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Comment by ars | Hacker News Reader

Yes, capture energy there.

But don't make electricity, make hydrocarbons using the https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_proces...

Ship water and coal, and return with mixed hydrocarbons, then distribute them all over the world. You thermalize (rather than electrolyze) the water to get hydrogen, then react it with the carbon from the coal.

Build a large pipeline to the nearest port to transport the material rather than trucking it.

The leftover oxygen can be sold, or more likely just released.

Since hydrogen releases much more energy (per atom) than carbon when burned, and since since hydrogen outnumbers the carbon in the final product, this will greatly reduce CO2 emissions, even though it's not completely zero.

Capturing heat from the sun is much easier and cheaper than electricity.

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Forget the coal, make methanol from water and co2.

What ars is saying that he wants to take the complex and partially-saturated hydrocarbons in coal and turn them into a hydrogen-satured hydrocarbon. (Most coal has a lot of double-bonds and loops within the carbon, in addition to a hydroxyl groups.) Since energy is released every time you break a bond, you'll have more bonds to break in the end product, but with the same amount of carbon, so you're keeping emissions constant while adding energy.

Regardless, it would be interesting to start with CO2 rather than coal. But can it be sucked up from the atmosphere efficiently and in mass quantities?

Well, trees have been doing it for a long time. Where do you think the carbon in the trees comes from? :)

Trees do lots of cool things that we don't know how to do. That's true of biological life in general. Heck, the lightest insulation for outdoor clothing is still feathers.

Aerogel is lighter than feathers and more insulating. There was a kickstarter this year for a jacket using aerogel as an insulator.

http://www.orosapparel.com/pages/technology

True. It's pretty exciting tech, although apparently it's not very comfortable or easy to work into clothing and gear. It seems pretty promising for very extreme conditions though, like climbing Everest.

Yeah, trees are annoyingly good at absorbing CO2 from the atmosphere. They have the benefits:

1. CO2 dissolves into their fluids

2. The CO2 is almost immediately next to the places that is going to use it

3. Since the Calvin Cycle is distributed, they don't have to collect and concentrate the CO2

4. A lot of surface area on the cellular level to absorb CO2.

I'm reading http://www.scientificamerican.com/article/prospects-for-dire... and it's unfortunate that "Each machine would require roughly 1.1 megajoule of electricity for pumping and compressing per kilogram of CO2 captured."

Trees have the advantage of lots and lots of them. But each individual one is not very efficient.

Making a power plant as large as a small forest is just unrealistic, and would not come close to being powerful enough.

That's why I suggested carbon from coal instead of CO2 - it's just not practical to get it from air.

All we really have to do is reduce CO2 emissions, it's not necessary to eliminate them.

> from water and co2.

It's not easy to get co2 in bulk, and methanol has no advantages over methane (for this process). You need the exact same amount of carbon.

This can't possibly be cost effective or profitable?

OP's point (I'm guessing) is that transmission is the problem with remote generation like this. Production of liquid fuels would probably be better than the enormous cost of building transmission capacity and the associated VAR and resistive losses.

Do you really think it's more expensive, in terms of energy to transport electrons over a wire than liquids over the surface of the earth? I find that hard to believe. Mind you, I haven't done the math.

I think OP's point is more about storage than transmission. Yes you can transport electrons over a wire, but that has a cost and then you have a limited reachability. With liquid on the other hand, you can store in massive tanks and transport anywhere in the world to produce energy locally.

Bulk transport over the ocean is extremely cheap, so much so that oil speculators are paying ships to idle in anticipation of price rise.

Electrical transmission will lose you anywhere from 1%-1.5% per 100 miles depending on the voltage you step up to. Transmitting from the Sahara to the places where the load is gets you to rather large resistive losses.

Also, there are generation losses. A traditional heliostat boiler + turbine will get you about 15-20% effficiency. then you have to shunt the waste heat somewhere in a place with very little fresh water. Oops. PV doesn't get you much better, with about 18% efficiency, but you do solve the need for coolant, at the cost of another problem: Sahara dust on your panels.

The OP talks about using the thermal output from heliostats directly, which would probably (like you, I haven't done the math) be more efficient in fuels production than 15-20%, although you do have the coolant problem again.

One of us should do the math :) Until then, my intuition is that liquid fuels production from such a remote location would probably be more efficient.

It's for sure more efficient. Just think about the power density of even a small gas pipeline - it utterly dwarfs any electrical line, and they are much cheaper to build.

People in Australia are considering a commercial plan to build a solar power to liquid hydrogen plant, possibly converting the hydrogen to LNG or ammonia, and then shipping it to Japan.

http://mobile.abc.net.au/news/2015-11-12/renewable-hydrogen-...

The mere fact that LNG (liquid natural gas, at -180 degrees Celsius) is already being shipped across the worlds oceans today, supports the notion you are questioning.

Um, that's just a fancier way of burning coal.

No it's not. The majority (by far) of the energy comes from thermalizing the water. The hydrogen-oxygen bond is much stronger than the carbon-oxygen bond and there are many more hydrogen atoms in the final fuel.

Ok, it's a more efficient way of burning coal. You're still CO2-emmision positive.

> You're still CO2-emmision positive.

And so what? I said that, did you not read what I wrote?

I'll quote it for you: "this will greatly reduce CO2 emissions, even though it's not completely zero."

> more efficient

That is way underestimating it, it's a fraction of the CO2 output of any other fuel. By far most of the energy comes from the sun, only a small amount comes from the coal. And it's pollution free since all the heavy metals in coal are captured at the source.

It also fits in well with existing technology since there don't exist any other ways of transporting fuel in bulk except hydrocarbons. There simply doesn't exist any other way of doing it.

Have you ever heard the saying "The perfect is the enemy of the good?"

Trying to be eliminate CO2 entirely is impossible, if you hold out for that you'll do nothing whatsoever.

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