Quote:
Originally Posted by Ecky
On the face of it, a linear genset really does seem to be the best of all worlds. My impression is that it's a matter of just implementing it, and the time to develop it. It hasn't been all that long since batteries were commonly big enough to provide all the power needs of a vehicle, and this would best work as a way to recharge those batteries, while the batteries remain responsible for motive power.
That said, I have been reading about Mazda's newest genset, and it gives me pause as to whether automakers will even choose (for mainstream) to pursue high efficiency gensets. Mazda's pitch appears to be that, most driving is local and short-haul, and eventually all vehicles will be hybrids of some sort, and have a battery of some size. Batteries are rapidly falling in price, size and weight. For a passenger vehicle, this essentially means driving on the battery most of the time, with access to a charger every night. The point of a genset (according to Mazda) is not really to provide the energy that is used to move the vehicle on a regular basis, but to extend range in those less frequent cases, such as a road trip, and as such their efficiency is relatively unimportant.
Mazda has chosen to develop a rotary for this. My first impression was "are they insane?", given how inefficient and polluting rotaries are. Their reasons, however: rotaries are compact, lightweight, power dense, and smooth. They take up very little room in the vehicle, and their emissions and efficiency are near irrelevant if they're only being used occasionally. So, rather than a vehicle having a 500 mile battery, give it a 100 mile (or whatever is deemed appropriate) battery and a small rotary genset. The vehicle will do 98% of its driving on the battery, the genset will not cause significant compromises to vehicle packaging, and the driver will not feel any range anxiety. Similar in concept to how GM advertised the Volt, and to how BMW designed the i3 REX.
I have personal interest in efficiency, but Mazda seems to be posing the question, "To what end, and at what cost?". Possibly a linear genset could be more compact, cheaper, and more balanced than even a rotary. But, it does need to be developed.
EDIT: A picture of the size of the MX-30 drivetrain. It is 168hp, and weighs less than a typical gasoline engine alone. Mazda choose to attach a rotary, and to equip it with a 130 mile (209km) battery, which weighs about the same as two full tanks of gasoline. The total drivetrain including the EV battery weighs no more than a conventional engine, transmission and full gas tank.
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Thx Ecky! Mazda is posing some very good questions there! Worth thinking about!
While electricity isnt nearly as clean as we like to believe it is, it's cheap... (ATM!!) and enables regen.
So mazda is saying: "As it's hardly used; make it as light and cheap as possible"
That makes sense from the 98% of driving is city where 68% of fuel is used to accelerate weight.
Better yet might be a 'Stay at home 98% of the time, quick connect genset type engine doodat, that one only 'plugs in' when a longer trip is planned, saving that weight.
The problem there is one can never underestimate the ingenious ways in which idiots manage to uck this sort of thing fup!
The other way to go may be an even smaller than 'required freeway cruise power' sized, always-on engine:
That's lighter, takes lifespan killing amp load of a smaller lighter battery all the time and provides heat for the interior.
That, combined with regen, should work fine in town.
During the normal bathroom/fuel/food stops of a long trip; the engine stays on at it's optimized rpm, charging away, so you don't (normally) run out of battery.
Add the option to also plug it into an EV charger (if there is one) if you like.
Then there's also all that, easy at constant rpm, fuel pyrolysis/ Steam Reformation/ Water Gas Shift reaction stuff one might do.
As the power is more off than on here in The New South Africa; having a genset wherever I am is another big selling point.