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You seem to be under the impression that the cost of hydrogen storage comes almost exclusively from the cost of electricity used for electrolysis of water. This

You seem to be under the impression that the cost of hydrogen storage comes almost exclusively from the cost of electricity used for electrolysis of water. This is not the case. Even if we assume zero electricity costs, th cost of storing hydrogen amounts to over a thousand dollars per KWh. Current estimates place this at $1,400 per KWh per year for the average case assuming that the electricity provided is free [1]. That works out to $3.80 per day per kilowatt hour of storage. Even for the optimistic estimated provided by this study, it's still $800/KWh/year - still over $2.00 per day. And again, this is assuming that free excess wind generation is used to get generate hydrogen. Us retail energy costs are about $.13/KWh. Industrial costs are $.07/KWh. For diurnal storage, hydrogen energy storage represents a 20x cost increase even in the best case estimates for the storage cost and assuming that excess wind generation will pick up th slack. And for non-diurnal storage the costs are even higher per KWh because a smaller amount of delivered electricity needs to pay off the same amount of capacity cost. Also, before you point at figure 16, know that this graph includes "capacity credits" - it's not the actual cost. 1. https://www.google.com/url?sa=t&source=web&rct=j&url=https://prod-ng.sandia.gov/techlib-noauth/access-control.cgi/2011/114845.pdf&ved=2ahUKEwiOnYj9wLbqAhVXJzQIHZLrDSYQFjAGegQIBBAB&usg=AOvVaw3nNskLLKaSysr_Dltygx1B https://www.google.com/url?sa=t&source=web&rct=j&url=https:/...

pfdietz 6y ago
> You seem to be under the impression that the cost of hydrogen storage comes almost exclusively from the cost of electricity used for electrolysis of water. Nowhere did I say or imply that. My argument is actually the complete opposite. What hydrogen does is get a much lower cost per unit of energy storage capacity, at the cost of lower efficiency . The cost per energy capacity of batteries is two orders of magnitude higher than for hydrogen storage. So, hydrogen exploits that for long term storage, it's ok to waste more input energy, if you can get the capital cost down. > Us retail energy costs are about $.13/KWh. Industrial costs are $.07/KWh. The correct figure to look at is wholesale price, which is often below $.03/kWh in US power markets, and lower at off peak times when one would make hydrogen. https://www.eia.gov/todayinenergy/detail.php?id=42456 https://www.eia.gov/todayinenergy/detail.php?id=42456 > For diurnal storage, hydrogen energy storage I explicitly wasn't talking about diurnal storage. That's not the use case for hydrogen. The use case is long term storage. > And for non-diurnal storage the costs are even higher per KWh because a smaller amount of delivered electricity needs to pay off the same amount of capacity cost. Hydrogen has a huge advantage in long term storage, because the per-energy capacity cost is so damned low, compared to batteries. Yes, the cost per kWh stored in long term storage is higher than the cost per kWh in short term storage. But they are different use cases and one cannot be substituted for the other. If you optimize the problem of providing a steady output from renewables over the days and years, you will find in most places that a mix of short term and long term storage is optimal. Neither substitutes for the other.
- manfredo 6y ago
  > The correct figure to look at is wholesale price, which is often below $.03/kWh in US power markets, and lower at off peak times when one would make hydrogen. Again, the estimates shared in the study are made with the assumption that electricity used for hydrogen production is free. This is why I am left with the impression that you think the energy used for electrolysis amounts to a large portion of the cost of hydrogen storage. Because you seem to be fixated on the cost of electricity, even though hydrogen storage is still incredibly expensive even if electricity is 100% free. No, hydrogen does not have low cost of energy storage. Average estimates place the cost at $1,400 per KWh per year for average estimates and $800 per KWh per year for optimistic estimates. And for the third time, just to make sure that this fact gets across, these estimates are made with the assumption that the electricity supplied to generate hydrogen is at zero cost from surplus renewable generation. This cost needs to be recovered from people drawing the stored energy. If all this energy is being drawn in one day of the year, it's going to cost $1,400 or $800 per kilowatt hour depending of whether you use the average or optimistic estimates. If you draw the energy on 10 days out of the year then it's going to cost $140 or $80 per KWh. How does this make it more suitable for long term storage? It doesn't. Even if the cost were spread out over the entirety of the year it would cost anywhere from 60 to 120 times as much as the wholesale price of $0.03 per KWh. If this energy is only going to be draw on for part of the year this cost increase is going to be even larger because the same cost of storage needs to be recuperated from a shorter period of sales. It's the most suitable solution for long term storage by virtue of the fact that it's one of the only mechanisms we have for long term storage with our current technology. It's nowhere near cost effective. The costs are the total opposite of "so damn low".
  - pfdietz 6y ago
    Sigh. You are just not connecting the dots. Yes, the cost to store hydrogen for LONG TERM STORAGE is higher than the cost to store electricity in batteries for SHORT TERM STORAGE. But the cost to store hydrogen for long term storage is LOWER than the cost to store electricity in batteries for the long term. If you are comparing batteries short term with hydrogen long term, you are comparing apples and oranges. Your study does NOT say batteries are cheaper than hydrogen for long term storage. They could not possibly be cheaper for that, since there are too few charge/discharge cycles to amortize the batteries' very high cost per kWh of capacity. You seem to be saying "just use short term storage!". But that's not a legitimate approach, since there are long term variations in supply and demand. Short term storage only applies to short term variations.
philipkglass 6y ago
I think that you are misreading units somewhere. I don't see anywhere in that report that looks like $1400/kWh for hydrogen systems. Are you referring to Figure 14? The "Spilled Wind - Current Technology" bar there looks like it could be about $1400. But that graph is dollars per kilowatt, not per kilowatt hour. It refers to a system with 6 hours of storage.

pfdietz 6y ago

> You seem to be under the impression that the cost of hydrogen storage comes almost exclusively from the cost of electricity used for electrolysis of water. Nowhere did I say or imply that. My argument is actually the complete opposite. What hydrogen does is get a much lower cost per unit of energy storage capacity, at the cost of lower efficiency . The cost per energy capacity of batteries is two orders of magnitude higher than for hydrogen storage. So, hydrogen exploits that for long term storage, it's ok to waste more input energy, if you can get the capital cost down. > Us retail energy costs are about $.13/KWh. Industrial costs are $.07/KWh. The correct figure to look at is wholesale price, which is often below $.03/kWh in US power markets, and lower at off peak times when one would make hydrogen. https://www.eia.gov/todayinenergy/detail.php?id=42456 https://www.eia.gov/todayinenergy/detail.php?id=42456 > For diurnal storage, hydrogen energy storage I explicitly wasn't talking about diurnal storage. That's not the use case for hydrogen. The use case is long term storage. > And for non-diurnal storage the costs are even higher per KWh because a smaller amount of delivered electricity needs to pay off the same amount of capacity cost. Hydrogen has a huge advantage in long term storage, because the per-energy capacity cost is so damned low, compared to batteries. Yes, the cost per kWh stored in long term storage is higher than the cost per kWh in short term storage. But they are different use cases and one cannot be substituted for the other. If you optimize the problem of providing a steady output from renewables over the days and years, you will find in most places that a mix of short term and long term storage is optimal. Neither substitutes for the other.

manfredo 6y ago
> The correct figure to look at is wholesale price, which is often below $.03/kWh in US power markets, and lower at off peak times when one would make hydrogen. Again, the estimates shared in the study are made with the assumption that electricity used for hydrogen production is free. This is why I am left with the impression that you think the energy used for electrolysis amounts to a large portion of the cost of hydrogen storage. Because you seem to be fixated on the cost of electricity, even though hydrogen storage is still incredibly expensive even if electricity is 100% free. No, hydrogen does not have low cost of energy storage. Average estimates place the cost at $1,400 per KWh per year for average estimates and $800 per KWh per year for optimistic estimates. And for the third time, just to make sure that this fact gets across, these estimates are made with the assumption that the electricity supplied to generate hydrogen is at zero cost from surplus renewable generation. This cost needs to be recovered from people drawing the stored energy. If all this energy is being drawn in one day of the year, it's going to cost $1,400 or $800 per kilowatt hour depending of whether you use the average or optimistic estimates. If you draw the energy on 10 days out of the year then it's going to cost $140 or $80 per KWh. How does this make it more suitable for long term storage? It doesn't. Even if the cost were spread out over the entirety of the year it would cost anywhere from 60 to 120 times as much as the wholesale price of $0.03 per KWh. If this energy is only going to be draw on for part of the year this cost increase is going to be even larger because the same cost of storage needs to be recuperated from a shorter period of sales. It's the most suitable solution for long term storage by virtue of the fact that it's one of the only mechanisms we have for long term storage with our current technology. It's nowhere near cost effective. The costs are the total opposite of "so damn low".
- pfdietz 6y ago
  Sigh. You are just not connecting the dots. Yes, the cost to store hydrogen for LONG TERM STORAGE is higher than the cost to store electricity in batteries for SHORT TERM STORAGE. But the cost to store hydrogen for long term storage is LOWER than the cost to store electricity in batteries for the long term. If you are comparing batteries short term with hydrogen long term, you are comparing apples and oranges. Your study does NOT say batteries are cheaper than hydrogen for long term storage. They could not possibly be cheaper for that, since there are too few charge/discharge cycles to amortize the batteries' very high cost per kWh of capacity. You seem to be saying "just use short term storage!". But that's not a legitimate approach, since there are long term variations in supply and demand. Short term storage only applies to short term variations.

philipkglass 6y ago

I think that you are misreading units somewhere. I don't see anywhere in that report that looks like $1400/kWh for hydrogen systems. Are you referring to Figure 14? The "Spilled Wind - Current Technology" bar there looks like it could be about $1400. But that graph is dollars per kilowatt, not per kilowatt hour. It refers to a system with 6 hours of storage.