The known sorbent deactivation over calcium looping cycles is one of the main drawbacks of this technology for CO2 capture. Steam is often discussed to improve carbonation and calcination reactions, and can be easily removed from the gas streams by condensation. Even though its benefits have been already reported on the literature, a comprehensive overview of the steam mechanisms on these reactions is still lacking. The aim of this work is to underline the effects of steam addition on the gas atmosphere properties, as heat transfer and CO2 partial pressure, as a catalyst, on the pore structure, and lastly, on CO2 diffusion. According to the literature review, we can conclude that steam effects positively the carbonation and calcination reactions in an optimal range. These findings can give a guideline for further calcium looping experimental investigation and open possibilities for sorbent improvement.
High optical accuracy required for concentrating solar power (CSP) systems needs accurate metrology to assess mirror optical parameters. Researchers have developed a variety of CSP optical metrology systems, which include complex calculations and calibration terms. This raises the question: How do we know these methods’ accuracy? One approach is to compare metrology system measurements against a ground truth reference. An ideal ground truth reference is simple, inherently accurate, and easy to replicate. In this paper we seek ground truth references to enable CSP metrology developers to easily cross-check the accuracy of their systems. These fall into two broad categories: Ground truth methods and ground truth physical standards. We describe fundamentals and present several examples. This is an abbreviated version of a full-length detailed report [1].
The energy transition toward renewable sources and the decarbonization of the power sector represent both a strategic challenge and an opportunity for Chile due to its outstanding solar and wind resources. This study evaluates the technical and economic feasibility of hybrid renewable energy systems integrated with hydrogen technologies under a Small Distributed Generation Means (SDGM) scheme, where grid injection is limited to 9 MW. A photovoltaic–wind (PV-WT) system combined with electrolyzers (Proton Exchange Membrane Electrolyzer, PEME, and Alkaline Water Electrolyzer, AWE) and fuel cells (Proton Exchange Membrane Fuel Cell, PEMFC, and Alkaline Fuel Cell, AFC) is analyzed for green hydrogen production and utilization. Hourly simulations in Python model renewable generation, grid injection constraints, hydrogen production, storage, and reconversion. The complementarity between solar and wind resources improves generation stability and hydrogen production. Among the evaluated configurations, the PV-WT-AFC-AWE system in the coastal region achieved the best economic performance, with an LCOE of 106.29 USD/MWh, an LCOH of 7.60 USD/kg, an NPV of −3.7 million USD, and an IRR of 7.6%. In contrast, configurations including fuel cells (PV-WT-PEMFC-PEME) exhibited the poorest economic performance, indicating that hydrogen reconversion into electricity is not economically viable under the SDGM framework due to conversion inefficiencies, high capital costs, and low utilization factors. Overall, PV-WT-electrolyzer systems are technically viable, but their economic feasibility depends strongly on the final use of hydrogen, with direct hydrogen export emerging as the most promising pathway.
Heliostats can experience a wide range of operating temperatures, spanning from below -5°C to above 40°C. Yet many heliostat mirrors combine components of dissimilar materials, with different coefficients of thermal expansion (CTE). This may cause temperature-induced deformations, which can reduce optical accuracy. In this paper we assess the optical effect of temperature change for two different mirror designs: a metal-backed design and a glass sandwich design. We integrated an optical deflectometry system with a temperature-controlled environmental test chamber, and measured high-resolution slope maps of the two mirror designs over a wide range of temperatures. Our results indicate that changing temperature can significantly affect optical slope and consequent energy capture. Further, we found that mirror design structure can have a significant effect on susceptibility to optical change with temperature, with the glass-sandwich design showing much less temperature-induced change than the metal-backed mirror. We conclude with suggested design guidelines for reducing the effect of temperature on heliostat optical performance.
Thermochemical energy storage (TCES) is an emerging technology that aims to improve efficiency of high-temperature Concentrated Solar Power (CSP) systems. At the same time, the pool of materials for TCES at T = 900-1200oC remains very limited mainly due to poor cyclic stability. This work addresses the performance and cyclic stability of new SrCO3-based composites with CaCO3, Li2CO3, SnO2, MgAl2O4, and SnAl2O5. The composites were prepared by mechanical mixing and sol-gel methods, characterized by XRD analysis and tested under cycling at 1200 °C (decarbonation) and 900 °C (carbonation) by using TGA and DSC. The incorporation of additives generally improved cycling stability compared to pure SrCO3, although the effect on effective conversion depended on the additive composition. The SrSnO15 composite, consisting of SrCO3 and 15 wt. % of SnO2, achieved the highest performance, reaching an effective conversion 5.36 times greater than pure SrCO3 after nine cycles. In contrast, the SrSnAl20 and SrMgAl20 composites exhibited lower effective conversion rates but maintained stable cycling with asymptotic conversion trends, suggesting that further optimization of synthesis conditions may enhance their performance. X-ray diffraction analysis revealed the formation of secondary phases after cycling, including Sr3Al2O6, SrSnO3, and Sr2SnO4, indicating chemical interactions and phase evolution within the composites. These phase transformations may contribute to the improved cycling stability observed in the doped materials. Overall, the results highlight the potential of additive-modified SrCO3 composites as promising candidates for TCES applications in CSP systems.
