All the more reason using forest products waste and a perennial grass that is native to the american plains for feedstock makes a lot of sense. I also recall that there was a diesel product easily made from methanol.
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The flux capacitor was impressive, but maybe not as impressive as Doc Brown’s invention of a tiny nuclear reactor that can somehow efficiently and instantly convert plutonium directly into electricity without generating any radioactive waste.
(Or, come to think of it, maybe it generates lots of highly radioactive waste with a long half-life but the time machine uses its time-travelling powers to quickly age it into a safe form?)
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Cellulase turns cell walls back into glucose.
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Not even vaguely similar to Wankel. Uses conventional reciprocating pistons on a rocking arm to drive a conventional con rod and crank.
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Supercapacitors could be also used for buffering - I think that it would provide greater efficiency and longer lifespan.
How does the energy efficiency of a hydrogen-fueled internal combustion engine compare to that of a hydrogen fuel cell vehicle?
Doc Brown’s time machine produced huge quantities of nuclear waste, but he dealt with the problem the same way as everyone else: leave it to future generations to worry about. (Literally—he’d just make a quick stop around 2045 every so often and dump the spent rods on the side of a road somewhere.)
Here are two really hard to compare sources, but they are at least the same general van with two different engine options, and generally to me this says to me that your answer is, more or less: since 2003 when it was about even, a lot better now.
https://www.hydrogen.energy.gov/pdfs/progress06/vi_a_1_bonhoff.pdf
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I fail to be impressed. The engine I have in my present car is one of the modern “downsized” high economy engines. It is supposed to have about 20% less friction than the previous generation, all with classical technology. So a rube goldberg design giving unproven 30% gains fails to impress me.
BTW: I read about the development of the engine in my car. It took about 5 years to develop it. Increasing fuel efficiency is only part of the work, there are various further optimisations: maintenance (oil contamination), noise levels, heat (insuring optimal work temperature is quickly gained is very important for typical use), pollution, etc…
I am taking my car as an example, because it is the car I have. I know that about every major manufacturer did about the same in the past years (at least in Europe and Asia). BTW: the new car indeed uses about 18-20% less fuel than the old one and the old one was already quite fuel efficient for the time. I use 6l per 100 km (about 40 mpg US), which is a bit better than average for that particular model (small European 4-5 seater). Please note that EU fuel is a bit better than US fuel, the same engine would use about 5% more on US fuel.
I don’t intend to prove that my car is particularly good, whatever. I just want to give a reference point for what can be had today with technology already on the market.
Hey, that’s pretty cool - four cycles in three combustion chambers!
It has the same problem that wankels and other rotaries have - it’s very challenging to seal off the “live” combustion chamber from the adjacent chambers - but it looks better than the Wankel in this regard, because of the rotor shape.
Anyway, thanks for the link, I hadn’t heard of Liquid Piston before. Their design might actually be applicable to chainsaws and that would be a Wonderful Thing®
Compressed Air propulsion for a moving vehicle is frankly terrifying. In an accident that air tank is a bomb. Even in cases of poor maintenance or slight manufacturing defect that tank is a bomb. Everyone knows that in real life cars don’t explode like they do in Michael Bay films, but with a compressed air car of non-negligible range they would (minus the fireball).
Ask a dive shop owner why he fills air tanks under water, or look up old Steam Boiler/Steam Locomotive explosions (same principle) for examples of what happens when a pressure vessel fails.
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That was true a few years ago, but even the dirtiest states are still net positive The worst average region is northern Wisconsin at 38 mpg equivalent. So maybe if you’re in rural Wisconsin or the UP you could make that case but even there the decarbonization is happening due to simple rolling upgrades and that gap will likely be gone within a decade.
Thank/fuck you for posting that link! (disclaimer was fair, but also juicy bait.) My favorite part of it is how the website itself looks like ancient web technology!
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That’s the most important point! If you buy an EV today, the power will be cleaned up well before your EV wears out - even if you are in the dirtiest power parts of Tennessee, Georgia or Kentucky - just due to market forces.
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Perfectly valid drawbacks. I would only point out that internal combustion itself is only on the order of 10-20% efficient. The lion’s share of heat generated by IC generally requires making internal parts of alloys and of much more mass than they would otherwise need to be, and the addition of an integral cooling subsystem. Each propellant demands its own concessions, we’ve just institutionalized the IC ones. 
The one place I’ve heard of air powered cars being used is in India, where the cold air is routed into the cabin as a form of air conditioning. They’re vehicles made extremely cheaply for lower caste people and I have no doubt that some families have been shredded by flying tank debris.
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