The Educational Value of Modelling Complex Thermodynamic Systems with System Dynamics Software

The solution of problems involving complex thermodynamic systems often occupies much of a students\u27 time and can be a distraction from them developing a clear understanding of system components, interaction of subsystems, modelling simplifications and assumptions, and design optimization. Refocusing students on the fundamental concepts of thermal systems design and analysis is possible with the introduction of system modelling software that carries some of the load of repetitive calculation required for complex systems. Models of thermodynamic systems encountered in an advanced undergraduate thermodynamics course were developed by students (some provided to students) to solve homework problems of complex steam power plants, internal combustion engines, gas turbine power plants, refrigeration, and building energy systems. Computer modelling systems used included two commercial modelling programs, an open source program, and systems developed by the authors. Use of the modelling software forced students to setup problems in the same way as if solved on paper but allowed them to identify common components and processes that could be modeled by common blocks and used in multiple thermal systems. One example presented is a simple process block that gives the state for any location in a converging/diverging supersonic nozzle with a normal shock. The initial implementation has resulted in positive feedback from students and an improved self-efficacy in understanding and modelling complex thermodynamic systems not presented in class

Battery, Hybrid and Fuel-Cell Propulsion Systems

The main purpose of the Research is theoretical and experimental evaluation of electric propulsion systems: pure electric ones, fed exclusively by electrochemical energy storage, hybrid electric, in which the power for propulsion comes from different sources, and fuel cell-based vehicles. These studies were carried on through an extended modelling and experimental activity, related to: • Modelling and experimental activities on electrochemical storage systems and super-capacitors, to evaluate their performance and to better individuate the optimal sizing for usage on-board electric and hybrid vehicles. • Design and realisation of a Fuel-Cell based vehicle, starting from the design of the propulsion system, for which dedicated models in Matlab-Simulink® environment were specifically realised, coming to an extended laboratory test activity for all the components, specially for the Fuel-Cell System. • Design of a complete line of electric and hybrid buses, based on the modelling of the propulsion system in collaboration with the manufacturer, through the usage of new object-oriented modelling techniques realised in Dymola-Modelica® environment. After evaluating different energy management strategies, an exhaustive comparison with conventional and electric pure versions has been carried on. The PhD Thesis, after an introduction about innovative propulsion systems, describes in detail all the activities presented, trying to summarise general techniques of design and management for hybrid vehicles

Special issue on standalone renewable energy system: Modeling and controlling

1. Introduction Standalone (off-grid) renewable energy systems supply electricity in places where there is no access to a standard electrical grid. These systems may include photovoltaic generators, wind turbines, hydro turbines or any other renewable electrical generator. Usually this kind of system includes electricity storage (commonly, lead-acid batteries, but also other types of storage can be used, such as lithium batteries, other battery technologies, supercapacitors and hydrogen). In some cases, a backup generator (usually powered by fossil fuel, diesel or gasoline) is part of the hybrid system. Low-power standalone systems are usually called off-grid systems and typically power single households by diesel generators or by solar photovoltaic (PV) systems (solar home systems) [1]. Systems of higher power are called micro- or mini-grids, which can supply several households or even a whole village. Mini- or micro-grids, powered by renewable sources, can be classified as smart grids, allowing information exchange between the consumers and the distributed generation [2]. The modelling of the components, the control of the system and the simulation of the performance of the whole system are necessary to evaluate the system technically and economically. The optimization of the sizing and/or the control is also an important task in this kind of systems..

Modelling of power exhaust in fusion plasmas

This PhD thesis deals with the thorny problem of “Modelling of power exhaust in fusion plasmas”, a challenge concerning the development of a system able to withstand the large loads expected in the fusion power plant divertor. After an introduction to fusion and to the key concepts modelling the behaviour of the plasma during plasma-surface interactions and describing the power exhaust, an overview of the state-of-the-art in the research field on power exhaust is given. A brief introduction on theoretical basis of the plasma boundary reconstruction precedes the author first contribution in the design and vertical stability analysis of plasma alternative magnetic configurations for a demonstration fusion power plant (DEMO). The second contribution concerns an assessment of the DEMO divertor target tiles lifetime in case of strike-point sweeping. This technique is one of the most promising candidate solution to the power exhaust issue but its main drawback is related to the periodical heating and cooling of the plasma facing components inducing the thermal-fatigue phenomenon. To evaluate the lifetime of the DEMO divertor target tiles, different 2D and 3D thermo-mechanical models are presented. Finally, a preliminary analysis on the wobbling technique applied to a DEMO Double Null plasma magnetic configuration is illustrated

Electric thermal storage in isolated wind diesel power systems: use of distributed secondary loads for frequency regulation

Thesis (Ph.D.) University of Alaska Fairbanks, 2017Isolated coastal utilities in Arctic villages commonly use a mix of diesel and wind power to provide electrical service to their consumers. It is common for such communities to experience periods of high wind generation for which no immediate demand exists and either waste, curtail, or poorly utilize the surplus. The objective of the present work is to explore (through mathematical and numerical modelling) the technical feasibility of and optimization strategies for distributing this excess wind energy as domestic space heat for use as a cleaner, more economical alternative to fossil fuels. Autonomously controlled Electric Thermal Storage (ETS) devices are considered as a solution to decouple the supply of excess wind power with domestic heat demand without the need for communication infrastructure or a second distribution circuit. First, using numerical heat transfer analysis, it is shown that the performance of an ETS heater core can be generalized and expressed in terms of its physical properties and simple geometric dimensions in such a way as to inform system sizing and economic performance studies for prospective applications. Furthermore, a collection of autonomous ETS units is shown (using a full-scale lab-validated mathematical model) to possess the ability to assume the role of partial and/or sole frequency regulator on a hybrid wind-diesel system. Several design changes are proposed, which render the commercially-available units more amenable to frequency regulation. Ultimately, ETS is shown to be a promising alternative means of utilizing excess renewable energy for domestic space heat while providing additional stability to the electrical grid.Chapter 1 Introduction -- 1.1 Hybrid Wind-Diesel Systems -- 1.2 Frequency Regulation -- 1.3 Voltage Regulation -- 1.4 Energy Storage -- 1.5 Secondary Loads -- 1.6 Electric Thermal Storage -- 1.7 Summary and Organization of Subsequent Chapters -- 1.8 Nomenclature -- 1.9 References -- Chapter 2 Summary of Measurement and Modeling Methodologies -- 2.1 Numerical Heat Transfer - Measurement -- 2.2 Numerical Heat Transfer - Physical Modeling -- 2.3 Electromechanical Dynamics - Measurement -- 2.3.1 Field Measurements -- 2.3.2 Raw Data -- 2.3.3 Post Processing: RMS Values -- 2.3.4 Post Processing: Frequency and Power Factor -- 2.3.5 Post Processing: Impedance, Real Power, and Reactive Power -- 2.4 Electromechanical Dynamics - Modeling -- 2.4.1 Model Structure -- 2.4.2 Equivalent Circuit Simulation Process -- 2.4.3 Solution of Nonlinear Ordinary Differential Equations (ODEs) -- 2.5 References -- Chapter 3 Generalized Heat Flow Model of a Forced Air Electric Thermal Storage Heater Core -- 3.1 Abstract -- 3.2 Introduction -- 3.3 Model -- 3.3.1 Definitions -- 3.3.2 Structure -- 3.3.3 Governing Equations -- 3.3.4 Boundary Conditions -- 3.3.5 Material Properties -- 3.4 Analysis -- 3.4.1 Solution Linearization and Air Velocity Profile -- 3.4.2 Thermal Gradients -- 3.4.3 Parameter Sweep -- 3.5 Results and Discussion -- 3.5.1 One-parameter Model -- 3.5.2 Two-parameter Model -- 3.5.3 Core Energy Balance -- 3.5.4 Stove Modelling -- 3.6 Conclusions -- 3.7 Acknowledgements -- 3.8 Funding -- 3.9 Nomenclature -- 3.10 References -- Chapter 4 Development of a Full-Scale-Lab-Validated Dynamic Simulink© Model for a Stand-Alone -- Wind-Powered Microgrid -- 4.1 Abstract -- 4.2 Introduction -- 4.3 Mathematical Model -- 4.3.1 Diesel Engine/Governor Model -- 4.3.2 Synchronous Generator Model -- 4.3.3 Excitation System Model -- 4.3.4 Induction Generator Model -- 4.4 Data Collection -- 4.5 Results -- 4.5.1 Data Processing -- 4.5.2 Diesel Only (DO) Mode - Laboratory Results -- 4.5.3 Diesel Only (DO) Mode - Simulation Results -- 4.5.4 Wind-Diesel (WD) Mode -- 4.6 Conclusions -- 4.7 Future Work -- 4.8 Acknowledgements -- 4.9 References -- Chapter 5 Frequency Regulation by Distributed Secondary Loads on Islanded Wind-Powered Microgrids -- 5.1 Abstract -- 5.2 Introduction -- 5.3 Mathematical Model -- 5.3.1 Wind-Diesel Hybrid System -- 5.3.2 Individual ETS Units Response -- 5.3.3 Aggregate DSL Response -- 5.4 Analysis -- 5.4.1 Invariant Model Inputs (Machine Parameters) -- 5.4.2 Variable Model Inputs -- 5.4.3 Model Outputs -- 5.5 Results and Discussion -- 5.5.1 Synchronized Switching -- 5.5.2 Staggered Switching -- 5.5.3 Additional Observations and Discussion -- 5.6 Conclusion and Future Work -- 5.7 References -- Chapter 6 Modelling Integration Strategies for Autonomous Distributed Secondary Loads on High Penetration Wind-Diesel Microgrids -- 6.1 Abstract -- 6.2 Introduction -- 6.3 Model -- 6.3.1 System Requirements -- 6.3.2 System Components -- 6.3.3 Control Strategy -- 6.4 Results and Discussion -- 6.4.1 Ramp Simulation -- 6.4.2 Representative Simulation -- 6.4.3 Design Considerations -- 6.5 Conclusions -- 6.6 Acknowledgements -- 6.7 References -- Chapter 7 Results and Observations -- 7.1 Result and Observations of Chapter 3 -- 7.2 Results and Observations of Chapter 4 -- 7.3 Results and Observations of Chapter 5 -- 7.4 Results and Observations of Chapter 6 -- Chapter 8 Conclusions -- 8.1 Conclusions for Generalized Heat Flow Model of a Forced Air Electric Thermal Storage Heater Core -- 8.2 Conclusions for Development of a Full-Scale-Lab-Validated Dynamic Simulink© Model for a Stand-Alone Wind-Powered Microgrid -- 8.3 Conclusions for Frequency Regulation by Distributed Secondary Loads (DSLs) on Islanded Wind-Powered Microgrids -- 8.4 Conclusions for Modeling Integration Strategies for Autonomous Distributed Secondary Loads on High Penetration Wind-Diesel Microgrids -- 8.5 Suggestions for Future Research -- 8.6 Overall Conclusions -- 8.7 Acknowledgements

Modelling the Power Cost of Application Software Running on Servers

One of the most important aspects of managing data centres is controlling the power consumption of applications running on servers. Developers, in particular, should evaluate each of their applications from a power consumption point of view. One can conduct an evaluation by creating models that predict power usage while running applications on servers. For this purpose, this study creates a non-exclusive test bench that can collect data on subsystem utilization by using a performance counter tool. Based on the selected subsystem performance, various models have been created to estimate the power consumption of applications running on servers. The author's models are created based on collecting the performance on four subsystems (i.e. the CPU, Memory, Disk and Interface) by Collectd tool, and the actual power consumption of a machine using a TED5000 power meter. These subsystems have been chosen because they are the components of the server that consume the most power. In addition, as the experiments in this study demonstrate, using these subsystems as the model's input is the most efficient selection across different hardware platforms. The accuracy of the models is affected by the model inputs selection. Creating the model requires several steps: (i) connect the power meter to the server and install all the required packages such as Collectd; (ii) perform workloads on the selected subsystems; (iii) collect and simplify the data (subsystems counters and actual power) that has been stored during performing the workloads; and (iv) train the data by a modelling technique in order to create the model. This work has seven dimensions; (i) collection of the performance counters and the actual power consumption of a system, and simplification of the collected data; (ii) introduction of a simple test bench for modelling and estimation of the power consumption of an application; (iii) introduction of two modelling techniques: Neural Network and Linear Regression; (iv) design of two types of workloads; (v) use of three real servers with different configurations; (vi) use of four scenarios to validate the models; (vii) proof of the importance of the subsystems selection; and (viii) automation of the test bench. With these models, power meter devices will no longer be necessary in measuring power consumption. Instead, the models can be used to predict power consumption. Generally, Neural Network models have fewer errors than Linear Regression models, and all the models (Neural Network or Linear Regression) perform better with long time workload design

Power Flow Modelling of Dynamic Systems - Introduction to Modern Teaching Tools

As tools for dynamic system modelling both conventional methods such as transfer function or state space representation and modern power flow based methods are available. The latter methods do not depend on energy domain, are able to preserve physical system structures, visualize power conversion or coupling or split, identify power losses or storage, run on conventional software and emphasize the relevance of energy as basic principle of known physical domains. Nevertheless common control structures as well as analysis and design tools may still be applied. Furthermore the generalization of power flow methods as pseudo-power flow provides with a universal tool for any dynamic modelling. The phenomenon of power flow constitutes an up to date education methodology. Thus the paper summarizes fundamentals of selected power flow oriented modelling methods, presents a Bond Graph block library for teaching power oriented modelling as compact menu-driven freeware, introduces selected examples and discusses special features.Comment: 12 pages, 9 figures, 4 table

Energy-based Analysis of Biochemical Cycles using Bond Graphs

Thermodynamic aspects of chemical reactions have a long history in the Physical Chemistry literature. In particular, biochemical cycles - the building-blocks of biochemical systems - require a source of energy to function. However, although fundamental, the role of chemical potential and Gibb's free energy in the analysis of biochemical systems is often overlooked leading to models which are physically impossible. The bond graph approach was developed for modelling engineering systems where energy generation, storage and transmission are fundamental. The method focuses on how power flows between components and how energy is stored, transmitted or dissipated within components. Based on early ideas of network thermodynamics, we have applied this approach to biochemical systems to generate models which automatically obey the laws of thermodynamics. We illustrate the method with examples of biochemical cycles. We have found that thermodynamically compliant models of simple biochemical cycles can easily be developed using this approach. In particular, both stoichiometric information and simulation models can be developed directly from the bond graph. Furthermore, model reduction and approximation while retaining structural and thermodynamic properties is facilitated. Because the bond graph approach is also modular and scaleable, we believe that it provides a secure foundation for building thermodynamically compliant models of large biochemical networks

INTRODUCTION

This special issue of the Journal of Energy is dedicated to the establishment of today the Department for Energy and Power Systems (ZVNE), University of Zagreb Faculty of Electrical Engineering and Computing in 1934. in that time the High Voltage Department as part of the Technical Faculty. For this reason, the history of the Department for Energy and Power Systems is presented in the introductory article, while the other articles are part of a broad scientific and professional work of the employees of the Department and some of the articles were created in wide cooperation with experts from the companies, that graduated from the Department. Journal of Energy special issue: present 17 papers selected for publication in Journal of Energy after having undergone the peer review process. We would like to thank the authors for their contributions and the reviewers who dedicated their valuable time in selecting and reviewing these papers. We hope this special issue will provide you valuable information of some achievements at Department of Energy and Power Systems, Faculty of Electrical Engineering and Computing. Short introduction of scientific and expert work of the Department for Energy and Power Systems (ZVNE): Besides educational energy related programmes for undergraduate, graduate and postgraduate students, DEPARTMENT OF ENERGY AND POWER SYSTEMS has been actively involved for many years in many scientific and expert studies. Studies on scientific projects include collaboration with industry, national institutions, electric utilities, and many foreign universities. The Department has developed valuable international cooperation with many research institutions around the world, either directly or through inter-university cooperation. The Department is the leading institution in the field of electrical power engineering in the region, it has a long lasting cooperation with the economic sector, and it is recognized for its scientific activities and a large number of published scientific papers in globally relevant journals, as well as numerous national and international scientific projects. Main Department areas of activities are: a) Power Engineering and Power Technologies, b) Energy, Environment, Energy Management and c) Nuclear Power Engineering In Power Systems Engineering the research is focused to development of both fundamental knowledge and applications of electrical power engineering. The research is generally directed to increasing the availability and the reliability of a power system with an emphasis on the adjustment to the open market environment. Specific goals include: improving models and methodologies for power system analysis, operation and control; development, production and application of models and methodologies for power systems planning, maintenance and development; application of soft-computing (artificial intelligence, meta-heuristics, etc.), information technologies (web-oriented technologies, geographic information systems, enterprise IT solutions, etc.) and operational research in improving processes of planning, development, exploitation and control of power systems; investigation on applications for coordinated control of power system devices and exploring the power system stability, security and economic operation; integration of intelligent devices and agents in energy management systems and distribution management systems equipment and software; advanced modelling of dynamics, disturbances and transient phenomena in transmission and distribution networks (in particular regarding distributed generation); advances in fault detection, restoration and outage management. The researches also cover high voltage engineering. At time of global changes in the energy sector, with emphasis on sustainable development, significant efforts are devoted to liberalization efforts, facilities revitalization, improved legislation and adoption of new standards. In area of Power Technologies, Energy and Environment, Energy Management the main framework for the research are: sustainable electricity generation on a liberalized market, modelling ETS and electricity market; energy security and climate change; power system optimization with emission trading; rational use of energy and energy savings; energy management in industry and buildings; energy conservation and energy auditing in industry and buildings. General objective of the research is to develop methodologies for quantitative assessment of the environmental impact of applicable energy technologies (electric power producing plants and their technology chains), as a base for estimating optimal long-term development strategy of the Croatian power system. Research work includes new strategies of energy sector and power system development; preparing medium and long-term electricity generation expansion plan for power system; comparison of energy, economic and environmental characteristics of different options for electric power generation; studies for rational use of energy and energy savings, assuming a centralized structure of the electricity market. Research work also includes renewable energy sources and its role in power sector, as well as electricity production considering cap on CO2 emissions. Research covers development of new models for power system generation optimization and planning under uncertainties on the open electricity market. The goal of that research is to create analytical and software tools which will enable a successful transition to liberalized electricity market and ensure healthy and efficient power system operation in compliance with environmental requirements. In the Nuclear Energy Field research cover nuclear physics reactor theory, nuclear power plants. fuel cycles and reactors materials and general objective of the research is to develop methodologies for reliable assessment of nuclear power plants operational safety. In the nuclear energy field the specific analysis cover calculations of transients and consequences of potential accidents in NPP Krško. In the field of safety analyses of nuclear power plants the research activities are oriented to the mathematical modelling of nuclear power plant systems and components

Feasibility of a solar photo-voltaic system as an energy source for lighting in grid-connected residential buildings in Cameroon : case study of Buea : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Environmental Management (without major) at Massey University, Palmerston North (New Zealand)

Cameroon has the second largest hydropower potential in Africa after the Democratic Republic of Congo. However, even with this potential, electricity supply in the country is insufficient and unreliable especially in the midst of the dry season, thus the many residents affected are inconvenienced due to lack of energy for lighting. This and coupled with climate change constraints, necessitates the investigation of measures geared towards effective utilization of the available energy from the grid and the feasibility of an alternative energy source to be employed in the onsite generation of electricity in residential buildings for lighting. In this research, a total of 100 residential dwellings of different classes (T1 to T7) were surveyed in the town of Buea, Cameroon. The survey employed the use of a questionnaire designed to collect data on current lighting technologies used in dwellings and the electricity load for lighting and basic communication appliances (radios and mobile phone chargers) of the dwellings. An economic and environmental analysis for transition towards efficient lighting in the surveyed dwellings was conducted. The load profiles of the dwellings classified from the k-means algorithm in R Statistics were used in the HOMER Pro software for a techno-economic modelling of residential PV systems (stand-alone and grid back-up) to meet the load of the dwellings. The survey had a questionnaire return rate of 92%. Results of the survey revealed that artificial lighting in the dwellings is achieved through the use of the following technologies: incandescent lamps, compact fluorescent lamps (CFL) and fluorescent tubes. The economic assessment of efficient lighting transition in the dwellings for an artificial daily lighting duration of six hours revealed a net present value (NPV) that ranges from $47 (T1 building) to$282.02 (T5 building), a benefit cost ratio (BCR) of 1.84 and a simple payback period (PBP) of 0.17 year (2 months) for the substitution of current incandescent lamps in dwellings with CFL. The substitution of incandescent lamps with light emitting diodes (LED) revealed an NPV of the range $89.14 (T1 building) to$370 (T5 building), a BCR of 3.18 and a PBP of 1.92 years (23 months). The substitution of incandescent lamps with CFL and LED results to a reduction in lighting related greenhouse gas (GHG) emissions from dwellings by 66.6% and 83.3% respectively. Results from the HOMER modelling revealed a levelized cost of electricity (LCOE) of the PV system under the following parameters: 0% annual capacity shortage, 40% minimum battery state if charge (SOC), 25 years PV lifetime, 5% discount rate and 2% inflation rate to be 10 to 13 times more expensive (stand-alone system) and four to eight times more expensive (back-up system) compared to the grid electricity. The PV systems have potentials to save an annual emission of 89.17 to 527.37 kgCO2-e for the stand-alone system. Favourable government policies are necessary to spur the deployment of these low carbon technologies in the residential sector of Cameroon