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Why does “replace typical car with hybrid” help at all? Does regenerative braking save that much energy?

by tomp 8y ago

NLips 8y ago
Hybrids typically run the engine at or close to peak efficiency all the time, which more than makes up for transmission losses. In contrast, traditional ICE-only powered vehicles have to run the engine at a range of speeds, some of which are considerably less efficient.
rypskar 8y ago
>> Why does “replace typical car with hybrid” help at all? Does regenerative braking save that much energy? At least in my plug-in hybrid I get statistics on that. I have driven it 80% on electricity with average fuel consumption of 2.0 l/100km the 16 months I have owned it, that include 2 longer trips of 700km with average fuel consumption of 4.0 l/100km and some charging problems last winter. The car have 200hp, so would have been a lot more if not hybrid.
ed_balls 8y ago
I depends on you location and driving in the city e.g. Prius can have less total CO2 emission than Tesla S if the electricity comes from fossil fuels. https://www.youtube.com/watch?v=6RhtiPefVzM https://www.youtube.com/watch?v=6RhtiPefVzM
- tomp 8y ago
  I find that hard to believe. So you're saying that Prius, despite being more complicated (as it needs to route both internal combustion and electric power to the wheels), has an electric motor/transmission more efficient than Tesla and internal combustion engine more efficient than power plants? The only way I think that's possible is if weight is taken into account, Prius seems to be a bit smaller and thus possibly lighter than Model S...
  - curlypaul924 8y ago
    Are you taking into consideration the loss of energy in power transmission and distribution? (I also find the argument hard to believe, but I'd be interested in seeing a proper comparison)
    - tomp 8y ago
      Well, yeah, that's basically equivalent to saying that you'd save money by running an internal combustion engine at home, rather than buying electricity from the grid. Sounds unlikely - although there are potential savings to be had if you take into account the heat generated, which is lost from the powerplant but a household could use it for heating - check out mCHP https://en.wikipedia.org/wiki/Micro_combined_heat_and_power https://en.wikipedia.org/wiki/Micro_combined_heat_and_power
      - curlypaul924 8y ago
        It's more like saying that you'd save fuel by running an equivalent ICE at home. You'd be unlikely to save money, because of economies of scale.
        tomp 8y ago
        But I imagine that fuel is the vast majority of the cost, at least operational cost... and the initial investment is also at least to some extent dependent on the resources used (energy, matter).
  - zamfi 8y ago
    I think this is possible if the Tesla’s electricity is coming from burning coal, which produces ~double the CO2 emissions per unit energy compared with gas. (Though this seems annoying to actually calculate, so I haven’t.) You would not be looking at efficiency from a energy/$ perspective, which is what industry power generators care about, but rather energy/ton of CO2, which they rarely care about.
curlypaul924 8y ago
Yes, it does -- why else would the endurance racing world be embracing hybrid technology? A hybrid car has won Lemans for the last 5 years. At least with the Prius-style hybrids, though, regenerative braking isn't the only advantage: * The engine is an Atkinson cycle, which has better thermal efficiency than a typical Otto cycle engine. * The electric motor is providing torque off the line, so there is no need for a torque converter (which reduces efficiency). * The engine can be completely shut off when cruising at low speeds. * The power split device (PSD) is more reliable than a traditional transmission, reducing maintenance costs over the lifetime of the vehicle. (it is much less labor intensive to replace the battery than to service the transmission) The advantages add up when driving around town, but at highway speeds, a 3-cylinder or small 4-cylinder non-hybrid will often have better gas mileage.
- SmellyGeekBoy 8y ago
  > Yes, it does -- why else would the endurance racing world be embracing hybrid technology? A hybrid car has won Lemans for the last 5 years. While I agree with your sentiment, I think it's dishonest to not mention the fact that diesels were absolutely dominating until the rules were changed in hybrids' favour a few years back.

Why does “replace typical car with hybrid” help at all? Does regenerative braking save that much energy?

by tomp 8y ago

Why does “replace typical car with hybrid” help at all? Does regenerative braking save that much energy?

Hybrids typically run the engine at or close to peak efficiency all the time, which more than makes up for transmission losses. In contrast, traditional ICE-only powered vehicles have to run the engine at a range of speeds, some of which are considerably less efficient.

rypskar 8y ago

>> Why does “replace typical car with hybrid” help at all? Does regenerative braking save that much energy? At least in my plug-in hybrid I get statistics on that. I have driven it 80% on electricity with average fuel consumption of 2.0 l/100km the 16 months I have owned it, that include 2 longer trips of 700km with average fuel consumption of 4.0 l/100km and some charging problems last winter. The car have 200hp, so would have been a lot more if not hybrid.

ed_balls 8y ago

I depends on you location and driving in the city e.g. Prius can have less total CO2 emission than Tesla S if the electricity comes from fossil fuels. https://www.youtube.com/watch?v=6RhtiPefVzM https://www.youtube.com/watch?v=6RhtiPefVzM

tomp 8y ago
I find that hard to believe. So you're saying that Prius, despite being more complicated (as it needs to route both internal combustion and electric power to the wheels), has an electric motor/transmission more efficient than Tesla and internal combustion engine more efficient than power plants? The only way I think that's possible is if weight is taken into account, Prius seems to be a bit smaller and thus possibly lighter than Model S...
- curlypaul924 8y ago
  Are you taking into consideration the loss of energy in power transmission and distribution? (I also find the argument hard to believe, but I'd be interested in seeing a proper comparison)
  - tomp 8y ago
    Well, yeah, that's basically equivalent to saying that you'd save money by running an internal combustion engine at home, rather than buying electricity from the grid. Sounds unlikely - although there are potential savings to be had if you take into account the heat generated, which is lost from the powerplant but a household could use it for heating - check out mCHP https://en.wikipedia.org/wiki/Micro_combined_heat_and_power https://en.wikipedia.org/wiki/Micro_combined_heat_and_power
    - curlypaul924 8y ago
      It's more like saying that you'd save fuel by running an equivalent ICE at home. You'd be unlikely to save money, because of economies of scale.
      - tomp 8y ago
        But I imagine that fuel is the vast majority of the cost, at least operational cost... and the initial investment is also at least to some extent dependent on the resources used (energy, matter).
- zamfi 8y ago
  I think this is possible if the Tesla’s electricity is coming from burning coal, which produces ~double the CO2 emissions per unit energy compared with gas. (Though this seems annoying to actually calculate, so I haven’t.) You would not be looking at efficiency from a energy/$ perspective, which is what industry power generators care about, but rather energy/ton of CO2, which they rarely care about.

curlypaul924 8y ago

Yes, it does -- why else would the endurance racing world be embracing hybrid technology? A hybrid car has won Lemans for the last 5 years. At least with the Prius-style hybrids, though, regenerative braking isn't the only advantage: * The engine is an Atkinson cycle, which has better thermal efficiency than a typical Otto cycle engine. * The electric motor is providing torque off the line, so there is no need for a torque converter (which reduces efficiency). * The engine can be completely shut off when cruising at low speeds. * The power split device (PSD) is more reliable than a traditional transmission, reducing maintenance costs over the lifetime of the vehicle. (it is much less labor intensive to replace the battery than to service the transmission) The advantages add up when driving around town, but at highway speeds, a 3-cylinder or small 4-cylinder non-hybrid will often have better gas mileage.

SmellyGeekBoy 8y ago
> Yes, it does -- why else would the endurance racing world be embracing hybrid technology? A hybrid car has won Lemans for the last 5 years. While I agree with your sentiment, I think it's dishonest to not mention the fact that diesels were absolutely dominating until the rules were changed in hybrids' favour a few years back.