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Comment by ok_dad | Hacker News Reader

10 hours of discharge time (20 MW power peak with 200MWh energy storage) is good, but not "long term" to me. It is barely sufficient for storing solar/wind overnight. "Long term energy storage" to me is several days or more at peak power. I'm excited for all these different methods, though, because unlocking energy storage is key to reducing carbon emissions, since most of the base load is from carbon emitting power sources.

Edit: I clarified that I meant the amount of energy stored not how long the gasses themselves can be stored. "Long term energy storage", to me, should be defined as being able to discharge at max power for like a day or more, and this tech is more "medium term" storage, again in my opinion.

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I have never understood that sentiment. If you define long term energy storage as being able to discharge at max power for a day or a week you are penalizing superior storage technologies for no reason. Let's say that you have two technologies that have the same cost per KWh, the same round-trip efficiencies, etc. Now let's assume one of them has a maximum discharge rate of C/100 so that at maximum power it lasts for 100 hours. Let's assume the other technology has a maximum discharge rate of 1C, so at maximum power it lasts for 1 hour. For the same price, you could have either a system that only works for long term storage or a system that would be considered "short term" storage even though it has the same capacity and the same price as the long term option. There may be some exceptions, but generally whenever you have short term storage you automatically have the option of long term storage as well by just discharging at a lower rate.

Sure, but I’m in the industry and it’s standard to talk about hours of storage based on the power max and energy capacity.

SV Clean Energy issued an RFO that defined LDS as 8+ hours of ESS:

https://www.svcleanenergy.org/joint-lds-rfo/

Sure but in that respect I diverge, I think they’re setting a low bar.

The plant they are building can store 10 hours worth of electricity at maximum delivery power (200MWh @ 20MW). TFA does not say how long they can store the electricity for.

They are turning c02 from a gas into liquid form. So I assume they can store it indefinitely.

I expect it becomes financially unviable if they end up storing it for long. Daily charge/discharge allows them to amortize their annual cost of capital across 365 cycles. Weekly or seasonal storage is going to be much less cost effective.

Calm, cloudy days do happen, so we either need seasonal storage, or need to be okay with much less electricity on such days.

I guess depending on the storage mechanism, the length of stored time isn't really an area of concern. I routinely store full propane tanks for months, for example. Its a significantly smaller molecule but I would think similar timescales could be achieved with CO2.

As per the headline, it's "long-duration storage" meaning that you can potentially wait a while (days, weeks) before that discharge of stored energy.

From the article: "many hours up to many days"

> "Long term energy storage", to me, should be defined as being able to discharge at max power for like a day or more,

"Long term money storage" should be defined as storing more than $10 000 - yes, no, or irrelevant?

> “Long term money storage" should be defined as storing more than $10 000 - yes, no, or irrelevant?

Your example should be more like “a long term emergency savings is 6 months of your budget” vs. “a short term emergency savings is 2 months of your budget”

there's a guy on Twitter that runs sims of Australia's power usage that claims 5 hours of storage is enough for year round use of renewables so 10 hours could be a big deal

Link? Overnight you would need “length of night time” as the minimum capacity for a grid to support zero carbon base generation, assuming all renewables, so he must be using a value with carbon base generation support, I’m assuming we need even more storage when we eliminate carbon base generation.

I don't know what you mean by carbon base generation. You need to compensate for shortfalls in renewable production.

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