Maximum Obtainable Efficiency Research Articles

Thermodynamic Analysis and Performance Improvement in Biomass Power Plant: A Comprehensive Review

Biomass power plants play a crucial role in the sustainable energy sector by converting organic materials such as agricultural residues, forest biomass, and dedicated energy crops into electricity and heat. Biomass power plants represent a viable and renewable energy solution that can contribute to transitioning to a low-carbon economy. Their ability to convert organic materials into electricity and heat, coupled with proper management of feedstocks and emissions, can provide a sustainable alternative to fossil fuel-based power generation. Biomass has appeared as one of the most encouraging renewable energy sources for the replacement of fossil fuels. An extensive study about the prospective of biomass to produce renewable energy in the world has been exhibited in this article. The biomass-driven combined heat and power plant demonstrates 67% and 12% efficiency improvement compared to the stand-alone biomass power plant. BFP-CCS performs best at the H<sub>2</sub>O/Mn<sub>2</sub>O<sub>3</sub> mass ratio of 1.6, the H<sub>2</sub>O/O<sub>2</sub> molar ratio of 2.8, the O<sub>2</sub>/biomass mass ratio of 0.22, and the fuel utilization factor of 0.65. The exergo-economic and exergo-environmental factors obtained are 51.5% and 0.0288% respectively at the favorable operating conditions. The round-trip efficiency of the process using R1233zd was 8.77%, which was slightly lower than that of the process using R245fa (8.84%). The net power output of the final CLC integrated configuration and conventional power plants are 492.19 kW and 273.12 kW respectively. A lot of energy can be recovered without low-temperature corrosion problems, and 7% of the total input energy can be saved. The maximum obtainable exergy efficiency was 42.03%, which was related to MSW (Municipal Solid Waste). The primary aim of this review is to furnish a thorough understanding of the thermodynamic complexities and potential improvements within biomass power plants. Through a critical analysis of current research and emerging technologies, this review aims to establish the groundwork for more effective and sustainable energy production from biomass, playing a crucial role in shaping a cleaner and more environmentally friendly future.

An innovative biomass-fueled gas turbine-ORC system equipped with electrochemically mediated amine regeneration (EMAR) for CO2 capture

CO2 capture technologies can contribute to reducing pollutant emissions and achieving a ‎cleaner environment. ‎Despite the trend toward reducing fossil fuel use, many of the suggested alternatives emit substantial amounts of CO2, including biomass gasifiers. This study presents a novel hybrid power generation system consisting of a biomass gasifier, a gas turbine, an ORC cycle, an electrochemically mediated amine regeneration (EMAR) technology to capture CO2 emissions, and, for the final storage, a CO2 compressor. Clean production is the primary goal of this study, in which a large amount of energy is produced with a near zero CO2 emission, using EMAR CO2 capture technology. An energy-based model is presented and validated carefully. Two scenarios are proposed to assess the system feasibility encompassing parametric and optimization studies. During the parametric study, the influence of the three subsystems' (gas turbine, biomass gasifier, EMAR) parameters is investigated on three energy efficiencies, defined to evaluate the proposed system performance. Lastly, the hybrid system is optimized via Genetic algorithm considering each efficiency as the objective. Results illustrate that the maximum obtainable efficiency of the system without utilizing EMAR can reach up to 33.65%. Whereas utilizing EMAR and CO2 compressing lowers the efficiency by 6–8% (by point).

Energy, exergy, exergoeconomic, and environmental analyses and multi-objective optimization of a biomass-to-energy integrated thermal power plant

A novel biomass-driven heat and power cogeneration system comprising biomass gasification, a gas turbine, a Stirling engine, and a supercritical carbon dioxide cycle integrated with a domestic water heater was proposed in this work. Different biomass feedstocks (paper, wood, paddy husk, and municipal solid waste) were used in the gasifier as the input fuel. The devised system was analyzed from energy, exergy, exergoeconomic, and environmental viewpoints. Moreover, the effect of integrating the Stirling engine with the stand-alone CHP system is studied. Moreover, a detailed parametric analysis was performed to assess the effect of varying operating parameters on system efficiency. Finally, multi-objective optimization using genetic algorithm in MATLAB software was performed to obtain the optimum operating points. According to the results, using municipal solid waste as the input biomass resulted in the highest exergy efficiency by 41.36% and the lowest CO2 emission by 0.9021t/MWh. Also, the system with the Stirling engine had a higher exergy efficiency and lower CO2 emission than the system without the Stirling engine. According to the optimization results, the maximum obtainable exergy efficiency was 42.03%, which was related to MSW. Also, the minimum achievable cp,tot was 10.94$/GJ, attributable to the respective paddy husk.

Influence of fuel bio-alcohol content on the performance of a turbo-charged, PFI, spark-ignition engine

In this work, the behavior of an engine running with binary and ternary mixtures of n-butanol, ethanol and gasoline has been investigated.Analyses have been performed at different engine speed both at low load and at high load. For each blend, the air to fuel ratio has been kept stoichiometric, while the spark time has been tuned in order to maximize the engine brake torque and hence the engine fuel conversion efficiency. The performance, the combustion characteristics and the pollutant emissions of the engine fueled by biofuel mixtures have been compared to those characterizing the engine running with neat gasoline.In an attempt to provide a guideline for the development of engines running with every mix of gasoline and alcohol, measurements are presented as a function of the oxygen content of the fuel. When the fuel oxygen content increases, results show that the optimal spark time must be retarded at part load while must be advanced at high load. At this operation, the maximum obtainable efficiency increases, the CO2 specific emissions decrease almost linearly together with NOx and HC specific emissions, the engine torque remains practically the same, while the brake specific fuel consumption increases.

Ultracold Rydberg atoms for efficient storage of terahertz frequency signals using electromagnetically induced transparency

Quantum communication with terahertz (THz) frequency signals has many advantages like reduced attenuation and scintillation effects in certain atmospheric conditions along with very high level of data security. In this work, we propose a scheme to realize Quantum Memory (QM) for efficient storage of terahertz (THz) frequency signals using Electromagnetically Induced Transparency (EIT) in an ultracold atomic medium of 87Rb Rydberg atoms prepared in a Two Dimensional Magneto Optical Trap (2D-MOT). The uniqueness of our scheme lies in the choice of the energy levels involved in the EIT process, all three of which have been chosen to be the Rydberg levels (enabling signal beam to be in THz) in a lambda type arrangement. This first of its kind proposal reveals that atomic media are a potential candidate for devising QMs which can store THz frequency signals. We have estimated that the Optical Depth (OD) in our scheme can reach a very high value of 690, very high maximum obtainable storage efficiency (η) of ∼99%, the group velocity (vg) can be as low as 5.07 × 103 m/s, and the Delay Bandwidth Product (DBP) can be as high as 9.5. All of these estimates emphasize the feasibility of our scheme as a QM device for efficient storage of THz pulses.

Design Approach for Efficient Wireless Power Transfer Systems During Lateral Misalignment

This paper methodizes efficiency improvement during lateral misalignment for the wireless power transfer (WPT) system using two coupled semielliptic defected ground structure (DGS) resonators. We design the WPT system using a scaled value of the available mutual coupling between the resonators at perfect alignment. This scaled mutual coupling value enforces over-coupling regime, and the WPT efficiency is lower than the peak one. Then, during lateral misalignment, WPT efficiency improves until it peaks at critical coupling. Next, with further misalignment, the efficiency drops as the system enters loose coupling regime. The proposed method consists of two steps. First, we derive an analytical approach to determine the scaled mutual coupling value for efficiency design during lateral misalignment, and second, we improve the maximum obtainable efficiency by careful designing of the DGS structures’ profile. We verify the proposed method by implementing the WPT system at 300 MHz, which shows a peak efficiency of 80% for a size $D_{o} \times D_{o} = 40 \times 40$ mm2 with a transfer distance $d = D_{o}$ . During misalignment, the efficiency is higher than 50% for a lateral shift up to ±0.75 $D_{o}$ .

Proposition of an Environment Friendly Triple Junction Solar Cell Based on Earth Abundant CBTSSe/CZTS/ACZTSe Materials

We propose a triple junction CBTSSe/CZTS/ACZTSe solar cell using earth abundant and non‐toxic CBTSSe, CZTS, and ACZTSe as the primary absorbing layers for top, middle, and bottom cells, respectively. Using rigorous optoelectronic simulation, we analyze the performance of the proposed cell and vary absorber thicknesses in order to maximize its efficiency. The maximum obtainable efficiency is calculated to be 36.04% with 2.73 V open circuit voltage, 17.88 mA cm−2 short circuit current density, and 73.7% fill factor including Shockley–Read–Hall, surface and radiative recombination mechanisms. The maximum achievable efficiency can be obtained from an optimized device structure with 250, 300, and 1000 nm thicknesses of CBTSSe, CZTS, and ACZTSe, respectively. The design and analyses presented in this work would help in achieving highly efficient eco‐friendly inorganic solar cells.

Impact of membrane characteristics on the performance and cycling of the Br2–H2 redox flow cell

The Br2/H2 redox flow cell shows promise as a high-power, low-cost energy storage device. In this paper, the effect of various aspects of material selection and processing of proton exchange membranes on the operation of the Br2/H2 redox flow cell is determined. Membrane properties have a significant impact on the performance and efficiency of the system. In particular, there is a tradeoff between conductivity and crossover, where conductivity limits system efficiency at high current density and crossover limits efficiency at low current density. The impact of thickness, pretreatment procedure, swelling state during cell assembly, equivalent weight, membrane reinforcement, and addition of a microporous separator layer on this tradeoff is assessed. NR212 (50 μm) pretreated by soaking in 70 °C water is found to be optimal for the studied operating conditions. For this case, an energy efficiency of greater than 75% is achieved for current density up to 400 mA cm−2, with a maximum obtainable energy efficiency of 88%. A cell with this membrane was cycled continuously for 3164 h. Membrane transport properties, including conductivity and bromine and water crossover, were found to decrease moderately upon cycling but remained higher than those for the as-received membrane.

EFFICIENCY OPTIMIZATION OF AN OPENLOOP CONTROLLED PERMANENT MAGNET SYNCHRONOUS MOTOR DRIVE USING ADAPTIVE NEURAL NETWORKS

When a Permanent Magnet Synchronous Machine (PMSM) is utilized for applications where high dynamic performance is not a requirement, a simple open loop control strategy can be used to control them. PMSMs however are prone to instability when operated open loop in a variable speed drive, particularly at mid-frequencies/speeds. This paper presents an open-loop control strategy based on a direct adaptive neural network controller is developed for efficiency optimization of open-loop controlled PMSM drive. Stability constraints of the drive system which was previously reported are used to maintain both stable and highly efficient operation of the drive system. The adopted neural network can be viewed as a method for nonlinear adaptive system identification, relying on pattern recognition of stability limits and maximum obtainable efficiency. Results from computer simulation show that a stable and highly efficient operation can be maintained for the drive system under study irrespective of load and supply variations. The obtained results are also found in correlation with previously reported experiments and observations.

Multiple regression models for the prediction of the maximum obtainable thermal efficiency of organic Rankine cycles

Much attention is focused on increasing the energy efficiency to decrease fuel costs and CO2 emissions throughout industrial sectors. The ORC (organic Rankine cycle) is a relatively simple but efficient process that can be used for this purpose by converting low and medium temperature waste heat to power. In this study we propose four linear regression models to predict the maximum obtainable thermal efficiency for simple and recuperated ORCs. A previously derived methodology is able to determine the maximum thermal efficiency among many combinations of fluids and processes, given the boundary conditions of the process. Hundreds of optimised cases with varied design parameters are used as observations in four multiple regression analyses. We analyse the model assumptions, prediction abilities and extrapolations, and compare the results with recent studies in the literature. The models are in agreement with the literature, and they present an opportunity for accurate prediction of the potential of an ORC to convert heat sources with temperatures from 80 to 360 °C, without detailed knowledge or need for simulation of the process.

Comparison of the energy performance of pulse generation circuits for PEF

Pulse shaped voltages are required for preservation of food with PEF. Several pulse forms generated by a variety of circuits are compared with respect to required energy. The analysis includes square pulses, trapezoidal pulses, exponential decay pulses and oscillatory and over-damped oscillatory pulses. The base of comparison is the establishment of a certain minimum voltage level during certain minimum time. The comparison concerns the dissipation in a resistive load, which is considered to be representative for a category of loads, including PEF. Furthermore, the ratio between initial capacitor voltage and corresponding threshold voltage is compared as this parameter reflects the required hold voltage of the switch in the circuit. The analysis shows that the efficiency approaches 100% for hard switched circuits and circuits with transmission lines. For highly damped RLC-circuits with capacitor C, inductor L and load resistance R the maximum obtainable efficiency is between 37 and 47% where the capacitor C has to be charged to 1.6–1.8 times the desired threshold voltage. For oscillating damped sinusoids the maximum efficiency is between 47 and 52%, however, the capacitor has to be charged to 1.8–3 times the threshold voltage. Graphs with an example are provided to determine circuit parameters from a certain pulse specification.

On communications performance and processor efficiency

Efficient applications running on large multiprocessor machines require the support of an effective communications fabric. Contemporary multiprocessor networks based on dedicated VLSI switching components have dramatically improved performance over store-and-forward techniques, however communications latency is still very significant compared with computation speed. This limitation places constraints on the design of efficient parallel applications. This paper demonstrates the viability of an approach to enhancing communications performance and thus run-time efficiency of network-bounded parallel applications. A bound is derived on the maximum obtainable efficiency for applications on point-to-point connected architectures. This motivates an optimisation strategy based on controlling network bandwidth requirements, by constraining the dilation of the mapped interprocess communications graph. The effectiveness of the optimisation strategy is demonstrated through simulation of realistic network-bounded application loads.

Influence of roughness and interdiffusion in zone plate structures on the diffraction efficiency described by coupled wave theory

Diffractive transmission x-ray optics, e.g., zone plates and gratings, are well suited for x-ray microscopy and spectroscopy. X-ray optics for use at short wavelengths require high zone aspect ratios which can be obtained by alternately depositing two materials with different x-ray scattering properties on a microwire. The roughness and the diffusion inherent to this process influence the diffraction efficiency of these optics. Using coupled wave theory, it is shown that roughness and interdiffusion increase the structure height required for optimal diffraction efficiency compared to ideally smooth structure profiles. In addition, the maximum obtainable diffraction efficiency decreases with increasing root-mean-square roughness and interdiffusion.

Multicast scheduling algorithms in mobile networks

We consider the problem of multicasting data to mobile users in a cellular mobile network. In the absence of mobility, a single channel can be used to multicast to all mobile users within a cell. However, mobility combined with the effects of fading necessitates a more complex channel allocation policy. In this paper we develop theoretical bounds on the maximum obtainable efficiency and present algorithms that acheive this bound. Our results hold for the case when mobiles travel on a highway, as well as for the more general case where mobiles roam in a two-dimensional region.

Grating microstructures in photoactive polymers by laser interference patterns

The formation of grating microstructures in new photopolymer formulations are investigated by holographic recording. Holographic recording in cast polymer layers occurs in real-time and in-situ, meaning that no wet-chemical or post-thermal/photochemical processing are required. The hydrophilic photopolymers are based on acrylamide monomers, which are dissolved together with photoactive components, such as the sensitizing dye eosin and the new charge transfer agent diphenyl iodonium (DPI) salt with triethanolamine, in polyvinyl alcohol. The addition of DPI significantly increases the exposure sensitivity from about 35 to 12 mJ/cm 2, i.e. by a factor of about three, without affecting the maximum obtainable diffraction efficiency (DE). The influences on the storage mechanism by other additives, such as cross-linking agents and plasticizers are also investigated. The introduction of the cross-linking agent bisacrylamide stabilizes the formed structures against thermal and environmental relaxations. The introduction of plasticizers have a significant effect on the spatial modulation of the refractive index in the recorded grating patterns. Large enough refractive index modulations can be obtained, so as to yield very high DEs of about 90%. The angular-DE and thickness-DE responses closely follow the theoretical predictions, according to the coupled-wave theory. These photopolymer layers have potential in photonics applications, such as holographic optical elements and waveguide structures.

Anaerobic Treatment of Domestic Sewage under Moderate Climatic (Dutch) Conditions Using Upflow Reactors at Increased Superficial Velocities

This paper describes experiments with domestic sewage using a 120 litre expanded granular sludge bed (EGSB) reactor and a 205 litre fluidised bed (FB) reactor. Presettled domestic sewage was used in the experiments, because these reactor systems are inadeguate in removing SS. Compared to conventional UASB reactors, the advantage of EGSB systems is the significantly better contact between sludge and wastewater. A batch recirculation system was used to assess the maximum achievable removal of the different COD fractions under EGSB and UASB conditions. The results obtained with the EGSB reactor reveal a removal efficiency of 90% with respect to the maximum obtainable efficiency of the soluble COD fraction under dry weather conditions. This efficiency can be obtained at hydraulic retention times (HRT) exceeding 3 hours. Even at HRT's ranging from 2 - 1.5 hours, still 84% - 77% of the maximum possible removal efficiency as assessed in batch recirculation experiments can be achieved at temperatures exceeding 13°C. The advantage of EGSB systems is the high volumetric loading rate that can be applied while maintaining a high removal of the dissolved COD fraction. Moreover, little if any accumulation of inert suspended solids occurs in the sludge bed. On the other hand, the poor removal of suspended solids can be considered as a disadvantage of these systems in treating domestic sewage. Conventional FB systems using sand as carrier material were shown to have little prospect for treating settled domestic sewage, because hardly any methanogenic activity will develop in such a system. However, it was also found that a very satisfactory guality granular sludge developed on settled sewage when operating FB systems in a mode similar to EGSB systems. This granular sludge appeared to be of a guality egual or even better than that of granular seed sludge, cultivated in a UASB reactor treating papermill wastewater.

Strategies for optimized application of annular-phased-array systems in clinical hyperthermia

A theoretical framework is presented for optimized heating of deep-seated tumours by phase and amplitude steering. The optimization problem for a specific tumour and perfusion case results in a functional dependency between power-level and maximum obtainable therapeutic efficiency. Different optimization criteria and strategies are outlined, which cause an increase of power or thermal dose in the tumour. Three tumour models (central pelvic tumour, eccentric abdominal tumour with or without necrosis) are analysed in detail. The simulation studies predict that appreciable parts of these tumours (50-100%) can be heated efficiently (42.5-43 degrees C) within the range of available and clinically tolerated power levels (1-5 kW/m), if tumour perfusion is less than 20-25 ml/100 g min. Some improvements are obtained by increasing the number of independent channels (from four to eight) and by the application of time-dependent (complementary) power-deposition patterns.

Optimization of the parameters of an ion beam buncher

To maximize the ion current in a bunch coming out of a beam buncher several parameters have to be optimized. In this paper an analytical method has been developed to optimize these parameters for a sinusoidal buncher and a buncher excited by a combination of the first and second harmonics. Expressions have been given for maximum obtainable bunching efficiency as a function of phase acceptance. The shape of the bunched beam is discussed.

Optimization of Three-Phase Induction Motor Design Part II: The Efficiency and Cost of an Optimal Design

With the continuing increase of the cost of electrical energy, motor manufacturers and consumers became increasingly concerned with the energy conservation available from highly efficient electrical motors. Motor cost and efficiency are interrelated; therefore, the effect of motor cost on the maximum obtainable efficiency is of interest both to the motor manufacturer and to the consumer. The relation between the power factor and the maximum efficiency of a motor is another aspect of energy conservation. The optimal motor design, with respect to the maximum efficiency, and with respect to the minimum motor cost (by means of a mathematical optimization method described in Part I), was used in Part II to investigate the above-mentioned motor relations. Three motor-cost functions were investigated: production cost, capitalized cost, and annual cost. The motor that was used in the study was a 100 hp, three-phase, squirrel-cage induction motor.

Helix and coupled-cavity traveling-wave tubes

After 28 years of considerable research and development, two types of traveling-wave tube (TWT) circuits have captured the major portion of the production business. For broad-band applications, the helix is almost exclusively used, while for high-average-power applications, such as radar transmitters, the coupled cavity circuit has gained the ascendancy. Recent advances have been stimulated and supported by the ever increasing needs of electronic countermeasures (ECM) where average power and bandwidth are of critical importance. For airborne systems where the limitations on weight and size are stringent, periodic magnetic focusing has been utilized along with special gridded electron guns which make possible simple modulation circuits. Although relatively few TWT's have been manufactured in large quantitites, there are many refined prototypes covering the frequency range from L band through Ku band at power levels of from a few hundred watts to several hundred kilowatts. Very impressive life data have now been accumulated for the TWT amplifiers currently operating in all of the communication space satellites. Although this particular application is less than 10 years old, there are hundreds of TWT's continuously transmitting in orbit today. Significant advances have been recently achieved in the maximum obtainable efficiency from a TWT designed for system use. With careful design of the electron optics and the employment of velocity tapering, efficiencies in excess of 50 percent are quite common in a practical transmitter operating in the X-band region. Broad-band dual-mode tubes are now in the development stage which permit efficient operation at two different power levels separated by as much as 7 dB. Such versatility is quite important to modern airborne countermeasure techniques. In the foreseeable future, the total TWT market will likely remain constant at the 80-million dollar level in spite of the continued erosion of the present tube applications caused by solid-state microwave devices. As power levels increase and the higher frequency bands become more popular, TWT's will remain unchallenged in many situations. No dramatic breakthroughs are predicted for this mature technology, but there will be increasing emphasis on life, reliability, and cost.