Why Copper Collectors

Aluminium is cheaper. Stainless steel is stronger. So why copper?

Copper has the second-highest thermal conductivity of any metal at 401 W/mK. Silver beats it at 429 W/mK, but nobody is building solar collectors from silver. Aluminium manages 237 W/mK. Stainless steel limps in at 16 W/mK.

For a solar thermal collector, where the entire job is to move heat from the absorber surface to the fluid in the risers, conductivity is everything. A copper riser conducts heat to the water roughly 25 times faster than a stainless steel one.

Copper also forms a protective patina that resists further corrosion. An all-copper system running plain water has a service life measured in decades.