scholarly journals Power-Optimized Sinusoidal Piston Motion and Its Performance Gain for an Alpha-Type Stirling Engine with Limited Regeneration

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4564 ◽  
Author(s):  
Mathias Scheunert ◽  
Robin Masser ◽  
Abdellah Khodja ◽  
Raphael Paul ◽  
Karsten Schwalbe ◽  
...  
Keyword(s):  
Power Output ◽  
Waste Heat ◽  
Primary Energy ◽  
Primary Energy Consumption ◽  
Performance Gain ◽  
Piston Motion ◽  
Stirling Engines ◽  
Remarkable Result ◽  
Performance Gains ◽  
Alpha Type

The recuperation of otherwise lost waste heat provides a formidable way to decrease the primary energy consumption of many technical systems. A possible route to achieve that goal is through the use of Stirling engines, which have shown to be reliable and efficient devices. One can increase their performance by optimizing the piston motion. Here, it is investigated to which extent the cycle averaged power output can be increased by using a special class of adjustable sinusoidal motions (the AS class). In particular the influence of the regeneration effectiveness on the piston motion is examined. It turns out that with the optimized piston motion one can achieve performance gains for the power output of up to 50% depending on the loss mechanisms involved. A remarkable result is that the power output does not depend strongly on the limitations of the regenerator, in fact—depending on the loss terms—the influence of the regenerator practically vanishes.

Reduction of Primary Energy Consumption Through Distributed Thermal Storage in Buildings Connected With a District Heating Network

2014 ◽  
Author(s):  
Giorgia Baccino ◽  
Sara Cosentino ◽  
Elisa Guelpa ◽  
Adriano Sciacovelli ◽  
Vittorio Verda
Keyword(s):  
Energy Consumption ◽  
Thermal Load ◽  
Waste Heat ◽  
Distributed Storage ◽  
Fluid Dynamic ◽  
District Heating ◽  
Thermal Storage ◽  
Primary Energy ◽  
Operating Conditions ◽  
Primary Energy Consumption

One of the possible options for increasing the primary energy efficiency in district heating networks (DHNs) consists in flattening the thermal load diagram of the plants. This can be obtained through thermal storage. Storage generally allows one to increase the percentage of heat produced through CHP plants, waste heat or renewable systems. In this work, a numerical approach to analyze possible effects of distributed storage on the primary energy consumption is presented. This is based on the availability of detailed information about the thermal substations that connect the users to the DHN and a thermo-fluid dynamic model of the network. First, the analysis of a user of the district heating network is proposed in order to show the operating conditions of the heat exchanger in the thermal substation. Then the model of the network is presented and an application is proposed. This application allows us to discuss how the thermal request of a user modifies along the network because of the heat capacity of the network itself and mixing with the mass flow rates at different temperatures. Therefore, the thermal load that the plants should fulfill is different than the simple summation of the thermal request of the users. This tool allows one to link the thermal thermal request of the users to the thermal load of the plant and thus to the global primary energy consumption. It can be then applied to the evaluation of possible variation of thermal request profile of the users.

Thermodynamic Analysis and Performance Investigation of an Alpha-Type Stirling Engine

2012 ◽  
Author(s):  
E. D. Rogdakis ◽  
I. P. Koronaki ◽  
G. D. Antonakos
Keyword(s):  
Thermodynamic Analysis ◽  
Power Output ◽  
System Performance ◽  
Engine Performance ◽  
Energy Systems ◽  
Stirling Engine ◽  
Operating Conditions ◽  
System Capacity ◽  
Stirling Engines ◽  
Alpha Type

The Stirling engine, as an external combustion engine, can be powered using a variety of heat sources including the continuous combustion process thus achieving significantly reduced emissions. Energy systems powered by a Stirling engines meet the needs of various applications not only in the domestic and industrial sections but in military and space gadgets as well. Stirling engines can also be used as cryocoolers in medical applications where they are called to achieve very low temperatures. Each energy system using Stirling Engine optimizes its performance in specific operating conditions. The system capacity depends on the geometric and structural characteristics, the design of the unit, the environment in which the engine is allowed to it works as well as the size of the load. In order to study the function and the efficiency of Stirling energy systems a CHP SOLO 161V -ALPHA TYPE STIRLING ENGINE was installed in the Laboratory of Applied Thermodynamics of NTUA. A thermodynamic analysis has been conducted using appropriate computing codes. The effect of each independent variable on the system performance was investigated. The study was divided into distinct levels of detail, bringing out each variable. Initially, the performance of the heat engine was examined assuming an ideal regenerator. Then, the effectiveness of the regenerator was evaluated as well as its effect on the engine performance, while the effect of the pressure drop and the energy dissipation on the engine efficiency was also investigated. Measurements were conducted using different operational conditions concerning the heating load of the engine. The effect of the geometrical characteristics of the regenerator on power output and engine performance was examined based on the results of a simulation analysis. Moreover, the power output and the efficiency of the machine in relation to the thermal load of the unit and the average pressure of the working medium were investigated. Major performance input characters affecting geometrical and operational parameters of the unit were identified leading to unit optimization with specific combinations leading to increased system performance. Simulation results were validated by comparison to corresponding values obtained by relative experiments conducted with the SOLO unit. Finally, a sensitivity analysis was performed in order to investigate the effect of the operating conditions on the performance of an alpha type Stirling Engine.

scholarly journals Stirling engines - the state of technology development and computational models

2021 ◽  
Author(s):  
Mariusz Furmanek ◽  
Jacek Kropiwnicki
Keyword(s):  
Power Systems ◽  
Computational Models ◽  
Waste Heat ◽  
Numerical Models ◽  
Renewable Energy Sources ◽  
Primary Energy ◽  
Stirling Engine ◽  
Correct Selection ◽  
Engine Operation ◽  
Stirling Engines

Stirling engines represent a technologically important solution in combined heat and power systems. Their use enables the achievement of over 90 percent efficiency in the management of the primary energy source with a very high durability of the device, mainly due to the lack of contact of the working gas with external factors and a very small number of mechanical components. The use of a Stirling engine may be equally important when applying renewable energy sources or waste heat from other processes. The first part of the work presents an overview of available commercial Stirling engine solutions. The second part of the work presents an overview of numerical models of Stirling engine operation, which enable the correct selection of the main geometrical features of the devices and the improvement of the structure in order to maximize efficiency or power.

Optimization of the Thermal Request Profiles of Buildings Connected With a Large District Heating Network

2016 ◽  
Author(s):  
Vittorio Verda ◽  
Elisa Guelpa ◽  
Giulia Barbero ◽  
Francesco Brundu ◽  
Andrea Acquaviva ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Waste Heat ◽  
Central Area ◽  
District Heating ◽  
Thermal Storage ◽  
Primary Energy ◽  
Physical Models ◽  
Primary Energy Consumption ◽  
Peak Shaving ◽  
Start Up

Thermal storage is very important in modern district heating networks in order to increase the share of waste heat and heat produced through renewable sources and cogeneration. The role of thermal storage is even more important in the case of Mediterranean areas, where climate and user behavior cause high peak requests in the morning. Nevertheless the installation of large storage volumes is not always feasible, especially in dense urban areas, therefore alternative options are investigated. One of these options is virtual storage. This consists in proposing changes to the thermal request profiles of some of the connected buildings, in order to obtain a peak shaving, which is an effect similar to that obtained using storage. To perform such approach there are two crucial elements: 1) an advanced ICT solution able provide real time information about the thermal request of the buildings and the thermodynamic conditions at the thermal substations; 2) a detailed thermo fluid-dynamic model of the district heating network able to simulate the temperature evolution along the network as the function of time. Using physical models it is possible to examine the effects, obtained by modifying the thermal request of users, on the total load of the thermal plants feeding the network. In particular, the model is applied to the analysis of changes in the start-up time of the buildings as well as possible pauses during the day. The start-up strategy should not produce significant effects on the building temperatures, so that acceptable comfort standard can be guaranteed. This is checked using a compact model of the buildings which parameters are obtained through data measured at the thermal substations. These changes in the request profiles usually involve a larger heat request. Nevertheless, peak shaving is accompanied by a reduction in heat generation of boilers and an increase in the thermal production of efficient systems, such as cogeneration units. This results in a significant reduction in the primary energy consumption. The goal of the analysis is to find the optimal start-up strategy in order to minimize the primary energy consumption at the thermal plants. An application to the Turin district heating network, which is the largest network in Italy, is presented. In particular, a subnetwork connecting the main transport network to about 100 buildings located in the central area of the town is considered. The analysis if performed in selected days where the optimization was conducted the day before on the basis of weather forecasts and then applied to the network. Despite the changes in the request profiles could be applied only to a limited number of buildings, the analysis show that the peak request can be reduced. Simulations performed considering the application of changes to a larger number of buildings show that reduction in the primary energy consumptions of the order of 1.25% can be obtained.

scholarly journals Experimental evaluation of piston motion modification to improve the thermodynamic power output of a low temperature gamma Stirling engine

2021 ◽  
Vol 313 ◽  
pp. 04002
Author(s):  
Michael Nicol-Seto ◽  
David Nobes
Keyword(s):  
Low Temperature ◽  
Power Output ◽  
Stirling Engine ◽  
Maximum Power ◽  
Piston Motion ◽  
Heat Engines ◽  
Stirling Engines ◽  
Thermodynamic Performance ◽  
Engine Power ◽  
The Ideal

Stirling engines are a variety of heat engines which are capable of using heat from various sources including low temperature renewables. This work examines performance of a lab scale low temperature gamma type Stirling engine with a drive train modified with oval elliptical gears. The gears were added to dwell the engine piston motion to attempt to improve the thermodynamic performance of the engine by better replicating the ideal Stirling cycle. A variety of dwelling piston configurations were tested on both the displacer and power piston. It was observed that that the piston dwelling had the anticipated effect of changing the engine indicator diagrams to more closely resemble the ideal cycle, however there were no substantial improvements to maximum engine power. It was observed that dwelling the displacer piston caused substantial reductions to engine running speeds and resulted in maximum power being reduced. In the case of power piston dwelling the indicator diagram was enlarged and there were slight increases to maximum power production. Overall the added complexity of dwelled piston motion systems is not likely an advantageous method of increasing the power output of low temperature difference Stirling engines.

scholarly journals Investigation of effect of heat exchanger size on power output in low-temperature difference Stirling engines

2021 ◽  
Vol 313 ◽  
pp. 03002
Author(s):  
Linda Hasanovich ◽  
David Nobes
Keyword(s):  
Heat Exchanger ◽  
Low Temperature ◽  
Power Output ◽  
Heat Exchangers ◽  
Waste Heat ◽  
Significant Loss ◽  
Stirling Engine ◽  
Dead Volume ◽  
Optimal Geometry ◽  
Stirling Engines

The Stirling engine is capable of converting any source of thermal energy into kinetic energy, which makes it an attractive option for utilizing low-temperature sources such as geothermal or waste heat below 100 °C. However, at these low temperatures, the effects of losses are proportionally higher due to the lower thermal potential available. One such significant loss is excess dead volume, wherein a significant contributor is the heat exchangers. The heat exchangers must be selected to optimize power output by minimizing the dead volume loss while maximizing the heat transfer to and from the engine. To better understand what the optimal geometry of the heat exchanger components is, a Stirling engine is modelled using a third-order commercial modelling software (Sage) and trends of engine properties of power, temperature, and pressure for different heat exchanger geometries are observed. The results indicate that there is an optimum heat exchanger volume and geometry for low temperature Stirling engines. This optimum is also affected by other engine properties, such as regenerator size and engine speed. These results provide insight into the optimal geometry of these components for low-temperature Stirling engines, as well as providing design guidance for future engines to be built.

scholarly journals Optimized Piston Motion for an Alpha-Type Stirling Engine

Entropy ◽  
2020 ◽  
Vol 22 (6) ◽  
pp. 700 ◽  
Author(s):  
Robin Masser ◽  
Abdellah Khodja ◽  
Mathias Scheunert ◽  
Karsten Schwalbe ◽  
Andreas Fischer ◽  
...  
Keyword(s):  
Waste Heat ◽  
Stirling Engine ◽  
Piston Motion ◽  
Performance Improvements ◽  
Engine Model ◽  
Wide Range ◽  
The Individual ◽  
Parameter Values ◽  
The Impact ◽  
Alpha Type

The Stirling engine is one of the most promising devices for the recovery of waste heat. Its power output can be optimized by several means, in particular by an optimized piston motion. Here, we investigate its potential performance improvements in the presence of dissipative processes. In order to ensure the possibility of a technical implementation and the simplicity of the optimization, we restrict the possible piston movements to a parametrized class of smooth piston motions. In this theoretical study the engine model is based on endoreversible thermodynamics, which allows us to incorporate non-equilibrium heat and mass transfer as well as the friction of the piston motion. The regenerator of the Stirling engine is modeled as ideal. An investigation of the impact of the individual loss mechanisms on the resulting optimized motion is carried out for a wide range of parameter values. We find that an optimization within our restricted piston motion class leads to a power gain of about 50% on average.

scholarly journals Cooling Cycle Optimization for a Vuilleumier Refrigerator

Entropy ◽  
2021 ◽  
Vol 23 (12) ◽  
pp. 1562
Author(s):  
Raphael Paul ◽  
Abdellah Khodja ◽  
Andreas Fischer ◽  
Karl Heinz Hoffmann
Keyword(s):  
Quantitative Estimate ◽  
Waste Heat ◽  
Thermodynamic Cycle ◽  
Cooling Power ◽  
Driving Mechanism ◽  
Power Gain ◽  
Piston Motion ◽  
External Energy ◽  
Stirling Engines ◽  
Hot Bath

Vuilleumier refrigerators are a special type of heat-driven cooling machines. Essentially, they operate by using heat from a hot bath to pump heat from a cold bath to an environment at intermediate temperatures. In addition, some external energy in the form of electricity can be used as an auxiliary driving mechanism. Such refrigerators are, for example, advantageous in situations where waste heat is available and cooling power is needed. Here, the question of how the performance of Vuilleumier refrigerators can be improved is addressed with a particular focus on the piston motion and thus the thermodynamic cycle of the refrigerator. In order to obtain a quantitative estimate of the possible cooling power gain, a special class of piston movements (the AS motion class explained below) is used, which was already used successfully in the context of Stirling engines. We find improvements of the cooling power of more than 15%.

On Energy Status indicators and the role of renewableEnergy under Economic Crisis

2014 ◽  
pp. 92-105
Author(s):  
P. Bezrukikh ◽  
P. Bezrukikh (Jr.)
Keyword(s):  
Renewable Energy ◽  
World Economy ◽  
Electrical Energy ◽  
Primary Energy ◽  
Primary Energy Consumption ◽  
Energy Status ◽  
Economy Growth ◽  
The World ◽  
Production Regime

The article analyzes the dynamics of consumption of primary energy and production of electrical energy in the world for 1973-2012 and the volume of renewable energy. It is shown that in the crisis year of 20 0 9 there was a significant reduction in primary energy consumption and production of electrical energy. At the same time, renewable energy has developed rapidly, well above the rate of the world economy growth. The development of renewable energy is one of the most effective ways out of the crisis, taking into account its production regime, energy, environmental, social and economic efficiency. The forecast for the development of renewable energy for the period up to 2020, compiled by the IEA, is analyzed. It is shown that its assessment rates are conservative; the authors justify higher rates of development of renewable energy.

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