Stirling System Research Articles

Optimization of Output Power and Thermal Efficiency of Solar‐Dish Stirling Engine Using Finite Time Thermodynamic Analysis

This paper presents an investigation on finite time thermodynamic (FTT) evaluation of a solar‐dish Stirling heat engine. FTTs has been applied to determine the output power and the corresponding thermal efficiency, exergetic efficiency, and the rate of entropy generation of a solar Stirling system with a finite rate of heat transfer, regenerative heat loss, conductive thermal bridging loss, and finite regeneration process time. Further imperfect performance of the dish collector and convective/radiative heat transfer mechanisms in the hot end as well as the convective heat transfer in the heat sink of the engine are considered in the developed model. The output power of the engine is maximized while the highest temperature of the engine is considered as a design parameter. In addition, thermal efficiency, exergetic efficiency, and the rate of entropy generation corresponding to the optimum value of the output power is evaluated. Results imply that the optimized absorber temperature is some where between 850 K and 1000 K. Sensitivity of results against variations of the system parameters are studied in detail. The present analysis provides a good theoretical guidance for the designing of dish collectors and operating the Stirling heat engine system.

Multi-objective optimization of Stirling engine using non-ideal adiabatic method

In the recent years, remarkable attention is drawn to Stirling engine due to noticeable advantages, for instance a lot of resources such as biomass, fossil fuels and solar energy can be applied as heat source. Great numbers of studies are conducted on Stirling engines and non-ideal adiabatic method is one of them. In the present study, the efficiency and the power loss due to pressure drop into the heat exchangers are optimized for a Stirling system using non-ideal adiabatic analysis and the second-version Non-dominated Sorting Genetic Algorithm. The optimized answers are chosen from the results using three decision-making methods. The applied methods were compared at last and the best results were obtained for the technique for order preference by similarity to ideal solution decision making method.

Optimization of Power Solar Dish-Stirling: Induced Effects of Heat Source Temperature and Working Fluid Temperature in Hot Side

This paper presents an investigation on finite time thermodynamic evaluation and analysis of a Solar-dish Stirling heat engine. Finite time thermodynamics has been applied to determine the net power output and thermal efficiency of the Stirling system with finite-rate heat transfer, regenerative heat loss, conductive thermal bridging loss and finite regeneration process time. The model investigates the effects of the inlet temperature of the heat source and heat sink, the volumetric ratio of the engine, effectiveness of heat exchangers and heat capacitance rates on the net power output and thermal efficiency of the engine and entropy generation. The thermal efficiency of the cycle corresponding to the magnitude of the maximized power of the engine is evaluated. Finally, sensitivities of results in a variation of the thermal parameters of the engine are studied. The present analysis provides a good theoretical guideline for designing and operating of the Stirling heat engine systems.

1D modelling of an alpha type Stirling engine

In this paper, a 1-D model of an half alpha type “double-acting” Stirling engine (made up of two double-acting pistons, two hot heat-exchangers, two cold heat-exchangers and a common recuperator-regenerator for the two separate gas circuits, all that giving two cycles with 180° phasing) is presented. In this architecture, two cylinders, containing, each one, a double-acting piston, are combined in order to operate like two parallel Stirling systems in opposition of phase. This model, derived from Andersen’s model, is used to describe the compressible flows in the half-engine, under energy transfers. A finite-volume numerical method is applied for the equations of energy, mass and momentum assessment. This modelling was carried out using the Matlab/Simulink software. The results of this dynamic modelling relate to one half engine. We obtain the evolution of the physical parameters (density, pressure and temperature), and the (p, V) cycle. The influence of the various assumptions was studied. A parametric study was carried out in order to obtain the optimal values of the geometry of the engine and its ideal speed of operation.

Dish Stirling Advanced Latent Storage Feasibility

Dish-Stirling systems have been demonstrated to provide high-efficiency solar-only electrical generation, holding the world record at 31.25%. This high efficiency results in a system with a high possibility of meeting the DOE SunShot goal of $0.06/kWh. Current dish-Stirling systems do not incorporate thermal storage. For the next generation of non-intermittent and cost-competitive solar power plants, we propose a thermal energy storage system that combines latent (phase-change) energy transport and latent energy storage in order to match the isothermal input requirements of Stirling engines while also maximizing the exergetic efficiency of the entire system.This paper reports on the technical advantages and challenges of dish Stirling with storage, to make a preliminary estimate as to the technical feasibility of such a system. The proposed system with storage incorporates high temperature latent transport and latent storage, providing an exergetic match to the isothermal input of the Stirling cycle. The transport from the receiver to the storage, and from storage to the engine, is accomplished with advanced sodium heat pipes. The storage is in a solid-liquid phase change material (PCM), likely a metallic eutectic to reduce exergy losses in thermal conduction.We model a dish Stirling system at a block level, using a combination of real data from several dish systems with and without heat pipe transport, and determine annual energy production and revenue streams based on Barstow California weather data and Southern California Edison Time of Day pricing. We optimize the system on solar multiple, capacity of storage, and several operational strategies.We find that a storage system using metallic eutectic phase change storage results in a feasible physical embodiment, with mass, volume, and complexity suitable for 25kWe dish Stirling systems. The results indicate a system with 6hours of storage and a solar multiple of 1.25 provides the optimum impact to LCOE and profit for the range of cases studied.A storage system applied to dish Stirling will leverage the current high performance systems, increasing the value to the utilities and transmission entities. A feasible embodiment has been proposed, which with sufficient development will re-establish dish Stirling as a leading energy option.

Design and Analysis of a Novel Hybrid Solar/Gas Dish Stirling System (HS/GDSS)

In this paper, a 20kW design capacity solar parabolic dish concentrator hybrid solar/gas dish Stirling system (HS/GDSS) is proposed. To ensure a steady operation of an electricity power plant, HS/GDSS uses gas as complement when solar radiation is weak. Thermodynamic models were made to conduct design of system parameters. After detail characteristics were chosen, analysis was carried out to evaluate this system. The results show that within design condition, overall efficiency of the system is 27.58% at daytime and 33.94% at night, which has advantages over single-energy solar dish Stirling electricity power plant.

Feasibility Study of Dish Stirling Systems in Malaysia

This paper focuses on the feasibility study ofDish Stirling systems in Malaysia from technical simulations using System Advisor Model (SAM), a software developed by the National Renewable energy Laboratory as a step towardsmore environmentally cleaner solutions to electrical power generation. Kuala Lumpur, Malaysia’s capital city, experiences an annual Global Horizontal Irradiance of 1561.9 kWh/m2 and low Direct Normal Irradiance of 373.1 kWh/m2 due to high reflection and scatter by present clouds. The highest annual energy output of DS systems in Malaysia is located in Georgetown at 739,524 kWh, however, representing only 14 % of annual energy output in Phoenix. Simulations results conclude Malaysia as a location unsuitable for Dish Stirling systems and potentially other Concentrated Solar Power systems

Techno Economic Study of the Utilization of Solar Dish Stirling Technology for Electricity Generation at the Algerian Sahara

This article presents the results of an investigation concerning the application of two configurations of the Dish Stirling system (prototype, mature) in order to use it as stand alone systems under the Algerian climate for three different sites (Algiers, Bechar, and Tamanrasset). Furthermore, this article presents the social and environmental impacts of using this technology. An analysis of the daily performances, monthly performances, and annual performances for the three sites has been presented. In addition, an economic assessment of these systems has been performed. The results show that both Tamanrasset and Bechar are more suitable than the Algiers site for the implementation of the Dish Stirling systems.

Multi-objective thermodynamic-based optimization of output power of Solar Dish-Stirling engine by implementing an evolutionary algorithm

A solar-powered high temperature differential Stirling engine has been considered for optimization with multiple criteria. A mathematical model based on the finite-time thermodynamics has been developed so that the output power and thermal efficiency and the rate of entropy generation of the solar Stirling system with finite rate of heat transfer, regenerative heat loss, conductive thermal bridging loss and finite regeneration process time are obtained. Furthermore, imperfect performance of the dish collector and convective/radiative heat transfer mechanisms at the hot end as well as the convective heat transfer at the heat sink of the engine are considered in the developed model. Three objective functions including the output power and overall thermal efficiency have been considered simultaneously for maximization and the rate of entropy generation of the Stirling engine are minimized at the same time. Multi-objective evolutionary algorithms (MOEAs) based on NSGA-II algorithm has been employed while the Effectiveness’s of regenerator, the Effectiveness’s of the low temperature heat exchanger, the Effectiveness’s of the high temperature heat exchanger, heat capacitance rate of the heat sink, heat capacitance rate of the heat source, temperatures of the working fluid in the high temperature isothermal process and temperatures of the working fluid in the low temperature isothermal process are considered as decision variables. Pareto optimal frontier has been obtained and a final optimal solution has been selected using various decision-making approaches including the fuzzy Bellman–Zadeh, LINMAP and TOPSIS methods.

Designing a solar powered Stirling heat engine based on multiple criteria: Maximized thermal efficiency and power

A solar-powered high temperature differential Stirling engine was considered for optimization using multiple criteria. A thermal model was developed so that the output power and thermal efficiency of the solar Stirling system with finite rate of heat transfer, regenerative heat loss, conductive thermal bridging loss, finite regeneration process time and imperfect performance of the dish collector could be obtained. The output power and overall thermal efficiency were considered for simultaneous maximization. Multi-objective evolutionary algorithms (MOEAs) based on the NSGA-II algorithm were employed while the solar absorber temperature and the highest and lowest temperatures of the working fluid were considered the decision variables. The Pareto optimal frontier was obtained and a final optimal solution was also selected using various decision-making methods including the fuzzy Bellman–Zadeh, LINMAP and TOPSIS. It was found that multi-objective optimization could yield results with a relatively low deviation from the ideal solution in comparison to the conventional single objective approach. Furthermore, it was shown that, if the weight of thermal efficiency as one of the objective functions is considered to be greater than weight of the power objective, lower absorber temperature and low temperature ratio should be considered in the design of the Stirling engine.

Application Model for a Stirling Engine Micro-Generation System in Caravans in Different European Locations

This article describes a simple model obtained from a commercial Stirling engine and used for heating a caravan. The Stirling engine has been tested in the lab under different electrical load conditions, and the operating points obtained are presented. As an application of the model, a series of transient simulations was performed using TRNSYS. During these simulations, the caravan is traveling throughout the day and is stationary at night. Therefore, during the night-time hours, the heating system is turned on by means of the Stirling engine. The study was performed for each month of the year in different European cities. The different heating demand profiles for different cities induce variation in the electricity production, as it has been assumed that electricity is only generated when the thermal demand requires the operation of the Stirling system. As a result, a comparison of the expected power generation in different European cities is presented.

Comparative Optimization on the Focusing Methods of Solar-Electric Dish Stirling System

Nowadays, the high-speed economic development has caused significant consumption of energy. While the circumstance is getting severer, solar energy is taken as a kind of clean, environmental friendly resource with infinite storage that has aroused a wide public concern. Photovoltaic and solar thermal are two main categories of solar applications. Because of its high conversion efficiency, low emission and flexible installation, dish Stirling solar power technology is more preferable to be used among the solar thermal area. From the view of practical engineering application, this paper illustrates multiple focusing methods of the current dish Stirling solar power systems in detail, and the comparison of these methods are given to analyze their advantages, disadvantages and their application scenarios. It can be used for the future development of dish Stirling solar power technology and applied as a reference for large dish solar thermal power plants’ installations and tests.

Environmental Profiles of Stirling-Cooled and Cascade-Cooled Ultra-Low Temperature Freezers

The environmental footprint of ultra-low temperature (ULT) freezers as used in bio-repositories, universities and other research organizations is investigated. These freezers, employing the cascade refrigeration system, use between 10 and 20 times the energy of an average household refrigerator/freezer. In addition, they often require high greenhouse gas potential (GWP) refrigerants. A new technology employing the Stirling cycle machine promises to reduce energy consumption of ULT freezers by 50% or more. The cascade and Stirling systems are compared for equivalent sized freezers in terms of embodied energy and equivalent CO2 production from cradle to gate and use, including total equivalent warming impact (TEWI) estimations. End-of-life issues are discussed but not quantified. It is shown that Stirling technology is able to significantly reduce the environmental impact of ULT freezers.

The place of solar power: an economic analysis of concentrated and distributed solar power

BackgroundThis paper examines the cost and benefits, both financial and environmental, of two leading forms of solar power generation, grid-tied photovoltaic cells and Dish Stirling Systems, using conventional carbon-based fuel as a benchmark.MethodsFirst we define how these solar technologies will be implemented and why. Then we delineate a model city and its characteristics, which will be used to test the two methods of solar-powered electric distribution. Then we set the constraining assumptions for each technology, which serve as parameters for our calculations. Finally, we calculate the present value of the total cost of conventional energy needed to power our model city and use this as a benchmark when analyzing both solar models’ benefits and costs.ResultsThe preeminent form of distributed electricity generation, grid-tied photovoltaic cells under net-metering, allow individual homeowners a degree of electric self-sufficiency while often turning a profit. However, substantial subsidies are required to make the investment sensible. Meanwhile, large dish Stirling engine installations have a significantly higher potential rate of return, but face a number of pragmatic limitations.ConclusionsThis paper concludes that both technologies are a sensible investment for consumers, but given that the dish Stirling consumer receives 6.37 dollars per watt while the home photovoltaic system consumer receives between 0.9 and 1.70 dollars per watt, the former appears to be a superior option. Despite the large investment, this paper deduces that it is far more feasible to get few strong investors to develop a solar farm of this magnitude, than to get 150,000 households to install photovoltaic arrays in their roofs. Potential implications of the solar farm construction include an environmental impact given the size of land require for this endeavour. However, the positive aspects, which include a large CO2 emission reduction aggregated over the lifespan of the farm, outweigh any minor concerns or potential externalities.

Using a group decision support system to add value to group model building

AbstractThis note intends to contribute to the practice of group model building by presenting group model‐building scripts that can (1) create a preliminary problem boundary using less than one hour of group time, (2) convene discussions with the group that explicitly link dynamic structure with system behaviour, and (3) allow participants to “zoom” between a micro and a macro view of system structure. These scripts may be used during early phases of problem structuring. They build on an extended program of inquiry dating back to the Stirling System Dynamics Conference of 1994, and they utilize a well‐established group decision support system to facilitate group discussion, negotiation, and decision. Copyright © 2010 John Wiley & Sons, Ltd.

Thermal analysis of Stirling engine solar driven

Solar energy is one of the more attractive renewable energy sources; the conversion of the latter per thermal way into electricity is a major energy stake. The current systems are primarily based on technology known as ‘solar dish/Stirling’, which uses Stirling engines placed at the focal plan of a parabolic concentrator. The Stirling engine presents an excellent theoretical output equivalent to the output of Carnot one. It is with external combustion, less pollutant, silencer and request little maintenance. Thanks to these advantages which the Stirling engine is very interesting to study. The dish Stirling system studies consist on three parts; the thermal modelling of Stirling engine, optical study of parabolic concentrator and finally the thermal study of the receiver. The present study is dedicated only to a thermal modelling of the Stirling engine based on the decoupled method. We evaluate, starting from an ideal adiabatic analysis, the thermal and mechanical powers exchanged, that we correct then by calculating the various losses within the machine. This model led to the writing of important set of equations algebra - differentials. The calculation programme worked out under Fortran to solve this system, makes allow to calculate the performances of any types of the Stirling engines, according to the kinematics used, the types of regenerators, the exchangers, as well as the various working liquids used.

Energy Performance of a New Stirling Micro Cogenerator

The simultaneous production of heat and power at a small-scale is already a well known technique. Cogeneration is one of the main ways to bring about decentralized, embedded, localized and/or autonomous power production. However, it is still a challenge to design cogenerators to be below 10 kW as required for the smallest applications such as providing heat and power to a single house (see Fig.1). This paper specifically introduces a Stirling micro-cogeneration system whose nominal power is 1 kW. The system connects a new “double-effect” Stirling engine with a linear induction generator. The connection is done via the engine’s piston that serves also as the secondary (mover) of the generator. First of all, the system is described, then, a state-space model of the co-generator under steady-state oscillatory conditions is presented in order to synthesize a controller that ensures robust stability and desired performances through the resistant effort created by the generator on the piston. Finally, an real rotating emulator is developed to study the energetic viability of the cogenerator.

Detailed Performance Analysis of a 10kW Dish∕Stirling System

The CNRS-Promes dish∕Stirling system was erected in Jun. 2004 as the last of three country reference units built in the “Envirodish” project. It represents the latest development step of the EuroDish system with many improved components. With a measured peak of 11kW electrical output power, it is also the best performing system so far. The measurement campaign to determine the optical and thermodynamic efficiency of the system is presented. The optical quality of the concentrator and the energy input to the power conversion unit was measured with a classical flux-mapping system using a Lambertian target and a charge coupled device camera system. An efficiency of the concentrator including the intercept losses of 74.4% could be defined for this particular system. For the thermodynamic analysis all the data necessary for a complete energy balance around the Stirling engine were measured or approximated by calculations. For the given ambient conditions during the tests, a Stirling engine efficiency of 39.4% could be measured. The overall efficiency for the conversion of solar to electric energy was 22.5%.

スターリングサイクルの双方向利用(スターリングエンジン及び関連要素と応用システム(2))

Stirling cycle is one of the machines which can convert power and thermal energy each other. Cogeneration system is a typical example of Stirling cycle as a bilateral application. Stirling system is used as a secondary machine. The system is driven as an engine with an exhaust gas of a primary engine. The same system is also driven as a heat pump. In this study, a bilateral Stirling system is examined both experimentally and analytically. The system performance is then presented. Finally, the expected performance is suggested.

Technical and economical evaluation of solar thermal power generation

This article presents a feasibilty on a solar power system based on the Stirling dish (SD) technology, reviews and compares the available Stirling engines in the perspective of a solar Stirling system. The system is evaluated, as a parameter to alleviate the energy system of the Cretan island while taking care of the CO 2 emissions. In the results a sensitivity analysis was implemented, as well as a comparison with conventional power systems. In the long-term, solar thermal power stations based on a SD can become a competitive option on the electricity market, if a concerted programme capable of building the forces of industry, finance, insurance and other decision makers will support the market extension for this promising technology.