MEDIUM-CONCENTRATION SOLAR TECHNOLOGY

Thermo-hydraulic studies of concentrated solar system with parabolic troughs collectors for direct steam generation (GeDiVa)


Partners: CIEMAT-PSA
Financed by: Spanish Ministry of Economy and Competitiveness (Proyectos de Investigación Fundamental no Orientada)
Reference: ENE2011-24777
Duration: January 2012 – December 2014

Motivation: Concentrated solar systems with parabolic troughs collectors for direct steam generation constitute a step forward in the improvement of conversion efficiency from solar to thermal energy in the temperature range between 110ºC and 500ºC, besides it is expected an important reduction of the solar field manufacturing costs using this type of technology mainly due to the elimination of some equipment currently installed in the concentrated solar power stations that have been connected to the grid during last years in Spain, where the heat transfer fluid used in the receivers of the parabolic troughs is a synthetic oil. The applications of this technology are mainly the electricity generation, industrial process heat, and solar heating and cooling.

The existence of different states of the fluid in the solar field complicates the modeling and simulation of the systems using this technology, due mainly to the difficulty which is found in the modeling and simulation of the phase transition of the two-phase flow in the tubes, where different flow patterns appear. There are many correlations in literature for the calculation of pressure drop in the tubes with two-phase water-steam flow, as well as for the calculation of convective heat transfer coefficient, and many of them are not suitable for tubes as those used in parabolic trough collectors subjected to radiation heat flux in the tube wall about 40 kW/m2. These difficulties have motivated the development of this research project.
Objectives:
To perform thermo-hydraulics studies of different configurations of solar field using several types of parabolic troughs commercially available that can work with pressurized water-steam as heat transfer fluid.
To elaborate a guide with recommendations regarding conversion efficiencies from solar to thermal energy achieved and pressure losses occurring in the solar field depending if its configuration and nominal working conditions are those that in the outlet of the solar field there is pressurized hot water, saturated steam (with different void fractions), or superheated steam.
To develop simulation tools, which have modular and flexible capabilities, with a complete library of components for this type of solar fields.
Selected publications: