Reddit mentions of Solar Engineering of Thermal Processes

I am a huge fan of the technology and the physics. The best part about estimating solar gains, is once you understand the geometry, it becomes very simple.

I don't have any good learning resources, I learned at university my books are currently in boxes.

Instead, I have the link to the national solar data. This data can be used to estimate nearly any location in the US with good success. The database contains radiation measurement information from a TON of airport and other weather monitoring locations. You find the location closest to where you are trying to estimate and pull the data in for your model. Once you have a good program/script/spreadsheet you can just dump in data for your location and auto-generate your yearly or daily gains (on any day).

https://www.nrel.gov/gis/data-solar.html

This was my book: https://www.amazon.com/Solar-Engineering-Thermal-Processes-Duffie/dp/0470873663/ref=asc_df_0470873663/?tag=bingshoppinga-20&linkCode=df0&hvadid={creative}&hvpos={adposition}&hvnetw=o&hvrand={random}&hvpone=&hvptwo=&hvqmt=e&hvdev=c&hvdvcmdl={devicemodel}&hvlocint=&hvlocphy=&hvtargid=pla-4583726541174521&psc=1

It's not focused on photovoltaic / electric panels, so it may not be 100% what you're looking for, but I think the book handles the geometry and radiation bits of the problem. Beyond gains estimation, it really becomes a matter of which commercial system you want to buy. If you're interested in furthering the solar energy technology, you're probably better off looking into material science or straight-up physics.

I read a few years that PV technology has gotten so good, thermal systems are obsolete as you can just use electricity to generate heat, but I've not seen any hard numbers on that and it may come down to need.