Stirling System Research Articles

Investigation of the potential for electrification of remote areas using parabolic solar collectors in southern Algeria

The dish stirling technology holds great promise as a renewable energy solution for remote and off-grid electric regions, particularly in the southern areas of North Africa. In this research, we conducted simulations of a 100 kw Dish Stirling system to evaluate its feasibility in comparison to photovoltaic technology at five distinct locations in southern Algeria: Adrar (Bordj Badji Mokhtar), Illizi (Djanet), Tamanrasset (Ain Mertoutek), Tindouf, and Bechar. Our findings underscore the substantial potential of Dish Stirling Solar Power technology, with the Sahara region standing out as particularly promising. In this region, the Dish Stirling system consistently outperforms a 100 kw photovoltaic system across all selected locations. The Dish Stirling system achieves an average annual electricity generation of 256 mwh while simultaneously mitigating CO2 emissions by 177 tons annually. Among these locations, Djanet Illizi emerges as the most favorable, with the Dish Stirling system producing an impressive 288.43 mwh annually. This capacity is sufficient to meet the annual energy needs of 230 households, all while maintaining a competitive LCOE of 0.0378 USD/kwh. Comparative analysis with previous research illuminates the remarkable cost-effectiveness of Dish Stirling technology in southern Algeria, primarily due to its abundant direct normal irradiance levels. These findings underscore the immense potential of Dish Stirling systems as a clean and highly efficient energy solution, well-suited for demanding to address the energy needs of remote environments, such as those found in the southern border regions of Algeria.

The thermal and stored heat energy driving a Stirling engine for power generation

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.

Experimental investigation to evaluate the performance profile of a small-scale standalone concentrated solar parabolic dish Stirling system

In this study, a small-scale solar parabolic dish Stirling system (SPDSS) is designed, developed and experimentally operated to generate electricity. The developed system is composed of a solar concentrator, a Stirling engine-generator set, and dual-axis tracking mechanism. The locally assembled Stirling engine is air-filled, double-acting gamma, with a nominal power rating of 40 W. There are six essential output parameters including engine displacer temperature, average engine speed, generator terminal voltage, load current, electrical power and overall efficiency of the system, which have been measured experimentally to assess global performance of the system. The experimental results revealed that the developed system could yield a maximum engine displacer temperature of 275°C, average engine speed of 261 RPM, peak generator no-load terminal voltage of 31.3 V, maximum load current of 2.67 amps, maximum electrical power of 17 W and overall efficiency of 3.4%. The experimental results, for the purpose of validation, have also been compared with simulation results and found in good agreement.

Numerical study on a nuclear-powered Stirling system for space power generation

The use of nuclear-powered Stirling systems for planetary and deep space exploration applications has drawn increasing attention in recent decades. As the critical energy conversion unit in the system, the free-piston Stirling engine (FPSE) is characterized by high efficiency, low mass, compact configuration, robustness, and long lifetime, but difficult to accurately model and analyze. A self-developed numerical model of the whole system, coupled with a third-order model of the FPSE, was proposed for the first time, and a nuclear-powered Stirling system comprising eight 1 kW FPSEs was designed. The methodology for designing a system with high efficiency, high specific power, and compact structure was proposed. Furthermore, the internal heat transfer and loss mechanisms were analyzed. The results revealed that the engines’ performance could be improved by increasing the temperature ratio of the hot end to the cold end. However, this leads to a corresponding increase in the size and mass of the heat exchangers. It was shown that the optimum hot-end temperatures for maximizing the system efficiency exist at different cold-end temperatures due to the radiation heat loss of heat pipes. When the hot-end and cold-end temperatures are respectively 1050 K and 450 K, a maximum system efficiency of 25.64% could be obtained. Moreover, the system efficiency and specific power could be increased by optimizing the FPSEs’ parameters and enhancing the heat exchangers’ heat transfer capabilities, and the adverse effect of the heat sink fluctuation could be inhibited accordingly. The distribution of the exergy losses changes greatly with the operating temperatures, and the primary parameter to be optimized also changes accordingly.

A Summary: Dynamic and thermodynamic analysis of thermoacoustic and Stirling systems based on time-domain acoustic-electrical analogy

A unified fast transient simulation method for thermoacoustic and Stirling systems has been developed, named time-domain acoustic-electrical analogy (TDAEA) method. From a thermoacoustic theory point of view, the method captures the main acoustic impedance characteristics of the components and simplifies the calculations reasonably by using lumped models for components, thus remarkably reducing the computation. The TDAEA models of common components in thermoacoustic and Stirling systems are summarised with detail derivation. Two case studies are then carried out on free-piston Stirling generator (FPSG) and heat-driven thermoacoustic refrigerator (HDTR). Model verifications demonstrate the effectiveness and accuracy of the method: for the FPSG, the average deviation between the calculations and experiments in operating frequency, electric power, LA efficiency and thermal-to-electric efficiency are 5.0%, 16.3%, 2.4% and 26.9%, respectively; as for the HDTR, the deviation in cooling power lies in 29.9%. Using this method, transient evolutions can be obtained, which contains both start-up and steady stages. For start-up analysis, the transient operating frequency, pressure–volume diagram and limit cycle, etc, can be exhibited. Regarding the steady stage, the method is available to give the distribution of acoustic field and the losses in components. Moreover, the infulences of operating and geometric parameters on system performance can aslo be obtained. This study provides a new perspective and an effective method for fast transient simulation of thermoacoustic and Stirling systems, as well as gives a deeper understanding on the transient evolution of self-sustained oscillation and dynamic & thermodynamic cycles in these systems.

Solar-driven Dish Stirling System for sustainable power generation in Bangladesh: A case study in Cox’s Bazar

In recent years, the power sector of Bangladesh has seen a major development in terms of generation capacity. But as before, it is heavily dependent on fossil fuels overlooking the potential of renewable energy resources. The scope for grid-connected renewable energy systems has not been explored too far and in terms of solar thermal energy and concentrating solar power (CSP), it is even less. This study focuses on assessing the techno-economic feasibility of solar-driven Dish Stirling system for large-scale grid-connected power generation in Bangladesh. Detailed modeling and optimization of a 100 MW Dish Stirling power plant have been carried out in Cox’s Bazar, Bangladesh, a location suitable for solar energy harnessing due to favorable climatic conditions. The modeling parameters and weather data have been collected from relevant literature, various solar data providers, and specific plant parameters have been optimized for the Bangladeshi climatic condition. Simulation of the modeled plant carried out by the System Advisor Model (SAM) shows that, it can supply 129.856 GWh electricity annually operating at an overall efficiency of 24.91% which is much higher than the values reported in similar literature for the South-Asian regions. The levelized cost of electricity (LCOE) has been determined to be 10.18 cents/kWh, which is highly competitive and promising. The insights obtained from this study can be a perfect starting point for the policymakers and concerned authorities of Bangladesh to further explore the viability of this technology for renewable and sustainable power.

Development of Neural Network Prediction Models for the Energy Producibility of a Parabolic Dish: A Comparison with the Analytical Approach

Solar energy is one of the most widely exploited renewable/sustainable resources for electricity generation, with photovoltaic and concentrating solar power technologies at the forefront of research. This study focuses on the development of a neural network prediction model aimed at assessing the energy producibility of dish–Stirling systems, testing the methodology and offering a useful tool to support the design and sizing phases of the system at different installation sites. Employing the open-source platform TensorFlow, two different classes of feedforward neural networks were developed and validated (multilayer perceptron and radial basis function). The absolute novelty of this approach is the use of real data for the training phase and not predictions coming from another analytical/numerical model. Several neural networks were investigated by varying the level of depth, the number of neurons, and the computing resources involved for two different sets of input variables. The best of all the tested neural networks resulted in a coefficient of determination of 0.98 by comparing the predicted electrical output power values with those measured experimentally. The results confirmed the high reliability of the neural models, and the use of only open-source IT tools guarantees maximum transparency and replicability of the models.

Numerical investigation to assess the output performance of concentrated solar parabolic dish system

In this study, a standalone solar parabolic dish Stirling system is mathematically modeled and simulated using MATLAB to investigate the effects of material design and opt-geometrical parameters on output performance of the system. The concentrator diameter, rim angle, dispersion angle, incidence angle, solar angle, receiver emissivity, receiver absorbance, receiver thermal conductivity, and concentrator reflectance are the major parameters considered for investigation. The effects of the aforementioned parameters have been rigorously observed on Geometrical Concentration Ratio (G.C.R), receiver temperature, receiver thermal loss, output power, and overall efficiency of the system. In addition, the optimized values of the studied parameters have also been identified to establish the optimal geometrical configuration of the system. The results revealed that the maximum output power and the overall efficiency of the system have been calculated at 45° rim angle, 0.4° dispersion angle, 0° incidence angle, and 0.3° solar angle. At these optimal angles, receiver thermal loss may be significantly minimized while maintaining the desired G.C.R. The results, for the purpose of validation, have also been compared with theoretical and experimental dataset from the contemporary literature and found in good agreement.

Dynamic and thermodynamic characterization of a resonance tube-coupled free-piston Stirling engine-based combined cooling and power system

This paper proposes a novel resonance tube-coupled free-piston Stirling engine-based combined cooling and power (FPS-CCP) system for future application in scavenging unconventional natural gas from coal mines and oil fields. Unlike the traditional duplex Stirling system, the proposed system employs a resonance tube to couple an engine and a cryocooler. In addition, a linear alternator is introduced to facilitate startup and meet multiple demands, resulting in flexible adjustments and even higher exergy efficiency. A novel time-domain unsteady model based on thermoacoustic theory was developed to investigate the onset behavior of the (FPS-CCP) system. The proposed model successfully predicted the onset temperature and onset frequency. Results indicated that within the calculation range, the resonance tube with either a larger diameter or a shorter length leads to a lower onset temperature. Furthermore, the system performance under the steady-oscillating state was studied in terms of the typical operation characteristics and energy flow distribution. When the heating temperature is 833 Kand the mean pressure of helium gas is 5 MPa, the proposed system can provide a cooling capacity of 1000 W at 110 K and an electric power of 800 W with a global exergy efficiency of 29.4%, demonstrating an efficient power matching among the subsystems.

Performance evaluation of a stand-alone solar dish Stirling system for off–grid electrification

ABSTRACT The performance of solar-powered Stirling engine system with a parabolic dish collector to electrify rural residential houses is presented. The developed model considers both the nonlinearized heat losses of the solar dish collector and the effect of the irreversibility of the Stirling engine. Governing equations for the solar collector, receiver heat transfer, thermodynamic cycle for Stirling engine, and mechanical and electric energy conversion are integrated and simulated in MATLAB software. Validation of the current model against experimental data is found in a very good match. A simulated model located in southern Jordan is built as a case study. The model simulates the hourly thermal to the electric conversion of solar energy to meet the required household load. The simulations results predict that overall system efficiency during summer is around 30% while it is around 22% during wintertime. The optimal concentration ratio is about 230 for the current solar dish Stirling engines configuration studied in this work. Furthermore, the load of loss probability is found to decrease linearly with increasing collector size. It was found that the solar dish Stirling engine with proper reflector size can meet the load demand with high reliability factor. Finally, storage capacity equal to daily energy demand is sufficient to meet uncontrollable load under varying weather conditions during summer, spring, and fall seasons in Jordan.

Research on a new type of solar dish Stirling cogeneration system based on adjustable receiver and control strategy

With the increasing global demand for carbon emission reduction, solar energy has received great attention worldwide, with solar dish Stirling system as a representative technology. However, some shortcomings of the conventional design limit its commercial application. In this paper, a novel solar dish Stirling cogeneration system (SDSCS) with adjustable dual receiver is proposed. A control strategy for switching between power generation and heat production modes is established, which is based on direct normal irradiance (DNI). In order to verify the system performance, three regions with significant differences in DNI levels in Tianjin, Yinchuan, and Lhasa were selected for comparison of technical and economic indicators. The results show that, compared with the conventional system that can only generate electricity, the SDSCS can achieve a significantly higher proportion of system running time in three regions at 14.66%, 24.53%, and 34.32%, respectively. The comprehensive energy efficiency shows the same trend at 55.83%, 53.91%, and 41.03%. In addition, the load satisfaction rate calculated by the day of the three regions is 43.05%, 81.46%, and 94.04%, respectively. In terms of levelized energy cost, the value of using SDSCS is 6.77 CNY/(kW·h), 3.37 CNY/(kW·h), and 1.94 CNY/(kW·h), lower than conventional system except for Tianjin.

Techno-Economic Assessment of Concentrated Solar and Photovoltaic Power Plants in Brazil

The need for a diverse energy matrix has been promoting a favorable environment for integrating new renewable energy sources, such as Concentrated Solar Power plants (CSPs). Nonetheless, as a consequence of the incipient solar generation via CSPs in Brazil, there is a unsatisfactory number of researches that handle technical and economic assessments of CSP plants performance on this country. Given this scenario, this study proposes an assessment of the technoeconomic viability of the implementation of 100 MW CSP plants in Brazil, considering the Solar Tower (ST) systems, Parabolic Trough Collectors (PTC), Linear Fresnel (LFR) Reflectors and Dish Stirling (DS) Systems, and comparing the results to a photovoltaic (PV) plant. This study utilizes project data of power plants collected from the relevant literature and applies it to the city of Bom Jesus da Lapa, Brazil. The CSP techno-economic viability is evaluated through the analysis of the annual energy generated, as well as the economic viability indicators, such as the Net Present Value, the Internal Rate of Return, the Discounted Payback and the Levelized Cost of Energy, and through a single-variable sensitivity analysis. This analysis employs the discounted cash flow model, considering the energy trade in a Regulated Contracting Environment

A novel Gamma‐type duplex Stirling system to convert heat energy to cooling power: Theoretical and experimental study

This article aims at coupling two Stirling machines together to produce cooling power from different heat sources. Two identical Gamma-type ST500 Stirling machines are coupled together. The first machine, named Stirling engine, is powered by burning natural gas and an electrical power supply as an auxiliary starter. The Stirling engine is connected to a second Stirling machine named Stirling refrigerator by a mechanical belt. The driving force is transferred to the Stirling refrigerator using the mechanical belt. Mechanical energy is then converted to cold energy in the Stirling refrigerator. This study presents the experimental and theoretical results by examining the whole system named duplex Stirling refrigerator system. Five experiments are performed on the system at different pressures to evaluate the results. Water circulation in copper coils is used to determine the cooling flux produced by the Stirling refrigerator. Finally, the coefficient of performance (COP) is calculated. The experimental data are validated using a MATLAB-based code developed based on the presented formulas in this study. The results show that the system's maximum COP and electrical efficiency, consisting of two similar 500 W Gamma-type Stirling machines, are between 0.21% and 70.8%, respectively. Setup theoretical and experimental efficiencies are 0.24 and 0.21, respectively, at the best case. The experimental results of the duplex Stirling refrigerator system used in this study are compared with the simulation results. Finally, the experimental results of this study are compared with some other reported results from different authors on the subject of the duplex Stirling refrigerator.

The performance prediction and techno-economic analyses of a stand-alone parabolic solar dish/stirling system, for Jamshoro, Pakistan

This study aims to propose a simulation as well as mathematical model to carry out the performance assessment and efficiency improvement of a stand-alone Parabolic Solar Dish Stirling (PSDS) system. The simulation for a 25 ​kW PSDS system is performed in the System Advisor Model (SAM) under the environmental conditions of Jamshoro, Sindh, Pakistan. The results show that the city has a good potential of direct solar irradiance with yearly average value of 1719.15 ​kWh/m2/y. The system can generate yearly 38.6 ​MWh with overall system net efficiency of 23.39%. Whereas, the maximum energy of 3.38 ​MWh is produced in month of January, due to high solar irradiance. However, the lowest energy of 2.15 ​MWh is produced in July, due to the monsoon spell in selected city. Furthermore, from the techno-economic analyses of the proposed system, the levelized cost of energy is found to be 0.13 $/kWh, which is quite low. As the Stirling Engine (SE) works at higher temperature, so, increasing the diameter of concentrator results more thermal energy at the cavity. The solar radiations are high around the solar noon, therefore, the operating temperature can damage the hot-side of SE due to thermal overloading. In future, to protect the hot-side of SE, it is recommended to use thermo electric generator.

Operation of a Dish Stirling Heliothermic System with Directly Illuminated Tube Receiver

The generation of electricity from solar energy is one of the options within the renewable technologies that have gained much importance in recent years. Within this area, Dish Stirling systems stand out among solar concentration technologies, as they have the highest efficiency in converting thermal energy into electricity. Unfortunately, there are few publications and information on operating parameters of this type of technology. For this reason, this paper presents a methodology to characterize the behavior of this type of system, considering project parameters of a system installed in the city of Itajuba-MG Brazil. In the initial stage, a geometric and optical analysis is presented, which allows us to determine parameters such as the parabolic disk opening area and optical parameters that define the performance of this component. In the next stage, a thermal analysis is elaborated as a way to quantify the losses in the receiver system and to be able to calculate the energy supplied to the Stirling engine fluid. Finally, relationships are established to characterize the behavior of the Stirling engine working with a DIR type receiver. The results show that for speeds below 8 m/s, the heat loss due to radiation is higher than the loss due to convection, representing up to 90% of the total heat loss in the system, for solar irradiation of 1000 W/m2, the maximum electrical power obtained by the system was 0.99 kW.

Techno‐enviro‐economic assessment of a stand‐alone parabolic solar dish stirling system for electricity generation

In this study, a stand-alone parabolic solar dish/Stirling (PSDS) system model is developed and investigated. The techno-enviro-economic performance of a 25-kW stand-alone PSDS system is simulated in the System Advisor Model (SAM) tool under ambient conditions of Jamshoro, Pakistan. The avoided CO2 emissions due to the installation of the proposed system are calculated in an Excel spreadsheet. The methodology for emissions calculation is based on the average value of emissions per kWh recommended by the Intergovernmental Panel on Climate Change (IPCC). The results indicate that the proposed PSDS system generates 38.6 MWh of electrical energy annually, and the maximum energy of 3.38 MWh is achieved in January. The main reason for that is the highest value of DNI in that month. The system has attained a net efficiency of 23.39% and a levelized cost of energy (LCOE) of 0.13 $/kWh. The yearly emissions from PSDS are 762 kg, which is only 2.2% and 4.69% of coal and natural gas, respectively. Moreover, the sensitivity analysis of the PSDS system showed that the projected mirror area and collector cost affects the power output and cost of generation significantly.

Thermo-economic analysis and multi-objective optimization of a solar dish Stirling engine

ABSTRACT Stirling engines operate in a variety of temperatures and the electric power production via dish Stirling systems could be considered as an appropriate alternative for high-temperature solar concentrator energy harvesting systems. To this end, by performing various studies and analyses on the engine, Stirling cycle, and heat exchangers while utilizing the solar energy as the input thermal energy of the Stirling engine, parameters with the highest effect on the output power and engine stability are detected and considered as optimization variables. In this case, output power, thermal efficiency, and economic evaluation are taken to be the three suitable objective functions for multi-objective optimization. Moreover, two optimization algorithms of MOPSO and SPEA/2 are introduced and applied for the first time for analyzing a dish Stirling engine. Finally, the optimization variable values before and after optimization, as well as the yielded improvement in the output power and thermal efficiency are presented, using LINAMP and TOPSIS techniques for optimum point selection. The optimization results show that the optimum conditions for three objective functions in case of three-objective optimization acquired by LINAMP and TOPSIS methods are 38.96, 0.2391, 0.3127 and 38.71, 0.2433, 0.3152 of P-η-F, respectively, acquired from optimization by SPEA/2 algorithm. However, single-objective optimization of each of the three objective functions optimized separately yields the values of (42.27, 27.51, and 0.3379) and (42.12, 27.62, and 0.3361) for MOPSO and SPEA/2 algorithms, respectively.

Simulation of pressure imbalance phenomena in a double-acting α-cycle Stirling engine

This article presents an exploratory process of finding root causes of an undesirable pressure imbalance in an industrial high temperature heat pump based on a reverse Stirling engine using a simulation model of the process. Different types of Stirling engine configurations can be used as heat engines converting heat to power or as heat pumps using power to raise the temperature of low temperature heat to a higher level. The studied heat pump has a double-acting α-configuration, with two double-acting pistons interacting with a working fluid on each piston face. Theoretically, this configuration creates two separate circuits, which can be treated in isolation of each other, but in practice, some working fluid will leak through the piston rings. A simulation model of the studied Stirling system using the software Simulink was developed to investigate to which degree such piston-ring leakages could affect system pressures. By modelling piston-ring leakage and experimenting with different combinations of model parameters, different types of effects on system pressures are seen in the simulations, offering explanations for pressure fluctuations observed in the real heat pump system. These pressure phenomena may well be present in other reciprocating systems, and identifying them is a first step in preventing them in order to increase system stability. An interesting observation was that the direction of the imbalance was not necessarily determined by the direction of the leak through the piston rings, but by the piston position at the onset of the leak. The simulation model is shown to be capable of reproducing complex patterns seen in the measurements of the real process by simple modifications and adaptation of model parameters.

Design a Solar Powered Stirling Engine Prototype to Produce Electricity

For the concerns of environmental issue such as global warming, sustainable and green way to produce energy is highly in demand. Dish Stirling system is one of the most efficient system among others concentrated solar power technologies. However, the system is in disadvantage in terms of cost and reliability when compare to others CSP technologies. In this study, a fundamental prototype of solar powered dish Stirling engine is designed, manufactured, and tested. One component of the prototype which is the power piston is malfunctioning. It was found that the accuracy requirement of the manufacturing of the prototype was high and it requires high skill and experience in machining process.

Thermo-ecological assessment of Stirling engine with regenerator fed with cryogenic exergy of liquid natural gas (LNG)

The paper presents a thermo-ecological analysis of a liquefied natural gas regasification system equipped with a Stirling engine. The proposed system includes an alpha configuration machine, working as a cold engine with the heat sink acting as the evaporator for the LNG and the upper heat source being at ambient temperature (sea water) or moderately higher. The engines are modelled using two approaches developed by the authors, that is a CFD model and a second-order one-dimensional model. First a small engine is modelled by both CFD and the second order approach to compare results and after confirming their similarity, due to a lower computational cost a larger machine is modelled with the second order model. Due to the heat transfer conditions being crucial for a Stirling cycle machine's performance, those are investigated. It is shown that the internal, convective heat transfer coefficients are much higher in cryogenic conditions than in typical ones. The results of engine assessment are used for the Thermo-ecological cost (TEC) analysis. Within the thermo-ecological analysis, the influence of selected parameters is demonstrated. Additionally the TEC of electricity generated in cold power plant is presented for different configurations. In the case of analysed Stirling systems savings of natural gas reach the level of only 0.5%. However, when TEC of electricity is calculated, the savings are at the level of 72%. The proposed theoretical investigations are the base for the acquisition of new knowledge in the field of possible ways of converting cryogenic exergy of LNG into electricity and optimization of this cycle with strong focus on ecological effects, including the TEC.