Hydrogen gas: Difference between revisions
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There's another (similar) process called [[methane cracking]] which takes in natural gas, and produces hydrogen gas + solid carbon (not CO<sub>2</sub>). The main problem is that it's a ''net loss'' of energy {{x|it takes a lot more energy than you ultimately get by burning the hydrogen gas}}. In theory, it doesn't have to be. | There's another (similar) process called [[methane cracking]] which takes in natural gas, and produces hydrogen gas + solid carbon (not CO<sub>2</sub>). The main problem is that it's a ''net loss'' of energy {{x|it takes a lot more energy than you ultimately get by burning the hydrogen gas}}. In theory, it doesn't have to be. | ||
{{p|Chemistry equations:<br />CH<sub>4</sub> → C + 2 H<sub>2</sub> (endothermic: | {{p|Chemistry equations:<br />CH<sub>4</sub> → C + 2 H<sub>2</sub> (endothermic: 75 kJ/mol)<br />2 H<sub>2</sub> + O<sub>2</sub> → 2 H<sub>2</sub>O (exothermic: 572 kJ/mol)}} | ||
==Usage== | ==Usage== |
Revision as of 23:18, 27 January 2023
Hydrogen gas (H2) is a fuel that when burned, produces no pollution and no carbon emissions - only water vapor (H2O).
There are no natural resources of hydrogen gas
Production
Electrolysis
Electricity can turn water (H2O) into hydrogen gas (H2) and oxygen gas (O2). This process is called electrolysis.
The electricity could come from renewable sources such as solar, wind, hydro, or geothermal. But even if we manage to scale up those energy sources, there is still an issue with scaling up the electrolysis itself: the need for rare metals in the electrolyzers.
From fossil fuels
Currently most hydrogen is produced from natural gas via steam reforming, but this emits just as much CO2 as burning the natural gas itself.
There's another (similar) process called methane cracking which takes in natural gas, and produces hydrogen gas + solid carbon (not CO2). The main problem is that it's a net loss of energy
CH4 → C + 2 H2 (endothermic: 75 kJ/mol)
2 H2 + O2 → 2 H2O (exothermic: 572 kJ/mol)
Usage
Most hydrogen gas today is used in making fertilizer. However, there are other things that could be done with hydrogen if production was scaled up enough:
- Hydrogen gas can be burned.
- Hydrogen gas can be used for making electricity, using a fuel cell.
- However, to use this in energy storage systems is quite lossy:
- "electricity → hydrogen gas → back to electricity" is at best only 40% to 48% efficient
(...)( This is the combined energy-efficiency. The electrolyzers are about 80% efficient, and the fuel cells are about 50% to 60% efficient. ) .
- "electricity → hydrogen gas → back to electricity" is at best only 40% to 48% efficient
- However, to use this in energy storage systems is quite lossy:
In this way, fuel cell vehicles are not as efficient as battery electric vehicles. At least they're still more efficient than hydrogen combustion vehicles.
Color terminology
Hydrogen is a colorless gas, but people sometimes name it with colors to indicate how it was produced:
- Grey hydrogen is made from natural gas (steam reforming) - high greenhouse gas emissions. Currently the vast majority of hydrogen is produced this way.
- Blue hydrogen is made from natural gas the same way, but with carbon capture. This is supposed to reduce emissions, but in practice it doesn't help much.
- Pink hydrogen is made from electrolysis using nuclear energy.
- Green hydrogen is made from electrolysis using renewable energy.