Splitting Cycle Research Articles

Preliminary design and performance assessment of compressed supercritical carbon dioxide energy storage system

Energy storage system plays a key role in the network grid with the increasing penetration of intermittent renewable energy. Compared with the compressed air energy storage system, the energy storage with compressed supercritical carbon dioxide has the advantages of compactness and high energy storage density. In this paper, we propose two isobaric compressed supercritical carbon dioxide energy storage systems: a simple cycle system and a split cycle system. Underwater energy bags are firstly adopted to store the compressed carbon dioxide and maintain a constant gas pressure during charging and discharging processes. Energy and exergy performance of the systems are analyzed, and the exergy economics is presented for the proposed compressed carbon dioxide energy storage systems. The effect of key parameters on the system performance is performed. The results show that the simple cycle has a lower round trip efficiency (38.74%), a lower exergy efficiency (55.85%) and a slightly better economic performance. The split cycle performs with a higher round trip efficiency (43.94%) and a higher exergy efficiency (62.81%). Total investment cost per unit output work of the split cycle (0.0726 $/kWh) is higher under the condition of free heat source. It can be concluded that the split cycle can enhance the thermodynamic performance of the energy storage system by improving the design of the recuperator.

Thermochemical splitting of CO2 using solution combustion synthesized lanthanum–strontium–manganese perovskites

Redox reactivity of La(1-x)SrxMnO3 (LSM) perovskites towards a solar thermochemical CO2 splitting (CS) cycle is investigated. The LSM perovskites are synthesized via a solution combustion synthesis (SCS) method using glycine as the reducing agent. Multiple analytical techniques are used for the structural characterization of the LSM perovskites. Thermogravimetric thermal reduction (TR) and CS cycles (in three sets: one, three and ten cycles) are conducted to estimate the amounts of O2 released (nO2) and CO produced (nCO) by each LSM perovskite. Higher nO2 by each LSM perovskite, as compared to the nCO during the first cycle. The nO2 is decreased, and the re-oxidation capacity of each LSM perovskite is improved from cycle one to three. In terms of the average nO2 and nCO from cycle 2 to cycle 10, the La0.60Sr0.41Mn0.99O2.993 (214.8 μmol of O2/g·cycle) and La0.30Sr0.70Mn0.99O2.982 perovskites (342.1 μmol of CO/g·cycle) are observed to have the uppermost redox reactivity. The redox reactivity of all the LSM perovskites (except for La0.88Sr0.11Mn1.00O2.980) is recorded to be higher than that of the widely studied CeO2 material.

Exploring the alternative MnO-Na2CO3 thermochemical cycle for water splitting

Abstract Thermochemical cycles for H2O and CO2 splitting using CeO2 have demonstrated high efficiency (> 5%) and fast kinetics. Alternative multistage cycles based on stoichiometric oxides, such as Mn-Na, can potentially provide much larger efficiencies under less stringent operation conditions. However, these cycles consist of three stages operating at very different temperatures (from 50 °C to 1500 °C) and, accordingly, the overall energy yield of the cycle critically depends on efficient heat recovery. Despite of this, recently the Mn3O4–Na2CO3 cycle has shown a remarkable H2 production and high stability. To further enhance hydrogen generation rate, in this work we explore the feasibility of the novel cycle based on MnO, which can potentially increase the yield per cycle. Several samples of MnO with different physicochemical characteristics were investigated to establish the influence on the oxide physicochemical properties on hydrogen generation. A maximum conversion of 47 %, with a productivity of 20.1 μmol H2 min−1 g−1 were obtained using the MnO sample with relatively large surface area. As expected, this productivity is notably better than that obtained with Mn3O4 under identical conditions. Furthermore, the results obtained here reveals that low temperature hydrolysis under CO2 atmosphere can improve the Na extraction by more than 10 %. This enhances the cyclability of the process and it may allow coupling hydrogen production with CO2 capture. Furthermore, the thermal reduction of the solid product recovered after the carbonation stage yields nearly pure MnO, confirming experimental the feasibility of completing this alternative cycle.

Efficient generation of hydrogen by two-step thermochemical cycles: Successive thermal reduction and water splitting reactions using equal-power microwave irradiation and a high entropy material

Hydrogen production through two-step thermochemical water splitting cycle based on metal oxide has emerged as a promising strategy to store dilute and intermittent solar energy. However, a typical reaction time of the two-step thermochemical water splitting cycle is lengthy, with at least 0.5 h for thermal reduction step and 1 h for water splitting step, and the energy required in the thermal reduction process for hydrogen regeneration is higher than the generated hydrogen energy. In this work, to overcome the problem of an energy efficiency imbalance, we investigated the possibility of the rapid and successive reactions of thermal reduction and water splitting, using short-term irradiation from a low-energy microwave. To this end, a high entropy material, as a poly-metal oxide used to generate hydrogen, was produced by simultaneously introducing four cations onto a SiC foam – (FeMgCoNi)O1.2@SiC. It was found that the oxygen vacancy of the (FeMgCoNi)O1.2@SiC could be significantly increased by short-term microwave irradiation, and hence the thermal reduction process took only 4 min, which is much less than normal. High H2 generation rates were achieved by re-oxidation of the Fe (II) to Fe (III) of the (FeMgCoNi)O1.2@SiC. In addition, the microwave plasma generated by microwave irradiation induced (FeMgCoNi)O1.2@SiC discharge could enhance the water splitting process. The maximum hydrogen yield was 122 mL/g at 700 W, due to the coupling effect of the thermochemical cycle and microwave plasma. In this way, the power consumption of microwave process is only 3% of that of conventional high-temperature heat treatment during thermal reduction process.

Thermodynamic analysis and optimization of an integrated solar thermochemical hydrogen production system

In this study, thermodynamic analysis of solar-based hydrogen production via copper-chlorine (Cu–Cl) thermochemical water splitting cycle is presented. The integrated system utilizes air as the heat transfer fluid of a cavity-pressurized solar power tower to supply heat to the Cu–Cl cycle reactors and heat exchangers. To achieve continuous operation of the system, phase change material based on eutectic fluoride salt is used as the thermal energy storage medium. A heat recovery system is also proposed to use the potential waste heat of the Cu–Cl cycle to produce electricity and steam. The system components are investigated thoroughly and system hotspots, exergy destructions and overall system performance are evaluated. The effects of varying major input parameters on the overall system performance are also investigated. For the baseline, the integrated system produces 343.01 kg/h of hydrogen, 41.68 MW of electricity and 11.39 kg/s of steam. Overall system energy and exergy efficiencies are 45.07% and 49.04%, respectively. Using Genetic Algorithm (GA), an optimization is performed to evaluate the maximum amount of produced hydrogen. The optimization results show that by selecting appropriate input parameters, hydrogen production rate of 491.26 kg/h is achieved.

Regeneration of a metal oxide catalyst with polyvinylpyrrolidone under xenon flash irradiation for repetitive hydrogen generation

In thermochemical water splitting cycles using an oxide catalyst, the temperature required for the catalyst reduction process (1000 °C–2500 °C) is much higher than that required for the hydrogen generation process (800 °C–1500 °C). Accordingly, there is an issue of inefficiency because the energy required to generate hydrogen is higher than the generated hydrogen energy. In this study, we investigated a method to decrease the energy required for the reduction of an oxide catalyst through the combination of polyvinylpyrrolidone as a reducing agent and Xe flash irradiation. A three-dimensional (3D) microporous nickel oxide (NiOx) was used as the oxide catalyst to maximize the surface area of the reaction and, hence, the amount of hydrogen generated from water. During the repeated hydrogen generation cycles, the maximum rate of hydrogen generation (10.6 µmol min−1 g−1) and the total amount of hydrogen generated (642 µmol g−1) were stably maintained without the degradation of the 3D microporous NiOx catalyst structure. The reduction method proposed here is expected to provide insights to resolve the issue of the inefficiency of energy in the catalyst reduction process during the hydrogen generation and regeneration processes using an oxide catalyst.

Production of solar CO via two-step neodymium oxide based thermochemical CO2 splitting cycle

Detailed thermodynamic scrutiny of the solar thermochemical neodymium oxide-based CO2 splitting (Nd-CS) cycle is reported. The thermal reduction (TR) and CO2 splitting (CS) reaction temperatures required for the operation of the Nd-CS cycle were determined. The equilibrium compositions of Nd2O3, NdO, and O2 exhibit that the initiation of the TR of Nd2O3 is feasible at 1982 K, and the complete conversion is possible at 2232 K. As per the delta G analysis, the CS reaction was feasible at all temperatures above 300 K. After understanding the chemical thermodynamic equilibrium of the Nd-CS cycle, the efficiency analysis was performed by using the HSC Chemistry 9.9 software. The results obtained via the efficiency analysis shows that the Nd-CS cycle was capable of attaining the highest possible ηsolar-to-fuel-Nd-CS = 9.45% at partial TR of Nd2O3 = 55% (TH = 2154 K). Application of HR = 20%, 40%, 60%, 80%, and 100%, improved ηsolar-to-fuel-Nd-CS at TR-Nd = 55% (TH = 2154 K) up to 10.51%, 11.84%, 13.55%, 15.85%, and 19.09%, respectively.

A study on the Fe–Cl thermochemical water splitting cycle for hydrogen production

Thermochemical water splitting cycles are recognized as one of the promising pathways for sustainable hydrogen production. In the present study, Iron-chlorine (Fe–Cl) cycle as one of the chlorine family thermochemical cycles where iron chloride is consumed for hydrogen production from water, is considered for a study. This four-step cycle is modelled by Aspen Plus software package and analyzed for performance investigation of each reaction step and system's components. The parametric studies are also performed to assess the effect of operation conditions such as temperature, pressure and steam to feed ratio on the reaction products and conversion rates. Results indicated that although the effect of pressure is not significant on reaction's production rates, an increase in temperature favors oxygen production in reverse deacon reaction and magnetite production in hydrolysis and lowers hydrogen production in the hydrolysis step. On the other hand, steam to chlorine (Cl2) ratio is directly correlated with hydrochloric acid (HCl) and oxygen production in reverse deacon reaction and hydrogen production in hydrolysis.

Thermodynamic study of the effect of partial thermal reduction of dysprosium oxide on solar-to-fuel energy conversion efficiency

A thermodynamic equilibrium and efficiency analysis of the dysprosium oxide-based solar thermochemical H2O splitting (Dy-WS) cycle is conducted. The objective of this study is to understand the effect of partial thermal reduction (TR) of Dy2O3 on the solar-to-fuel energy conversion efficiency (ηsolar-to-fuel-Dy-WS) of the Dy-WS cycle. The equilibrium analysis indicate a rise in the percentage TR of Dy2O3 (%TR-Dy) from 0.3% up to 100% when the TR temperature (TH) is increased from 2000 K to 2530 K. The upsurge in the TH yielded a considerable surge in the Q̇solar-reactor-Dy-WS and Q̇solar-heater-Dy-WS. Overall results of this study showed that the ηsolar-to-fuel-Dy-WS is amplified from 0.6% to 6.5% in three zones (slow zone, medium-fast zone, and fast zone) as the TH is amplified from 2000 K up to 2280 K. A further rise in the TH from 2280 K up to 2530 K resulted in a drop in the ηsolar-to-fuel-Dy-WS from 6.5% to 3.5%. By employing the heat recuperation, the ηsolar-to-fuel-HR-Dy-WS is improved further up to 11.4% (at TH = 2280 K).

Understanding Sub and Supercritical Cryogenic Fluid Dynamics in Conditions Relevant to Novel Ultra Low Emission Engines

In this paper we provide insight into the thermophysical properties and the dynamics of cryogenic jets. The motivation of the work is to optimise the use of cryogenic fluids in novel ultra low emission engines. For demonstration, we use conditions relevant to an internal combustion engine currently being developed by Dolphin N2 and the University of Brighton, the CryoPower recuperated split cycle engine (RSCE). The principle of this engine is a split-cycle combustion concept which can use cryogenic injection in the compression cylinder to achieve isothermal compression and thus help maximise the efficiency of the engine. Combined experimental and numerical findings are presented and the effects of atomisation dynamics of the LN 2 are explored at both sub- and supercritical conditions in order to cover different pressure and temperature conditions representative of the engine compression cycle. For subcritical regimes, we observe that the appearance of the jet coincides with the predicted atomisation regimes based on the Weber, Ohnesorge and Reynolds numbers for other common fluids. For the modelling of supercritical jets, a new methodology within OpenFoam which accounts for Real Fluid Thermodynamics has been developed and the jet behaviour under various pressure and temperature conditions has been investigated. To our knowledge this is the first study where a cryogenic spray process evolution is examined for conditions relevant to the ones prevailing in a compression chamber accounting for both sub and supercritical conditions.

Application of chromium oxide-based redox reactions for hydrogen production via solar thermochemical splitting of water

Thermodynamic equilibrium, as well as efficiency analysis of the Cr2O3/Cr water splitting (Cr-WS) cycle, was conducted in this study. The thermodynamic properties required for the computations were obtained from an HSC Chemistry 9.9 software. An increase in thermal reduction (TR) temperature (TH) from 1800 K to 2230 K was responsible for the rise in the percentage TR of Cr2O3 (Tr-Cr) from 0% to 100%. The equilibrium analysis additionally indicates that the re-oxidation of Cr into Cr2O3 via WS reaction is feasible at any temperature from 300 to 3000 K (we have selected 1300 K for this study). The efficiency analysis indicates that the Q̇solar-reactor-Cr-WS and Q̇solar-heater-Cr-WS were enhanced by 3636.8 kW and 260.0 kW due to the increment in the TH from 1800 K to 2230 K. The increase in the Q̇solar-reactor-Cr-WS and Q̇solar-heater-Cr-WS resulted into a rise in the Q̇solar-cycle-Cr-WS by 3896.8 kW. The ηsolar-to-fuel-Cr-WS increased from 9.5% to 26.4% when the TH was augmented from 1800 K to 2000 K. A further rise in the TH from 2000 K to 2230 K resulted in a reduction in the ηsolar-to-fuel-Cr-WS from 26.4% to 21.3%. After employing the 100% heat recuperation, theηsolar-to-fuel-HR-Cr-WS of the Cr-WS cycle was improved up to 48.3% at TH = 2000 K.

Is intracytoplasmic sperm (ICSI) better than traditional in vitro fertilization (IVF): confirmation of higher blastocyst rates per oocyte using a split insemination design.

To explore the effects of traditional vs. intracytoplasmic sperm injection (ICSI) insemination method on the outcome of high-quality blastocyst development in a split sibling oocyte cohort. In this retrospective cohort study, we analyzed 62 ICSI/IVF split cycles. Sibling oocytes were randomly assigned to ICSI or IVF insemination. Two hundred thirty-four ICSI-only cycles and 152 IVF-only cycles were also analyzed for comparison. Blastocysts were graded by Gardner's embryo grading and were considered a high-quality blastocyst if 3BB or better (Gardner 1999). In the ICSI/IVF split group, (1) ICSI oocytes had a higher fertilization rate per oocyte allocated (73% vs 62%, p < 0.001), (2) more high-quality day 2 embryos (69% vs 55%, p < 0.005), (3) ICSI oocytes had a lower blastulation rate per 2PN (46% vs 54%, p < 0.05), but a higher blastulation rate when calculated per oocyte allocated (40% vs 32%, p < 0.05). The ICSI-only group had a lower fertilization rate (65% vs 70%, p < 0.001) but more high-quality day 2 embryos in comparison to the IVF-only group (68% vs 64%, p < .05). The total high-quality blastulation rate was higher for the IVF-only group per 2PN (49% vs 43%, p < 0.05) and per oocyte retrieved (34% vs 28%, p < 0.05). This distinctive IVF/ICSI sibling oocyte split design demonstrated a higher-quality blastulation rate in the IVF group compared to the ICSI group when calculated per 2PN, but not per oocyte allocated to each insemination procedure.

Utilization of Niobium Pentoxide based redox reactions for solar hydrogen generation via thermochemical water splitting cycle

A solar-driven Nb2O5-based water splitting (Nb-WS) cycle thermodynamically scrutinized and the obtained results reported in this paper. The thermodynamic analysis conducted in two phases: phase-1) equilibrium analysis and phase-2) efficiency analysis. According to the equilibrium analysis, partial thermal reduction (TR) of Nb2O5 from 0.7% up to 100% was feasible in the temperature range of 1700 K–2083 K. The obtained results further indicate that the WS reaction was favorable at any temperature below 1500 K. As per the outcomes associated to the efficiency analysis, the Q˙solar-reactor-Nb-WS and Q˙solar-steam generator-Nb-WS increased by 2321.7 kW and 87.2 k due to the rise in the TH from 1700 K to 2083 K. This upsurge in the Q˙solar-reactor-Nb-WS and Q˙solar-steam generator-Nb-WS resulted in an upturn in the Q˙solar-cycle-Nb-WS by 2408.9 kW. The ηsolar-to-fuel-Nb-WS also amplified from 1.9% up to 11.4% as the TH surged from 1700 K up to 2040 K. A further rise in the TH from 2040 K up to 2083 K does not yield any improvement in the ηsolar-to-fuel-Nb-WS. A 50% heat recuperation resulted in the attainment of the maximumηsolar-to-fuel-HR-Nb-WS equal to 15.8% at TH=2020 K.

An overview of solar decarbonization processes, reacting oxide materials, and thermochemical reactors for hydrogen and syngas production

Solar decarbonization processes are related to the different thermochemical conversion pathways of hydrocarbon feedstocks for solar fuels production using concentrated solar energy as the external source of high-temperature process heat. The main investigated routes aim to convert gaseous and solid feedstocks (methane, coal, biomass …) into hydrogen and syngas via solar cracking/pyrolysis, reforming/gasification, and two-step chemical looping processes using metal oxides as oxygen carriers, further associated with thermochemical H2O/CO2 splitting cycles. They can also be combined with metallurgical processes for production of energy-intensive metals via solar carbothermal reduction of metal oxides. Syngas can be further converted to liquid fuels while the produced metals can be used as energy storage media or commodities. Overall, such solar-driven processes allow for improvements of conversion yields, elimination of fossil fuel or partial feedstock combustion as heat source and associated CO2 emissions, and storage of intermittent solar energy in storable and dispatchable chemical fuels, thereby outperforming the conventional processes. The different solar thermochemical pathways for hydrogen and syngas production from gaseous and solid carbonaceous feedstocks are presented, along with their possible combination with chemical looping or metallurgical processes. The considered routes encompass the cracking/pyrolysis (producing solid carbon and hydrogen) and the reforming/gasification (producing syngas). They are further extended to chemical looping processes involving redox materials as well as metallurgical processes when metal production is targeted. This review provides a broad overview of the solar decarbonization pathways based on solid or gaseous hydrocarbons for their conversion into clean hydrogen, syngas or metals. The involved metal oxides and oxygen carrier materials as well as the solar reactors developed to operate each decarbonization route are further described.

Solar thermochemical splitting of H2O using Ca-Ferrite based redox reactions: Effect of partial pressure of O2

The influence of the partial pressure of O2(PO2) on the viability of the Ca-ferrite based solar thermochemical H2O splitting cycle was thermodynamically scrutinized. The thermodynamic parameters were estimated by maintaining a steady thermal reduction (TR) and water splitting (WS) temperature equal to 1800 K and 1200 K, respectively. The reduction in the PO2 from 10−1 atm to 10−5 atm resulted in an improvement in the degree of non-stoichiometry (δ) associated with the Ca-ferrite from 0.172 to 0.720. Besides, a similar drop in the PO2increased the Q˙CaFe2O4−red−CFWS and Q˙H2O−heating−CFWS by 222.4 kW and 43.1 kW, separately. An upsurge in both Q˙CaFe2O4−red−CFWS and Q˙H2O−heating−CFWS significantly affected the Q˙solar−cycle−CFWS, and it was enhanced from 382.5 kW to 704.8 kW when the PO2 increased from 10−1 atm to 10−5 atm. Even though Q˙solar−cycle−CFWS was enlarged, due to the augmentation in H2 production, ηsolar−to−fuel−CFWS was escalated from 12.8% to 29.2% when the PO2 was decreased from 10−1 atm to 10−5 atm. By employing heat recuperation, the maximumηsolar−to−fuel−HR−CFWS (61.1%) was recorded for PO2=10−5atm.

An ageing protocol for testing high temperature solar materials for thermochemical applications

Future's sustainable economy based on hydrogen will require large-scale hydrogen production processes in a CO2 emission-free way. Within this context, solar-driven thermochemical water splitting cycles have been proposed as a promising alternative for hydrogen mass production.Thermochemical processes require thermal and chemically stable reactor wall materials, which can withstand severe operating conditions, suitable for specific solar fuels production. Several unresolved issues are involved in predicting the effect of environmental degradation on the long-term performance of innovative materials for next generation solar chemical reactors to guarantee their reliability and durability under demanding working conditions.The research project ARROPAR-CEX involves a multidisciplinary team for studying novel receiver concepts and new materials, working under extreme conditions (in excess of 1000 kW/m2, and very high temperatures, typically above 1000 °C).The main objective of this work has been to develop and propose as candidate an accelerated ageing method for solar receiver’ materials, in order to estimate their degradation during lifetime under extreme solar operating conditions. A set of four selected ceramic materials have been submitted to these accelerated ageing test procedures and some preliminary conclusions on their suitability have been extracted.

Thermodynamic performance assessment of boron based thermochemical water splitting cycle for renewable hydrogen production

The present study is related with the thermodynamic performance assessment of renewable hydrogen production through Boron thermochemical water splitting cycle. Therefore, all step efficiencies and overall cycle efficiency are calculated based on complete reaction. Additionally, a parametric study is conducted to determine the effect of the reference environment temperature on the overall cycle efficiency. In this regard, exergy efficiencies, exergy destruction rates and also inlet and outlet exergy rates of the cycle are calculated and presented for various reference temperatures. The exergy efficiency of the cycle is calculated as 0.4393 based on complete reaction and occurs at 298 K. This study has shown that Boron thermochemical water splitting cycle has a great potential due to cycle performance. As a result, Boron based thermochemical water splitting cycle can help achieve better environment and sustainability due to high exergetic efficiency. By the way, economic and technical issues of the storage and transportation of the hydrogen can find a proper solution if the hydrogen production reaction of the Boron thermochemical water splitting cycle takes place on-board of a vehicle.

Solar hydrogen production via thermochemical magnesium oxide – Magnesium sulfate water splitting cycle

This investigation reports the thermodynamic scrutiny of the MgO/MgSO4 water-splitting cycle. At the initial stage, the thermal reduction temperature required for the commencement of the thermal dissociation of MgSO4 (in the absence of inert Ar) and the maximum temperature below which the water-splitting reaction is feasible is identified by performing thermodynamic equilibrium calculations. The influence of inert Ar as the carrier gas on the thermal reduction temperature is also explored. After identifying the required operating temperatures, the second law efficiency analysis predicts the process parameters of this cycle. Overall analysis confirms that although the rise in the molar flow rate of Ar from 1 to 50 mol/s results in a decrease in the thermal reduction temperature from 1490 K to 1282 K, the solar-to-fuel energy conversion efficiency is adversely affected and reduces from 47.7% to 18.1%. As per the analysis, this cycle achieved the highest solar-to-fuel energy conversion efficiency (47.7%) at the molar flow rate of Ar = 1 mol/s, thermal reduction temperature = 1490 K, and water splitting temperature = 475 K. Further increment in the solar-to-fuel energy conversion efficiency up to 62.5% is possible if 50% of the heat recuperation is applied.

CeTi2O6-A Promising Oxide for Solar Thermochemical Hydrogen Production.

A large entropy of reduction is crucial in achieving materials capable of high-efficiency solar thermochemical hydrogen (STCH) production through two-step thermochemical water splitting cycles. We have recently demonstrated that the onsite electronic entropy of reduction attains an extreme value of 4.26 kB at 1500 K in Ce4+ → Ce3+ redox reactions, which explains the high performance and uniqueness of CeO2 as an archetypal STCH material. However, ceria requires high temperatures (T > 1500 °C) to achieve a reasonable reduction extent because of its large reduction enthalpy, which is a major obstacle in practical applications. Therefore, new materials with a large entropy of reduction and lower reduction enthalpy are required. Here, we perform a systematic screening to search for Ce4+-based oxides which possess thermodynamics superior to CeO2 for STCH production. We first search the Inorganic Crystal Structure Database (ICSD) and literature for Ce4+-based oxides and subsequently use density functional theory to compute their reduction enthalpies (i.e., oxygen vacancy formation energies). We find that CeTi2O6 with the brannerite structure is the most promising candidate for STCH because it possesses three essential characteristics of an STCH material: (i) a smaller reduction enthalpy compared to ceria yet large enough to split water, (ii) a high thermal stability, as reported experimentally, and (iii) a large entropy of reduction associated with Ce4+ → Ce3+ redox. Our proposed design strategy suggests that further exploration of Ce4+ oxides for STCH production is warranted.

Estimation of solar‐to‐fuel energy conversion efficiency of a solar driven samarium oxide‐based thermochemical CO2 splitting cycle

AbstractEstimation of the solar‐to‐fuel energy conversion efficiency (with and without heat recuperation) of the Sm2O3/SmO‐based solar‐driven thermochemical CO2 splitting cycle is reported. HSC Chemistry 9.9 software and its thermodynamic database were utilized for the thermodynamic analysis. The temperatures required for the partial thermal reduction (TR) of Sm2O3 and the reoxidation of SmO via CO2 splitting (CS) reaction were identified. The thermodynamic modeling equations and the process flow configuration for the Sm2O3/SmO‐based CO2 splitting (Sm‐CS) cycle were formulated. The obtained results indicate that a higher quantity of solar energy input was needed to increase the percentage of partial TR of Sm2O3. The solar‐to‐fuel energy conversion efficiency (without heat recuperation) was first increased up to 9.13% for 50% of TR‐Sm and then decreased to 6.54% as the %TR‐Sm further enhanced to 100%. The application of heat recuperation was beneficial not only to increase the solar‐to‐fuel energy conversion efficiency but also to decrease the TR temperature required for the attainment of the maximum efficiency value. © 2020 Society of Chemical Industry and John Wiley &amp; Sons, Ltd.