Experimental and theoretical calculation of efficiency for flat plate solar collectors in Erbil city. Periodicals of Engineering and Natural Sciences, [S. l.], v. 7, n. 2, 2019. DOI: 10.21533/pen.v7.i2.1583. Disponível em: https://pen.ius.edu.ba/index.php/pen/article/view/1583. Acesso em: 24 jun. 2026.