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Correct, a lot of Mackay's estimates fail to account for the difference in delivered efficiency between electric solutions and their gas counterparts. For insta

Correct, a lot of Mackay's estimates fail to account for the difference in delivered efficiency between electric solutions and their gas counterparts. For instance in his car section[1], he estimate you'd need to produce 40kwh to drive 50km. That may be close to the true energetic content of the gas burned, but you could drive that far on just 10kwh in a modern EV, meaning electrification dropped your gross energy needs by 75%. [1] https://www.withouthotair.com/c3/page_29.shtml https://www.withouthotair.com/c3/page_29.shtml

ZeroGravitas 3y ago
He was aware of the benefits of EVs though, from a later chapter > OK, the race is over, and I’ve announced two winners – public transport, and electric vehicles. He was also very positive about heat pumps. https://www.withouthotair.com/c20/page_131.shtml https://www.withouthotair.com/c20/page_131.shtml > You’ve shown that electric cars are more energy-efficient than fossil cars. But are they better if our objective is to reduce CO2 emissions, and the electricity is still generated by fossil power- stations? > This is quite an easy calculation to do. Assume the electric vehicle’s energy cost is 20 kWh(e) per 100 km. (I think 15 kWh(e) per 100 km is perfectly possible, but let’s play sceptical in this calculation.) If grid electricity has a carbon footprint of 500 g per kWh(e) then the effective emissions of this vehicle are 100 g CO2 per km, which is as good as the best fossil cars (figure 20.9). So I conclude that switching to electric cars is already a good idea, even before we green our electricity supply.
- lostlogin 3y ago
  And that misses the petrol station thing. Stocking the station tanks (and that supply chain), staffing, etc, that doesn’t cost zero.
  - deleted 3y ago
    [deleted]
  - rcxdude 3y ago
    True, but neither does maintaining the grid
    - smileysteve 3y ago
      Marginally and variable costs it does though. A 100% capacity charging station has few variable costs compared to gasoline delivery; the grid interconnect and charging cables are equivalent to filler and tank safety inspection, not daily or weekly deliveries of fuel by pipeline + truck.
    - addicted 3y ago
      But we’re already maintaining the grid. Growing it to handle the new workload would require a fraction greater maintenance workload which would be tiny in comparison to maintaining the entire parallel infrastructure needed to get oil from a Saudi Arabia desert to a car filling up at a gas station in the middle of Wichita.
  - taylodl 3y ago
    Refining oil is a power-intensive process, requiring 5 kWH of energy per gallon of gas. This is why talks about EVs requiring so much more electrical power generation are vastly overblown - they don't account for the power consumed to pump, refine, transport, and distribute the petro products needed for ICE vehicles.
- conjecTech 3y ago
  I'm sure he was. It's easy for us to see 15 years later that the combination of EVs + solar/wind has a huge efficiency gain because you can get to avoid internal combustion altogether, but EVs were nascent enough in 2008 for that to not be as clear, so those assumptions didn't make it into his calculations.
PeterisP 3y ago
This is a bit of an apples-to-oranges comparison. If you consider the energetic content of the gas burned in a car, then you need to measure the same thing for the EV - large power plants are a bit more efficient than car engines, but unavoidably far from 100%; in order to get 10kwh of electricity to an EV the current grid would burn gas or coal with an energetic content of probably 25kwh or so. So electrification alone can't bring so large reductions in total energy consumption - it is simply one of the prerequisites for that, and it also needs to be accompanied with large scale build-up of non-fossil electricity, of renewables or nuclear.
- stavros 3y ago
  But when you're using solar to generate the energy, what's the equivalent of burning? I'd argue that it's just "whatever the panel produces". So, if you have some panels producing 1 KWh, and you need that KWh for your car, the relevant efficiency here is transport efficiency.
  - PeterisP 3y ago
    Since we currently aren't covering the existing demand for electricity with reneweables, the "marginal kwh" of electrifying some car comes from fossil fuels, not solar. Those are two separate things - electrifying some transportation need gets us X benefit, and converting some electric generation from fossil fuels to solar gets Y benefit, but the former doesn't automagically create the latter.
    - conjecTech 3y ago
      1) There is no reason to attribute all of the carbon intensity to the last use to be added. It is far more accurate to estimate the carbon intensity of something by the blended production mix at its time of use. Fossil fuel plants are often kept online for factors beyond the need for additional capacity at a certain time. 2) You are assuming there is no curtailment or rejection of wind, solar, and nuclear, which is categorically false. This is why there are time-of-day rates that vary so drastically. There are large amounts of renewable/low-carbon energy that would otherwise be wasted in pretty much every geography.

ZeroGravitas 3y ago

He was aware of the benefits of EVs though, from a later chapter > OK, the race is over, and I’ve announced two winners – public transport, and electric vehicles. He was also very positive about heat pumps. https://www.withouthotair.com/c20/page_131.shtml https://www.withouthotair.com/c20/page_131.shtml > You’ve shown that electric cars are more energy-efficient than fossil cars. But are they better if our objective is to reduce CO2 emissions, and the electricity is still generated by fossil power- stations? > This is quite an easy calculation to do. Assume the electric vehicle’s energy cost is 20 kWh(e) per 100 km. (I think 15 kWh(e) per 100 km is perfectly possible, but let’s play sceptical in this calculation.) If grid electricity has a carbon footprint of 500 g per kWh(e) then the effective emissions of this vehicle are 100 g CO2 per km, which is as good as the best fossil cars (figure 20.9). So I conclude that switching to electric cars is already a good idea, even before we green our electricity supply.

lostlogin 3y ago
And that misses the petrol station thing. Stocking the station tanks (and that supply chain), staffing, etc, that doesn’t cost zero.
- deleted 3y ago
  [deleted]
- rcxdude 3y ago
  True, but neither does maintaining the grid
  - smileysteve 3y ago
    Marginally and variable costs it does though. A 100% capacity charging station has few variable costs compared to gasoline delivery; the grid interconnect and charging cables are equivalent to filler and tank safety inspection, not daily or weekly deliveries of fuel by pipeline + truck.
  - addicted 3y ago
    But we’re already maintaining the grid. Growing it to handle the new workload would require a fraction greater maintenance workload which would be tiny in comparison to maintaining the entire parallel infrastructure needed to get oil from a Saudi Arabia desert to a car filling up at a gas station in the middle of Wichita.
- taylodl 3y ago
  Refining oil is a power-intensive process, requiring 5 kWH of energy per gallon of gas. This is why talks about EVs requiring so much more electrical power generation are vastly overblown - they don't account for the power consumed to pump, refine, transport, and distribute the petro products needed for ICE vehicles.
conjecTech 3y ago
I'm sure he was. It's easy for us to see 15 years later that the combination of EVs + solar/wind has a huge efficiency gain because you can get to avoid internal combustion altogether, but EVs were nascent enough in 2008 for that to not be as clear, so those assumptions didn't make it into his calculations.

PeterisP 3y ago

This is a bit of an apples-to-oranges comparison. If you consider the energetic content of the gas burned in a car, then you need to measure the same thing for the EV - large power plants are a bit more efficient than car engines, but unavoidably far from 100%; in order to get 10kwh of electricity to an EV the current grid would burn gas or coal with an energetic content of probably 25kwh or so. So electrification alone can't bring so large reductions in total energy consumption - it is simply one of the prerequisites for that, and it also needs to be accompanied with large scale build-up of non-fossil electricity, of renewables or nuclear.

stavros 3y ago
But when you're using solar to generate the energy, what's the equivalent of burning? I'd argue that it's just "whatever the panel produces". So, if you have some panels producing 1 KWh, and you need that KWh for your car, the relevant efficiency here is transport efficiency.
- PeterisP 3y ago
  Since we currently aren't covering the existing demand for electricity with reneweables, the "marginal kwh" of electrifying some car comes from fossil fuels, not solar. Those are two separate things - electrifying some transportation need gets us X benefit, and converting some electric generation from fossil fuels to solar gets Y benefit, but the former doesn't automagically create the latter.
  - conjecTech 3y ago
    1) There is no reason to attribute all of the carbon intensity to the last use to be added. It is far more accurate to estimate the carbon intensity of something by the blended production mix at its time of use. Fossil fuel plants are often kept online for factors beyond the need for additional capacity at a certain time. 2) You are assuming there is no curtailment or rejection of wind, solar, and nuclear, which is categorically false. This is why there are time-of-day rates that vary so drastically. There are large amounts of renewable/low-carbon energy that would otherwise be wasted in pretty much every geography.