Can Solar Thermal Collectors heat water to a high-enough temperature?

It all depends on the solar insolation (sunlight) for that day.The Evacuated tubes set at the proper angle, based on your needs, produce more heat as the sun angle lowers with the season. Basically, as the outside air temp rises, the panels produce less heat as the sun is at a higher angle. As seasonal temps get colder, the panels get hotter and produce more heat for your domestic hot water needs and house heating. The system would be designed to deliver a daily DHW storage tank temperature rise of 25-30 C/35-55 F. With most designs, this heat is stored in a tank, then with a heat exchanger, goes into your existing DHW tank and/or house heating such as baseboard or in-floor hydronics, hot tub or swimming pool.