Fritz Zaversky

This study presents the design and modeling of a first-of-its-kind experimental prototype integrating a high-temperature air-based Concentrated Solar Power (CSP) receiver with a diabatic Compressed Air Energy Storage (CAES) system. The prototype architecture and operating modes are defined, and a detailed thermal model of an Open Volumetric Air Receiver (OVAR) is developed and optimized, with emphasis on passive mass flow regulation under non-uniform solar flux. At nominal conditions (800 °C), the receiver achieves a predicted thermal efficiency of 81.6%. Transient simulations assess off-design dynamic behavior under realistic conditions, showing sensitivity to solar fluctuations and need for heliostat aiming strategies to reduce thermal non-uniformities and ensure stable outlet temperatures. For the CAES subsystem, a techno-economic analysis identifies high-pressure (300 bar) commercial gas cylinders as the most cost-effective aboveground storage solution, while discharge simulations yield a required storage volume of 4.8 m³. Finally, the complete piping and instrumentation diagram (P&ID) of the integrated system is presented, defining the experimental configuration. Overall, this work establishes the design basis for the future experimental demonstration of hybrid CAES-CSP operation for dispatchable renewable power generation and supports subsequent control development and scale-up analyses.

This paper focuses on the expansion train designed for the compressed air energy storage (CAES) concept under development in the EU-funded ASTERIx-CAESar project. The system integrates concentrated solar thermal energy from a high-temperature (800 °C) volumetric central-receiver into a hybrid storage configuration, combining low-temperature thermal energy storage (LT-TES) with compressed air storage (CAS) and high-temperature thermal energy storage (HT-TES). Electricity from the grid powers compressors during low-price periods, storing compressed air and recovering compression heat in LT-TES. Solar heat is stored in HT-TES. During discharge, preheaters and reheaters supply stored energy to the expansion train. Residual energy in the exhaust of the low-pressure turbine reduces round-trip efficiency; therefore, a bottoming waste heat recovery unit based on organic Rankine cycle (ORC) technology is assessed. Multiple air-cooled configurations are modeled for expander exit temperatures (EET) of 300–600 °C, using organic fluids and steam in subcritical, transcritical, and supercritical layouts. Scale effects on expander type (screw or axial) and isentropic efficiency are considered for capacities from 1 to 100 MWe. A multi-objective optimization of the bottoming cycle considers technical and economic aspects to maximize efficiency and heat recovery by adjusting vapor generator pressure/temperature. A global optimization of the expansion train identifies the optimal cycle configuration for each EET and scale, integrating the waste heat recovery system with a two-stage turbine. Recommendations to improve CAES system efficiency are provided.

The industrial sector is a significant energy consumer, primarily reliant on fossil fuels. Nevertheless, the potential of Concentrated Solar Power (CSP) technologies for decarbonizing the industry is promising and the challenges posed by variability in weather and seasons can be effectively addressed through the use of seasonal storage methods, such as Thermochemical Energy Storage (TCES). This study presents a dynamic lumped-capacitance model, implemented in Dymola, designed to simulate a continuous suspension reactor employing salt hydrates like calcium oxalate monohydrate/anhydrous. The model mainly comprised (i) heat balances, (ii) reaction kinetics for the dehydration process and (iii) a heat transfer model. Furthermore, the study delves into a comprehensive case study involving the integration of CSP and TCES into a dairy processing facility located in Spain, addressing both daily operational requirements and seasonal energy storage demands. The solar field, heating demand, and storage tanks are described in detail. The transient simulation results for July showcase the efficacy of the solar installation and sensible energy storage for day-to-day operations, resulting in a total solar contribution of 47.3%. Notably, the thermochemical energy stored during this period can cover 22.1% of the low-temperature energy demand in January. The study underscores the importance of TCES in sustainable energy systems and paves the way for further optimization, economic assessment, and expanded applications. Future work will focus on enhancing the model and incorporating additional thermochemical materials, supported by additional experimental data.

The CAPTure Open Volumetric Air Receiver (OVAR) design is based on ceramic stackable “free floating” absorber modules that form the receiver structure and avoid a complex metallic double membrane design. The novel receiver design has been validated at small-scale (15 kWth) at a solar simulator, as well as on the top of an experimental tower at 300 kWth, up to absorber module outlet temperatures above 900ºC. The novel OVAR concept is attractive for both the concentrated solar power (CSP) sector, as well as for high-temperature process heat supply. The thermal efficiency of the receiver concept is expected to be above 80% at outlet temperatures of 900ºC.

Kuwait is a country with great potential for concentrated solar power (CSP) due to its high solar resource. The current work analyzes the potential of the application of CSP technology in the country and its particularities. Specifically, the current work examines a CSP plant with parabolic trough collector (PTC) technology and how this technology is affected in its performance depending on the location (inland or coastal) and the refrigeration system (wet, dry, or seawater cooled). The modeling methodology is based on a two-step approach: first, the Rankine steam power cycle is modeled in detail in a state-of-the-art steady-state simulation environment, obtaining the performance of the power cycle for each cooling technology; second, the power cycle performance maps are integrated into a detailed transient system-level simulation model of the complete CSP plant in order to perform annual yield simulations for the different representative locations of the climate of Kuwait. These results provide valuable information on both the potential of this technology for its more immediate application such as electricity generation and other future applications such as the desalination of seawater where the location must necessarily be coastal.

This work presents a techno-economic parametric study of an innovative central receiver solar thermal power plant layout that applies the combined cycle (CC) as thermodynamic power cycle and a multi-tower solar field configuration together with open volumetric air receivers (OVARs). The topping gas turbine (GT) is powered by an air–air heat exchanger (two heat exchanger trains in the case of reheat). In order to provide dispatchability, a high-temperature thermocline TES system is placed upstream the gas turbine. The aim is threefold, (i) investigating whether the multi-tower concept has a techno-economic advantage with respect to conventional single-tower central receiver plants, (ii) indicating the techno-economic optimum power plant configuration, and (iii) benchmarking the techno-economic optimum of the CC plant against that of a conventional single-cycle Rankine steam plant with the same receiver and TES technology. It is concluded that the multi-tower configuration has a techno-economic advantage with respect to the conventional single-tower arrangement above a total nominal solar power level of about 150 MW. However, the benchmarking of the CC against a Rankine single-cycle power plant layout shows that the CC configuration has despite its higher solar-to-electric conversion efficiency a higher LCOE. The gain in electricity yield is not enough to outweigh the higher investment costs of the more complex CC plant layout.