Solar energy may be practically utilized directly through transformation into heat, electrical or chemical energy. We present a procedure to design a square facet concentrator for laboratory-scale research on medium-temperature thermal processes. The efficient conversion of solar radiation into heat at these temperature levels requires the use of concentrating solar collectors. Large concentrating dishes generally have a reflecting surface made up of a number of individual mirror panels (facets). Optical ray tracing is used to generate a system performance model. A square facet parabolic solar concentrator with realistic specularly surface and facet positioning accuracy will deliver up to 13.604 kW of radiative power over a 250 mm radius disk (receiver diameter) located in the focal plane on the focal length of 1500mmwith average concentrating ratio exceeding 1200. The Monte Carlo ray tracing method is used for analysis of the optical performance of the concentrator and to identify the set of geometric concentrator parameters that allow for flux characteristics suitable for medium and high-temperature applications. [Projekat Ministarstva nauke Republike Srbije, br. III42006: Research and development of energy and environmentally highly effective polygeneration systems based on renewable energy resources]