Development and performance analysis of compound parabolic solar concentrators with reduced gap losses - oversized reflector

A severe energy shortage already exists in many parts of the developing wor ld. In an attempt to find a technical solution, several solar energy collec tion technologies have been developed. A system has been designed to use co mpound parabolic concentrating collectors to collect solar energy and to ge nerate steam. A compound parabolic concentrator (CPC) profile with oversize d reflector and thereby reduced gap losses was designed with a half-accepta nce angle of 23.5 degrees for a tubular absorber of OD 19 mm. Five troughs fabricated with a fiberglass substrate pasted over with UV stabilized self- adhesive aluminized polyester foil having high specular reflectivity joined together side by side make the CPC module with aperture area of 0.72 m(2). Copper tubes coated with NALSUN selective coatings and enclosed by borosil icate glass envelopes act as absorbers. The reflector-absorber assembly pla ced in a single glazed glass wool insulated wooden box forms the CPC collec tor. Using water as heat transfer fluid, efficiency tests were conducted wi th different inlet temperatures. Even at high temperature, the system opera tes with a reasonably high efficiency of 50%. In situ steam generation test ing was also conducted. The fabricated CPC collector was used for steam coo king by connecting it to a pressure cooker. Cooking tests were conducted an d the results are compared with earlier works. This cooker unites the chara cteristics of reflector cookers, steam cookers, pressure cookers and heat a ccumulating solar cookers. The fabricated CPC can be of immense and wide sp read use for rural applications, such as water heating, steam cooking and s terilization. (C) 2001 Elsevier Science Ltd. All rights reserved.