5 ms·

From what I understand, these TWhs refer to total energy usage, not electricity usage. If you replace a ICE by an BEV powered by solar cells, you actually redu

From what I understand, these TWhs refer to total energy usage, not electricity usage. If you replace a ICE by an BEV powered by solar cells, you actually reduce the total TWhs because of efficiecy: - ICE: 6L of gasoline per 100km, that equals to about 60 KWh - BEV: 17KWh for the same distance. The same applies to heat-pumps and some industrial processes.

conjecTech 3y ago
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.
bufferoverflow 3y ago
But that doesn't reduce consumption of electricity. Your gasoline cars don't consume any, and your EVs consume a lot.
- avar 3y ago
  Increasing electricity consumption while lowering overall energy consumption is the point.
- sundvor 3y ago
  Presently running my EV just about 100% on rooftop solar energy, which is possible about 3/5ths of year in my situation. Melbourne, AUS, admittedly, but still. Fuel delivery still requires a crap load of energy, some of it in the form of electricity - even just running the pumps 24x7 - but there's so many elements in that value chain it could fill volumes. There's far fewer even in the dirtiest of EV charging scenarios.
- rsynnott 3y ago
  Again, the numbers _do not refer to consumption of electricity_, they refer to consumption of energy.
helsinkiandrew 3y ago
Probably more significantly: about 30-40% of UK energy use is gas central heating which is 90-95% efficient. Electric heat pumps (beginning to be installed in numbers the U.K.) are 300-400% efficient. That’s nearly half the saving
- jillesvangurp 3y ago
  Industrial heating is also a big factor. That too is dependent on gas right now. A lot of that could shift to electrical in the next few decades. And the rest might transition to hydrogen.

conjecTech 3y ago

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.

bufferoverflow 3y ago

But that doesn't reduce consumption of electricity. Your gasoline cars don't consume any, and your EVs consume a lot.

avar 3y ago
Increasing electricity consumption while lowering overall energy consumption is the point.
sundvor 3y ago
Presently running my EV just about 100% on rooftop solar energy, which is possible about 3/5ths of year in my situation. Melbourne, AUS, admittedly, but still. Fuel delivery still requires a crap load of energy, some of it in the form of electricity - even just running the pumps 24x7 - but there's so many elements in that value chain it could fill volumes. There's far fewer even in the dirtiest of EV charging scenarios.
rsynnott 3y ago
Again, the numbers _do not refer to consumption of electricity_, they refer to consumption of energy.

helsinkiandrew 3y ago

Probably more significantly: about 30-40% of UK energy use is gas central heating which is 90-95% efficient. Electric heat pumps (beginning to be installed in numbers the U.K.) are 300-400% efficient. That’s nearly half the saving

jillesvangurp 3y ago
Industrial heating is also a big factor. That too is dependent on gas right now. A lot of that could shift to electrical in the next few decades. And the rest might transition to hydrogen.