[pfdietz]

Not really. For long term storage, the cost of a unit of energy storage capacity becomes more important than the round trip efficiency. This is all the more the case when the cost of the input energy declines.

For seasonal storage, hydrogen is vastly better than batteries, even with a RTE of 40%. That's because the cost of an underground hydrogen storage cavern can be as little as $1 per kWh of storage capacity.

[_aavaa_]

But the units of energy you need to store are directly related to your efficiency.

[pfdietz]

Efficiency of the discharge part, yes. But that's a less than factor of 2 effect that can't overcome the two orders of magnitude superiority over batteries in cost per unit of storage capacity.

[_aavaa_]

Compared to batteries maybe, but that’s not the only alternative, and isn’t even the main alternative for long term storage.

Hydro being the simplest long term alternative.

Even if we stay with batteries, they’re price is continuing to trend down. That two order of magnitude you quote is only going to get smaller. What can’t be overcome is again the thermodynamic limit.

[pfdietz]

I'm merely pointing out that this thermodynamic handwaving doesn't demonstrate what you appear to be claiming it demonstrates.

What is this other technology, btw? Be specific and quantitative here.

[_aavaa_]

We have gotten on a discussion of storage, which is a little afield of the original point, an alternative to nuclear fission for meeting our energy demand. That, and not storage specifically, is the actual target:

- Build out solar and wind to cover the winter usage, not the summer usage (the cost with them not running is longer payback period, they do not have negative energy prices).

- Build pumped hydro storage for longer term storage

- Build more hydro

- Change how you use hydro: use them as your "peaker" to handle when the sun and wind go offline

- No city/state/country is an island, build more HVDC connecting countries, especially EAST-WEST so that even when the sun has set here we have an extra hour or two of solar from the west.

- Build batteries for short term usage (see the Horndale battery in Australia for incredible short payback periods)

- Store heat/cold when you have the renewable and then use it as heat/cold.

- And build nuclear it's great baseload, if you can afford the actual price after the massive overruns.

But again, before we start coming up with new use-cases for hydrogen, we need to solve the 90 million tonnes annually made directly from fossil fuels. Until that's done, hydrogen remains a GHG problem, not a GHG solution.