Development of an innovative code for the design of thermodynamic solar power plants part A: Code description and test case Giampaolo Manzolini * , Andrea Giostri, Claudio Saccilotto, Paolo Silva, Ennio Macchi Politecnico di Milano, Dipartimento di Energia, Via Lambruschini 4, 20156 Milano, Italy 1 article info Article history: Received 1 September 2010 Accepted 30 December 2010 Available online 3 February 2011 Keywords: Parabolic trough simulation Concentrated solar plants Solar plant optimization abstract This paper presents an innovative code for predicting performances, as well as preliminary plant sizing and investment costs estimation, for different parabolic trough solar fields operating at nominal conditions. The code allows a preliminary design of the solar field lay-out, the sizing of the main components of the plant and the optimization of the steam cycle. The code, named PATTO (PArabolic Trough Thermodynamic Optimization), allows to separately calculate the thermal efficiency of parabolic trough systems in commerce as well as combination of components of various commercial systems, in order to exploit different technology solutions: combination of mirrors, receivers and supports. The code is flexible in terms of heat transfer fluid, temperature and pressure range. Regarding the power block, a conventional steam cycle with super-heater and re-heater sections and up to seven regenerative bleedings is adopted. In part A of the paper a detailed description of the code is presented, with cali- bration toward real applications and reference values found in literature. Part B reveals capability of the code in predicting performances of different solar technologies and their costs. Finally an innovative solar plant configuration is proposed. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Among renewable energies, solar energy could play a funda- mental role to satisfy the energy demand in countries with high solar radiation. In particular solar thermal power could easily cover the commercial demand for bulk electricity in the range of ten to hundreds MW, with relatively low land demand and predictable decreasing of costs in the near future. Moreover, this technology allows the adoption of a thermal storage with possible decoupling of the electricity production from the energy source. In solar thermal power plants the solar radiation is firstly con- verted into thermal energy through a concentrator, then into electricity through a thermodynamic cycle, usually a Rankine cycle. Depending on the type of concentrator, the solar power plants can be based on linear receivers (i.e. parabolic trough or Fresnel collectors), or point focus receivers, such as solar towers or para- bolic dish systems. Linear concentrators, mainly parabolic trough collectors, are currently the most proven solar thermal electric technology and are becoming the reference technology for commercial applications. Today, several companies work on parabolic trough systems such as Solel [1], Schott [2], Acciona [3], EuroTrough [4] and Archimede Solar Energy [5], just to mention some of them. Manufacturers offer various kinds of collectors, with different performances and temperature operating ranges. Solar thermal power plant costs are still high and mainly related to the solar field, so that R&D programs are mostly directed toward improving receiver performances, as well as decreasing their actual cost. The most used plant configuration involves indirect steam generation by means of a synthetic oil as a thermal fluid circulating in the solar field, even if other routes are being explored, such as using molten salts mixture as thermal fluid in collectors or in thermal storage [6], or Direct Steam Generation (DSG) plants [7], in which water is directly evaporated inside solar collectors. An innovative configuration, aiming to achieve better performances and lower costs will be presented in the second part of this work. The paper deals with the development and testing of an inno- vative code, named PATTO, (PArabolic Trough Thermodynamic Optimization) capable of (i) predicting the performance of solar trough based CSP plants under nominal conditions, (ii) carrying out a preliminary sizing of the overall plant, and of (iii) estimating investment costs of the main components of the system. The code is implemented in MS Visual Basic 6.0 with Excel spreadsheets as user interface for input and output data. With respect to other existing codes, in particular SAM developed by NREL [8], the software PATTO presented in this paper is limited to the evaluation at * Corresponding author. Tel.: þ39 (0)2 2399 3810. E-mail address: giampaolo.manzolini@polimi.it (G. Manzolini). 1 http://www.gecos.polimi.it. Contents lists available at ScienceDirect Renewable Energy journal homepage: www.elsevier.com/locate/renene 0960-1481/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.renene.2010.12.027 Renewable Energy 36 (2011) 1993e2003