In the present work, a new pattern-free heliostat layout optimization methodology based on the genetic algorithm is introduced. This method is developed to speed up the optimization process attempting to find the global optimum. The novel part of the proposed method is that multiple neighboring heliostats are optimized simultaneously with nearly no restrictions. The proposed methodology is tested with a standard performance analysis model that calculates the annual insolation weighted optical efficiency of the heliostat layout. In order to improve the flexibility of the shadowing and blocking for more complex cases, in which the reflecting polygon is divided into multiple polygons, we adopt the polygon clipping algorithm. With the proposed pattern-free optimization methodology, the insolation weighted optical efficiency of the PS10 heliostat layout has been improved by 0.6% point with 3.7% reduction in the heliostat field area. (C) 2017 Elsevier Ltd. All rights reserved.