tesla owners charge their vehicles at 80% efficiency and not the ideal 92-98%. I imagined that would be a problem at those energy levels, apparently not! Anyhow, there is nothing inherently worse about fueling a central ICE to pump out electricity to EVs than directly fueling an ICE car. Larger ICEs tend to be more efficient, especially so for diesels. If you add the savings by the regenerative charging enabled by electric motors, it becomes even more favorable to electrify cars. We need a lot of batteries though!

[1] https://forums.tesla.com/forum/forums/charging-efficiency-0

What about refinement costs to turn oil into gasoline in the first place? That takes energy as well, and creates pollution. So we have a loss before we even get to the ICE.

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.

Very interesting information. Thank you.

What would you say is the typical efficiency of a modern gasoline car? Say, one that uses 7L/100km on average?

Also, why do the coal plants with higher efficiency so expensive? I've read somewhere that higher heat would be better, but the steel that can resist it, is too expensive. Is that correct?

I'm not am expert on turbines, but generally the turbine efficiency is directly related to the temperature and pressure difference between the inlet and outlet. Hence bigger plants have typically higher efficiencies. Bigger turbines have also more stages, so not only they have to withstand higher pressure, but simply there are more parts.

Hybrid cars let you operate IC engines at fairly high efficiency depending on setups but you now have to deal the overhead of charging batteries for both setups.

Also, if you want total efficiency in terms of C02 then you need to consider. Gasoline takes a lot of energy to extract, refine into a usable state, and transfer around the world. On the other hand hydrocarbons extract energy from hydrogen bonds not just carbon bonds so they produce less C02 per BTU.

Net result electric cars backed by coal power still win vs IC, but not by as much as you might think.

PS: You can also use turbines in hybrid car which would boost it's efficiency even more. But, you can also produce very cheap solar power which once again shifts things back to electricity.

Are you sure about your statement on turbos reducing efficiency? Some of the most economical consumer engines are turbocharged--in fact auto makers commonly cite mpgs as a reason to use turbos; so I am confused.

Yes. Turbocharging increases mpg not by increasing thermal efficiency, but by allowing to use a smaller and lighter engine. A lighter engine means less mass to accelerate, therefore less energy to spend. A smaller engine means less internal friction so less energy lost. However this theory works well if you actually don't use the full power that turbo gives you, or you use it only occasionally. These engines have great advantage in lab mpg tests, but in real dynamic driving the advantage diminishes. The main problem is that by adding a turbo, you need to decrease the compression ratio of the engine, which decreases thermal efficiency. Another thing is that turbo needs some energy to be powered, and also has some of its own energy losses. This is not free.

The new Honda Civic comes in a 1.5 turbo and a 2.0 NA, the turbo being the heavier package--but which still delivers higher mpgs. And if the turbo has more efficiency due to less internal friction, that still creates more useful energy out of the same amount of fuel, no?

You are right, but now we are not discussing thermal efficiency, but total mpg which is related, but not the same thing. Efficiency being equal, you'll get more mileage from an electric car, because it can get back some energy from regenerative breaking, and it definitely has less internal friction.

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?

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

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).

What's the power transmission loss from carrying crude to a refinery and then to Australia? The country is a net importer of oil, which means tankers burning foul stuff to carry it there.

Very true. Considering the whole supply chain for accurate comparison is complicated. Although I think my main point still stands : from an environmental perspective it's rather ineffective to have an electric car in a place where electricity comes from fossil fuels.

I think you're overstating the current situation and also leaving out the fourth dimension. If the grid gets cleaner over the useful life of the EV then it benefits from that. I believe basically all grids are projected to get vleaner over the next decade.

While electric cars might be worse for the environment, they're probably much better for people, because the pollution generation can be moved well away from dense urban areas. I imagine most people don't even remember what a city without gasoline pollution, like, smells like.

I imagine it will be similar to those before-after photos of cleaning smoker's apartments.

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.

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

Does anyone know what the upper bound is on solar recharge rate vs energy needed to fly for a reasonably heavy aircraft?

That would be amazing. Flying above the clouds with unobstructed sun hitting the panels you would imagine should be possible one day.

Could they do that if solar panels were 100% efficient?

On this aircraft, no. On other aircraft, it has been done without 100% efficiency.

https://en.wikipedia.org/wiki/Solar_Impulse#2015–16_circumna...

^ About 118 hours of manned flight between Japan and Hawaii.

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-Flying-Pipistrels-Electri.... Other interesting details in those too.)

Some numbers from the conventional-engine version: 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).

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.

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.

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.

Here are some comments from Musk regarding electric aircraft: https://www.youtube.com/watch?v=yx3auTD85Fw

"I'd love to do it... but I think my mind would explode."

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.

It seems like battery swapping would be a viable alternative here. The packs are only ~17kWh

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.

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.

Hydrogen fuel cells would solve another problem and that is when you expand the hydrogen you reduce the weight of the aircraft.

The problem with batteries is that a full battery and a discharged one weigh the same.

The tricky part with hydrogen is the containment. You either need cryogenically cooled tanks to get it to a liquid state, or metal hydrides to store it chemically. Both have fairly poor energy density (by volume and mass). What's more, the fuels cells aren't cheap either, and some of the more efficient ones operate at very high temperatures.

For all it's faults hydrocarbon fuels are really good at storing energy that's easily extractable.

Hydrogen creation using electrolysis is really inefficient. Somewhere under 50%.

"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

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.

Where’s the €65,000 number coming from? I found http://www.flypipistrel.com/price-lists/PIPISTREL-ALPHA-ELEC... 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.

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

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.

Further to the running costs: if replacing battery cells worn out by 700 one-hour-flight cycles costs €12,000 (again citing http://www.flypipistrel.com/price-lists/PIPISTREL-ALPHA-ELEC...), that’s €17.14/hour, which is over AU$26.

So if you consider that to be a “fuel cost” (seems reasonable to me), then your “$3 an hour to run the plane's engine” has multiplied by ten—so much for “one-tenth the cost of a fuel engine”! (Yes, to make the comparison fair we need to factor engine maintenance costs into it, which can reasonably be expected to fall in the electric motor’s favour, but I don’t care to speculate how it may balance out this matter of the battery cost.)

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.

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.

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.

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

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

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

A weight distributor.

ballast

Self-loading freight.

>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.

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.

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.

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.

someone to talk to

speaking weight

Hypoxia redundancy system.

This is local news so what they mean is that this is the first plane in the country with those characteristics. The internet makes local news sites global and it probably never even crossed their minds that someone not local would naturally make that interpretation from the headline.

What about "First electric passenger plane takes to the skies in Australia"?

That's better, except someone would then complain that "first" implies that it's the world's first and happens to be in Australia. We used your suggestion but reordered the phrases above.

Edit: actually, I think we can get around all this by just using the first sentence of the article.

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