Hydrogen gas: Difference between revisions

From the change wiki
(→‎How much would be needed, if hydrogen were scaled up?: Added some more DPs, planning to use them in new estimates in future edits)
(Refactored page. But the PGMs section still needs redoing.)
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==Use-cases==
==Energy storage basics==
===Production===
For [[energy storage]] of renewable electricity:
* Storing energy from [[wind]] power, as the windy seasons and non-windy seasons both tend to last for months at a time.
* Hydrogen gas would be '''produced''' via ''electrolysis'':
* Storing energy from [[geothermal electricity]], which is only available in very specific geographical regions, usually far away from most [[population]] (power lines can't reach). The hydrogen gas can be transported to where people could use it.
** 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).}}


Hydrogen gas can be produced using electricity to split water molecules (H<sub>2</sub>O) into hydrogen gas (H<sub>2</sub>) and oxygen gas (O<sub>2</sub>). This process is called ''electrolysis''.


===Transport===
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.
{{pn|Research needed for this section}}
* Is it viable to repurpose natural gas pipelines? Or would it leak too much since H<sub>2</sub> molecules are much smaller than methane? {{rn}}
* How about pressurized storage tanks on trains? {{rn}}


===Usage===
Combustion
* for cooking (much like [[natural gas]] stoves)
* for [[heating]] homes / buildings
Fuel cells
* for [[fuel cell vehicles|vehicles]]
* for home electricity, in ''some'' cases{{en}}{{x|waste heat could also be used to heat the home}}
<small>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 people can smell if there's a gas leak.</small>


Hydrogen fuel cells are the opposite of the electrolysis mentioned above. A fuel cell takes in hydrogen gas (along with oxygen gas from the air), generates electricity, and leaves behind water vapor.
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.


===General===
Compared to batteries,
* Hydrogen is better for ''long-term'' energy storage.
* Hydrogen is better for transporting energy.
* Hydrogen is worse in terms of energy recovery.
** 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%.
Batteries may be better for storing [[solar]] energy from the daytime and using it at night.


===Compared to status quo===
==Energy sources==
Most hydrogen gas today is used for making [[fertilizer]], and is produced from natural gas. Fertilizer production can continue with renewables. This is a relatively small amount of hydrogen, compared to a "net zero carbon emissions scenario" involving all the use-cases above.
'''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.


==Considerations==
'''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.}}
===Platinum-group metals===
 
{{sum|Possible problem}}
'''Other use-case:''' Storing energy from [[hydroelectricity]] during long periods of low demand.
 
<!-- TODO: find number to fill this in with:
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]].
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<!-- 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===
==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.}} }}
-->
-->
==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 people sometimes ''name'' it with colors to indicate ''how it was produced'':
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... it continues from "compared to status quo" but doesn't quite fit in that section...
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> &rarr; C + 2 H<sub>2</sub> &emsp; (endothermic: &nbsp; 75 kJ/mol)<br />2 H<sub>2</sub> + O<sub>2</sub> &rarr; 2 H<sub>2</sub>O (exothermic: &nbsp; 572 kJ/mol)}}
{{p|Chemistry equations:<br />CH<sub>4</sub> &rarr; C + 2 H<sub>2</sub> &emsp; (endothermic: &nbsp; 75 kJ/mol)<br />2 H<sub>2</sub> + O<sub>2</sub> &rarr; 2 H<sub>2</sub>O (exothermic: &nbsp; 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.
** 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]].
-->
-->


<!-- TALK: maybe refactor the page to start with a section called "basics" that explains fuel cells, electrolysis, steam reforming and methane cracking? -->
==See also==
* [[Methane cracking]] {{light|- another way to produce hydrogen gas. Not worthwhile currently, but ''in theory'' the right tech could maybe change that.}}

Revision as of 17:17, 28 October 2023

Not to be confused with nuclear fusion of hydrogen atoms.

Hydrogen gas (H2) is a combustible fuel that leaves behind nothing but water vapor (H2O) when burned.

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.


This page is about how hydrogen gas could be used with renewable energy.


Energy storage basics

For energy storage of renewable electricity:

  • Hydrogen gas would be produced via electrolysis:
    • Electricity is used to convert water (H2O) 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 (and still some heat).
    • In both cases, the hydrogen reacts with oxygen in the air to form H2O 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 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.


The intent would be for hydrogen gas to be used in place of fossil fuels:

  • Cars, trucks, etc. would be:
  • Homes & buildings:
    • For heating: Hydrogen gas could be burned instead of natural gas.
    • For cooking food: Hydrogen gas could probably work with gas stoves. [RESEARCH needed]
  • 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.
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. Note, however: Batteries are a better choice for smoothing out the day/night cycle of solar power.

Other use-case: Storing energy from hydroelectricity during long periods of low demand.


Status quo


Platinum-group metals

Problem in some cases

Both electrolysis and fuel cells need platinum-group metals (PGMs):

  • [platinum, palladium, rhodium, ruthenium, iridium, osmium]
    • Any of these metals will do, but all of them are extremely scarce (even more than gold), with platinum & palladium being the most available.
    • These metals serve as catalysts in the reactions. They are not used up, but they need to be there, in a thin layer plated onto the electrodes.

Note: It is possible to build fuel cells and electrolysis systems without PGMs, but the energy-efficiency is much lower.[QUANTIFICATION needed] There are scientists trying to overcome this,[LINKS needed] but there's no guarantee that it will be viable in the near future.

How much would be needed, if hydrogen were scaled up?

The mass of PGMs needed is proportional to peak power:

  • For electrolysis systems, the maximum rate of hydrogen production is limited by the amount of PGMs.
  • For fuel cell vehicles, the horsepower is limited by the amount of PGMs.
    • But the vehicle can still achieve short bursts of higher horsepower if there's a battery or supercapacitor in parallel with the fuel cell.
world.population
8 billion
Number of people alive today, globally
https://www.unfpa.org/data/world-population-dashboard
Last updated in 2023
world.cars
1.446 billion
Number of cars in the world
Last updated in 2022
www.carsguide.com.au › car-advice › how-many-cars-are-there-in-the-wor...
hedgescompany.com › blog › 2021/06 › how-many-cars-are-there-in-the-...
toyota_mirai.pgm
30 grams
Amount of platinum-group metals (PGMs) in a Toyota Mirai (fuel cell vehicle)
The Toyota Mirai is a common example of a hydrogen-powered vehicle.

https://www.heraeus.com/media/media/hpm/doc_hpm/precious_metal_update/en_6/20181031_PGM_Market_Analysis.pdf
catalytic_converter.pgm
2 grams
Platinum-group metals (PGMs) in a catalytic converter of a car
Countless automotive forums say 3 to 7 grams for a typical car.

But ThermoFisher (which is more reputable, perhaps) says "The recoverable amounts of Pt, Pd, and Rh in each [vehicle] can range from 1-2 grams for a small car to 12-15 grams for a big truck in the US." - Are There Precious Metals in Catalytic Converters? https://www.thermofisher.com/blog/metals/platinum-group-metal-recovery-from-spent-catalytic-converters-using-xrf/

I assume they mean 1-2 grams ''total'', not 1-2 grams ''of each'' Pt Pd Rh, right? That would make sense considering they also mention that the ratios vary as metal prices/availability change over time.

1 to 2 grams total recoverable is also consistent with the following study: Yakoumis et al 2018 IOP Conf. Ser.: Mater. Sci. Eng. 329 012009 - Real life experimental determination of platinum group metals content in automotive catalytic converters - https://iopscience.iop.org/article/10.1088/1757-899X/329/1/012009/pdf

Still no word on what percentage this ''recoverable'' is of total PGMs - how efficient is the recycling process? Unknown
platinum.mine_production
186000 kg/year
Global production of new platinum from mining
Using data from 2019.

Source: USGS Mineral Commodity Summaries 2021
palladium.mine_production
227000 kg/year
Global production of new palladium from mining
Using data from 2019.

Source: USGS Mineral Commodity Summaries 2021
pgm.mine_production
platinum.mine_production + palladium.mine_production
Global production of platinum-group metals (PGMs) from mining
Assumption: that the other PGMs (iridium, rhodium, osmium, ruthenium) are in such small quantities that it's ok that they aren't counted here (because data is unavailable)
pgm.reserves
70000 tonnes
Global reserves of platinum-group metals
Includes platinum, palladium, ruthenium, rhodium, osmium, iridium.

Platinum-group metal reserves worldwide by country 2021
Statista - https://www.statista.com › statistics › platinum-me...
crop_land
15000000 km^2
Agricultural land used for growing crops - global total
https://ourworldindata.org/land-use
electrolysis.pgm_by_power
0.209 grams per kilowatt
Quantity of platinum-group metals (PGMs) in an electrolyzer
Electrolyzers make hydrogen gas from water & electricity. Platinum and/or similar metals are needed as catalytic plating.

Data source:
Manufacturing Cost Analysis for Proton Exchange Membrane Water Electrolyzers
August 2019 Technical Report NREL/TP-6A20-72740
https://www.nrel.gov/docs/fy19osti/72740.pdf
Pages 4 and 5: Table 1:
Cell plate area: CCM coated area: 748 cm^2
Platinum loading (anode): 7 g/m^2
Platinum-iridium loading (cathode): 4 g/m^2
Single cell power: 1965 W
From this we can calculate:
(7 g/m^2 + 4 g/m^2)/2 * 748 cm^2 / 1965 W = 0.20936387 g/kW
Sucks that the article doesn't directly specify this 'g/kW' value for us to confirm whether my calculations are correct. Still this is the best data source I could find. The article does also provide a lot of specs on total costs (ranging from $561/kW all the way down to $69/kW for some proposed systems with advanced techniques and economies of scale).
wind.capacity_factor
35%
Wind power: ratio: average output / peak power capacity
"The capacity factor of a wind turbine is its average power output divided by its maximum power capability. On land, capacity factors range from 0.26 to 0.52. The average 2019 capacity factor for projects built between 2014 and 2018 was 41%. In the U.S., the fleetwide average capacity factor was 35%."
https://css.umich.edu/factsheets/wind-energy-factsheet
wind.rq_land
34.5 hectares/MW
Land requirements of wind power
Important:
- This is per megawatt capacity (peak), not per average output.
- Stats can vary tremendously based on how windy the location is.
- This stat is based on 172 different wind projects scattered throughout the USA.
- Consider variance: (34.5 +/- 22.4) hectares/MW
- This is the total land use, including the spacing between turbines in a wind farm.
- This is much bigger than [wind.rq_land_disturbed] which is just the land directly impacted by constructing the turbine itself.

Citation:
Land-Use Requirements Of Modern Wind Power Plants In The United States
(Paul Denholm, Maureen Hand, Maddalena Jackson, and Sean Ong)
Page 16
energy.tfc
9937.70 Mtoe/year
Global energy usage - total final consumption (TFC)
Includes: fuel (80.7%) + electricity (19.3%) AFTER it is generated.

Does not include the fuel used in generating electricity. See [energy.tes] for that.

Citation: "Key World Energy Statistics 2020" IEA
- Page 47 - Simplified energy balance table - World energy balance, 2018
fossil_fuels.energy
11596.92 Mtoe/year
Total consumption of coal, oil, and natural gas (worldwide)
Key World Energy Statistics 2020 (IEA report)
- page 47: World energy balance, 2018
- - Total Energy Supply (TES), first 4 columns combined
electrolysis.efficiency
80%
Energy efficiency of producing hydrogen & oxygen gases from water
Hydrogen made by the electrolysis of water is now cost-competitive ...
www.carboncommentary.com › blog › hydrogen-made-by-the-electrolysis...
commercial_factor
2
Without this, we'd be calculating for just personal vehicles. But we also need to factor in commercial vehicles such as buses and trucks. These vary widely in size, and data is hard to find, so for simplicity sake, we just assume that they'd add up to about the same as personal vehicles - thus doubling total energy storage needed. This assumption is based on the fact that freight trucks are a somewhat smaller share of energy demand than passenger vehicles, but the trucks probably need a longer range.

Suppose,

  • that all of today's energy demand were to be met using hydrogen gas
  • that all hydrogen gas were to be produced using wind power (or something with the same capacity factor as wind)
  • that all PGMs can forever be recovered and recycled

Tl;dr: There are enough PGM minerals in the Earth, but today's mining rates would be far too slow.
We'd have to start mining a lot faster, and find some way to do it without exploitative labor. [ELABORATION needed]

Calculations: PGMs needed for hydrogen production: energy.tfc / wind.capacity_factor * electrolysis.pgm_by_power grams per capita * world.population production_pgm (calculation loading)

PGMs needed for hydrogen-based electricity consumption: world.cars * toyota_mirai.pgm grams per capita * world.population consumption_pgm (calculation loading)

PGMs recoverable from catalytic converters of old gas cars:Old semi trucks (not counted here) could also provide a bit more world.cars * catalytic_converter.pgm grams per capita * world.population recyclable_pgm (calculation loading)

Compared to mineral reserves: production_pgm + consumption_pgm - recyclable_pgm % pgm.reserves (calculation loading)

Compared to current production rate: production_pgm + consumption_pgm - recyclable_pgm years pgm.mine_production (calculation loading)

This estimate is imperfect and oversimplified, but probably reasonable in a scenario where some vehicles use hydrogen combustion and some use fuel cells. In general,

  • If more vehicles use hydrogen combustion, we'd need more wind power but less PGM.
  • If more vehicles use fuel cells, we'd need less wind power but more PGM.

In any case, producing that much wind power is maybe reasonable if most farmland were to be covered in wind turbines. energy.tfc / wind.capacity_factor * wind.rq_land % crop_land (calculation loading)

More musings about the calculations above:

  • Hydrogen combustion vehicles are about as energy-efficient as gasoline combustion vehicles. But hydrogen fuel cell vehicles are more efficient. We'd need less hydrogen than this estimate calls for.
  • Home electricity would be done with fuel cells too. We'd need more PGMs than this estimate. We'd need more hydrogen than this estimate, to make up for the losses in fuel cells (although those losses could be used as heating in some cases).
  • If electric semi trucks use fuel cells too, we'd need more PGMs than this estimate.
  • Or if a large enough percent of all vehicles use combustion instead of fuel cells, then we'd need less PGM than this estimate.
  • We didn't count the hydrogen needed in the vehicles that transport the hydrogen (hopefully would be minor, like with fossil fuel transport).
  • All this is based on status-quo energy demand, which relies on the fact that most of the world currently lives in poverty. If all nations were developed, a lot more resources would be needed.
  • Wind power land estimates are based on status-quo installations which are likely on windier-than-average land. In which case, maybe crop land wouldn't be enough - but then again, there's also pasture and barren land that could be used.
  • But in any case, we probably wouldn't actually use wind/hydrogen for everything anyway. Rooftop solar combined with batteries could probably be a better way to provide electricity whenever hydrogen need not be involved.
  • 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.


Energy losses

Lossy but manageable
  • Electrolysis is at most 80% efficient.
  • Fuel cells are at most 60% efficient.
  • Thus, best-case electricity recovery is only 48%(...)( 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.

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

[RESEARCH needed]

Chemically, hydrogen is the lightest gas (smallest molecules). This makes it harder to store than other gases, but there are still ways. [ELABORATION needed]


Pipelines

[RESEARCH needed]

Could existing natural gas pipelines be used for transporting hydrogen gas? Or would it cause too much leakage/corrosion? [RESEARCH needed]


Safety

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(...)( 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.
  • This section needs more safety-related info.


Color terminology

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.
  • "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.


See also

  • Methane cracking - another way to produce hydrogen gas. Not worthwhile currently, but in theory the right tech could maybe change that.
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