I am curious about the various types of plug in hybrid vehicles, and which design is the most efficient. Charge depleting designs can run on batteries alone, then switch to charge sustaining mode by turning on a gas engine to generate electricity.
But this seems inherently inefficient, because during charge depleting mode, the batteries are expending energy to lug around the gasoline engine, which is doing no work. Likewise, when it switches to charge sustaining mode, the gas engine is lugging around batteries that are doing essentially no work.
Wouldn’t it be more efficient to use a smaller gas engine that runs constantly at peak efficiency RPMs, to provide only enough energy to extend the life of the batteries to a useful range? That way, the vehicle is lighter (smaller engine) which makes the batteries last longer.
For example, if a fully charged battery, running as the sole energy source, can provide a 40 mile range, but by adding a small gas powered generator that runs all the time, the range is extended to 80 miles (hypothetical mileage). Would this not be more efficient than a similar hybrid that switched between charge depleting and charge sustaining modes?
I understand this vehicle does not achieve the goal of operating without fossil fuel, but am I wrong to think it might be more efficient in its overall use of energy, both in charging the batteries and using fossil fuel? This also does not mean mixed mode hybrids could not be ideal for drivers who made mostly short trips within the range of the batteries; but in situations where the driver was consistently needing a vehicle that could go beyond the range of batteries alone every day, wouldn’t this be a more energy efficient solution?
I am envisioning a plug-in hybrid with a small gas turbine engine running constantly at peak efficiency RPMs, only large enough to provide enough electricity to extend the range of the battery pack, not replace it. Plus, a gas turbine is much more flexible in the type of fuel is uses, including biodiesel and ethanol.
I want my turbine car, dammit!