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Comment by m_mueller | Hacker News Reader

Something that annoys me with these articles is that such processes are usually praised as carbon capture at the same time as it is energy storage. Well yes, but not both at the same time. And I really doubt its effectiveness as energy storage in the first place - why would you burn fossil fuels (with a loss), then gather energy with renewables to capture back the CO2 (with a loss) and then use the energy of the ethanol again (again with a loss)? Just store the energy from the renewables in batteries.

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Batteries might be more expensive than storing energy in liquid fuels. They have a limited number of charge cycles after all, whereas a vat of Ethanol can be refilled forever. There is also a large number of motors available that can burn Ethanol, but a significantly smaller number of electric vehicles.

1.) electric vehicles are also vastly simpler mechanically, so what you gain with energy storage efficiency in gasoline tanks you loose with their complex motors.

2.) if cheap energy density is the problem they want to solve, then this process at least needs to be compared to using the land to grow plants in order to turn them into ethanol fuel. So a comparison like "wind farm under average conditions + ethanol farming" vs. "wind farm under average conditions + solar under average conditions + CO2 to ethanol process" --> how many Joules of kinetic energy can you produce per square kilometer of land, given the fuel/electricity is used in the currently most efficient motors/batteries?

Many people dislike growing plants for Ethanol production because they compete for arable land that can be used to produce food. Solar and wind farms can be built in places where agriculture is not viable.

well, at the end it's just sunlight, carbon, nitrogen, water, a few minerals and a bunch of chemical reactions. I'm pretty sure you could find a biological process to put anywhere that's also viable for solar farms, including open water. In fact, haven't there been a bunch of papers using algae?

Growing plants for fuel by itself is not a problem. Core issue is that the collective intelligence of us as species does not appear to be higher than yeast.

One idea goes like this: We use nuclear or renewables to power a process to capture extant CO2 to be used as fuel, which turns it back to CO2, which will be recaptures, so run-away processes are reigned in. (I can tell by your comment that you get this.)

Here's the kicker: the energy density of liquid fuels is super-hard to beat. Batteries (and super-capacitors) are getting better, but relatively speaking, on a whole bunch of dimensions, it doesn't get much easier economically, technically or infrastructurally than burning some hydrocarbon. Hopefully sulfur and mercury free.

Tieing "the energy of the future" with "the infrastructure of today" is a very attractive concept that draws a lot of funding from a lot of folks. And researchers, in labs, are working on things that have various limitations of their own, such as "well, gosh, how do you make a copper-iridim-mesh-alloy-hydromister in volume?"

Energy density is great, but for most current usecases I'd argue it's not really necessary. It's neither needed in your home (lots of space to put batteries, is connected to a power line), nor for your daily commute, nor for agriculture, nor for heavy industry (even better power lines), nor for long distance land based transport (trains are just as good and can be electrified easily) which covers the largest energy consumers right there. It is very useful for long distance individual travel by car (so, get a Chevy Volt instead of a Tesla) as well as airplanes, rockets and ocean shipping. If we'd just use the remaining fossil fuel for those purposes it would be pretty easy to be carbon negative.

80/20 rule and all that, I agree. I'm originally from a ranch in Wyoming 65m+ from the nearest grocery store, and those use-cases (ag, distance) are burned into my gut. It makes for some bad intuitive generalized conclusions on this topic from time-to-time.

no sweat, it's a pleasure to communicate with people who are able to think systematically and who can do an actual discussion rather than just shouting from rooftops.

Please, don't mistake me - I'm still opinionated. I just got tired of yelling on the Internet. :-)

On this topic, though, in this context: no need to yell. You make a good point.

I will say that it is devilishly hard. Liquid fuels have some impressive characteristics, that make them an easy "go-to" for almost 100% of our heavy portable-power use-cases, and economic alternatives for those use-cases must almost be developed one-at-a-time. I'm an engineer, not a policy constructivist, so somebody saying "tax it" to bring alternatives to economic parity is vaguely unsatisfying to me.

The economics of it are the main reason why I think batteries are the only way forward we have with current technology. We desperately need a solution that is not only carbon neutral, but cheaper than gasoline power at the same time, using a cost-of-ownership kind of calculation.

If Tesla can deliver on making the required batteries as cheap for the usecases outlined above, it is the most promising way of solving an important part of the very near future crisis of unpaid negative externalities we've been causing in our fossil fuel based economy. Neither fuel cells nor bio fuel (both ways to get back higher energy density) can do this, because both can never beat the economics of fossil fuel when you run the numbers, especially in our post shallow water fracking world.

There is a big caveat however: It won't do any good if we continue to demolish the clean electric energy we got from nuclear and replace it with fossil fuels. Clean energy in total actually slowed down if not reversed because of recent nuclear scares. That includes Germany btw., often cited for their solar/wind efforts, but this was hardly able to replace the nuclear plants they're closing at the same time. This ist the stuff where I'm getting angry at the world... it's like a frog in a slowly boiling pot throwing out his supply of ice cubes because it scared him.

I wonder if it would be useful to harvest excess CO2 from the atmosphere. That way, you're using the existing CO2 as a fuel source.

Am I missing the sarcasm tag?

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