Cycle Efficiency Research Articles

Modelling and optimization of combined supercritical carbon dioxide Brayton cycle and organic Rankine cycle for electricity and hydrogen production

Hydrogen as a clean fuel, is key energy carrier for sustainable development, and its production via water electrolysis is most desirable for its carbon free nature. Nuclear power provides good opportunity to satisfy the huge energy demand associated with the process, in addition to electrical power generation. Modelling an efficient and cost effective nuclear based power and Hydrogen cogeneration system and optimizing it to enhance its performance is the core academic problem addressed in the present study. It proposes a power plant cycle aided by a nuclear reactor, providing 300 MW thermal power input. Supercritical CO2 Brayton cycle is used as the main cycle, instead of traditional Helium Brayton cycle or steam Rankine cycle. To increase the cycle efficiency, by reducing the compression work and by reducing the cold source loss, main compression intercooling and waste heat recovery by an Organic Rankine Cycle (ORC) is introduced together with recompression Brayton cycle arrangement. The power coming from recovered waste heat goes to a Proton Exchange Membrane Electrolyzer (PEME), which facilitates the production of Hydrogen by splitting water via electrolysis. Additional attention is given to ORC fluid selection by employing and comparing the performance of widely acknowledged R245fa together with its more eco friendly replacements, R1233Zd(E) and R1234Ze(Z). The evaluation of the system performance is conducted through the lenses of Energy, Exergy, and Economics. Essential parameters are scrutinized to gauge their impact on two pivotal objectives. Overall Exergy Efficiency(ηex) takes care of the thermodynamic performance and the economic aspect is scrutinized by Levelized Cost of Energy (LCOEn). Notably, by employing R245fa as the ORC working fluid, the system attains peak Energy efficiency of 42.13% and Exergy efficiency of 58.32%, and a minimum LCOEn of 0.063 USD/kWh. Of all the components associated with the system nuclear reactor tops the chart for maximum exergy destroyed(40.8% of total) as well as maximum investment cost(65.7% of total). Pump contributes least to exergy destruction(0.03% of the total) and heat exchangers hold least share(1.1% of total) for investment cost. Furthermore, a multiobjective optimization exercise is executed to fine-tune the system’s operational parameters. This optimization results in a 3.12% increase in Overall Exergy Efficiency and a 9.79% decrease in LCOEn compared to the base operating condition with R245fa used as the ORC fluid. The ηex & LCOEn in best possible operating condition are 58.25% & 0.0645 USD/kWh using R245fa as ORC fluid, 58.23% & 0.0645 USD/kWh using R1233Zd(E) as ORC fluid and 58.22% & 0.0644 USD/kWh using R1234Ze(Z) as ORC fluid. If same amount of electrical Power is supplied to PEME for both with and without ORC configuration, having an ORC is advantageous both in terms of superior Exergy Efficiency and lower LCOEn. The proposed configuration is also economically more lucrative with higher Net Present Value(NPV) and Benefit to Cost Ratio(BCR). For example, when PEME power input for both the cases is 10 MW, proposed system has NPV = 201.79 Million USD & BCR = 1.70 compared to NPV = 164.03 Million USD & BCR = 1.58 for without ORC configuration. Even if in without ORC configuration, no electrical power is supplied to the electrolyzer, adding an ORC to produce Hydrogen will still achieve maximum 1.57% Exergy Efficiency increment, compared to only electrical power production by sCO2 Brayton cycle. It is seen that in base condition, the NPV is still superior for the proposed configuration (203.03 to 189.32 Million USD), and the BCR dips only slightly from 1.72 to 1.71.

A statistical physics-based methodology for evaluating the efficiency of an adsorption refrigeration cycle using C3H2F4/Maxsorb III

Recently, the statistical physics modeling found a great success in the description of various aspects of adsorption phenomena such as olfaction, depollution, and photovoltaic processes. Therefore, we attempted here to apply this treatment in the domain of refrigeration by an adsorption/ desorption process cycle, using the grand canonical formalism of the statistical physics as a working tool. So, for this study, four advanced equations based on statistical physics treatment are used to clarify the adsorption process at molecular level and define its physico-chemical parameters for refrigeration applications. Our results showed that the double layer model with two energies provides useful details concerning this phenomenon by determining the number of captured HFO-1234ze (E) (C3H2F4) molecules per site nAM, the density of receptor site Drs, the adsorption quantity at saturation N a sat and two energetic parameters Phs1 and Phs2. The steric results revealed that the adsorbed C3H2F4 molecules tended towards a parallel position when the temperature increased. Evaluations of the adsorption energies and enthalpy values indicated that the anchoring process is exothermic and of a physisorption nature. In order to improve the thermodynamic efficiency, the coefficient of performance was calculated by analyzing changes in thermodynamic functions, giving a value of 0.58 for the C3H2F4 / Maxsorb III. Also, the COP value can be enhanced by using the same adsorbate with high compressibility to minimize the machine size but changing the present adsorbent by activated carbon derived from biomass such as: Waste Palm Trunk (WPT-AC) and Mangrove wood (M−AC).

Predator-induced defense decreases growth rate and photoprotective capacity in a nitrogen-limited dinoflagellate, Alexandrium minutum

Some dinoflagellates produce toxic secondary metabolites that correlate with increased resistance to grazers. The allocation costs of toxin production have been repeatedly addressed, but with conflicting results. Few studies have considered the potential costs of this defense to the photosystem, even though defense toxins (e.g., karlotoxins and brevetoxins) are closely linked to the photoprotective process. Here, we used chemical cues from copepods to induce paralytic shellfish toxin (PST) production in resource-limited Alexandrium minutum and quantitatively determined the growth rate and potential trade-offs with the photosystem process. The results show that grazer-induced, more toxic A. minutum had larger cell volume, lower cell division rate, and lower pigment content under nitrogen-limited conditions than control cells. In addition, predator cues led to a lower relative abundance of photoprotective xanthophylls and a reduced de-epoxidation efficiency of the xanthophyll cycle under high light conditions, reducing the ability of the cells to resist photodamage. Decreased photoprotective capacity may reflect an overlooked defense cost of toxin production.

The novel and slowest arterial pressure waves: clinical implications in children with congenital heart disease following cardiovascular surgery.

Certain rhythmic arterial pressure waves in humans and animals have been noticed for over one century. We found the novel and slowest arterial pressure waves in children following surgical repair for CHD, and examined their characteristics and clinical implications. We enrolled 212 children with 22 types of CHD within postoperative 48 h. We monitored haemodynamics (blood pressure, cardiac cycle efficiency, dP/dTmax), cerebral (ScO2), and renal (SrO2) oxygen saturation every 6 s. Electroencephalogram was continuously monitored. Mean blood flow velocity (Vm) of the middle cerebral artery was measured at 24 h. We found the waves with a frequency of ∼ 90 s immediately following surgical repair in 46 patients in 12 types of CHD (21.7%), being most prevalent in patients with aortic arch abnormalities (Aorta Group, n = 24, 42.3%) or ventricular septal defect (Ventricular Septal Defect Group, n = 12, 23.5%). In Aorta and Ventricular Septal Defect Groups, the occurrence of the waves was associated with lower blood pressures, dP/dTmax, cardiac cycle efficiency, ScO2, SrO2, Vm, worse electroencephalogram background abnormalities, higher number of electroencephalogram sharp waves, and serum lactate (Ps <0.0001-0.07), and were accompanied with fluctuations of ScO2 and SrO2 in 80.6% and 69.6% of patients, respectively. The waves observed in children following cardiovascular surgery are the slowest ever reported, occurring most frequently in patients with aortic arch abnormalities or ventricular septal defect. While the occurrence of the waves was associated with statistically worse and fluctuated ScO2 and SrO2, worse systemic haemodynamics, and electroencephalogram abnormalities, at present these waves have no known clinical relevance.

Thermodynamic analysis of supercritical CO2 power generation system for waste heat recovery with impurities in CO2

Waste heat recovery from gas turbines is an effective method for meeting the demand for a more efficient and cleaner energy system with decreased CO2 emissions and lower environmental pollution. The supercritical CO2 Brayton cycle is a promising power conversion system for waste heat recovery. The advantage of the supercritical CO2 Brayton cycle can be attained based on its physical characteristics. However, when another fluid is mixed as an impurity in a system using pure CO2, physical characteristics of working fluid was changed and operation at the design point can be challenging. Therefore, it is important to verify the purity of CO2 and understand the effect of impurities in CO2 in advance. This study examined the effects of impurities in the working fluid of a supercritical CO2 power generation system for actual demonstration facilities. The effect of impurity, a CO2-based mixture, in a supercritical CO2 power generation system on waste heat recovery from an LM500 gas turbine was investigated. A purity test of industrial grade CO2, which was noted as 99.9 % pure by the supplier, was conducted to verify the composition of the working fluid. The results of the purity test showed that the supplied CO2 consisted of 99.076 % CO2 along with nitrogen, argon, oxygen, water, and methane. Based on the results of the purity test, sensitivity analyses of the CO2-based binary mixtures and industrial mixtures were performed. A design point analysis was conducted for the CO2-based industrial mixture in comparison with pure CO2, which has cycle efficiency of 16.15 %, gross power of 510.03 kW, mass flow rate of 12.55 kg/s, and waste heat recovery of 2119.06 kW. In the case of fixed waste heat with mass flow rate of 14.417 kg/s, the cycle efficiency decreased by 0.39 % and gross power increased by 66.14 kW. In the case of fixed mass flow rate with 1844.598 kW waste heat, the cycle efficiency decreased by 0.32 % and gross power decreased by 9.84 kW. In addition, the influence of the performance of the major components on the system performance was investigated.

Optimisation of Brayton cycle CO2-based binary mixtures: An application for waste heat recovery of marine low-speed diesel engines exhaust gas

The energy-saving capabilities and efficient operation of marine low-speed diesel engines (MLDE) is a key emphasis for the main power source for ocean transportation. The purpose of the supercritical carbon dioxide recompression Brayton cycle (SCRBC) is to capture and utilise waste heat emitted by the engine's exhaust gas. However, the SCRBC performance will be severely affected by the large temperature fluctuations of ocean-going vessels during operation and high ambient temperatures in the cabin. A SCRBC model was built using the exhaust gas test data as the boundary conditions and validated using the Sandia National Laboratory (SNL) test data. The physical characteristics of the working fluids were evaluated by adding other fluids to CO2 in specific proportions to modify the critical point and increase cycle efficiency. The results demonstrated that employing CO2-based binary working fluids with low alkane and hydrogen sulfide (H2S) enhanced the recovery power, with the most significant increase obtained by the addition of 16.48 % H2S, which increased the power by 9.72 kW and improved the Brayton cycle efficiency by 3.31 %. Compared to the MLDE at 100 % load, the total efficiency increased by 1.77 % and the BSFC decreased by 6.76 (g kW−1 h−1) using CO2-H2S as the working fluid. The analysis of the SCRBC system component exergy losses showed that the cooler had the highest exergy losses. Adding other fluids to CO2 reduced the exergy losses of each component with the SCRBC system exergy losses decreasing from 162.97 to 129.90 kW and the exergy loss efficiency decreasing from 24.24 % to 22.65 %. The use of CO2-based binary working fluids specifically designed for ambient temperature may be expanded to other engines to enhance the efficiency of waste heat recovery.

Design optimization and off-design performance analysis of one-dimensional supercritical CO2 Brayton cycle

Supercritical carbon dioxide (SCO2) recompression Brayton cycle (RBC) is an encouraging technology for thermal power conversion and heat harvest for a wide range of heat sources due to its high-efficiency, low auxiliary power consumption, and compact size. However, most studies on its design and off-design performance analysis have been limited to the simple zero-dimensional component models without considering aerothermodynamics and ambient conditions. In this study, we developed a set of fully one-dimensional components models for SCO2 compressors, turbines, and heat exchangers, and, then, applied them to the multi-objective design optimization of a SCO2 cycle targeting a 50 MW net power output. The cycle off-design performance analysis methods and the control strategies were developed to countermeasure the performance degradation against the varying cooling water temperatures and part loads. The multi-objective cycle design optimization demonstrates that the cycle thermal efficiency and total product unit cost can be 0.476 and 11.652$/GJ, respectively, for the 50 MW SCO2 RBC cycle. The choke margin of the main compressor is 0.136 less than that of the re-compressor, and condensation can lead to a sharp decline in efficiency under high-flow conditions, causing the earlier onset of choking. The off-design performance analysis shows that the turbine inlet pressure control improves cycle efficiency below the design point of 317 K but does otherwise above the point. In contrast, inventory control strategies can maintain stable cycle efficiency and achieve adjustable net power output between 10 % and 110 %. The findings have the potential to advance further the commercial application of SCO2 cycles in high-temperature thermal energy systems.

Ranking Energy Storage Technologies Using Analytical Hierarchy Process (AHP) and VIKOR

Abstract Due to increasing global average temperatures, it is imperative to increase investment in renewable energy and energy storage technologies to reduce the negative impact to the environment. As such, improvements associated with renewable energy intermittency and variability is a priority. One solution is through the use of energy storage technologies (ESTs) to improve the reliability and stability of power supplies. ESTs come in various selections, each with its own application and attributes. Since no EST is universally applicable, utilization of MADM methods helps in narrowing selected technologies in a specific application. In this study, a hybrid AHP and VIKOR method is utilized for stationary power applications. AHP is used for determining weights associated with each EST attribute from surveyed experts in academe and industry. The attributes efficiency and cycle life obtained the highest weights of 0.2384 and 0.2322 respectively. VIKOR is used in ranking ESTs based on available data gathered. Supercapacitor is ranked as best alternative due to its cycle efficiency, storage lifetime, power capacity, and power density. Subsequent rankings are flywheel, pumped-hydro, and lithium-ion battery. Technology readiness level and specific application details could be incorporated in further studies to improve ranking. This study demonstrates the potential of hybrid AHP-VIKOR in guiding researchers and decision makers select the appropriate EST given competing performance in different criteria.

A micro-channel cooling system with two-phase looped thermosyphon for a supercritical CO2 Brayton cycle

The supercritical Carbon Dioxide (sCO2) closed Brayton cycle is a promising power generation technology, while the efficient cooling of CO2 and precise control of Compressor Inlet Temperature (CIT) is crucial for the high cycle efficiency and stable compressor operation due to the acute variation of thermophysical properties in the near-critical region. In conventional indirect cooling scheme, an intermediate single-phase water circuit is used to transfer heat from CO2 to water at the precooler, and then from water to the environment at the cooling tower, having the disadvantage of large pumping work consumption and high thermal resistance. In this work, a self-driven two-phase looped thermosyphon that significantly enhances the heat transfer by internal evaporation and condensation, is proposed to replace the water circuit. An experimental ultra-compact cooling system, consisting of a looped thermosyphon combined with micro-channel evaporator and condenser, filled with R134a coolant, is designed, fabricated, and tested. Visualized observation of the two-phase flow pattern and simultaneous measurement of the temperature, pressure and mass flow rates are conducted. A nodal analysis method is adopted, and a MATLAB code is developed for analyzing the internal fluid flow and the coupled sCO2-R134a-Air heat transfer, which is validated by experiment data. The results show that, the CO2 temperature could be accurately maintained at a specified near-critical point with a fluctuation of less than 1 K, and the average heat-releasing temperature can be reduced, while considerable pumping work, usually accounting for 2–5 % of the rated power output can be saved, thus contributing to increased cycle efficiency and system compactness.

Impact Quality Indicators onto Sustainable Manufacturing

This paper dealt study effect quality indicators of crushing Limestone process in quarries onto Sustainable Manufacturing. Sustainable Environment was achieving through minimizing quality indicators which were use resources and lead time during crushing of limestone in position. Non-value added time and use resources are studied in this paper. This paper aims to show impact key performance indicators of quality which were production efficiency, efficiency of manufacturing cycle and efficiency of use resources onto Operational and environmental sustainability in order to reduce environmental and operational impacts onto environment and human health. Crushing Limestone process had been employing on one year as a case study to evaluate operational and environmental sustainability of an Iraqi industry. Program of Minitab-Version 17 was employed to analyze information of production process. Results illustrated that the rate of efficiency of utilized resources and waste of resources on one year were 95% and 5%. Conclusions shown lead time was an important performance measure of quality from sustainable Manufacturing perspective.

Development of a novel renewable energy-based integrated system coupling biomass and H2S sources for clean hydrogen production

The present work aims to develop a novel integrated energy system to produce clean hydrogen, power, and biochar. The Palmaria palmata, a type of seaweed, and hydrogen sulfide from the industrial gaseous waste streams are taken as potential feedstock. A combined thermochemical approach is employed for the processing of both feedstocks. For clean hydrogen production, the zinc sulfide thermochemical cycle is employed. Both stoichiometric and non-stoichiometric equilibrium-based models of the proposed plant design are developed in the Aspen Plus software, and a comprehensive thermodynamic analysis of the system is also performed by evaluating energy and exergy efficiencies. The study further explores the modeling, simulation, and parametric analyses of various subsections to enhance the hydrogen and biochar production rate. The parametric analyses show that the first step of the thermochemical cycle (sulfurization reaction) follows stoichiometric pathway and the ZnO to H2S ratio of 1 represents the optimal point for reactant conversion. On the other hand, the second step of the thermochemical cycle (regeneration reaction) does not follow a stoichiometric pathway and ZnS conversion of 12.87% is achieved at a high temperature of 1400oC. It is found that a hydrogen production rate of 0.71 mol/s is achieved with the introduction of 0.27 mol/s of H2S. The energy and exergy efficiencies of the zinc sulfide thermochemical cycle are found to be 65.23% and 35.58% respectively. A biochar production rate of 0.024 kg/s is obtained with the Palmaria palmata fed rate of 0.097 kg/s. The Palmaria to biochar energy and exergy efficiencies are found to be 55.43% and 45.91% respectively. The overall energy and exergy efficiencies of the proposed plant are determined to be 72.88% and 50.03% respectively.

Enhanced adsorption and regeneration performances for methyl mercaptan capture by a metal–organic framework incorporated in a mesoporous silica

Cu-modified adsorbent is widely used in removing S-containing odor pollutant, such as methyl-mercaptan (CH3SH). Increasing the dispersion of adsorptive sites and improving the regeneration cycle efficiency are two important problems. In this work, a copper metal–organic framework (MOF) was synthesized by in-situ growing the Cu-MOF on SBA-15. Micro-morphology characterizations revealed that the Cu-MOFs grew inside the SBA-15 mesopore channels and showed a good dispersion. When the hybrid (Cu-MOF in SBA-15) and the Cu-MOFs were compared for the CH3SH removal, the hybrid removed 1.70-mol CH3SH per mol of Cu in the adsorbent. This adsorbent capacity was far bigger than Cu-MOFs (0.70 mol·mol−1) and resulted from a better Cu-MOFs dispersion in SBA-15. Additionally, an easy and energy-saving hydrothermal method was put forward for the regeneration of the used adsorbent at 80 °C. The capacity of the regenerated material was higher than 70 % for at least 6 cycles. In addition, the regeneration temperature was far lower than that (> 350 °C) generally utilized in previous reports investigating cycled adsorption of CH3SH. The enhanced regeneration performances were attributed to the confinement effect of the SBA-15, which restrained the ligand around the Cu coordination centers. This work confirms the effective removal of odor-gas using a cost-effective regenerable adsorbent.

Optimizing Concentrated Solar Power: High‐Temperature Molten Salt Thermal Energy Storage for Enhanced Efficiency

ABSTRACTMolten salts (MSs) thermal energy storage (TES) enables dispatchable solar energy in concentrated solar power (CSP) solar tower plants. CSP plants with TES can store excess thermal energy during periods of high solar radiation and release it when sunlight is unavailable, such as during cloudy periods or at night. This capability allows these plants to provide reliable, dispatchable power, ensuring a continuous electricity supply to the grid. This paper examines the challenges and opportunities of utilizing higher‐temperature molten salt formulations to enhance power cycle efficiency. Drawing on existing literature, performance analysis of existing power plants, and novel simulation results, we project the expected technological improvements by the end of this decade. By using 15 h of TES and a higher temperature MS formulation, with heat transfer fluid hot temperatures of 700°C, and a power cycle 350 bar 700°C of efficiency 48%, the annual electricity production from a 115 MW power plant in Daggett, California is 688 GWh, the total installed cost is $684 m while the 25‐year LCOE is 6.37 c/kWh.

Novel Recuperated Power Cycles for Cost-Effective Integration of Variable Renewable Energy

The ongoing transition to energy systems with high shares of variable renewables motivates the development of novel thermal power cycles that operate economically at low capacity factors to accommodate wind and solar intermittency. This study presents two recuperated power cycles with low capital costs for this market segment: (1) the near-isothermal hydrogen turbine (NIHT) concept, capable of achieving combined cycle efficiencies without a bottoming cycle through fuel combustion in the expansion path, and (2) the intercooled recuperated water-injected (IRWI) power cycle that employs conventional combustion technology at an efficiency cost of only 4% points. The economic assessment carried out in this work reveals that the proposed cycles increasingly outperform combined cycle benchmarks with and without CO2 capture as the plant capacity factor reduces below 50%. When the cost of fuel storage and delivery by pipelines is included in the evaluation, however, plants fired by hydrogen lose competitiveness relative to natural gas-fired plants due to the high fuel delivery costs caused by the low volumetric energy density of hydrogen. This important but uncertain cost component could erode the business case for future hydrogen-fired power plants, in which case the IRWI concept powered by natural gas emerges as a promising solution.

Optimization of biomass-fueled multigeneration system using SOFC for electricity, hydrogen, and freshwater production

The rapid depletion of fossil fuel resources and their detrimental impact on the environment necessitates the exploration of renewable energy alternatives. Biomass stands out as a reliable renewable source, especially in multigeneration systems. This study suggests a biomass-driven multigeneration configuration for the production of electricity, heating, hydrogen, and freshwater. The configuration is evaluated from thermodynamic and economic perspectives, utilizing an Artificial Neural Network to predict key outcomes. The system optimization process integrates Machine Learning with decision-making methods to achieve optimal conditions. The findings highlight that an anode-cathode gas recycling design is the most effective configuration for the Solid Oxide Fuel Cell unit, achieving a cycle efficiency of 67.68% and a product cost of $11.41/GJ. Municipal Solid Waste biomass and CO2 were identified as the most efficient fuel and gasification agents, respectively. The evaluations also determined that the integration of the multi-objective grey wolf optimizer and the CatBoost method is the most reliable machine learning model for optimization. Furthermore, by combining the Multi-Objective Harris Hawks Optimization algorithm with TOPSIS, LINMAP, and Fuzzy decision-making approaches, the system achieves optimal performance across multiple scenarios. In one scenario, the system reached an exergy efficiency of 67.68% and a hydrogen production rate of 22.34 kg/h. The optimum recycling ratios for the anode and cathode were determined to be 0.16 and 0.38, respectively. The study demonstrates the feasibility of the proposed configuration, offering significant potential for sustainable and cost-effective energy generation.

Development and Assessment of the Performance of a Novel Parabolic Trough Solar Collector-Driven Three-Stage Cooling Cycle

Abstract A gaseous flow is employed as heat transfer fluid (HTF) in a parabolic trough solar collector (PTSC) for simultaneous production of cooling at three different levels of temperature to meet the demands of air conditioning, refrigeration, and ultra-low-temperature refrigeration required to ensure the efficacy of some special vaccines. The combined system consists of five subsystems including PTSC, Kalina cycle (KC), ejector refrigeration cycle (ERC), cascaded refrigeration cycle (CRC), and absorption refrigeration cycle (ARC). A simulation through an engineering equation solver (EES) is conducted to assess the impact of internal tube diameter of absorber and solar irradiation on rise of HTF temperature and mass flowrate of Kalina cycle fluid. It is determined that for given solar irradiation, the temperature of HTF goes down when internal diameter of absorber tube is enlarged. The influence of weather conditions; solar irradiation and ambient temperature, type of HTF, and concentration of ammonia–water basic solution on thermal and exergy efficiencies of three-stage cooling cycle (TSC) are examined. The TSC with helium-operated PTSC delivers better results than air and CO2. Exergy analysis shows that solar collector (30.26%) dissipates the highest exergy, followed by the ejector (12.5%) and vapor generator subsystem (7.61%). The type of CRC fluid pair affects TSC cycle refrigeration capacity and cooling exergy efficiency. The promotion of solar irradiation from 850 to 1200 W/m2 increases the cooling exergy efficiency of the three-stage cycle from 6.72% to 9.52% when the evaporator temperature is set at −45 °C and CRC employs NH3-propylene.

Energy features of CO2-cycles during oxygen combustion of methanol

The PURPOSE of the work is to determine the mass-flow characteristics of working substances and energy indicators of an installation based on a CO2 cycle with a two-stage pressure increase (Allam cycle) during oxygen combustion of methanol.METHODS. A research methodology is presented in which the mass-flow characteristics of working substances are determined based on the reactions of combustion and synthesis of methanol and electrolysis of water. These reactions are basic for ensuring operational processes in the installation. The method is based on the molar ratios of substances participating in reactions under stoichiometric conditions. Using the thermodynamic parameters of the cycle being implemented and at a given installation power, the consumption of the working fluid, the share of carbon dioxide renewal in the cycle, the amount of methanol produced in the synthesis unit, the amount of fresh methanol, the amount of hydrogen produced in the water electrolysis unit and the amount of oxygen are determined, necessary to ensure fuel combustion processes. At the same time, the amount of commercial hydrogen is determined. Electricity consumption for own needs is determined using regulatory methods and data from equipment manufacturers.RESULTS. The article shows that with similar values of thermal efficiency of CO2 cycles based on oxygen combustion of methane and methanol, the amount of carbon dioxide removed from the cycle for disposal is 11% less. It has been shown that a CO2 cycle operating on methanol is capable of producing commercial hydrogen simultaneously with electricity generation. The specific electricity consumption for hydrogen production is 22% less than for its production without combination with the CO2 cycle.

Comparative study on productivity of double slope solar still using different wick and energy storage materials

The aim of the proposed study is to evaluate the efficiency of Double Slope Solar Still (DSS) using different wick and energy storage materials. In the study, wick materials such as jute, cotton and sponge were used in combination with energy storage materials such as mild steel, cast iron and copper. The experiments were conducted using DSS with different combinations of wick and energy storage materials to determine the efficient performance combination. The results show that sponge and copper have higher efficiency with wicks and energy storage materials. The results show that the maximum amount of water produced in a single day was 3147 ml when the DSS system was used with a combination of sponge and copper materials. This range shows an increase of 17.47 % and 12.44 % over the DSS with jute and copper and the DSS with the combination of cotton and copper respectively. The DSS showed the highest average energy efficiency when used in conjunction with a combination of sponge and copper, namely 51 % of the average efficiency. This corresponds to an increase of 18.60 % and 10.86 % compared to the combination of DSS with jute and copper and the combination of DSS with cotton and copper respectively. The best evaporation heat transfer coefficient of 345 W/m2K was determined for the combination of DSS with sponge and copper. Average exergy efficiency is also maximum of 3.076 % for the DSS with sponge and copper materials, which is higher than other investigated combinations. The proposed system has an energy payback period of 1.26 years, an energy production factor of 0.78, a life cycle efficiency of 6.9 % and a cost of $0.031 per litre of water produced in the environmental economic analysis.

Comprehensive analysis and thermo-economic optimization of the dry cooling system for supercritical CO2 power cycle

This paper presents a comprehensive analysis and optimization of the dry cooling system for the supercritical CO2 (sCO2) power cycle, a promising technology for generating electricity from renewable heat sources. Unlike prior studies that concentrated solely on specific cooling system components, this paper examines thermoeconomic factors and employs mathematical models to analyze how various operational parameters impact both the cooling system's performance and cost, as well as the overall power cycle. Additionally, the paper employs a multi-objective optimization method to determine the optimal parameter values across varying cooling capacities and ambient temperatures. The results show that the thermal efficiency of the power cycle does not increase linearly with the cooling capacity, due to the change in CO2's physical properties near the temperature and pressure where it behaves like both a liquid and a gas (the pseudo-critical point). Furthermore, optimal cooling system area varies based on cooling capacity and ambient temperature, leading to cost reduction and improved power system efficiency. This paper provides a useful tool and guidance for designing and operating the dry cooling system for the sCO2 power cycle.

Peroxymonosulfate promoted dioxygen activation with Mn(II)-nitrilotriacetic acid complexes for sulfadiazine degradation

In the field of peroxymonosulfate (PMS) activation technology, there is a pressing need to reduce PMS consumption and enhance its utilization rate. The present study demonstrates that the introduction of dissolved oxygen (DO) into the Mn(II)-nitrilotriacetic acid (NTA)-activated PMS system significantly enhances the degradation efficiency of sulfadiazine and increases the PMS utilization rate from approximately 15.0 to 41.3 %. Mechanistic analysis reveals that the Mn(II)-NTA/PMS system generates sulfate radicals as well as intermediate valent manganese species in the absence of DO; while in the presence of DO, Mn(II) is oxidized to Mn(III) by dioxygen to form superoxide anions and Mn(III), which can be further oxidized by PMS to higher valence states such as Mn(V) and Mn(VII). Consequently, the production of free radicals decreases while intermediate valent manganese species become more abundant. Additionally, O2•− can also reduce both Mn(VII) and Mn(IV) back to their lower oxidation state (Mn(II)). The cooperative interactions between these active species enhance the efficiency of catalytic cycles of manganese species. Moreover, the influence of multiple factors, the degradation products, and their associated toxicity assessment were investigated. Overall, this research provides valuable insights into the design of highly efficient PMS and DO activation systems.