1. GIT
Supercritical Steam cycle for Line-Focusing Solar Power Plants Luis Coco Enríquez, Javier Muñoz-Antón, José M. Martínez-Val Grupo de Investigaciones Termoenergéticas (GIT), ETSII-UPM
Abstract
Fossil Power Plants state of the art technology is aligned with Supercritical (650ºC 250 bar live steam) and even UltraSupercritical (760ºC 350 bar live steam) Balance Of Plants (BOP).
Sandia National Laboratories and Siemens Energy, Inc., confirmed the feasibility of adapting the Siemens turbine SST-900 for supercritical steam in concentrated solar power plants, see reference [1].
This study is focused on integrating a Line-Focusing, Parabolic or Linear Fresnel solar collectors with a Supercritical Rankine power cycle.
Direct Molten Salt
Two Heat Transfer Fluids were assessed with line-focusing, Parabolic or Linear Fresnel solar collectors:
- Direct Steam Generation.
- Direct Molten Salt (HITEC XL).
An innovative Direct Steam Generation
Solar Field configuration with steam compressors is proposed.
A fossil boiler for backing during transitory periods is recommended in both cases.
Direct Steam Generation
Supercritical Rankine Power Cycle (BOP)
● Molten Salt configuration provides higher net
Plant efficiency (~ 1 %) due to steam compressors
electrical consumption.
● Receiver material cost high impact Solar Field
capital investment cost:
Carbon Steel or T91 in Direct Steam Generation.
Austenitic Stainless steel in Molten Salt receivers.
Conclusions:
● Subcritical Rankine line-focusing solar
plants net efficiency up to ~40% (Turbine
inlet: 550ºC and 87.7 bar).
● Supercritical Rankine line-focusing solar
plants net efficiency up to 43-45% (Turbine
inlet: 550ºC and 260 bar).
● Net plant efficiency improvement due to:
a) Direct ReHeating stages (up to 3).
b) 7 Feed-water heaters+Deaerator.
● Solar collectors aperture area savings.
References:
[1] James E. Pacheco, Thorsten Wolf, Nishant Muley "Incorporating Supercritical Steam Turbines into Advanced Molten-Salt Power Tower Plants: Feasibility and performance” Sandia report, SAND , March 2013.