[jeff5may]

If your solar collectors are expected to reach 200degC, you had better deal with the possibility of steam generation in your design. Especially if the collector flow may stagnate (purposely or accidentally) during full sun exposure. One high pressure event is all it takes to destroy lots of work.

Actually, a concentrated solar system using alcohol as antifreeze would have a LOWER boiling point than water alone. Like around 80-90 degC, depending on the strength of alcohol. So what you are proposing here is a high-temperature solar still. If designed properly, your setup might not even need much of a pump at high temperatures. Just design your heat exchanger to also function as a condenser.