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.

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.

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.