5 ms·

Much less efficient than solar panels.

gus_massa 4y ago
I guess you are comparing the efficiency of solar panels (20%) with the efficiency of photosynthesis (1%-2%). The problem is that solar panels have a 20% producing electricity, but using that electricity to make fuel has a very low efficiency. From the article: > When air was bubbled through potassium hydroxide dissolved in ethylene glycol and the CO2-loaded solution subsequently hydrogenated in the presence of H2 and a metal catalyst, complete conversion to methanol was observed at 140 °C. Even with catalyst, organic reactions have an awful efficiency. In many of them the reactives produce not only what you want but also other molecules. In this case it's hard to imagine, because methane is very small and all side products I imagine like COH2 can probably be converted to methane inside a hot recipient full of H2. Anyway, even if you lose no CO2 as side products, the reaction may lose a lot of energy as heat. Photosynthesis has many intermediate steps that help the conversion to be more efficient (and also because photosynthesis builds a bigger molecule that is harder).
- Schroedingersat 4y ago
  The photosynthesis isn't the end of the biofuel equation. Corn ethanol is energy negative (switchgrass, sugar cane or beets are better but still abysmal). If you consider a hybrid PV-CSP plant, the H2 step can be done at 20% from air. CO2 capture is under 10%. So you'd need to show that the ethylene step is under 5% efficient when you also had an available free low quality steam input (or high quality at 50% sunlight-efficiency).
  - gus_massa 4y ago
    I almost agree. From https://en.wikipedia.org/wiki/Sugarcane#Ethanol https://en.wikipedia.org/wiki/Sugarcane#Ethanol > One hectare of sugar cane yields 4,000 litres of ethanol per year (without any additional energy input, because the bagasse produced exceeds the amount needed to distill the final product). This, however, does not include the energy used in tilling, transportation, and so on. Thus, the solar energy-to-ethanol conversion efficiency is 0.13%. but I'm still pessimistic about the efficiency of the new method.
    - Schroedingersat 4y ago
      The thing that will kill as an energy storage method it is capital and labour expenses more than efficiency. I'd expect something like it to be viable for chemical feedstock once the fossil fuel subsidies start to die out and less investment goes into extracting more and worse sources cheaply though.
    - deleted 4y ago
      [deleted]
- konschubert 4y ago
  Let me add another pair of goalposts here: Solar can be done without water
elevaet 4y ago
Much less efficient at producing watts perhaps, but less efficient at producing liquid, transportable hydrocarbons? I doubt it.

I guess you are comparing the efficiency of solar panels (20%) with the efficiency of photosynthesis (1%-2%). The problem is that solar panels have a 20% producing electricity, but using that electricity to make fuel has a very low efficiency. From the article: > When air was bubbled through potassium hydroxide dissolved in ethylene glycol and the CO2-loaded solution subsequently hydrogenated in the presence of H2 and a metal catalyst, complete conversion to methanol was observed at 140 °C. Even with catalyst, organic reactions have an awful efficiency. In many of them the reactives produce not only what you want but also other molecules. In this case it's hard to imagine, because methane is very small and all side products I imagine like COH2 can probably be converted to methane inside a hot recipient full of H2. Anyway, even if you lose no CO2 as side products, the reaction may lose a lot of energy as heat. Photosynthesis has many intermediate steps that help the conversion to be more efficient (and also because photosynthesis builds a bigger molecule that is harder).

Schroedingersat 4y ago
The photosynthesis isn't the end of the biofuel equation. Corn ethanol is energy negative (switchgrass, sugar cane or beets are better but still abysmal). If you consider a hybrid PV-CSP plant, the H2 step can be done at 20% from air. CO2 capture is under 10%. So you'd need to show that the ethylene step is under 5% efficient when you also had an available free low quality steam input (or high quality at 50% sunlight-efficiency).
- gus_massa 4y ago
  I almost agree. From https://en.wikipedia.org/wiki/Sugarcane#Ethanol https://en.wikipedia.org/wiki/Sugarcane#Ethanol > One hectare of sugar cane yields 4,000 litres of ethanol per year (without any additional energy input, because the bagasse produced exceeds the amount needed to distill the final product). This, however, does not include the energy used in tilling, transportation, and so on. Thus, the solar energy-to-ethanol conversion efficiency is 0.13%. but I'm still pessimistic about the efficiency of the new method.
  - Schroedingersat 4y ago
    The thing that will kill as an energy storage method it is capital and labour expenses more than efficiency. I'd expect something like it to be viable for chemical feedstock once the fossil fuel subsidies start to die out and less investment goes into extracting more and worse sources cheaply though.
  - deleted 4y ago
    [deleted]
konschubert 4y ago
Let me add another pair of goalposts here: Solar can be done without water

elevaet 4y ago

Much less efficient at producing watts perhaps, but less efficient at producing liquid, transportable hydrocarbons? I doubt it.