PGMs required for hydrogen production vs for fuel cell vehicles
- Electrolysis: To turn water into hydrogen & oxygen gases, using electricity.
- Hydrogen fuel cell: Does the opposite of electrolysis: Produces electricity, powered by hydrogen & oxygen, leaves behind water vapor as exhaust.
Electrolysers and fuel cells both require 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.
The supply of PGMs is limited to what we can mine from the Earth (mineral reserves / resources), so we have to be mindful of how much would be needed.
How much would be needed, if hydrogen were scaled up?
world.population
8 billion
Number of people alive today, globally
https://www.unfpa.org/data/world-population-dashboard
Last updated in 2023
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-...
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
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
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
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
Source: USGS Mineral Commodity Summaries 2021
pgm.status_quo_mining_production
platinum.mine_production + palladium.mine_production
Global production of platinum-group metals (PGMs) from mining (status quo)
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 mineral 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...
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).
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
https://css.umich.edu/factsheets/wind-energy-factsheet
For comparison, nuclear power has a much higher capacity factor (over 90%) because it's not intermittent the way wind is. If the hydrogen gas were produced from nuclear instead, less PGM would be needed.
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
- 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
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.consumption
11596.92 Mtoe/year
Total consumption of coal, oil, and natural gas (worldwide) (energy units)
Key World Energy Statistics 2020 (IEA report)
- page 47: World energy balance, 2018
- - Total Energy Supply (TES), first 4 columns combined
- 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...
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 need far more horsepower and probably a longer range.
Scenario 1: If hydrogen gas (from wind power) were to directly replace all fossil fuels (this implies that people would drive hydrogen combustion vehicles):
(calculation loading) (calculation loading) PGMs needed for hydrogen gas production.
- The amount of PGMs needed is pretty reasonable (16% of mineral reserves). We'd still have to mine for PGMs a lot faster than the status-quo (and do it without exploitative labor). [new page needed]
To prevent NOx emissions, hydrogen combustion vehicles need catalytic converters, just like gasoline or diesel vehicles do. Catalytic converters also contain some PGMs, which could be obtained by recycling old catalytic converters from fossil-fuel vehicles.
Scenario 2: If all vehicles were hydrogen fuel cell vehicles instead:
(calculation loading) (calculation loading) PGMs needed to make the fuel-cell vehicles.Fuel-cell vehicles don't have catalytic converters, but a fuel cell contains far more PGMs than a catalytic converter.
- One benefit of fuel cell vehicles is that they're more energy-efficient than combustion vehicles (i.e. less hydrogen used per kilometer driven).
- The problem is, the fuel cells alone would need 7 times more PGMs mined than Scenario 1 (estimated). Perhaps too much to be scalable. And this is true even though we factored in the recycling of old catalytic converters.
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.
More musings about the calculations above:
- All of this assumes that electrolyzers and fuel cells can be completely recycled at their end-of-life, with all PGMs recovered. If they can't, we're kind of screwed in the long run (at least for hydrogen).
- Hydrogen combustion vehicles are about as energy-efficient as gasoline combustion vehicles. Hence we can assume that the Scenario 1 estimate is accurate enough.
- Home electricity can also be done with fuel cells - this would of course need more PGMs (and more hydrogen to make up for the losses in fuel cells (although those losses could be used as heating in some cases)).
- 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 unfortunately relies on the fact that most of the world currently lives in poverty. If all nations were developed, more resources would be needed.
- 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.
Verdict
- If we're going to have hydrogen-powered vehicles, most of them will probably have to be combustion only (or some sort of hybrid with just a very small fuel cell).
- At least PGMs are not a limiting factor for wind-based hydrogen production.