Smart Car of America Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
292 Posts
It is stuff like this that proves that marketing and PR departments of major companies are filled with people who can't do a back of the envelope calculation and/or who have moral turpitude for a backbone.
 

·
Registered
Joined
·
4,575 Posts
The devil is in the details but if the feedstocks are biologically sourced and therefore part of the natural carbon cycle, it's potentially a good thing. It's mineral-sourced carbon that is the problem.
 

·
Registered
Joined
·
292 Posts
Explain what you mean, please?
Lets ignore for the moment the complexity of the chemistry and engineering involved in this magical fuel plant. We know its going to be *hard* because if it were easy, someone would already have done it to beat the big oil companies at their game.

I'm somewhat familiar with the complexities of the oil industry because my sister in law is a petroleum geologist. There's a lot of effort, energy and complexity that goes into getting you a gallon of gas. If there was a cheaper and easier way to make gasoline you can be pretty sure they would be doing it already.

Heck, during WWII the Germans expended a lot of effort and dead soldiers trying to get at the soviet oil fields because synthesizing their own diesel wasn't very efficient even when they didn't care about being green.

Lets look at some of the basics.

Bosch is proposing to use elemental hydrogen, generated from water, and purified CO2 for feed stocks. Then they are going to combine them to make hydrocarbons to burn in some kind of, lets call it "normal", internal combustion engine. Could be ICE, could be diesel, maybe something like natural gas. In general, the same kind of engines we've been using for a long time. All of which have roughly the same level of efficiency (approximately 20%). The very best Formula one engines sometimes get as high as ~47% under ideal conditions. Maybe those new Mazda engines are somewhere in between.

Basically making some kind of gasoline-like product from CO2 and water. Which are, wait for it, the primary exhaust products of *burning* gasoline.

Reversing that process is pretty expensive from an energy perspective. Sort of like putting the genie back in the bottle. Not only do you have to put the 20% of the energy you used to push your car, but you have to put MORE than the the other 80% as well.

This is basic college level thermodynamics. You always lose on any energy transformation.

Lets be generous about the magical chemical factory and say it takes only 20% more than reversing the output energy efficiencies. That's crazy optimistic, but good enough for a back of the envelope calculation.

So roughly 6 times the motive energy you get from your car. A generous 16% efficiency

Now start to add in the inefficiencies and energy costs of getting the CO2 feed stock, electrolysis to produce the hydrogen, thermal losses in running the necessary chemical plant. With a little thought I'm sure you can come up with more places where you're losing energy and adding complexity.

Now, compare that to taking the renewable energy they're going to power this complex chemical plant and put it in a battery, and use that battery to power an electric motor. Both of those stages are close to 90% efficient. For a net efficiency of 75-80%. Versus 16% for the magic chemical plant.

Its a lot like the stupidity of hydrogen as an energy storage mechanism, only much worse. At least with the hydrogen you're only paying for splitting the H2 out of the water and then compressing it down for storage. Which is a generous 25% efficient. There's no CO2 processing and other unknowns from the magical chemical plant pulling that number down.

The basic physics is in favour of BEVs. Someone can argue about it, but they're just as likely to be right as they are to prove that the earth is flat.
 
1 - 7 of 7 Posts
Top