The Rutgers University Solar Energy System
combines three components: a porous concrete floor
over water storage, an energy saving blanket system,
and the solar collector shown in Figure 8–7. Although
the collector is inexpensive and uninsulated, it
collected an average of 50% of the available solar
energy during five years of research. Based on
construction costs, the entire system has a simple
pay-back of ten years. This period may be too long
to justify such an installation. Commercial solar heat
collectors require a much higher investment and have
much longer pay-back periods