Frankly, I'm doing the reading and research on this stuff as I go while teaching the class. We haven't gotten to the grid yet, so I would need to report back in a few weeks on some of your questions. I'm enjoying teaching the class, because this stuff is really interesting and important and it gives me a good reason to learn it.

On solar, we have efficient enough panels to make it work without going crazy covering huge chunks of the Earth. Obviously we don't have to get 100% of our power that way anyways, but the link shows the area coverage we would need for reasonably achievable 10% efficient solar panels. I used that map in class last week. It's simultaneously a ton of actual area (100k+ square miles) and not all that daunting when you visualize it that way. We wouldn't have to kick people off their farms or out of their homes to do it. For grid-scale power, you can take advantage of putting the panels in deserts where land is readily available and it's always sunny, but getting the power back to the people and staffing the solar farms is a real hurdle (not a lot of skilled workers in the Sahara Desert). But, the economics of solar has made the cost per kWh go way down in recent years. It's really just a matter of continuing to build and integrate. There's a ton of DOE investment in battery research, which is what's really needed to continue to expand solar on the grid. You've got to be able to time shift your power from day to night. We aren't there yet, but it's promising IMO.

One of the issues with solar roofs and personal-scale solar power is how to meter it into the grid. It's not that hard to generate enough electricity for a house so that you're net positive, which means you can sell it back to the power company. But practically you have to stay on the grid for backup and different states have different policies on what the power company can charge. Since I'm teaching in Alabama, I shared this link on how Alabama is handling (or really failing to handle) the challenge: https://www.al.com/news/2021/06/alabama-last-among-southern-states-in-solar-power-but-change-could-be-on-the-horizon.html

Thanks for a good conversation. This is way more fun than bickering about Trump and Biden all the time. :)