Slag as an Inventory Material for Heat Storage in a Concentrated Solar Tower Power Plant: Design Studies and Systematic Comparative Assessment

Abstract

Featured Application: Concentrated solar power (CSP) plant with open volumetric receiver.Abstract: By using metallurgical slag from an electric arc furnace that is otherwise not recycled but deposited as an inventory material in thermal energy storage for concentrated solar power plants, it is possible to make a significant step forward in two transformation processes: energy and raw materials. As this type of slag has not been considered as an inventory material for this purpose, it is important to clarify fundamental questions about this low-cost material and its storage design. In this paper, design studies of slag-based thermal energy storage are carried out. Different slag-specific design concepts are developed, calculated and evaluated by a method based on established management tools. Finally, concepts for further investigations are defined. The highest aptitude value and the lowest risk value are achieved by the vertical storage design with axial flow direction. Therefore, it is taken as the lead concept and will be considered in complete detail in further research. Also, a closer look, but not as detailed as the lead concept, is taken at the horizontal storage with axial flow and the vertical storage with radial flow direction.In CSP plants, molten salt technologies have been extensively deployed in CSP applications for the storage of thermal energy prior to steam or electricity generation. An example among many is the Solana power plant with 280 MWe and a storage system able to supply full power for six hours. [2] The technology of regenerator-type storage is less developed, but has the potential for higher efficiency and lower costs. In particular, the application of regenerators in CSP power plants with an open volumetric receiver seems to be a promising approach, as shown in Figure 1.

Experimental Studies on Thermal Performance and Thermo-Structural Stability of Steelmaking Slag as Inventory Material for Thermal Energy Storage

“…Another distinguishing feature is the flow direction, which is divided into axial, radial or meander-shaped. Further information, especially the pros and cons of each arrangement is given in [22]. Krüger et al [22] set up simplified continuous solid phase models, based on the Λ-Π method to obtain an initial estimation of the thermal design and heat storage dimensions.…”

“…Further information, especially the pros and cons of each arrangement is given in [22]. Krüger et al [22] set up simplified continuous solid phase models, based on the Λ-Π method to obtain an initial estimation of the thermal design and heat storage dimensions. The basics of the method are described in [25,26].…”

“…It was taken as the lead concept and is investigated in detail in further research. The stepby-step implementation of the method as well as detailed results for the individual TES designs are given in [22]. The entire design process includes the development of various possible TES designs, their calculation and evaluation using established management tools.…”

“…CSP plant specifications used as boundary conditions for the TES design consideration and the slag material properties are given in Table 1. Krüger et al [22] applied management tools normally used in production development in order to identify a lead concept. This includes an aptitude and risk analysis based on the quality function deployment (QFD) method.…”

“…The European project REslag investigates the use of a slag pebble inventory in regenerator-based TES systems further [21]. Within this project, Krüger et al [22,23] already presented the basic work of lead design identification and the investigation of material and thermomechanical aspects. First performance studies as well as experimental results are given by Haunstetter et al in [24].However, there are still open questions regarding the thermal performance and thermo-structural stability of the slag pebble inventory under cyclic temperature load.…”