I try to bite my lip lately, and be quiet, but think about what you are being told. Your solar thermal will create 'too much' heat? To them, it is a problem if temperatures go above what would turn the fluid in the system, water, to steam.
Some industrial evacuated tubes are relatively cheap to make compared to photovoltaic. They also collect energy better in areas that are temperate and often cloudy. If let loose to what they can do, they can heat the hot end up to several hundred degree C, and not break down.
If you used oil instead of water, as a transfer fluid, storing it in a tank, there are in fact several Stirlings out there already or about to come to market, that could have the hot end inserted into this tank, and run fine to produce a steady flow of power, even overnight, when there is no sun, if designed right.
Now I creap back into my hole.