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== | ==Energy storage basics== | ||
For [[energy storage]] of renewable electricity: | |||
* Hydrogen gas would be '''produced''' via ''electrolysis'': | |||
* | ** Electricity is used to convert water (H<sub>2</sub>O) into hydrogen gas and oxygen gas. | ||
* Hydrogen gas would be '''consumed''' via... | |||
** Burning it as fuel, producing heat. | |||
** Using it in ''fuel cells'', producing electricity {{light|(and still some heat)}}. | |||
** {{light|In both cases, the hydrogen reacts with oxygen in the air to form H<sub>2</sub>O again (water vapor).}} | |||
This process has more energy losses than charging/discharging a battery, but hydrogen gas is far better suited for '''long-term''' energy storage. Hydrogen can be stockpiled in pressurized tanks (if designed properly). It can also be [[transportation of hydrogen gas|shipped]] long distances, just like any other fuel. This could help in cases where renewable energy sources are geographically far away from where energy is needed. | |||
Hydrogen fuel | The intent would be for hydrogen gas to be used in place of [[fossil fuels]]: | ||
* Cars, trucks, etc. would be: | |||
** [[Hydrogen combustion vehicles]], or | |||
** [[Hydrogen fuel cell electric vehicles]] | |||
* Homes & buildings: | |||
** For [[heating]]: Hydrogen gas could be burned instead of [[natural gas]]. | |||
** For cooking food: Hydrogen gas could probably work with gas stoves. {{rn}} | |||
* Factories: | |||
** Most of the energy used in manufacturing is in the form of high heat needed for processing materials. Factories could burn hydrogen gas instead of burning [[coal]] or natural gas. | |||
== | ==Energy sources== | ||
'''Main use-case:''' Storing [[wind]] power.<br /> | |||
Here's why: | |||
* Wind power is far more intermittent than [[solar]]. Whereas solar follows a day/night cycle, windy and not-so-windy seasons can last for ''months'' at a time. | |||
* Wind turbines tend to be geographically far away from where electricity is needed, on average. Wind power is more spread out in terms of [[land]], compared to the same amount of energy from local [[rooftop solar]]. Hydrogen could be transported long distances that can't be reached with power lines. | |||
== | '''Other use-case:''' Since solar panels produce more energy in the summer, it would still be worthwhile to store ''some'' of that energy via hydrogen gas, to be used during the winter. {{light|Note, however: Batteries are a better choice for smoothing out the ''day/night cycle'' of solar power.}} | ||
{{sum| | '''Other use-case:''' Storing energy from [[hydroelectricity]] during long periods of low demand. | ||
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For renewables & hydrogen to replace all fossil fuels, hydrogen production & consumption would have to scale up by about ___ times the status quo. | |||
--> | |||
==Status quo== | |||
* Most hydrogen today is '''produced''' from [[fossil fuels]] ([[natural gas]]) via [//wikipedia.org/wiki/Steam_reforming steam reforming]. The carbon emissions are as high as burning the natural gas itself. | |||
* Most hydrogen today is '''used''' in producing [[fertilizer]]. | |||
==Platinum-group metals== | |||
{{sum|Problem in some cases}} | |||
Both '''electrolysis''' and '''fuel cells''' need platinum-group metals (PGMs): | Both '''electrolysis''' and '''fuel cells''' need platinum-group metals (PGMs): | ||
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* Since vehicle fuel cells use the biggest share of PGMs in this estimate, this is yet another reason to advocate for [[public transit]] and [[walkability]]. | * Since vehicle fuel cells use the biggest share of PGMs in this estimate, this is yet another reason to advocate for [[public transit]] and [[walkability]]. | ||
</div></tab></tabs> | </div></tab></tabs> | ||
<!-- TODO: Uncomment this when done writing about PGMs above (a more immediate and important mention that should be on here first) | <!-- TODO: Uncomment this when done writing about PGMs above (a more immediate and important mention that should be on here first) | ||
==Atmospheric losses== | |||
{{sum|Probably minor}} | {{sum|Probably minor}} | ||
The concern would be that when hydrogen gas leaks to the atmosphere, it's so light that it ends up being lost into outer space via [//wikipedia.org/wiki/Jeans_escape Jeans escape]. At what point would this permanent loss of hydrogen affect ecosystems? Would it be on the scale of billions of years or millions of years or thousands? Per unit of energy, I bet there would actually be hydrogen loss than with [[nuclear fusion]]. {{rn}} {{pn|TODO: Estimate using the status-quo gas leak rate of natural gas.}} }} | The concern would be that when hydrogen gas leaks to the atmosphere, it's so light that it ends up being lost into outer space via [//wikipedia.org/wiki/Jeans_escape Jeans escape]. At what point would this permanent loss of hydrogen affect ecosystems? Would it be on the scale of billions of years or millions of years or thousands? Per unit of energy, I bet there would actually be hydrogen loss than with [[nuclear fusion]]. {{rn}} {{pn|TODO: Estimate using the status-quo gas leak rate of natural gas.}} }} | ||
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==Energy losses== | |||
{{sum|Lossy but manageable}} | |||
* Electrolysis is at most 80% efficient. | |||
* Fuel cells are at most 60% efficient. | |||
* Thus, best-case ''electricity'' recovery is only 48%{{x|in other words, 60% of 80%}}. Far less than most batteries which have a charge-discharge efficiency of 80% to 90%. | |||
** But for things that just need ''heat'', then the energy recovery is still a good 80%. For example, wind power to produce hydrogen gas to burn for heating homes. | |||
*** Note however: For vehicles, this is outweighed by the fact that [[hydrogen combustion vehicles]] are less fuel-efficient than [[fuel cell vehicles]]. | |||
{{pn|TODO: add calculation: knowing the losses, is there still enough [[land]] for wind-generated hydrogen gas were to directly replace all fossil fuels, in principle?}} | |||
==Shelf life== | |||
{{sum|{{rn}} }} | |||
Chemically, hydrogen is the lightest gas (smallest molecules). This makes it harder to store than other gases, but there are still ways. {{en}} | |||
==Pipelines== | |||
{{sum|{{rn}} }} | |||
Could existing natural gas pipelines be used for transporting hydrogen gas? Or would it cause too much leakage/corrosion? {{rn}} | |||
==Safety== | |||
{{sum|Manageable}} | |||
* Just like natural gas, hydrogen gas is non-toxic and odorless but highly flammable. For safety in consumer applications, small quantities of some non-toxic but smelly gas{{x|such as methyl mercaptan, hydrogen sulfide, or ethyl isobutyrate (Wikipedia has a page "Hydrogen odorant")}}should be added to it, so that people would know if there's a gas leak. | |||
* {{pn|This section needs more safety-related info.}} | |||
==Color terminology== | ==Color terminology== | ||
Hydrogen is a colorless gas, but | Hydrogen is a colorless gas, but researchers 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. | * "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.<!-- TODO: cite that article I found awhile ago --> | * "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 --> | ||
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SCRAP: Not sure where to put this | SCRAP: Not sure where to put this, if anywhere at all: | ||
===Production from fossil fuels=== | ===Production 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.org/wiki/Steam_reforming steam reforming], but this emits just as much CO<sub>2</sub> as burning the natural gas itself. | ||
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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: 75 kJ/mol)<br />2 H<sub>2</sub> + O<sub>2</sub> → 2 H<sub>2</sub>O (exothermic: 572 kJ/mol)}} | {{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)}} | ||
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==See also== | |||
* [[Methane cracking]] {{light|- another way to produce hydrogen gas. Not worthwhile currently, but ''in theory'' the right tech could maybe change that.}} |