alt Hacker NewsI think it's less a question of batteries being economical, and more a question of the relative economics of batteries vs solar panels.
After all, if the highest demand is between 16:30 and 19:00 you could use batteries to store power at 12:00 and sell it at 18:00 - or in famously sunny Australia you could build enough solar panels that solar output at 18:00 matches power demand.
If batteries have a solid 9% return on investment, but solar panels have an even better 12% return on investment, panels will outpace batteries even though the batteries are a decent investment.
(Also, from a politican's perspective, making batteries highly economical is how you get batteries built. And an awful lot of pro-environment policies involve raising taxes, banning things and creating new chores; it's nice to have some green policy announcements that actually benefit voters in the short term.)
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You won't get 12% return if your panels generate electricity which is only paid between 18 and 19, because there is already overcapacity between 16:30 and 18.
> If batteries have a solid 9% return on investment, but solar panels have an even better 12% return on investment, panels will outpace batteries even though the batteries are a decent investment.
EDIT
I forgot to say: I like your idea of intraday arbitrage using batteries! It is a very cool idea. Surely, this could be well modeled to know your expected ROI before investment/build-out.
> you could build enough solar panels that solar output at 18:00 matches power demand
No you could not. For half the year the sun has set by 18:00.