Investigation of the use of silicone sponge tube and design study of other components in solar thermal collector

Most solar thermal systems in Northern Europe have a separate antifreeze filled loop for protection against freezing and require a new tank fitted with a heat exchanger. When retrofitting to existing homes this means that a perfectly good tank (usually copper) needs to be replaced. We have developed an innovative solution that allows a domestic water supply to be heated directly, without the secondary fluid cycle. This increases the efficiency of the system and reduces capital and installation costs. Our solution allows the system to freeze but cause no system damage by using a compressible closed cell silicone sponge tube within an outer copper pipe. When it freezes the compressible tube takes up the expansion due to the ice and prevents pressure build up and damage to the system. This study will determine the optimum specification of the silicone sponge tube by trialling various specifications of tubes and sizes in a real world situation as well as freeze tests.