DEVELOPMENT OF NEW PROCESSES FOR WELDING OF THERMAL AL-CU SOLAR ABSORBERS USING DIODE LASERS

摘要

Flat-plate solar collectors are favorable devices torngenerate heat from the energy of the sun. The centralrnpart of a collector, the solar absorber, is a front-coatedrnaluminum sheet with a copper tube fixed on the backrnside in order to transport heated liquid. Nowadays, thernabsorber is often fabricated by laser welding with twornflashlamp-pumped Nd:YAG lasers which provide highrnpeak pulse powers. A disadvantage of this procedure isrnthe high electrical energy consumption. Research onrnnew laser welding processes is aimed to reduce thernamount of energy required. Diode lasers allowrnprocessing with higher efficiency, due to a betterrnabsorption behavior of the aluminum sheet.rnAccordingly, two different processes have beenrndeveloped. The first one, using two laser sources inrnpulsed mode, is similar to the industrial process, butrnenables an extension of the spot welds in order tornincrease the joint strength. In contrast, the secondrnprocess requires only one laser source to weld the tubernon both sides, using a scanner system which isrnintegrated in a newly developed innovative laserrnprocessing head. By adopting these processes,rnsignificant energy savings during the production ofrnsolar absorbers can be achieved, ensuring high processrnreliability at the same time.