Modeling a Stirling Engine for Cogeneration Applications

2012 ◽  
Author(s):  
Ana C. Ferreira ◽  
Senhorinha Teixeira ◽  
José C. Teixeira ◽  
Manuel L. Nunes ◽  
Luís B. Martins
Keyword(s):  
Power Generation ◽  
Power Systems ◽  
Carbon Dioxide Emissions ◽  
Internal Combustion Engines ◽  
Market Competition ◽  
Good Alternative ◽  
Low Noise ◽  
Total Efficiency ◽  
Partial Load ◽  
Stirling Engines

The interest on decentralized power generation technology has been drastically increasing over the last few years. This great interest is due to the necessity of achieving new ways for improving energy efficiency, the national security of energy supply and the reduction of carbon dioxide emissions. Combined heat and power generation (CHP) systems can be a good option to achieve those goals. In Europe and for the building sector, this fact can be translated in the development of low power systems (micro-CHP), designed to fulfill building equivalent loads. These systems will replace the usual boilers that satisfy the dwelling’s heat requirements and, additionally, generate electricity for own consumption or export back to the electricity grid. The most cited technologies in small and micro-scale are Fuel Cells, Internal Combustion Engines, and Stirling Engines. Stirling Engines are gaining some attention due to their advantages: high total efficiency, fuel flexibility, low emissions, low noise/vibration levels and good performance at partial load. Due to these characteristics, Stirling engines seem to be a good alternative for residential energy conversion, and thus, a pathway for more energy-efficient systems that rise to the challenges of increasing market competition. Many studies have been conducted in order to assess Stirling Engines performance, but the integration of technical and economic evaluation for micro-CHP systems applications is an issue that is not focused in literature, and is the final objective of this project.

scholarly journals Improvements of Micro-CHP SOFC System Operation by Efficient Dynamic Simulation Methods

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1113
Author(s):  
Laura Nousch ◽  
Mathias Hartmann ◽  
Alexander Michaelis
Keyword(s):  
Power Generation ◽  
Power Systems ◽  
System Modeling ◽  
Power Input ◽  
Experimental Investigations ◽  
System Operation ◽  
Modeling Tools ◽  
Decentralized Generation ◽  
Partial Load ◽  
Battery Capacity

Solid Oxide Fuel Cell (SOFC) technology is of high interest for stationary decentralized generation of electricity and heat in combined heat and power systems (CHP) for the residential sector. Application scenarios for SOFC systems in an electricity-regulated mode play an important role, especially in places where an electrical grid connection is not available or rather unstable. The advantages of SOFC systems are the high fuel flexibility and the high efficiencies also under partial load operation compared to other decentralized power generation technologies. Due to the long, energy-consuming system heat-up and the limited partial load capability, SOFC systems do not reach the performance of conventional power generation technologies. Furthermore, stack thermal cycling is associated with power degradation and should be minimized. In this paper, the improvement of these drawbacks are investigated for hotbox-based SOFC systems in the 1 kWel-class for residential applications. Since experimental investigations of the high-temperature systems are limited, modeling tools are established, enabling the visualization of internal system characteristics and providing the opportunity to simulate system operation in critical regions. To achieve this, a methodology for dynamic SOFC system modeling in a process engineering manner is developed based on the modeling language Modelica. A suitable approach is particularly important for modeling and simulation of the strong thermal interaction between the hot system components within the hotbox. The parametrized and validated models are used for the investigation of different dynamic effects, such as the system heat-up and the operation in low partial load points. A second reduced thermal system model aims for annual simulations of the SOFC system together with a battery to investigate the number of thermal cycles and the advantage of a hot standby operation. As a result, it is found that an adequate control of the power input at the start-up device and the cathode air flow has a high improvement potential to increase the stack heating rate and accelerate the heat-up in an energy-saving way. The hotbox-internal thermal management is identified as a crucial issue to reach low partial load points. To avoid the risk of stack cooling, lower heat losses and/or additional heat sources are of importance. Furthermore, the robustness of the tail gas oxidizer is found to be crucial for a higher load flexibility during partial load and the end of life stack operation. The annual simulation results indicate that operating the battery hybrid system with a hot standby mode requires much lower battery capacity for a high grid independence and a complete avoidance of system shutdown and associated power degradation.

scholarly journals Analysis of electric motor vehicles market

2019 ◽  
Vol 179 (4) ◽  
pp. 169-175
Author(s):  
Marta MACIEJEWSKA ◽  
Paweł FUĆ ◽  
Monika KARDACH
Keyword(s):  
Electric Vehicle ◽  
Electric Vehicles ◽  
Carbon Dioxide Emissions ◽  
Internal Combustion Engines ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Low Noise ◽  
Motor Vehicles ◽  
Combustion Engines ◽  
The European Union

The increasingly restrictive standards related to exhaust emissions from cars make difficult the development of internal combustion engines. The activities undertaken in the design of internal combustion engines are mainly based on downsizing, e.g decreasing the engines displacement. The main direction in the development of vehicle propulsion is to reduce carbon dioxide emissions. It is expected to reduce CO2 emissions in 2020 to reach 95 g/km. Electric vehicles achieve low noise levels and do not emitted a burn, and thus, their use leads to a reduction in the amount of toxic exhaust gases in the air. The aspect of reducing emissions of harmful exhaust compounds and activities focusing on downsizing on the market of combustion engine cars leads to a significant increase the number of electric vehicles. In 2018 around 95 million motor vehicles were registered in the world, of which around 12 million in the European Union and 273 thousand in Poland. The number of electric vehicles among all sold is around 5.5%. Every year new, more technologically advanced models appear on the electric vehicle market. In 2018, the most popular model was the Nissan LEAF and the BAIC EC-Series. A large number of Renault ZOE have also been sold. In article analyzed different models of electric vehicle, which are available on market and presented the characteristics based on e.g. price per 100 kilometers, range for every model or charging time.

Numerical Study of Regenerator Configuration in the Design of a Stirling Engine

2014 ◽  
Author(s):  
Ana C. Ferreira ◽  
Senhorinha Teixeira ◽  
Manuel L. Nunes ◽  
Luís B. Martins
Keyword(s):  
Power Systems ◽  
Energy Conversion ◽  
Numerical Study ◽  
Renewable Energy Sources ◽  
Thermodynamic Cycle ◽  
Good Alternative ◽  
Stirling Engine ◽  
Micro Scale ◽  
Point Of Use ◽  
Stirling Engines

The sustainable development involves the rational use of energy, by satisfying energy demands without compromising the safety of future supply. The use of renewable energy sources together with combined heat and power systems is currently considered a priority in Europe. The market trends are evolving to decentralized energy conversion with the increasing replacement of boilers and other conventional systems by small and micro-scale cogeneration units, able to produce the same amounts of useful energies. Micro scale cogeneration systems have been developed as ideal solutions to meet the energy needs for the building sector. These technologies, which include the Stirling engines, allow the production of high quality electricity and heat, efficiently and close to the final point of use. Stirling engines seem to be a good alternative for residential energy conversion. The main objective of this paper is to study alternative configurations for the regenerator of an alpha Stirling engine and evaluate the overall performance of the system. Numerical simulations were performed via a MatLab® code that includes the thermodynamic cycle analysis accounting for the effects of non-ideal heat exchangers and pumping losses. Based on a previously developed costing methodology, the investment purchase cost for each configuration is also estimated. Results showed that, for mean pressure values above 30 bar, the Stirling engine efficiency is higher for a regenerator with a wired mesh matrix rather than with a wrapped foil matrix. This is due both to better heat transfer and to lower pumping losses with the wired mesh configuration. The capital cost of the system was calculated and showed that the heater and the engine bulk are the most expensive components.

scholarly journals Design and Research on Power Systems and Algorithms for Controlling Electric Underground Mining Machines Powered by Batteries

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 4060
Author(s):  
Artur Kozłowski ◽  
Łukasz Bołoz
Keyword(s):  
Power Systems ◽  
Power Supply ◽  
Internal Combustion Engines ◽  
Underground Mining ◽  
Test Stand ◽  
Research Network ◽  
Control Algorithms ◽  
Systems And Control ◽  
And Control ◽  
Supply Systems

This article discusses the work that resulted in the development of two battery-powered self-propelled electric mining machines intended for operation in the conditions of a Polish copper ore mine. Currently, the global mining industry is seeing a growing interest in battery-powered electric machines, which are replacing solutions powered by internal combustion engines. The cooperation of Mine Master, Łukasiewicz Research Network—Institute of Innovative Technologies EMAG and AGH University of Science and Technology allowed carrying out a number of works that resulted in the production of two completely new machines. In order to develop the requirements and assumptions for the designed battery-powered propulsion systems, underground tests of the existing combustion machines were carried out. Based on the results of these tests, power supply systems and control algorithms were developed and verified in a virtual environment. Next, a laboratory test stand for validating power supply systems and control algorithms was developed and constructed. The tests were aimed at checking all possible situations in which the battery gets discharged as a result of the machine’s ride or operation and when it is charged from the mine’s mains or with energy recovered during braking. Simulations of undesirable situations, such as fluctuations in the supply voltage or charging power limitation, were also carried out at the test stand. Positive test results were obtained. Finally, the power supply systems along with control algorithms were implemented and tested in the produced battery-powered machines during operational trials. The power systems and control algorithms are universal enough to be implemented in two different types of machines. Both machines were specially designed to substitute diesel machines in the conditions of a Polish ore mine. They are the lowest underground battery-powered drilling and bolting rigs with onboard chargers. The machines can also be charged by external fast battery chargers.

scholarly journals Life Cycle Energy Consumption and Carbon Dioxide Emissions of Agricultural Residue Feedstock for Bioenergy

2021 ◽  
Vol 11 (5) ◽  
pp. 2009
Author(s):  
Valerii Havrysh ◽  
Antonina Kalinichenko ◽  
Anna Brzozowska ◽  
Jan Stebila
Keyword(s):  
Carbon Dioxide ◽  
Power Generation ◽  
Life Cycle ◽  
Carbon Dioxide Emissions ◽  
Crop Production ◽  
Agricultural Residues ◽  
Environmental Indicators ◽  
Low Carbon ◽  
Low Carbon Economy ◽  
Energy Inputs

The depletion of fossil fuels and climate change concerns are drivers for the development and expansion of bioenergy. Promoting biomass is vital to move civilization toward a low-carbon economy. To meet European Union targets, it is required to increase the use of agricultural residues (including straw) for power generation. Using agricultural residues without accounting for their energy consumed and carbon dioxide emissions distorts the energy and environmental balance, and their analysis is the purpose of this study. In this paper, a life cycle analysis method is applied. The allocation of carbon dioxide emissions and energy inputs in the crop production by allocating between a product (grain) and a byproduct (straw) is modeled. Selected crop yield and the residue-to-crop ratio impact on the above indicators are investigated. We reveal that straw formation can consume between 30% and 70% of the total energy inputs and, therefore, emits relative carbon dioxide emissions. For cereal crops, this energy can be up to 40% of the lower heating value of straw. Energy and environmental indicators of a straw return-to-field technology and straw power generation systems are examined.

Trade-Off Design Analysis of Operating Pressure and Temperature in PEM Fuel Cell Systems

1999 ◽  
Author(s):  
Frano Barbir ◽  
Bhaskar Balasubramanian ◽  
Jay Neutzler
Keyword(s):  
Fuel Cell ◽  
Cell Polarization ◽  
Propulsion System ◽  
Automotive Application ◽  
Total Efficiency ◽  
Operating Voltage ◽  
Operating Pressure ◽  
Surprising Result ◽  
Partial Load ◽  
Full Power

Abstract The paper presents the results of an optimization study of an automotive fuel cell propulsion system equipped with a fuel reformer. Based on a set of fuel cell polarization curves determined experimentally by running a prototype fuel cell stack at a variety of operating pressures and temperatures, a numerical steady state model was used to determine the optimal operating pressure and temperature. The optimization criteria were the size of individual components and the entire propulsion system as well as its total efficiency at both full power and partial load. The results suggested that an automotive system should be operated at relatively high pressure (308 kPa), but an expander must be used to recover most of the power used for compression. A surprising result of this analysis is that a relatively low temperature (∼60°C) results in smallest heat rejection equipment if neutral water balance is mandated. The efficiency of the system is about 33% at full power and about 38% at 25% of the load. Higher efficiencies may be achieved by selecting a higher fuel cell operating voltage, but that would result in larger fuel cell stacks, which may be a limiting factor for automotive application with the state-of-the-art fuel cells.

Three Spool High Efficiency Small Scale Gas Turbine Concept

2017 ◽  
Author(s):  
Matti Malkamäki ◽  
Ahti Jaatinen-Värri ◽  
Antti Uusitalo ◽  
Aki Grönman ◽  
Juha Honkatukia ◽  
...  
Keyword(s):  
Power Generation ◽  
Gas Turbine ◽  
Gas Turbines ◽  
High Efficiency ◽  
Small Scale ◽  
Inlet Temperature ◽  
Substantial Impact ◽  
Electrical Efficiency ◽  
Partial Load ◽  
Reciprocating Engines

Decentralized electricity and heat production is a rising trend in small-scale industry. There is a tendency towards more distributed power generation. The decentralized power generation is also pushed forward by the policymakers. Reciprocating engines and gas turbines have an essential role in the global decentralized energy markets and improvements in their electrical efficiency have a substantial impact from the environmental and economic viewpoints. This paper introduces an intercooled and recuperated three stage, three-shaft gas turbine concept in 850 kW electric output range. The gas turbine is optimized for a realistic combination of the turbomachinery efficiencies, the turbine inlet temperature, the compressor specific speeds, the recuperation rate and the pressure ratio. The new gas turbine design is a natural development of the earlier two-spool gas turbine construction and it competes with the efficiencies achieved both with similar size reciprocating engines and large industrial gas turbines used in heat and power generation all over the world and manufactured in large production series. This paper presents a small-scale gas turbine process, which has a simulated electrical efficiency of 48% as well as thermal efficiency of 51% and can compete with reciprocating engines in terms of electrical efficiency at nominal and partial load conditions.

A Modified Master Cycle Off-Design Performance and Heat Rate Improvement Optimization

2017 ◽  
Author(s):  
Chenghao Fan ◽  
Dongsheng Pei ◽  
Xiang He ◽  
Wentai Zhou ◽  
Zengtao Wei
Keyword(s):  
Power Generation ◽  
Thermodynamic Simulation ◽  
Heat Rate ◽  
Feed Water ◽  
Partial Load ◽  
Current Cycle ◽  
Rate Improvement ◽  
Pressure Extraction ◽  
Rate Optimization ◽  
Future Work

Coal-fired power generation will continue to be the cornerstone of China’s energy sources in the coming decades and advanced ultra-supercritical technology is the future of coal-fired power generation. This paper selects double reheat cycle design for study and incorporates back pressure extraction steam turbine (BEST) into current cycle design, which used to drive boiler feed water pump and feed regenerative heaters. This design prevailed in US in 1960s and gradually was replaced by condensing turbine due to less efficiency benefits at subcritical steam condition. Reinvention of BEST design in current double reheat cycle is an evitable choice, because the efficiency advantage is improved at USC steam condition. BEST configuration incorporated into current double reheat cycle and advanced cycle is developed to compare with other two conventional systems in this study. Thermodynamic simulation at design and off-design condition shows that BEST configuration has an obvious efficiency advantage at design load, but the advantage decreases at partial load. BEST expansion line and reheat pressure is integrated in cycle heat rate optimization. Genetic algorithm is chosen to implement the optimization and exergy analysis method is utilized to evaluate BEST expansion line optimization results. Finally, BEST design limitation and future work is practically concluded.

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