My undergrad thesis was about modeling a home-sized solar-thermal to electricity setup. The answer was (1) you could barely eek out something of value if you really tried (2) it would be beaten by solar panels hands down.

The problem is that electricity production is dependent on the difference in temperature between your hot liquid and the environment. And the 70C-30C with water you will get in the summer is simply not enough to produce much. Realistically, you need ten times this difference to do anything useful.

The other option is to heat oil, with lower heat capacity. That you could heat to a bit higher temperatures, but then you are going to continuously lose oil that has to be topped up.

Unfortunately, despite my dreams, such systems seem economically unrealistic.