This has been in the works for a few years.
 

https://global.nissannews.com/en/releases/210226-01-e

A strong hybrid with an engine optimized to run in one power band has always been one of my solutions of choice.

Basically what has been attempted on buses for a while, even in my country.

The ICE part begins at youtu.be/jeUEEfnr5-k?t=1149

It relies on promoting a swirl in the combustion chamber. The spark plugs would need to be clocked correctly.

Don't have time to pay attention to the video at the moment (funny they dub male speakers with female voices).

This appears to be a series hybrid. I'm always confused if the first gen Volt was a series hybrid or not, but I know the BMW i3 with ICE was. Makes all kinds of sense to me, especially if they incorporate ~16 kWh battery that can be plugged in for an initial all electric range of 60 miles.

I'll really get excited when these technologies reach the vehicles most in need of them; larger trucks, SUVs, and vans.

Interesting,

The Epower transmission peaks at about 80% efficient similar to an antique slush box.

By increasing engine efficiency they should be able to overcome the inherent inefficiency of a series hybrid

Nissan has teased the epower coming to the US for 5 years, see if it ever makes it.

Make mine a plug in Note when it comes over (doubtfull any epower ever will and if it does expect it in a landbarge)

Nissan has been selling an e-Power Note in Japan since 2016. This is the same powertrain with a step up in efficiency (if it works outside the lab)

My understanding is that although serial hybrids work well for low speed operation they aren't the most efficient way to transfer power at highway speeds. That is why the Prius, Volt, and pretty much every other hybrids is a series / parallel hybrid to allow the most efficient mode for the travel conditions.

Japan would have ideal conditions for a serial hybrid with their dense cities and low speed limits. (The highest speed limit I saw in my travels to Japan was 80 kph on an urban expressway.)

Energy conversions are inherently inefficient, so improvements in processing any particular energy conversion needs to be extremely efficient to offset the losses from additional conversions.

ICE converts energy from chemical > heat > mechanical.
Throw in series hybrid and the process is chemical > heat > mechanical > electrical > chemical > electrical > mechanical.

The electro-chemical conversions are more efficient than the initial chemical > heat conversions, but they still represent loss of efficiency.

If internal combustion ever got to say 70% efficiency, it would be game over for alternatives. The density of fossil fuels combined with high efficiency conversion would be an insurmountable obstacle. That doesn't appear likely, so we will see EV powertrains begin to displace ICE.

Exactly.


IIRC the Volt could be driven on ICE power when the batteries were low, so it's not a serial hybrid at all.


Wrightspeed has been proposing that approach mostly for trucks and buses. Had it provided a similar driveline for something like a Jeep Wrangler or the compact trucks, maybe there would be a good chance for success in the fleet market.

Ernie Rogers, a former member . . .
 

. . . provided a white paper calculating that the application of the Atkinson Cycle to a diesel engine could yield a tad over 60% thermal efficiency. Use of various materials in construction could pull out a few more percentages. Your 70% efficiency target is not that far off for the intrepid.

A single speed atkinized Diesel could also get away with a much more simplistic emissions system

The gen1 chevy volt was both, but was primarily a series hybrid. Only under very specific situations will the engine drive the wheels directly. Which is why it was only capable of mid to high 40's MPG on the highway whereas a toyota prius could easily do better.

There is a big difference between theoretical values, lab tests, and reality. A combined cycle gas plant is theoretically 95% efficient. The most efficient real combined cycle plant is the GE 7HA that is 63.8% efficient.

(I worked on the 7HA and 9HA programs at my first job out of university)

I won't really hold my breath for that. Just remember most of the emissions non-conformity observed on tests with Diesel vehicles in South Korea back in the Dieselgate days were related to harsh weather conditions (not the same as the deliberate fraud observed in Volkswagens and Audis).

Well understood.
 

Peak thermal efficiencies for Class 8 diesel trucks are already at 48%. Large ocean going diesels are at 52%. A practical application of the Atkinson Cycle to the diesel cycle can push the 60% envelope. Use of ceramic coatings to reduce heat loss ( the main advantage of the large ocean engines due to cylinder size )
plus advanced injector technologies such as the defunct Transonic super critical fuel injection will nudge you within spitting range of 70% thermal efficiency. That's more than good enough to use as a constant load generator in a serial hybrid vehicle.

This is where a single load point makes it much simpler.
 

All engines coupled to drive a vehicle directly must provide variable power. They struggle to provide this variable power and thus fall into inefficient ranges both in thermal efficiencies as well as emissions. A single speed/load makes it so much easier.

As long as the emission controls keep their performance under all the different environmental and weather conditions it may be required to operate.

I'd argue against this, simply by virtue of its transmission layout. It uses a very similar planetary gearset to a Prius. The electric motor is large enough and the gearing chosen such that the gas engine doesn't *need* to oppose the electric motor in order to operate at all normal road speeds, but ultimately it's still planetary gears. Torque into the system = torque out of the system.