An experimental facility was developed to asses in situ the degradation of crystalline silicon solar cells, fabricated by the Solar Energy Group of the National Atomic Energy Commission (CNEA), by measuring the current-voltage characteristic curve. The cells were irradiated with 10 MeV protons and fluences between 10(8) and 10(13) p/cm(2), using an external beam of the linear tandem accelerator TANDAR, at CAC-CNEA. Furthermore, theoretical simulations were performed to establish the relation between the variation of the electrical parameters and the degradation of the lifetime of minority carriers in the base. The damage constant for 10 MeV proton irradiated silicon solar cells of n(+)-p-p(+) structure and 1 Omega cm base resistivity was determined. Finally, a proposal of a new model of radiation damage for silicon solar cells is discussed. (C) 2004 Elsevier B.V. All rights reserved.