In this paper, a new technique is proposed for design and optimization of a heliostat field. The unique aspect of the proposed approach is the code's ability to design the field with non-equal heliostats. It has been argued that designing a field of non-equal heliostats improves the energy and economic performance of a heliostat field. On this account, a new code called AINEH (analysis of implementation of non-equal heliostats) was developed to evaluate this idea. Firstly, the mathematical models developed in AINEH code are discussed by presenting the initial layout model, expansion technique, economic model, optimization approach, and objectives. Parametric analysis is carried out to identify the effect of different design parameters. Additionally, AINEH code is used to re-design PS10 by conducting a thermo-economic optimization. Energy optimization results show that PS10 annual weighted efficiency can be improved by 0.32% points from 68.91% to 69.23% in case of using AINEH code. In addition, field's levelized cost of energy (LCOE) can be reduced by 1.3 US$/MWh (6.5%) from 19.9 US$/MWh to 18.6 US$/MWh. (C) 2018 Elsevier Ltd. All rights reserved.