Solar thermal hot water systems — where solar heating is used to provide hot water to process applications — are becoming common in industrial applications where hot water is at a premium. Selecting an efficient, stable fluid to transfer heat from the rooftop panel down to the hot water heat exchanger is a key step to optimizing any solar thermal hot water system.
Solar rooftop panels can reach temperature exceeding 300°F (149°C). This temperature normally does not pose an issue as long as the heat transfer fluid circulates through the panel and removes heat. Issues can occur, however, when the fluid stops circulating due to a power outage or pump failure. If stagnant fluid in the panel reaches high temperatures, a number of scenarios are possible, depending on system design.