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Can “second life” EV batteries work as grid-scale energy storage?

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Re: Can “second life” EV batteries work as grid-scale energy storage?

#131

Post by pfdietz »

kragen wrote: post #130
maxerickson wrote: post #100

Earlier quoted context omitted.

What's the proposed system design? For example, in January, I get about 9 hours of sunlight and have an average daily high of 25 F. I'm gonna need to store heat somehow or another.

I haven't seen pfdietz's proposed system design, but a so-called "sand battery," consisting of a box of sand with a heating element running through it, should work fine. You can PWM the heating element with a power MOSFET to keep it from overheating; you can measure its temperature with its own resistance, but also want additional thermocouple probes for the sand and to measure the surface of the box. A fan can blow…

Sand batteries have a much higher cost per unit of energy storage capacity, so they are in more direct competition with batteries for shorter term storage. It's hard to compete with a storage material you just dig out of a local hole. The economics pushes toward crude and very cheap.

Having said that: a good design for sand batteries would use insulated silos, pushing/dropping sand into a fluidized bed heat exchanger where some heat transfer gas is intimately mixed with it. This is the NREL concept that Babcock and Wilcox was (still is?) exploring for grid storage, with a round trip efficiency back to electricity of 54% (estimated) using a gas turbine. Having a separate heat exchanger means the silos don't have to be plumbed for the heat exchange fluid or have to contain its pressure.

Getting the sand back to the top (where it will be heated and dropping into silos) is a problem that could be solved with Olds Elevators, which were only recently invented (amazingly).

https://www.youtube.com/watch?v=-fu03F-Iah8

Re: Can “second life” EV batteries work as grid-scale energy storage?

#132

Post by MetaWhirledPeas »

jbm wrote: post #90
ACCount37 wrote: post #8

Earlier quoted context omitted.

A lot of the early EV battery life projections were based on Nissan Leaf Gen 1. Which had a horrendous battery pack that combined poor choice of chemistry, aggressive usage and a complete lack of active cooling. When EVs with good battery pack engineering started hitting the streets, they outperformed those early projections by a lot. And by now, it's getting clear that battery pack isn't as much of a concern - with…

I am a bit more concerned about batteries now as opposed to an year ago. We had this article from Elektrek [1] about battery issues in South Korea. When I asked my local electric maintenance shop [2, sorry for the FB link], they said they have started seeing the same issue in Model 3s and Ys in Canada as well. (They also said that it is too early to tell how common it would become) This may bode well for recycling si…

I would be more concerned if the source were anyone but Electrek~. Their vendetta against Tesla has forfeited all their credibility on Tesla news.

"many of these vehicles are now out of warranty, as they sometimes exceed the maximum mileage"

They have good numbers for the number of affected vehicles, but the best they can do for out-of-warranty stats is "many" and "sometimes". Convenient.

~To be fair this applies to a lot of popular tech sites I used to respect. Dunking on Tesla is its own industry these days, it seems.

Re: Can “second life” EV batteries work as grid-scale energy storage?

#133

Post by cptskippy »

cogman10 wrote: post #20
ACCount37 wrote: post #8

Earlier quoted context omitted.

A lot of the early EV battery life projections were based on Nissan Leaf Gen 1. Which had a horrendous battery pack that combined poor choice of chemistry, aggressive usage and a complete lack of active cooling. When EVs with good battery pack engineering started hitting the streets, they outperformed those early projections by a lot. And by now, it's getting clear that battery pack isn't as much of a concern - with…

I'll defend the leaf a little. LiPo batteries were quiet expensive when it was initially released. NiMH was really the only option in town. And with a lower energy density battery that's also heavier, adding a cooling system would have also added a bunch of weight to the already heavy car with a barely usable range of 100 miles. Gen 2, however, had no excuses. They had every opportunity to add active cooling and they…

> Gen 2, however, had no excuses. They had every opportunity to add active cooling and they still decided to go with just air cooling.

The Lizard pack in the later Nissan Leafs has held up surprisingly well. I have a 2015 that still gets 75 miles of range. I'm sure they thought it wasn't necessary and they probably had the actuarial numbers to justify it.

Re: Can “second life” EV batteries work as grid-scale energy storage?

#134

Post by alvah »

pfdietz wrote: post #49
hnaccount_rng wrote: post #41

Earlier quoted context omitted.

In addition to my sibling comment: The cost of the panels is a rather small fraction of the total cost of a typical installation. Most of that cost ist labor, some regulatory requirements and the inverter. Whether you pay a factor of 2 for the panels or not typically doesn't matter. In other words: Reusing used panels will only ever be able to safe you a minuscule amount.

The low cost of the modules themselves has led to the suggestion of cost optimized DC-coupled PV systems being used to directly drive resistive heaters. The cost per unit of thermal energy in a cost optimized system moderate scale system (> residential, Low cost modules allow one to do away with things like optimally tilted modules and single axis tracking. The modules can also be tightly packed, reducing mounting an…

Is it worth using heat pumps in this setup (in addition to resistive elements)? I understand they can't reach the absolute temperature of resistive heating, but from an efficiency POV for the first few tens of degrees they are much more efficient.

Re: Can “second life” EV batteries work as grid-scale energy storage?

#135

Post by adrianN »

floxy wrote: post #47
ACCount37 wrote: post #8

Earlier quoted context omitted.

A lot of the early EV battery life projections were based on Nissan Leaf Gen 1. Which had a horrendous battery pack that combined poor choice of chemistry, aggressive usage and a complete lack of active cooling. When EVs with good battery pack engineering started hitting the streets, they outperformed those early projections by a lot. And by now, it's getting clear that battery pack isn't as much of a concern - with…

Don't forget that the original Leaf pack was only 24 kWh. So if you assume a ~1000 full-equivalent-charge-cycles lifespan, then the large Gen2 62 kWh pack will live 2.5 times longer than an original 24 kWh pack. If you average 3.5 miles/kWh, the 24 kWh battery will be expected to last somewhere around 84,000 miles. While the 62 kWh pack will last for 217,000 miles. https://coolienergy.com/lfp-vs-nmc-batteries-the-sci…

Why would you only assume 1000 cycles? Is the chemistry that bad? The LFP battery on my balcony is rated for 5000 cycles iirc.

Re: Can “second life” EV batteries work as grid-scale energy storage?

#136

Post by adrianN »

apendleton wrote: post #72
epistasis wrote: post #27

Earlier quoted context omitted.

There's currently no technological path for fusion to be cheaper than fission. It would require a technological breakthrough that we have not yet imagined. And already, solar plus storage is cheaper than new nuclear. And solar and storage are getting cheaper at a tremendous rate. It's hard to imagine a scenario where fusion could ever catch up to solar and storage technology. It may be useful in places with poor sola…

> It would require a technological breakthrough that we have not yet imagined. Maybe, but not necessarily. The necessary breakthrough might have been high-temperature superconducting magnets, in which case not only has it been imagined, but it has already occurred, and we're just waiting for the engineering atop that breakthrough to progress enough to demonstrate a working prototype (the magnets have been demonstrate…

In the end we're still making steam and running a turbine. Just the steam turbine part of the power plant has a hard time competing with solar in sunny locations.

Re: Can “second life” EV batteries work as grid-scale energy storage?

#137

Post by cyberax »

pfdietz wrote: post #107
maxerickson wrote: post #100

Earlier quoted context omitted.

What's the proposed system design? For example, in January, I get about 9 hours of sunlight and have an average daily high of 25 F. I'm gonna need to store heat somehow or another.

The place I saw this most clearly described was in Standard Thermal's concept, which will store the heat in huge piles of dirt heated to 600 C. The thermal time constant of such piles can be many years. https://www.orcasciences.com/articles/standard-thermal-copy https://austinvernon.substack.com/p/building-ultra-cheap-ene... https://news.ycombinator.com/item?id=45012942

I ran the numbers on that, and it just doesn't work. Stone has rather lousy specific heat capacity (less than 1kJ/kg/K, compared to 4.2kJ for water).

A typical house in Midwest needs around 22,000kWh (7.913×10^10 J) over the winter (75 million BTU - https://www.eia.gov/todayinenergy/detail.php?id=57321 ).

If we assume the delta of 550 degrees (600 down to 50), you'll need: 7.913×10^10 J / (550K * 1000Jkg^-1K^-1) = 143,872,727 kg of material in your pile. This is a ridiculously stupid number. And I don't see any obvious mistakes?

Re: Can “second life” EV batteries work as grid-scale energy storage?

#138

Post by cyberax »

epistasis wrote: post #67
noosphr wrote: post #61

Earlier quoted context omitted.

China has been building out nuclear capacity at 5% a year for 25 years. Solar and wind capacity had shot through the roof in the last five years because they can't sell hardware to the west any more. The other big item is hydro power, which China has a ton of untapped potential for. Unfortunately for the West every good river has already been damed so we can't follow them there.

> Solar and wind capacity had shot through the roof in the last five years because they can't sell hardware to the west any more. "can't sell hardware??" hah! I've never heard that weird made-up justification, where did you pick it up from? China installed 277GW of solar in 2024, capacity factor corrected that's 55.4 GW of solar power. That's equivalent to the entire amount of nuclear that China has ever built. One y…

> China installed 277GW of solar in 2024, capacity factor corrected that's 55.4 GW of solar power.

The problem is not just the mean capacity factor, but the capacity factor in _winter_. It's terrible for China, less than 15%. And more importantly, you can have _weeks_ with essentially zero solar power when you need it most.

Re: Can “second life” EV batteries work as grid-scale energy storage?

#139

Post by kragen »

pfdietz wrote: post #131
kragen wrote: post #130

Earlier quoted context omitted.

I haven't seen pfdietz's proposed system design, but a so-called "sand battery," consisting of a box of sand with a heating element running through it, should work fine. You can PWM the heating element with a power MOSFET to keep it from overheating; you can measure its temperature with its own resistance, but also want additional thermocouple probes for the sand and to measure the surface of the box. A fan can blow…

Sand batteries have a much higher cost per unit of energy storage capacity, so they are in more direct competition with batteries for shorter term storage. It's hard to compete with a storage material you just dig out of a local hole. The economics pushes toward crude and very cheap. Having said that: a good design for sand batteries would use insulated silos, pushing/dropping sand into a fluidized bed heat exchanger…

(I completed my parent comment since you wrote your response, which may make it confusing to read your response; sorry about that.)

I agree that local dirt is much cheaper than trucked-in construction sand, but I think my design sketch above shows that a "sand battery" whose only moving parts are fans will be about 30× cheaper than a real battery at household scale, even though the sand is still most of the estimated cost. A "sand battery" designed to power a steam turbine is a much more difficult problem to solve, but in this case the stated problem is just that it's 24°F (-3°) outside, so I think much cheaper solutions are fine, with no pressure vessels, stainless steel, insulated silos, sand conveyors, or heat transfer fluids other than garden-variety air.

Do you have a good handle on the pressure (and therefore power) requirements for getting air to flow upward through sand? I feel like you ought to be able to get a pretty decent amount of thermal power out of half a tonne of sand with a really minimal amount of pumping, but that's only a gut feeling. Definitely as you go to graded-granulometry gravel the required head drops off to almost nothing.

Thanks for the link to the Olds device! That's utterly astounding. Archimedes could have used it for raising sand, although making a sturdy enough tube out of wood might have been a bit of a chore.

Re: Can “second life” EV batteries work as grid-scale energy storage?

#140

Post by cyberax »

pfdietz wrote: post #108
apendleton wrote: post #103

Earlier quoted context omitted.

In terms of cost of materials to build a reactor, sure, that seems right. But most of the cost of fission is dealing with its regulatory burden, and fusion seems on track to largely avoid the worst of that. It seems conceivable that it ends up being cheaper for entirely political/bureaucratic reasons.

Relaxed regulatory burden doesn't seem to be making fission competitive in China; renewables are greatly overwhelming it now, particularly solar. We might ask why regulations are so putatively damaging to nuclear, when they aren't to civil aviation. One possibility is that aircraft are simply easier to retrofit when design flaws are found. If there's a problem with welding in a nuclear plant (for example) it's extrem…

Regulation is not a problem, and even the construction costs are not terrible. We can take the Rooppur NPP as a base, it produces reliable energy at 6-7 cents per kWh. The reason for cost overruns is simply because NPPs are one-off products, the Western countries don't have a pipeline for NPP production.

For comparison, utility-scale solar with 16 hours of storage is 21 cents: https://www.utilitydive.com/news/higher-renewable-energy-cos...

Just raw solar without storage can be as low as 2-3 cents per kWh.

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