Carbon-Recycling in Power-to-Gas energy storage configurations

Nowadays many people speak of Power-to-Gas and first demonstrations like the Thüga Project in Hessen (equipped with ITM Electrolyzes) were quite impressive. With inexpensive CO2 availability from e.g. a biogas plant a Substitute Natural Gas [ #SNG ] output energy efficiency of up to 50% of electric energy input may be achievable. And as long as the myth of Carbon Neutrality may continue to spook, such SNG may be steam reformed into Hydrogen for an electric output of 30% of original abundant electricity stored.

The smaller the scale of local Hydrogen requirement it might be more attractive to produce it from dry thermo- catalytic methane splitting. The graphene like Carbon Captured during such Hydrogen production can serve either as a crude-oil substitute refining intermediary or as an energy storage for later power to gas synthesis from excess new renewable electricity to the extent abundantly available for electrolysis.

Combining Carbon Recycling with Hydrogen production of Power-to-Gas Methane synthesis for storage and distribution across existing Natural Gas infrastructures, available electrolysis derived Hydrogen could yield 2 times the amount of substitute natural gas [ #SNG ]. Irrespective of using any calorific output from the various transformation losses, the SNG output energy efficiency is 96% of necessary energy input whereof abundant excess electricity for electrolysis and heat accounts for 56%. The remaining 44% are contributed by the graphene like Carbon previously captured for Energy Storage Use. So the electricity to electricity output/input efficiency would be between 50 – 60% of originally abundant electricity stored, depending on how the SNG was consummated.

Since we advocate for not combusting Methane for power generation, whether fossil or renewable synthesis derived, such SNG should undergo another Physical Carbon Capture cycle to release Hydrogen for Fuel Cell utility power on demand. Since at demand there won’t be any free energy to drive the Dry Thermo- Catalytic Methane Splitting at about 10% of the feedstock’s energy content, the 1st cycle’s Carbon would be consummated over 10 cycles. Therefore in average Carbon Efficiency is raised by factor 5.

Original local Methane feedstock could come from any sewage sludge or organic waste biogas plant as well as Natural Gas grid outlet whether containing SNG in part or not. Assuming there was not enough Hydrogen from electrolysis available, half the captured graphene like Carbon could be sacrificed into CO2 to achieve the molar ratio required for a Methane synthesis from the remaining 50% Carbon monoxide. In that case SNG net-output energy efficiency would be 90% of Carbon Energy Input, allowing an electricity output of 27% under repeated Carbon capture for Use as Energy Storage. Overall Carbon Efficiency improvement would still be 1.4 times higher than using Hydrogen Fuel Cell Utility from Methane Steam Reforming [ #SMR ].

For a world that aspires to exit from the use of fossil fuels by 2050 or earlier, a change of power generation and transportation from current direct hydrocarbon fuel combustion or reformation to Hydrogen-energy based systems in combination with decentralized Carbon Recycling would deem a way forward promising great practicability. Since Captured Carbon for Use is a storable and transportable aggregate the points of accrual could be remote from the points of its consumption. Since Dry Thermo- Catalytic Dissociation of Methane will always need catalyst replenishment and recycling of catalyst through the chemical use of the Carbon, some cartridge exchange systems might do the job even for household installations.


#CarbonRecycling, #Power2Gas,  #EnergyStorage

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