Kogeneracija – techniškai pažangus šilumos ir elektros energijos gamybos būdas. Elektros energija gaunama iš generatoriaus, o šilumos energija gaunama variklio aušinimo metu. Kadangi Lietuvoje elektros ir šilumos gamyba iš atsinaujinančių energijos šaltinių yra labai aktualu, darbo tikslas: suprojektuoti kogeneracinės jėainės vidaus elektros tinklą, parinkti kogeneratorių. / Cogeneration technologically advanced of heat and electricity production. It is particularly relevant for Lithuania, because there exists a strong need for heat production, the restructuring of heat and electricity networks, is changing its legal framework, the development of market relations. Undergraduate work is designed combined heat and power plant. Cogeneration plant will be used for alternative fuel: biogas which derived from the landfill. However, in order to improve the efficiency of cogeneration landfill gas is mixed with natural gas in certain proportion. Combined heat and power plant is designed according to the Republic of Lithuania laws and regulations. Heat comes from cogeneration emissions into the atmosphere in summer. It was found that in order to increase the heat recovery efficiency, not only in winter but in summer, for example to be equipped with heated vegetable production complexes.

In the United States, 40% of energy use was for electricity generation in 2011, but two thirds of the energy used to produce electricity was lost as heat. Combined heat and power systems are an energy technology that provides electrical and thermal energy at high efficiencies by utilizing excess heat from the process of electricity generation. This technology can offer a decentralized method of energy generation for urban regions which can provide a more reliable, resilient and efficient power supply, and has a lower impact on the environment compared to certain centralized electricity generation systems. In order for the use of combined heat and power systems to become more widespread and mainstream, studies must be performed which analyze their use in various conditions and applications. This work examines the use of a combined heat and power system with a microturbine as the prime mover in residential and commercial scenarios and analyzes the technical and economic feasibility of various system configurations. Energy models are developed for R1, R6 and 2-story office building scenarios using eQUEST, and these results give the electrical and thermal energy requirements for each building. Combined heat and power system models are then developed and presented for each scenario, and the building energy requirements and system component sizes available are considered in order to determine the optimal configurations for each system. The combined heat and power system models designed for each scenario are analyzed to find energy savings, water impacts, and emissions impacts of the system, and each model is examined for economic and environmental feasibility. The models created provide information on the most technically and economically efficient configurations of combined heat and power systems for each scenario examined. Data on system component sizing, system efficiencies, and environmental impacts of each system were determined, as well as how these scenarios compared to the use of traditional centralized energy systems. Combined heat and power has the potential to significantly improve the resiliency, reliability and efficiency of the current energy system in the U.S., and by studying and modeling its uses we more completely understand its function in a range of scenarios and can deploy the systems in a greater number of environments and applications.

Micro-cogeneration is one of the technologies promoted as a response to the global call for the reduction of carbon emissions. Due to its recent application in the residential sector, the implications of its usage have not yet been fully explored, while at the same time, the available simulation tools are not designed for conducting research that focuses on the study of this technology. This thesis develops a virtual prototyping environment, using a dynamic multi-physics simulation tool. The model based procedure in its current form focuses on ICE based micro-CHP systems. In the process of developing the models, new approaches on general system, engine, heat exchanger, and dwelling thermal modelling are being introduced to cater for the special nature of the subject. The developed software is a unique modular simulation tool platform linking a number of independent energy generation systems, and presents a new approach in the study and design of the multi node distributed energy system (DES) with the option of further development into a real-time residential energy management system capable of reducing fuel consumption and CO2 emissions in the domestic sector. In the final chapters, the developed software is used to simulate various internal combustion engine based micro-CHP configurations in order to conclude on the system design characteristics, as well as the conditions, necessary to achieve a high technical, economic and environmental performance in the UK residential sector with the purpose of making micro- CHP a viable alternative to the conventional means of heat & power supply.

New technologies to converting heat into usable energy are constantly being developed for renewable use. This means that more interactions between different energy grid will be applied, such as utilizing low thermal waste heat to convert its energy to electricity. With high electricity price, such technology is quite attractive at applications that develop low waste heat. In the case of excess heat in district heating (DH) grid and the electricity price are high, the waste heat can be converted to electricity, which can bring a huge profit for DH companies. Candidate technologies are many and the focus in this degree rapport is on the so-called Organic Rankine Cycle (ORC) that belongs to the steam Rankine cycle. Instead of using water as a working fluid, organic working fluid is being used because of its ability to boil at lower temperature. Because this technique is available, it also needs to be optimized, developed, etc. to achieve the highest appropriate efficiency. This can be done, for example, by modeling different layouts, analyzing functionality, performance and / or do a simulation of various suitable working fluids.  This is the purpose of this degree project and the research parts are to select working fluids suitable at low temperatures (70-120) °C, the difference analysis between the selected fluids and identification of the parameters that most affect the performance. There are many suitable methods to apply to achieve desired results. The method used in this rapport degree is commercial software such as Mini REFPROP, CoolPack, Excel but the most important part is simulation with AspenPlus. The selected and suitable working fluids between the chosen temperature interval are R236ea, R600, R245fa and n-hexane. Three common layouts were investigated, and they are The Basic ORC, ORC with an internal heat exchanger (IHE) and regenerative ORC. The results show that in comparison between 120°C and 70°C as a temperature source and without an internal heat exchanger (IHE), R600 at 70°C, has the highest efficiency about 13.55%. At 110°C n-hexane has the highest efficiency about 18.10%. R236ea has the lowest efficiency 13.16% at 70°C and 16.29% at 110°C. R236ea kept its low efficiency through all results. Without an IHE and a source range from 70 °C up to almost 90 °C, R600 has the highest efficiency and at 90°C n-hexane has the highest efficiency. With an IHE and between (70-90) °C R245fa still has the highest efficiency. With or without IHE and a heat source of 110 °C n-hexane has the highest efficiency 18.10% and 18.40%. R236ea gets the greatest increase 5.2% in efficiency but remains with the lowest efficiency. With Regenerative ORC, n-hexane had an optimal middle pressure about 0.76 bar. The optimal pressure corresponds to a thermal efficiency of 17.52%. The most important identified parameters are the fluid characteristics such as higher critical temperature, temperature source, heat sink, application placement and component performance.         The current simulations have been run at some fixed data input such as isentropic efficiencies, no pressure drops, adiabatic conditions etc. It was therefore expected that the same efficiency curve would repeat itself. This efficiency pattern would differ with less or higher values depending on the layout performance. However, this pattern was up to 90 degrees Celsius and gets a very noticeable change by the change of the efficiency for n-hexane. Therefore n-hexane is chosen with Regenerative ORC because it had the highest efficiency at the highest temperature source tested. This is due definitive to the fluid properties like its high critical temperature compared to the other selected fluids. R236ea remains the worst and that’s also related to the fluid properties. It is also important to note that these efficiencies are only from a thermodynamic perspective and may differ when combining both thermal and economic perspectives as well as application placement. These high efficiencies will certainly be lower at more advanced or real processes due to various factors that affect performance. Factors such as component´s efficiency and selection, pipe type and size, etc. To maintain a constant temperature when it’s not, flow regulation is then necessary and that’s also affects the performance.   The conclusion is that the basic ORC which does not have an IHE and from 70 up to 90 degrees Celsius, R600 has the highest efficiency. Higher temperature gives n-hexane the highest efficiency. With an IHE and between (70-90) °C R254fa has the highest efficiency. At higher temperature source n-hexane has the highest efficiency. ORC with an IHE has the best performance. The R236ea has the worst performance through all results. With regenerative ORC, an optimal meddle-pressure for n-hexane is 0.76 bar. Important parameters are The properties of the fluid, temperature source, heatsink, Application placement and component performance. / Nej

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第17560号 / 工博第3719号 / 新制||工||1566(附属図書館) / 30326 / 京都大学大学院工学研究科航空宇宙工学専攻 / (主査)教授 吉田 英生, 教授 中部 主敬, 准教授 松本 充弘 / 学位規則第4条第1項該当

The main outcome of this research is the development of a Probabilistic Impact Assessment methodology to comprehensively understand the effects of low carbon technologies (LCTs) in low voltage (LV) distribution networks and the potential solutions available to increase their adoption. The adoption of LCTs by domestic customers is an alternative to decreasing carbon emissions. Given that these customers are connected to LV distribution networks, these assets are likely to face the first impacts of LCTs. Thus, to quantify these problems a Monte Carlo-based Probabilistic Impact Assessment methodology is proposed in this Thesis. This methodology embeds the uncertainties related to four LCTs (PV, EHPs, µCHP and EVs). Penetration levels as a percentage of houses with a particular LCT, ranging from 0 to 100% in steps of 10%, are investigated. Five minute time-series profiles and three-phase four-wire LV networks are adopted. Performance metrics related to voltage and congestion are computed for each of the 100 simulations per penetration level. Given the probabilistic nature of the approach, results can be used by decision makers to determine the occurrence of problems according to an acceptable probability of technical issues. To implement the proposed methodology, electrical models of real LV networks and high resolution profiles for loads and LCTs are also developed. Due to the historic passive nature of LV circuits, many Distribution Network Operators (DNOs) have no model for them. In most cases, the information is limited to Geographic Information Systems (GIS) typically produced for asset management purposes and sometimes with connectivity issues. Hence, this Thesis develops a methodology to transform GIS data into suitable computer-based models. In addition, thousands of residential load, PV, µCHP, EHP and EV profiles are created. These daily profiles have a resolution of five minutes. To understand the average behaviour of LCTs and their relationship with load profiles, the average peak demand is calculated for different numbers of loads with and without each LCT.The Probabilistic Impact Assessment methodology is applied over 25 UK LV networks (i.e., 128 feeders) for the four LCTs under analysis. Findings show that about half of the studied feeders are capable of having 100% of the houses with a given LCT. A regression analysis is carried out per LCT, to identify the relationships between the first occurrence of problems and key feeder parameters (length, number of customers, etc.). These results can be translated into lookup tables that can help DNOs produce preliminary and quick estimates of the LCT impacts on a particular feeder without performing detailed studies. To increase the adoption of LCTs in the feeders with problems, four solutions are investigated: feeder reinforcement, three-phase connection of LCTs, loop connection of LV feeders and implementation of OLTCs (on-load tap changers) in LV networks. All these solutions are embedded in the Probabilistic Impact Assessment. The technical and economic benefits of each of the solutions are quantified for the 25 networks implemented.

Fuel cell technology has reached commercialisation of fuel cells in application areas such as residential power systems, automobile engines and driving of industrial manufacturing processes. This thesis gives an overview of the current state of fuel cell-based technology research and development, introduces a μCHP system sizing strategy and proposes methods of improving on the implementation of residential fuel cell-based μCHP technology. The three methods of controlling residential μCHP systems discussed in this thesis project are heat-led, electricity-led and cost-minimizing control. Simulations of a typical HT PEMFC -based residential μCHP unit are conducted using these control strategies. A model of a residential μCHP system is formulated upon which these simulated tests are conducted. From these simulations, equations to model the costs of running a fuel-cell based μCHP system are proposed. Having developed equations to quantify the running costs of the proposed μCHP system a method for determining the ideal size of a μCHP system is developed. A sizing technique based on industrial CHP sizing practices is developed in which the running costs and capital costs of the residential μCHP system are utilised to determine the optimal size of the system. Residential thermal and electrical load profile data of a typical Danish household are used. Having simulated the system a practical implementation of the power electronics interface between the fuel cell and household grid is done. Two topologies are proposed for the power electronics interface a three-stage topology and a two-stage topology. The efficiencies of the overall systems of both topologies are determined. The system is connected to the grid so the output of each system is phase-shifted and DC injection, harmonic distortion, voltage range and frequency range are determined for both systems to determine compliance with grid standards. Deviations between simulated results and experimental results are recorded and discussed and relevant conclusions are drawn from these.

The aim of thesis entitled steam turbine is a condensing steam turbine with steam extraction, in twin-shaft implementation for municipal waste-incineration plant. The first part of the work is focused on the design used and the selected concept turbine. The second part is engaged in thermodynamic calculation of backpressure and condensing part. The end is devoted to technical – economic comparison with other possible conceptual variants.

This thesis is devoted to the construction of new waste-to-energy plants in a territory where is already another fossil-fuel power station in operation. The aim is to create a mathematical model and prove that those two devices are able to cooperate effectively using same technology. Exactly assembled model under real operating have characteristics of a mixed integer nonlinear programming. The optimization software GAMS is used for its calculation. The complexity of the model, however, is at a level that solutions in bad initial conditions ends in local optima, or not found at all. This thesis is devoted to the elimination of non-linearity using binary variables and heuristic so the task was solved with acceptable time limits to guarantee an optimal solution.

The Brista 1 plant is a wood chip-fired combined heat and power (CHP) plant located near Märsta, northwest of Stockholm, Sweden. The primary purpose of the plant is to supply heat to the northwest district heating grid. In order to meet increasing demand for district heating, Fortum Heat is constructing a second CHP plant next to Brista 1. The Brista 2 plant will use a mixture of municipal and industrial waste as fuel. Due to changes in the European Green Certificate program, the fuel subsidies for wood chips will be significantly reduced. This will cause the Brista 1 plant to incur significantly increased operating costs. The Brista 2 plant, however, will not be affected by these changes and will therefore be much cheaper to run than Brista 1. However, due to the large demand for district heating it will be necessary to run both plants in parallel at certain times in order to meet the heating demand and/or maximize revenue during periods of high electricity demand. A computer program has been constructed using MATLAB which simulates the Brista 1 and 2 plants and their combined operation in both backpressure and direct condensing mode. The results show that the optimum allocation of heat production does not seem to be affected by electricity price assuming both plants are operated in backpressure mode. The reason for this would seem to be that the production costs (fuel, emissions, O&M) are unaffected by the electricity price. Therefore, the allocation which maximizes electrical power production, and thus revenue from electricity sales, will always be favored. In certain cases, it is more profitable to run the Brista 1 plant in direct condensing mode. The reason for this would seem to be that the thermal efficiency is somewhat higher, and that at low electricity prices the revenues from electricity sales do not offset the cost of the reduced heat production.