Just use EVs. EVs are primarily energy storage devices, some people get to drive them about 20 - 30 mins/day. The remaining 23 hours, it is a energy storage device. It can absorb excess power when price is negative, and can even supply power back to the grid when prices are high!
Its more than pennies[1]. By several orders of magnitude. Car batteries now last longer the rest of the car lifespan, it will be millions of miles soon.
In my country for home consumers the difference between day/night rates is 10-20c/kWh. With spot pricing I can see it working to cover the post commute power spike - but you're effectively doubling your commute discharge rate and pushing charge levels to suboptimal levels.
Batteries might work but at 80% capacity they are worth significantly less than new - both in terms of utility and resale value.
Maybe if battery range gets extended so far that even at 80% capacity it's an overkill - like 1000mile batteries - I could see myself doing something like this - but at current ranges and charging setups - I'll skip the few dozen euro a month.
On the other hand battery prices are dropping exponentially. There's a good argument to be made that your battery is a depreciating asset not (just) because it's degrading, but because the technology is getting cheaper, and thus you should extract as much value from it as possible as quickly as possible (and then replace it).
The caveat to this market is who knows how much of a premium you'll end up paying to replace the battery given that it's attached to a certain model of car.
> On the other hand battery prices are dropping exponentially.
Are they ? I keep hearing this but in practice the price of an EV is still dominated by the battery pack and the movement in EV prices is anything but exponential. China started pushing out the affordable EVs but that's because they are using less efficient/cheaper chemistry and even with better packaging they are significantly less energy dense.
I've seen Toyota announce 1000 miles solid state battery - if battery tech was dropping exponentially that should be cheaper than ICE in a few years - I would take the opposite side of that bet.
China's LFP battery packs, as of 2022, have a density of 160 Wh/kg [1], which matches the NMC battery pack in a Model Y from the same year [2] (Note: The Model Y battery pack was no doubt designed and built earlier given that it was already in a product). I.e. is isn't really the case that the batteries they are putting in are less efficient than the earlier iterations. Though you could have even high energy density batteries if you didn't switch to LFPs.
I'm not sure we are racing towards 1000 mile cars, because I'm not sure it's the case that there's a huge market for 1000 mile cars, and there's limits on density short of technological leaps that would make such vehicles heavy. I think we're rather more likely to see 600km cars just keep dropping in price instead.
Yes, exactly this has been proposed with "smart car chargers," along with other things you can do if the grid operator has some control over a bunch of grid-connected equipment. It hasn't taken off as far as I know, probably because that means the car battery wears out more.
The "virtual power plants" are the closest thing to this idea that is actually done in practice. That's individuals who own batteries joining some collective that then sells to the grid the ability to reduce demand a bit. Tesla did a pilot program with its Powerwalls iirc.
That is a great thought and there is a lot of research in using batteries of vehicles for grid stabilization as well as arbitrage trading.
The problem, however, is that a lot of plugged vehicles are required to guarantee a meaningful amount of firm power/energy capacity and owners typically do not want to sacrifice a lot of flexibility when they rent out their batteries to provide such services.
Furthermore, as you can see from the replies, many are scared about battery degradation. Because of this and due to the fact that reverse charging is not possible for most vehicles, this schemes are often restricted to delayed charging which further limits revenue potential.
However, using arrays of old car batteries as stationary batteries is a very viable idea that, in my estimation, will lead to a significant growth in installed BESS in a couple of years.
