Can solar tower plants withstand the operational flexibility of combined cycle plants?. (15th May 2022)

• Record Type: Journal Article
• Authors: González-Gómez, P.A.; Gómez-Hernández, J.; Ruiz, C.; Santana, D.
• Is Part Of: Applied energy. Volume 314(2022)
• Publication Date: 2022-05-15
• Subjects: Solar tower plant -- Load-following power plant -- Steam generator -- Cyclic fatigue analysis; ASME American Society of Mechanical Engineers -- CCPPs combined cycle power plants -- CSP concentrating solar power -- EV evaporator -- HTF heat transfer fluid -- HRSG heat recovery steam generators -- LC load change -- LCOE levelized cost of electricity -- PH preheater -- RH reheater -- SAM system advisor model -- SG steam generator -- STP solar tower plant -- SH superheater -- TEMA Tubular Exchanger Manufacturers Association; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2022.118951
• Languages: English
• ISSNs: 0306-2619

Abstract

Highlights: The reliability of the steam generator is key to reduce forced outages. The cost of the unplanned stops due to leakages balance the steam generator cost. Steam generator exchangers with a 20% extra area is a recommendable practice. An increase of the LCOE between 1.6 and 0.8% is obtained due to the cycling operation. Abstract: The aim of this work is to investigate the level of reliability of a 100 MWe solar tower plant operating as a load-following plant using actual operational data of combined cycle power plants. Despite the low cost, the steam generator has been identified as the main cause of unavailability of solar tower plants due to fatigue failures of tube-to-tubesheet joints, which can lead to steam/water leakage into the heat transfer fluid circuit, putting the plant performance at risk. A methodology based on the ASME code and EN standards is proposed to predict the fatigue failures of critical welded points of the steam generator, such as tube-to-tubesheet joints and other T-joints. The results show that the forced outages due to failures of the steam generator lead to an energy penalty that ranges over 230–453 GWh over the plant lifetime. The associated annual degradation rate ranges over 0.123–0.244%. Three tube leakage repair strategies are compared: tube-to-tubesheet weld crack repair, tube plugging and tube plugging with steam generator replacement. The latter strategy was shown to be the best practice because the lowest levelized cost of energy was obtained. In addition, the design of heat exchangers with a minimum of 20% extra area is highly recommended to not compromise the plant operation due to tube plugging. Last, the load-following operation of the solar tower plant increases the levelized cost of energy by approximately 1.6% in the case of tube repair and approximately 0.8% in the case of tube plugging with steam generator replacement.