Hydrogen gas: Difference between revisions

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Hydrogen gas (H2) is a fuel that when burned, produces no pollution and no [[climate change|carbon emissions]] - only water vapor (H2O). Just one problem: There are '''no''' natural resources of hydrogen gas.
Hydrogen gas (H<sub>2</sub>) is a fuel that when burned, produces no pollution and no [[climate change|carbon emissions]] - only water vapor (H<sub>2</sub>O).


To make hydrogen gas, you need to use some other [[energy]] source.
There are '''no''' natural resources of hydrogen gas{{x|except in rare and extremely small quantities, not a viable way to supply [[energy]] in any meaningful amount}}. To make hydrogen gas, you need to use some other [[energy]] source. In this way, hydrogen can be understood as a form of [[energy storage]].


==Production==
==Production==
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===Electrolysis===
===Electrolysis===


Electricity can turn water (H2O) into hydrogen gas (H2) and oxygen gas (O2).
Electricity can turn water (H<sub>2</sub>O) into hydrogen gas (H<sub>2</sub>) and oxygen gas (O<sub>2</sub>). This process is called [[electrolysis]].


The electricity could come from renewable sources such as [[solar]], [[wind]], or [[hydro]].
The electricity could come from renewable sources such as [[solar]], [[wind]], [[hydro]], or [[geothermal]]. But even we manage to scale up those energy sources, there is still an issue with scaling up the electrolysis itself: [[electrolysis#need for catalyst metals|the need for rare metals]] in the electrolyzers.<!-- TODO: say more decisively whether this scaling is viable or not: but first there are questions to resolve on the [[electrolysis]] page -->


====Research needed for this page====
===From fossil fuels===
Can electrolysis be done efficiently on a medium scale, for example using the energy from a rooftop of solar panels?
 
Are rare minerals needed to make efficient electrolysis machines? If so, which minerals and how much of them; what are the different options?<!-- answered in [[fuel cell vehicles]] kind of already -->
 
Can natural-gas infrastructure be retrofitted for hydrogen gas, in general?


===From fossil fuels===
Currently most hydrogen is produced from [[natural gas]] via [//wikipedia.org/wiki/Steam_reforming steam reforming], but this emits just as much CO<sub>2</sub> as burning the natural gas itself.


Currently most hydrogen is produced from natural gas via [[wikipedia:steam reforming|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 CO<sub>2</sub>). The main problem is that it's a ''net loss'' of energy {{x|it takes 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> &rarr; C + 2 H<sub>2</sub> (endothermic: 74.850 kJ/mol)<br />2 H<sub>2</sub> + O<sub>2</sub> &rarr; 2 H<sub>2</sub>O (exothermic: 285.820 kJ/mol)}}


There's another (similar) process called [[methane cracking]] which takes in natural gas, and produces hydrogen gas + solid carbon (not CO2). The main problem, currently, is that it's a ''net loss'' of energy {{x|it takes more energy than you ultimately get by burning the hydrogen gas}}. In theory, it doesn't have to be.
==Usage==
{{p|Chemistry equations:<br />CH4 &rarr; C + 2 H2 (endothermic: 74.850 kJ/mol)<br />2 H2 + O2 &rarr; 2 H2O (exothermic: 285.820 kJ/mol)}}


==Uses==
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.
** This could be useful for [[heating]] and [[cooking]].
** It ''might'' be possible for some existing ''natural gas'' infrastructure be retrofitted for hydrogen gas.{{rn}}
*** If so, gas stoves could run on hydrogen.
* Hydrogen gas can be used for making electricity, using a ''fuel cell''.
** However, to use this in [[energy storage]] systems is quite '''lossy''':
*** "electricity &rarr; hydrogen gas &rarr; back to electricity" is ''at best'' only 40% to 48% efficient{{x|This is the combined energy-efficiency. The electrolyzers are about 80% efficient, and the fuel cells are about 50% to 60% efficient.}}.
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]].


Most hydrogen gas today is used in making [[fertilizer]].
==Color terminology==


But in the future it could also be used for:
Hydrogen is a colorless gas, but people sometimes ''name'' it with colors to indicate ''how it was produced'':
* powering [[electric vehicles|electric vehicles]]
* [[Grey hydrogen]] is made from natural gas steam reforming - high [[greenhouse gas]] emissions. Currently the vast majority of hydrogen is produced this way.
* [[energy storage]]
* [[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.<!-- TODO: cite that article I found awhile ago -->
* home [[heating]]
* [[Pink hydrogen]] is made from electrolysis using [[nuclear]] energy.
* cooking (similar to natural-gas stoves)
* [[Green hydrogen]] is made from electrolysis using renewable energy.
The general idea would be to use [[surplus electricity]] to generate hydrogen gas, and then use it as a fuel later.

Revision as of 23:08, 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(...)( except in rare and extremely small quantities, not a viable way to supply energy in any meaningful amount ). To make hydrogen gas, you need to use some other energy source. In this way, hydrogen can be understood as a form of energy storage.

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 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 (...)( it takes more energy than you ultimately get by burning the hydrogen gas ). In theory, it doesn't have to be. [''']Chemistry equations:
CH4 → C + 2 H2 (endothermic: 74.850 kJ/mol)
2 H2 + O2 → 2 H2O (exothermic: 285.820 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.
    • This could be useful for heating and cooking.
    • It might be possible for some existing natural gas infrastructure be retrofitted for hydrogen gas.[RESEARCH needed]
      • If so, gas stoves could run on hydrogen.
  • 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. ).

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:

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