Derivation of a tube solar collector transmittance for beam and diffuse radiation

Abstract

An expression of the total directional ray transmittance for a tube solar collector cover glass has been derived. Numerical hemispheric integration has been made for both beam and diffuse radiation. From the equivalent solar altitude angle we derived an expression that gives the equivalent altitude which can be used to estimate the average transmittance of a tubular cover glass using the mean beam transmittance expression.