Making gasoline from seawater (to store energy)

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Discussion Overview

The discussion revolves around the feasibility and implications of producing gasoline from seawater, specifically through a process that extracts carbon dioxide and hydrogen. The conversation touches on the technology's potential applications, energy efficiency, and economic viability, as well as comparisons to existing methods like Fischer-Tropsch synthesis.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants highlight the proof-of-concept demonstrated by the U.S. Naval Research Laboratory, which claims to convert seawater into gasoline using an electrolytic process.
  • Others express skepticism regarding the economic feasibility, questioning whether the projected cost of $3 to $6 per gallon is realistic given the current state of technology.
  • A participant mentions the Fischer-Tropsch synthesis as a related process for producing hydrocarbons from CO2 and H2, suggesting parallels to the seawater gasoline production method.
  • Concerns are raised about the net energy return of the process, with some participants questioning if it consumes more energy than it produces.
  • Some suggest that using nuclear power or solar energy could provide the necessary energy for the process, while others note the variability of energy sources from the grid.
  • A participant proposes that if the process can effectively store energy rather than produce it, it could address significant energy storage challenges without disrupting existing oil infrastructure.
  • There are mentions of ongoing research into alternative methods, such as algae fuel and synthetic bacteria, which may offer similar benefits.

Areas of Agreement / Disagreement

Participants express a mix of interest and skepticism regarding the technology's viability. While some see potential benefits, particularly in energy storage, others remain doubtful about the economic and energy efficiency aspects. No consensus is reached on the feasibility or practicality of the proposed methods.

Contextual Notes

Participants note the importance of considering energy sources and efficiency in evaluating the proposed gasoline production method. There are references to historical energy return ratios in oil production, indicating that assumptions about energy inputs and outputs are critical to the discussion.

  • #31
Reverse osmosis is much less energy consuming than electrolysis so you are probably right. What scrubbing process would be used? I don't know a lot about that sort of Chemistry.
 
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  • #32
mheslep said:
Do they? AFAIK subs recycle, i.e. they purify their grey water and scrub CO2 out of the air.

You run a steam plant, you want to have a water-maker somewhere aboard. Even the old diesel-driven fleet boats from WWII had water-makers aboard, not for making potable water so much but for maintaining the acid in the batteries used to drive the vessel while submerged.

http://www.fleetsubmarine.com/fresh_water.html

The regulations governing the discharge of greywater from USN vessels are currently evolving, with the goal being to minimize the amount of solid waste and untreated liquid waste which is discharged during operation, but that doesn't necessarily mean that the grey water is re-cycled back into the potable water or feed water systems.

Most shipboard water-makers are of the 'flash' type, where seawater is fed into a low-pressure chamber, in which the water flashes into vapor, leaving a concentrated brine behind. The brine is dumped and the flashed vapor is condensed back to liquid water, without the salt.
 
  • #33
Astronuc said:
...
Liquid fuels are simply a medium in which chemical energy is stored.

Interesting. :wink:
 
  • #34
seawater is a natural electrolyte and sunshine a natural source of power
 
  • #35
BigWill said:
seawater is a natural electrolyte and sunshine a natural source of power

Does the adjective "natural" make it an engineering proposition? Its only advantage is that it's cheap to obtain (if you happen to live near the coast).
 
  • #36
Thanks for that. You may want to debate sustainable / renewable / naturally non toxic unless you want to poison your pH by drinking saltwater all day long...but the balance of seawater covering 4/5ths of the planet mean depth of around 3000m, make water accessible to the majority as the solar wind turns it into rain. This may change rapidly as the water companies inflate charges and organise for drought with pollutive atmospheric changes.
 

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