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Growing demand for electricity due to economic development contributes to increased greenhouse gas production, especially CO 2. However, emissions can be limited by enhancing the efficiency of primary energy conversion, such as integrating geothermal energy into coal-fired power plants. Therefore, this paper proposes replacing conventional feed-water heaters with geothermal preheaters to create a hybridized system. This study was based on a numerical model validated at a selected Polish power unit. The model was subsequently calibrated for off-design conditions to facilitate partial load analysis. The obtained characteristics outperformed those of the non-hybrid unit, generating over 18 MW of electric power output. Such an improvement could potentially boost the unit's net efficiency by more than 2.6 %. This enhancement is significant as power units typically operate under part load for approximately 90 % of the time, hence the need to evaluate the performance characteristics of hybridized units in those states. Furthermore, the research outlines the potential decrease in the plant's CO 2 emission factor, with reductions reaching up to 6.5 % under off-design conditions. Based on a gap analysis of the existing literature, this paper's comprehensive partial load evaluation serves as a new addition to research on hybridized systems. • An in-depth analysis of feed-water heaters operation is performed. • Turbine performance calculations for both design and off-design states is validated. • The comprehensive study of hybridized systems integrates three major factors. • Hybrid geothermal-fossil power cycle is vital for specific CO 2 emissions reduction. [ABSTRACT FROM AUTHOR]

Combined cycle gas turbine power plants (CCGTs) are a combined cycle consisting of a gas turbine and a steam turbine to generate electricity. Sometimes CCGTs incorporate cogeneration to produce both heat and power. After the gas fuel combustion in the gas turbine combustion chamber, the flue gases are passed through the Heat Recovery Steam Generator (HRSG) to extract heat and generate additional electrical power using the steam turbine. The CCGT technology is recognized for its highest efficiency of 58% in electricity production among the power production technology. A highly efficient CCGT power plant with 60% efficiency produces even 2.5 times less CO 2 than a modern coal power plant with an efficiency of 45% because of the use of gas fuel and electrical efficiency. The CO 2 emission can be reduced further when the post-combustion CO 2 capture methods are applied. To perform CO 2 capture and to reduce the CO 2 emission from power plants, the CO 2 mass fraction in flue gas is the crucial parameter for the operation of the Post-combustion Carbon Capture and Storage (PCCS) technology. The PCCS technology uses solvents, which is the aqueous solution of amine that reacts with flue gas and absorbs the CO 2 , which is treated and separated later. The paper presents the results of the energy analysis of a post-combustion carbon capture process when integrated with a combined cycle gas power plant. The study considered two different gas fuels such as methane and syngas. Syngas composition was determined from the sewage sludge gasification process and can be treated as zero-emission CO 2 gas fuel. When the flue gas produced from the syngas is used in PCCS at more than 50% of load conditions, the negative CO 2 emission level in large-scale CCGT power plants can be reached. The paper presents the results of mass and energy balance analysis of HRSG of a CCGT integrated with PCCS to perform CO 2 capture. The analysis of HRSG using flue gases from methane and syngas is performed by calculating the enthalpy of flue gas, rate of heat exchange, and temperature distribution of each component of HRSG. The comparison of the result shows slight differences due to the different composition and flow rates of flue gases. The flue gas at the outlet of two HRSG is used in the PCCS at different load conditions. An aqueous solution of 30 wt% Monoethanolamine (MEA) with rich loading of 0.5 mol-CO 2 /mol-MEA and a mixture of 16 wt% 2-amino-2-methyl-1-propanol (AMP) – 14 wt% Piperazine (PZ) with rich loading of 0.62 and 0.86 mol-CO 2 /mol-amine respectively are used in the PCCS. Due to the reboiler duty of amines, the steam consumed by the PCCS for AMP-PZ regeneration is less compared to MEA. Depending upon the flue gas and solvent used in the PCCS, the power consumed by the PCCS from CCGT power plant is measured from 9.6% to 11.6%. For the given operating condition of the CCGT and PCCS at more than 50% load condition, the negative CO 2 emission level can be achieved. • Analysis of the post-combustion carbon capture process with CCGT was performed. • Comparison of PCCS performances using MEA and AMP-PZ mixture solvent was performed. • Achieving negative CO 2 emission level in CCGT using PCCS are presented. • Flue gas from methane and syngas from sewage sludge were used in the PCCS analysis. • CO 2 emission in flue gases from methane and syngas fuel was calculated. [ABSTRACT FROM AUTHOR]

Scientists initiated a pursuit of more resilient and long-lasting energy sources due to the continuous deterioration of the environment and the substantial rise in the expense of conventional energy sources. Solar energy is one of the most cost-effective, environmentally friendly, and easily accessible sustainable energy sources. Photovoltaic/thermal (PV/T) solar modules are gaining popularity due to their ability to utilise more solar radiation to generate electric power and heat gain simultaneously. This study reviews recent advancements in PV/T modules, focusing on the dual conversion of solar radiation into electrical and thermal energy. The review highlights significant improvements, such as the use of nanoparticles, bi-fluid circulation, and innovative cooling techniques. The study examined the main categories of PV/T systems, including air-cooled, water-cooled, bi-fluid-cooled, nano-fluid-cooled, and ternary nanofluid-based units. This paper offers an in-depth analysis of various components within PV/T modules, covering aspects such as concepts, materials, and review techniques. However, challenges remain, including the trade-off between thermal and electrical efficiency and integration into existing infrastructure. Despite these limitations, PV/T systems show great potential for contributing to sustainable energy solutions and achieving global sustainable development goals. Future research directions include integrating an artificially intelligent approach for system optimization and expanding hybrid PV/T technologies. [Display omitted] • A graphical summary of the PV/T types is demonstrated. • Sustainability achievements by the PV/T modules are discussed. • Water, air, nanofluid, and bi-fluid-based coolants are summarised. • Ternary nanofluid-based PV/T is reviewed. [ABSTRACT FROM AUTHOR]

Resonance tubes are often used to connect multi-stage looped thermoacoustic heat engine and linear alternators to form a multi-stage looped thermoacoustic electric generator. In this paper, we experimentally investigate the performance of a multi-stage looped thermoacoustic electric generator with two sets of resonance tubes of different lengths. With the increase of the length of resonance tubes from 1.5 m to 2 m, the system frequency decreases from 70 Hz to 62 Hz. The maximum output acoustic power increases from 6.97 kW to 8.16 kW, and the maximum output electric power increases from 5.09 kW to 6.24 kW. Meanwhile, the maximum thermoacoustic efficiency increases from 23.08 % to 23.94 %, the maximum acoustic-to-electric efficiency increases from 78.03 % to 82.06 % and the maximum thermal-to-electric efficiency increases from 17.79 % to 19.64 %. Numerical simulation is also conducted based on a 3-step coupling method and validates the experimental results. This study demonstrates that adjusting the length of resonance tubes in a multi-stage looped thermoacoustic electric generator is an effective way to tune the frequency as well as to improve the coupling between the multi-stage looped thermoacoustic heat engine and linear alternators. • A 4-stage looped thermoacoustic electric generator is built. • Resonance tubes with lengths of 1.5 m and 2 m are installed in the system. • Numerical simulation is based on a 3-step coupling method. • Frequency decreases with the length of resonance tubes increases. • Output power and efficiency increase with the length of resonance tubes increases. [ABSTRACT FROM AUTHOR]

Portable electric power generator with a power level of several hundred Watts plays an important role in outdoor activities, emergency relief and tactical power supply. As an external-combustion heat engine with outstanding heat source adaptability, free-piston Stirling generator (FPSG) owns attractive advantages of quietness, high thermal efficiency, and high reliability. This paper proposes a novel ultra-high frequency (UHF) FPSG-based portable power supply system driven by a diesel porous media evaporative combustor (PMEC). An experimental setup was designed and built based on the quasi-one-dimension thermoacoustic impedance matching of the FPSG and three-dimension thermal coupling of steady combustion and alternating flow between FPSG and combustor. The fundamental operating characteristics of the system were investigated in terms of combustion powers and electric loads. Preliminary experimental results show that a maximum output electric power of 350 We at a heating temperature of 875 K and a maximum fuel-to-electric efficiency of 11.98 % were obtained. Computational fluid dynamics (CFD) simulations were employed to delve into the intricate combustion and heat transfer processes, unveiling the formation of carbon deposits and confirming the efficacy of cyclone holes in reducing carbon deposition. This pioneering exploration of 130 Hz UHF and evaporative-combustion coupled heat transfer successfully showcases the feasibility of constructing a high-specific-power FPSG-based portable power system. • An innovative portable power generation system was proposed utilizing a free-piston Stirling generator. • Free-piston Stirling generator with an ultra-high operating frequency exceeding 130 Hz was built to demonstrate a high power density of 70 W/kg. • The integrated design of the high-temperature heat exchanger in the free-piston Stirling electric generator ensures reliability under elevated temperatures and pressures. • The novel design featuring inclined swirl air jet orifices and a gradually shrinking spout effectively eliminates severe carbon deposits, enhancing combustion and heat transfer efficiency. [ABSTRACT FROM AUTHOR]

This paper focuses on the determination of the optimal operating scenario of an Externally-Fired Micro-Gas turbine utilizing syngas produced by biomass gasification. Biomass exploitation can contribute to the achievement of the net-zero emissions target in 2050. This can be boosted by the advancement of externally-fired technology. In this study, a dual-objective optimization process, including a validated thermodynamic model, is combined with preliminary cost insights to assist the decision-making process. The resulting performance is compared with the actual data-based performance of a reference natural-gas-fired Micro-Gas Turbine. The performance comparison is performed through an exergetic analysis, identifying the main losses contributors. The optimization results in an externally-fired performance of 77.9 kW el electrical power and 20.3% efficiency, improved by 31.5% compared to the average current externally-fired demonstrated efficiencies. Yet, there is still room for improvement to reach natural-gas-fired Micro-Gas Turbine efficiency. The study highlights an unavoidable efficiency decrease of at least 4.0 percentage points due to the use of syngas itself instead of natural gas, which conversely increases heat recovery potential. However, compared to the state-of-the-art demonstrations, the proposed analysis is a significant step towards efficiency improvement, which can be exploited for future biomass demonstrations, attractive for electricity generation as well. • Performance of an externally-fired microturbine using biomass syngas is optimized. • Design point is determined through an optimization with preliminary cost insights. • Performance is compared with the validated data from a natural gas microturbine. • Electrical efficiency improved by 31.5% compared to average current demonstrations. • Syngas use results in an unavoidable efficiency decrease of 4.0 percentage points. [ABSTRACT FROM AUTHOR]

The development of novel technical solutions for the efficient recovery of waste heat is crucial for making accessible the large amount of thermal energy released by industrial processes, thus supporting the EU energy strategy. To this end, the EU-H2020 project CO2OLHEAT aims at developing and demonstrating a novel sCO 2 power unit of 2 MW capacity, recovering energy from flue gases at 400 °C. The CO2OLHEAT system features a relatively unconventional multi-shaft configuration where the sCO 2 compressor is driven by a dedicated radial expander, while the electrical power is generated via a separated axial turbine. The present study focuses on the design and fluid-dynamic analysis of the CO2OLHEAT compressor. The thermodynamic optimization of the cycle led to an overall pressure ratio slightly above 2.5, delivered with a two-stage centrifugal compressor. As typically found in sCO 2 power systems, the thermodynamic state of the fluid at the machine intake (P = 85 bar; T = 32 °C) is close to the critical point and to the saturation curve; therefore, the first stage of the machine demands a dedicated aero-thermodynamic design, which can account for the effects of non-ideal thermodynamics and of the potential onset of two-phase flows. The paper discusses the conceptual aero-mechanical design of the compressor and then focuses on its performance assessment over the full operating range via Computational Fluid Dynamics. Two alternative CFD models are applied, the first one based on the barotropic fluid representation and the second one featuring a complete thermodynamic model, both of them assuming homogeneous equilibrium in presence of multi-phase flows. The experimental validation and the application of the two models are presented and discussed. They are shown to provide similar outcomes, and indicate that the compressor fulfills the system requirement and guarantees wide rangeability. A thorough comparison between the CFD results highlights the implications of the underlying physical differences between the models, thus allowing to properly evaluate their use for the aerodynamic design and analysis of sCO2 compressors. • A two-stage sCO 2 radial compressor for waste heat recovery system is presented. • Two alternative CFD formulations are presented and experimentally validated. • The compressor performance and operation are assessed with the two CFD models. • The barotropic model is recommended for design, the full HEM for flow analysis. • The roughness highly influences the compressor performance but not the rangeability. [ABSTRACT FROM AUTHOR]

While the US electric power sector transitioning towards a low-carbon system, the escalated adoption of renewable energy has paradoxically increased water consumption. Consequently, it is imperative to engineer a power generation matrix that mitigates CO 2 emissions and minimizes water utilization. The primary endeavor should be to meticulously identify the variables affecting water consumption changes, especially highlighting and addressing the inherent tension between water conservation and carbon reduction. Employing temporal and spatial Logarithmic Mean Divisia Index methodologies, this study meticulously investigated the factors driving water consumption changes across state-level electricity production sectors in the US from 2010 to 2018. The analysis revealed that the generation mix structure was a predominant factor in escalating water consumption, exerting a more substantial influence than total power generation. Moreover, while the water consumption coefficient initially mitigates the impact of other factors, its effectiveness diminishes over time. Utilizing spatial Logarithmic Mean Divisia Index techniques, this paper further delineated state-level disparities, illuminating the heterogeneous nature of water consumption across regions. Projections up to 2050 suggest that water consumption reductions could be realized even amidst a highly intense scenario. The study's robustness and reliability were further augmented by employing an adaptive Logarithmic Mean Divisia Index. • Temporal-spatial LMDI reveals significant shifts in the US power sector water consumption. • Water consumption coefficient, fuel structure, and generation identified as key drivers. • Scenario analysis forecasts significant water savings potential by 2050. • Findings highlight the necessity for integrated water-energy transition policies. • Study proposes targeted strategies for a sustainable energy-water nexus. [ABSTRACT FROM AUTHOR]

Free-piston Stirling generator (FPSG) is a promising distributed power generation system with compact configuration and high efficiency. In a new perspective on thermoacoustics, this paper develops a time-domain acoustic-electrical analogy method to explore the transient and steady-state performance of a highly efficient FPSG. The method captures the main characteristics of the FPSG, simplifying the calculation thus saving time, and its effectiveness has been verified by our experiments. Transient evolutions of key parameters such as volume flow rate, oscillating pressure and voltage, are first given, followed by an investigation of the acoustic field distribution. Subsequently, a performance analysis of the system is carried out. The results indicate that an increase in the damping coefficient leads to a deterioration in performance, particularly for the displacer. Operating parameters have strong influences on system performance: lower ambient temperature, higher heating temperature and larger external electric resistance contribute to higher pressure ratio and electric power, while excellent performance can be achieved at medium mean pressure. A maximum thermal-to-electric efficiency of 45.2% and a highest exergy efficiency of 68.0% are obtained at an electric resistance of 57.5 Ω and a heating temperature of 600 °C, accompanied by an electric power of 1517 W, which implies that the proposed FPSG has great promise in the field of kilowatt-scale distributed power generation. This paper provides a new viewpoint and an effective way for the rapid simulation of free-piston Stirling generator. • A thermoacoustic-based time-domain method is developed for free-piston Stirling generator. • Transient and steady performance of a free-piston Stirling generator is explored. • A highest thermal-to-electric efficiency of 45.2% with electric power of 1517 W is obtained. • The proposed system shows great potential in the field of distributed power generation. [ABSTRACT FROM AUTHOR]

In the context of globalization where new energy vehicles are widely used, this paper proposes a novel mechanical-electro-hydraulic power coupling system for electric vehicles (MEHV). The planetary gear mechanism (PDCM) is integrated with the accumulator, hydraulic pump/motor, battery and motor to realize the mutual conversion of mechanical energy, electric energy and hydraulic energy. Subsequently, a rule-based energy management strategy is established to distribute energy and realize smooth switching in real time. Then, further analysis is carried out on the electro-hydraulic torque distribution. The results illustrate that, the peak torque of the drive motor (DM) can be decreased, and the hydraulic energy can be fully utilized to improve the state of charge (SOC) under appropriate ratio. Simultaneously, to ensure the appropriate electro-hydraulic ratio under complicated conditions, this paper adopts the fuzzy rule-based energy management strategy of multi-parameter input. Ultimately, the actual driving conditions are established using the actual driving data and the strategy. Consequently, the peak torque is significantly lower than pure electric vehicle, the battery energy consumption is reduced by 19.06%. Therefore, the approach proposed in this paper notably improves the running state of the motor, the energy utilization rate, as well as the economy and stability of the vehicle. • A novel mechanical-electro-hydraulic power coupling system is proposed. • A power flow analysis method based on bond graph theory is proposed. • An analysis of electro-hydraulic ratios is presented by a rule-based strategy. • The electro-hydraulic ratio is optimized according to fuzzy control strategy. • Actual results are analyzed by actual data collection and simulation. [ABSTRACT FROM AUTHOR]

Urban agglomeration is identified as the important geographic units of country development while contributing immensely to carbon emission. This paper explored energy-related carbon emission characteristics of the Pearl River Delta (PRD) - the typical urban agglomeration in China, from cities and sectors perspectives. By conducting LMDI model, this paper decomposed carbon emission by sector and by cities to illustrate the key impact factors in the PRD, explored the reasons for the change of driving effects in urban agglomeration in view of regional difference. It concludes that, most cities carbon emission rebound around 2017, while carbon emission sharply decreased. There are differences in key reduction industries in different cities, while production and supply of electric power and transport sector had negative impact on reduction processes in most cities. The significant inhibition effect of energy intensity is mainly attributed to the great decrease of energy intensity in main industries reduction cities, such as Shenzhen, Guangzhou, Dongguan and Foshan. Based on the characteristics of carbon emission and social and economic development of the PRD, this paper puts forward specific suggestions and measures for differentiated emission reduction in urban agglomeration, and provides a new idea for the governance of carbon emission in urban agglomeration. • The carbon emission inventory of typical urban agglomeration was built. • Carbon emission characteristics were diagnosed from cities and sectors perspectives. • Great disparities in contribution of carbon emission variation exists sectors and cities. • Energy intensity and economic growth were key drives of PRD region carbon emission. [ABSTRACT FROM AUTHOR]

A novel auxiliary energy system for desalination plant based on proton exchange membrane fuel cell (PEMFC)-organic Rankine cycle (ORC) combined heat and power is proposed in this paper. A thermodynamic model of the system is established, and a dynamic net present value (NPV) calculation method under the context of time-of-day tariff is designed. The system output power, economic and environmental evaluation indicators under steady-state and dynamic operation are optimized using NSGA-III and TOPSIS. The parameters sensitivity analysis shows increasing the ORC system saturation pressure and the auxiliary equipment efficiency is beneficial to increase output power and reduce indirect CO 2 mass specific emission (MSE). However, excessive pressure and efficiency will lead to a significant decrease in NPV. Under steady-state optimization, the electrical power of the system is increased by 20.1 % compared to the conventional PEMFC system. And when the proposed system operates dynamically, the single-day power generation is 1620 kWh, which is 9.31 % higher than the PEMFC system. The single-day heated seawater production is 110.1 tons and the MSE is 0.105 kg/kWh. The NPV decreases significantly, but the system can pay for itself over its lifetime. Therefore, the proposed system has thermodynamic and economic performance advantages over the conventional PEMFC system. [Display omitted] • A novel PEMFC-ORC CHP auxiliary energy system for desalination plant. • A dynamic NPV calculation method based on time-of-day tariff. • Thermodynamic, economic and environmental performance indicators. • Steady-state and dynamic operating capacity configuration optimization. • Single-day power generation is 1620 kWh and NPV is $ 870 in dynamic operation. [ABSTRACT FROM AUTHOR]

Solar thermal power system and photovoltaic coupled system can supply electric energy based on renewable solar energy. To explore the optimal configuration of hybrid microgrid driven by solar energy and to achieve a stable and sufficient electric power supply for the distributed energy system, this paper configures a solar thermal-photovoltaic hybrid microgrid and compares the performance of several microgrids based on the power load analysis of the building. The working fluid and the microgrid configuration are determined based on the performance evaluation of single and hybrid microgrids. The effect of solar irradiation on economic and environmental performance is analyzed under the meteorological data of Xi'an and Lhasa in China. Furthermore, the configuration optimizations of a hybrid microgrid based on the actual load and basic load of the building are carried out to examine the performance of the system. Results indicate that economic and environmental performances are sensitive to solar irradiation. More than 50 % of the area of solar thermal collector can be saved for Lhasa compared with Xi'an. Solar thermal-photovoltaic hybrid microgrid with battery can decrease carbon emission and avoid dependence on the external power grid. • Cooling, heating, power load of a six-story building is evaluated and converted. • Multi-objective optimization of solar thermal power system microgrid is performed. • Configuration optimization of solar thermal-PV hybrid microgrid is carried out. • Optimal microgrid configuration under different power load types is compared. [ABSTRACT FROM AUTHOR]

Superconducting systems can reduce the generation of Joule heat and improve energy utilization efficiency, which has a broad application prospect. Improving the energy conversion efficiency of the refrigerator in superconducting systems is crucial, which can further improve the energy utilization efficiency of superconducting systems and promote the large-scale application of superconducting systems. In this paper, an electrical analogy model is developed to calculate the energy conversion efficiency of the pulse tube refrigerator with active dual-piston. And a 40 K pulse tube refrigerator with a high cooling capacity using active dual-piston is designed and fabricated, the accuracy of the model is verified by comparisons of cooling capacity, compressor efficiency, and power of active dual-piston at 300W input electrical power of the compressor. A cooling capacity of 7.17 W can be obtained at 40 K with an electrical power of 506 W. The active dual-piston electrical power reduces from 20 W to 0 W as the diameter of active dual-piston decrease from 24 mm to 18 mm. This study contributes to designing and optimizing a high-energy conversion pulse tube refrigerator with an active dual-piston. • The energy conversion efficiencies of the compressor and cold finger are investigated experimentally. • The conversion efficiency is analyzed with the circuit analogy model. • The acoustic-electric conversion efficiency in the active phase shifter is considered. • The electrical power into the active phase shifter is investigated and optimized. [ABSTRACT FROM AUTHOR]

In order to match the basic load of the power grid and the charging demand of electric vehicles, this paper fully considers the high pollution and non-renewability of coal-fired power generation, the clean and renewable nature of wind power, and the characteristics of intermittent and fluctuation. In this paper, a high-confidence wind power scenario is used to establish a multi-objective optimal scheduling model that considers the V2G characteristics of electric vehicles, generator operating costs, abandoned air volume, environmental pollution, and charging costs for electric vehicle users, the optimal multi-objective scheduling model adopts CPLEX solver tool, by setting the simulation comparison of three scenarios: non-electric vehicle charging, electric vehicle charging, and electric vehicle charging and discharging, the calculation results show that the proposed optimal scheduling strategy realizes the collaborative optimization of thermal power units, wind power and electric vehicles. This paper provides a solution for the optimal scheduling of large-scale electric vehicles connected to the grid. • Established a collaborative optimal scheduling model. • The comprehensive optimal solution is obtained by solving with CPLEX. • Realize the efficient use of various energy sources. [ABSTRACT FROM AUTHOR]

This paper quantifies that current net-zero building definitions will remain as necessary but not sufficient conditions in sustainable decarbonization efforts until they recognize exergy destructions as one of the root causes of emission responsibilities. A direct relationship between exergy destructions and nearly-avoidable carbon dioxide emissions has been set as a sufficient condition to upgrade the decarbonization mindset. This relationship is demonstrated in a case study where a solar prosumer building with photovoltaic panels and a ground-source heat pump, known as a net-zero energy building, is responsible for emissions. Based on the second law, emission responsibilities, primarily at the PV panels and the heat pump, were identified. By replacing them with advanced photo-voltaic-heat panels with temperature peaking and heat pump with adsorption cooling machines, carbon dioxide emission responsibility due to avoidable exergy destructions was reduced by 96%. The main attribute is using solar power only for electric power instead of downgrading it downstream to heat or cold by the heat pump, minimizing exergy mismatches between electrical and thermal power. The paper also shows that a net-zero energy building may neither be a net-zero exergy building nor a zero-carbon building due to these exergy destructions. • Second Law redefines Net-zero buildings, showing unrecognized root emissions causes. • Exergy destructions are responsible for these root causes. • Unrecognized root emission causes are at least 60% of known sources. • A case study shows that solar prosumers may be upgraded for nearly nearly-zero carbon building. • Net-zero carbon building is not possible for inevitable and irreversible exergy destructions. [ABSTRACT FROM AUTHOR]

This paper develops heterogeneity-based econometric models that forecast the yearly consumption of electricity. Unlike previous research, this paper departs from classical econometric regression models and explicitly accounts for unobserved heterogeneity and corresponding interactions. More specifically, three modeling approaches are applied: a random parameter linear regression model (RPLRM), a correlated random parameter linear model (C-RPLRM), and a random parameter linear model with heterogeneity in means and variances (RP-HMV). In addition, a grey model is estimated based on historical consumption data. The estimation results clearly demonstrate that the random parameter methodology is statistically superior to the classical multiple linear regression model. Moreover, based on the test results reported in this paper, as well as the forecasting accuracy measures, the RP-HMV model is shown to be statistically outstanding, with a very low forecasting error (MAPE of 0.04%) compared to the other models, including the grey model. Our estimation results show that two variables, namely the average electricity price and contribution of renewable energy to the national and distribution grids, produced statistically significant random parameters with heterogeneous variances and means. Moreover, the results show that factors including the number of households on the distribution grid, average electric power price, and availability of all-season air conditioners with hot and cold inverter characteristics significantly influenced the electricity consumption. These empirical results reveal that random-parameters models with heterogeneity in their means and variances can provide a detailed analysis of the predictor variables shaping the annual electricity consumption, and they highlight the importance of including unobserved heterogeneity and related interactions in econometric models. • The yearly electric power consumption is addressed through heterogeneity models. • Unobserved heterogeneity in means and variances are considered. • A wide range of explanatory variables affects the yearly consumption of electricity. • The random parameter methodology is statistically superior to the classical multiple linear regression model. • The random parameter model with heterogeneity in means and variances is statistically superior to other heterogeneity models. [ABSTRACT FROM AUTHOR]

Maritime vessels have increased in size to facilitate the transportation of more goods and fuels between continents, but these huge ships rely on diesel engines and consume more fossil fuels that negatively affect the environment. A potential strategy is to replace traditional fuels with clean and green choices and upgrade engine performance. This research paper introduces a newly developed hybrid integrated marine engine involving a gas turbine, a solid oxide fuel cell, and two organic Rankine cycles. This potential engine is then analyzed using exergy, exergoeconomic, and exergoenvironmental analyses and assessments. It is found that the engine combination can produce 15.8 MW, which is increased by 50% compared to a traditional marine engine, and the engine performance reaches 38% energetic efficiency and 47% exergetic efficiency. Also, the exergetic efficiency based on the fuel and product principle is 54 %. This engine has a 243 $/h levelized cost rate and a 132 mPt/h environmental rate. Finally, the average overall specific product exergetic cost and specifc product-based environmental impact are obtained to be 60 $/GJ and 20 mPt/MJ, respectively. By comparing five potential fuel blends (namely MF1 with 25% hydrogen and 75% methane, MF2: 25% hydrogen and 75% methanol, MF3: 40% hydrogen and 60 % ethanol, MF4: 40% hydrogen and 60% DME, and MF5: 40% hydrogen, 15% methanol, 15% methane, 15% DME and 15% ethanol), the blend of methane and hydrogen with marine fuel (MF1) is found to be the most economical with the lowest environmental impact while the second option is the ethanol and hydrogen blend (e.g., MF3). • Five alternative fuels are chosen with different concentrations. • Hybrid marine engine produces 15.8 MW electric power with 54 % exergetic efficiency. • Hybrid marine engine has a total levelized cost rate of 243 $/h. • Total component-related environmental rate of hybrid locomotive is 132 mPt/h. • Specific product exegetic cost and environmental impact are 60 $/GJ and 20 mPt/MJ. [ABSTRACT FROM AUTHOR]

This paper introduces a novel design of a speed amplified flux switching linear generator for the power take-off unit of an ocean wave energy converter. The design incorporates several innovative features, including semi-closed stator iron cores, four coil phases shifting, and a fixed pulley wheel mechanism. These enhancements aim to increase the generator's output power and reduce its cogging force. The fixed pulley wheel mechanism effectively doubles the relative speed of the translator with respect to the stators. The scientific originality of this work lies in the development of a comprehensive design methodology for wave energy converters, specifically focused on optimizing the power take-off design under different ocean environments. The proposed approach combines analytical techniques, hydrodynamic boundary element analysis, 3D electromagnetic finite element modeling, and machine learning methods. By synergistically employing these methods, the authors achieve an efficient and effective power take-off design. To facilitate the optimization process, a three-dimensional electromagnetic finite element model of the flux switching linear generator is developed. This model is refined and optimized to maximize the output power while minimizing the cogging force, using a regular sinusoidal wave motion as the excitation input. The experimental results confirm that the proposed flux switching linear generator outperforms conventional permanent magnet linear generators in terms of power output performance. Furthermore, the model is used to simulate and predict the generator's power output under various ocean environments, considering the hydrodynamics of the wave energy converter. In summary, this manuscript presents a significant contribution to the field of flux switching electromagnetic linear generator based wave energy harvesters. The novel generator design and the comprehensive design methodology offer valuable insights and advancements in the development of efficient wave energy converters. Illustration of a wave energy converter with a flux switching linear generator (FSLG) on the ocean surface and harvested electrical power for the wave energy converter of the proposed new optimal FSLG power take-off model (K em = 8 Tm and C p = 15 N m/s) in the irregular waves of the peak spectrum frequency of 1 rad/s and the significant wave height of 1.414 m. [Display omitted] • A novel speed amplified flux switching linear generator. • A semi-closed stator iron core foot configuration • Four phase coils are adopted for enhancing the performance • A synergy of analytical, finite element modelling, and machine learning methods • The wave energy converter design method under different ocean environments [ABSTRACT FROM AUTHOR]

Deep borehole heat exchanger (DBHE) extracts heat from mid-deep geothermal energy through heat transfer process. As DBHE commonly applies coaxial borehole heat exchangers with depth of 2–3 km, the volume reaches more than 30 m3, similar to the small heat tank underground. When the heat pump system turns off, the water in DBHE still extracts heat from the high-temperature ground and stores heat. This kind of heat storage characteristic of DBHE was studied in this paper with simulation analysis. Benefiting from the heat storage characteristic, the average heat extraction rate (Q r) of DBHE under intermittent operation is 8.6%–64.7% higher than Q r under continuous operation, with run-stop ratio decreasing from 24 to 0 to 8–16 per day. Then the influence of operation modes, parameters and thermo-physical properties of DBHE on the heat storage characteristic were studied quantitatively, proving the wide-range regulation ability of Q r. Therefore, the regulation ability of DBHE matches the variation of space heating load very well, and also matches the production rules of clean electric power like photovoltaic and wind power. Hence, the DBHE could further participate in the demand response of electrical power system, and absorb clean electric power. • The heat storage characteristic of deep borehole heat exchangers (DBHEs) was studied. • The heat storage characteristic improves the transient heat extraction rate obviously. • Operation modes and parameters influence the heat storage performance greatly. • The DBHEs have wide-range regulation ability of transient heat extraction rate. [ABSTRACT FROM AUTHOR]

Thermal management of triple-junction solar cell is crucial for enhancing electrical efficiency of a high concentrated photovoltaic (HCPV) system. In this paper, a HCPV system integrated with vapor chamber (VC) cooling and thermoelectric generator (TEG) is proposed to maximize the energy output. The VC as a passive cooling device can effectively extract the excessive heat from the triple-junction cell and the TEG module are used to convert the waste heat into electrical power thereby harvesting more energy. A detailed unsteady-state modeling of the VC based HCPV/TEG system is established in MATLAB. The effects of new VC structure, TEG type and concentration ratio on the dynamic performance of the system are discussed and a comparison with the CPV-TEG system without VC cooling is provided. Results reveal that effective cooling of the new VCs can maintain the sophisticated cell under 1000 suns at below 329 K and the average exergy efficiency of the system is 31.20%. It is observed that the appropriate selection of TEG module can improve the system performance. Using TEG5, the proportion of CPV power in total power for the proposed system reaches 99.02%, which increases by 2.81% compared with that of the reported CPV-TEG system without VC cooling. • A HCPV system integrated with VC cooling and TEG proposed to maximize energy output. • Unsteady-state modeling of VC-HCPV/TEG system is established in MATLAB. • VCs maintain cell below 329 K at 1000 suns and average exergy efficiency is 31.20%. • Appropriate selection of TEG module can improve the system performance. • The system provides a superior performance compared to CPV-TEG without VC cooling. [ABSTRACT FROM AUTHOR]

Solar thermal devices with large installation areas represent technical, economic, and environmental challenges to design, construct, and operate them. Heat pump assisted with a solar thermal installation (STI) guarantee heat load supply at target temperature of a process, minimizing STI occupied area, environment impacts and associated costs. This paper deals with the design of two heat pumps, each one assisted with a STI. For designing solar network (which together the storage tank makes up the STI), lower irradiance levels than winter period are considered, guaranteeing continuous process operation. For designing each heat pump, two refrigerants with Ozone Depletion Potential of zero and Global Warming Potential of 7 (in one of them) are evaluated. This designing methodology is applied to a second-generation production of bioethanol case study. When heat is generated through a heat pump assisted with STI, the solar network absorber area is reduced by 85%, comparing with required area if only a STI produces heating. The same thing happens to generate electric power. Solar fraction value is one, 81,360 tons/year of not burned bagasse avoids 63,142 tons/year of greenhouse gases emissions. Still always guaranteeing the supply of energy to process, the impacts on environment and soil are minimized. [Display omitted] • Significant reduction of large solar thermal installation and storage system areas. • The cost of solar thermal energy is below the cost of fossil fuels. • Operation of the solar collector network under adverse irradiance conditions. • Profitable heat and power production from solar thermal energy plus heat pumps. [ABSTRACT FROM AUTHOR]

The aim of this paper is the investigation of cold energy recovery of liquefied natural gas (LNG) in regasification terminals achievable through direct expansion techniques. After an overview of the state of the art related to the LNG system and the technologies proposed for power recovery, multi-pressure direct expansion solutions with internal heat recovery (multi-pressure DE) are analysed. The purpose is to identify the highest level of recoverable energy and the optimal design parameters, considering technological constraints such as pressure and minimum end-expansion temperature. The multi-pressure DE solutions prove to be innovative power recovery methods because, with a relatively low use of seawater, it is possible to save regasified LNG and generate electrical power, valorising the energy invested in liquefaction. An estimate of recoverable power in operating terminals is carried out. Configurations with cryogenic or non-cryogenic turboexpanders are discussed. Using the proposed solution with non-cryogenic turboexpander and distribution pressure of 3.5 MPa, 56 kJ for each kg of LNG can be produced, which can become more than 150 kJ/kg with cryogenic turboexpanders. For long-distance distribution, cryogenic multi-pressure DE cycles can recover around 100–120 kJ per kg of LNG. The presented techniques can allow recovery of up to and over 30% of the maximum specific work available in LNG regasification. [Display omitted] • The expansion of LNG trade drives the interest in electricity recovery from cold gas. • Efficient power from LNG: Advancements in recovering cold energy for electricity. • Choosing the best path: Evaluating Direct Expansion and ORC for LNG cold recovery. • Examining the benefits of cryogenic Direct Expansion in LNG power recovery. • Investigating the benefits of multi-pressure direct expansion in LNG energy recovery. [ABSTRACT FROM AUTHOR]

With the gradual transformation of global energy, photovoltaic power generation, wind power generation, and other renewable energy have attracted countries around the world. Western China has excellent wind and solar energy resources, which are highly vulnerable to external factors and have severe limitations. Considering the gradual maturity of storage and energy storage technology of abandoned mine reservoirs, the combination of storage and energy storage technology of abandoned coal mines and wind-solar power generation technology can realize the reasonable allocation of electric energy in the time dimension. This paper studies the regulation capability of the mine pumped-hydro energy storage system proposed by scholars and uses the wind-photoelectric field model to predict the output power of wind farms and solar power stations. Taking the Lingxin coal mine as an example, the optimization algorithm is used to optimize the dispatching ability of the entire PHS joint system. The results prove that the system proposed in this paper can significantly improve the instability of the generation power curve (In terms of variance, volatility decreases to 18.76%), and improve the overall system revenue to some extent (economic efficiency increased by 15.47%). This provides certain technical support for the better utilization of new energy in the future. • A energy dispatching system based on the underground reservoir of mine is presented. • The output power of the electric field is predicted based on proposed means. • GA-dog leg algorithm is used to optimize the system scheduling. • Discuss the robustness and rationality of the optimization method. [ABSTRACT FROM AUTHOR]

To reduce large peak torque and improve the vehicle's dynamic performance during frequent stops and starts, a novel mechatronics-electro-hydraulic power coupling system (MEH-PCS) is proposed. It combines a conventional electric motor and a piston pump/motor into a single unit that converts electrical, mechanical, and hydraulic energy. After a theoretical analysis of the system power flow, the paper establishes a rule-based dynamic optimal energy management strategy to control energy distribution and the dynamic switching of working modes in real-time. Moreover, a prototype vehicle model (MEH-PCEV) based on the MEH-PCS is developed by analyzing the working modes of the system. Thereafter, the feasibility and superiority of MEH-PCEV are verified by comparing it with AMESim certified pure electric vehicles. The verification results indicate that the MEH-PCEV's battery consumption rate is reduced by 14.418% and 21.174%, respectively, in the new European driving cycle and the American city cycle. Furthermore, the time for the vehicle to reach the start-up speed threshold is enhanced, and the electric peak torque is substantially reduced. Ultimately, the paper proposes a fuzzy controller with vehicle speed and pressure of the accumulator as variables to optimize the logic threshold control strategy. The electric torque is substantially reduced while the overall efficiency of the motor operating point is enhanced. The consumption rate of electric energy has been improved somewhat. Under the drive strategy's control, the MEH-PCS is well suited for frequent stops and starts conditions. As a development, this research is expected to provide a reference for improving electric torque. • A novel mechatronics-electro-hydraulic power coupling system is proposed. • The power flow is analyzed to get the factors that affect the electrical power. • A method for switching operating modes to reduce the electric peak torque is proposed. • A regular and dynamically optimal energy management strategy is designed. • A fuzzy logic optimization method is designed to reduce the electric peak torque. [ABSTRACT FROM AUTHOR]

Intermittent renewable energy sources have been transformed from supplementary energy to dominant incremental alternative energy sources in the context of carbon neutrality target worldwide. For coastal countries, it is urgent to integrate abundant offshore energy into regional onshore renewable power sources economically and reliably considering the scarcity of land resources and negative environmental impacts. However, limited knowledge on the complex spatiotemporally synergy relationships between energy potential (onshore and offshore) is a barrier in making reasonable policies to promote collaborative development of onshore and offshore energies. This study presents a spatiotemporally explicit modelling framework for assessing the synergy potential characteristics of onshore and offshore renewable energy sources. The framework firstly estimates the technical potential of solar PV and wind energy across the country by using 40 years of hourly meteorological reanalysis data (1980–2020), and then investigates the long-term changes trend, stability, and complementarity of solar-wind energy potential spatiotemporally at both onshore and offshore sub-regions. We find that a considerable amount of solar PV and wind energy sources could be harnessed in China, and onshore potential across the country (178 PWh/yr) is approximate 20 times higher than offshore energy potential (8.9 PWh/yr). Overall, onshore solar-wind energy potentials exhibit statistically insignificant but slightly increasing trend over the past 40 years, while offshore wind potentials observe an opposite change trend for solar PV and wind energy production. Complementarity assessment showed the northeast and offshore parts of China present high complementarity effects for hourly and daily power production of solar-wind systems. Furthermore, inter-regional combination between offshore and onshore northwest regions also exhibits promising synergy effect for renewable energy power output. The results on resources dynamic and complementarity highlight the advantage of interregional resources cooperative configuration and electric power grid interconnections. The analysis performed in this paper could provide a global picture for the integration planning and collaborative development strategies formulation of on-/offshore renewable energy across the country. • Synergy potential of onshore and offshore renewable energy was evaluated. • Trend, stability, and complementarity of solar and wind potential were examined. • Onshore energy potential in China is 20 times higher than offshore potential. • Synergy development strategies of onshore and offshore energy were proposed. [ABSTRACT FROM AUTHOR]

Exploring efficient renewable energy conversion devices is one of the vital subjects to address the current energy crisis. Double-acting free piston Stirling generator is a promising type of Stirling generator with the advantages of high efficiency and wide energy adaptability, so it has a bright future in the energy sector. In this paper, the SAGE software and acoustic-electric coupling model are used in the generator system for exploring the influence of key parameters on performance. The results indicate that the system exhibits higher power output when the unit number is 4 or 5. The piston clearance may induce greater exergy losses in a double-acting configuration, because of the greater pressure difference and the temperature difference on the two sides of the pistons. Reducing dead volume can improve power density and efficiency. Moreover, any parameter inconsistencies between units can affect the output electric powers of all units. Further investigation reveals that this issue can be effectively addressed by adjusting the external resistance and reactance. This work may offer some guidance for the design of double-acting free piston Stirling electric generators. • An acoustic-electric coupling model for the DAFPSG is established. • The system performs better when the unit number is 4 or 5. • The loss induced by the piston clearance may greatly deteriorate the performance. • Performance degradation induced by parameter inconsistency can be partly suppressed. [ABSTRACT FROM AUTHOR]

Reservoir level control in hydroelectric power plants has importance for the stability of the electric power supply over time and can be used for flood control. In this sense, this paper proposes a sequence-to-sequence (Seq2Seq) long short-term memory (LSTM) neural network model with an attention mechanism and wavelet transform for noise reduction to predict reservoir levels for a one-hour horizon in advance. Accurate reservoir level predictions are essential components for effective water management. The proposed model was evaluated on real-world data and compared with different setups of LSTM, besides ensemble learning models such as bagging, boosting, and stacking. Results demonstrate that the proposed approach outperforms other LSTM models with a mean squared error of 0.0020 and a mean absolute error of 0.0347. Moreover, the wavelet transform with a BayesShrink thresholding method and six levels was the most effective for denoising the input signal. The proposed Wavelet-Seq2Seq-LSTM model provides reservoir managers with accurate and timely predictions of water levels, allowing for better decision-making in dam management under emergency conditions. Advanced techniques such as Seq2Seq, attention mechanism, and wavelet transform to make the proposed approach a promising reservoir-level prediction solution. • Prediction of dam level rise improves confidence in hydroelectric power plants. • The wavelet transform makes noise reduction for chaotic time series. • The BayesShrink method proves to be better for signal denoising. • Attention mechanism assigns appropriate weight to each encoder's hidden state output. [ABSTRACT FROM AUTHOR]

This paper investigates the performance of direct and indirect passive cooling systems of phase change material(PCM)/flat heat pipes (FHP) for low-concentrated photovoltaic solar panel (LCPV) via compound parabolic collector (CPC). The study is performed in the case of not including and including the CPC at different concentration ratios and FHP condenser lengths. The system is entirely mathematically modeled and solved using MATLAB software and validated via experimental setup. The study is performed to cool the panel with PCM attached at its back (direct) or transfer the PV's excess heat to the PCM via FHP (indirect). Results show that indirect cooling system outperforms the direct one with and without CPC system for power generation and efficiency. Both cooling systems mitigate the panel operating temperature without the CPC system, compared with the reference panel. However, the direct approach (LCPV-PCM) has a panel's temperature higher than the reference one including CPC. Contrarily, the indirect cooling system (LCPV-PCM/FHP) has operating temperatures lower than the reference panel at C = 2, while at C = 4, LCPV-PCM/FHP has operating temperatures higher than the reference panel. The maximum produced power from LCPV-PCM/FHP at C = 4 and 30 cm condenser length is equivalent to 3.71 times compared with the reference panel. • Direct and indirect cooling systems of LCPV via HP-PCM are studied. • The indirect PCM-heat sink outperformed the performance of the direct one. • Without CPC, the PV/FHP-PCM has a maximum PV temperature reduction of 19.6 °C. • For C = 4, both cooling systems kept panel's temperature higher than conventional PV. • At C = 4 and L con = 30 cm, the electric power is 3.71 times the reference panel. [ABSTRACT FROM AUTHOR]

The high reliability and long lifespan of thermoacoustic generators (TAG) make them ideal for waste heat recovery applications. However, the size and weight of these generators is still a challenge. This paper introduces a traveling-wave thermoacoustic generator that is free from a wavelength long loop. The new generator consists of an acoustic driver (linear motor), thermoacoustic engine and a linear alternator. The linear motor introduces the initial acoustic power into the thermoacoustic engine which amplifies it, then the amplified acoustic power is converted into electricity through the linear alternator. The electric power obtained from the alternator exceeds the initial input ("seed") power consumed by the motor to kick-start the thermoacoustic amplification, thus providing the net power gain. The advantage lies in decoupling the operation from the reliance on the acoustic resonance. A two-stage engine can be built with half a meter length, while a three-stage engine can be less than a meter long including a coiled inertance pipe. The three-stage TAG can generate 120.5 W of electricity, at a thermal to acoustic efficiency of 34.2% and a total efficiency of 20.5%. • Thermoacoustic engine free from resonance length. • Linear motor and linear alternator matching to a thermoacoustic engine. • Cascade traveling wave thermoacoustic engine. • Passive control of phase difference using inertance tube. • Modelling of thermoacoustic engines using DeltaEC. [ABSTRACT FROM AUTHOR]

Combined heat and power (CHP) plants are main generation units in district heating systems that produce both heat and electric power simultaneously. Moreover, CHP plants can participate in electricity markets, selling and buying the extra power when profitable. However, operational decisions have to be made with unknown electricity prices. The distribution of unknown electricity prices is also not known exactly and uncertain in practice. Therefore, the need of tools to schedule CHP units' production under distributional uncertainty is necessary for CHP producers. On top of that, a heating network could serve as a heat storage and an additional source of flexibility for CHP plants. In this paper, a distributionally robust short-term operational model of CHP plants in the day-ahead electricity market is developed. The model accounts for the heating network and considers temperature dynamics in the pipes. The problem is formulated in a data-driven manner, where the production decisions explicitly depend on the historical data for the uncertain day-ahead electricity prices. A case study is performed, and the resulting profit of the CHP producer is analyzed. The proposed operational strategy shows high reliability in the out-of-sample performance and a profit gain of the CHP producer, who is aware of the temperature dynamics in the heating network. • Distributionally robust operational strategy of CHP producer is proposed. • Proposed method models temperature dynamics in the heating pipes. • CHP producer explicitly controls risk and conservativeness of market profits. • Heat network flexibility improves producer's economic performance. [ABSTRACT FROM AUTHOR]

Real-time temperature measurement during microwave (MW) heating is a significant challenge as metallic thermocouples tend to interact with MW. This paper aims to unravel the mysteries behind metallic thermocouple application during MW heating and present a method to detect a reliable temperature reading during MW processing. Experiments were carried out in a 1.25 kW lab-scale MW system facilitated with a quartz reactor, cavity, and metallic thermocouples placed from the top and the bottom of the MW cavity. The validation of numerical simulation results with an experiment showed the effect of placing the metallic thermocouple on the temperature and electric field distribution. The most striking result was the interaction of the thermocouple with the MW electric field in the top configuration that created localized heating, inaccurate temperature readings (error ± 120 °C), low MW energy absorbance (peak value 91 W), and MW leakage (>10 mW/cm2). Interestingly, a very reliable temperature reading (error ± 20 °C) with high MW power absorption (peak value 273 W) was observed when the metallic thermocouple was placed from the bottom of the cavity. In summary, minimal exposure of metallic thermocouples to MW irradiation would effectively measure accurate temperature. • Real-time temperature measurement under microwave (MW) is challenging task. • Thermocouple exposed to MW shows high discrepancy in temperature reading. • MW electric field and power absorption gets disturbed when thermocouple exposed. • Simulation revealed deposition of electric field on the exposed thermocouple. • Reliable temperature readings when thermocouples are not exposed to MW. [ABSTRACT FROM AUTHOR]

Thermoacoustic electric generator is a novel heat-to-power conversion technology with potential high efficiency and reliability, showing great potential in distributed power generation. In this paper, we conduct time-domain acoustic-electrical analogy investigations on a high-power 4-stage looped traveling-wave thermoacoustic electric generator to shed lights on the system performance. The components of a thermoacoustic system are simplified as an acoustic–electrical analogy model, thus saving computational time. Additionally, the nonlinear effects in the regenerator, heat exchanger and resonance tube are considered in establishing the time-domain equations. Method validation shows a reasonable agreement between experimental and simulated results. Transient evolutions of the oscillating pressure and volume flow rate are firstly given. Investigation is then conducted on onset temperature using different working gases of helium, argon, nitrogen, and neon. The results indicate that when the external resistance reaches 70 Ω, the minimum onset temperature difference of 112 K can be achieved with argon as the working gas. For steady-state characteristics, the influences of electric resistance and heating temperature are explored. It is found that higher heating temperature contributes to larger electric power. A large electric resistance results in a large electric resistance at high heating temperature, while the highest efficiency is achieved with a medium electric resistance. Furthermore, higher heating temperature can lead to more irreversible losses. With helium employed, a maximum electric power of 13.3 kW with thermal-to-electric efficiency of 27.4% is achieved with an electric resistance of 150 Ω and a heating temperature of 950 K, and a highest thermal-to-electric efficiency of 33.5% with electric power of 1.38 kW is obtained when the electric resistance and heating temperature are 90 Ω and 750 K, respectively. This study shows that the proposed method provides a new perspective and an effective method for understanding thermoacoustic electric generator. • A novel time-saving time-domain acoustic–electrical analogy method is proposed. • Investigation is conducted on a high-power traveling-wave thermoacoustic electric generator. • A minimum onset temperature of 112 K is achieved with hydrogen as the working gas. • A maximum electric power of 13.3 kW and a highest thermal-to-electric efficiency of 33.5% are obtained. [ABSTRACT FROM AUTHOR]

Sudan is facing an energy crisis caused by a large deficit in electric power supply and transportation fuels such as gasoline and diesel. Only about 32% of the population have access to electricity. Fuels subsidies have been removed causing a huge prices-hike. Therefore, Sudan is in urgent need to promote its abundant biomass resources to mitigate the energy crisis. In recent years, syngas from biomass gasification has emerged as a potential energy source for power generation and manufacturing synthetic gasoline and diesel via Fischer–Tropsch (FT) synthesis. The paper reports (1) the availability of Sudan's livestock manure for syngas production and (2) the optimization of syngas production for the applications of power generation and FT synthesis. The study covers eight (8) livestock manure of Sudan origin, viz. Cattle Dairy, Cattle Non-Diary, Sheep, Goat, Broiler, Layer, Horse, and Camel. Sudan has a large livestock population but poor manure management. Despite poor management, the available manure (10%) amounts to 17 Mt/year with an energy value of 300 EJ/year (7.14 Mtoe/year). The process optimization is accomplished using the optimization section of the Model Analysis Tools of the Aspen Plus simulator. The cold gas efficiency and H 2 /CO ≥ 2.0 molar ratio are taken as the optimization objective function and constraint, respectively. The operating conditions under which the objective function and the constraint are satisfied are steam to biomass ratio (0 < S B < 5), equivalent ratio (0 ≤ E R < 1. 0), and gasification temperature (500 ° C ≤ T g ≤ 1300 ° C). The optimum set of operating conditions are ER = 0, SB = 0.46-1.0, T g = 750 ° C -1000 ° C. The syngas quality of all livestock manure except Camel are: H 2 mole fraction = 0.47-0.56, LHV = 10.0-15 MJ/kg, and H 2 /CO ≥ 2.0. The syngas produced amounts to 22.42 Mt/year with an energy value of 270 EJ/year (6.44 Mtoe/year). This energy could level the deficit in electric power and transportation fuel demands. • The available manure is about 17.0 Mton/year, with an energy potential of 7.1 Mtoe. • Rigorous optimization procedure is developed and executed using Aspen Plus. • The operating conditions (ER, SB, T) are optimized to give maximum cold gas efficiency. • The potential syngas production is 6.73 Mtoe/year with H2/CO>2. [ABSTRACT FROM AUTHOR]

Current energy intensification measures of dividing wall columns are mainly based on vapor recompression and organic Rankine cycle technologies. Vapor recompression can achieve self-heat recovery of the dividing wall column to use a large part of the waste heat. And the organic Rankine cycle recovers the surplus low-temperature waste heat. However, the efficiency of such low-temperature waste heat recovery by organic Rankine cycle is always low. Additionally, the current design of such energy systems is based on conventional fossil fuels, which are not conducive to long-term development. This paper proposes using solar energy to improve the efficiency of low-temperature waste heat recovery. Based on this concept, a novel waste heat recovery combined solar organic Rankine cycle is established, which is integrated into a vapor recompression assisted dividing wall column system to simultaneously recover waste heat and produce electric power. In addition, the organic Rankine cycle and solar organic Rankine cycle assisted systems were compared. Furthermore, a robust solar-energy design and optimization procedure was used to optimize the three proposed schemes by considering the actual solar fluctuations in Islamabad. Performance analysis and techno-economic evaluation were executed under nominal and actual conditions. The results show that solar radiation can increase the waste heat recovery efficiency and reduce the actual total annual cost. • A concept of using solar energy to enhance waste heat recovery is proposed. • A waste heat recovery combined solar organic Rankine cycle system is established. • Solar energy can improve efficiency of waste heat recovery but less energy recovery. • Using solar energy can save the total annual cost of distillation system. [ABSTRACT FROM AUTHOR]

Looped travelling-wave thermoacoustic electric generator (LTTAEG) can transform thermal energy to electric power using thermoacoustic effect. Based on our previous effort on multi-stage LTTAEG with side-branched and dual-opposed linear alternators (LAs) as acoustic-to-electric transducers, for a higher output electric power and thermal-to-electric efficiency, a 4-stage LTTAEG is studied numerically and experimentally in this paper. In the simulation, the performance of 4-stage looped thermoacoustic heat engine is investigated based on linear thermoacoustic theory while the performance of dual-opposed LA is studied based on a novel network model. A new coupling algorithm between the 4-stage looped TAHE and dual-opposed LA is also proposed. In experiment, with 6 MPa pressurized helium as working gas, 650 °C and 25 °C heating and cooling temperatures. A highest electric power of 6.1 kW with thermal-to-electric efficiency of 15.86% and a highest thermal-to-electric efficiency of 19.64% with electric power of 4.37 kW is obtained when the electric capacitance connected to the LA is 17 μF and the electric resistance is 40 Ω and 75 Ω, respectively. Due to the high oscillating pressure in the system, some nonlinear phenomena have caused the simulation results deviated from the experimental results, especially in acoustic power and electric power, which should be investigated and considered in the future study. • A 4-stage looped thermoacoustic electric generator is studied. • Dual-opposed linear alternator is studied based on a novel network model. • New coupling way of thermoacoustic heat engine and linear alternator is proposed. • Electric power of 6.1 kW and thermal-to-electric efficiency of 19.64% is obtained. [ABSTRACT FROM AUTHOR]

The mitigation of peak-valley difference and transient power fluctuation are both of great significance to the economy and stability of the power grid. This paper proposes a novel vehicle-to-grid behavior management method that can provide peak-shaving and fast power balancing service to the grid simultaneously. Firstly, a multi-time scale vehicle-to-grid behavior management framework is designed to enable large-scale optimization and real-time control at the same time in vehicle-to-grid scheduling. Then, the grid peak-shaving requirement is modeled as an optimization problem in a centralized V2G state coordinator, where the charging behavior of all grid-connected electric vehicles can be synergistically scheduled. The optimization variable is designed as a group of vehicle-to-grid state control signals that can respond to grid peak-shaving requirements. Further, a V2G power controller is designed to manage the vehicle charging power in real time based on the sampled grid frequency state and discrete state control signals. In the developed scheduling method, the charging power of grid-connected electric vehicles is scheduled by the cooperation between the V2G state coordinator and the power controller. The effectiveness of the proposed methodologies is verified on a microgrid system, and results indicate that the V2G scheduling can achieve multi-time scale grid power balancing. This work can bring dual benefits, enabling system operators to use cheap solutions to manage energy networks and allowing vehicle owners to gain profits from providing V2G services to the grid. • V2G behavior management method for multi-time scale grid power balancing. • Grid peak shaving and power balancing can be simultaneously satisfied. • A centralized V2G state coordinator and a real-time power controller are designed. • The method is verified on a microgrid with real power generation and consumption data. • It is proved that the economy and supply quality of microgrids can be improved. [ABSTRACT FROM AUTHOR]