How about this as a fix:
The excess solar energy goes to a battery charging vending machine for EVs that sits in the driveway. Someone with a low battery for an e-bike/scooter or nanocar books a battery and pops by to swap their low battery for a full one. That would perhaps be a way to profit from selling the excess energy instead of getting ripped off by the grid.
schools and farms cannot use their own solar energy production and must sell it to the grid at a low price and buy it back at a significantly higher price.
The thing is, they are feeding the grid when the sun is hitting hard (mid-day) which is the time of day when the grid needs the most help. So they are helping to flatten the consumption peaks. They should be getting the best sales price at that point. So it’s like they are getting boned for improving the grid and giving the powerplant relief.
Indeed universal standards can’t be expected to exist or relied on and my comment doesn’t assume that.
What I would envision is a company that needs to deploy a battery swapping infrastructure for a car like this one (which I hear is common in Spain). People and businesses with extra solar power could have a 3rd-party drop off a vending machine which could be brand-specific.
Or it could be scooter batteries. I heard about battery swapping station for scooters in the UK. I don’t recall the brand though.
(update) It’s worth noting that a sustainable user-repairable battery is being planned, called the “Infinite Battery”:
https://www.ifixit.com/News/101675/bike-manufacturers-are-making-bikes-less-repairable