from Hacker News

Terraformer Mark One – cheap natural gas from sunlight and air

by epaulson on 6/26/23, 8:43 PM with 10 comments

• by civilitty on 6/26/23, 11:54 PM

  Back of the napkin math: 0.055 metric tons of CO2 per Mcf * 2,300 Mcf/year = 126 metric tons of CO2 per year - that much checks out.

  It lists 1 MW power input so ~8,760 MWh at 100% utilization. According to [1] it's .44 metric tons of CO2 per MWh, or 3,850 metric tons of CO2 per year if the Terraformer Mk 1 is powered by natural gas. 126/3850 = ~3.2% round trip efficiency - that much also checks out so this doesn't seem like a perpetual motion style scam. Even if those stats are only for 20% utilization with solar, that's still a realistic(-ish) round trip efficiency of 15%. I can't tell what kind of utilization the infographic actually assumes ("between 0.2 and 1"...) and it mixes metric, imperial, annual, daily, and instantaneous units!

  The big problem is that the opportunity cost of not using that 1MW of solar to displace dirty energy elsewhere is huge. It's just wildly uneconomical without free surplus renewable energy and possibly CO2 reduction incentives like a carbon tax.

  [1] https://www.eia.gov/tools/faqs/faq.php?id=74&t=11

• by ozb on 6/27/23, 2:35 AM

  So roughly $100k/(5*120 tons CO2) + 2 million kWh/(5*120 ton CO2) --> 5*2300 Mcf

  Ie $167 + 3333 kWh will turn 1 ton CO2 into 19 Mcf

  At $0.10/kWh, this is equivalent to paying $500 to remove 1 ton of CO2 from the atmosphere. This goes down to $300 if we assume solar can generate power at $0.04/kWh, particularly off-grid and without need for storage.

  And it apparently turns out that the Inflation Reduction Act subsidizes the synthetic natural gas at $54/Mcf, so if we sell about 4.7 Mcf at $64 we've effectively gotten the government to pay $250 to remove 0.8 tons from the atmosphere.

  This sounds interesting, as a first step.

• by rotexo on 6/26/23, 11:29 PM

  Quick google indicates that a 1MW solar array yields around $40k revenue per year [1]. (I might be misinterpreting that, and also might not be the best source, but multiple hits gave the same ballpark.) With that route, you don’t pay up-front for the electrolyzers, DAC plant, and Sabatier reactor (cost unknown to me for all those components). Maybe add some batteries (Li-ion? Flow?) and you can probably increase annual revenue a fair bit (again, I don’t know how the initial outlay would compare between the terraformer and solar-plus-batteries). I know the two options aren’t totally comparable, because you get an easily transportable fuel with the terraformer. Still, my intuition is that just from the economics, this might be slow to take off. (then again, I know almost nothing!)

  [1] https://www.solarreviews.com/blog/what-is-a-solar-farm-do-i-....

• by tarmol on 6/27/23, 10:59 AM

  I have been thinking along the same lines (same process for CO2 capture and natural gas as output). The thing that kills it is energy requirements, in this scenario 1 MW of solar panels would cost about 1 million USD + 100k USD for the plant. In theory it could be profitable within 7-8 years - possibly sooner if built in Africa or some other country with infinite solar (just napkin math).

  Another thing that might make it more profitable is extra conversion to SAF (Sustainable Aviation Fuel).

  Long term in this type of tech is crucial to stop burning up carbon stored in the ground for use cases that require more energy density (like flight).

• by NoZZz on 6/28/23, 6:32 AM

  Fischer-Tropsch reactor?