J.Midi, From my time reading the panel over the past 10 yrs plus, the user HighFlyer has been a great help to others and has a great handle on the technology and implementation. He hasn't been on the forum as much lately but he may respond to a direct message.
if you google pondboss and solar projects you may find many other useful threads. I found this one that delves quickly into the technical side. It sounds like it gets cold enough by you that you may need special equipment, controllers, and non-standard batteries to keep it going, or at least size the batteries so they don't discharge too low each time before charging again.
The type of pump is important when working with solar. Also with natural wind aeration on the top you may not need as much turning over of the deeper water. Traditionally the goal is to turn over your entire volume once every 24 or so hours but in your case you have wind action mixing of much of the water in the top acre feet so you may be able to turn over the bottom water a little less frequently and still achieve the goal.
Start with this thread, maybe reach out to HighFlyer, and if you have a lot of time to read (there are 16 pages of mressages!!) I'll also post a link to a long standing thread about how solar was added in the extreme conditions of a pond at 10,000 ft elevation in Colorado and was (eventually) successful in preventing winter kill for the first time ever. THere are fantastic photos and diagrams in this link.
Thread 1:
Good solar tech threadThread 2 Extreme solar:
8 acre pond at 10,000'
