Periodic Reporting for period 1 - ASTERIx-CAESar (AIR-BASED SOLAR THERMAL ELECTRICITY FOR EFFICIENT RENEWABLE ENERGY INTEGRATION & COMPRESSED AIR ENERGY STORAGE)
Période du rapport: 2023-10-01 au 2025-01-31
The ongoing renewable energy revolution, i.e. the ever rising fraction of non-dispatchable renewable power generation, is dramatically changing the way of power generation. A key requirement for the efficient operation of the future energy system is massive energy storage on the one hand, and highly flexible power generation on the other. It is clear that the future’s ideal power plant needs to provide “adaptive” power generation, being able to generate power, when required by the grid, and also to store energy efficiently, when electricity demand is low, but renewable energy is available in excess (e.g. from PV, or wind). Therefore, it is mandatory that future CSP plants implement efficient electrical energy storage, in addition to, or in combination with thermal energy storage (TES) in order to stabilize the power grid. Future “adaptive” CSP plants must store energy during periods of high renewable output and low demand (low price periods), in order to dispatch electricity during hours of high demand (high price periods), representing the crucial “magic potion” in order implement a future 100% renewable energy system.
The ASTERIx-CAESar project focuses on a novel solution, an innovative hybrid CSP – Compressed Air Energy Storage (CAES) combined cycle power plant configuration that provides very competitive electrical energy storage technology (“the magic potion”) and a break-through in solar-to-electric energy conversion efficiency. A sophisticated set of features of both technologies make the approach highly attractive, compared to state-of-the-art CSP solutions.
The main development will cover: (i) an advanced high-efficiency solar receiver, (ii) optical sensors and AI-based solar flux control, (iii) optimized CAES with heat exchangers and compressor/expander detailed designs and (iv) innovative integration of desalination. The proposed technology is set forth by an interdisciplinary partnership spanning the entire CSP value chain. Targeting a TRL of 6-7, the ASTERIx-CAESar concept will be validated with a demonstration scale prototype of up to 480 kWth.
The ASTERIx-CAESar project focuses on a novel solution, an innovative hybrid CSP – Compressed Air Energy Storage (CAES) combined cycle power plant configuration that provides very competitive electrical energy storage technology (“the magic potion”) and a break-through in solar-to-electric energy conversion efficiency. A sophisticated set of features of both technologies make the approach highly attractive, compared to state-of-the-art CSP solutions.
The main development will cover: (i) an advanced high-efficiency solar receiver, (ii) optical sensors and AI-based solar flux control, (iii) optimized CAES with heat exchangers and compressor/expander detailed designs and (iv) innovative integration of desalination. The proposed technology is set forth by an interdisciplinary partnership spanning the entire CSP value chain. Targeting a TRL of 6-7, the ASTERIx-CAESar concept will be validated with a demonstration scale prototype of up to 480 kWth.
WP1 – Concept definition and Techno-economic Optimisation:
Since the project start, the WP1 working group has been focused on defining all main power plant working parameters, such as the optimal charging and discharging times according to power grid demands, maximum CAES pressure, CAES vessel design and design parameters of compressor train and expansion train. A detailed system-level performance model has been developed in Modelica, which allows the performance assessment and optimisation under different boundary conditions.
On the other hand, experimental testing will be done at different scales. The working group will test small solar absorbers (12x12 cm) in the solar furnace at CIEMAT-PSA. Then, larger absorber samples (25x25 cm) will be tested at the solar tower at IMDEA. Finally, during the last project year, a 300 kWth receiver with approximately 1 m2 of aperture area will be tested at a solar tower at CIEMAT-PSA. This receiver will power a hot air turbine that will be connected to a small-scale CAES unit, providing between 1 or 2 hours of nominal turbine mass flow. During the first project year, all prototypes have been defined and specified in detail.
WP2 – Solar Receiver Development:
The CAPTure receiver technology will be further developed considering an advanced ceramic composite material (developed by Walter E.C. Pritzkow Spezialkeramik). The receiver will be tested at different scales from 50 to 300 kWth.
WP3 – Advanced Heat Exchangers:
The ASTERIx-CAESar plant concept requires two separate heat transfer systems: a Low Temperature Heat Exchanger (LTHE) system to carry out the intercooled/ aftercooled compression, and the High Temperature Heat Exchanger (HTHE) system to heat and re-heat the compressed air before the expansion. For both systems, two different concepts will be explored: the classic recuperative concept, where heat transfer occurs between streams separated by a heat transfer surface, and the innovative regenerative concept, where air is cooled/heated in a single vessel by passing through a porous heat storage medium.
WP4 – Advanced CAES and power cycle development and Optimisation:
WP4 is responsible for the development of turbomachinery and the associated integrated systems in ASTERIx-CAESar. This implies three main modules (islands) of the facility: the compression train charging the storage system (whether underground or on surface), the expansion train converting the mechanical (pressurised air) and thermal (high temperature storage medium) energy stored in the system into electricity, and bottoming heat recovery system harvesting any remaining thermal energy downstream of the expanders to produce additional electric power.
WP5 – Automatization and improved plant operation and monitoring via AI methods:
WP5 addresses three main activities:
- High-accuracy & high-precision aiming strategy generation method enhanced with artificial intelligence algorithms. - Advanced optical sensors for monitoring high-concentration solar thermal systems has focused on the use of optical fibers. - AI-based heliostat tracking control system for low-cost operation requires an intensive campaign to collect and label images to store a comprehensive training and validation dataset, enabling improved model performance and greater generalisation across diverse conditions.
WP6 – Validation & Demonstration of receiver and power cycle:
Within the framework of WP6, significant progress has been made in evaluating the thermal behaviour and scaling up the ASTERIx-CAESar solar absorbers and complete prototype. The work package, aimed at validating the concept under real-world conditions, is currently advancing through its initial tasks. A key development in this task involves collaboration between APRIA and CIEMAT on designing a reverse osmosis (RO) desalination unit powered by compressed air from the CAES system.
Since the project start, the WP1 working group has been focused on defining all main power plant working parameters, such as the optimal charging and discharging times according to power grid demands, maximum CAES pressure, CAES vessel design and design parameters of compressor train and expansion train. A detailed system-level performance model has been developed in Modelica, which allows the performance assessment and optimisation under different boundary conditions.
On the other hand, experimental testing will be done at different scales. The working group will test small solar absorbers (12x12 cm) in the solar furnace at CIEMAT-PSA. Then, larger absorber samples (25x25 cm) will be tested at the solar tower at IMDEA. Finally, during the last project year, a 300 kWth receiver with approximately 1 m2 of aperture area will be tested at a solar tower at CIEMAT-PSA. This receiver will power a hot air turbine that will be connected to a small-scale CAES unit, providing between 1 or 2 hours of nominal turbine mass flow. During the first project year, all prototypes have been defined and specified in detail.
WP2 – Solar Receiver Development:
The CAPTure receiver technology will be further developed considering an advanced ceramic composite material (developed by Walter E.C. Pritzkow Spezialkeramik). The receiver will be tested at different scales from 50 to 300 kWth.
WP3 – Advanced Heat Exchangers:
The ASTERIx-CAESar plant concept requires two separate heat transfer systems: a Low Temperature Heat Exchanger (LTHE) system to carry out the intercooled/ aftercooled compression, and the High Temperature Heat Exchanger (HTHE) system to heat and re-heat the compressed air before the expansion. For both systems, two different concepts will be explored: the classic recuperative concept, where heat transfer occurs between streams separated by a heat transfer surface, and the innovative regenerative concept, where air is cooled/heated in a single vessel by passing through a porous heat storage medium.
WP4 – Advanced CAES and power cycle development and Optimisation:
WP4 is responsible for the development of turbomachinery and the associated integrated systems in ASTERIx-CAESar. This implies three main modules (islands) of the facility: the compression train charging the storage system (whether underground or on surface), the expansion train converting the mechanical (pressurised air) and thermal (high temperature storage medium) energy stored in the system into electricity, and bottoming heat recovery system harvesting any remaining thermal energy downstream of the expanders to produce additional electric power.
WP5 – Automatization and improved plant operation and monitoring via AI methods:
WP5 addresses three main activities:
- High-accuracy & high-precision aiming strategy generation method enhanced with artificial intelligence algorithms. - Advanced optical sensors for monitoring high-concentration solar thermal systems has focused on the use of optical fibers. - AI-based heliostat tracking control system for low-cost operation requires an intensive campaign to collect and label images to store a comprehensive training and validation dataset, enabling improved model performance and greater generalisation across diverse conditions.
WP6 – Validation & Demonstration of receiver and power cycle:
Within the framework of WP6, significant progress has been made in evaluating the thermal behaviour and scaling up the ASTERIx-CAESar solar absorbers and complete prototype. The work package, aimed at validating the concept under real-world conditions, is currently advancing through its initial tasks. A key development in this task involves collaboration between APRIA and CIEMAT on designing a reverse osmosis (RO) desalination unit powered by compressed air from the CAES system.
In WP1 the ASTERIx-CAESar plant concept optimization is ongoing. Preliminar performance numbers of the plant are the following:
- Round-Trip-Efficiency (RTE): 43.9%
- Power plant efficiency (eta cycle): 40.1%
- Electricity production-to-consumed ratio (eRTE): 107.3%
- Solar-to-thermal efficiency (eta st): 60.9%
- Ratio of auxiliary consumptions: 6.1%
In WP2 the CAPTure volumetric receiver concept is being developed further. High-flux solar furnace testing confirmed expected performance, applying an advanced solar absorber manufacturing process better suited for replication in higher numbers.
In WP3 heat exchanger designs are being optimized. A particular innovation is the application of heat recovery steam generator design concepts in air/air heat exchangers.
In WP4 taylored compressor and expander designs are developed that best fit the specific operating conditions.
In WP5 advanced aiming point strategies are being developed and tested. Additionally, fiber-optic sensors are in development for solar flux and temperature measurement. Furthermore, an AI-based heliostat calibration system is in development and being tested.
In WP6 solar furnace testing of absorber samples is performed. Additionally, the CAPTure H2020 prototype is being modified in order to demonstrate the ASTERIx-CAESar concept in the relevant environment.
- Round-Trip-Efficiency (RTE): 43.9%
- Power plant efficiency (eta cycle): 40.1%
- Electricity production-to-consumed ratio (eRTE): 107.3%
- Solar-to-thermal efficiency (eta st): 60.9%
- Ratio of auxiliary consumptions: 6.1%
In WP2 the CAPTure volumetric receiver concept is being developed further. High-flux solar furnace testing confirmed expected performance, applying an advanced solar absorber manufacturing process better suited for replication in higher numbers.
In WP3 heat exchanger designs are being optimized. A particular innovation is the application of heat recovery steam generator design concepts in air/air heat exchangers.
In WP4 taylored compressor and expander designs are developed that best fit the specific operating conditions.
In WP5 advanced aiming point strategies are being developed and tested. Additionally, fiber-optic sensors are in development for solar flux and temperature measurement. Furthermore, an AI-based heliostat calibration system is in development and being tested.
In WP6 solar furnace testing of absorber samples is performed. Additionally, the CAPTure H2020 prototype is being modified in order to demonstrate the ASTERIx-CAESar concept in the relevant environment.