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Jollo
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Note to mods: this is my first post, unsure about the best forum for this query. Please feel free to move if necessary. Thanks.
I have this wild notion that one possible way to “quickly” replace fossil fuels is methanol. Methanol is the simplest alcohol (CH3OH), liquid and stable at room temperature, and can be burned in existing internal combustion engines with a few modifications. It can also be transported and distributed with the existing transport infrastructure used for petroleum derivatives (pipelines, supertankers... down to the local gas station). So, unlike with hydrogen, you can switch to a methanol-based economy with moderate infrastructure changes.
Methanol can be produced out of CO2, water and sunlight: basically, you electrolyze water using power generated by a solar panel (2 H2O → O2 + 2 H2), discard O2 in the atmosphere, put H2 in a reactor with CO2 (needs a cheap metallic catalyzer, plus some heat and pressure also powered by the solar panel) et voilà: CO2 + 3 H2 → CH3OH + H2O. Recycle H2O into the process (thus lowering H2O demand by 33%) and collect methanol, ready for transportation and usage (no further refinement is necessary). The problem is: where do you take CO2 from? In today’s industrial base, from petroleum processing (driving the false impression that methanol itself is a petroleum derivative). In principle, it could also be captured directly out of the atmosphere.
Burning methanol and air (e.g. in an internal combustion engine) will create CO2 (2 CH3OH + 3 O2 → 2 CO2 + 4 H2O), but if methanol is produced capturing CO2 from the atmosphere the production-combustion cycle is carbon-neutral. Also, combustion leaves no nasty pollutant by-products (aerosols, NOx, aromatic hydrocarbons, etc..).
Methanol does has a few problems to be worked around: it is corrosive for aluminum and a few other metals, so a few components along the whole cycle might have to be re-designed accordingly. Methanol’s specific energy (circa 20 MJ/kg) is less than half than gasoline's (up to 47 MJ/kg), but packing a little less punch in your car engine will not kill anyone (in your aircraft engine that might be a little more worrisome... but I'm confident ways around can be found). It is toxic if ingested, but not more than gasoline. On the other hand, unlike gasoline and petroleum, it is quickly bio-degradable (7 days half-life in water).
The problem is that typical atmospheric CO2 concentrations (around 390 ppm by volume) would make for very low production yields, but efficiency issues and a “weak” energy source (such as a solar panel) would cap process yields to very low values anyway.
So this is how I imagine this could work on a large scale: litter a desert with small, autonomous sunlight-powered processors with a water tank (initially full), a methanol tank (initially empty) and lots of time and sunshine to perform the conversion. A fleet of robotic, automated collectors could do the “milk runs”, collecting methanol and refilling water tanks, visiting every individual processor perhaps every few months (and replacing broken down or ageing processors for refurbishment while they’re on the spot). Or imagine an ocean littered by small, autonomous floating processors (no need for the water tank, but you’d have to figure out displacement) and robotic collector ships doing the rounds.
Now for a few disclaimers:
Now for a little amplification: methanol is liquid and stable at room temperature, much of the existing petroleum-based transport infrastructure could be adapteded with moderate change, it has a decent specific energy and can be produced and burned in a carbon-neutral cycle. It looks like a promising candidate on all counts.
I am therefore asking some expert opinions about this scenario, especially about the economics, and about possible alternatives that would fit the bill. Thanks in advance.
Jollo
I have this wild notion that one possible way to “quickly” replace fossil fuels is methanol. Methanol is the simplest alcohol (CH3OH), liquid and stable at room temperature, and can be burned in existing internal combustion engines with a few modifications. It can also be transported and distributed with the existing transport infrastructure used for petroleum derivatives (pipelines, supertankers... down to the local gas station). So, unlike with hydrogen, you can switch to a methanol-based economy with moderate infrastructure changes.
Methanol can be produced out of CO2, water and sunlight: basically, you electrolyze water using power generated by a solar panel (2 H2O → O2 + 2 H2), discard O2 in the atmosphere, put H2 in a reactor with CO2 (needs a cheap metallic catalyzer, plus some heat and pressure also powered by the solar panel) et voilà: CO2 + 3 H2 → CH3OH + H2O. Recycle H2O into the process (thus lowering H2O demand by 33%) and collect methanol, ready for transportation and usage (no further refinement is necessary). The problem is: where do you take CO2 from? In today’s industrial base, from petroleum processing (driving the false impression that methanol itself is a petroleum derivative). In principle, it could also be captured directly out of the atmosphere.
Burning methanol and air (e.g. in an internal combustion engine) will create CO2 (2 CH3OH + 3 O2 → 2 CO2 + 4 H2O), but if methanol is produced capturing CO2 from the atmosphere the production-combustion cycle is carbon-neutral. Also, combustion leaves no nasty pollutant by-products (aerosols, NOx, aromatic hydrocarbons, etc..).
Methanol does has a few problems to be worked around: it is corrosive for aluminum and a few other metals, so a few components along the whole cycle might have to be re-designed accordingly. Methanol’s specific energy (circa 20 MJ/kg) is less than half than gasoline's (up to 47 MJ/kg), but packing a little less punch in your car engine will not kill anyone (in your aircraft engine that might be a little more worrisome... but I'm confident ways around can be found). It is toxic if ingested, but not more than gasoline. On the other hand, unlike gasoline and petroleum, it is quickly bio-degradable (7 days half-life in water).
The problem is that typical atmospheric CO2 concentrations (around 390 ppm by volume) would make for very low production yields, but efficiency issues and a “weak” energy source (such as a solar panel) would cap process yields to very low values anyway.
So this is how I imagine this could work on a large scale: litter a desert with small, autonomous sunlight-powered processors with a water tank (initially full), a methanol tank (initially empty) and lots of time and sunshine to perform the conversion. A fleet of robotic, automated collectors could do the “milk runs”, collecting methanol and refilling water tanks, visiting every individual processor perhaps every few months (and replacing broken down or ageing processors for refurbishment while they’re on the spot). Or imagine an ocean littered by small, autonomous floating processors (no need for the water tank, but you’d have to figure out displacement) and robotic collector ships doing the rounds.
Now for a few disclaimers:
- I am *not* talking here about energy *generation*, I am talking about energy *storage* and *transport*. I’ll say that again: I am fully aware that the energy balance of the process described above is *negative*. Please don’t go off charging about ignoring the first law of thermodynamics: there’s loads I don’t know, but please believe I’ve got Physics 101 down on pat (I hope).
- I once read (Heinlein, so we’re fully into SF!) that energy is literally “raining soup” (in radiation, wind, temperature gradients, etc.), but never in the right place, time and density to be useful. I happen to agree: what I am looking for here is a method to *store* energy in a medium with:
- decent specific energy
- decent economics
- easy transportation and storage
- easy energy retrieval (e.g. combustion or fuel cells) and
- applicable to low yield energy transformation processes (something like days or months to gather energy and seconds to deliver it where and when needed)
- We already have such a medium, and it works great: it’s called gasoline (or variations thereof, from mazut to JP4); alas we only know how to produce it economically from fossil petroleum, and lots of problems ensue
- Hydrogen would be a great idea (and has about double the specific energy of gasoline), but fails miserably on the #2 and #3 requirements: it’s the most volatile gas in the universe, and it’s horribly expensive to store and transport safely. A couple of orders of magnitude too expensive.
- Chemical batteries are very efficient, but have a very low specific energy (less than 1MJ/kg for the most expensive types). At least an order of magnitude too low for most applications.
Now for a little amplification: methanol is liquid and stable at room temperature, much of the existing petroleum-based transport infrastructure could be adapteded with moderate change, it has a decent specific energy and can be produced and burned in a carbon-neutral cycle. It looks like a promising candidate on all counts.
I am therefore asking some expert opinions about this scenario, especially about the economics, and about possible alternatives that would fit the bill. Thanks in advance.
Jollo
