If you don't have enough food, produce fewer children.
If you don't like fossil fuel, stop using it. No ones is forcing us to find an alternative.
It is really simple.
We already have the technology to produce electricity by solar power.
The only dilemma is, that if there is no profit, we humans tend to see things as useless.
Thats why we still use fossil fuels, because we are some cheap bastards, and we want everything to be about growth and production.
Yea, maybe it would take 10 hours to produce the same things which would normally only take 1 hour, but who is saying we are in a hurry?
And yes i agree with you that we need technology to save out planet now, but the only reason that we need to save the planet in the first place, is that we invented technology
Just imagine if there was no plastic garbage anywhere, no fossil fuels being burned and released into our atmosphere, no forrests chopped down by chainsaws, no need to breed entire races of cows and pigs indoors in giant mass-slaughtering butcheries just to be able to feed ourselves, and no need to constantly improve our weaponry, nukes and tanks.
All these problems that we have, and that we say we want to solve using technology, are actually rooted in technology. Because none of the problems would be existing if we had never invented them first. Of course there would be some hunger, but that has just something to do with overpopulation.
Technology is good until a certain point, after that point it will only result in decline. And we have passed that point hundreds of years ago.