I've been chatting to another user on here (https://slrpnk.net/u/JacobCoffinWrites who does the cool photobash images of solarpunk scenes) and it really got me thinking about solar concentrators so i went on a bit of a binge learning about them, there are so many really cool designs and so many things a source of heat like that can be used for.
One idea i especially like is using it to power absorption refrigeration (like off-grid gas powered refrigerators use) so when the sun is hot you can focus it's power and use it to cool your house -- then when it's starting to get cooler switch it to heating, ideally heating a medium which will retain the heat so you can distribute it through the night. For agricultural use it could heat greenhouses and drying rooms, industrially there's an endless amount of possibilities. Even recreationally it could be great, cutting out the cost of heating a pool or hot tub - could really make some off-grid luxury.
A great youtube channel with various diy examples is Sergiy Yurko, who's still managing to make great videos despite living in Ukraine - https://www.youtube.com/@sergiyyurko8668/videos
and https://www.youtube.com/@GREENPOWERSCIENCE/videos has some really cool videos too, like demonstrating using a fresnal lens to melt metal
I built a parabolic trough collector with automatic sun tracking. reflective area was 1 x 3 m, good enough to cook food at 80-90°C in a 20cm diameter oven tube.
If I built it again now I might not use the sun tracking, I think it's overengineering. Nicer to set up a workflow where you move the collector without having so much stuff that can malfunction on there (motors, sensors, electronics board ...), or build one large enough that you don't have to move.
I saw the super high temperature fresnel stuff in Tamera - but it's not something I would confidently build in a well-equipped home workshop.
About the only thing I remember from Thermodynamics in university: avoid transforming and transporting energy needlessly. If you want heat, use the heat you already have. Instead of building a field of 2m PV panels in the Sahara and transporting the electric energy to my home in Europe, where I use it to plug my air or water heating device, I should always find out where unused heat can be found in my environment and try to coax that into my process. Which is why instead of getting more experience in photovoltaics I just built this monstrous collector thingy together with a few other people, and started investigating stirling engines - because they are small scale, silent, flexible about their heat source (so concentrated solar energy can be turned directly into mechanical energy for example - for a more efficient solar pump).
Another low energy low impact favourite tech of mine are ram pumps. They can be set up uninvasively in a stream and pump water into a reservoir - to be used for irrigation and energy harvest. I've had them filling IBCs during about three months in summer last year before the stream dried, and didn't set them up because I have no way yet to take the water without damming up, and it felt wrong to do so. I will have to cut my way through some thorny shit and make a natural dam a little more upstream to get enough height, but it's worth it if I don't want to rudely interrupt the lives of the stream creatures.