Performance of a “black” liquid flat-plate solar collector

A cost-effect, “black” liquid, flat-plate solar collector has been designed, and prototypes have been built and tested. In these collectors a highly absorbent “black” liquid flows in transparent channels and directly absorbs solar energy. The liquid is the hottest substance in the collector, and no metals are required anywhere in the design. The collector differs in the following ways from conventional flat-plate collectors: 1. 1. Solar radiation is absorbed directly by the black liquid without the need to heat any other structures within the collector. 2. 2. Lower heat losses are possible since energy is absorbed directly by the working fluid, and the flow pattern can be arranged so that the hottest spot is in the center of the collector away from all edges. As the fluid moves progressively inward toward the exit, which is located at the center of the collector, it will pick up some of the heat loss along the radial direction. 3. 3. Lower cost may be possible since no metal is required in construction and only glass and/or plastic need be used in addition to the insulation and frame. The absence of metal should eliminate all corrosion problems. 4. 4. New avenues of research are opened up by the use of black liquids: an entirely new class of materials are available which may aid in finding inexpensive, durable absorbers. 5. 5. New configurational arrangements are possible with the absence of metal absorbers. Experimental performance data for the black liquid collector is presented which compares favorably with other conventional flat-plate collectors.