Abstract: A barrel-shaped solar roofing element consisting of a portion of a conical-shaped panel of a material such as PVC plastic formed by injection molding adapted for receiving an impingement of solar energy upon an outer surface thereof and constructed of insulative material having a relatively thin dimension, a passway extending throughout the panel for conduiting a heat exchanger fluid, the passway having a male coupling at one edge of the panel and a female coupling at a generally distal edge of the panel and constituting a fluid circuit, or at least a portion thereof, each of the male coupling and female coupling formed for interlocking with a complementary or mating kind of coupling of an adjacent panel.