The heat exchanger of the SPRING panels is made of PolyPropylene (more precisely we use a Block-Copolymer). The polypropylene heat exchanger of the DualSun Spring panel is composed of 188 canals, each with a 5mm exterior diameter, and two collectors which serve to distribute the liquid through the canals.
On the one hand, this material has been designed and tested to last 40 years in solar heating applications, which has been confirmed by a theoretical ageing study carried out by the CNRS PIMM laboratory, as well as by accelerated ageing tests at TÜV Rheinland.
On the other hand, this material has already been used for decades in similar types of applications.
For example, there are already thermal collectors for swimming pool heating that have been using the same material as the DualSun SPRING exchanger for decades.
That said, the DualSun exchanger is much more protected than a pool heating collector, so its longevity will be greater:
- The exchanger is positioned behind the photovoltaic laminate which constitutes a very effective anti-UV barrier (glass, EVA, backsheet, etc.).
- The temperatures in the DualSun SPRING exchanger are limited by the photovoltaic system, which also recovers energy. The DualSun heat exchanger thus achieves a lower stagnation temperature than the exchanger in full sunlight without PV laminate,
- Our recommendations on pressure are clear: if the panel does not exceed 1.5 bar in operation it will have an exceptional longevity.
This design is specific to DualSun and protected by international patents
What pressure test are DualSun SPRING panels subjected to before they are installed?
Each DualSun SPRING panel is tested at 1.5 times the maximum allowable operating pressure (see module data sheet in the DualSun documentation area) to verify their tightness.
- The protocol and test tools are standard and certified in the solar thermal industry.
- The measurement performed is a measurement of pressure variation in the panel over a given time, which is then converted and communicated as a leakage rate.
- The pressure variation allowed over the duration of the test corresponds to zero, +/- the detection threshold of the test bench, of the order of one ten thousandth of the atmospheric pressure in the heat exchanger (i.e. a high threshold equivalent to 3ml/min after conversion by PV=nRT in the test).