mpg -- electric over gas?

[Kablooie]

I've noticed that when the battery starts to get low, the gas engine kicks in to recharge it, even if the gas engine isn't needed otherwise.

Does anyone know how efficient the electric engine is relative to the gas engine in terms of gas mileage?

I assume the electiric engine alone, (without regenerated power), would be less efficient than the gas engine alone.

[DanMan32]

From a pure electric to kinetic power standpoint, I believe electric motors are more efficient. However, where are you going to get the power? With the Prius, you have two sources: the battery, and the ICE through the power SPlit Device (PSD) and through the inverters. There are some losses with these conversions. Even with the battery, you have to get power to IT somehow, and again, you have 2 options: from regenerative power, and from ICE, both going through inverters.

But electric power has its advantages over ICE, mostly large instant torque at low speeds. That's why the Hybrid Synergy Drive. It takes the best of both worlds working cooperatively at their best conditions. Also, running a motor efficiently and cleanly doesn't require a warmup time, unlike ICE. Much of ICE's waste is waste heat. If we can find another way to provide similar mass power generaton without requiring heat, we would improve things drastically. Maybe that is the point of hydrogen power.

OK, I admit, I probably rambled a great deal without really saying much that is concrete.

[lawlopez]

Think of hydrogen as a gasoline made from electricity. If the hydogen goes through a internal combustion engine it will have losses similar to those experienced by gasoline and diesel. If the electricty comes off the grid then it will have losses similar to all power comming off the grid.

[DanMan32]

Oh, I agree, though correct me if I am wrong, but isn't hydrogen combustion more efficient? At least you won't have to deal with warmups simply for emissions reasons.

My focus was that electric motors achieve peak efficiency pretty much instantly; no warm up period needed, where ICE needs quite a bit of time to become efficient, not to mention to keep emissions down. That is where we get a significant amount of loss.

[Tideland Prius]

Well technically it's not synergy since total output is less than the sum of its parts (unless we're using battery output and not the motor's output)

[hdrygas]

Well technically it's not synergy since total output is less than the sum of its parts (unless we're using battery output and not the motor's output)

You are correct on the strict definition of synergy, however in a more poetic sense there is a synergy. HSD gives us a synergy of low end torque and efficiency of the ICE in its best range. Toyota stretched the definition but I think in a responsible way. It is Hybrid Synergy Drive and that is more than a marketing statement.

[lawlopez]

synergy merely means that that they work together not that they violate the conservation of energy law.

It means that they are more than the sum of their parts, not that they violate the laws of thermodynamics.

In English, the battery and electric motor will get down the block.

The gas engine will get you 40 MPG.

Together they get you 500 miles on a tank of gas.

[DanMan32]

Right, when I explain the Prius drive system compared to other hybrid methods, the best word I can come up with is synergy, working together, since you can't have ICE power without MG power SOMEWHERE. Though you could have MG power without ICE, though not for long.