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Then generate power at a coal or natural gas power plant. Until we get further along with renewables, the total environmental impact of replacing everything wit

Then generate power at a coal or natural gas power plant. Until we get further along with renewables, the total environmental impact of replacing everything with electric today probably isn’t worth it. Example: https://www.reuters.com/business/autos-transportation/when-do-electric-vehicles-become-cleaner-than-gasoline-cars-2021-06-29/ https://www.reuters.com/business/autos-transportation/when-d... I remember having a heated discussion with someone about this at work, and it came down to where you were charging that Tesla and if you had rooftop solar (not even discussing the environmental impact of mfg + shipping + installation + support + useable lifetime of the solar panels, home batteries, and support accessories). And at the end of the day, moving around a 5000# Tesla or 6500# F150 Lightning takes a lot more power in any form than a 3400# Civic / Camry.

bobthepanda 5y ago
My understanding is that bulk power generation is probably more efficient than having the motive power in the locomotive itself. There are also isolated use cases that the US railroads have been electrified for in the past (a lot of it was de-electrified to artificially boost revenues with asset sales in the midcentury). Namely * mountain tunnels; a fair amount of Western mountain tunnels can only accommodate one diesel train at a time due to ventilation, and the crews carry respirators and oxygen in case the train stalls inside * any sort of long sustained slope; downhill trains using regenerative braking can return electricity for those going uphill
- mlyle 5y ago
  > My understanding is that bulk power generation is probably more efficient than having the motive power in the locomotive itself. Almost certainly. But this probably evaporates once you need to pull significant amount of battery.
  - ErikCorry 5y ago
    Trains are very efficient at carrying weight, especially if they can dump power into the grid (or battery) when braking. That metal-on-metal wheel has super low rolling resistance.
    - mlyle 5y ago
      > Trains are very efficient at carrying weight Sure. But you also need a whole lot of them to provide sustained power to move a large train for a decent trip length. > especially if they can dump power into the grid (or battery) when braking Smaller benefit here to regen. Sure, a 10000 tonne train has a lot of kinetic energy-- maybe 3 gigajoules or something. But compare to > 50MW to keep that train moving at a decent clip. So a complete stop with 100% of the energy recaptured is only about 60 seconds of rolling resistance energy use.
      - ErikCorry 5y ago
        I think the cost of batteries is going to be a bigger issue than the weight. Which is why hybrid (battery combined with overhead power lines) looks so attractive to me.
        mlyle 5y ago
        > Which is why hybrid (battery combined with overhead power lines) looks so attractive to me. It may be good for some segments, but consider the number of charge cycles and charge/discharge rate, along with the peak charging currents on the overhead lines. For, say, 10000 tonne trains, 15MW sustained is a good very optimistic target for how much power you need to put out to keep rolling (before you make this any worse with adding battery mass and before you consider e.g. slopes, braking, etc). If your goal is a discharge rate of C/1, you're carrying 75 tonnes of batteries-so it masses about 1% more. Then, what duty cycle are you charging at? 100% coverage from the overhead power lines means you need to bring 15MW into the train. If the goal is a big saving in the amount of overhead power lines needed, 10% coverage from the overhead power lines means you'll instead need to bring 150MW into the train during those spans (and, this is a really aggressive 10C charge rate...) I think C/1 is too aggressive for good cycle service, 10C is waaaay too aggressive for charging-- and these are best case scenario (flat ground, etc). If you multiply the amount of batteries by a big amount, now the mass change to the train and the rolling resistance contribution to the train from batteries becomes significant). edit: in the end, I think you're usually better off just electrifying the portions of the train route where it's easiest, and burning diesel the rest of the way, instead of trying to somehow dotted-line-overhead-electrify things and limp through with batteries.
deleted 5y ago
[deleted]
callalex 5y ago
Even the most perfect internal combustion engine only manages to turn 20% of burned energy into motion. You can understand this intuitively by realizing every gas car has a big radiator whose sole job is to dump energy into the atmosphere quickly.
- ummonk 5y ago
  Pretty sure Skyactiv-X gets 40%+ peak thermal efficiency. As do diesel engines. Toyota's dynamic force engine is up there too.
  - callalex 5y ago
    Sure, hooked up to a bench with ideal temperature, RPM, throttle, auspicious planetary positions etc. Put that same engine in a car that drives around and you won’t see anywhere near that.
- adrian_b 5y ago
  Two-stroke Diesel engines used in ships have an efficiency well over 50%, up to 59% for those with waste heat recovery systems. High-temperature gas turbines can also have efficiencies over 50%. Modern four-stroke internal combustion engines used in cars and trucks can have an efficiency over 40%, up to 45%. That said, such efficiencies remain low compared to electric motors with efficiencies over 95% and with combined cycle power plants which can reach an efficiency of 65% (while power plants with heat cogeneration may reach efficiencies around 80%).
  - bluGill 5y ago
    The efficiency of a modern engine at best is what you say. However in the real world you rarely see the best and so the other claim is also right, your typical car is running around 20%efficient ,but it can get over 40
mlyle 5y ago
> I remember having a heated discussion with someone about this at work, and it came down to where you were charging that Tesla This sounds like a faulty analysis. Generally even if 100% of your electricity is something moderately bad, like natural gas, end-to-end power use is better than an ICE with gasoline. Figure an electric car is 150 watt-hours per mile, and charging is 94% efficient (pessimistic, but makes the numbers round). Natural gas is 0.4 kilograms/(KWhr), so about 65 grams of CO2 emitted for that mile. Compare to 8.5 kilograms of CO2 emitted from burning a gallon of gas, so you'd need to get 130 miles to the gallon to be equivalent. Considering lifecycle costs makes things closer, but not super close. > and if you had rooftop solar Most people charge at night, so your own rooftop doesn't help. (Also, most places the renewable mix is worse at night, but not in all: in some places wind and hydroelectric "win"). > And at the end of the day, moving around a 5000# Tesla or 6500# F150 Lightning takes a lot more power in any form than a 3400# Civic / Camry. More mass means slightly more tire friction and means more kinetic energy-- a big fraction of which you get back in regen.
lostlogin 5y ago
The equation is so complicated. The petrol burning car has to get fuel. You have to drive to a station that had to be built, the station has to be staffed and the fuel and staff hauled there. Obviously electric requires infrastructure too, but it would be good to see a full breakdown and I can’t find one.
shagmin 5y ago
In addition to the other comments, buyers aren't generally deciding between a 1/2 ton pickup and mid-size sedan anyway, or a luxury car and a small compact sedan. And I agree it really varies where you live and other variables, but that to me doesn't matter when 1) ICE vehicles aren't really that efficient anyway. 2) Even ignoring the first point, it's possible electric vehicle owners are more likely to get much of their electricity from greener sources than non-electric vehicle owners, and the extra demand on the grid requires more energy production to be built, and new energy production is probably going to be a lot greener than old sources. 3) A lot of people are somewhat environmentally conscious but only as convenience and their current lifestyle allow. People know a Civic is probably more environmentally friendly than 99% of cars, and don't care. Then you can get in how many oil spills have been prevented, etc.,
beerandt 5y ago
The term you're looking for is LCA (Life Cycle Analysis). Includes energy and emissions calculations that take into account embedded costs. Might also search for Sustainability Engineering.

bobthepanda 5y ago

My understanding is that bulk power generation is probably more efficient than having the motive power in the locomotive itself. There are also isolated use cases that the US railroads have been electrified for in the past (a lot of it was de-electrified to artificially boost revenues with asset sales in the midcentury). Namely * mountain tunnels; a fair amount of Western mountain tunnels can only accommodate one diesel train at a time due to ventilation, and the crews carry respirators and oxygen in case the train stalls inside * any sort of long sustained slope; downhill trains using regenerative braking can return electricity for those going uphill

mlyle 5y ago
> My understanding is that bulk power generation is probably more efficient than having the motive power in the locomotive itself. Almost certainly. But this probably evaporates once you need to pull significant amount of battery.
- ErikCorry 5y ago
  Trains are very efficient at carrying weight, especially if they can dump power into the grid (or battery) when braking. That metal-on-metal wheel has super low rolling resistance.
  - mlyle 5y ago
    > Trains are very efficient at carrying weight Sure. But you also need a whole lot of them to provide sustained power to move a large train for a decent trip length. > especially if they can dump power into the grid (or battery) when braking Smaller benefit here to regen. Sure, a 10000 tonne train has a lot of kinetic energy-- maybe 3 gigajoules or something. But compare to > 50MW to keep that train moving at a decent clip. So a complete stop with 100% of the energy recaptured is only about 60 seconds of rolling resistance energy use.
    - ErikCorry 5y ago
      I think the cost of batteries is going to be a bigger issue than the weight. Which is why hybrid (battery combined with overhead power lines) looks so attractive to me.
      - mlyle 5y ago
        > Which is why hybrid (battery combined with overhead power lines) looks so attractive to me. It may be good for some segments, but consider the number of charge cycles and charge/discharge rate, along with the peak charging currents on the overhead lines. For, say, 10000 tonne trains, 15MW sustained is a good very optimistic target for how much power you need to put out to keep rolling (before you make this any worse with adding battery mass and before you consider e.g. slopes, braking, etc). If your goal is a discharge rate of C/1, you're carrying 75 tonnes of batteries-so it masses about 1% more. Then, what duty cycle are you charging at? 100% coverage from the overhead power lines means you need to bring 15MW into the train. If the goal is a big saving in the amount of overhead power lines needed, 10% coverage from the overhead power lines means you'll instead need to bring 150MW into the train during those spans (and, this is a really aggressive 10C charge rate...) I think C/1 is too aggressive for good cycle service, 10C is waaaay too aggressive for charging-- and these are best case scenario (flat ground, etc). If you multiply the amount of batteries by a big amount, now the mass change to the train and the rolling resistance contribution to the train from batteries becomes significant). edit: in the end, I think you're usually better off just electrifying the portions of the train route where it's easiest, and burning diesel the rest of the way, instead of trying to somehow dotted-line-overhead-electrify things and limp through with batteries.

deleted 5y ago

[deleted]

callalex 5y ago

Even the most perfect internal combustion engine only manages to turn 20% of burned energy into motion. You can understand this intuitively by realizing every gas car has a big radiator whose sole job is to dump energy into the atmosphere quickly.

ummonk 5y ago
Pretty sure Skyactiv-X gets 40%+ peak thermal efficiency. As do diesel engines. Toyota's dynamic force engine is up there too.
- callalex 5y ago
  Sure, hooked up to a bench with ideal temperature, RPM, throttle, auspicious planetary positions etc. Put that same engine in a car that drives around and you won’t see anywhere near that.
adrian_b 5y ago
Two-stroke Diesel engines used in ships have an efficiency well over 50%, up to 59% for those with waste heat recovery systems. High-temperature gas turbines can also have efficiencies over 50%. Modern four-stroke internal combustion engines used in cars and trucks can have an efficiency over 40%, up to 45%. That said, such efficiencies remain low compared to electric motors with efficiencies over 95% and with combined cycle power plants which can reach an efficiency of 65% (while power plants with heat cogeneration may reach efficiencies around 80%).
- bluGill 5y ago
  The efficiency of a modern engine at best is what you say. However in the real world you rarely see the best and so the other claim is also right, your typical car is running around 20%efficient ,but it can get over 40

mlyle 5y ago

> I remember having a heated discussion with someone about this at work, and it came down to where you were charging that Tesla This sounds like a faulty analysis. Generally even if 100% of your electricity is something moderately bad, like natural gas, end-to-end power use is better than an ICE with gasoline. Figure an electric car is 150 watt-hours per mile, and charging is 94% efficient (pessimistic, but makes the numbers round). Natural gas is 0.4 kilograms/(KWhr), so about 65 grams of CO2 emitted for that mile. Compare to 8.5 kilograms of CO2 emitted from burning a gallon of gas, so you'd need to get 130 miles to the gallon to be equivalent. Considering lifecycle costs makes things closer, but not super close. > and if you had rooftop solar Most people charge at night, so your own rooftop doesn't help. (Also, most places the renewable mix is worse at night, but not in all: in some places wind and hydroelectric "win"). > And at the end of the day, moving around a 5000# Tesla or 6500# F150 Lightning takes a lot more power in any form than a 3400# Civic / Camry. More mass means slightly more tire friction and means more kinetic energy-- a big fraction of which you get back in regen.

lostlogin 5y ago

The equation is so complicated. The petrol burning car has to get fuel. You have to drive to a station that had to be built, the station has to be staffed and the fuel and staff hauled there. Obviously electric requires infrastructure too, but it would be good to see a full breakdown and I can’t find one.

shagmin 5y ago

In addition to the other comments, buyers aren't generally deciding between a 1/2 ton pickup and mid-size sedan anyway, or a luxury car and a small compact sedan. And I agree it really varies where you live and other variables, but that to me doesn't matter when 1) ICE vehicles aren't really that efficient anyway. 2) Even ignoring the first point, it's possible electric vehicle owners are more likely to get much of their electricity from greener sources than non-electric vehicle owners, and the extra demand on the grid requires more energy production to be built, and new energy production is probably going to be a lot greener than old sources. 3) A lot of people are somewhat environmentally conscious but only as convenience and their current lifestyle allow. People know a Civic is probably more environmentally friendly than 99% of cars, and don't care. Then you can get in how many oil spills have been prevented, etc.,

beerandt 5y ago

The term you're looking for is LCA (Life Cycle Analysis). Includes energy and emissions calculations that take into account embedded costs. Might also search for Sustainability Engineering.