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Australia's first electric aircraft has begun test flights

abc.net.au

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Re: Australia's first electric aircraft has begun test flights

#21

Post by pkolaczk »

jfoucher wrote: post #14
badosu wrote: post #4

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.

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.

Re: Australia's first electric aircraft has begun test flights

#22

Post by icebraining »

jfoucher wrote: post #14
badosu wrote: post #4

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.

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.

Re: Australia's first electric aircraft has begun test flights

#23

Post by FrojoS »

pkolaczk wrote: post #21
jfoucher wrote: post #14

Earlier quoted context omitted.

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.

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),…

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?

Re: Australia's first electric aircraft has begun test flights

#24

Post by pkolaczk »

FrojoS wrote: post #23
pkolaczk wrote: post #21

Earlier quoted context omitted.

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),…

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.

Re: Australia's first electric aircraft has begun test flights

#26

Post by speeq »

TillE wrote: post #25

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

Re: Australia's first electric aircraft has begun test flights

#27

Post by kevincox »

TillE wrote: post #25

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.

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.

Re: Australia's first electric aircraft has begun test flights

#28

Post by pedrocr »

aphextron wrote: post #2

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

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.

Re: Australia's first electric aircraft has begun test flights

#29

Post by gus_massa »

pedrocr wrote: post #28
aphextron wrote: post #2

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

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"?

Re: Australia's first electric aircraft has begun test flights

#30

Post by Retric »

pkolaczk wrote: post #21
jfoucher wrote: post #14

Earlier quoted context omitted.

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.

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),…

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.

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