Electric Super Duty??

[Overtaxed]

Some recent news from the EAA Sport Aviation magazine (Dec 2020). A new startup company called Turbotech in France is building small turbine engines for small aircraft along with turbine powered generators for hybrid aircraft. The generator spins at the same speed as the turbine so no gear reduction with the total package weighing 254 lbs. (less than my 5.5kw Onan, 290 lbs.) and produces 55kw. NOT 5.5 but 55 kw. It runs on Jet fuel, diesel or biofuel. Of course this unit still uses fossil fuel but a different possibility for a large electric vehicle.

Now we're talking man! This is exactly the kind of tech that will make a semi (or big pickup towing an RV) feasible in the short-mid term. I say that because, maybe, long enough term, we figure out ways to deal with the "math" issues I posted above and pure EV semis, but something like this can get there in the here and now.

55KW means that little engine is putting out about 110HP! Amazing for something that light.

[Chewwi]

55KW means that little engine is putting out about 110HP! Amazing for something that light.

Just a little off.

55kW = 73.8hp

[Overtaxed]

Just a little off.

55kW = 73.8hp

Touche. However, with losses in the generation, 2HP per KW is a decent approximation. Perfect generator efficiency, you're right; but practically, you'll need more than 74HP to spin a 55KW generator (assuming it's using all 55KW).

[Airrace]

@Overtaxed @Chewwi
The magazine article does say 74hp. Also working on a 90 kw (121hp). They claim that the fuel burn is 4-6 gallons an hour at cruise. What that will convert to in a ground vehicle I'm not sure.

[Chewwi]

Touche. However, with losses in the generation, 2HP per KW is a decent approximation. Perfect generator efficiency, you're right; but practically, you'll need more than 74HP to spin a 55KW generator (assuming it's using all 55KW).

Electrical losses are already accounted for. The output of the turbine generator is 55kW DC. The Turbotech website states the final output is from a power electronic converter which indicates the turbine is driving an AC generator that feeds the converter. Industrial motors and electric generators are typically greater than 95% efficiency. The inefficiencies in this machine are almost all on the turbine side, not the generator side.

[Airrace]

The web site says it is "ultra quite", but not sure what that really means. The helicopter engines in hydroplanes seem to be quite compared to an APU in a C-141 or C-17 (90kw plus air) and where does the heat go? While still using fossil fuel, is the cost of an all electric truck comparable to the current 1 ton trucks we currently drive. And will we need around 600kw to meet the 450 hp we have now? Will we need that much? I'm not sure how all this translates back and forth. I get the feeling I'm comparing apples and walnuts to each other.

[Chewwi]

The web site says it is "ultra quite", but not sure what that really means. The helicopter engines in hydroplanes seem to be quite compared to an APU in a C-141 or C-17 (90kw plus air) and where does the heat go? While still using fossil fuel, is the cost of an all electric truck comparable to the current 1 ton trucks we currently drive. And will we need around 600kw to meet the 450 hp we have now? Will we need that much? I'm not sure how all this translates back and forth. I get the feeling I'm comparing apples and walnuts to each other.

Ultra quiet is a relative term and it could still be deafening.

I’m pretty sure you know where the heat goes based on your profile (air racing and USAFR).

If you want the equivalent of 450 hp, you will need about 336 kW (not 600kW).

[Overtaxed]

Ultra quiet is a relative term and it could still be deafening.

I’m pretty sure you know where the heat goes based on your profile (air racing and USAFR).

If you want the equivalent of 450 hp, you will need about 336 kW (not 600kW).

Without batteries, yes, you'd need a big generator. But the reason diesel-electric is so interesting is because you can store that electric (in a battery pack) so that the peak loads (starting from a stop, for example) can be serviced at 1000HP using the batteries, and then, during cruise operations, when you maybe need 100HP to keep rolling, the generator can charge the batteries. Driving is very variable on demand, going up a huge hill with a massive load, might take every HP the engine can put out, however, going downhill on the other side, instead of 450HP, you actually are a negative HP (and, like most electric cars, you can charge the batteries from it). Batteries allow you to harness that energy and deal well with the fluctuating power requirements of a typical drive, you want huge bursts of power followed by a relatively modest power consumption once at cruising speed. That's why you could get away with something like a 100HP generator instead of a 400HP diesel engine, you can run that generator flat out at 100HP the entire time it's running charging batteries, and then, during cruise, which might only take 50HP, the batteries gain a charge. Taking off from a stop, which could be 1000HP, you can use the extra energy stored in the batteries. It's really about finding the right balance, how big a genny to get "unlimited range" without being too big (using too much fuel). How big a battery to provide enough juice for the peak loads and hold enough generated electric to be usable. Too much battery is wasteful, too much genny is wasteful, and too little of each, well.. Eventually you come to a stop (or only have 100HP to start your rig rolling, good luck with that!).

[SolarPoweredRV]

Without batteries, yes, you'd need a big generator. But the reason diesel-electric is so interesting is because you can store that electric (in a battery pack) so that the peak loads (starting from a stop, for example) can be serviced at 1000HP using the batteries, and then, during cruise operations, when you maybe need 100HP to keep rolling, the generator can charge the batteries. Driving is very variable on demand, going up a huge hill with a massive load, might take every HP the engine can put out, however, going downhill on the other side, instead of 450HP, you actually are a negative HP (and, like most electric cars, you can charge the batteries from it). Batteries allow you to harness that energy and deal well with the fluctuating power requirements of a typical drive, you want huge bursts of power followed by a relatively modest power consumption once at cruising speed. That's why you could get away with something like a 100HP generator instead of a 400HP diesel engine, you can run that generator flat out at 100HP the entire time it's running charging batteries, and then, during cruise, which might only take 50HP, the batteries gain a charge. Taking off from a stop, which could be 1000HP, you can use the extra energy stored in the batteries. It's really about finding the right balance, how big a genny to get "unlimited range" without being too big (using too much fuel). How big a battery to provide enough juice for the peak loads and hold enough generated electric to be usable. Too much battery is wasteful, too much genny is wasteful, and too little of each, well.. Eventually you come to a stop (or only have 100HP to start your rig rolling, good luck with that!).

Good Analysis. This is the method behind the Chevy Volt, it is 100% Electric Drive with the ICE (engine) powering a Generator that is capable of producing slightly more than 100% of the electricity required to propel the vehicle after the energy in the battery has reached 0% (not counting any reserve designed into the Battery Pack to protect the Battery's health). This is different from the Toyota Prius which combines both the ICE and Battery power to propel the vehicle down the road.

To make this system even better you could make it a Plug-in Hybrid with a significant All-Electric Range.

[Overtaxed]

Good Analysis. This is the method behind the Chevy Volt, it is 100% Electric Drive with the ICE (engine) powering a Generator that is capable of producing slightly more than 100% of the electricity required to propel the vehicle after the energy in the battery has reached 0% (not counting any reserve designed into the Battery Pack to protect the Battery's health). This is different from the Toyota Prius which combines both the ICE and Battery power to propel the vehicle down the road.

To make this system even better you could make it a Plug-in Hybrid with a significant All-Electric Range.

Totally agree. That way you can use batteries a lot of the time, charge at home, short trips, etc and probably never touch the generator at all. But when your towing heavy, or driving a long distance you don't have to try to to jam 100s of KWH into a battery in a "fuel stop", you can drop 1000's of KWH of diesel fuel in 5 mins at any truck stop in the country. Charging 100's of KW's worth of batteries is a major, major problem, one that I don't see any reasonable solution to in the short-medium term. Onboard generators solve that problem and we could have an "electric semi" or "electric F450" tomorrow without inventing entirely new ways to distribute power or building a nuclear reactor next every large truck stop to keep up with the electric requirements of "fueling" 100's of semis per hour.