CPC variation of Sydney Tube

This is a variation on the Sydney type where a curved reflector is added to the back of the collector. The CPC stands for compound parabolic collector. This shape of reflector is capable of reflecting the sun's rays onto the central tubular absorber, even as the sun tracks across the sky. The aperature area of the collector is now the area of the reflector, but it can only lose heat through the vacuum tube and the manifold. For this reason, the thermal characteristics of this type of collector are excellent.

However while the refelctor and front of the tube may stay relatively clean for a number of years, dust and dirt tend to collect quite quickly on the back of the vacuum tubes. The collector will require regular (at least once per year) cleaning to maintain its output. One of the principal advantages of conventional vacuum tube collectors is that the wind can pass between the tubes, however with a reflector, increased wind loading is inevitable. It is also very important to verify that the reflectors are of good quality and tightly connected to minimise any rattle.