alt Hacker News>This isn't like a hybrid car. It's a parallel hybrid, where the gas engine is just big enough for efficient cruise at altitude, and the electric motor/generator provides extra power for takeoff and ascent (or go-around power), and then charges slowly during cruise if needed.
Isn't that exactly what hybrid cars (e.g. Prius) are? Extremely efficient gas engine for highway cruising, but insufficient for acceleration, which is aided by electric motors?
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IDK if anyone really answered -this- question properly, so I will.
> Isn't that exactly what hybrid cars (e.g. Prius) are? Extremely efficient gas engine for highway cruising, but insufficient for acceleration, which is aided by electric motors?
Well, it kinda depends. Where Hybrids get the biggest MPG boost is in city driving. The stop and go traffic lets you use Regen braking and go quite some time without the engine kicking back on while still moving forward.
I still don't understand Honda's system enough to speak well on it, but I can speak to THS because it seems to be the cheapest to do and is most proven on the road.
The general parameters for a THS type system on a Toyota Prius or Rav4, or a Ford Maverick/Fusion/Escape is a 2.0L or 2.5L (at least in modern US examples) engine paired to a simple planetary gearset containing a power split device. It is a single speed (At least in the cheap configurations, however that simplicity is possibly close enough to be viable for air usage vs a reduction gear.) That's part of why they tend to have fairly large engines, the valve timing magic gives them at least a bit more HP to not be too bad on the highway.
> but insufficient for acceleration
Going back to the modern cases, the engine is typically sized large enough to give some acceleration even on the highway. Not always great but usually enough.
At least as far as the non-plug-in hybrids, the 0-35MPH can be surprisingly peppy.
The bigger magic (again, at least as far as THS) is it makes it easy to just run the engine at the 'most optimal RPM' for certain tasks, excess energy gets piped to the battery or back out through the system, this does also help reliability tho, because you can then design the reliability of the engine around certain RPM ranges...
This is mostly correct. The Prius is actually a series-parallel hybrid, as it maintains a direct mechanical link between the engine and the wheels (and the engine is capable of adding power to the wheels) but it also uses two electric motors to isolate the two degrees of freedom (engine rpm and wheel speed). This second part is the series bit: the wheels and the engine are, in principle, fully independent, because the motors can absorb or add power to the crankshaft and the driveshaft to hit a target rpm without changing the rpm of the other shaft. In practice, the Prius doesn't run at a constant rpm due to sizing constraints of the motors, as the mechanical linkage means that one motor has to be able to absorb the engine power and torque of the other motor, which is impossible across all conditions.
Most hybrids are actually parallel or series-parallel. Series hybrids are comparatively rare because the traction motor has to be sized for the full operational range of the vehicle. Their primary advantages are mechanical simplicity and packaging; even though the power electronics and motors are bigger, the lack of mechanical coupling means you can put them wherever is convenient.
The Prius uses a planetary gear set to blend power of the engine with that of the two motor-generators.
Both the engine and motors are used at all speeds. Particularly during highway acceleration the entire assembly rotates in the same direction.