3 ms·

That's not obvious to me. Sure, using the numbers and technology we all learned about in thermo class 20 years ago (best ICE efficiency of a car is 20% usually

That's not obvious to me. Sure, using the numbers and technology we all learned about in thermo class 20 years ago (best ICE efficiency of a car is 20% usually gets much worse), I agree. But the hybrid drivetrain throws all the assumptions of that common wisdom in the air. Namely: - Throttle can be open all the way when power is needed, the engine turned off otherwise - Engine can be made for efficiency, not power density - Engine can be sized to average power, not worst case scenario over the lifetime of the car On top of that, in the last 20 years, the power electronics revolution has made recovery of the energy in the exhaust stream possible (see F1). I'd love to have an ICE expert tell me why ICE efficiency can't be double what common wisdom tells me what it is. I suspect it's environmental laws regulating NOx emissions (thus putting a hard upper bound on compression ratios). I really doubt an electric car can beat the carbon emissions of a natural gas powered ICE that achieves 40% efficiency. Not with our current energy mix anyway

JshWright 5y ago
ICE efficiency can absolutely be improved. The question is if it's worth it. EVs are already better, even assuming zero renewables on the grid (which obviously isn't the case), and get better each year as more renewables come online at an ever increasing pace. We can either continue on the current path (which is certainly the path of least resistance), or we can pivot and make a massive investment in building out a CNG distribution system (not to mention all the R&D and production cost that would go into swapping out any significant percentage of the current vehicles on the road). We need to convert the grid away from fossil fuels anyway. If we're doing that already, why take on the extra work of building out a consumer-facing CNG infrastructure? I think CNG (and, for that matter, hydrogen) makes a ton of sense in certain circumstances. Mass transit fleets, truck depots, etc
- sasfasaf 5y ago
  Ok, but I want numbers. How good can ICEs get? Mercedes claims their 1.5L F1 engine - designed for power, not efficiency - is over 50% thermally efficient. An EV can't match that. Not with the gas cycle efficiency and all the line power losses.
  - JshWright 5y ago
    The practical limit for an ICE engine in a road car (in a hybrid configuration) is probably somewhere in the neighborhood of 50% (small sizes make efficiency harder). A theoretical ideal ICE hybrid would almost certainly beat a current day EV on the current day grid. But that's not a fair comparison, and we have to modernize the grid anyway. F1 PUs are absolutely designed with efficiency in mind. The FIA limits both the maximum fuel used in a race, as well as the instantaneous fuel flow rate. When fuel flow rates are capped, getting more power is the same thing as getting more efficiency.

JshWright 5y ago

ICE efficiency can absolutely be improved. The question is if it's worth it. EVs are already better, even assuming zero renewables on the grid (which obviously isn't the case), and get better each year as more renewables come online at an ever increasing pace. We can either continue on the current path (which is certainly the path of least resistance), or we can pivot and make a massive investment in building out a CNG distribution system (not to mention all the R&D and production cost that would go into swapping out any significant percentage of the current vehicles on the road). We need to convert the grid away from fossil fuels anyway. If we're doing that already, why take on the extra work of building out a consumer-facing CNG infrastructure? I think CNG (and, for that matter, hydrogen) makes a ton of sense in certain circumstances. Mass transit fleets, truck depots, etc

sasfasaf 5y ago
Ok, but I want numbers. How good can ICEs get? Mercedes claims their 1.5L F1 engine - designed for power, not efficiency - is over 50% thermally efficient. An EV can't match that. Not with the gas cycle efficiency and all the line power losses.
- JshWright 5y ago
  The practical limit for an ICE engine in a road car (in a hybrid configuration) is probably somewhere in the neighborhood of 50% (small sizes make efficiency harder). A theoretical ideal ICE hybrid would almost certainly beat a current day EV on the current day grid. But that's not a fair comparison, and we have to modernize the grid anyway. F1 PUs are absolutely designed with efficiency in mind. The FIA limits both the maximum fuel used in a race, as well as the instantaneous fuel flow rate. When fuel flow rates are capped, getting more power is the same thing as getting more efficiency.