Increment In Efficiency Research Articles

Microwave-boosted elemental mercury removal using natural low-grade pyrolusite

Utilizing natural minerals to remove Hg0 from flue gas was regarded as a preferable route to control mercury pollution. This paper purposed a novel microwave (MW)-boosted removal method using natural low-grade pyrolusite (NLP), by which over 85 % of Hg0 was removed and approximately 10–20 % of the increment of efficiency was obtained. Compared with thermo-catalysis, MW also empowered NLP with a wider active-temperature range (100–250 °C) and better H2O and SO2 resistances. Kinetic analysis showed that MW increased the rate constant and reduced the activation energy, Hg-TPD and material balance analyses demonstrated that major Hg0 was chemisorbed as HgO. Via the thermal treatment experiments, the regeneration performance of NLP was confirmed to be good. From the experiments and characterizations, the mechanism was preliminarily speculated: (i) the contribution order of the active components was MnO2 > Mn3O4 > Fe2O3; (ii) the redox pairs of Fe(II)/Fe(III) and Mn(III)/Mn(IV), as well as the O-species, involved in the conversion from Hg0 to HgO. Density functional theory calculations revealed the pathway and mechanism: (i) MnO2 exhibited higher oxidation activity, whereas Mn3O4 showed higher adsorption activity; (ii) Odis derived from Oads enhanced the removal of Hg0 by increasing the adsorption energies and amounts of transferred electron; (iii) Oads had advantages over Olat in term of desorbing HgO, which was the rate-determining step.

Investigation of ZVS Criteria and Optimization of Switching Loss in a Triple Active Bridge Converter Using Penta-Phase-Shift Modulation

Triple active bridge (TAB) as an isolated multiport dc–dc converter is a promising solution for integrated energy management systems to maintain an efficient power flow between the ports. This article presents the design, modeling, and switching loss optimized phase-duty-controlled PWM modulation scheme of a TAB converter composed of three full-bridge modules and a high-frequency planar transformer. The work aims at the derivation and analysis of the zero-voltage switching (ZVS) conditions for a TAB, where the turn-on switching loss is mitigated along with attaining an improved EMI performance, comprising of reduced noise peaks. Moreover, an optimized five-variable control-based TAB PWM modulation technique is proposed in this article in order to achieve minimized switching loss and the overall system loss for a wide voltage gain and load range. The instantaneous switching currents, responsible for the switching losses at the devices, are derived from the transformer winding current expressions, formulated employing the generalized harmonic approximation (GHA) technique. The various loss minimization techniques and the theoretically obtained criteria for ZVS are experimentally verified using a laboratory-developed prototype of an 800-W TAB converter. With the implementation of the proposed optimal phase-duty control, the experimental results show a nonunity gain light-load efficiency increment up to 10% compared to the conventional phase-shift modulation alone.

Thermodynamic analyses of a novel hybrid photovoltaic-thermal (PV/T) module assisted vapor compression refrigeration system

Buildings have a respectable share of global energy consumption and it is well-known that refrigeration, heating and air conditioning systems have crucially contributed to this share. Therefore, even a small improvement in these systems has a noteworthy potential in globally saving energy. Accordingly, the performance of Photovoltaic-Thermal module-assisted vapor compression refrigeration system (PV/T-VCRS) has been handled in the present research. PV/T-VCRS has been integrated with PV module, refrigeration system, and their hybrid. Additionally, different from the conventional superheating methods, superheating has been performed with a PV/T module in this work. In order to discuss the system performance, and observe the differences between conventional and modified hybrid systems, energy and exergy analyzes have been applied. In the results, the average PV module surface temperature in PV module and PV/T-VCRS is recorded to be 56.16 °C and 40.93 °C, respectively. This case leads to a direct increment in PV module electrical efficiency. Electrical efficiency, average electrical efficiency in PV module, and PV/T-VCRS are calculated to be 13.49% and 14.69%, respectively. The average COP values are found to be 5.23 for VCRS, and 5.68 for PV/T-VCRS. Total exergy destruction in VCRS and PV/T-VCRS has been calculated to be 175.85 W and 443 W. On the other hand, the exergy efficiency is found to be 50.79% in VCRS and 60.73% in PV/T-VCRS. In the conclusion, it is well-noticed that hybrid PV/T-VCRS presented promising results in terms of electrical efficiency, COP, energy, and exergy analyses as compared to those of the conventional system.

Thermodynamic study on energy crops thermochemical conversion to increase the efficiency of energy production

The actual paper analyses the performance of different energy crop biomasses, Miscanthus x giganteus Greef et Deu (EC-1) and Arundo donax L. (EC-2) stems, during slow pyrolysis process monitored by simultaneous TG-DTG-MS techniques, through chemical exergy analysis. In addition to considering the physical and chemical characteristics of given feedstocks for their efficient thermo-chemical conversion into pyrolytic gas, in this study, a theoretical simulation for their implementation use in the gasification process was also performed. The performed thermodynamic study with detailed exergy analysis showed that the large contribution of exergy in syngas components such as CO and H2 originates primarily from cellulose pyrolysis of EC-1, while large exergy contribution in syngas component as CH4 originates from lignin pyrolysis of EC-2. It was founded that the exergy efficiency of syngas for EC-1 equals 19.04%, which is lower than the exergy efficiency of syngas for EC-2 (20.46%), as a result of higher ash content in EC-1. Also, it was reported that higher carbon (C) and hydrogen (H) contents present in the EC-2 sample generate higher gaseous energy and exergy values, i.e. the increment of exergy efficiency of syngas, by both approaches (pyrolysis and gasification exergy analysis), but results in a lower biomass chemical exergy (18.28 MJ kg−1). The methodology applied to the gasification process was shown a higher exergy efficiency for EC-2 (∼36 – 42%) than for EC-1 (∼33 – 39%), dependant on the equivalence ratio (ER).

The influence of component parameters on cycle characteristic in rotating detonation gas turbine

A cycle calculation model of methane-air directly mixing rotating detonation gas turbine was built combining two-dimensional numerical simulations of rotating detonation combustor (RDC) with convergent inlet structure. Controlled variable method was used to investigate the cycle performance improvement for different component parameters compared with traditional gas turbine, and sensitivity analysis to gain the influence weight of component parameters was carried out. The results demonstrated that cycle efficiency increasing rates were all more than 11.5% in simulated conditions. With the decrease of compressor ratio, compressor efficiency, turbine efficiency and equivalence ratio of RDC, cycle net power increments were all in a downward trend, while cycle efficiency increment showed different variation trends especially when equivalence ratio of RDC and compressor pressure ratio decreased. Turbine efficiency was the most significant factor for cycle performance improvement and the influence of compressor efficiency had been stable. Compressor pressure ratio had different influence weights on cycle efficiency increment when above and below 8.00. Equivalence ratio of RDC had an opposite effect on cycle efficiency increment and different influence weights on net power increment when above and below 0.75.

A Comparative Study of Impeller Modification Techniques on the Performance of the Pump as a Turbine

The extensive use of the pump as a turbine (PAT) for micro-hydropower applications has a significant value from economic and technical viewpoints. However, the unavailability of the characteristics curve and relatively lower efficiency are the two basic limitations when considering pumps for power-generating applications. In this paper, the performance of the PAT is analyzed using the computational fluid dynamics (CFD) software called Ansys CFX in conjunction with standard k - ε . Then, experiments were done to verify the results of the simulation. Measurement inaccuracy effects are also taken into account. The initial performance of the PAT is refined by controlling basic design parameters (i.e., increasing the number of impeller blades, decreasing blade thickness, blade tip rounding, and adjusting blade inlet angle). Additionally, a new modification method known as blade grooving is also introduced in this research. Finally, all listed modification techniques are applied simultaneously to achieve maximum performance. The output of the study confirms that the adopted modification techniques have a positive effect on performance improvement. When the number of impellers is increased, the power output is enhanced by 5.72%, and blade grooving provides the most efficiency improvement, i.e., 7.00%. But decreasing blade thickness has no remarkable impact on the performance; the power output and efficiency are improved by 1.24% and 2.60%, respectively. The maximum performance improvement was achieved when the modification techniques are applied simultaneously with 10.56 and 10.20 percent of power and efficiency increments, respectively. From the entire study, it can be concluded that the chosen design parameters have an important effect on stabilizing the internal flow, decreasing the required head, decreasing the hydraulic loss in the impeller, and increasing the overall performance. The study also helps to figure out which modification technique is the most practical.

An enhanced arithmetic optimization algorithm for global maximum power point tracking of photovoltaic systems under dynamic irradiance patterns

ABSTRACT The photovoltaic power system is highly dependent on the quantity of solar irradiance incident on it and its temperature. These parameters are dynamically changing with time due to climatic changes, shadows formed by clouds, trees, buildings, and so on, resulting in multiple maximum power points (MPP). Out of which one is global MPP (GMPP) and the rest are local MPP (LMPP). The GMPP varies dynamically along with the weather conditions and connected load. Many GMPP tracking (GMPPT) algorithms were developed which are inefficient and ineffective under dynamic irradiance conditions. This paper proposes a new enhanced arithmetic optimization algorithm based on the levy flight (AOA-LF) as a GMPPT method, which improves the tracking efficiency and tracking speed because of its good exploration and exploitation due to the long jump with a variable step size. The suggested AOA-LF GMPPT method is implemented in MATLAB/SIMULINK and tested with eight different dynamic irradiance patterns whose tracking curves are compared with the existing GMPPT algorithms like JAYA-LF, DFO, AOA, PSO, and P&O, which reveals that it is excellent in the tracking of GMPP with increment in efficiency as high as 19% when compared with P&O method and the least time to reach the GMPP with percentage decrement as high as 69% as compared to the PSO method. Also, the proposed AOA-LF GMPPT method is validated with the help of OPAL-RT OP4510 Real-Time Digital Simulator. Hence, the proposed algorithm shows superior performance with zero steady-state oscillations and also enhanced exploration and exploitation.

Numerical investigation on the performance and vapor injection process of a scroll compressor with different injection features

Using the vapor injection scroll compressor in heat pump systems for electric vehicles is one of the promising solutions for promoting the driving range in extremely cold climates. In this paper, a three-dimensional transient simulation model of the vapor injection scroll compressor with different injection features, including injection positions, shapes, and inclinations, is established and verified with a deviation within 8 %. And the influence of the injection flow on the internal flow field and the performance of the scroll compressor is the key problem to be studied. The results show that when the injection port gets closer to the discharge port, the increment of isentropic efficiency and the decrement of discharge temperature increase, and the maximum values can reach 6.7 % and 11.3 K, respectively. From the results of the flow field distribution, the heat aggregation is observed at the internal engaging point, and a shock pressure and two vortexes occur at the bottom of the orbiting scroll as the injection flow rushes into the working chamber, which may bring the operational stability of orbiting scroll and leakage troubles. The heat aggregation is weakened with a smaller injection inclination. Shock pressure gets smaller from single-circle injection port to waist and from the injection inclinations of 90° to 30°, with a reduction of 9.5 % and 26 % respectively. Overall, a vapor injection scroll compressor using a waist-shaped injection port with an injection inclination of 60° is recommended, which shows a better comprehensive effect.

Thermal Performance of a Counter-Flow Double-Pass Solar Air Heater With The Steady and Pulsating Flow

The present work studied the influence of pulsating flow as an active method on the thermal performance of a double-pass solar air heater with a tubular solar absorber. A ball valve has been used as a pulse generator mounted at the downstream flow of the solar air heater. The experiments were under indoor conditions with a constant heat flux of 1000 W/m2, and different air mass flow rates ranged from 0.01 to 0.03 kg/s. Moreover, the study covered three pulsation frequencies varied from 1 to 3 Hz. Based on the experimental outcomes, it can be observed that the heat transfer rate is enhanced by applying the pulsating flow, where it was found that the outlet temperature in the case of applying the pulsating flow rises by about 25.6 - 27% as compared with the steady flow case. Moreover, pulsating flow offers a higher effective thermal performance by about 15.2 % at the maximum air mass flow rate compared with the steady flow. In addition, the findings pointed out that varying the pulsation frequency from 1 to 3 Hz produces an enhancement in heat transfer rate and in solar heater effective efficiency, where it was found that when changing the frequency from 1 to 3, the increment of effective efficiency ranged from 3.8 to 6.9 % depending on the air mass flow value.

Aerodynamic design considerations for supercritical CO[formula omitted] centrifugal compressor with real-gas effects

The optimal supercritical carbon dioxide (SCO2) Brayton cycle requires the SCO2 compressor to operate near the critical point, where strong real-gas effects make the aerodynamic design much more challenging. Conventional semi-empirical aerodynamic design guidelines developed for air compressors are no longer applicable because CO2 flows undergo significant changes in thermophysical properties when inlet conditions of the SCO2 compressor change, when different design parameters are chosen, and when the phase change occurs. This paper proposed a set of new design guidelines for SCO2 compressors from zero-dimensional (0D), one-dimensional (1D), and three-dimensional (3D) perspectives. At 0D level, the concept of similitude is introduced to derive new performance correlations independent of inlet conditions. At 1D level, the coupling effect of thermophysical properties and design parameters is considered and new guidelines for preliminary design are proposed. At 3D level, detailed blade modeling procedures are discussed in order to improve compressor performance and suppress phase changes. All these design considerations are validated by redesigning and comparing several well-designed SCO2 compressors from open literature. The results show that for the compressor operating near the pseudo-critical line, an efficiency increment of about 0.7% can be obtained by adopting the proposed design considerations, while phase change can also be well suppressed at the same time.

Esterification efficiency improvement of carbon-based solid acid catalysts induced by biomass pretreatments: Intrinsic mechanism

Effect of various reagents (i.e. H2O2, H2SO4, H3PO4 and their mixtures) pretreatments on esterification activities of carbon-based solid acid catalysts synthesised by one-step sulphonation (150 °C for 4 h) was investigated. The results demonstrated that sulphonic acid density of catalyst positively correlated with the esterification efficiency and the high lignin content of the biomass stimulated the loading of sulphonic acid groups. The bamboo powder pretreated with 1% H2SO4 yielded the highest lignin content (from 26.4% to 33.0%). The corresponding catalyst yielded the highest esterification efficiency (97.3%), which decreased to 82.9% after four cycles. On the other hand, the bamboo powder pretreated by H2O2 and 30% H3PO4 brought little effect on the increment of lignin content and esterification efficiency of the catalysts. Therefore, biomass pretreatment could be a solution of disposal acidic wastewater (like catalyst sulphonation wastewater) by reusing it as pretreatment reagents and improving the esterification efficiency of the catalysts.

All-perovskite two-terminal tandem solar cell with 32.3% efficiency by numerical simulation

Metal halide all-perovskite tandem solar cell has shown great promise with enhanced power conversion efficiency beyond the limitation of a single junction cell. In this work, we have simulated all-perovskite tandem solar cells with a top cell of 1.75 eV wide-bandgap FA0.8Cs0.2Pb(I0.7Br0.3)3 and bottom cell with 1.25 eV (FASnI3)0.6(MAPbI3)0.4:Cl as main perovskite absorber materials through simulation on SCAPS-1D software. The simulated device shows an almost 13% higher power conversion efficiency value as compared to the experimentally achieved value in identical device configuration with the same materials. In addition to this, almost 54% increment in the power conversion efficiency to around 32.3% is achieved after simulating the improved tandem configuration gained from varying various transport layers along with alteration in their layer thicknesses. Decreased device resistance, easy transportation mechanism of charge carrier, along with defect-controlled simulation, has assisted in such a significant increase. This work provides a new direction for experimental realization with higher power conversion efficiency and establishes a new route toward the development of all-perovskite tandem solar cells.

Operation-dependent exergetic sustainability assessment and environmental analysis on a large tanker ship utilizing Organic Rankine cycle system

This study focuses on the novel perspective of marine ORC systems with a detailed marine diesel generator plant simulation integrated with an ORC system model to evaluate environmental impacts and energy efficiency increments by reducing the number or the load of generators by using the ORC system support during operation. It is aimed to analyze the fuel-saving potential and sustainability performance of the power generation plant of a tanker ship when an ORC is integrated. The thermodynamic system simulation determined the fuel consumption of the plant within two years regarding six operation modes. The results show that the optimum working fluid is R1336mzz (Z) for the evaporation pressure of 16 bar. Organic Rankine cycle system integration provided a total fuel-saving of 15% from diesel generators and the total fuel consumption of the vessel was reduced by 5.16%. The sustainability performance of the system was ensured with a novel operation-dependent approach that enhances the exergetic sustainability assessment by considering the operation modes of the vessel and the time spent on these operations for a certain time. The load reduction in the generators resulted in better sustainability performance and the operation-dependent indicators were affected by operations having more working hours.

Immediate Effects of Vagal Nerve Stimulation in Drug-Resistant Epilepsy Revealed by Magnetoencephalographic Recordings.

Objective: Vagus nerve stimulation (VNS) has been a neuromodulatory option for treating drug-resistant epilepsy (DRE), but its mechanism remains unclear. To obtain insight into the mechanism by which VNS reduces epileptic seizures, the immediate effects of VNS in brain networks of DRE patients were investigated when the patients' vagal nerve stimulators were turned on. Methods: The brain network properties of 14 DRE patients with a vagal nerve stimulator and 14 healthy controls were evaluated using magnetoencephalography recordings for 6 main frequency bands. Results: Compared with healthy controls, DRE patients exhibited significant increases in functional connectivity in the theta, alpha, beta, and gamma bands and significant reductions in the small-world measure in the theta and beta bands. During periods when patients' vagal nerve stimulators were turned on, DRE patients showed significant reductions in functional connectivity in the theta and alpha bands and a significant increase in the small-world measure in the theta band when compared with periods when patients' vagal nerve stimulators were turned off. Conclusions: Our results indicate that the brain networks of DRE patients were pathologically hypersynchronous and instantaneous VNS can decrease the synchronization of brain networks of epileptic patients, which might play a key role in the mechanism by which VNS reduces epileptic seizures. In the theta band, instantaneous VNS can increase the network efficiency of DRE patients, and the increment in network efficiency may be helpful for improving brain cognitive function in epileptic patients. Impact statement For the first time, we investigated the immediate effects of vagus nerve stimulation (VNS) in the brain networks of drug-resistant epilepsy patients using magnetoencephalography. Our results show that instantaneous VNS can decrease the hypersynchronization of epileptic networks and increase the network efficiency of epileptic patients. Our results are helpful in understanding the mechanism of action by which VNS reduces epileptic seizures and improves the cognitive function in epileptic patients and the brain network reorganization caused by long-term VNS.

Parametric optimization of novel solar chimney power plant using response surface methodology

CFD and experimental approaches are used to carry out the design of a Solar Chimney Power Plant (SCPP) that consists of a Semi Convergent Collector that is equipped with a Divergent Chimney. The present work engages in figuring out the importance of study variables in statistic modelling thereby improving the efficiency. Both the response surface methodology (RSM) and the single objective approach (SOA) are used in the process of determining the amounts of influential parameters and optimizing the model. Experiment test on a small-scaled model is carried out with inclined Collector to a Divergent Chimney. The CFD result indicates that the updraft effect increases because of the convergent collector with mean temperature rise of 18 K. Experiment and simulation results are in good agreement. The numerical model predicted that the increment in outside temperature leads to increment in mass flow rate, velocity, inside temperature, power output and efficiency of the plant. Hence the single input model predicted the values for five outputs. The numerical model seems to be fit with experimental study with an increase in mass flow rate from 0.04 kg/s to 0.06 kg/s with incremental time step. The deviation between the experimental and numerical studies lies only 0.423. Developing a larger size model helps in achieving larger power output. It is recommended that the semi convergent collector with a divergent chimney adopts for construction of large size SCPP for generating greener energy.

Defects passivation by solution-processed titanium doping strategy towards high efficiency kesterite solar cells

The performance of kesterite Cu2ZnSn(S,Se)4 (CZTSSe) thin films solar cells is limited mainly because of the two technical bottlenecks, including multilayer crystallization in non-hydrazine solvents, and the presence of severe non-radiative recombination within the absorber layer and/or heterojunction region, resulting in large open-circuit voltage (Voc) deficit. Herein, we show that by adding an environment-friendly 2-methoxyethanol solvent and adjusting the solution processing conditions without inserting any insulating layer between the Mo substrate and CZTSSe absorber, the multilayer crystals can be removed via a hybrid layered deposition (HLD) approach. In addition, we found that the introduction of Ti4+ in CZTSSe can substantially improve the film morphology, increase the grain size and suppress CuSn defects. Consequently, solar cells based on Ti4+ doped CZTSSe film manifest a conspicuous enhancement in the Voc from 0.455 to 0.505 V with the lowest Voc deficit of 0.278 V, JSC from 36.12 to 39.43 mA/cm−2 along with a remarkable increment in the power conversion efficiency (PCE) from 9.48 to 12.07 %. These results unveil the encouraging prospects of judiciously developed Ti-doped CZTSSe thin-films to alleviate the Voc deficit and boost the performance of kesterite solar cells.

Enhancement of the electrochemical performance of a cathodically coloured organic electrochromic material through the formation of hydrogen bonded supramolecular polymer assembly

Herein, we have developed an H-bonded network polymer architecture with improved crystallinity and photophysical properties through a supramolecular interaction between carboxylic acid-containing perylenebisimide (PBI) cross-linker and poly(4-vinyl pyridine) (P4VP) polymer chains. The H-bonded supramolecular polymers (SMPs) are thoroughly characterized using 1 H NMR, FTIR, XRD, and AFM studies. The XRD reveals higher molecular packing, long-range ordering, and better crystallinity after supramolecular assembly formation, while AFM confirms the fibril and sphere-like nanostructures in the SMP networks with decreased diameters. The long-range ordering and nanoaggregate structures in SMP benefit the network structure for better diffusion of counter ions during the redox reaction of the PBI moieties. The electrochromic (EC) measurements of the films divulge the similar reversible EC colour change of the PBI and SMP films from pristine red to deep violet along with vis-to-NIR electrochromism between the −2 V to +1 V potential sweeping along with the significant improvement of the EC parameters in SMP films compared to pristine PBI film. The colouring time (red to deep violet) is improved by 63% (5.6 s–2.2 s), while the bleaching time (deep violet to red) is speeded up by 51% (8.4 s–4.1 s) along with the increment in colouration efficiency by 50% (52.3 cm 2 /C to 78.1 cm 2 /C). Therefore, this report is very advantageous to deliver a simple and viable strategy for the enhancement of the EC parameters of organic electrochromes through the generation of ordered H-bonded polymer network formation. • Generation of H-bonded supramolecular polymer assembly (SPA) with perylene bisimide (PBI). • PBI used as cross-linker for H-bonded SPA with poly(4-vinyl pyridine). • SPA shows fast switching and improved colouration efficiency than pristine PBI. • Durable vis-to-NIR electrochromism in PBI based SPA.

SVPWAM modulation strategy for back-to-back converters to reduce harmonic and common mode voltage

ABSTRACT This paper presents a new switching strategy by combining space vector modulation (SVM) and pulse amplitude modulation (PAM) techniques. The proposed method can eliminate harmonics and reduce power loss, leading to efficiency increment. Moreover, as one of the significant challenges in any modulation technique, the common-mode voltage is investigated. Accordingly, applying the proposed method in a conventional back-to-back two-level converter results in a substantial reduction of the common-mode voltage as well as the harmonic content of the systems’ input current fed by the power grid. Also, easy implementation regardless of the converter’s rating is the other advantage of using this method. Furthermore, applying this strategy does not add to the converter’s volume, weight, and cost. The appropriate selection of the active vectors, the arrangement of the switching sequences for the inverter and rectifier, as well as the modulation index of the converter are key factors in this technique. The performance of the proposed strategy is investigated through both simulations and experimentations on a back-to-back two-level converter prototype. The experimental results show that the proposed method reduces the common-mode voltage by more than 50%, reaching 87.2% efficiency, making the proposed method suitable for industrial applications.

The roadmap towards the efficiency limit for supercritical carbon dioxide coal fired power plant

The Chinese Government has issued a series of documents to explain China’s control over the carbon dioxide (CO2) emission. One of the major tasks is to develop higher efficiency coal fired power plant, compared with current running power plant. In this paper, we aim to explore the roadmap to reach the efficiency limit for coal fired power plant using supercritical carbon dioxide cycle (sCO2 cycle). Referenced to Carnot cycle, the proposed roadmap is to increase the cycle efficiency by elevating average heat absorption temperature (Tave,h) and lowering average heat release temperature (Tave,l). In contrast to recompression cycle (RC), tri-compression cycle (TC) is introduced. Due to the increased Tave,h, TC achieves the second largest contribution for efficiency increment, followed by the reheating technique. Then, TC, double reheating (DRH) and intercooling (IC) are integrated as TC + DRH + IC in the power plant. To completely absorb flue gas energy over entire temperature range of (1500 ∼ 120) °C. A top cycle and a bottom cycle are connected for cascade utilization of flue gas energy. Overlap energy utilization is further utilized to fill the efficiency gap between top and bottom cycles. The proposed cycle also integrates the module boiler design to suppress the pressure drop penalty, and the flue gas recirculation to keep the heater surface temperature in an accepted level. A numerical model is developed for the comprehensive sCO2 cycle. At the main vapor parameters of 35 MPa/630 °C, the sCO2 coal fired power plant reaches the net power generation efficiency of 51.03%, which is higher than 48.12% for a supercritical water-steam power plant at the same capacity. Such efficiency improvement saves 175.2 kilotons of coal and reduces 396.4 kilotons of CO2 emission for 1000 MW capacity in a fascial year. Our work provides the guideline for the design and operation of large scale sCO2 coal fired power plant.

Energy and Exergy Analysis for Single Slope Passive Solar Still with Different Water Depth Located in Baghdad Center

In the present experimental work, the energy and exergy for single slope passive solar still with different basin water depths are experimentally investigated under the Baghdad climate condition. The analysis is performed using the governing equations formulated according to the first and second laws of thermodynamics. Compared to solar still with 1 cm water depth, the obtained results indicated that raising the water depth to 2 and 3 cm caused an appreciable drop in water basin temperature, and high levels of water basin reduction were about 4% and 9%, respectively, from 8:00 a.m. to 14:00 p.m., which significantly affects heat and mass transfer and ultimately hinders further water productivity. The maximum evaporation and convection heat transfer coefficients are found (32 W/m2·k) and (2.62 W/m2·k), respectively, while the maximum productivity of solar still is found to be 1468.84 mL/m2 with 1 cm water depth. Conversely, stills with 2 and 3 cm water depth, exhibit an increment of the daily exergy efficiency after 14:00 p.m., this increment was the most for the still with 3 cm water depth. Therefore, we have concluded that the still with 1 cm of water depth attained the highest water productivity, while the still with 3 cm of water depth attained the best exergy efficiency with no additional costs.