La present tesis s’enmarca en el camp/sector de l’emmagatzematge d’energia termica, concretament en el proces de disseny i optimitzacio que comporta el desenvolupament d’una tecnologia d’emmagatzematge termic. Per aquest fi s’han dissenyat, construit, operat i analitzat dues plantes prototip, la primera d’elles situada a la Universitat de Lleida amb una capacitate de 66 kWhth i la segona situada a la plataforma Solcar d’Abengoa, amb 8m5 MWhth. Al llarg d’aquesta tesis, es mostra el proces d’analisi, estudi i optimitzacio realitzat per permetre desenvolupar els sistemes d’emmagatzematge termic amb sals foses desde la seva etapa inicial de desenvolupament y la seva extrapolacio a dissenys comercials, permetent el desenvolupament de tecnologies d’emmagatzematge termic que ajudin a reduir els costs i a augmentar l’eficiencia de les plantes de generacio de concentracio solar amb un objectiu clar: que l’electricitat d’origen solar sigui competitiva enfront a les plantes fossils en l’horit...

Esta obra se distribuye con la licencia Creative Commons Reconocimiento-NoComercial-SinObraDerivada 4.0 Internacional (CC BY-NC-ND 4.0.) Ciclo de mejora en el estudio de la gestionabilidad de la tecnología termosolar cilindroparabólica en el mercado energético Cycle of improvement in the study of the dispatchability of the parabolic trough technology in the energy market

Industries with fast-developing technologies and knowledge-intensive business services rely on the development of scientific knowledge for their growth. This is also true in the renewable energy industry such as in concentrating solar power (CSP) plants, which have undergone intense development and expansion in the last two decades. Yet knowledge generation is not sufficient; its dissemination and internalization by the industry is indispensable for new product development. This paper contributes to providing empirical evidence on the known link between knowledge development and firm growth. In 10 years the cost of electricity produced through CSP has decreased five-fold. This decrease has only been possible due to innovation projects developed through a complex network of research and development (R&D) collaborations and intense investment, both public and (to a greater extent) private. The development and construction of pilot plants and demonstration facilities are shown to be ke...

Despite the big deployment of concentrating solar power (CSP) plants, their environmental evaluation is still a pending issue. In this paper, a detailed life cycle assessment (LCA) of a CSP tower plant with molten salts storage in a baseload configuration is carried out and compared with a reference CSP plant without storage. Results show that the plant with storage has a lower environmental impact due to the lower operational impact. The dependence on grid electricity in a CSP tower plant without storage increases its operation stage impact. The impact of the manufacturing and disposal stage is similar in both plants. When analyzed in detail, the solar field system and the thermal energy storage (TES) and heat transfer fluid (HTF) systems are the ones with higher impact. Within the storage system, the molten salts are those with higher impact. Therefore, in this study the impact of the origin of the salts is evaluated, showing that when the salts come from mines their impact is low...

Postmortem tests were performed over components removed from the TES-PS10 pilot plant after almost four years of continuous operation being exposed to solar salts under representative commercial operation conditions. Accordingly, corrosion performance of plates sections extracted from both storage tanks and samples cut from the hot molten salts pump were evaluated. Corrosion damage extension, oxides layers morphology, and corrosion products chemistry were analyzed by X-Ray diffraction, energy dispersive X-ray spectrometry, optical microscopy, and SEM. In addition to materials compatibility with molten salts, mechanical tests were carried out over the storage tanks plates sections. Although the corrosion damage extension over the plates extracted from storage tanks was low and the mechanical properties were according to the standard, some interesting observations were seen. For example, a sample extracted from the hot storage tank and exposed to intermittent contact with molten salts showed some areas characterized by the growth of a non-protective oxide scale. Moreover, localized corrosion with slight penetration through the base material was identified for all storage plates samples under evaluation. On the other hand, the molten salt pump parts under study showed adherent and uniform oxides layers without detecting corrosion-erosion phenomena. Some cavities were found in the discharge elbow, and these imperfections were associated to a bad metallurgical quality during casting. Summarizing, corrosion phenomena suffered by the components under evaluation could be corrected in future plants by applying the lessons learned discussed in this study. As conclusion, materials selection analyzed within this postmortem evaluation is valid from the corrosion point of view to be used in the design of commercial TES systems in PTC plants.

A387 Gr 91 Cr-Mo alloy corrosion compatibility with LiOH-KOH mixture was evaluated at 315 ºC (Test#1) and 360 ºC (Test#2). This alloy is studied for a techno-economical optimization of a steam-PCM heat exchanger proposed in the thermal energy storage (TES) system of a direct steam generation (DSG) facility. The corrosion damage was analyzed with visual inspection, optical microscopy, SEM, EDS and XRD, and corrosion rates were also calculated. A387 Gr 91 alloy generates protective oxide layers over base metal. Localized corrosion damages were not detected with these test conditions, while XRD and EDS profiles showed CrO and LiFeO2 as main corrosion products generated by this alloy. On the other hand, corrosion rates decrease with exposure time showing the passivation of the alloy. A387 Gr 91 corrosion performance was compared with A316L stainless steel, which was preliminary proposed by the authors in previous studies. In addition to corrosion performance, parameters such as cost, thermal properties, and mechanical properties are discussed. In conclusion, the use of A387 Gr 91 instead to A316L alloy for the construction of the steam-PCM heat exchanger involves the techno-economical optimization of the equipment.

h i g h l i g h t s A receiver-reactor model is presented and evaluated for boundary conditions of high flux solar concentrators. 27 High temperature solar fields have been optimized and flux data for the single receiver-reactors is presented. Definition of the array efficiency to quantify operational strategies. New strategies for the operation of receiver-reactor arrays improve the array efficiency by 46%. Receiver-reactor, solar concentrator and splitting plant performances are analyzed for a large set of configurations.

The circular economy can be promoted as a solution to support the sustainability market position of renewable energy systems. To design a circular and sustainable system, a structured approach is needed. The present study develops a methodology framework for sustainable circular system design (SCSD), aiming to assess thermal energy storage (TES) technologies from a sustainable perspective. To this end, a composite indicator, namely, environmental sustainability and circularity indicator (ESC) is provided. This indicator combines the environmental impacts of the TES system via the conduction of a life cycle assessment and its circulatory performance using the product-level material circularity indicator (MCI). The developed methodology is applied to a case study of high-temperature TES using molten salts as a part of a concentrated solar power plant. The SCSD embraces the analysis for the most relevant processes through proposing different ecological scenarios including, increasing the recycling rates (Modest Scenario), increasing the reuse rates (Medium Scenario), and a combination of both (Optimistic scenario). The circularity analysis showed that for the Modest, Medium and optimistic scenarios, the MCI moves from 20.6% for the current situation to 30.3%, 38.6%, and 46.4%, respectively. Accordingly, the optimistic scenario showed the most environmentally sustainable and circular scenario with ESC of 7.89%, whereas the Modest and Medium scenarios exhibited ESCs of 1.20% and 2.16%, respectively. A major obstacle for substantial improvement of the circulatory and ESC is the high share of unrecyclable molten salts in the system and therefore, any effort to improve the circulatory and the environmental benefits of this system can be reached by using more environmentally friendly alternative materials. The study concludes that the integration of reusing and recycling at the initial design should be sought in order to achieve a more environmentally sustainable and circular outcome.

Bibliometric analysis is a key study in order to elucidate the relevance of a research field. This study will point out the main evolution of the research performed in a topic considering the significance of each sub-topic. This study aims to perform a bibliometric analysis in concentrating solar power (CSP) technology. CSP had a first commercial wave between 1984 and 1995. Between 1995 and 2005 there was a period of commercial inactivity. Nevertheless, since 2005 CSP commercial implementation has been accelerating. This topic accounts for almost 6,300 publications on relevant journals and conference proceedings. Regional analysis showed that China is becoming the most relevant country for CSP research. The European Union still leads the development and will continue that way at least in the short term. Authors’ keyword evolution analysis has been useful as an indirect measure of technological maturity. It was found that conference proceedings have an important effect in the overall...

The aim of this study is to perform a review of the state-of-the-art of the reactors available in the literature, which are used for solid–gas reactions or thermal decomposition processes around 1000 °C that could be further implemented for thermochemical energy storage in CSP (concentrated solar power) plants, specifically for SPT (solar power tower) technology. Both direct and indirect systems can be implemented, with direct and closed systems being the most studied ones. Among direct and closed systems, the most used configuration is the stacked bed reactor, with the fixed bed reactor being the most frequent option. Out of all of the reactors studied, almost 70% are used for solid–gas chemical reactions. Few data are available regarding solar efficiency in most of the processes, and the available information indicates relatively low values. Chemical reaction efficiencies show better values, especially in the case of a fluidized bed reactor for solid–gas chemical reactions, and fi...

Current concentrated solar power (CSP) plants that operate at the highest temperature use molten salts as both heat transfer fluid (HTF) and thermal energy storage (TES) medium. Molten salts can reach up to 565°C before becoming chemically unstable and highly corrosive. This is one of the higher weaknesses of the technology. Solid particles have been proposed to overcome current working temperature limits, since the particle media can be stable for temperatures close to 1000°C. This work presents a review of solid particles candidates to be used as HTF and TES in CSP plants in open receivers. In addition, the interactions between solid particles with major system components are described in this review, for example, with TES system or heat exchanger. The parameters and properties of solid particles are identified from the material science point of view explaining their nature and the relation to the power plant efficiency and lifetime durability. Finally, future development is propo...