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Thermal energy storage technologies have been widely used to mitigate intermittency from renewable energy sources such as solar energy. Phase change material (PCM) is a material that can be used as a heat storage medium and is available in a wide range of operating temperatures. Molten salt is one of the PCMs that has the advantage of a very high operating temperature. The PCM solidification simulation based on HitecXL molten salt using COMSOL Multiphysics software was carried out with variations in heat absorption of 1–5 kW/m2, assuming constant heat absorption. The results showed that the PCM solidification process started from the surface of the Stirling engine heat exchanger pipe. The part of the PCM that is solidified falls due to gravity, causing a phenomenon similar to a droplet. The flow that occurred was natural, driven by the buoyancy force resulting from density changes due to temperature gradients in the solidification process. The time required for the PCM to completely solidify was closely related to the amount of heat absorption; the greater the heat absorption from the pipe, the faster the PCM is fully solidified. [ABSTRACT FROM AUTHOR]

Thermochemical recuperation heat recovery is an advanced waste heat utilization technology that can effectively recover exhaust waste heat from oxy-fuel Stirling engines. The novel combustor of a Stirling engine with thermochemical recuperation heat recovery system is expected to utilize both reformed gas and diesel fuels as sources of combustion. In this research, the effects of various factors, including the H2O addition, fuel distribution ratio (FDR), excess oxygen coefficient, and cyclone structure on the temperature distribution in the combustor, combustion emissions, and external combustion system efficiency of the Stirling engine were experimentally investigated. With the increase of steam-to-carbon ratio (S/C), the temperature difference between the upper and lower heating tubes reduces and the circumferential temperature fluctuation decreases, and the combustion of diesel and reformed gas remains close to complete combustion. At S/C=2, the external combustion efficiency is 80.6%, indicating a 1.6% decrease compared to conventional combustion. With the increase of FDR, the temperature uniformity of the heater tube is improved, and the CO and HC emissions decrease. However, the impact of the FDR on the maximum temperature difference and temperature fluctuation across the heater is insignificant. When the FDR rises from 21% to 38%, the external combustion efficiency increases from 87.4% to 92.3%. The excess oxygen coefficient plays a secondary role in influencing temperature uniformity and temperature difference, and the reformed gas and diesel fuel can be burned efficiently at a low excess oxygen coefficient of 1.04. With an increase in the cyclone angle, the heater tube temperature increases, while the maximum temperature difference at the lower part decreases, and the temperature fluctuation increases. Simultaneously, the CO and HC emissions increase, and the external combustion efficiency experiences a decrease. A cyclone angle of 30° is found to be an appropriate value for achieving optimal mixing between reformed gas and diesel fuel. The research findings present valuable new insights that can be utilized to enhance the performance optimization of Stirling engines. [ABSTRACT FROM AUTHOR]

Creating stable oscillations in the nonlinear dynamic of thermoacoustic stirling engines is an essential challenge for researchers. Hence, investigating this challenge is the main objective of this paper. In this regard, a novel systematic and parametric method using the practical stability theory is presented to investigate the stable oscillations (sufficient condition) of thermoacoustic stirling engines for the first time. In this regard, the goals of the problem, which included stable oscillations of the pistons are determined. In the following, based on the desired objectives of the nonlinear dynamic equations, the engine error is extracted. Based on the practical stability theory, a Lyapunov function is selected according to the dynamics of the problem. Then, a time derivative of the Lyapunov candidate function and its sign is determined later. According to the conditions presented for the practical stable theory (the positive definiteness of the Lyapunov function and the negative definiteness of its derivative), nine parametric conditions for the error dynamics of the thermoacoustic stirling engine are presented. Once these nine conditions are met, sufficient conditions (stable motion) will occur in engine dynamics. The noteworthy point is that the presented method is completely parametric, and this will make it possible to easily evaluate the effect of each parameter of the engine to reach sufficient conditions. Another interesting feature of the presented idea is to determine the accuracy of the design process, which can be determined using the value of the ultimate bound. In other words, the lower the value of the ultimate bound, the better the accuracy of the design. As a result, the design is close enough to the problem's objectives. Hence, in this work, the effect of the important parameters of the engine on the value of the ultimate bound is also evaluated. It is worth mentioning that in order to verify the effectiveness of the presented method, the data extracted from the constructed engine is used to check the sufficient condition and the effect of the parameters on the ultimate bound. The obtained results showed that the presented parametric method can examine the mentioned cases appropriately. In the end, it can be said that the main innovation and finding of this work is to investigate the sufficient condition of the thermoacoustic stirling engines using a parametric method (presenting nine parametric conditions). Through the utilization of this method, researchers can not only assess the sufficient condition but also investigate the impact of engine parameters on its performance before construction. This approach helps in reducing costs and time associated with the study. [ABSTRACT FROM AUTHOR]

The pneumatic supporting system consisting of gas springs and self-charged hydrostatic bearings can suppress vibrations and improve durability of free piston Stirling engines. In this paper, a free piston Stirling generator with pneumatic supporting system on the displacer was developed based on a prototype of plated spring scheme. A series of experiments were carried out to evaluate the impacts of self-charging gas bearing on the performance of gas springs. During the experiments, the linear alternator was applied an external AC power supply and the pressure fluctuations in working chamber were ensured to be consistent so that the pneumatic supporting system was separated from the entire engine. Through blocking the orifices and ducts of gas bearings with plugs, the gas springs were decoupled with the gas bearing. Comparative results show that the internally charged hydrostatic bearing can effectively reduce the mechanical damping of the displacer with a reduction from 117 N/m to 83 N/m after the bearing is switched on. While the hydrostatic bearing has side effects on the gas springs that increase the hysteresis loss from 78.48W to 337.11W and decrease the axial stiffness significantly.

To limit global warming and meet international environmental targets, more environmentally benign technologies must be used in the residential market. Combined Heat and Power (CHP) at the micro-scale (<50 kWe) is seen as one of the best solutions that offers simultaneous generation of both electricity and heat with high overall efficiencies using environmentally friendly fuels (e.g., biofuel, hydrogen, syngas). In this study, four major micro-CHP prime movers (i.e. Micro-gas turbine, Gas engine, Stirling engine, and Fuel cell) have been evaluated in terms of their performance and the currently available technologies and products. The most suitable options for household applications were identified using Political, Economic, Social, Technological, Legal, and Environmental (PESTLE) risk analysis and a Multi-Criteria Decision Analysis (MCDA). Fuel cells display the best environmentally friendly properties despite their price and high start-up time. Gas engines (Reciprocating engines) have the most developed technology with the fastest start-up time and high efficiencies but have vibration and noise issues. Micro-gas turbine micro-CHPs are emerging into the market with relatively cheaper prices, lower maintenance, and good start-up time. Stirling engines are fuel flexible with reasonable prices and available products. Micro-CHP systems, particularly when running on biofuels and hydrogen, provide excellent energy solutions for the future net zero buildings. [ABSTRACT FROM AUTHOR]

In order to improve the performance and service life of the Leningrader seal of the Stirling engine piston rod, interference, preload and friction coefficient were taken as influencing factors, and the curved surface response method was adopted to reduce the contact stress of sealing surface and von Mises stress of the sealing sleeve as the response index, with the optimization goal of reducing wear and extending life. The above three key parameters are analyzed and optimized, the influence of each parameter on the sealing performance and service life is obtained, and the best combination scheme of the three is determined. The results show that the interaction between pretightening force and interference fit has the greatest impact on contact stress. The interaction between interference fit and friction coefficient has the most significant effect on von Mises stress. The optimized parameters can reduce the maximum contact stress and maximum von Mises stress of the sealing sleeve by 26.3% and 20.6%, respectively, under a media pressure of 5-9 MPa. Test bench verification shows that the leakage of the optimized sealing device in 12 h is reduced by 0.44 cc·min-1 (1 cc=1 cm³). The wear rate of the sealing sleeve is 1.08% before optimization and 0.45% after optimization, indicating that the optimized parameters in this paper are effective. [ABSTRACT FROM AUTHOR]

Renewable energy sources account for a significant part of the energy sector, but electricity generation from renewable energy plants is not stable and predictable over time, depending on various factors, such as wind speed or insolation. One method of ensuring stable electricity generation from such plants is to use an additional energy source. In a thermodynamic plant based on the Stirling engine, when the heat from the concentration of solar radiation is not enough, additional heat can be obtained by burning fuel. This paper investigates the temperature control of the Stirling engine boiler by changing the distance to the Fresnel lens, which will allow further calculation of the required power of the additional heat source. The dependence of the temperature of the concentration spot on its area and the distance between the lens and the heating part of the engine at different intensities of solar radiation was determined. The depth of focus of the lens is analysed as the main characteristic for the selection of systems that regulate the distance between the lens and the surface of the Stirling engine boiler. [ABSTRACT FROM AUTHOR]

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The EU's energy targets are to achieve at least 32% renewables in the energy mix by 2030. Part of the solution is strengthening consumer rights by empowering individuals to generate their own electricity. The aim of this study was to identify the most suitable energy system for electricity generation of up to 50 kW in the EU residential sector. Multi-Criteria Decision Analysis was used to compare four systems: proton exchange membrane fuel cell with photovoltaic panels, photovoltaic panels, biomass-powered Stirling engine, and solar-powered Stirling engine. Based on the results, the most beneficial system for household electricity generation is the biomass-fueled Stirling engine system due to its affordability, reliability, and low environmental impact. Governments and businesses can use these findings to improve information for the residential sector and enable the transition to renewable energy. [ABSTRACT FROM AUTHOR]

Low temperature difference Stirling engine is an excellent teaching material for mechanical design because (1) students can experience all of four dynamics (material mechanics, fluid dynamics, thermodynamics, and dynamics of machinery) by designing and constructing it, (2) it is safe even if the design is not appropriate, so it allows students to freely try their own ideas, (3) there are many variations of engine configurations, including types and mechanisms, so there is much room for creativity and ingenuity, and (4) as the structure is simple, it is easy for students to understand if their ideas make sense. On the other hand, it is not easy to construct a working engine because of its low power. In order to make low temperature difference Stirling engines more effective teaching materials, this paper describes the design and fabrication of a low temperature difference Stirling engine with high power per swept volume that can run at higher speed. The results of analyzing the working fluid temperatures in the expansion and compression spaces indicate that the temperature ratio increases with increasing speed even in a low temperature difference Stirling engine. We found that an arrayed resin regenerator can provide high performance, and realized that a Stirling engine with a power piston swept volume of 4.5 cc and using hot water and ice as heat sources can run at a maximum power of 171 mW and a maximum speed of 31.3 Hz. Compared with other low temperature difference Stirling engines, the power per swept volume of test engine is more than 10 times higher and the rotational speed is nearly three times higher than those of the low temperature difference Stirling engines already reported. The results show that low temperature difference Stirling engines with high power per swept volume can be designed and fabricated by using 3D printers, and the value of the low temperature difference Stirling engine as a teaching material has been enhanced.

In this study, the performance of a hybrid power/freshwater generation system is modeled using a coupled artificial neural network (ANN) model with a pelican algorithm (PA). The proposed system is composed of a Stirling engine fixed to a solar dish, a desalination unit, and a thermoelectric cooler. The Stirling engine is used to generate the electricity required to operate the electrical-powered components of the system as well as to preheat the saline water. The thermoelectric cooler is used to supply the saline water with additional heat as well as to cool the condensation surface of the desalination unit. The performance of the proposed system in terms of water yield, generated power, and system efficiency was considered as the model's output; while the solar irradiance and dish diameter were considered as the model's inputs. In addition to the pelican algorithm, a conventional gradient descent optimizer was employed as an internal optimizer of the ANN model. The prediction accuracy of the two models was compared based on different accuracy measures. The ANN-PA outperformed the conventional ANN model in predicting the water yield, generated power, and system efficiency. The computed root mean square errors of the ANN and ANN-PA models were (1.982 L, 104.863 W, and 1.227 %) and (0.019 L, 1.673 W, and 0.047 %) for water yield, generated power, and system efficiency, respectively.

A typical model for a gyrating engine consists of an inertial wheel powered by an energy source that generates an angle-dependent torque. Examples of such engines include a pendulum with an externally applied torque, Stirling engines, and the Brownian gyrating engine. Variations in the torque are averaged out by the inertia of the system to produce limit cycle oscillations. While torque generating mechanisms are also ubiquitous in the biological world, where they typically feed on chemical gradients, inertia is not a property that one naturally associates with such processes. In the present work, seeking ways to dispense of the need for inertial effects, we study an inertia-less concept where the combined effect of coupled torque-producing components averages out variations in the ambient potential and helps overcome dissipative forces to allow sustained operation for vanishingly small inertia. We exemplify this inertia-less concept through analysis of two of the aforementioned engines, the Stirling engine, and the Brownian gyrating engine. An analogous principle may be sought in biomolecular processes as well as in modern-day technological engines, where for the latter, the coupled torque-producing components reduce vibrations that stem from the variability of the generated torque.

The EU’s energy targets are to achieve at least 32% renewables in the energy mix by 2030. Part of the solution is strengthening consumer rights by empowering individuals to generate their own electricity. The aim of this study was to identify the most suitable energy system for electricity generation of up to 50 kW in the EU residential sector. Multi-Criteria Decision Analysis was used to compare four systems: proton exchange membrane fuel cell with photovoltaic panels, photovoltaic panels, biomass-powered Stirling engine, and solar-powered Stirling engine. Based on the results, the most beneficial system for household electricity generation is the biomass-fueled Stirling engine system due to its affordability, reliability, and low environmental impact. Governments and businesses can use these findings to improve information for the residential sector and enable the transition to renewable energy.

Nowadays, energy systems are continuously impacted by external and internal conditions. The worldwide events of recent years have led to the need to consider not only the requirements for moving towards climate neutrality but also the security and independence of energy supply when creating new or transforming existing energy systems. The aim of this study was to answer the question of whether there is a possibility of transforming the energy supply process by promoting increased energy security and independence while not reducing energy demand, as well as creating high economic and environmental indicators. The research focuses on developing alternative scenarios for further decision-making studies by introducing modern energy technologies. Scenarios are analysed using the complex method developed, which includes three main steps: assessing the current situation, identifying available technologies, and assessing alternatives. The results suggest that Stirling's technology can provide 100% energy independence for individual energy consumers. At the same time, thanks to the combination of Stirling technology and solar technologies, there is an opportunity to reduce emissions and energy production costs, but capital investment is increasing. [ABSTRACT FROM AUTHOR]

Researchers' interest in Fuel Cells (FCs), a cutting-edge technology for producing heat and electricity simultaneously, has grown significantly in recent years. FC technology is a non-renewable yet unconventional distributed energy source with a number of benefits for the economic, environmental, and dependable operation of energy systems. In the present study, a highly efficient FC type is integrated with a Stirling engine and vanadium chlorine scheme. The proposed cycles are efficient not only in power generation but also in hydrogen production since it uses waste heat to generate hydrogen. The system is investigated from technical, economic, and environmental aspects through the scrutiny of parameters affecting the system's performance. A cutting-edge method of machine learning-based optimization with a gray wolf algorithm is used to identify the ideal solution point when different optimization goals are selected. The results indicate that the TOPSIS point matches the maximum efficiency and hydrogen production of 81% and 0.008 kg/s, and the ζ equals 0.21. Also, maximum net power output and hydrogen production of 7500 kW and 0.0045 kg/s happens in the TOPSIS point with the levelized cost of the products of 0.14 $/kWh. • A newly proposed system integrated with VCLC and fuel cell/Stirling is introduced. • The Machine learning-based gray wolf optimization is applied to the scheme. • The TOPSIS method is applied for the identification of the best point. • Maximum net power and hydrogen production of 7500 kW and 0.0045 kg/s is reached. [ABSTRACT FROM AUTHOR]

Reliable heat and power supply are among the basic household needs nowadays. It is especially topical in rural or distant locations that may be cut off from the energy grid due to extreme weather or other events. Nonetheless, the sustainability of our power production systems has to be considered to sustain our planet's long-term abilities to provide energy resources and a viable environment. Renewable energy resources must be prioritized in rural and remote areas, simultaneously strengthening distributed production ability and self-sufficiency. In this context, the use of the Stirling engine for heat to power generation in households, on the scale of small communities, and by using only renewable resources is becoming increasingly topical. Therefore, this research aims to identify the current state-of-the-art for Stirling engine applications using biomass as a renewable energy source, in the context of sustainability and energy security. The paper summarizes the current research tendencies at the household level in the use of biomass-based Stirling engines for renewable heat and power generation in decentralized energy systems. The methodology applied is a structured literature review and content analysis. The research results corroborate the progress towards the use of renewable resources and towards increased energy efficiency because the keyword and overlay analysis showed more frequent publishing in these areas. The content analysis on two more specific sub-directions of interest, i.e., biomass-fuelled Stirling engine use in households and Stirling engine implications on energy security, showed that though research activity in these directions has increased lately, more profound research is needed, especially on aspects of energy security and independence. The content analysis revealed a lack of in-depth analysis on the effects of Stirling engine use on energy security or energy independence, which is suggested as a topical subject for future research. [ABSTRACT FROM AUTHOR]

Regenerators play a vital role in enhancing the overall performance of Stirling engines. Hence, this paper performed an energy and exergy analysis to elucidate the significance of regenerator characteristics concerning system performance, contributing to the optimal regenerator's design and selection. The relationship between regenerator structure, regenerator exergy destruction, and output power, thermal efficiency, and exergy efficiency for Stirling engines was established by integrating the thermal model of Stirling engines with a mathematical model of regenerators. In contrast to cross-flow and parallel-flow regenerators, a novel concept of inclined-flow regenerators, featuring a matrix surface inclined in the direction of gas flow, was developed to achieve higher and more balanced engine output power and energy utilization efficiency. A comprehensive investigation was conducted into the effects of matrix structure types and regenerator geometries on the performance of both regenerators and engines. The results reveal that, following structural optimization, Stirling engines equipped with the inclined-flow regenerator demonstrate a substantial 16.6%, 38.3%, and 37.2% increase in power output, thermal efficiency, and exergy efficiency, respectively, compared to those equipped with cross-flow regenerators. In contrast, when compared to engines fitted with parallel-flow regenerators, they experience a 13.5% reduction in power output but achieve remarkable enhancements of 45.4% and 36.7% in thermal and exergy efficiency, respectively. This study introduces new insights into selecting regenerator structures for enhancing the output performance of Stirling engines. [ABSTRACT FROM AUTHOR]

This paper focuses on the study of gamma-type Stirling engine prototype using a combined Schmidt closed-form and mechanical loss analysis. Not restricted to optimizing the indicated power as classic Schmidt theory is set to, this analysis allows to maximize the shaft power due to the mechanical loss in power transmission. For this purpose, MATLAB code was developed to calculate the indicated and the shaft powers of the engine at different operating parameters. The results showed that shaft power peaks at swept volume ratios smaller than those of indicated power at different values of mechanism effectiveness. Within the range of engine mechanism effectiveness typically between 0.7 and 0.9, it was found that maximum shaft power for this particular engine can be achieved at different optimum values of swept volume ratio between 0.75 and 0.95 and phase angle between 80° and 90°. However, an optimum swept volume ratio was found to be k=0.55 of the same engine size for different scenarios of operation. Also, the developed model can be used as a design tool in the preliminary stage to find the optimum geometry of the engine. The new engine design parameters including the stroke, the crank radius and power piston bore, and engine alteration were presented. [ABSTRACT FROM AUTHOR]

In the foreseeable future, the depletion of finite fossil fuel reserves is a growing concern due to the increasing consumption of these resources by humans. Moreover, the emission of greenhouse gases from fossil fuel consumption contributes to global warming, resulting in significant harm to the Earth's ecosystem. The Stirling engine (SE) offers an outstanding solution for harnessing various heat sources, including solar, nuclear, and fossil fuels, among others. It provides numerous advantages, such as high efficiency, a long lifespan, low noise levels, and minimal or no emissions. This study conducts a finite physical dimensions thermodynamic analysis (FPDT) on a gamma-type double-piston cylinder engine and compares the results with other isothermal models and experimental data. The current model's results align closely with those of other thermodynamic models. [ABSTRACT FROM AUTHOR]

Stirling engines represent a category of external heat transfer engines that demonstrate versatility by harnessing various heat sources, including solar energy, bio-mass, conventional fuel, and nuclear power. Achieving high thermal efficiency in power production has been a paramount concern driving researchers across the globe to focus on developing Stirling engines. A gamma-type double-piston Stirling engine has been carefully selected for detailed analysis in this research endeavour. A polytropic model is employed in the investigation to gain deeper insights into the engine's behaviour. The outcomes derived from the polytropic analysis are subsequently compared with a classical adiabatic analysis. Remarkably, the polytropic approach significantly outperforms the classical adiabatic analysis in enhancing the overall performance of the Stirling engine. The power and efficiency obtained from the ideal polytropic analysis were 90.30 W, which is very close to the ideal adiabatic and experimental efficiency. The results hold significant promise for advancing the efficiency and practical application of Stirling engines, reinforcing their position as a prominent contender in pursuing sustainable and highly efficient power generation technologies. [ABSTRACT FROM AUTHOR]

Air pollution is greatly influenced by the emissions generated by automotive engines, making it a pressing concern. To address this issue, a considerable amount of research is currently devoted to recovering waste heat from these engines. A gamma-type Stirling engine has been meticulously chosen to achieve this specific objective. This study elucidates a new isothermal method that effectively analyses Stirling engines. A set of differential equations is proficiently solved by employing the powerful MATLAB R2020a software. Remarkably, the simulation results obtained from this computational approach closely align with the experimental data, indicating the accuracy and reliability of the methodology. Furthermore, this research delves into the feasibility of employing the Stirling engine as a Combined Cooling, Heating and Power (CCHP) system, shedding light on its potential applications in various domains. [ABSTRACT FROM AUTHOR]

The Stirling engine, invented in 1816, was initially lacking comprehensive scientific understanding, which only surfaced after a considerable 50-year period. In the present era, impressive strides have been made in enhancing the performance of Stirling engines by implementing thermodynamic cycles. Despite these advancements, there remains untapped potential for further improvements by applying soft computing methods. To address this, the focal point of this research paper centres around optimizing the Stirling engine, specifically focusing on a gamma-type double-piston Stirling engine and leveraging genetic algorithms to achieve the desired enhancements. The results from this analysis are meticulously compared with experimental data, validating the approach's efficacy. Additionally, this paper explores the potential impact of utilizing cryogenic fluids as coolants on the Stirling engine's performance. [ABSTRACT FROM AUTHOR]

The Stirling engine, a type of external combustion engine utilizing a compressible fluid as its working medium, holds promise as a highly efficient device for converting heat into mechanical work at Carnot efficiency. This research conducts a detailed analysis, comparing the Hargreaves isothermal model and the Schmidt model specifically for the gamma-type Stirling engine. The study examines the impact of dead volume on the engine's performance, revealing that the engine network is solely influenced by these volumes. Furthermore, it highlights the effectiveness of the Hargreaves model for the performance analysis of gamma-type Stirling engines. [ABSTRACT FROM AUTHOR]

In light of green solutions to address the shortage of freshwater shortage, energy crisis, and climate change. Tri-generation renewable systems are recently efficient approaches that can offer multiple energy outputs, such as heat, electricity, and distilled water. This paper presents a new hybrid freshwater production system driven by renewable energy for enhanced performance and waste heat recovery. This hybrid system proposes the utilization of reverse osmosis, an adsorption distillation system, and a solar dish Stirling engine (RO-ADS/SDSE). The cooperative concept is based on the re-desalination of the brine of the RO unit using an adsorption desalination system driven by the heat rejected from the SDSE, while the RO system is driven by the electrical energy produced by the Stirling engine. A mathematical model conducted in MATLAB coupled with EES package is developed to investigate the performance of the proposed RO-ADS/SDSE with and without pressure recovery (PR) mode at different salinity concentrations varying from 30000 to 50000 ppm at a constant feed pressure of 80 bar. The investigation is conducted based on the meteorological data of Tianjin, China. The results showed significant superiority in the performance of the proposed RO-ADS/SDSE system, as the annual freshwater production rate of the RO-ADS/SDSE with PR increased by up to 3000 m3 compared to 1700 m3 for the standalone RO system at a feed salinity of 45000 ppm and feed pressure of 80 bar. On a daily basis, the hourly permeating flow rate of the RO-ADS/SDSE with PR increased from 2.30 m3/h to 2.60 m3/h, and the permeate salinity decreased from 190 to 120 ppm. While the daily electricity consumption decreased from 5.20 to 4.40 kWh/m3. In conclusion, the proposed RO-ADS/SDSE system with PR can be considered a promising approach in maximizing the performance of desalination systems. [Display omitted] • Hybridization of a solar dish/Stirling engine with reverse osmosis/adsorption distillation (SDSE/RO-ADS) is studied. • RO-ADS/SDSE is simulated with and without pressure recovery at various salinity concentrations. • Freshwater product of SDSE/ RO-ADS is increased by up to 3000 m3/yr compared to 1700 m3 for RO system. • Daily specific electricity consumption is decreased from 5.20 to 4.40 kWh/m3. • Cost per liter of water of RO-ADS/SDSE reached 1.54 $/m3 with a reduction of 3.75% over RO system. [ABSTRACT FROM AUTHOR]

This paper presents a novel method to estimate the design parameters of a diaphragm thermoacoustic Stirling engine and investigate the stable limit cycle (sufficient condition) of the engine dynamic using the genetic algorithm and system energy changes. In this regard, first, the parametric equations are extracted by employing both the governing equations of the engine and energy standpoint. Next, V c 0 (initial volume of compression space), R q (pneumatic resistance), V h 0 (initial volume of expansion space), and hot gas temperature ( T h ) are taken as the design parameters in this study. Genetic algorithm and parametric equations were then utilized to estimate the chosen design parameters. Next, the sufficient condition of the engine is evaluated based on the estimated design parameters. The simulated outcomes are shown that the sufficient condition is satisfied by the estimated design parameters. Afterward, the simulated results are validated using experimental data gathered from the constructed SUTech-SR-3 engine. Comparing the extracted data eventuates a proper method of estimating design parameters and satisfying the sufficient condition related to the SUTech-SR-3 engine. It is worth noting that in this research, the dynamic of the thermoacoustic Stirling engine has investigated using a mechanical point of view. Also, in this paper, only the dynamic behavior of the engine has been investigated, and the production power and work have not been studied. [ABSTRACT FROM AUTHOR]

The Stirling engine, renowned for its high theoretical efficiency, is capable of partaking an active role in the current energy transition. Given its closed-cycle operation, the choice of the working fluid is pivotal in designing the Stirling engine. Dinitrogen tetroxide N2O4 has been extensively investigated in the past, based on the ideal gas thermodynamic model, as a chemically reactive working fluid for Stirling cycles. This molecule reversibly and rapidly dissociates into nitrogen dioxide NO2–and recombines into N2O4–under the influence of thermodynamic transformations throughout the cycle, in accordance with chemical equilibrium. Addressing discrepancies in previous studies, this work aims at assessing a wide range of theoretical chemically reactive gases as working fluids in a Stirling cycle, employing the ideal gas mixture model. The behavior of each reactive fluid is examined throughout the cycle, and the thermodynamic performance is evaluated. Therefore, this work quantifies and analyzes the thermodynamic performance of a chemically reactive Stirling engine. Results indicate a slight increase in the net specific work output with certain reactive fluids, offering a thermal efficiency comparable to that of inert working fluids. In addition, it is emphasized that for chemically reactive working fluids, the isochoric heat exchange within the internal regenerator is incomplete due to chemical reactions, in contrast to the case of inert fluids. To address this, either a supplementary heat source, heat sink, or both are required during the isochoric processes. Furthermore, chemically reactive fluids in the Stirling engine induce irreversibility in the internal regenerator, stemming from heat exchange across a finite temperature difference, penalizing the thermal efficiency of the engine for the majority of reactive fluids studied.

A pressure-volume diagram is often used to determine the indicated work of a Stirling engine. In this study, both the laser triangulation and hybrid Harris corner detection methods are proposed. The volume variations in the Stirling engines can be measured directly without complicated calculations. The variations in the pressure of the working fluid in the engine are measured by a piezoresistive pressure sensor. To confirm the proposed methods, a flat alpha-type Stirling engine was tested. In the laser triangulation method, a laser sensor is used to measure the variation in the crank angle of the shaft. In the hybrid Harris corner detection method, the crank angle of the shaft is obtained by analyzing the images of the mechanism recorded by a high-speed camera. The volume of the working spaces is obtained according to the geometry of the driving mechanism as well as the engine speed. In this study, the pressure-volume diagram of the proposed engine under different operating speeds is measured and compared. The results indicate that the difference in the engine speed and phase angle measured by both methods is 2.3 % and 2.9 %, respectively. The indicated powers of the engine measured by both methods with a heating temperature of 500 °C at 765 ± 5 rpm are 5.789 W and 6.904 W, respectively. The relative difference between the volume variations measured by both methods is lower than 0.5 %. The hybrid Harris corner detection method can obtain more precise results than the laser triangulation method.

This study aims to compare the technological solutions that can contribute to more sustainable energy use in the residential sector. Specifically, the goal of the study is to evaluate the environmental impact of different energy (heat and electricity) supply technologies applicable for an average size single-family building in Latvia, a country known for climatic condition characterized by cold winters with frequent snowfall. The study applies the lifecycle assessment methodology of ISO 14040 and the impact assessment method known as ReCiPe 2016 v1.1, which has not been used before for the scope addressed in the study in the context of single-family building energy supply technologies for climatic conditions in Latvia. Thus, the results of the study will provide new information for more sustainable energy solutions in this area of study. The technologies included in the defined scenarios are conventional boiler, electricity from the grid, Stirling engine, and solar photovoltaics (PV). The results of the lifecycle impact assessment for damage categories revealed that all scenarios have a high impact on human health due to fine particulate matter formation followed by global warming. Regarding the damage to the ecosystem, the terrestrial ecotoxicity category has highest impact, followed by global warming. Sensitivity analyses affirmed the model’s validity and also showed that the impacts of conventional systems were most sensitive to changes in electricity consumption, and therefore, the scenarios with electricity supply from a Stirling engine or PV can be considered a more robust solution under changing electricity demands from an environmental perspective.

The article briefly provides basic information about the principle of operation, design schemes and thermodynamic cycles of the Stirling engine. Advantages and disadvantages are considered. The predominant areas of application are shown. The article is useful for teachers and students of technical universities.

There is a critical need to use the abundantly available solar energy worldwide due to the global energy crisis. The goal of this study is to demonstrate the residential use of a stirling engine powered by solar energy in Karachi, Pakistan. The design was carried out to produce a power output of 5 kW in order to address the issues with household and rural area power generating. The design was simulated using MATLAB. The use of solar energy as the engine's heat input was one of the design's key components. This allowed the engine to be built for locations with a lot of solar radiation. In regions with abundant solar energy, solar cookers, sun air warmers, and other appliances may be used. For power generation, however, the Stirling engine was chosen. Calculations of the sun intensity showed that 5 kW of Stirling engine output could be generated from 12 kW of solar electricity. The concentrator for concentrating and reflecting the incoming radiations to the Stirling engine was selected as a solar parabolic dish. This process heated the engine's working fluid, which then expanded and contracted due to thermodynamic forces to produce the engine's power strokes.

With the great advantages and continuous innovations, prolific research efforts have been devoted to the Stirling engine (SE) domain driven by the sustainability development. In this study, a bibliometric analysis is conducted to explore the research tend and hotspots of SE. The country co-authorship, institute co-authorship and keyword networks are engendered from the visual map using VOSviewer, showing China ranks the first with the total number of published articles and the majority publications are presented by Chinese Academy of Sciences. Owing to the highest node centrality, the research findings in USA can be considered the most influential and greatly worthy being referred, particularly represented by the early contribution for thermo-acoustic SE. The total 7 keyword clusters are classified through the top terms in Citespace and 4 of them are related to its energy supply system, demonstrating the typical application of SE-based combined heat and power (CHP) and integrated multi-energy complementary system have gained much attention. Based on this, a detailed review of SE-based energy supply systems is further conducted through the system forms, 4E performance evaluation and soft model combing optimization solutions. Several relevant issues hindering the improvement of these terms are summarized, providing the potential guides to help develop the SE-based energy supply system.

South Africa’s national power grid is currently in dire straits. The lack of a dependable power supplier and rising electricity costs force the public and businesses to look for alternatives to meet their energy needs. These alternatives are costly to implement and beyond the financial reach of most South Africans. The most common alternative energy source is solar photovoltaic systems with large battery banks to survive Eskom's long, regular load-shedding schedules. This research aims to design and simulate a combined solar-thermal and stored heat energy-powered Stirling engine for power generation. The output of the research simulation was compared to a standard photovoltaic installation of similar power output. The results for this paper were generated from the simulation software package MATLAB. Such a system must have a lower capital cost to compete with solar photovoltaic systems with battery backup. The Stirling system was found to be cheaper than the deep-cycle gel system and about 11% cheaper than the PV system using lithium iron phosphate.

This paper uses second-order software for evaluating five Stirling engine parameter's effect on its performance to select an appropriate configuration with optimal dimensions for its use in a concentrated solar power plant. Appropriate configuration, heater shape, bundle tube heat exchanger size, and regenerator type and geometry are studied. Results show that alpha type Stirling engine is the most suitable for high temperature differences, U-shaped tubes are advantageous in combining good efficiency and fewer pressure losses. Shortening inner diameter and increasing U-shaped tubes number is a good strategy to increase engine efficiency also an increase in tubes length generates a reduction in engine efficiency. Regarding the regenerator, the wire mesh regenerator presents a good compromise between minimum pressure drop and heat losses and provides better engine efficiency. For its size, better efficiency is obtained for a thicker mesh. [ABSTRACT FROM AUTHOR]

Three distinct thermodynamic analysis models are developed and applied to a renowned cryogenic engine (PPG-102), namely the isothermal model, the ideal Schmidt model, and the ideal adiabatic model. Through a comparative analysis, the theoretical outcomes derived from these models are juxtaposed with the corresponding theoretical results from the existing literature. The comprehensive evaluation of these findings demonstrates significant convergence, with minor deviations primarily attributed to the inherent assumptions underlying each model. The design of the PPG-102 engine is meticulously executed within the Solidworks environment, allowing for the subsequent simulation under operating conditions identical to those of the computational models. Remarkably, the simulation results closely approximate the outcomes of the adiabatic analysis, thus corroborating the validity and effectiveness of this particular model. In this work, the presented models, initially developed for thermal Stirling engines, are augmented and applied to a cryogenics Stirling engine, offering a unique understanding of the workings of this apparatus. [ABSTRACT FROM AUTHOR]

Nowadays, the biogas-powered gas turbine cycles in poly-generation systems play a crucial role due to increasing fuel prices, declining renewable energy sources, and environmental concerns associated with fossil fuels. Concerning the high temperature of expanded gas, a novel high-performance poly-generation plant is achievable by intelligently selecting different subsystems. This paper presents a novel biogas-fueled poly-generation plant for producing electricity, refrigeration load, distilled water, and hydrogen simultaneously using multi-level heat recovery. An extended assessment of the devised plant output is performed based on energy-exergy, environmental, and exergoeconomic criteria, in which the plant's gas turbine inlet temperature, preheated air temperature, air compressor pressure ratio, as well as turbine inlet pressure, are considered as variables. In the following, to demonstrate the advantages of using a Stirling engine, this study investigates two scenarios to reveal its superiority, and a bi-objective optimization is performed, where the objective functions comprise minimizing the poly-generation unit products cost and maximizing the sustainability index. When the plant is operated with a Stirling engine, the plant produces 986 kW of electricity, 137.5 kW of refrigeration load, 8.39 m3/h of distilled water, and 2.96 kg/h of hydrogen. In this case, the energetic and exergetic efficiencies of the proposed system are enhanced by 2.96% and 7.89%, respectively compared to non-Stirling engine mode. Also, the carbon dioxide emissions and sustainability index are ameliorated from 606.2 kg/MWh to 588.6 kg/MWh and from 1.47 to 1.5, respectively. In addition, the sensitivity analysis indicates that in a certain ratio of PR AC , the plant's performance reaches its optimal mode. Moreover, the unit cost of products and sustainability index are improved by 9.9% and 8%, respectively, compared to the base design case with the SE. [ABSTRACT FROM AUTHOR]

Stirling engines are capable in the renewable energy gain and the recovery of waste heat, both of which are important issues today. Existing studies revealed that the piston trajectories convergent to the Stirling cycle provide more power than traditional crank mechanism. In this study, a hypocycloid drive mechanism not used in the literature was optimized on the ideal piston trajectories for beta type Stirling engines. Optimization was realized to improve the isochoric heating and cooling processes as well as the isothermal compression and expansion. The cyclic work was treated as another objective succession. The optimal results taking into account these five objectives were obtained with the gear ratios of 5 and 4 for displacer piston and power piston, respectively. The piston dwells provided the enough objective succession not only for the both isochoric processes but also for the isothermal compression process, while failed in the isothermal expansion. In comparison with crank mechanism, a cyclic work increment of 10% was achieved in the near-ideal piston trajectories, but the maximum increment of 14% eventuated in some out of ideal.

Given the increase in global energy consumption, the scarcity of fossil fuel resources, and the rise in environmental pollution have necessitated the use of novel technologies in energy production. Among these technologies, fuel cells have attracted researcher's attention due to their low environmental pollution, high efficiency, and ability to be combined with other power generation systems. The present research studies the performance of a hybrid solid oxide fuel cell-Stirling engine (SOFC-ST) system from a thermodynamic perspective. To this end, the fuel cell and the Stirling engine were modeled via coding in MATLAB software. The decision variables in this analysis were the current density, fuel utilization factor, fuel flow rate, number of fuel cells, air flow rate, and type of fuel used in the fuel cell. According to the results, when hydrogen is used as the fuel in the fuel cell, its power generation increases from 60 kW to 67 kW and its efficiency rises from 44.2 % to 49.4 % with the addition of the Stirling engine. However, if the fuel is methane, the power generated by the fuel cell increases from 19.9 kW to 26.6 kW, while its efficiency increases from 36.9 % to 49.2 %. [ABSTRACT FROM AUTHOR]

The Stirling engine is an external combustion engine that can be utilized in electricity generation. Existing literature indicates that air is less expensive than helium as the working fluid but has the low power and efficiency. Hence, the present updated MATLAB code attempts to use a mixture of air and helium as working fluids or other mixtures of other gases. To this end, this software proposes an experimentally validated nonideal thermodynamic model for a Gama‐type Stirling engine. After validation, a mixing gas of air and helium was used instead of an operating fluid in the thermodynamic model. Finally, three examples were run to demonstrate the software outputs for a hybrid engine. [ABSTRACT FROM AUTHOR]

Stirling engines are currently of interest due to their adaptability to a wide range of energy sources. Since simple tools are needed to guide the sizing of prototypes in preliminary studies, this paper proposes two groups of simple models to estimate the maximum power in Stirling engines with a kinematic drive mechanism. The models are based on regression or ANN techniques, using data from 34 engines over a wide range of operating conditions. To facilitate the generalisation and interpretation of results, all models are expressed by dimensionless variables. The first group models use three input variables and 23 data points for correlation construction or training purposes, while another 66 data points are used for testing. Models in the second group use eight inputs and 18 data points for correlation construction or training, while another 36 data points are used for testing. The three-input models provide estimations of the maximum brake power with an acceptable accuracy for feasibility studies. Using eight-input models, the predictions of the maximum indicated power are very accurate, while those of the maximum brake power are less accurate, but acceptable for the preliminary design stage. In general, the best results are achieved with ANN models, although they only employ one hidden layer. [ABSTRACT FROM AUTHOR]

There is a critical need to use the abundantly available solar energy worldwide due to the global energy crisis. The goal of this study is to demonstrate the residential use of a stirling engine powered by solar energy in Karachi, Pakistan. The design was carried out to produce a power output of 5 kW in order to address the issues with household and rural area power generating. The design was simulated using MATLAB. The use of solar energy as the engine's heat input was one of the design's key components. This allowed the engine to be built for locations with a lot of solar radiation. In regions with abundant solar energy, solar cookers, sun air warmers, and other appliances may be used. For power generation, however, the Stirling engine was chosen. Calculations of the sun intensity showed that 5 kW of Stirling engine output could be generated from 12 kW of solar electricity. The concentrator for concentrating and reflecting the incoming radiations to the Stirling engine was selected as a solar parabolic dish. This process heated the engine's working fluid, which then expanded and contracted due to thermodynamic forces to produce the engine's power strokes. [ABSTRACT FROM AUTHOR]