variavel0=<b>Carlos Antonio Silva Gomes</b> - c-gomes@bol.com.br Universidade Federal do Ceará
<b>Maria Eugênia Vieira da Silva</b> - eugenia@les.ufc.br Universidade Federal do Ceará
<b>Regio Davis Barros Alves</b> - solar09@les.ufc.br Universidade Federal do Ceará
<b>Klemens Schwarzer</b> -  Ingenieurbüro für Energie
<b>Abstract.</b> This work presents a comparative study of selective surfaces for solar collectors that are used in the centers with greater utilization of renewable energy. Temperature measurements and global and direct solar fluxes in the absorber plates as a function of time are presented. The samples were tested under the ambient conditions found in Fortaleza. The experimental values were used to determine the emissivity, after steady state energy balance were performed in the samples. The stagnation temperatures were also calculated and show the behavior of the samples. Microscopic analyses were also made (scanning microscopic electronic ) for each sample. The results clearly show the sample performances when exposed to solar radiation and that the procedure developed in this work can be used to determine an average value for the solar emissivity from simpler measurements.
<b>Keywords.</b> Solar Collectors, Emissivity, Solar Radiation.