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Luís A.S.B. Martins
Department of Mechanical Engineering - University of Minho

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Conference paper
Published: 30 September 2020 in Transactions on Petri Nets and Other Models of Concurrency XV
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Currently, the energy consumption study in buildings is very important, since it is one of the sectors of activity where there is great potential to improve energy efficiency. On the market, there are several simulation software, and the aim of this work consists in conducting a comparison between two dynamic simulation software, EnergyPlus, and Revit, with respect to the results obtained of thermal loads and annual energy consumption of a service building. In the simulation using EnergyPlus, an annual energy consumption of 442 MWh was obtained, that compares with 533 MWh when using Revit. Concerning the thermal loads in the sales area of the hypermarket, the simulation results for the thermal loads were the following: 761 kW for heating and 79 kW for cooling, versus 924 kW for heating and 86 kW for cooling when using the EnergyPlus and the Revit software, respectively. This discrepancy between the values obtained could be due to the limited selection of climatic files in Revit as well as the different definitions of the HVAC systems.

ACS Style

João Silva; José Brás; Ricardo Noversa; Nelson Rodrigues; Luís Martins; José Teixeira; Senhorinha Teixeira. Energy Performance of a Service Building: Comparison Between EnergyPlus and Revit. Transactions on Petri Nets and Other Models of Concurrency XV 2020, 12254, 201 -213.

AMA Style

João Silva, José Brás, Ricardo Noversa, Nelson Rodrigues, Luís Martins, José Teixeira, Senhorinha Teixeira. Energy Performance of a Service Building: Comparison Between EnergyPlus and Revit. Transactions on Petri Nets and Other Models of Concurrency XV. 2020; 12254 ():201-213.

Chicago/Turabian Style

João Silva; José Brás; Ricardo Noversa; Nelson Rodrigues; Luís Martins; José Teixeira; Senhorinha Teixeira. 2020. "Energy Performance of a Service Building: Comparison Between EnergyPlus and Revit." Transactions on Petri Nets and Other Models of Concurrency XV 12254, no. : 201-213.

Conference paper
Published: 30 September 2020 in Transactions on Petri Nets and Other Models of Concurrency XV
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This work seeks to analyze the thermal comfort of the occupants in a large building of Commerce and Services, integrating measures of assessment and energy efficiency promotion. The building is still in the construction phase and at its conclusion, will correspond to a supermarket located in the Central region of Portugal. For the evaluation of thermal comfort, Fanger’s methodology was used, where the Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) were calculated based on a detailed analysis of the environmental variables. These are essential to obtain, namely, mean air velocity, mean radiant temperature, mean air temperature and relative humidity. The other crucial variables are the metabolic rate and the thermal clothing resistance. The simulations necessary for the thermal comfort assessment were performed in ANSYS Fluent, in order to minimize the energy consumption in the cold thermal zone of the building, the sales area with frozen and chilled food, by means of reducing the inflow of air, without compromising thermal Comfort. The final results showed that the reduction of the amount of air to be inflated did not compromise the thermal comfort of the occupants. The Computational Fluid Dynamics (CFD) methodology allowed the creation of comfort maps, albeit for a single zone due to computational limitations. According to the results, the most comfortable zone was located right below the air insufflation with the summer being a more comfortable season. In winter, the main problem detected was the cold located near the floor.

ACS Style

Ricardo Noversa; João Silva; Nelson Rodrigues; Luís Martins; José Teixeira; Senhorinha Teixeira. Thermal Simulation of a Supermarket Cold Zone with Integrated Assessment of Human Thermal Comfort. Transactions on Petri Nets and Other Models of Concurrency XV 2020, 12254, 214 -227.

AMA Style

Ricardo Noversa, João Silva, Nelson Rodrigues, Luís Martins, José Teixeira, Senhorinha Teixeira. Thermal Simulation of a Supermarket Cold Zone with Integrated Assessment of Human Thermal Comfort. Transactions on Petri Nets and Other Models of Concurrency XV. 2020; 12254 ():214-227.

Chicago/Turabian Style

Ricardo Noversa; João Silva; Nelson Rodrigues; Luís Martins; José Teixeira; Senhorinha Teixeira. 2020. "Thermal Simulation of a Supermarket Cold Zone with Integrated Assessment of Human Thermal Comfort." Transactions on Petri Nets and Other Models of Concurrency XV 12254, no. : 214-227.

Journal article
Published: 16 January 2020 in Energies
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A range extender (RE) is a device used in electric vehicles (EVs) to generate electricity on-board, enabling them to significantly reduce the number of required batteries and/or extend the vehicle driving range to allow occasional long trips. In the present work, an efficiency-oriented RE based on a small motorcycle engine modified to the efficient over-expanded cycle, was analyzed, tested and simulated in a driving cycle. The RE was developed to have two points of operation, ECO: 3000 rpm, very high efficiency with only 15 kW; and BOOST: 7000 rpm with 35 kW. While the ECO strategy was a straightforward development for the over-expansion concept (less trapped air and a much higher compression ratio) the BOOST strategy was more complicated to implement and involved the need for throttle operation. Initially the concepts were evaluated in an in-house model and AVL Boost® (AVL List Gmbh, Graz, Austria), and proved feasible. Then, a BMW K75 engine was altered and tested on a brake dynamometer. The running engine proved the initial concept, by improving the efficiency for the ECO condition in almost 40% in relation to the stock engine and getting well over the required BOOST power, getting to 35 kW, while keeping an efficiency similar to the stock engine at the wide open throttle (WOT). In order to protect the engine during BOOST, the mixture was enriched, while at ECO the mixture was leaned to further improve efficiency. The fixed operation configuration allows the reduction, not only of complexity and cost of the RE, but also the set point optimization for the engine and generator. When integrated as a RE into a typical European light duty vehicle, it provided a breakthrough consumption reduction relatively to existing plug-in hybrid electric vehicles (PHEVs) in the market in the charge sustaining mode. The very high efficiency of the power generation seems to compensate for the loss of efficiency due to the excess electricity production, which must be stored in the battery. The results indicate that indeed it is possible to have an efficient solution, in-line with the electric mobility sustainability paradigm, which can solve most of the shortcomings of current EVs, notably those associated with batteries (range, cost and charging time) in a sustainable way.

ACS Style

F. P. Brito; Jorge Martins; Francisco Lopes; Carlos Castro; Luís Martins; A. L. N. Moreira. Development and Assessment of an Over-Expanded Engine to be Used as an Efficiency-Oriented Range Extender for Electric Vehicles. Energies 2020, 13, 430 .

AMA Style

F. P. Brito, Jorge Martins, Francisco Lopes, Carlos Castro, Luís Martins, A. L. N. Moreira. Development and Assessment of an Over-Expanded Engine to be Used as an Efficiency-Oriented Range Extender for Electric Vehicles. Energies. 2020; 13 (2):430.

Chicago/Turabian Style

F. P. Brito; Jorge Martins; Francisco Lopes; Carlos Castro; Luís Martins; A. L. N. Moreira. 2020. "Development and Assessment of an Over-Expanded Engine to be Used as an Efficiency-Oriented Range Extender for Electric Vehicles." Energies 13, no. 2: 430.

Conference paper
Published: 29 June 2019 in Transactions on Petri Nets and Other Models of Concurrency XV
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This work aims to simulate the thermal comfort for the user of a movie theater in the dimension related to considering the thermal environment parameters by the using EnergyPlus software. The results from simulation are then compared with the experimental ones. In order to calculate and model the thermal comfort, it was necessary a proper characterization of the space that included the measured occupancy, thermal environment variables, distinct electric equipment and lights. To compute the Predicted Mean Vote (PMV) and the Predictable Percentage of Dissatisfied (PPD) in EnergyPlus, the metabolic rate, air velocity and clothing insulation were defined according to the cinema specifications. The results obtained from EnergyPlus were then compared with the experimentally measured ones. Minor differences were observed regarding the comfort sensation. Despite the differences, the variation in the percentage of dissatisfied people is smaller than 2%. Furthermore, this work also allowed verifying that the occupancy rate is a determining factor in the thermal comfort sensation and, in this case, people provided the necessary energy to heat the cinema room in the second session that occurred at night.

ACS Style

Diogo Esteves; João Silva; Nelson Rodrigues; Luís Martins; José Teixeira; Senhorinha Teixeira. Simulation of PMV and PPD Thermal Comfort Using EnergyPlus. Transactions on Petri Nets and Other Models of Concurrency XV 2019, 52 -65.

AMA Style

Diogo Esteves, João Silva, Nelson Rodrigues, Luís Martins, José Teixeira, Senhorinha Teixeira. Simulation of PMV and PPD Thermal Comfort Using EnergyPlus. Transactions on Petri Nets and Other Models of Concurrency XV. 2019; ():52-65.

Chicago/Turabian Style

Diogo Esteves; João Silva; Nelson Rodrigues; Luís Martins; José Teixeira; Senhorinha Teixeira. 2019. "Simulation of PMV and PPD Thermal Comfort Using EnergyPlus." Transactions on Petri Nets and Other Models of Concurrency XV , no. : 52-65.

Proceedings article
Published: 03 November 2017 in Volume 4A: Dynamics, Vibration, and Control
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Stirling engines efficiency, the increased maintenance interval periods, the variety of energy sources and the relatively low gas emissions makes Stirling technology an interesting choice as prime mover for cogeneration applications. These are some of the reasons that justify the attention received from researchers in the last years, focused in its modelling, optimization and its application in the suppression of buildings energy needs. In this study, an alpha-Stirling engine was numerically modelled. At this configuration, the working fluid flows between expansion and compression spaces by alternate crossing of, a high temperature heat exchanger (heater), a regenerator and a low temperature heat exchanger (cooler). Thus, the engine is considered as a set of five components connected in series. MatLab® environment was used to implement a software-code to model the thermodynamic cycle of the Stirling engine. The modular code allows investigating the influence of different geometrical and thermal parameters of all the engine components that affects its power production and the efficiency, the effectiveness of heat exchangers and the design itself of the power plant. This parametric analysis helps finding some restriction values for geometrical parameters that cannot be solved through the optimization procedures. For instance, at some point, there is a geometrical limit for which the increase in heat transfer is overlapped by the void volume or pumping losses increase. The parametric analysis led to an enhanced configuration of the numerical model, which resulted in the increase of engine thermal efficiency (about 13.4%), with a power production close to 5 kW.

ACS Style

Ana Cristina Ferreira; Senhorinha F. C. F. Teixeira; Jose Teixeira; Luis Martins. Parametric Analysis of the Thermal Components of an Alpha-Stirling Engine for Cogeneration Applications. Volume 4A: Dynamics, Vibration, and Control 2017, 1 .

AMA Style

Ana Cristina Ferreira, Senhorinha F. C. F. Teixeira, Jose Teixeira, Luis Martins. Parametric Analysis of the Thermal Components of an Alpha-Stirling Engine for Cogeneration Applications. Volume 4A: Dynamics, Vibration, and Control. 2017; ():1.

Chicago/Turabian Style

Ana Cristina Ferreira; Senhorinha F. C. F. Teixeira; Jose Teixeira; Luis Martins. 2017. "Parametric Analysis of the Thermal Components of an Alpha-Stirling Engine for Cogeneration Applications." Volume 4A: Dynamics, Vibration, and Control , no. : 1.

Journal article
Published: 01 August 2017 in Applied Thermal Engineering
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ACS Style

Ana Cristina Ferreira; Manuel L. Nunes; Jose Teixeira; Luís A.S.B. Martins; Senhorinha F.C.F. Teixeira; Silvia A. Nebra. Design of a solar dish Stirling cogeneration system: Application of a multi-objective optimization approach. Applied Thermal Engineering 2017, 123, 646 -657.

AMA Style

Ana Cristina Ferreira, Manuel L. Nunes, Jose Teixeira, Luís A.S.B. Martins, Senhorinha F.C.F. Teixeira, Silvia A. Nebra. Design of a solar dish Stirling cogeneration system: Application of a multi-objective optimization approach. Applied Thermal Engineering. 2017; 123 ():646-657.

Chicago/Turabian Style

Ana Cristina Ferreira; Manuel L. Nunes; Jose Teixeira; Luís A.S.B. Martins; Senhorinha F.C.F. Teixeira; Silvia A. Nebra. 2017. "Design of a solar dish Stirling cogeneration system: Application of a multi-objective optimization approach." Applied Thermal Engineering 123, no. : 646-657.

Journal article
Published: 01 June 2016 in Energy
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Micro-cogeneration systems are a promising technology for improving the energy efficiency near the end user, allowing the optimal use of the primary energy sources and significant reductions in carbon emissions. Its use, still incipient, has a great potential for applications in the residential sector. This study aims to develop a methodology for the thermal-economic optimization of micro cogeneration units using Stirling engine as prime mover and concentrated solar energy as the heat source. The thermal-economic optimization was formulated considering the maximization of the annual worth from the system operation, subjected to the nonlinear thermodynamic and economic constraints. The physical model includes the limitations in the heat transfer processes and losses due to the pumping effects and the costing methodology was defined considering a purchase cost equation representative of each system component. Geometric and operational parameters were selected as decision variables. Numerical simulations were developed in MatLab® programming language and the Generalized Pattern Search optimization algorithm with MADSPositiveBasis2N was used in the determination of the optimal solution. A positive annual worth for the defined input simulation conditions and the economic analysis disclosed a system, economically attractive, with a payback period of approximately 10 years.

ACS Style

Ana C. Ferreira; Manuel L. Nunes; José C.F. Teixeira; Luís A.S.B. Martins; Senhorinha F.C.F. Teixeira. Thermodynamic and economic optimization of a solar-powered Stirling engine for micro-cogeneration purposes. Energy 2016, 111, 1 -17.

AMA Style

Ana C. Ferreira, Manuel L. Nunes, José C.F. Teixeira, Luís A.S.B. Martins, Senhorinha F.C.F. Teixeira. Thermodynamic and economic optimization of a solar-powered Stirling engine for micro-cogeneration purposes. Energy. 2016; 111 ():1-17.

Chicago/Turabian Style

Ana C. Ferreira; Manuel L. Nunes; José C.F. Teixeira; Luís A.S.B. Martins; Senhorinha F.C.F. Teixeira. 2016. "Thermodynamic and economic optimization of a solar-powered Stirling engine for micro-cogeneration purposes." Energy 111, no. : 1-17.

Article
Published: 11 December 2015 in Journal of Electronic Materials
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Thermoelectric generators can be used in automotive exhaust energy recovery. As car engines operate under wide variable loads, it is a challenge to design a system for operating efficiently under these variable conditions. This means being able to avoid excessive thermal dilution under low engine loads and being able to operate under high load, high temperature events without the need to deflect the exhaust gases with bypass systems. The authors have previously proposed a thermoelectric generator (TEG) concept with temperature control based on the operating principle of the variable conductance heat pipe/thermosiphon. This strategy allows the TEG modules’ hot face to work under constant, optimized temperature. The variable engine load will only affect the number of modules exposed to the heat source, not the heat transfer temperature. This prevents module overheating under high engine loads and avoids thermal dilution under low engine loads. The present work assesses the merit of the aforementioned approach by analysing the generator output during driving cycles simulated with an energy model of a light vehicle. For the baseline evaporator and condenser configuration, the driving cycle averaged electrical power outputs were approximately 320 W and 550 W for the type-approval Worldwide harmonized light vehicles test procedure Class 3 driving cycle and for a real-world highway driving cycle, respectively.

ACS Style

F. P. Brito; A. Alves; J. M. Pires; L. B. Martins; J. Martins; J. Oliveira; Jose Teixeira; L. M. Gonçalves; M.J. Hall. Analysis of a Temperature-Controlled Exhaust Thermoelectric Generator During a Driving Cycle. Journal of Electronic Materials 2015, 45, 1846 -1870.

AMA Style

F. P. Brito, A. Alves, J. M. Pires, L. B. Martins, J. Martins, J. Oliveira, Jose Teixeira, L. M. Gonçalves, M.J. Hall. Analysis of a Temperature-Controlled Exhaust Thermoelectric Generator During a Driving Cycle. Journal of Electronic Materials. 2015; 45 (3):1846-1870.

Chicago/Turabian Style

F. P. Brito; A. Alves; J. M. Pires; L. B. Martins; J. Martins; J. Oliveira; Jose Teixeira; L. M. Gonçalves; M.J. Hall. 2015. "Analysis of a Temperature-Controlled Exhaust Thermoelectric Generator During a Driving Cycle." Journal of Electronic Materials 45, no. 3: 1846-1870.

Proceedings article
Published: 13 November 2015 in Volume 3: Biomedical and Biotechnology Engineering
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The development of electric and hybrid electric vehicles is motivated by the high prices of fossil fuels, the need for better efficiency and the minimization of pollutants and greenhouse gas emissions. There are several possible technologies for these vehicles but Plug-in Hybrid Electric Vehicles (PHEV) and Fully Electric Vehicles (FEV) are becoming popular. They both require advanced energy storage and management systems. In the design of these powertrains it is of capital importance to evaluate, not only the required traction energy, but also the energy involved in braking and that has the possibility of being regenerated, in real-world routes and traffic conditions. Type-approval driving cycles are insufficient for this purpose, as they do not include parameters that substantially affect the vehicle dynamics, such as road slope and additional friction due to road winding. This work presents a methodology for the energy characterization of driving cycles, based on the numerical integration of specific power, including new parameters such as specific traction and braking energies, cumulative uphill and downhill slopes and cornering friction energy, as well as energy-power distributions. The methodology will help in the comparison of the available type-approval driving cycles and in the definition of more realistic ones that can be used for better assessment of fuel consumption and emissions of vehicles. With input data from real routes, the procedure will be useful in the design of advanced electrical or hybridized powertrain systems, both to size the components and to define appropriate energy management strategies, with the final goal of an improved efficiency. The methodology will also be valuable in the energy classification of European roads. The paper describes the mathematical model, which allows the quantification of all the important energy flows involved in the evolution of a reference vehicle, following a route. This model was developed in the MatLab/Simulink environment and was applied to the characterization of three type-approval cycles and to three real routes. The results indicate that the type-approval cycles are too soft to adequately emulate present day aggressive traffic conditions. Driving cycles simulating significant road slopes and sinuosity should be used in the future, both for consumption and emissions certification and in the development of new powertrains.

ACS Style

Luis A. S. B. Martins; Bruno J. O. Araujo; Jorge J. G. Martins; Francisco C. P. Brito. Methodology for the Energy Characterization of Type-Approval and Real-World Driving Cycles for Passenger Vehicles. Volume 3: Biomedical and Biotechnology Engineering 2015, 1 .

AMA Style

Luis A. S. B. Martins, Bruno J. O. Araujo, Jorge J. G. Martins, Francisco C. P. Brito. Methodology for the Energy Characterization of Type-Approval and Real-World Driving Cycles for Passenger Vehicles. Volume 3: Biomedical and Biotechnology Engineering. 2015; ():1.

Chicago/Turabian Style

Luis A. S. B. Martins; Bruno J. O. Araujo; Jorge J. G. Martins; Francisco C. P. Brito. 2015. "Methodology for the Energy Characterization of Type-Approval and Real-World Driving Cycles for Passenger Vehicles." Volume 3: Biomedical and Biotechnology Engineering , no. : 1.

Conference paper
Published: 13 November 2015 in Volume 3: Biomedical and Biotechnology Engineering
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Solar concentric dish collectors and Stirling engines with cavity receivers are commonly considered for this purpose due to the high efficiency for converting solar radiation into mechanical energy. The study and design of a solar collector of this type, and of its cavity receiver, require solving a mathematical model that take into account the geometric, optical and thermal behavior of all components. With an adequate sizing, not only the useful energy produced on the solar device will meet the energy required for the process, but also the absorber temperature will be the needed for the operation of the Stirling engine. This paper focuses on the construction of a mathematical model that represents the operational performance of a concentric solar dish with cavity receiver for its applications in Stirling engines. The purpose is to develop a designing tool for optimization and for quantifying the effect of changing the values of design parameters over any specific output behavior or the overall performance of the system. The parameters in the optimization include: geometrical variables, i.e., the solar dish diameter, the receiver aperture diameter or the focal length; and optical variables, i.e., rim and incident angles, and irradiation interception factor. The objective is to minimize the solar dish collector cost and calculate the heat available to the Stirling engine, contained in the receiver cavity, to be converted in to mechanical energy. The numerical model was coded in the MatLab® programming language. The results of the simulation disclosed a model able to predict, adequately, the optical and thermal behavior of the described system, so that the model can be used to study the operation and also to design parameters. The optimal results disclosed the configuration of a solar collector dish with a rim angle of about 41° and for a dish diameter of 6.58 m and an aperture receiver of 0.12 m for a minimum cost of 4717 €. It was also concluded that the maximum temperature reached in the absorber of a receiver cavity, is limited mainly by the geometric relationships between the dish diameter, receiver aperture diameter and the aperture ratio, and it is possible to obtain an ideal thermal efficiency of 64%.

ACS Style

Ana Cristina Ferreira; Senhorinha De Fátima Teixeira; Jose Teixeira; Luis Martins. Design Optimization of a Solar Dish Collector for Its Application With Stirling Engines. Volume 3: Biomedical and Biotechnology Engineering 2015, 1 .

AMA Style

Ana Cristina Ferreira, Senhorinha De Fátima Teixeira, Jose Teixeira, Luis Martins. Design Optimization of a Solar Dish Collector for Its Application With Stirling Engines. Volume 3: Biomedical and Biotechnology Engineering. 2015; ():1.

Chicago/Turabian Style

Ana Cristina Ferreira; Senhorinha De Fátima Teixeira; Jose Teixeira; Luis Martins. 2015. "Design Optimization of a Solar Dish Collector for Its Application With Stirling Engines." Volume 3: Biomedical and Biotechnology Engineering , no. : 1.

Proceedings article
Published: 14 November 2014 in Volume 2A: Advanced Manufacturing
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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.

ACS Style

Ana Cristina Ferreira; Senhorinha Teixeira; Manuel Nunes; Luis Martins. Numerical Study of Regenerator Configuration in the Design of a Stirling Engine. Volume 2A: Advanced Manufacturing 2014, 1 .

AMA Style

Ana Cristina Ferreira, Senhorinha Teixeira, Manuel Nunes, Luis Martins. Numerical Study of Regenerator Configuration in the Design of a Stirling Engine. Volume 2A: Advanced Manufacturing. 2014; ():1.

Chicago/Turabian Style

Ana Cristina Ferreira; Senhorinha Teixeira; Manuel Nunes; Luis Martins. 2014. "Numerical Study of Regenerator Configuration in the Design of a Stirling Engine." Volume 2A: Advanced Manufacturing , no. : 1.

Conference paper
Published: 14 November 2014 in Volume 2A: Advanced Manufacturing
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Nitrogen oxides (NOx) from combustion devices are responsible for the formation of acid rain and photochemical smog. This led to a growing environmental concern resulting in the creation of rigorous legislation for harmful emissions. For domestic hot water production appliances, particularly water heaters, there are already some solutions in the market able to achieve low pollutant emissions. However, the complexity of the solutions makes the price tag significantly higher, hampering its mass adoption. It is therefore essential to design and develop simpler and low cost solutions that meet the limits imposed by legislation. This work reports the analysis and validation of the air-gas fuel mixture in a water heater low NOx gas burner element. This is based on a pre-mixed flame made of two separate fuel systems. One is a lean mixture that provides the bulk of the heat load. The other is a rich pilot flame, used to stabilize the flame. For that, a mathematical model was developed and applied, which, upon initial settings, allows for the prediction of the amount of primary air drafted. To validate the theoretical results, experimental tests were performed using a Laser Doppler Anemometer to evaluate the influence of the throat length in the amount of entrained air, as well as, the air induced in the burner element under study. Furthermore, a parametric analysis was performed which evaluated the influence of some variables (geometry, physical properties of fluids, etc.) in the amount of entrained air. The numerical results for the air-fuel equivalence ratio of a conventional burner element (between 0.645 and 0.794) proved to be reasonably close to the value announced by the manufacturer (0.7). Numerical analysis of the burner element with pilot stabilization resulted in values that verify the difference between the richness of the two mixtures. By adjusting the throat-diffuser geometry one may tune the air-fuel ratio of each mixture.

ACS Style

Jose Teixeira; Luis Martins; Manuel A. R. Lopes; Senhorinha De Fátima Teixeira; Manuel Eduardo C Ferreira. Two Stage Atmospheric Burners: Development and Verification of a New Mass-Energy Balance Model. Volume 2A: Advanced Manufacturing 2014, 1 .

AMA Style

Jose Teixeira, Luis Martins, Manuel A. R. Lopes, Senhorinha De Fátima Teixeira, Manuel Eduardo C Ferreira. Two Stage Atmospheric Burners: Development and Verification of a New Mass-Energy Balance Model. Volume 2A: Advanced Manufacturing. 2014; ():1.

Chicago/Turabian Style

Jose Teixeira; Luis Martins; Manuel A. R. Lopes; Senhorinha De Fátima Teixeira; Manuel Eduardo C Ferreira. 2014. "Two Stage Atmospheric Burners: Development and Verification of a New Mass-Energy Balance Model." Volume 2A: Advanced Manufacturing , no. : 1.

Journal article
Published: 17 June 2014 in International Journal of Sustainable Energy Planning and Management
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The support of combined heat and power production systems has gained policy attention, because these are often considered to be less polluting and more efficient than conventional energy conversion systems. As a consequence, the potential market for these energy systems that contribute to reduce greenhouse gas emissions and to enhance energy security on a national level, is shifting from large-scale existing units to small and micro-size emerging technologies. This paper presents a numerical model based on a cost-benefit analysis used to design an optimal cogeneration system for a small-scale building application, considering the Portuguese context and the comparison with the harmonized efficiency reference values for the separate production of electricity and useful heat. The model includes the identification of the objective function terms (i.e., the elements involved in the financial analysis across the system lifetime and the economic evaluation of costs) and benefits of the combined heat and power production system. The economic viability of cogeneration systems significantly depends on system technology, client energy requirements and support schemes implemented in the respective countries. A strategic approach is necessary to adequately embed the new technology as a feasible solution in terms of investment and operational costs. Only by matching the energy supply to the needs and expectations of the energy users, it will be possible to improve the market competitiveness of these alternative power production plants. The optimal solution disclosed a positive annual worth, which is higher if the carbon emission savings are monetized. In addition, the optimal system represents a more efficient way to produce useful heat and electricity (i.e. a positive primary energy saving) and to reduce gas emissions. A cost-benefit analysis can be applied for the techno-economic evaluation of a CHP system by assessing the monetary socio-environmental costs and benefits of a capital investment over its useful lifetime.

ACS Style

Ana Cristina Ferreira; Manuel Lopes Nunes; Luis Martins; Senhorinha De Fátima Teixeira. Technical-Economic Evaluation of a Cogeneration Unit Considering Carbon Emission Savings. International Journal of Sustainable Energy Planning and Management 2014, 2, 33 -46.

AMA Style

Ana Cristina Ferreira, Manuel Lopes Nunes, Luis Martins, Senhorinha De Fátima Teixeira. Technical-Economic Evaluation of a Cogeneration Unit Considering Carbon Emission Savings. International Journal of Sustainable Energy Planning and Management. 2014; 2 ():33-46.

Chicago/Turabian Style

Ana Cristina Ferreira; Manuel Lopes Nunes; Luis Martins; Senhorinha De Fátima Teixeira. 2014. "Technical-Economic Evaluation of a Cogeneration Unit Considering Carbon Emission Savings." International Journal of Sustainable Energy Planning and Management 2, no. : 33-46.

Conference paper
Published: 01 June 2014 in 2014 14th International Conference on Computational Science and Its Applications
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Stirling engine technologies have been applied to cogeneration systems mainly for residential applications. The performance of Stirling engines has been evaluated considering different operational conditions, which include the electrical and thermal production, working fluid pressure, components geometrical sizing and others. Thermal-economic evaluation represents an effective tool to optimize a power plant with this type of technology. This study presents a mathematical model that encloses the physical variable equations able to simulate the thermodynamic transformations of the cycle, and a set of equations that define the purchase cost of the main plant components. The paper presents a numerical study faithfully simulating a micro-cogeneration unit based on an alpha type Stirling Engine. The simulations were performed through a Mat Lab code able to disclose the best economic output for the best combination of decision variables. Stirling engine performance is affected by geometrical and operational parameters optimization is required in order to obtain the best performance. Results show that the implemented mathematical model reached an optimal solution disclosing a positive profit for the best physical configuration of the system. Also, the cost estimation based on sizing and quality parameters shows a good correlation with the capital investment costs of commercial models.

ACS Style

Ana Cristina Ferreira; Manuel Nunes; Luis Martins; Senhorinha De Fátima Teixeira. Maximum Profit of a Cogeneration System Based on Stirling Thermodynamic Cycle. 2014 14th International Conference on Computational Science and Its Applications 2014, 156 -160.

AMA Style

Ana Cristina Ferreira, Manuel Nunes, Luis Martins, Senhorinha De Fátima Teixeira. Maximum Profit of a Cogeneration System Based on Stirling Thermodynamic Cycle. 2014 14th International Conference on Computational Science and Its Applications. 2014; ():156-160.

Chicago/Turabian Style

Ana Cristina Ferreira; Manuel Nunes; Luis Martins; Senhorinha De Fátima Teixeira. 2014. "Maximum Profit of a Cogeneration System Based on Stirling Thermodynamic Cycle." 2014 14th International Conference on Computational Science and Its Applications , no. : 156-160.

Proceedings article
Published: 15 November 2013 in Volume 1: Advances in Aerodynamics
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Energy degradation can be calculated by the quantification of entropy and loss of work and is a common approach in power plant performance analysis. Information about the location, amount and sources of system deficiencies are determined by the exergy analysis, which quantifies the exergy destruction. Micro-gas turbines are prime movers that are ideally suited for cogeneration applications due to their flexibility in providing stable and reliable power. This paper presents an exergy analysis by means of a numerical simulation of a regenerative micro-gas turbine for cogeneration applications. The main objective is to study the best configuration of each system component, considering the minimization of the system irreversibilities. Each component of the system was evaluated considering the quantitative exergy balance. Subsequently the optimization procedure was applied to the mathematical model that describes the full system. The rate of irreversibility, efficiency and flaws are highlighted for each system component and for the whole system. The effect of turbine inlet temperature change on plant exergy destruction was also evaluated. The results disclose that considerable exergy destruction occurs in the combustion chamber. Also, it was revealed that the exergy efficiency is expressively dependent on the changes of the turbine inlet temperature and increases with the latter.

ACS Style

Ana Cristina Ferreira; Senhorinha F. Teixeira; Jose Teixeira; Manuel Nunes; Luis Martins. Exergy Efficiency Optimization for Gas Turbine Based Cogeneration Systems. Volume 1: Advances in Aerodynamics 2013, 1 .

AMA Style

Ana Cristina Ferreira, Senhorinha F. Teixeira, Jose Teixeira, Manuel Nunes, Luis Martins. Exergy Efficiency Optimization for Gas Turbine Based Cogeneration Systems. Volume 1: Advances in Aerodynamics. 2013; ():1.

Chicago/Turabian Style

Ana Cristina Ferreira; Senhorinha F. Teixeira; Jose Teixeira; Manuel Nunes; Luis Martins. 2013. "Exergy Efficiency Optimization for Gas Turbine Based Cogeneration Systems." Volume 1: Advances in Aerodynamics , no. : 1.

Proceedings article
Published: 15 November 2013 in Volume 1: Advances in Aerodynamics
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The last decade has witnessed a growing interest in the use of Stirling engine cogeneration systems for residential applications, due to their prospect for high efficiency, good performance at partial load, fuel flexibility, including the possible use of renewables, low emissions, vibration and noise levels. Stirling engines have sealed operating chambers, low wear and, as a consequence, low operating costs. In the European building sector, micro-cogeneration power plants are being designed to fulfill the heating requirements of the building and, additionally, generate electricity for internal consumption or for feeding into the local grid. Thermal-economic evaluation represents an effective tool to optimize a power plant with this type of technology. The mathematical formulation includes a set of equations able to describe and simulate the physical system, as well as a set of equations that define the cost of each plant component. This paper presents a numerical study faithfully simulating the real conditions of a micro-CHP unit based on an alpha type Stirling Engine. The simulations were performed through a MatLab® code that assesses the thermodynamic efficiency, including heat transfer limitations and pumping losses throughout the system. Results showed that heat-transfer limitations strongly affect cycle efficiency, particularly in the regenerator case. The pumping losses are less important when hydrogen or helium are used.

ACS Style

Ana Cristina Ferreira; Senhorinha Teixeira; Christophe Ferreira; Jose Teixeira; Manuel Nunes; Luis Martins. Thermal-Economic Modeling of a Micro-CHP Unit Based on a Stirling Engine. Volume 1: Advances in Aerodynamics 2013, 1 .

AMA Style

Ana Cristina Ferreira, Senhorinha Teixeira, Christophe Ferreira, Jose Teixeira, Manuel Nunes, Luis Martins. Thermal-Economic Modeling of a Micro-CHP Unit Based on a Stirling Engine. Volume 1: Advances in Aerodynamics. 2013; ():1.

Chicago/Turabian Style

Ana Cristina Ferreira; Senhorinha Teixeira; Christophe Ferreira; Jose Teixeira; Manuel Nunes; Luis Martins. 2013. "Thermal-Economic Modeling of a Micro-CHP Unit Based on a Stirling Engine." Volume 1: Advances in Aerodynamics , no. : 1.

Conference paper
Published: 09 November 2012 in Volume 1: Advances in Aerospace Technology
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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.

ACS Style

Ana Cristina Ferreira; Senhorinha Teixeira; Jose Teixeira; Manuel Nunes; Luis Martins. Modeling a Stirling Engine for Cogeneration Applications. Volume 1: Advances in Aerospace Technology 2012, 361 -369.

AMA Style

Ana Cristina Ferreira, Senhorinha Teixeira, Jose Teixeira, Manuel Nunes, Luis Martins. Modeling a Stirling Engine for Cogeneration Applications. Volume 1: Advances in Aerospace Technology. 2012; ():361-369.

Chicago/Turabian Style

Ana Cristina Ferreira; Senhorinha Teixeira; Jose Teixeira; Manuel Nunes; Luis Martins. 2012. "Modeling a Stirling Engine for Cogeneration Applications." Volume 1: Advances in Aerospace Technology , no. : 361-369.

Journal article
Published: 03 July 2012 in Energy
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A numerical optimisation method, previously applied to a large industrial cogeneration plant, has been adapted for a small-scale unit that must be driven by the heat demand of a medium-size building located in the north of Portugal. The unit is based on a micro-gas turbine and includes an internal pre-heater (typical of these types of small-scale units) and a water heater. The mathematical model yields a non-linear objective function, subject to physical constraints of system operation, and defined as the maximisation of the annual worth of the CHP system. Seven decision variables were selected for the optimization algorithm, including performance of internal gas turbine components and the electrical and thermal powers. The latter is linked to the estimated thermal load of the building via the number of working hours. A purchase cost equation was used for each major plant component and takes into account size and performance variables. The optimal solution was obtained for a feed-in-tariff and natural gas price reference scenario, and shows higher standards than models currently available in the market. A sensitivity analysis was carried out for the two variables that significantly affect the annual worth. Regarding the physical aspects of the major system components, the analysis revealed that the most relevant and susceptible variables are the compressor pressure ratio, the internal pre-heater effectiveness and the turbine inlet temperature.

ACS Style

Ana C.M. Ferreira; Manuel L. Nunes; Senhorinha F.C.F. Teixeira; Celina P. Leão; Ângela M. Silva; José C.F. Teixeira; Luís A.S.B. Martins. An economic perspective on the optimisation of a small-scale cogeneration system for the Portuguese scenario. Energy 2012, 45, 436 -444.

AMA Style

Ana C.M. Ferreira, Manuel L. Nunes, Senhorinha F.C.F. Teixeira, Celina P. Leão, Ângela M. Silva, José C.F. Teixeira, Luís A.S.B. Martins. An economic perspective on the optimisation of a small-scale cogeneration system for the Portuguese scenario. Energy. 2012; 45 (1):436-444.

Chicago/Turabian Style

Ana C.M. Ferreira; Manuel L. Nunes; Senhorinha F.C.F. Teixeira; Celina P. Leão; Ângela M. Silva; José C.F. Teixeira; Luís A.S.B. Martins. 2012. "An economic perspective on the optimisation of a small-scale cogeneration system for the Portuguese scenario." Energy 45, no. 1: 436-444.

Conference paper
Published: 01 January 2012 in Transactions on Petri Nets and Other Models of Concurrency XV
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Cogeneration is a high-efficiency technology that has been adapted to small and micro scale applications. In this work, the development and test of a numerical optimization model is carried out in order to implement an analysis that will lead to the optimal design of a small cogeneration system. The main idea is the integration of technical and economic aspects in the design of decentralized energy production considering the requirements for energy consumption for the building sector. The nonlinear optimization model was solved in MatLab®environment using two local optimization methods: the Box and the SQP method. The optimal solution provided a positive annual worth and disclosed reasonable values for the decision variables of the thermo-economic model. Both methods converged for the same solution, demonstrating the validity of the implemented approach. This study confirmed that the use of numerical optimization models is of utmost importance in the assessment of energy systems sustainability.

ACS Style

Ana C. M. Ferreira; Ana Maria A. C. Rocha; Senhorinha F. C. F. Teixeira; Manuel L. Nunes; Luís B. Martins. On Solving the Profit Maximization of Small Cogeneration Systems. Transactions on Petri Nets and Other Models of Concurrency XV 2012, 7335, 147 -158.

AMA Style

Ana C. M. Ferreira, Ana Maria A. C. Rocha, Senhorinha F. C. F. Teixeira, Manuel L. Nunes, Luís B. Martins. On Solving the Profit Maximization of Small Cogeneration Systems. Transactions on Petri Nets and Other Models of Concurrency XV. 2012; 7335 ():147-158.

Chicago/Turabian Style

Ana C. M. Ferreira; Ana Maria A. C. Rocha; Senhorinha F. C. F. Teixeira; Manuel L. Nunes; Luís B. Martins. 2012. "On Solving the Profit Maximization of Small Cogeneration Systems." Transactions on Petri Nets and Other Models of Concurrency XV 7335, no. : 147-158.

Conference paper
Published: 01 January 2011 in Volume 6: Fluids and Thermal Systems; Advances for Process Industries, Parts A and B
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The use of combined heat and power (CHP) systems to produce both electric and thermal energies for medium-size buildings is on the increase, due to their high overall efficiency, high energy prices and political and social awareness. In this paper, an energy-economic study is presented. The main objective is to implement an analysis that will lead to the optimal design of a small cogeneration system, given the thermal power duration curve of a multi-family residential building. A methodology was developed to obtain this curve for a reference B-class building located in the North of Portugal. The CHP unit is based on a micro gas-turbine and includes an Internal Pre-Heater (IPH), typical of these types of small-scale units, and an external Water Heater (WH). A numerical optimization method was applied to solve the thermo-economic model. The mathematical model yields an objective function defined as the maximization of the annual worth of the cogeneration system. A purchase cost equation was used for each major plant component that takes into account size and performance variables. Seven decision variables were selected for the optimization algorithm, including performance of internal gas-turbine components and electrical and thermal powers. The results show that, the revenue from selling electricity to the grid and fuel costs have the greatest impact on the annual worth of the system. The optimal solution for the small CHP is sensitive to fuel price, electricity feed-in-tariff, capital cost and to the thermal load profile of the building. High European energy prices point towards future micro gas-turbines with better electrical efficiencies, achieved via a higher pressure-ratio compressor and turbine inlet temperature.

ACS Style

Luís B. Martins; Ana C. M. Ferreira; Manuel L. Nunes; Celina P. Leão; Senhorinha F. C. F. Teixeira; Francisco Marques; José C. F. Teixeira. Optimal Design of Micro-Turbine Cogeneration Systems for the Portuguese Buildings Sector. Volume 6: Fluids and Thermal Systems; Advances for Process Industries, Parts A and B 2011, 179 -186.

AMA Style

Luís B. Martins, Ana C. M. Ferreira, Manuel L. Nunes, Celina P. Leão, Senhorinha F. C. F. Teixeira, Francisco Marques, José C. F. Teixeira. Optimal Design of Micro-Turbine Cogeneration Systems for the Portuguese Buildings Sector. Volume 6: Fluids and Thermal Systems; Advances for Process Industries, Parts A and B. 2011; ():179-186.

Chicago/Turabian Style

Luís B. Martins; Ana C. M. Ferreira; Manuel L. Nunes; Celina P. Leão; Senhorinha F. C. F. Teixeira; Francisco Marques; José C. F. Teixeira. 2011. "Optimal Design of Micro-Turbine Cogeneration Systems for the Portuguese Buildings Sector." Volume 6: Fluids and Thermal Systems; Advances for Process Industries, Parts A and B , no. : 179-186.