3 ms·
Why ever vary the speed? At this point, most of the parts of an EV are quite mature, and the overall system is a lot more straightforward than a conventional I
by amluto 5y ago
Why ever vary the speed?
At this point, most of the parts of an EV are quite mature, and the overall system is a lot more straightforward than a conventional ICE car. A rear motor (or pair) can drive the real wheels without a transaxle or multi-speed transmission. Traction control can be achieved by rapidly adjusting torque. Regenerative breaking massively increases brake lifetime and reduces particulate emissions. 4WD is relatively inexpensive and increases efficiency (because the front and rear motors can be optimized for different operating regimes, and one can be turned off whole cruising). An electric A/C compressor can operate at the optimal speed for the A/C without regard for driving conditions. A small battery pack that can produce plenty of power for bursts of acceleration under anything except racing conditions is essentially a commodity.
So I think a series electric car with a 150kW (not kWh, and only supplying 150kW in brief bursts) and a small, highly efficient 30-40kW gasoline engine would be fantastic. And that engine would not need to have low efficiency and high emissions while warming up at low speed — when it turns on, it could immediately run at its optimal operating point even if the car is stuck in traffic.
Heck, a manufacturer could sell the engine as an optional feature — many customers could simply skip the engine and drive the car as a short-range EV.
- PeterisP 5y agoIIRC that's how many diesel locomotives work, using electric transmission (generator+motor) instead of mechanical coupling.
- a9h74j 5y agoAt selected RPM notches with accompanying max power levels, the RPM values chosen to avoid any nasty resonances.
- redwall_hp 5y agoThat's also how hybrid supercars and the current batch of Formula 1 cars work. For nearly a decade now, F1 cars have been turbocharged engines running electric motors, putting down something like 800-1000hp in the process and running an entire race on one small tank of fuel. I think they're down to 1.6L V6 now. The Chevrolet Volt used a similar principle as well, as opposed to the Prius and its more complicated mechanical duel-drive train.
- manigandham 5y agoThat's incorrect. F1 cars are primarily driven by their piston engines. They have a real transmission that drives the wheels from the driveshaft. Electric motors assist with power delivery from energy captured from kinetic motion, heat and exhaust pressure. This is different from pure electric drivetrains like diesel-electric locomotives where the fuel is only used to generate electricity and all of the propulsion is by electric motors.
- nradov 5y agoThe Chevrolet Volt has a direct mechanical coupling from the internal combustion engine to the transmission for efficiency. If doesn't really operate as a series hybrid much of the time.
- akira2501 5y agoThe highest driving range for the longest range Tesla is 402 miles on a full charged 100kWh battery pack. This is 4.02 miles per kWh. A 30kW generator will produce 30kWh in an hour, which is enough energy to drive 120 miles and well above any average travel speed required. In ideal conditions a 20kW generator would be enough to drive with a completely depleted battery at highway speeds, and a 10kW generator would be enough to significantly extend your range. Which might be necessary.. a 30kW generator running at fult tilt while sitting at a stop light might be a rather unusual experience. Also looking at commercial extended duty 30kW generators makes me wonder where you're going to put that on an already 4,000lb car.
- amluto 5y agoIf I’m buying a series hybrid with a small battery, I would like the ability to tow small loads, drive with the windows open, drive faster than Tesla’s rated speed, drive on wet or snowy roads, etc. Some margin for error would be welcome.
- manigandham 5y agoExactly. Modern piston engines are great for dynamic loads but very inefficient because of it. Using engines to generate electricity in a single optimized configuration can greatly increase efficiency while benefiting from all the advantages of electric drivetrains. They can also be made modular to power everything from cars to boats to machinery. This setup is already used in diesel-electric locomotives and submarines but hasn't really been applied to other transport systems for various reasons. It's something I've been working on as a side project although maybe it's time to launch it as a startup.