Copper is the logical material for solar energy systems because:
* It has the best thermal conductivity of all engineering metals;
* It is highly resistant to both atmospheric and aqueous corrosion;
* It is easy to fabricate and to join by soldering or brazing;
* It has been used both for plumbing and for roofs since metals were first employed in those applications.
Copper's thermal advantages mean thinner copper sheet can collect the same heat as much thicker gages of aluminum or steel sheet, and copper collector tubes can be more widely spaced.
Copper's resistance to atmospheric corrosion is well demonstrated by its service in roofing and flashing. Unless attacked by the sulfur or nitrogen oxide exhausts from utilities or process industries, copper has withstood decades—even centuries—of weathering.
Copper resists hot water corrosion equally well. Properly sized to keep flow rates below those recommended in Pressure System Sizing, and properly installed, copper hot water systems are, for all practical purposes, completely resistant to corrosion.
The ease with which copper plumbing systems are joined by soldering needs no special emphasis. Sheet copper fabrication is equally recognized for its ease and simplicity.