Methane cracking: Difference between revisions
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==Energy viability== | ==Energy viability== | ||
{{sum|'''Not''' viable}} | {{sum|'''Not''' viable (except in theory)}} | ||
Every methane-cracking method ''invented so far'' is a '''net loss''' of energy. Meaning that it takes more energy to crack the methane than you ultimately get from burning the hydrogen. | Every methane-cracking method ''invented so far'' is a '''net loss''' of energy. Meaning that it takes more energy to crack the methane than you ultimately get from burning the hydrogen. |
Revision as of 02:02, 9 February 2024
Methane cracking
Energy viability
Every methane-cracking method invented so far is a net loss of energy. Meaning that it takes more energy to crack the methane than you ultimately get from burning the hydrogen.
But in theory, this need not be true:
- Cracking the methane:
- CH4 → C + 2 H2 (energy in:endothermic reaction 74.850 kJ/mol)
- CH4 → C + 2 H2 (energy in:endothermic reaction 74.850 kJ/mol)
- Burning the hydrogen:
- 2 H2 + O2 → 2 H2O (energy out:exothermic reaction 571.640 kJ/mol)
Hydrogen production efficiency comparison
Type | Method | Energy out / energy in |
---|---|---|
Methane cracking | Theoretical best case | 764% from the chemistry equations above |
Not methane cracking | Electrolysis of water | 80% |
Methane cracking | Best technologies so far | . . . To be filled in soon. It's almost certainly less than 80%. |
Not methane cracking | Heat -> turbine -> electrolysis of water | 25% |
There have been some green initiatives to use non-fossil-fuel energy to crack methane to make hydrogen gas. However, this is only worthwhile if the efficiency is better than non-methane-cracking ways to make hydrogen (see table).
Above 100%, you don't need any non-fossil-fuel energy for it to be green. Just burn some of the hydrogen to keep cracking the methane. Sadly, this has never been achieved.
In the ideal case, fossil fuels could power the entire world with zero carbon emissions. At least, until oil and gas reserves run out.