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One thing they neglect to mention (which is by no means a deal-breaker) is that you waste a good portion (about half) of the electricity in the process of charg
by elil17 1y ago
One thing they neglect to mention (which is by no means a deal-breaker) is that you waste a good portion (about half) of the electricity in the process of charging and discharging the pile of dirt. Chemical batteries are much more efficient in this regard.
- eplawless 1y agoThey mention it: > There is an efficiency penalty converting back to electricity; round-trip efficiency is 40%-45%, but sometimes the steady supply of electricity is worth it.
- carlos_rpn 1y agoI didn't have time to read the whole thing so I don't know if they mention it, but another article about about using sand as heat storage pointed out one of the advantages is that the material isn't toxic, unlike chemical batteries.
- pbhjpbhj 1y agoThere were reports last year, IIRC, of "sand shortages". Presumably a logistics infrastructure problem that could be relatively easily overcome?
- carlos_rpn 1y agoI remember those reports. I wonder if it has to be the same kind of sand, or could be some that we neither have another use for, nor would damage any ecosystem (too much).
- coryrc 1y agoThat's of "sharp sand". Sand batteries don't need sharp sand.
- Aurornis 1y agoThey do mention it, but it’s downplayed relative to how much of a problem it can be. In a situation where you have a lot of energy generation that would go to waste, storing it in a system with low round trip efficiency could be better than losing it. For planned installations where the generation cost is nontrivial (like a solar install) then increasing the generation to compensate for poor battery efficiency isn’t as easy of a decision.
- nyeah 1y agoYeah, when baseline efficiency is zero then there's probably room for improvement.
- capitainenemo 1y agoOne thing they also mention is how incredibly cheap storage of natural gas is. https://en.wikipedia.org/wiki/Power-to-gas#Efficiency https://en.wikipedia.org/wiki/Power-to-gas#Efficiency The efficiency of power to gas is not great, but it's about the same as this thermal storage method, with probably much longer lifetimes,easier transportation and more general utility (the natural gas could for example be converted to methanol using the holy grail catalyst that was in the news recently). The power to gas is also carbon neutral, even negative depending on what you decide to do with the natural gas (if you don't burn it for power but use it for industrial chemistry, you get some sequestration out of it).
- pfdietz 1y agoThe problem is the cost of getting the carbon and hydrogen to make the natural gas. If you're making a synthetic fuel, you might as well make methanol, which can be stored as a liquid, and is about as easy to make from syngas as methane.
- capitainenemo 1y agoYeah, did mention the methanol option as an additional step once the natural gas is created. But is the cost of getting the carbon and hydrogen that high? In a P2G system you'd be electrolysing water (plentiful) and combining it with carbon dioxide (also relatively plentiful, although it can also be linked to an existing fuel burning plant for better efficiency). There are existing production systems using this approach right now with surplus energy from renewables described in the wikipedia article.
- pfdietz 1y agoGetting it from existing fuel burning plants defeats the whole purpose. Direct air capture is out, so it'll have to be recovered from the combustion of the synfuel. Using the Allam cycle has been explored to do this (you also have to store the oxygen from electrolysis for later use in this oxyfuel combustion cycle) but it ends up being more expensive than just burning hydrogen, if there's reasonable geology for hydrogen storage. So, if this thermal storage scheme is cheaper than hydrogen, as it appears it will be, then these alternative synfuel schemes are ruled out.
- yodelshady 1y agoMore efficient, but much more expensive. I'm sick of people handwaving $100 per kWh. That is two orders of magnitude off where it needs to be to do anything more than virtue signal. Meanwhile multiple grids are now paying renewable to curtail, because guess what, the variability is correlated (it's the exact same damn mathematics we used to fuck up the entire global economy in 2008, which is why I'm so surprised people are handwaving that too, but whatever). If you want to minimise cost without relying on gas to save you on dark still days, you want a cheap use for the surplus, round-trip be damned.
- Panzer04 1y ago100$/kwh on a battery that does 1000 cycles is 10c/kwh, 5000 cycles ("Claimed" lifepo4 these days), that's 2c per kwh. These aren't that unreasonable, albeit one would need to account for cost of capital and so on increasing these effective numbers. Batteries are already economical in most grids where they can arbitrage daily prices of 0-10c during the day to 10-30c during the night, with the occasional outlier event contributing dollars per kwh. They will never load-shift across seasons, agreed, but for daily loadshifting they are already economical, and being 90%+ efficient (and very simple/easy to deploy and scale) is part of why they're popular. It opens up power shifting opportunities that aren't just daytime solar too.
- yodelshady 1y agoThey are doing seasonal storage - i.e. on a timescale of a year! So no, they are not doing 5000 f*king cycles! This is systematic fraud by the renewables industry and should be called out.
- pfdietz 1y agoHe was talking about batteries there, not Standard Thermal's storage solution. The point of the thermal storage is that it is complementary to batteries, which aren't suitable for seasonal storage and are not being used for seasonal storage.
- adgjlsfhk1 1y ago
- Symmetry 1y agoSolar prices are coming down quite fast, I don't think a factor of two is going to be a killer here if the storage is cheap and long-lasting enough. Some people are already considering over-provisioning solar panels relative to available transformers/grid connections so that they can maintain output on cloudier days. "What do we do with all the extra power when the belly of the Duck Curve [1] hits the ground" is a problem lots of people are thinking about. [1]https://en.wikipedia.org/wiki/Duck_curve https://en.wikipedia.org/wiki/Duck_curve
- olejorgenb 1y agoYeah, but then people should start to actual incorporate the full cost of these kind of things in the total cost of solar power when comparing it to other sources.
- pbhjpbhj 1y agoI think generating hydrogen for fuel cells seems prima facie a reasonable approach?
- elil17 1y agoThat has similar efficiency compared to this but probably looks much worse in terms of capex
- pfdietz 1y agoOr hydrogen for combined cycle power plants, which have a LHV efficiency in excess of 60%. This scheme is probably superior though, with lower capex and working at smaller scale, especially if one doesn't have deep salt formations to solution mine for hydrogen storage caverns.
- tgtweak 1y agoThe cost-prohibitive portion of this, which is greatly glossed over in the article and which I showed in my other reply - is that the steam generator required to recover this heat as electricity, is a massive part of the capex - more than half of the entire system end-to-end, including the solar and dirt storage. That makes the economy of it far less viable even with nearly free solar, which we're still quite far from.
- Ekaros 1y agoBut chemical batteries cost a lot more and don't have lifespans of hundreds or thousands of years in seasonal storage scenarios. And when electricity is in essence too cheap like with solar and wind it can be, losing half in efficiency actually doesn't matter too much.
- nordsieck 1y ago> But chemical batteries cost a lot more and don't have lifespans of hundreds or thousands of years in seasonal storage scenarios. Practically speaking, you're probably not going to get 1000s of years out of any storage method. There's just too much stuff that breaks down. Heck - a lot of historic dams are in the low hundreds of years old and are experiencing serious problems. IMO, the shorter lifespan of batteries isn't that big of a downside as long as the "bad" batteries can be mined for raw materials eventually.
- turtlebits 1y agoWe're talking about the storage layer, dirt/sand won't break down.
- stinos 1y agoAnother thing they don't seem to mention is environmental impact (if there even is any worth mentioning, not sure).
- pfdietz 1y agoHowever, for long term storage, the "cost of inefficiency" is swamped by the amortized capex of the batteries. The goal is to minimize capex, not maximize efficiency. This becomes even more true as the cost of the input energy declines.