Periodic Reporting for period 2 - SUNSON (Concentrated Solar energy storage at Ultra-high temperatures aNd Solid-state cONversion)
Periodo di rendicontazione: 2024-06-01 al 2025-05-31
SUNSON (Sun’s Son) is an ambitious European project aiming to develop a new generation of ultra-compact and efficient concentrated solar power (CSP) systems capable of operating at temperatures above 1200 °C. Its core goal is to enable high-efficiency solar energy storage and conversion, addressing one of the major challenges in the renewable energy sector: delivering dispatchable, clean electricity independent of sunlight availability.
The project integrates three key technologies into a single modular system—the SUNSON-BOX:
1) Advanced optics for precise solar concentration,
2) High-temperature thermal storage using innovative phase change materials (PCMs), and
3) Thermophotovoltaic (TPV) converters for solid-state power generation.
SUNSON also develops a digital Decision Support System (SUNSON-Tool) combining physical models and AI to optimize system design, performance, and integration with energy demand profiles.
With the promise of higher efficiencies, reduced system size, and scalable design, SUNSON aims to revolutionize solar thermal power generation and support the transition to a sustainable, zero-emissions energy future.
The project integrates three key technologies into a single modular system—the SUNSON-BOX:
1) Advanced optics for precise solar concentration,
2) High-temperature thermal storage using innovative phase change materials (PCMs), and
3) Thermophotovoltaic (TPV) converters for solid-state power generation.
SUNSON also develops a digital Decision Support System (SUNSON-Tool) combining physical models and AI to optimize system design, performance, and integration with energy demand profiles.
With the promise of higher efficiencies, reduced system size, and scalable design, SUNSON aims to revolutionize solar thermal power generation and support the transition to a sustainable, zero-emissions energy future.
During the second reporting period, the SUNSON consortium advanced significantly in the development of its innovative high-temperature solar-to-electricity system, progressing through key technical and scientific milestones across the different Work Packages.
WP2 focused on developing the SUNSON-Tool, a digital decision support system that integrates physical and mathematical models of the SUNSON-Box components. The team completed multiphysical modelling of solar optics, thermal energy storage, and TPV conversion, and integrated machine learning algorithms for short- and long-term solar radiation forecasting. A multidisciplinary design optimization (MDO) module was also implemented, enabling flexible system simulations tailored to various energy demand scenarios and supporting future scale-up analysis.
WP3 addressed the solar-to-heat conversion and thermal energy storage subsystems. The modular beam-splitting optics were fully designed to generate four equal focal points for improved flux distribution in beam-down CSP configurations, and their fabrication is underway. For the thermal storage system, two Fe-Si alloy PCMs were finalized, both demonstrating high latent heat capacities (>1 MWh/m³). Crucibles made of graphite with h-BN coatings were successfully tested through 100 thermal cycles between 1100 °C and 1300 °C, showing excellent thermal and chemical stability.
WP4 focused on developing the thermophotovoltaic (TPV) generator. Thin film InGaAs TPV cells achieved 25% conversion efficiency at 1704 °C and power densities of 3–4 W/cm² at 1797 °C. However, yields remained low due to wafer size constraints. A key mitigation step involved switching to 4-inch epitaxial wafers, significantly improving yields. Integration of InGaAs TPV cells has begun, and module assembly techniques are under development.
WP5 made progress toward assembling the SUNSON-Box prototype, a highly compact and modular CSP system. The detailed mechanical and thermal design integrates a solar absorber, PCM crucible, and TPV converter within a structure optimized for thermal efficiency and operational flexibility. The prototype supports four distinct operating modes (including charge, discharge, and storage) via mechanical decoupling. Manufacturing of components is ongoing, and integration at the PSA Solar Furnace is being prepared. A dedicated movable rig and support infrastructure (e.g. argon flushing, water cooling, remote control) have been planned to facilitate full-system demonstration under concentrated solar input.
WP6 supported the technical development with ongoing sustainability and techno-economic assessments. Life Cycle Inventory (LCI) data for all subsystems were compiled, and the initial Life Cycle Assessment (LCA) and Life Cycle Cost (LCC) evaluations were completed at TRL4. Energy and exergy analyses have been updated to reflect the latest system configurations. These results are helping guide design improvements and inform the cost-effectiveness and emissions reduction potential of the SUNSON innovations.
WP2 focused on developing the SUNSON-Tool, a digital decision support system that integrates physical and mathematical models of the SUNSON-Box components. The team completed multiphysical modelling of solar optics, thermal energy storage, and TPV conversion, and integrated machine learning algorithms for short- and long-term solar radiation forecasting. A multidisciplinary design optimization (MDO) module was also implemented, enabling flexible system simulations tailored to various energy demand scenarios and supporting future scale-up analysis.
WP3 addressed the solar-to-heat conversion and thermal energy storage subsystems. The modular beam-splitting optics were fully designed to generate four equal focal points for improved flux distribution in beam-down CSP configurations, and their fabrication is underway. For the thermal storage system, two Fe-Si alloy PCMs were finalized, both demonstrating high latent heat capacities (>1 MWh/m³). Crucibles made of graphite with h-BN coatings were successfully tested through 100 thermal cycles between 1100 °C and 1300 °C, showing excellent thermal and chemical stability.
WP4 focused on developing the thermophotovoltaic (TPV) generator. Thin film InGaAs TPV cells achieved 25% conversion efficiency at 1704 °C and power densities of 3–4 W/cm² at 1797 °C. However, yields remained low due to wafer size constraints. A key mitigation step involved switching to 4-inch epitaxial wafers, significantly improving yields. Integration of InGaAs TPV cells has begun, and module assembly techniques are under development.
WP5 made progress toward assembling the SUNSON-Box prototype, a highly compact and modular CSP system. The detailed mechanical and thermal design integrates a solar absorber, PCM crucible, and TPV converter within a structure optimized for thermal efficiency and operational flexibility. The prototype supports four distinct operating modes (including charge, discharge, and storage) via mechanical decoupling. Manufacturing of components is ongoing, and integration at the PSA Solar Furnace is being prepared. A dedicated movable rig and support infrastructure (e.g. argon flushing, water cooling, remote control) have been planned to facilitate full-system demonstration under concentrated solar input.
WP6 supported the technical development with ongoing sustainability and techno-economic assessments. Life Cycle Inventory (LCI) data for all subsystems were compiled, and the initial Life Cycle Assessment (LCA) and Life Cycle Cost (LCC) evaluations were completed at TRL4. Energy and exergy analyses have been updated to reflect the latest system configurations. These results are helping guide design improvements and inform the cost-effectiveness and emissions reduction potential of the SUNSON innovations.
The SUNSON project has delivered promising results across all core technological domains, validating the feasibility of a novel, compact solar-to-electricity system that integrates concentrated solar power (CSP), high-temperature thermal energy storage (TES) using phase change materials (PCMs), and thermophotovoltaic (TPV) conversion.
Thermophotovoltaics: The development of front/rear contact InGaAs TPV cells has achieved up to 25% electrical efficiency at 1704 °C, with power densities exceeding 3 W/cm². Although initial fabrication challenges limited yield, the switch to 4-inch wafers has increased manufacturing yield, demonstrating clear scalability potential.
Thermal Energy Storage: Two Fe-Si alloy PCMs were validated, both offering >1 MWh/m³ energy density and stable performance over 100 thermal cycles. These materials are geopolitically secure and economically viable, offering a compelling alternative to lithium- or boron-based solutions.
CSP Optics: The modular beam-splitting optical system enables simultaneous illumination of four absorber units with uniform flux distribution—critical for scaling up modular solar fields.
System Integration: The SUNSON-Box prototype demonstrates a 10× size reduction compared to conventional CSP-TES systems, combining high compactness, modularity, and operational flexibility.
Digital Twin and DSS Tool: The SUNSON-Tool integrates physical models and machine learning to simulate performance, optimize configuration, and support decision-making for various use cases. This software is a key asset for system design, replication, and eventual market deployment.
Thermophotovoltaics: The development of front/rear contact InGaAs TPV cells has achieved up to 25% electrical efficiency at 1704 °C, with power densities exceeding 3 W/cm². Although initial fabrication challenges limited yield, the switch to 4-inch wafers has increased manufacturing yield, demonstrating clear scalability potential.
Thermal Energy Storage: Two Fe-Si alloy PCMs were validated, both offering >1 MWh/m³ energy density and stable performance over 100 thermal cycles. These materials are geopolitically secure and economically viable, offering a compelling alternative to lithium- or boron-based solutions.
CSP Optics: The modular beam-splitting optical system enables simultaneous illumination of four absorber units with uniform flux distribution—critical for scaling up modular solar fields.
System Integration: The SUNSON-Box prototype demonstrates a 10× size reduction compared to conventional CSP-TES systems, combining high compactness, modularity, and operational flexibility.
Digital Twin and DSS Tool: The SUNSON-Tool integrates physical models and machine learning to simulate performance, optimize configuration, and support decision-making for various use cases. This software is a key asset for system design, replication, and eventual market deployment.