Flat plate solar collectors are the most common form of solar heating devices. In their most basic form, such collectors comprise a plurality of heat collection tubes on a black heat absorbing surface. Such a basic flat plate device is relatively inefficient and thereby requires an excessively large surface area to produce substantial quantities of heat.
Various techniques for increasing the efficiency of flat plate collectors have been proposed. Accordingly, in one such approach, a glass panel overlies the heat absorbing surface. Such a glass panel passes the ultra violet rays from the sun which are converted into heat energy. Most of the infrared radiation from the heat absorbing surface is reflected back to the surface by the glass panel, thereby increasing the precentage of the sun's energy converted into useful heat. Another known technique is to make the heat collection tubes integral with the heat absorbing surface to increase the heat transfer to water flowing in the heat collection tubes.
Techniques such as those outlined above and similar techniques may increase the efficiency of a flat plate solar collector to a level where sufficient heat is generated to accomplish various household heating and air conditioning requirements. However, the increase in the cost of materials for such complex flat plate solar collectors together with the incremental cost of installation renders the final product so expensive that such devices are frequently not cost effective as compared with conventional fuel heaters.
A further deficiency of prior art flat plate solar collectors is their inability to effectively respond over a wide range of incident sun angles. Such devices must be mounted and actuated so that they can follow the sun or must accept extremely low efficiencies during the extremes of sun travel. Additionally, in those flat plate solar collectors utilizing a glass panel to reduce radiation losses, there has been no effective mechanism for reducing convective and conductive heat losses from the solar panel.
Therefore, it is desirable to have a solar collector panel that is relatively inexpensive to manufacture and assemble and which provides for a highly efficient conversion of sun energy into heat and which transfers the converted heat efficiently to water flowing through the panel. Such a solar collector panel is particularly desirable where convective and conductive heat losses from the panel are minimized.