Solar Collector Soda-Lime Glass

The glass used on evacuated tubes must be very strong to resist environmental factors, as well as maintain the vacuum inside the tubes. Thermomax tubes use only the highest quality glass to insure resistance to snow, hail and wind, as well as maintain the vacuum over the life time of the tube.

Helium is a very small atom found in small quantities in the atmosphere. Because it is so small, it can actually travel through some types of glass (a process called diffusion). Since the vacuum is very important to the performance of the collector (and defined as the absence of molecules) this will cause the performance of the system to degrade over time. Borosilicate glass, used in most evacuated tube collectors, is susceptible to this phenomenon and soda lime glass,used in Thermomax collectors is not. F. Dewinter, author of “Solar Collectors, Energy Storage and Materials”, one of the main sources for information on solar systems, estimates the “Total heat loss can increase by 20% over 4.5 years in borosilicate glass evacuated collectors”. Because Thermomax uses only soda-lime glass in its collectors, this loss is minimized.

Another issue with glass on a solar collector is the strength of the tubes. Since they must be located on your roof and exposed as much as possible, they will be subjected to severe environmental challenges in their lifetime. Thermomax has tested borosilicate glass tubes and they have not met the high standards for certification required. Thermomax tubes are certified to take 5 hits from a one inch ice ball at 60MPH, withstand a snow load of 1100 lbs and winds up to 60 MPH without damaging the tubes.

If you are considering other tubes, make sure they use soda-lime glass and are certified for both snow load and the EN12975 hail impact test. Most other tubes on the market today do not have these features and certifications.

• Selective Coating on Collector
• Solar Collector Automatic Limiting Device
• Solar Thermal Heat Pipe
• High Vacuum Solar Collectors
• Solar Collector Soda-Lime Glass
• Solar Collector Hermetic Vacuum Seal and Flexible Neck

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