A concentrating photovoltaic wall element, including Cu(In, Ga)Se-2-based modules, aluminum reflectors, and an insulation for building integration, has been developed and evaluated. The geometric concentration ratio of the system is about 3 x. However, the measured maximum electric power from the modules is only 1.9 times that of identical vertical modules without reflectors, due to optical losses and a decrease in fill-factor from 0.6 to 0.5 under concentrated light. The optical efficiency of the system is 76% at an effective solar height of 40degrees. (C) 2002 Elsevier Science B.V. All rights reserved.