11 ms·

The big reason for this is thermodynamics. A conventional internal combustion engine car has to convert chemical energy to kinetic energy - the absolute best th

The big reason for this is thermodynamics. A conventional internal combustion engine car has to convert chemical energy to kinetic energy - the absolute best theoretical efficiency of this might be 70%, but in practice it's more like 30%. Electric cars have to pay the same thermodynamic penalty, but they pay it at the power station (In practice, thanks to renewables, not all the electricity used to charge a car will come from hydrocarbons - but let's assume it does for ease of comparison sakes). It's much easier to build highly efficient hydrocarbon power stations - typical efficiencies range from 40-60%. So when you look at the headline "efficiency" of an electric car, you need to take that thermodynamic penalty into account first. A modern series hybrid like a Toyota Prius is effectively an electric vehicle and a gas generator (which means it has the same efficiency gains due to regenerative braking). That gets 52 mpg, which is about 493 Wh/km. If you generated the 225 Wh the Tesla needs in even the most efficient combined cycle gas turbine powerplant you'd need 375 Wh. Less - but not nearly as drastic as it first seems. Renewables change the picture though - once you have significant renewable generation the carbon intensity of electricity starts dropping, which means that remote powerplant vs local powerplant argument falls apart. That is when the real power of electric vehicles kicks in - they can take their energy from anywhere.

antibasilisk 4y ago
>The big reason for this is thermodynamics. Yes it usually is
zamnos 4y ago
> the absolute best theoretical efficiency of this might be 70% I fell down a rabbit hole and found this link, which gives 46% for the theoretical limit for the efficiency of the internal combustion engine. https://physics.stackexchange.com/questions/98966/maximum-theoretical-efficiency-of-internal-combustion-engine https://physics.stackexchange.com/questions/98966/maximum-th...
- rkangel 4y ago
  It's a different metric but it is generally accepted that F1 cars have reached an overall thermal efficiency of 50%, which is cool. This is taking into account energy recovery from kinetic (regenerative braking) and thermal sources (from the turbo).
  - zamnos 4y ago
    KERS is neat and all, but factoring that into ICE engine efficiency seems a bit like cheating, since there's now also 2 MJ battery on board F1 cars.
- littlestymaar 4y ago
  note that this is true for spark ignition engines, but not all ICE, diesel engines can reach higher efficiency and there are even real diesel engines with almost 50% efficiency[1], obviously not in cars though. [1]: https://engineerine.com/meet-wartsila-31-worlds-most-efficient/ https://engineerine.com/meet-wartsila-31-worlds-most-efficie...
- osigurdson 4y ago
  Most power generation facilities are natural gas fired, using large aero derivitive gas turbine engines (essentially the same engine that is in the 747 - LM6000 vs CF6 for example) with a combined cycle steam turbine to capture the energy from excess heat. This arrangement has a thermodynamic efficiency of 60%. Even with electrical transmission losses, the efficiency is still far better (1.7X) than having the power plant located under the hood of the car.
  - zamnos 4y ago
    Not to mention, policing one large facility for compliance with emissions is much easier than trying to monitor every single one of millions of cars on the road.
    - Consultant32452 4y ago
      It's much easier to regulate millions of nobodies with no power than it is to regulate a single wealthy donor.
      - osigurdson 4y ago
        Even with a car, you aren’t necessarily regulating millions of individuals - primarily just manufacturers. I suppose there is the odd case where “old joe” removed his catalytic converter and is polluting more than others but that is probably rare. I don’t get your point on centralization however - more efficient but less robust (just like in software).
        osigurdson 4y ago
        Correction - I do get your point
        Consultant32452 4y ago
        For necessarily centralized industries like car manufacturing the regulations are written to protect the wealthy incumbents competition more than to protect consumers.
walrus01 4y ago
> A modern series hybrid like a Toyota Prius is effectively an electric vehicle and a gas generator (which means it has the same efficiency gains due to regenerative braking). That gets 52 mpg, which is about 493 Wh/km. Wait, does a new prius or something like a hyundai ioniq (also 52-53 mpg) not have the internal combustion engine mechanically coupled to the transmission and drive wheels anymore?
- masklinn 4y ago
  They do, but also don’t, the Prius and the Ioniq are series-parallel hybrid so the ICE plugs into a power splitter which can feed into both the mechanical transmission and a generator.
- rimliu 4y ago
  I've got Civic e:hev, which has kind of similar setup. ICE does drive wheels in some situations (high speed, much power required), but mostly is just EV. It does not even have a gearbox, so there is only direct coupling from ICE to the wheels that can be engaged or disengaged (this is done automatically, you have no manual control over this). I really like this setup, because it gives economy, but also a range and I don't need to worry about where to charge the car.
  - sidewndr46 4y ago
    Isn't Honda the dark horse of hybrids? I remember riding in one and the owner explained that apparently Honda chose a hybrid architecture that was different that everyone else. The car's transition from electric to ICE was quite noticeable.
    - kube-system 4y ago
      Honda has had two systems, the earlier “IMA” system which is a mild parallel hybrid. And the current “E-drive” system which is primarily a series hybrid. Series hybrids are actually pretty old tech — it’s how diesel locomotives works. The Chevy Volt also works just about the same way.
masklinn 4y ago
> the absolute best theoretical efficiency of this might be 70% While ICE are heat engines with a theoretical limit of 70%, they’re more specialised subsets described by the Otto (gas) and Diesel (… diesel) cycles, which have a much lower theoretical maximum. Just plugging the temperature ranges into Carnot will give you a Carnot limit of 50%, and using Otto will yield 46% (https://physics.stackexchange.com/a/98992 https://physics.stackexchange.com/a/98992). Add in that gas engines are not spherical and into a vacuum (losses and delays) and you’re in the 30s.
- qikInNdOutReply 4y ago
  Wrap the combustion engine with a heatpump to a small steam engine?
  - osigurdson 4y ago
    It isn't precisely "wrapped", but this is essentially how all natural gas fired generation facilities work. https://en.wikipedia.org/wiki/Combined_cycle_power_plant https://en.wikipedia.org/wiki/Combined_cycle_power_plant
    - greesil 4y ago
      I think the parent is referring to harvesting some of the waste heat
  - lilililililili 4y ago
    [dead]
  - Sohcahtoa82 4y ago
    The added weight and complexity would probably negate any benefit gained.
2OEH8eoCRo0 4y ago
ICE converts chemical energy to mechanical energy but an electric vehicle still has to convert electrical energy to mechanical energy.
- robnado 4y ago
  The battery converts from chemical energy to electrical energy and the motor of the vehicle converts from electrical to mechanical energy.
  - 2OEH8eoCRo0 4y ago
    Ah. My point was more that there are losses assocated with these conversions and you can't move all of it to the upstream power plant. ICE vehicles burn fuel and create rotational mechanical energy which other than gear reductions doesn't require conversion. Electric does chemical -> electrical and then electrical -> mechanical with losses at each step here right?
    - sidewndr46 4y ago
      Not entirely true, most transmissions have a system of torque converters and clutches. The torque converters convert rotational energy into fluid pressure to gain a kind of mechanical advantage. The clutches slip and make heat, usually to allow other parts of the transmission to interact without destroying gears. Once you get to cruising speed the transmission usually engages something called a "lockup" that bypass all that to get as close to the 100% number for energy transfer as possible.
    - nayuki 4y ago
      Note how almost every diesel locomotive has electrical generators and motors as an intermediate step because they decided that it's cheaper, more efficient, and/or lighter than having a huge gearbox. Electrification has some real advantages. https://en.wikipedia.org/wiki/Diesel_locomotive https://en.wikipedia.org/wiki/Diesel_locomotive , https://en.wikipedia.org/wiki/Diesel%E2%80%93electric_powertrain https://en.wikipedia.org/wiki/Diesel%E2%80%93electric_powert...
sgt 4y ago
Though that makes me think that hybrids have a real future. Or hydrogen fuel cells. Anything that doesn't require charging directly from the grid all the time, because although parts of the USA and Norway are ready for that, it's very tricky to get right globally. Maybe hybrids like the Prius get to be so efficient that such cars will have a truly negligible impact on global warming.
- pjc50 4y ago
  Hybrids that emit carbon will still have a huge effect on global warming, simply because there are so many cars. There isn't a huge amount of headroom for efficiency increases, so you're only going to get anywhere near "net zero" by charging from a renewable grid nearly all the time.
  - R0flcopt3r 4y ago
    Hybrids almost never emit carbon though. Because they're almost always running from the battery that you charged up from the wall before leaving home for your daily commute. And the daily commute is less, or maybe a little over the battery range. If it isn't then you have bought the wrong car, if you goal is carbon neutrality. You can use a smaller battery, which means using less rare materials that are very expensive. There are a lot of indirect emissions with electric vehicles, and it's important to look at the big picture.
    - leoedin 4y ago
      That's only true of plug-in hybrids. "Hybrid" just means a car with an electric and ICE drive train. Most hybrids aren't plug-in hybrids. They have no ability to charge their battery except from the engine.
      - adgjlsfhk1 4y ago
        right but that's easy to change.
    - XorNot 4y ago
svnt 4y ago
It is a sign of the success of the oil industry that this analysis always takes the cost of electricity generation back to the source, but assumes that fuel stations pump from a perfect source of naturally refined/distilled hydrocarbons. It is surprisingly difficult to get numbers on how much oil is used to extract, refine and transport oil. The best I found was this: https://www.speakev.com/threads/energy-required-to-refine-oil-to-petrol-diesel-and-by-products.13726/ https://www.speakev.com/threads/energy-required-to-refine-oi... Does anyone have better numbers?
- semi-extrinsic 4y ago
  I know Equinor publishes quite detailed numbers from their operations: https://sustainability.equinor.com/climate-tables https://sustainability.equinor.com/climate-tables The headline figure is maybe to compare 11.4 mill. tonnes CO2e emissions from "Scope 1 + Scope 2" (direct emissions from the company plus indirect emissions because they buy electricity and stuff), versus 243 mill. tonnes CO2e from Scope 3 (emissions from people burning the hydrocarbons sold). If that figure is correct, you can add 1.6 percent to the car tailpipe emissions figures to account for production and refining etc. But this is an oil & gas company that tries very hard and is among the best in the world for minimising emissions from production and refining. I would not be surprised if gasoline from US shale oil is more than an order of magnitude worse.
  - thfuran 4y ago
    >EROI values for our most important fuels, liquid and gaseous petroleum, tend to be relatively high. World oil and gas has a mean EROI of about 20:1 (n of 36 from 4 publications) (Fig. 2) (see Lambert et al., 2012 and Dale, 2010 for references). The EROI for the production of oil and gas globally by publicly traded companies has declined from 30:1 in 1995 to about 18:1 in 2006 (Gagnon et al., 2009). The EROI for discovering oil and gas in the US has decreased from more than 1000:1 in 1919 to 5:1 in the 2010s, and for production from about 25:1 in the 1970s to approximately 10:1 in 2007 (Guilford et al., 2011). Alternatives to traditional fossil fuels such as tar sands and oil shale (Lambert et al., 2012) deliver a lower EROI, having a mean EROI of 4:1 (n of 4 from 4 publications) and 7:1 (n of 15 from 15 publication) https://www.sciencedirect.com/science/article/pii/S0301421513003856#bib11 https://www.sciencedirect.com/science/article/pii/S030142151...
jjtheblunt 4y ago
Does regenerative braking count as renewable energy? It's clearly absent from internal combustion (diesel or not)
- acidburnNSA 4y ago
  Lord I hope not. It helps with efficiency, but is no more renewable than carrying a rock upstairs and throwing it out a window onto some kind of generator.
heresie-dabord 4y ago
> the real power of electric vehicles Generation can be from clean sources and is already happening in some jurisdictions. Even if a clean source is not available, the pollution can best be controlled at the source. In this period of history, hundreds of millions of people make billions of polluting trips every day in their communities. Although owning any car is the poorest choice of all for the environment, there are two ecological benefits to driving a BEV or a PHEV. * better efficiency than ICE * zero emissions in the case of BEV, zero emissions *for most trips* in the case of PHEV
marcosdumay 4y ago
> A conventional internal combustion engine car has to convert chemical energy to kinetic energy - the absolute best theoretical efficiency of this might be 70% You mean thermal energy? Both cars are converting chemical energy to kinetic. The theoretical maximum for this is 100%. But one uses a thermal intermediate step, that reduces that maximum.
Twirrim 4y ago
One of the big sources of electricity generation here is hydroelectric, so I've been joking with my kids for a while that we have a water powered car. The first time I brought it up sparked a fun conversation as they wanted to understand how water makes electricity, and then started rabbit-holing on how magnets are involved in everything.
MuffinFlavored 4y ago
> Renewables change the picture though - once you have significant renewable generation the carbon intensity of electricity starts dropping, which means that remote powerplant vs local powerplant argument falls apart. That is when the real power of electric vehicles kicks in - they can take their energy from anywhere. How close/far would you say we are as a society on "having significant renewable generation"?
- philipkglass 4y ago
  I don't know where you live, but in the United States renewables have recently surpassed nuclear and coal power as sources of electricity: https://www.eia.gov/todayinenergy/detail.php?id=55960 https://www.eia.gov/todayinenergy/detail.php?id=55960 They're still pretty close to each other right now. Renewables are at 21%, coal 20%, nuclear 19%. However, nuclear is flat and coal is declining. Renewables are still growing rapidly and will widen their lead significantly in a few more years. See the first embedded chart in the article, showing output trends since 2010. Also see the short term forecast at the end of the article: "In our March Short-Term Energy Outlook, we forecast the wind share of the U.S. generation mix will increase from 11% last year to 12% this year. We forecast that the solar share will grow to 5% in 2023, up from 4% last year. The natural gas share of generation is forecast to remain unchanged from last year (39%); the coal share of generation is forecast to decline from 20% last year to 17% in 2023."
  - 0cf8612b2e1e 4y ago
    I was curious, and Wikipedia lists 224 active coal plants in the USA. More amazing was that from 2010 to 2020, 240 coal plants were closed. [0] https://en.m.wikipedia.org/wiki/List_of_coal-fired_power_stations_in_the_United_States https://en.m.wikipedia.org/wiki/List_of_coal-fired_power_sta...
snitty 4y ago
>It's much easier to build highly efficient hydrocarbon power stations - typical efficiencies range from 40-60%. Just to expound on this. Power stations turn fuel to heat, and heat to electricity via steam turbines. In ICE cars, that heat is the main loss of power. Whole systems in cars are built to get rid of that excess heat in the engine.
derethanhausen 4y ago
The Prius' efficiency comes from much much more than regenerative braking. Part is a focus on good aero and low weight, like many electric cars. But most is from leveraging the electric motors to allow the engine to run at max thermal efficiency (probably a touch above your 30% figure) at nearly all times. ICEs are most efficient under medium-low RPMs and high load. The electric motors can sustain low speed cruising, letting the engine shut off entirely if it wouldn't be well utilized, and also fill in for high torque demand to keep engine power output lower.

antibasilisk 4y ago

>The big reason for this is thermodynamics. Yes it usually is

zamnos 4y ago

> the absolute best theoretical efficiency of this might be 70% I fell down a rabbit hole and found this link, which gives 46% for the theoretical limit for the efficiency of the internal combustion engine. https://physics.stackexchange.com/questions/98966/maximum-theoretical-efficiency-of-internal-combustion-engine https://physics.stackexchange.com/questions/98966/maximum-th...

rkangel 4y ago
It's a different metric but it is generally accepted that F1 cars have reached an overall thermal efficiency of 50%, which is cool. This is taking into account energy recovery from kinetic (regenerative braking) and thermal sources (from the turbo).
- zamnos 4y ago
  KERS is neat and all, but factoring that into ICE engine efficiency seems a bit like cheating, since there's now also 2 MJ battery on board F1 cars.
littlestymaar 4y ago
note that this is true for spark ignition engines, but not all ICE, diesel engines can reach higher efficiency and there are even real diesel engines with almost 50% efficiency[1], obviously not in cars though. [1]: https://engineerine.com/meet-wartsila-31-worlds-most-efficient/ https://engineerine.com/meet-wartsila-31-worlds-most-efficie...
osigurdson 4y ago
Most power generation facilities are natural gas fired, using large aero derivitive gas turbine engines (essentially the same engine that is in the 747 - LM6000 vs CF6 for example) with a combined cycle steam turbine to capture the energy from excess heat. This arrangement has a thermodynamic efficiency of 60%. Even with electrical transmission losses, the efficiency is still far better (1.7X) than having the power plant located under the hood of the car.
- zamnos 4y ago
  Not to mention, policing one large facility for compliance with emissions is much easier than trying to monitor every single one of millions of cars on the road.
  - Consultant32452 4y ago
    It's much easier to regulate millions of nobodies with no power than it is to regulate a single wealthy donor.
    - osigurdson 4y ago
      Even with a car, you aren’t necessarily regulating millions of individuals - primarily just manufacturers. I suppose there is the odd case where “old joe” removed his catalytic converter and is polluting more than others but that is probably rare. I don’t get your point on centralization however - more efficient but less robust (just like in software).
      - osigurdson 4y ago
        Correction - I do get your point
        Consultant32452 4y ago
        For necessarily centralized industries like car manufacturing the regulations are written to protect the wealthy incumbents competition more than to protect consumers.

walrus01 4y ago

> A modern series hybrid like a Toyota Prius is effectively an electric vehicle and a gas generator (which means it has the same efficiency gains due to regenerative braking). That gets 52 mpg, which is about 493 Wh/km. Wait, does a new prius or something like a hyundai ioniq (also 52-53 mpg) not have the internal combustion engine mechanically coupled to the transmission and drive wheels anymore?

masklinn 4y ago
They do, but also don’t, the Prius and the Ioniq are series-parallel hybrid so the ICE plugs into a power splitter which can feed into both the mechanical transmission and a generator.
rimliu 4y ago
I've got Civic e:hev, which has kind of similar setup. ICE does drive wheels in some situations (high speed, much power required), but mostly is just EV. It does not even have a gearbox, so there is only direct coupling from ICE to the wheels that can be engaged or disengaged (this is done automatically, you have no manual control over this). I really like this setup, because it gives economy, but also a range and I don't need to worry about where to charge the car.
- sidewndr46 4y ago
  Isn't Honda the dark horse of hybrids? I remember riding in one and the owner explained that apparently Honda chose a hybrid architecture that was different that everyone else. The car's transition from electric to ICE was quite noticeable.
  - kube-system 4y ago
    Honda has had two systems, the earlier “IMA” system which is a mild parallel hybrid. And the current “E-drive” system which is primarily a series hybrid. Series hybrids are actually pretty old tech — it’s how diesel locomotives works. The Chevy Volt also works just about the same way.

masklinn 4y ago

> the absolute best theoretical efficiency of this might be 70% While ICE are heat engines with a theoretical limit of 70%, they’re more specialised subsets described by the Otto (gas) and Diesel (… diesel) cycles, which have a much lower theoretical maximum. Just plugging the temperature ranges into Carnot will give you a Carnot limit of 50%, and using Otto will yield 46% (https://physics.stackexchange.com/a/98992 https://physics.stackexchange.com/a/98992). Add in that gas engines are not spherical and into a vacuum (losses and delays) and you’re in the 30s.

qikInNdOutReply 4y ago
Wrap the combustion engine with a heatpump to a small steam engine?
- osigurdson 4y ago
  It isn't precisely "wrapped", but this is essentially how all natural gas fired generation facilities work. https://en.wikipedia.org/wiki/Combined_cycle_power_plant https://en.wikipedia.org/wiki/Combined_cycle_power_plant
  - greesil 4y ago
    I think the parent is referring to harvesting some of the waste heat
- lilililililili 4y ago
  [dead]
- Sohcahtoa82 4y ago
  The added weight and complexity would probably negate any benefit gained.

2OEH8eoCRo0 4y ago

ICE converts chemical energy to mechanical energy but an electric vehicle still has to convert electrical energy to mechanical energy.

robnado 4y ago
The battery converts from chemical energy to electrical energy and the motor of the vehicle converts from electrical to mechanical energy.
- 2OEH8eoCRo0 4y ago
  Ah. My point was more that there are losses assocated with these conversions and you can't move all of it to the upstream power plant. ICE vehicles burn fuel and create rotational mechanical energy which other than gear reductions doesn't require conversion. Electric does chemical -> electrical and then electrical -> mechanical with losses at each step here right?
  - sidewndr46 4y ago
    Not entirely true, most transmissions have a system of torque converters and clutches. The torque converters convert rotational energy into fluid pressure to gain a kind of mechanical advantage. The clutches slip and make heat, usually to allow other parts of the transmission to interact without destroying gears. Once you get to cruising speed the transmission usually engages something called a "lockup" that bypass all that to get as close to the 100% number for energy transfer as possible.
  - nayuki 4y ago
    Note how almost every diesel locomotive has electrical generators and motors as an intermediate step because they decided that it's cheaper, more efficient, and/or lighter than having a huge gearbox. Electrification has some real advantages. https://en.wikipedia.org/wiki/Diesel_locomotive https://en.wikipedia.org/wiki/Diesel_locomotive , https://en.wikipedia.org/wiki/Diesel%E2%80%93electric_powertrain https://en.wikipedia.org/wiki/Diesel%E2%80%93electric_powert...

sgt 4y ago

Though that makes me think that hybrids have a real future. Or hydrogen fuel cells. Anything that doesn't require charging directly from the grid all the time, because although parts of the USA and Norway are ready for that, it's very tricky to get right globally. Maybe hybrids like the Prius get to be so efficient that such cars will have a truly negligible impact on global warming.

pjc50 4y ago
Hybrids that emit carbon will still have a huge effect on global warming, simply because there are so many cars. There isn't a huge amount of headroom for efficiency increases, so you're only going to get anywhere near "net zero" by charging from a renewable grid nearly all the time.
- R0flcopt3r 4y ago
  Hybrids almost never emit carbon though. Because they're almost always running from the battery that you charged up from the wall before leaving home for your daily commute. And the daily commute is less, or maybe a little over the battery range. If it isn't then you have bought the wrong car, if you goal is carbon neutrality. You can use a smaller battery, which means using less rare materials that are very expensive. There are a lot of indirect emissions with electric vehicles, and it's important to look at the big picture.
  - leoedin 4y ago
    That's only true of plug-in hybrids. "Hybrid" just means a car with an electric and ICE drive train. Most hybrids aren't plug-in hybrids. They have no ability to charge their battery except from the engine.
    - adgjlsfhk1 4y ago
      right but that's easy to change.
  - XorNot 4y ago

svnt 4y ago

It is a sign of the success of the oil industry that this analysis always takes the cost of electricity generation back to the source, but assumes that fuel stations pump from a perfect source of naturally refined/distilled hydrocarbons. It is surprisingly difficult to get numbers on how much oil is used to extract, refine and transport oil. The best I found was this: https://www.speakev.com/threads/energy-required-to-refine-oil-to-petrol-diesel-and-by-products.13726/ https://www.speakev.com/threads/energy-required-to-refine-oi... Does anyone have better numbers?

semi-extrinsic 4y ago
I know Equinor publishes quite detailed numbers from their operations: https://sustainability.equinor.com/climate-tables https://sustainability.equinor.com/climate-tables The headline figure is maybe to compare 11.4 mill. tonnes CO2e emissions from "Scope 1 + Scope 2" (direct emissions from the company plus indirect emissions because they buy electricity and stuff), versus 243 mill. tonnes CO2e from Scope 3 (emissions from people burning the hydrocarbons sold). If that figure is correct, you can add 1.6 percent to the car tailpipe emissions figures to account for production and refining etc. But this is an oil & gas company that tries very hard and is among the best in the world for minimising emissions from production and refining. I would not be surprised if gasoline from US shale oil is more than an order of magnitude worse.
- thfuran 4y ago
  >EROI values for our most important fuels, liquid and gaseous petroleum, tend to be relatively high. World oil and gas has a mean EROI of about 20:1 (n of 36 from 4 publications) (Fig. 2) (see Lambert et al., 2012 and Dale, 2010 for references). The EROI for the production of oil and gas globally by publicly traded companies has declined from 30:1 in 1995 to about 18:1 in 2006 (Gagnon et al., 2009). The EROI for discovering oil and gas in the US has decreased from more than 1000:1 in 1919 to 5:1 in the 2010s, and for production from about 25:1 in the 1970s to approximately 10:1 in 2007 (Guilford et al., 2011). Alternatives to traditional fossil fuels such as tar sands and oil shale (Lambert et al., 2012) deliver a lower EROI, having a mean EROI of 4:1 (n of 4 from 4 publications) and 7:1 (n of 15 from 15 publication) https://www.sciencedirect.com/science/article/pii/S0301421513003856#bib11 https://www.sciencedirect.com/science/article/pii/S030142151...

jjtheblunt 4y ago

Does regenerative braking count as renewable energy? It's clearly absent from internal combustion (diesel or not)

acidburnNSA 4y ago
Lord I hope not. It helps with efficiency, but is no more renewable than carrying a rock upstairs and throwing it out a window onto some kind of generator.

heresie-dabord 4y ago

> the real power of electric vehicles Generation can be from clean sources and is already happening in some jurisdictions. Even if a clean source is not available, the pollution can best be controlled at the source. In this period of history, hundreds of millions of people make billions of polluting trips every day in their communities. Although owning any car is the poorest choice of all for the environment, there are two ecological benefits to driving a BEV or a PHEV. * better efficiency than ICE * zero emissions in the case of BEV, zero emissions *for most trips* in the case of PHEV

marcosdumay 4y ago

> A conventional internal combustion engine car has to convert chemical energy to kinetic energy - the absolute best theoretical efficiency of this might be 70% You mean thermal energy? Both cars are converting chemical energy to kinetic. The theoretical maximum for this is 100%. But one uses a thermal intermediate step, that reduces that maximum.

Twirrim 4y ago

One of the big sources of electricity generation here is hydroelectric, so I've been joking with my kids for a while that we have a water powered car. The first time I brought it up sparked a fun conversation as they wanted to understand how water makes electricity, and then started rabbit-holing on how magnets are involved in everything.

MuffinFlavored 4y ago

> Renewables change the picture though - once you have significant renewable generation the carbon intensity of electricity starts dropping, which means that remote powerplant vs local powerplant argument falls apart. That is when the real power of electric vehicles kicks in - they can take their energy from anywhere. How close/far would you say we are as a society on "having significant renewable generation"?

philipkglass 4y ago
I don't know where you live, but in the United States renewables have recently surpassed nuclear and coal power as sources of electricity: https://www.eia.gov/todayinenergy/detail.php?id=55960 https://www.eia.gov/todayinenergy/detail.php?id=55960 They're still pretty close to each other right now. Renewables are at 21%, coal 20%, nuclear 19%. However, nuclear is flat and coal is declining. Renewables are still growing rapidly and will widen their lead significantly in a few more years. See the first embedded chart in the article, showing output trends since 2010. Also see the short term forecast at the end of the article: "In our March Short-Term Energy Outlook, we forecast the wind share of the U.S. generation mix will increase from 11% last year to 12% this year. We forecast that the solar share will grow to 5% in 2023, up from 4% last year. The natural gas share of generation is forecast to remain unchanged from last year (39%); the coal share of generation is forecast to decline from 20% last year to 17% in 2023."
- 0cf8612b2e1e 4y ago
  I was curious, and Wikipedia lists 224 active coal plants in the USA. More amazing was that from 2010 to 2020, 240 coal plants were closed. [0] https://en.m.wikipedia.org/wiki/List_of_coal-fired_power_stations_in_the_United_States https://en.m.wikipedia.org/wiki/List_of_coal-fired_power_sta...

snitty 4y ago

>It's much easier to build highly efficient hydrocarbon power stations - typical efficiencies range from 40-60%. Just to expound on this. Power stations turn fuel to heat, and heat to electricity via steam turbines. In ICE cars, that heat is the main loss of power. Whole systems in cars are built to get rid of that excess heat in the engine.

derethanhausen 4y ago

The Prius' efficiency comes from much much more than regenerative braking. Part is a focus on good aero and low weight, like many electric cars. But most is from leveraging the electric motors to allow the engine to run at max thermal efficiency (probably a touch above your 30% figure) at nearly all times. ICEs are most efficient under medium-low RPMs and high load. The electric motors can sustain low speed cruising, letting the engine shut off entirely if it wouldn't be well utilized, and also fill in for high torque demand to keep engine power output lower.