Carbon Dioxide Power Cycle Research Articles

Mean-Line Design of a Supercritical CO2 Micro Axial Turbine

Supercritical carbon dioxide (sCO2) power cycles are promising candidates for concentrated-solar power and waste-heat recovery applications, having advantages of compact turbomachinery and high cycle efficiencies at heat-source temperature in the range of 400 to 800 ∘C. However, for distributed-scale systems (0.1–1.0 MW) the choice of turbomachinery type is unclear. Radial turbines are known to be an effective machine for micro-scale applications. Alternatively, feasible single-stage axial turbine designs could be achieved allowing for better heat transfer control and improved bearing life. Thus, the aim of this study is to investigate the design of a single-stage 100 kW sCO2 axial turbine through the identification of optimal turbine design parameters from both mechanical and aerodynamic performance perspectives. For this purpose, a preliminary design tool has been developed and refined by accounting for passage losses using loss models that are widely used for the design of turbomachinery operating with fluids such as air or steam. The designs were assessed for a turbine that runs at inlet conditions of 923 K, 170 bar, expansion ratio of 3 and shaft speeds of 150k, 200k and 250k RPM respectively. It was found that feasible single-stage designs could be achieved if the turbine is designed with a high loading coefficient and low flow coefficient. Moreover, a turbine with the lowest degree of reaction, over a specified range from 0 to 0.5, was found to achieve the highest efficiency and highest inlet rotor angles.

Potential of Supercritical Carbon Dioxide Power Cycles to Reduce the Levelised Cost of Electricity of Contemporary Concentrated Solar Power Plants

This paper provides an assessment of the expected Levelised Cost of Electricity enabled by Concentrated Solar Power plants based on Supercritical Carbon Dioxide (sCO 2 ) technology. A global approach is presented, relying on previous results by the authors in order to ascertain whether these innovative power cycles have the potential to achieve the very low costs of electricity reported in the literature. From a previous thermodynamic analysis of sCO 2 cycles, three layouts are shortlisted and their installation costs are compared prior to assessing the corresponding cost of electricity. Amongst them, the Transcritical layout is then discarded due to the virtually impossible implementation in locations with high ambient temperature. The remaining layouts, Allam and Partial Cooling are then modelled and their Levelised Cost of Electricity is calculated for a number of cases and two different locations in North America. Each case is characterised by a different dispatch control scheme and set of financial assumptions. A Concentrated Solar Power plant based on steam turbine technology is also added to the assessment for the sake of comparison. The analysis yields electricity costs varying in the range from 8 to over 11 ¢/kWh, which is near but definitely not below the 6 ¢/kWh target set forth by different administrations. Nevertheless, in spite of the results, a review of the conservative assumptions adopted in the analysis suggests that attaining costs substantially lower than this is very likely. In other words, the results presented in this paper can be taken as an upper limit of the economic performance attainable by Supercritical Carbon Dioxide in Concentrated Solar Power applications.

Effect of printed circuit heat exchanger’s different designs on the performance of supercritical carbon dioxide Brayton cycle

Several fin configurations have been proposed in the literature to address the poor hydraulic performance associated with the PCHEs. However, the effect of the heat exchangers with proposed channel geometries on the performance of supercritical carbon dioxide(sCO2) power cycle is missing. In this context, the current study deals with the effects of different designs of the PCHEs varied by proposed channel configurations, heat exchanger’s effectiveness and design value of inlet Reynolds number on the performance of sCO2 power cycle. Moreover, a multi-object optimization study to find the best bargain between cycle’s efficiency and heat exchanger’s size is carried out using five different fin configurations (straight, zigzag, C-shaped, S-shaped, and airfoil fin channel configuration), heat exchanger’s effectiveness and inlet Reynolds number as a design variable. Results shows that enhancement in the hydraulic characteristics for a channel geometry that comes at the cost of thermal performance may not benefit the system’s efficiency. Optimization results suggest that C-shaped channel and zigzag channel geometries correspond to the cycle’s maximum efficiency and heat exchanger’s minimum size respectively. Optimization results further highlight that the comparison of channel geometries should be performed while in the setting of complete power generation cycle to account for all the variables involved.

Thermodynamic analysis on the combination of supercritical carbon dioxide power cycle and transcritical carbon dioxide refrigeration cycle for the waste heat recovery of shipboard

With excellent physical properties, carbon dioxide has been widely employed as a working fluid in efficient energy conversion technologies, which are represented by supercritical carbon dioxide Brayton cycle and transcritical carbon dioxide refrigeration cycle. In this contribution, with the aim to recover the waste heat of shipboard, a combined system coupling carbon dioxide Brayton cycle and refrigeration cycle is proposed to simultaneously produce power and cooling. In order to alleviate the temperature mismatch in recuperator and effectively utilize the discharged heat of refrigeration cycle, low temperature recuperator and gas cooler are shared by power and cooling cycles. For this novel waste heat recovery system, thermodynamic and economic models are developed to conduct energy, exergy and economic analysis. Thereafter, key cycle parameters including gas cooler pressure, evaporation temperature and turbine inlet temperature are investigated to reveal the effects on the system performances. The obtained results indicate that the energy and exergy efficiencies of the proposed system are respectively 42.42% and 39.05% under design conditions. The corresponding average energy cost is 9.28 $/GJ. At lower evaporation temperature and higher gas cooler pressure, the advantages of low temperature recuperator can be fully utilized and more work is produced. However, lower cooling capacity is obtained. Furthermore, the turbine inlet temperature has no effects on refrigeration cycle, and the net work decreases with the increase of inlet temperature. These results will be beneficial to improve the design and performance of combined power and cooling system for future shipboard applications.

Design and optimization of waste heat recovery system for supercritical carbon dioxide coal-fired power plant to enhance the dust collection efficiency

The supercritical carbon dioxide (SCO2) power cycle is a potential power cycle for coal-fired power plants. In the SCO2 power systems provided in previous studies, the boiler exhaust temperature is about 120 °C. To enhance the power plant efficiency and the dust collection efficiency of electrostatic precipitator, SCO2 power systems should be advanced to cool the boiler exhaust fluegas to nearly 95 °C. Therefore, systems of waste heat recovery from low-temperature fluegas are proposed and optimized in this study. Thermodynamic and optimization models are developed. The double reheat recompression SCO2 cycle is optimized as benchmark system. The benchmark system is improved to decrease the exergy loss and boiler exhaust, decrease the irreversibility of air preheater, and recover waste heat of the SCO2 cycle to preheat air to the air preheater. When the main compressor intercooling or bypass fluegas ahead the air preheater is adopted, the temperature of boiler exhaust fluegas can be decreased to around 95 °C which can ensure a high dust collection efficiency of electrostatic precipitator. The power plant efficiency is also increased as a result. However, if only low-temperature economizer is integrated, then the power plant efficiency is enhanced slightly by 0.09%-pts. If the low temperature economizer is integrated with other system improvements, the power plant efficiency can be enhanced by 0.89%-pts. Exergy analysis is also performed to reveal the mechanisms of efficiency enhancement.

Introducing a novel integrated cogeneration system of power and cooling using stored liquefied natural gas as a cryogenic energy storage system

Nowadays, it is inevitable to use energy storage systems for peak shaving and load leveling purposes. In the present study, a new integrated structure of power generation and refrigeration is developed for the use and recovery of the stored liquid natural gas energy as a cryogenic energy storage system. Kalina power cycle, molten carbonate fuel cell, carbon dioxide power cycle, and absorption-compression refrigeration system using solar energy are employed to achieve this goal. This new integrated structure generates 161,287 kW power, 1964 kW refrigeration at 266 K through LNG recovery with 4.066 kg/s mass flow rate and 8464 kW refrigeration at 218.5 K. Electrical, thermal and exergy efficiencies of the whole system are 57.92%, 61.66%, and 68.21%, respectively. In the present study, considering the efficiency of the LNG production and storage sector at the off-peak time as well as its cryogenic energy recovery sector at the on-peak time, round-trip efficiency of the proposed cryogenic storage system is calculated as 66.29%. Via the parametric study on major system parameters such as Tu101 and Tu102 turbines inlet pressures, Tu201 turbine outlet temperature, etc., the performance of the system in various conditions is evaluated. Important results of the parametric study include an increase in the system total thermal efficiency up to 70.03% by reducing the outlet temperature of the Tu201 turbine to 880 K.

Measurements of Density and Sound Speed in Mixtures Relevant to Supercritical CO2 Cycles

Abstract The objective of this research is to validate properties of mixtures relevant to supercritical carbon dioxide (sCO2) power cycles. Direct-fired sCO2 cycles are a promising technology for the future power generation systems. The working fluid of sCO2 cycles will be near and above critical point of CO2. One of the challenges is that the simulation of mixtures should consider real gas behavior. Expected operating conditions of Allam cycles reach up to 300 bar and 1000 °C. Characterizing the mixtures at the extreme conditions is an important issue in current researches and industrial applications. Thermophysical properties of mixtures may be beyond the valid range of the widely used database such as NIST REFPROP. Experimental data of mixture properties in the literature are limited which is necessary to develop high-fidelity design tools for sCO2 power cycles. We measured the density and sound speed of several multi-component mixtures. A temperature-controlled high-pressure test cell was used for the density measurements. Sound speed was measured by resonant frequency detection using an external speaker and a piezoelectric pressure sensor. Mixtures studied in this work include carbon dioxide, methane, oxygen, and water vapor. Properties of pure CO2 were measured to show the validity of our technique. Compositions were selected to be close to frozen mixtures at the inlet, mid-progress, and exhaust conditions of a model sCO2 combustor in the previous numerical simulation work. Corresponding reaction progress variables (RPV) were RPV = 0, 0.5, and 1. Temperature and pressure conditions of experiments are 310–450 K and 0–150 bar. In our study, density and sound speed from the NIST REFPROP database agree with experimental measurements within the range of our measurement uncertainties.

Energy minimization of carbon capture and storage by means of a novel process configuration

Carbon capture and storage is considered a key technology for decarbonizing the heat and power industries and achieving net zero emission targets. However, the significant energy requirements of the process as currently utilized hinders its widespread implementation. This work presents a novel process configuration by which the energy expenditures of carbon capture and storage can be minimized. This configuration is intended to enhance heat integration during the capture process through an innovative combination of three stripper modifications, namely lean vapor compression, a rich solvent split with vapor heat recovery and reboiler condensate heat recovery using a stripper inter-heater in a single flow-sheet. For carbon dioxide compression, a novel pressurization strategy involving carbon dioxide multi-stage compressors, a heat pump system and a supercritical carbon dioxide power cycle was designed and evaluated. The heat pump was used for carbon dioxide liquefaction while the supercritical carbon dioxide power cycle was employed to recover the intercooling heat. Through a comprehensive parametric investigation of the proposed configuration, the optimum value of the key operating parameters i.e., the split fraction, flash pressure, stripper inter-heater location, stripper inter-heater solvent flowrate, carbon dioxide liquefaction pressure and supercritical carbon dioxide cycle turbine pressure ratio were estimated. The performance of the proposed design at the optimized condition was quantified in terms of the reboiler heat duty, the carbon dioxide pressurization power and the equivalent work and compared to a baseline case post-combustion carbon capture and storage process. The proposed case reduced the reboiler heat duty from 3.36 GJ/TonneCO2 to 2.65 GJ/TonneCO2 and the electric power required for carbon dioxide compression from 16,691 kW to 14,708 kW. The results demonstrate that the new design can significantly reduce the reboiler duty, compression power and equivalent work by 21.1%, 11.88%, and 15.8%, respectively.

Performance improvement of supercritical carbon dioxide power cycles through its integration with bottoming heat recovery cycles and advanced heat exchanger design: A review

In this article, the performance improvement of supercritical carbon dioxide (sCO2) Brayton cycles through heat recovery and advanced heat exchanger (HX) design is reviewed. The configuration of sCO2 cycles and the bottleneck of the design of an efficient sCO2 cycle is first evaluated. It was found that heat rejected in the precooler is a large waste that could potentially enhance the overall sCO2 system performance. Then integration of the absorption cycle, organic Rankine cycle, and thermal desalination plant to the sCO2 cycle to recover the waste thermal energy is reviewed and discussed. Results showed that these bottoming heat recovery cycles could substantially improve the overall sCO2 system efficiency. The combined system of sCO2/absorption chiller, sCO2/ORC increases the cycle efficiency to about 78% and 79%, respectively. Also, a combined system of sCO2/desalination produces about 200 000 m3/day with a cost of less than $1.0/m3. Based on the review, the evaluation criteria are proposed for decision‐makers. Another bottleneck of the design of the sCO2 system is the HXs (recuperators) used in the sCO2 cycle which are relatively large and negatively affect the cycle compactness and performance. Therefore, various types of recuperators proposed and designed for sCO2 cycles are reviewed and evaluated. This review highlights the need for further research to enhance heat recovery, reduce the cost of bottoming cycles, and improve the design of HXs.

Experimental study on heat transfer of supercritical CO2 flowing in a mini tube under heating conditions

Supercritical carbon dioxide (S-CO2) power cycles hold great potential applications in various energy utilization systems, in which the heat transfer of S-CO2 is one of the most important issues. However, due to the complex thermophysical properties, it is still insufficient to predict heat transfer coefficient of S-CO2, especially under the heating conditions with high ratios of heat flux to mass flux (q/G). In this study, the heat transfer of S-CO2 is experimentally investigated in a mini tube (d = 2 mm) in the range of p = 7.6–8.4 MPa, q = 100–200 kW/m2 and G = 400–700 kg/m2 s, in which the ratio of q/G is within 250–500 J/kg. The parameter influences on heat transfer coefficient of S-CO2 are analyzed. It is found that the heat transfer coefficient decreases with increasing heat flux and decreasing mass flux, but is little affected by pressure. Under high q/G conditions, buoyancy effect is significant and heat transfer is deteriorated in the whole test section. Available heat transfer correlations for S-CO2 are compared with the experimental data; however, the prediction errors of these correlations are relatively high, especially in pseudo-critical regions. As a result, a new heat transfer correlation is developed for S-CO2 under high q/G conditions, in which buoyancy effect and variations in thermophysical properties are both taken into account.

Modeling and advanced exergy analysis of integrated reverse osmosis desalination with geothermal energy

Abstract In this research, the integrated carbon dioxide power cycle with a geothermal energy source to supply the required reverse osmosis desalination power for freshwater production is defined. It is also a carbon dioxide power cycle, coupled with thermal energy recovery of infrared energy of liquid natural gas (LNG) to generate more power. A sodium hypochlorite generator is considered to prevent the brine water discharging. The brine water portion of the desalination outlet was the input to this generator. The cycling power is consumed by the desalination system and sodium hypochlorite generator. After modeling, the advanced exergy analyses are studied. By exergy analysis, it is observed that in this model the condenser has the highest exergy destruction rate, equal to 952 kW. Additionally, the unavoidable part of the exergy destruction of carbon dioxide turbine constitutes 88% of its exergy destruction that is equal to 301 kW. So this component is the best option to improve exergy destruction.

Exergoeconomic analysis and optimization of reverse osmosis desalination integrated with geothermal energy

AbstractIn this research, the integrated carbon dioxide power cycle with the geothermal energy source to supply the required reverse osmosis desalination power for freshwater production is defined. The cycling power is consumed by the desalination system and sodium hypochlorite generator. Exergoeconomic analysis, and optimization are studied. Exergoeconomic analysis is shown that the desalination system, sodium hypochlorite generator, carbon dioxide turbine, and natural gas turbine have the highest rate for the sum of capital gain and exergy destruction cost. For the first case of optimization, the total cost rate is considered as the objective function. The optimal inlet discharge rate of sodium hypochlorite generator was 62% of the brine water outlet discharge rate of the desalination system. Plus, the total cost rate is reduced by 10% compared to the general case when 100% of brine water discharge rate of the desalination system enters into the sodium hypochlorite generator. The second case is multiobjective optimization to reduce costs and increase productivity.

Performance analysis of carbon dioxide based combined power cycle for concentrating solar power

A detailed analysis of a combined power block system using carbon dioxide integrated with a thermal energy storage system and solar field is presented. The combined power block system consists of a topping supercritical carbon dioxide recompression Brayton cycle and its waste heat is recovered by coupling a bottoming transcritical carbon dioxide power cycle. Transcritical carbon dioxide power cycle is selected owing to its temperature glide merit and better heat transfer characteristics than conventional waste heat recovery cycle systems using other working fluids. A molten salt that can operate at relatively higher temperature than nitrate solar salt is selected as a storage medium and as heat transfer fluid between thermal energy storage system and external heat exchanger of power block. A complete mathematical model for the heliostat field, solar receiver, thermal energy storage, and power block system has been developed. The discretized heat exchanger approach has been implemented to accurately capture the properties of working fluid and to provide more refined results. Theoretical analysis of the system includes first and second law efficiencies and power output. The research findings suggest that the integrated combined cycle configuration is a promising alternative for efficient energy conversion and the established framework provides a profoundly potential way to utilize concentrated solar power.

Impact of Fluid Substitution on the Performance of an Axial Compressor Blade Cascade Working with Supercritical Carbon Dioxide

Abstract Recent research on turbomachinery design and analysis for supercritical carbon dioxide (sCO2) power cycles has relied on computational fluid dynamics. This has produced a large number of works whose approach is mostly case-specific, rather than of general application to sCO2 turbomachinery design. As opposed to such approach, this work explores the aerodynamic performance of compressor blade cascades operating on air and supercritical CO2 with the main objective to evaluate the usual aerodynamic parameters of the cascade for variable boundary conditions and geometries, enabling “full” or “partial” similarity. The results present both the global performance of the cascades and certain features of the local flow (trailing edge and wake). The discussion also highlights the mechanical limitations of the analysis (forces exerted on the blades), which is the main restriction for applying similarity laws to extrapolate the experience gained through decades of work on air turbomachinery to the new working fluid. This approach is a step toward the understanding and appropriate formulation of a multi-objective optimization problem for the design of such turbomachinery components where sCO2 is used as the operating fluid. With this objective, the paper aims to identify and analyze what would be expected if a common description of such computational design problems similar to those where air is the working fluid were used.

A Supercritical CO2 Waste Heat Recovery System Design for a Diesel Generator for Nuclear Power Plant Application

After the Fukushima accident, the importance of an emergency power supply for a nuclear power plant has been emphasized more. In order to maximize the performance of the existing emergency power source in operating nuclear power plants, adding a waste heat recovery system for the emergency power source is suggested for the first time in this study. In order to explore the possibility of the idea, a comparison of six supercritical carbon dioxide (S-CO2) power cycle layouts recovering waste heat from a 7.2 MW alternate alternating current diesel generator (AAC DG) is first presented. The diesel engine can supply two heat sources to the waste heat recovery system: one from exhaust gas and the other from scavenged air. Moreover, a sensitivity study of the cycles for different design parameters is performed, and the thermodynamic performances of the various cycles were evaluated. The main components, including turbomachinery and heat exchangers, are designed with in-house codes which have been validated with experiment data. Based on the designed cycle and components, the bottoming S-CO2 cycle performance under part load operating condition of AAC DG is analyzed by using a quasi-steady state cycle analysis method. It was found that a partial heating cycle has relatively higher net produced work while enjoying the benefit of a simple layout and smaller number of components. This study also revealed that further waste heat can be recovered by adjusting the flow split merging point of the partial heating cycle.

500℃ 대응 kW급 초임계 이산화탄소 발전 시스템 시험 장치 예비운전 특성 연구

초임계 이산화탄소 발전 사이클이란 증기 사이클과 마찬가지로 터보제너레이터를 구동하여 전기를 생산하지만 작동 유체로 증기가 아닌 이산화탄소를 사용하는 발전 사이클을 의미한다. 특히 사이클 전 공정에 걸쳐 초임계 이산화탄소가 상대적으로 높은 밀도로 존재하기 때문에 작은 크기의 터보기기나 열교환기를 사용 가능한 장점이 있다. 또한, 압축일이 적어 사이클의 효율이 높고, 저압부의 온도가 상온 이상이므로 물이 부족한 지역에서 건식냉각을 활용할 수 있는 장점도 있다. 본 논문에서는 500℃ 대응 kW급 초임계 이산화탄소 발전 시스템 시험 장치의 설계와 예비시험에 대하여 논의하고 있으며, 예비시험 결과로부터 초임계 이산화탄소 발전의 운전 절차를 정립하고, 그 특징을 살펴보았다.

Carbonate molten salt solar thermal pilot facility: Plant design, commissioning and operation up to 700 °C

Concentrated solar power (CSP) is not currently cost competitive with conventional power generation or other solar energy technologies, but it is attractive because it integrates commercially viable large-scale thermal energy storage (TES). To improve performance and reduce costs, supercritical carbon dioxide (s-CO2) power cycles have been proposed to increase the thermal-to-electric conversion to values above 50%. However, to achieve this target, the solar energy collected by the receiver and stored in the TES must be delivered to the power turbine at a temperature at or above 700 °C, while current advanced plants only provide thermal energy at 565 °C. For the first time, a high temperature (700 °C) molten salt experimental pilot plant for CSP was designed, built, and tested by Abengoa using carbonate salts as the heat transfer fluid. We demonstrate the feasibility of large-scale, industrially relevant operation between 400 and 700 °C, thus providing a solution to integrate higher efficiency s-CO2 power cycles. We address the key points in material compatibility, component design, instrumentation and system integration. Operational aspects such as preheating and filling procedures, start-up, maximum temperature reached, and the main challenges faced are described in detail. The heat losses in the loop and components are analyzed. We show that with appropriate electrical heat tracing elements, operation with carbonates is feasible and that the main subsystems that must be redesigned are the high temperature tanks and pumps. Lessons learned from the plant operation are summarized here to guide the design of future commercial scale high temperature molten salt plants.

500℃ 터빈 입구 조건의 수백 kWe급 초임계 이산화탄소 발전시스템 테스트루프 개발 연구

한국에너지기술연구원에서는 바이오매스 및 폐열과 같은 분산 전원에 적합한 수백 kWe급 초임계 이산화탄소 발전사이클 테스트루프를 개발 중에 있다. 터빈 2기, 압축기, 복열기 2기, 연소배가스 이용 히터로 구성된 120kWe 용량의 이중 브레이튼 사이클을 개발하였으며, 목표 터빈 입구 조건은 500℃/135bar이다. 미캐니컬 씰과 틸팅패드 베어링으로 구성된 충동형 축류 터보-발전기는 2017년에 이미 제작, 시험을 성공적으로 완료하였다. 다음 단계로 드라이가스씰(DGS)이 적용된 원심형 압축기를 개발하였으며, 버너와 쉘앤튜브 열교환기로 구성된 650℃의 연소배가스 이용 히터를 제작하고, ASME 기준에 따라 배관 설계를 진행하였다. 전체 테스트루프는 올해 완성 및 운전을 목표로 하고 있다.

Thermal performance and economic analysis of supercritical Carbon Dioxide cycles in combined cycle power plant

A closed-loop, indirect, supercritical Carbon Dioxide (sCO2) power cycle is attractive for fossil-fuel, solar thermal and nuclear applications owing to its ability to achieve higher efficiency, and compactness. Commercial Gas Turbines (GT’s) are optimised to yield maximum performance with a conventional steam Rankine cycle. In order to explore the full potential of a sCO2 cycle the whole plant performance needs to be considered. This study analyses the maximum performance and cost of electricity for five sCO2 cascaded cycles. The plant performance is improved when the GT pressure ratio is considered as a design variable to a GT to optimise the whole plant performance. Results also indicate that each sCO2 Brayton cycle considered, attained maximum plant efficiency at a different GT pressure ratio. The optimum GT pressure ratio to realise the maximum cost reduction in sCO2 cycle was higher than the equivalent steam Rankine cycle. Performance maps were developed for four high efficient cascaded sCO2 cycles to estimate the specific power and net efficiency as a function of GT turbine inlet temperature and pressure ratio. The result of multi-objective optimisation in the thermal and cost (c$/kWh) domains and the Pareto fronts of the different sCO2 cycles are presented and compared. A novel sCO2 cycle configuration is proposed that provides ideal-temperature glide at the bottoming cycle heat exchangers and the efficiency of this cycle, integrated with a commercial SGT5-4000F machine in lieu of a triple-pressure steam Rankine cycle, is higher by 1.4 percentage point.

Calcium-based composites for direct solar-thermal conversion and thermochemical energy storage

Calcium-Looping (CaL) is considered as a promising process for thermochemical energy storage in the 3rd generation Concentrated Solar Power plants using a supercritical carbon dioxide power cycle. Here we propose, for the first time, a novel strategy to directly absorb solar energy using calcium-based composite thermochemical energy storage (TCES) materials. The main novelty lies in the binary metallic element doping of the calcium-based raw materials to enhance their direct interactions with solar radiation photons for light capturing. In particular, the use of the metallic element doping is to form high light-absorbing material for addressing the unfavorable intrinsic optical absorption properties of the calcium carbonate for photon management. A simple and facile sol-gel method was used to synthesize the CaO composites doped with Mn and Fe. Such binary metallic element doping into the calcium-based materials not only boosted the solar absorption but also improved the cycling stability of the TCES material in the integrated CaL-CSP system. The synthetic composites were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The effects of thermochemical cycling on the microstructures and properties of TCES material were investigated. Furthermore, the underlying mechanisms were discussed. The results indicated that the enhancement of the optical absorption for the composites originated from metal oxides of Fe and Mn with high light-absorbing ability. The synergistic effects of small grain size and the reinforced skeleton structures could impede agglomeration and collapse of the composites, thereby improving the cycling stability.