Overall, I think these differences will lead to separate production facilities and differing designs.
The 18650 is a form factor, not the chemistry.
Tesla uses the 18650 in the Model S and X but uses a 21700 form factor for the Model 3, Powerwall and Powerpack. They announced during their Battery Day event the transition to the 4680 form factor.
The Powerwall and Powerpack uses a Lithium NMC chemistry which is different from the Lithium NCA chemistry used in their automobiles.
* Clarification
I have the impression that Tesla tweaks the chemistry depending on the application. The cells used for power wall and grid storage might be slightly different to take advantage of those differences.
While weight/volume isn't important itself, reducing the weight/volume per kWh will also tend to reduce the cost per kWh since you're using less materials.
There are storage solutions that go further in taking advantage of the points you mention, such as flow batteries, but in that case I think it can be expensive to get high power output. The article mentions that price per kW is also important. With batteries you automatically get more watts the more watt-hours you add, which is useful in many cases.
Not yet, but if power production becomes more volatile (more wind/solar and ???) without associated demand response, how quickly you can charge and discharge starts impacting your duty cycle (“inventory turns per hour”).
But a faster recharge lets you do more of your buying the absolute trough. And faster discharge lets you capture more of any spike (but that’s less valuable methinks).
Kinda like being able to charge your Tesla with a bigger circuit at home so you don’t have to charge as much during peak hours.
A big market for grid batteries then becomes "frequency stabilisation services": they are paid not for actual turnover, but for being there and able to respond to demand within an AC cycle.
"On December 14, the Loy Yang coal power plant — one of the largest in Australia — suddenly went offline. In an instant, the grid shed 560 MW of electricity, enough to power 170,000 homes. 600 miles away, the Hornsdale Power Reserve battery system, as the Tesla system is officially known, kicked in within 140 milliseconds. It reacted so quickly, in fact, that the local grid operator was unable to measure the response time accurately. "
https://cleantechnica.com/2017/12/27/tesla-grid-storage-batt...
This is where hydro-based power plants excel, they're able to adjust the power output as quickly as gravity can push the water down the pipes. They're able to ramp up from almost no output to full capacity in minutes. Gas-turbines are also able to do this.
But it's well worth reading https://www.ofgem.gov.uk/system/files/docs/2019/09/eso_techn... on an actual UK grid trip event to see what kind of things can happen; start at "summary of event" on p4. Note the three paragraphs starting with "However" as subsequent stability systems also failed.
> This made the cumulative loss of generation 1,691MW
(!)
> All of the available “backup” power had already been deployed
Which in turn means if anything else goes wrong with the grid and there isn't enough generation, then all home solar countrywide cuts out, making the problem 10x worse.
Lesson learned: "I detected something weird, lets turn off" is not a good algorithm for everyone to use on a system requiring high uptime!
It was obvious from the start really...
I thought people were mounting these out in the garage.
For me that would be an 80° delta between the highest summer highs and the lowest winter low. The delta in places like Wyoming would be a lot more.
For $50 worth of electricity, you can keep something the size of a refrigerator 40 degrees F warmer than the outdoor air all year if you can surround it with an insulating box 2 inches thick.
In a car, the volume to surface area ratio is worse, and you can't guarantee it won't be left in the cold for months without a grid connection, so you need to ensure the chemistry can work cold.