In this paper, the problem of estimating the distributed profile of the temperature along the tube of a concentrated distributed solar collector from boundary measurements is addressed. A nonlinear observer is proposed based on a nonlinear integral transformation. The objective is to force the estimation error to follow some stable transport dynamics. Convergence conditions are derived in order to determine the observer gain ensuring the stabilization of the estimation error in a finite time. Numerical simulations are given to show the effectiveness of the proposed algorithm under different working conditions. (C) 2016, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.