Climate mitigating energy production

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A Lawrence Livermore team has demonstrated that electrolysis of saline water produces not only hydrogen, chlorine and oxygen gases, the resulting electrolyte solution is significantly elevated in hydroxide concentration, which are strongly absorptive and retentive of atmospheric CO2.

 

Figure 1 to the right is a schematic of the process that produces what they refer to as "super green" hydrogen.

 

(A case study of a hypothetical 100 MW OTEC plant analyzing the prospects of OTEC technology by Dr. Subhashish Banerjee et. al (page 125) determined that hydrogen production from a 100 MW OTEC plant would be over 35,000 kg/day. 

 

Every mole of hydrogen produces a mole of sodium that in turn precipitates a mole of CO2. A 100 MW OTEC would therefore produce 12,775,000 kgs of hydrogen a year which would sequesters 562,000 metric tons of CO2 with the super green technique.

 

Full capacity OTEC (14 terawatts) could therefore sequester about 79 billion metric tons/year by 2100 and return atmospheric CO2 concentrations to safe levels.

 

Fourteen terawatts would generate 1.8 trillion kilograms of hydrogen each year, which in turn would be converted to 16 trillion kilograms of water when energy is produced in a hydrogen fuel cell or the hydrogen is burned in some other engine.

 

Since the average height of of land is 840 meters, this water would have the potential to generate 4.3 terawatts of hydro or about 4 times what the world is currently producing.)

 

Hydrogen and oxygen can be combined in a stationary installation at any elevation to produce energy and water and the head between where it is produced and where it is needed can be used either to augment the system's energy output or to facilitate water distribution.

 

Hydrogen is a water as as energy carrier.

 

Compressed hydrogen has the highest energy potential by weight  of non-nuclear materials.  The most efficient way to produce compressed hydrogen is to perform electrolysis in deep water. When performed at a depth of 1000 meters the gas arrives at the surface pressurized to 100 bar.

  

Raising desalinated ocean water to an average height of 840 meters consumes considerable energy.

 

Hydrogen on the other hand is lighter than air and would rise from a depth of 1000 meters to any place on land of its own volition. It is a lifting gas because it is 14 times less dense than air. Above the surface compressed gas has the same energy potential as compressed air energy storage systems. 

 

Hydrogen is most frequently associated with stationary or transportation fuel cells. In the latter case the gas is compressed to between 350 and 700 bar for spatial and range considerations but the optimal operating pressure of PEM fuel cell systems in automotive or stationary applications is about 6 bar.

 

The relationship between work required and the compression of a gas is logarithmic so only 30% more energy is required to compress a gas to 700 bar from 100.  This extra work plus the potential inherent in the gas at 100 bar is recovered when the pressure is dropped back to the 6 bar used in the fuel cell.

 

In a fuel cell hydrogen is combined with oxygen to produce electrical energy and water in a process that is thermodynamically the opposite of electrolysis - the fuel cell produces the same amount of energy as is consumed in electrolysis.

 

Hydrogen is the ideal energy carrier because compressed it has the highest specific energy of any non fissionable material and it produces over 3 times the amount of energy as an equal weight of gasoline and when burned or is converted to electricity in a fuel cell and water is the only by-product. 

 

Hydrogen’s drawbacks are the energy required to compress it to the 350 to 700 bar (atmospheres) needed for volume and range considerations in most transportation applications and the CO2 produced by steam reforming of natural gas, which is the principal way the gas is produced commercially.

 

Steam reforming is used because electrolysis is between 3 and 10 times more costly but the CO2 negates much of the environmental potential of hydrogen when both are produced by this process.

 

High-pressure electrolysis is the cheapest form of electrolysis because it eliminates the need for further compression of the gas.

 

At 1000 meters, the deepest extent of a heat pipe OTEC system, the water pressure is 100 bar and electrolysis performed there would bring hydrogen to the surface at that pressure.

 

Producing hydrogen this way buys time to avoid climate catastrophe as the world transitions from fossil fuels to zero emitting energy and is the best rationale for moving to a hydrogen economy, with no emissions.

 

If climate catastrophe is imminent, we should be prepared to address the problem regardless of the cost. That is the primal human response to existential threats but since this is one of the cheapest ways to produce zero emissions energy with high capacity we should be transitioned to it on that basis alone.

 

According to a recent survey, 77 percent of Canadians believe hydrogen is the "wave of the future.”

 

Surely it is time to catch that wave?.

 

 

 

 

 

(Figure 1)