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  • 101.
    bootun, chandrasekar
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. University of Mauritius.
    Energy Audit of Mauritian Industries2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Abstract

    Three companies namely Esko & Co Ltd, Cuttings Work Ltd and The Message Ltd were targeted for the purpose of this project study.

    The first one is Esko & Co Ltd. The company has diversified its production activities to produce sweets, bubble gums, chocolates, wafers and noodles both for the local market and export purposes.

    Cuttings Works Ltd is the second leading company in the manufacturing of top grade products using the best possible gemstones for the jewellery grade. The company is also diversifying and expanding its market.

    On the other hand ‘The message Ltd’ is another company involved in the designing and make up of high class casual wear. Previously the company was only designing and preparing samples and the bulk order done in another textile factory. With respect to the highly demanding market, they have now started the production of their shirts in-house.

    Being exposed to competition threats from other local and overseas suppliers, it is imperative for these factories to investigate on cost saving possibilities and process improvement opportunities. A walk-through audit was carried out where data were collected. The objective of the audit was to obtain energy savings through low cost improvements that optimise the building systems and process operation so that the companies operate efficiently and effectively. On the basis of observations and calculations, the following cost savings options can be suggested:’

    1. 1.       Savings on Fuel (HFO) used at Esko & Co Ltd.

    A saving on fuel consumed of MUR 458 572 [PH1] (Euro 11 464 based on exchange rate of Euro 1 = MUR40) per year can be achieved by recovering the heat loss through the flash steam for pre-heating the feed-water to the boiler. Another saving on fuel of MUR 105 578 (Euro 2639) per year can be done by recovering the heat loss from the Wafers machine exhaust. Also by recovering the heat loss from the boiler chimney exhaust a saving of MUR 137 457 (Euro 3436) per year can be achieved.

    1. 2.       Savings on Electrical components.

    It was found that in a big manufacturing company like Esko & Co Ltd, a direct saving of MUR13 278 (Euro 332) per year can easily be achieved by substituting the existing Fluorescent tube lights (18W) by 9W-T8 lamp with a return on investment of 2.8 years. However in smaller scale enterprise like The Message ltd and Cuttings Ltd, the shift on economic lamp can also lead to savings of MUR 3700 (Euro 92.5) and MUR 1386 (Euro 34.7) yearly.

    Most often large scale enterprise was found to be always paying a penalty fee for power factor. Hence the investment on an Automatic Correction Unit will also help doing savings. For instance, Esko & Co Ltd can save MUR 3200 (Euro 80) monthly on its electricity bill with a payback of 3.1 years for the power corrector unit.

    Next we noticed that big companies are used to a penalty fee for power factor. As this fee is for a period of six months for every month of excess power consumed, it is worth investing on an Automatic Power Correction unit. As such foe Esko & Co Ltd we found that a saving of MUR 3200 Euro 80) per month will be made with a payback period of 3.1 years for the equipment.

    Furthermore it was found that the power consumed by air conditioning units is quite significant. For instance for Esko & Co Ltd 33 % of the total power consumed are by the air conditioning units. A direct saving in this respect is achievable by only increasing the set point temperature by 1 to 2 oC. Other simple measures can be shading of windows to prevent sunlight or using wind curtains at doors and to switch on the AC when needed can largely help to decrease the air conditioning load However there is also room for future investment in variable speed drive for the compressors of the air conditioning units which is still costly at present.

    1. 3.       Steam leakage optimisation

    Reduction of steam leakage can be done by replacing the return condensate line from the oil heat exchanger at Esko& Co Ltd by a smaller one. It was not possible to calculate the savings as the leaks could not be measured – however results will show in the fuel bills.

    1. 4.       Reduction of heat dissipated

    Insulating the exhaust pipes from the Wafer machine at Esko& Co Ltd by using mineral wool of thickness 57mm will considerably decrease the heat dissipated to the surrounding by 80 % and hence improving the working environment around the machine since no air conditioner is found in that room. Air conditioning load in other rooms are expected to reduce and once again here it is difficult to conduct any calculations on how much can be saved. But by taking this measure the effects are immediately seen.

    1. 5.       Transport Fuel optimisation

    Normally big companies like Esko& Co Ltd which has many lorries for their product delivery that consume around 2330 litres of diesel monthly. As the transportation fuel is continuously increasing, this area also requires monitoring and optimisation. Simple measures like smooth driving, regular tuning and servicing of your engine can help improving the fuel economy of the company.

    1. 6.       Use of solar energy

    To alleviate the increasing world oil prices, the use of renewable energies are becoming important. As such we found that in a country like Mauritius where there is great potential for solar energy, the latter can be an option for companies to invest on. It was found that a grid connected system will be more advantageous and depending on an agreement with the local grid, a payback of less than 5 years can be achieved for a tariff around MUR 3 (Euro 0.08) per kWh.

    1. 7.       Avoided carbon dioxide emissions.

    To decrease the impact of global warming, it is important to cut down the emissions of greenhouse gases as it will be a serious threat to the third world countries and small island states in the first place as they are the most vulnerable. With the savings in the amount of HFO burned at Esko& Co Ltd, we found that the avoided amount of GHG emissions amounts to 98.96 kg CO2-e/year.

  • 102. Bose, A.
    et al.
    Raj, K.
    Kuzeva, D.
    Mura, T.
    Xin, J.
    Jayasuriya, Jeevan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Hybrid renewable power systems for generation of own power by small and medium-scale enterprises2018In: E3S Web of Conferences, EDP Sciences , 2018Conference paper (Refereed)
    Abstract [en]

    Decentralized power generation, from renewables, is an attractive option for the future energy transition. Through a case study, the techno-economic feasibility to produce own power from distributed renewable to de-carbonize the operations of the Small and Medium Scale Enterprises (SMEs) was critically analysed. The case study was performed on one of the leading printing outfits of Sri Lanka. Solar photovoltaic (PV) and biomass gasification systems are the most cost-efficient and easy to operate technologies for grid-connected, small-scale power generation, at present, for the context. Grid integration has been found as a major challenge, in both technical and economic parameters of the project. The low capacity factor of solar PV and complexity of the supply chain for biomass power systems are critical to the respective technologies. A hybrid Solar PV-Biomass gasification power plant would have superior techno-economic performances with lower environmental impact than stand-alone systems. An equal share of the net power capacity between the technologies was obtained as the most suitable combination for the proposed hybrid power plant. A net carbon dioxide reduction of more than eighty percent of the operations of the SMEs is feasible. Socio-political factors also have a high impact on overall viability of such small-scale systems.

  • 103.
    BOUE, Yoan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Functional model development for Multi-Purpose Crew Vehicle using EcosimPro2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Multi-Purpose Crew Vehicle (MPCV) is a spacecraft designed to carry men to the Moon and beyond. Developing such a spacecraft requires accurate numerical models. This work presents the development of such a model for the propulsion system of MPCV, with the software EcosimPro. The EcosimPro model of a spacecraft that is similar to MPCV is studied. Its results are compared with available flight data and its accuracy is assessed. Modifications are performed on this model in order to create the MPCV propulsion system model. The MPCV model is then used for performing functional propulsion analysis.

  • 104.
    Bron, Oliver
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. L.M.F.A., Ecole CentraleLyonFrance.
    Ferrand, P
    Fransson, T H
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Experimental and numerical study of nonlinear interactions in two-dimensional transonic nozzle flow2006In: UNSTEADY AERODYNAMICS, AEROACOUSTICS AND AEROELASTICITY OF TURBOMACHINES / [ed] Hall, KC Kielb, RE Thomas, JP, Ecole Cent Lyon, LMFA, Lyon, France. Royal Inst Technol, Heat & Power Technol, Stockholm, Sweden.: SPRINGER , 2006, p. 463-+Conference paper (Refereed)
    Abstract [en]

    A prerequisite for aeroelastic stability prediction in turbomachines is the understanding of the fluctuating aerodynamic forces acting on the blades. Unsteady transonic flows are complex because of mutual interactions between travelling pressure waves, outlet disturbances, shock motion, and fluctuating turbulent boundary layers. Complex phenomena appear in the shock/boundary layer region and produce phase lags and high time harmonics, which can give a significant contribution to the overall unsteady lift and moment, and therefore affect flatter boundaries, cause large local stresses, or even severely damage the turbo-machine. This paper is concerned with the understanding of phenomena associated with travelling waves in non-uniform transonic flows and how they affect the unsteady pressure distribution on the surface as well as the far field radiated sound. In similitude with turbomachines potential interaction, the emphasis was put on the unsteady interaction of upstream propagating acoustic waves with an oscillating shock in a 2D nozzle flow. Both numerical and experimental studies are carried out and compared with each other. Results showed that the unsteady pressure distribution results from the superposition of upstream and downstream propagating pressure waves, which are partly reflected or absorbed by the oscillating shock. Beside, the phase angle shift underneath the shock location was found to linearly increase with the perturbation frequency, which can be critical regarding aeroelastic stability since it might have a significant impact on the phase angle of the overall aerodynamic force acting on the blade and shift the aerodynamic damping from stable to exciting.

  • 105.
    BRUHAT, Jean-Frederic
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Aero-acoustic optimization of a swept fan2012Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This study deals with the aerodynamics and acoustics of modern transonic fans. Today, three-dimensional design techniques make possible the creation of fan blades with enhanced performance. This project investigates two of these techniques, the sweep and dihedral controls, and their influence on supersonic shock structures and blade performance. Simultaneously, the parameters influencing fan shock noise in the intake are examined.

     

    The first objective is to determine the consequences of a forward sweep on the fan performance. A series of analyses is thus carried out on a typical fan blade in order to assess the effect of a high negative sweep introduced in the tip section. Two blades with the same geometry, except for the tip section which is swept forward, are analyzed at high rotation regimes using CFD methods. The results show that the forward sweep blade has a significantly improved stall margin but an overall lower performance.

     

    In parallel, a CFD analysis is carried out to study the fan’s acoustics. The shock noise, mostly created in the tip section of the blades, is responsible for a large percentage of the noise coming out of the engine during takeoff and cruise. The objective is to understand the propagation of shock noise in the intake and isolate relevant parameters involved in the phenomenon. It is found that the shock noise level emitted is not proportional to the fan speed, as expected. This observation is counterintuitive and leads to search which variables are relevant for the analysis of the phenomenon. The angle the shock makes with the meridional axis is found to be influential on the outgoing noise level as well as the position of the shock on the blade. Finally, a model using the shock angle and aerodynamic variables to predict the noise levels is presented and support the CFD results.

  • 106.
    BUNDHOO, Jasbeersingh
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Analysis and application of maintenance strategies for Omnicane Thermal Energy Operations(St Aubin) Ltd2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Maintenance costs at Omnicane Thermal Energy Operations (St Aubin) Ltd contribute a significant part ofthe unit cost of electrical energy produced and affect the profitability of the power plant. Hence it is necessaryand crucial to minimize maintenance costs by optimizing maintenance processes to make the plant morereliable and to run economically.The total maintenance cost for OTEOSAL from year 2008 to 2011 is seen to be increasing and has evendouble from 2008 to 2011. The cost of external labor during operation has increased by nearly four times dueto a lot of breakdown on different equipments and also the value of the spare parts store is seen to risebecause many spare parts are bought at random in fear of having a shut down due to unavailability of spareparts. These excess expenses contribute to a loss in profitability. With a good maintenance strategy, the totalmaintenance cost can be reduced by about 30%.Fault Tree Analysis (FTA) and Failure Mode Effect Analysis (FMEA) were done and allowed identifyingcritical equipments at the power plant and the Grate Stocker, one of the most important and criticalequipment for the plant was selected to perform a Quantitative Analysis of the FTAs. The probability offailure for the Grate Stocker is seen to be 0.98 and has reliability as low as 0.02. Quantitative Analysis of FTAand Pareto Analysis will allow having the right quantity of spare parts at the right time without overstocking.From this thesis, it can be said that combining different maintenance and management methods andstrategies based on FTA, FMEA and Pareto Analysis and all these well formalized and documented accordingto ISO 9001 will certainly allow the power plant to gain a lot like availability, reliability and even financiallyfrom maintenance and also will make OTEOSAL ready for new challenges appearing in the energy sector inMauritius.

  • 107. Cabeza, Luisa F.
    et al.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Yan, Jinyue
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes. Mälardalen University, School of Business, Västerås, Sweden .
    Advances in energy storage research and development: The 12th International Conference on Energy Storage Innostock 20122013In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 109, p. 291-292Article in journal (Other academic)
  • 108.
    Cadiou, Gaëlle
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fluid Structure Interaction Simulation of a Cantilever Anemometer in OpenFoam2012Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    In the field of wind energy, structures containing flexible and flow adaptive elements are continuously developed. In this context, Fluid Structure Interaction (FSI) simulations provide an accurate support for the estimation of loads and the forecast of performances, by calculating interactions between the fluid and the solid domains.The present article investigates the structure and the numerical behavior of the FSI solver icoFsiFoam provided by the software OpenFoam, through the modeling of an existing cantilever anemometer. The aim of the work is hereby to isolate important parameters relative to icoFsiFoam and optimize them for the studied case.Various analyses demonstrate the sensitivity of the solver to parameters corresponding to the solid domain. In particular, the solid mesh and tolerance levels of the solid solver have a great impact on the simulation results. Further observations also show that the form of the discretized solid governing equation has an influence on the transient FSI simulation.

  • 109. Cai, Yixiao
    et al.
    Xia, Chen
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Wang, Baoyuan
    Zhang, Wei
    Wang, Yi
    Zhu, Bin
    KTH, School of Computer Science and Communication (CSC), Media Technology and Interaction Design, MID.
    Bioderived Calcite as Electrolyte for Solid Oxide Fuel Cells: A Strategy toward Utilization of Waste Shells2017In: ACS SUSTAINABLE CHEMISTRY & ENGINEERING, ISSN 2168-0485, Vol. 5, no 11, p. 10387-10395Article in journal (Refereed)
    Abstract [en]

    The excessive consumption of synthesized materials and enhanced environmental protection protocols necessitate the exploitation of desirable functionalities to handle our solid waste. Through a simple calcination and composite strategy, this work envisages the first application of biocalcite derived from the waste of crayfish shells as an electrolyte for solid oxide fuel cells (SOFCs), which demonstrates encouraging performances within a low temperature range of 450-550 degrees C. The single cell device, assembled from calcined waste shells at 600 degrees C (CWS600), enables a peak power density of 166 mW cm(-2) at 550 degrees C, and further renders 330 and 256 mW cm(-2) after compositing with perovskite La0.6Sr0.4Co0.8Fe0.2O3-delta (LSCF) and layer-structured LiNi0.8Co0.15Al0.05O2 (LNCA), respectively. Notably, an oxygen-ion blocking fuel cell is used to confirm the proton-conducting property of CWS600 associated electrolytes. The practical potential of the prepared fuel cells is also validated when the cell voltage of the cell is kept constant value over 10 h during a galvanostatic operation using a CWS600-LSCF electrolyte. These interesting findings may increase the likelihood of transforming our solid municipal waste into electrochemical energy devices, and also importantly, provide an underlying approach for discovering novel electrolytes for low-temperature SOFCs.

  • 110.
    Calianno, Luca
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    SENSITIVITY STUDIES ON THE THERMAL MODEL OF A SOLAR STEAM TURBINE2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the past, steam turbines were mostly used for base load operation. Nowadays, with the increased development of variable renewable technologies, these same steam turbines are withstanding higher cyclic operational regimes with more frequent start-ups and fast changing loads. As such, improving the operational flexibility of installed and future designed steam turbines is a key aspect to be considered by equipment manufacturers.

    Steam turbine start-up is a phase of particular interest since is considered to be the most intricate of transient operations. During this phase, the machine can potentially be subjected to excessive thermal stresses and axial rubbing due to differential thermal expansion. These two thermal phenomena either consume component lifetime or can lead to machine failure if not carefully controlled. As such, there is a balance to be considered between increasing turbine start-up speed while ensuring the safe operation and life preservation of these machines.

    In order to improve the transient operation of steam turbines, it becomes important to examine their thermal behavior during start-up operation. To do that, it is important to have tools able to predict the thermal response of the machine. In this thesis work the impact of different aspects and boundary conditions on the results of ST3M, a KTH in-house tool, were investigated with the aim of understanding how large was their impact on the way to capture the thermal behavior of the turbine in terms of metal temperature and differential expansion. A small industrial high pressure turbine was validated against measured data and implemented on a sensitivity study; this analysis showed that the geometrical approximation introduce errors in the results, that the use of empirical Nusselt correlations give similar results to the validated model and that the cavity assumptions have a large impact on the trend of the differential expansion. Lastly, a strategy to validate any other similar turbine to the one of the study case was proposed in order to give a guide to future works in how to validate a model and what are the most influent parameters to take care of.

  • 111.
    Camacho Ureña, Pedro Manuel
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Integration of ASOFC with Gasification for Polygeneration2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Solid Oxide fuel cells (SOFC), is one of the fuel cell types with a greater potential as a commercial electrical power generator. As a high temperature fuel cell type (600-1000ºC), presents one of the biggest opportunity to be integrated in a polygeneration system combining it with existing infrastructure to provide heat and power in a efficient way. Furthermore, unlike other types of fuel cells, SOFC can work using a wide variety of fuels, meaning that with some reformation; most of the commercially available fuels can be utilized, and even some relatively sustainable fuels that are not yet commercial, such as gasified biomass.

    The main part of this thesis focuses on the design of two gasifier models, one for partial oxidation gasification and other for steam gasification, both models where verified using published experimental results and simulations. Afterwards the models were integrated to work with a SOFC system. Several key parameters where analyzed in other have a complete view of the behavior of the system. The system was studied by changing different parameters like fuel cell operating temperature, fuel cell operating pressure, fuel composition, and moisture content.

    Finally another part of the thesis is to analyze two different systems, one integrating gasifier and SOFC, and other studying the integration of the gasifier system to a combine cycle system, SOFC-Micro Gas Turbine.

    The study concludes, as expected, that there is an inverse correlation between the moisture level in the fuel and the efficiencies in all the systems. Also the model shows that increasing the cell operating temperature will reduce the number of cell needed in order to achieve the design power output.

  • 112.
    Camara, Enrique
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Validation of Time Domain Flutter PredictionTool with Experimental Results2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In turbomachinery applications as propulsion and power generation, there is a continuous endeavour to design engines with higher efficiency, driving the compressor and turbine blades towards slimmer and more aerodynamically loaded configurations that frequently operate with fluids at higher temperatures and speeds. This combination of reduced design space and adverse operating environment makes the blades more susceptible to flutter and challenges the designer to predict its occurrence.

    Nowadays there are different CFD solvers that allow the prediction of flutter in turbomachinery; some of them are more efficient than others and provide considerable computational power savings when compared with traditional CFD methods that sometimes require the simulation of several or all the blades in a given row.

    The present thesis work is aimed at investigating the strengths and potential limitations of a novel time marching method for Flutter prediction in the Travelling Wave Mode (TWM) domain available in ANSYS CFX 14.5. The results are compared with experimental measurements obtained at the KTH test rig and CFD simulations in the Influence Coefficient Domain (INFC) performed in a previous MSc. Thesis in 2013.

    An approach in CFX to solve flutter is the Fourier Transformation method that uses only two passages with phase lagged periodic boundary conditions. In the previous thesis only one operating point was calculated using this method. This project focuses on the extension of the calculations to various operating points and expanding the solver validation.

  • 113.
    Cardozo, Evelyn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Combustion of agricultural residues: Application for Stirling micro-combined heat and power2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Access to energy services is crucial for the development of countries. Therefore, in developing countries, the access to modern conversion technologies would contribute to reduce the poverty, improve health services and promote the economy especially in rural areas. Around 2.5 billion people in these countries use biomass for cooking. However, major concerns are due to the unsustainable use of biomass and the inefficient conversion technologies employed in rural areas. Therefore, the use of locally available biomass in modern biomass conversion technologies would significantly reduce emissions and improve the energy efficiency. These modern technologies may include residential pellet stoves and boilers which at the moment only are used for heating appliances in industrialized countries. Their combination with a prime mover like a Stirling engine could a very attractive solution to produce combined heat and power (CHP) though still in prototype stage. In this context, this study is mainly focused on the development of an energy system fuelled by locally available biomass to produce heat and electricity based on a Stirling engine. The main objective is to perform experiments to find relevant parameters that characterize the energy system proposed.

    In the first stage of this work, the suitability of using agricultural residues in a pellet boiler was evaluated in comparison to commercial wood pellets. The agricultural residues used during the tests were: sugar cane bagasse, sunflower husks and Brazil nut shells. The first two residues were pelletized and the last one was reduced to a uniform size. Parameters and energy used during the pelletizing were found. Emission levels and boiler efficiency under steady-state and transient conditions were also presented for the different biomass sorts. In the second stage, the integration of the same pellet burner and the Stirling engine was characterized in terms of losses and efficiency calculations. Finally, the integration of the pelletizing, combustion, and heat and power generation was discussed based on experimental and predicted results.

  • 114.
    Cardozo, Evelyn
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Erlich, Catharina
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Alejo, Lucio
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Thermal power analysis of flue gases during the combustion of agricultural residues in a residential pellet boilerManuscript (preprint) (Other academic)
  • 115.
    Cardozo, Evelyn
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Erlich, Catharina
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Malmquist, Anders
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Alejo, Lucio
    An experimental study of a Stirling engine micro-CHP system fuelled on wood and sugarcane bagasse pelletsManuscript (preprint) (Other academic)
  • 116.
    Cardozo, Evelyn
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. Universidad Mayor de San Simón, Bolivia .
    Erlich, Catharina
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Malmquist, Anders
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Alejo, Lucio
    Integration of a wood pellet burner and a Stirling engine to produce residential heat and power2014In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 73, no 1, p. 669-678Article in journal (Refereed)
    Abstract [en]

    The integration a Stirling engine with a pellet burner is a promising alternative to produce heat and power for residential use. In this context, this study is focused on the experimental evaluation of the integration of a 20 kWth wood pellet burner and a 1 kWe Stirling engine. The thermal power not absorbed by the engine is used to produce hot water. The evaluation highlights the effects of pellet type, combustion chamber length and cycling operation on the Stirling engine temperatures and thermal power absorbed. The results show that the position of the Stirling engine is highly relevant in order to utilize as much as possible of the radiative heat from the burner. Within this study, only a 5 cm distance change between the Stirling engine and the pellet burner could result in an increase of almost 100 °C in the hot side of the engine. However, at a larger distance, the temperature of the hot side is almost unchanged suggesting dominating convective heat transfer from the hot flue gas. Ash accumulation decreases the temperature of the hot side of the engine after some cycles of operation when a commercial pellet burner is integrated. The temperature ratio, which is the relation between the minimum and maximum temperatures of the engine, decreases when using Ø8 mm wood pellets in comparison to Ø6 mm pellets due to higher measured temperatures on the hot side of the engine. Therefore, the amount of heat supplied to the engine is increased for Ø8 mm wood pellets. The effectiveness of the engine regenerator is increased at higher pressures. The relation between temperature of the hot side end and thermal power absorbed by the Stirling engine is nearly linear between 500 °C and 660 °C. Higher pressure inside the Stirling engine has a positive effect on the thermal power output. Both the chemical and thermal losses increase somewhat when integrating a Stirling engine in comparison to a stand-alone boiler for only heat production. The overall efficiency of the pellets fired Stirling engine system reached 72%.

  • 117.
    Cardozo, Evelyn
    et al.
    Univ Mayor San Simon, Fac Ciencias & Tecnol, Cochabamba, Bolivia.
    Malmquist, Anders
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Performance comparison between the use of wood and sugarcane bagasse pellets in a Stirling engine micro-CHP system2019In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 159, article id 113945Article in journal (Refereed)
    Abstract [en]

    The use of locally available agricultural residues is an interesting alternative for residential heat and power generation based on the Stirling engine technology. However, some biomass with high ash content (agricultural residues) may cause operational problems and impact on the performance of the Stirling engine and the overall CHP system. This work is focused on the evaluation of useful parameters of a CHP system based on a 20 kW(th) pellet burner, a 1 kW(e) Stirling engine and a 20 kW(th) residential boiler using wood and sugar cane bagasse pellets. Similar temperatures in the Stirling hot end were found when using both fuels under steady-state and transient conditions. CO emission levels when using bagasse were lower than for wood pellets but slightly higher levels of NOx and higher accumulated ash were found. A fouling factor of the Stirling heat exchanger was found to be around 1.1 m(2) degrees C/kW after two cycles (6 h) and 3.2 m(2) degrees C/kW after three cycles (9 h) of operation when using wood pellets. A linear relation between the Stirling power output and the accumulated ash was assessed which was used to predict a longer operation time using bagasse pellets. This shows that after three cycles of operation with bagasse pellets, without removing accumulated ash, the CHP efficiency is still kept over 83% and for wood pellets, the CHP efficiency was kept over 90%.

  • 118.
    Cardozo Rocabado, Evelyn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Energy Situation in Bolivia and Biomass CHP Technologies2010Report (Other academic)
  • 119.
    Cardozo Rocabado, Evelyn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Pelletizing study of agricultural residues: Parameters and energy consumption2011Report (Other academic)
  • 120.
    Cardozo Rocabado, Evelyn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Uncertainty analysis: Measured parameters in combustion tests2012Report (Other academic)
  • 121.
    Cardozo Rocabado, Evelyn
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. Facultad de Ciencias y Tecnología (FCyT), Universidad Mayor de San Simon (UMSS), Cochabamba, Bolivia.
    Erlich, Catharina
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Alejo, Lucio
    Universidad Mayor de San Simon.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Combustion of agricultural residues: An experimental study for small-scale applications2014In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 115, p. 778-787Article in journal (Refereed)
    Abstract [en]

    Energy services could be greatly improved by using of residues from local food industries in small-scale combustion units. Wood pellets are a reliant and proven fuel to be used in small-scale combustion units. However, these units should preferably be able to use different types of biomass depending what it is locally available. Therefore, studies have been focused on exploring the suitability of using agricultural residues for small-scale heat and power generation using direct combustion. This study targets to compare the combustion of different agricultural residues in a single unit designed for wood pellets. The different biomass fuels used are circle divide 6 mm and circle divide 8 mmwood pellets, circle divide 6 mmbagasse pellets, circle divide 6 mmsunflower husk (SFH) pellets and Brazil nut (BN) shells. The results reveal a decrease in the fuel power input, higher oxygen levels in the flue gases and shorter cycles for ash removal when using the agricultural residues. The excess air ratio was calculated based on a mass balance and compared with a standard equation showing a good agreement. CO and NO emission levels as well as the relative conversion of fuel-C to CO were higher for the BN shells and SFH pellets in comparison to the other biomass types. SO2 emission was estimated based on the analysis of unburned sulfur in ash and mass balances; the higher estimated levels corresponded to the BN shells and SFH pellets. All the biomass sorts presented over 95% relative conversion of fuel-C to CO2. Wood pellets and BN shells presented the highest amount of unburned carbon in ash relative to the fuel-C. The relative conversion of fuel-N to NO and fuel-S to SO2 were higher for wood pellets. Bagasse pellets showed similar emission levels and relative conversion efficiency to wood pellets.

  • 122.
    Cardozo Rocabado, Evelyn
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Erlich, Catharina
    Alejo, Lucio
    Fransson, Torsten H.
    Comparison of the thermal power availability of different agricultural residues using a residential boiler2016In: BIOMASS CONVERSION AND BIOREFINERY, ISSN 2190-6815, Vol. 6, no 4, p. 435-447Article in journal (Refereed)
    Abstract [en]

    This study presents a comparison of combustion performance, losses, and efficiency at steady-state and transient conditions for different biomass types in a residential boiler. The types of biomass used were 6 and 8 mm wood pellets, 6 mm sugarcane bagasse pellets, 6 mm sunflower husk pellets, and Brazil nut shells. The comparison in the development of the temperature in the combustion chamber during the start-up revealed that the 6 mm wood pellets ignite and propagate faster than the rest of the biomass fuels due to their smaller size compared with 8 mm wood pellets and lower ash content compared with the rest of the biomass sorts. Thermal power output and efficiencies under steady-state and transient conditions were calculated by the direct method, i.e., by measuring the heat recovery by the water boiler, and the indirect method, i.e., by measuring the heat losses. By using the indirect method, the availability of the flue gas thermal power during the start-up was seen more in detail than when the other method was applied. When comparing both methods as tools for boiler efficiency evaluation for different fuel types, the discrepancy of the resulting efficiencies between is larger when there are higher amounts of chemical losses in the boiler. Therefore, this method shows good agreement also for bagasse pellets but is, without modification, proposed not to be valid for fuels emitting higher amount of carbon monoxide (CO). Boiler efficiencies reached class 3 boilers according to EN 303-5 (> 74.8 %) for all biomass sorts.

  • 123.
    Carlberg, Marcus
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Quantify Change in Wind Turbine Power Performance Using Only SCADA Data2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The power performance characteristic of a wind turbine is defined by its power curve and resulting estimate in annual energy production. It is a key attribute for validating the performance of newly installed wind turbines, and the power curve is monitored throughout the wind turbine life cycle. This report explains power performance, upgrading, and conventional measurement methods.

    Wind farm stakeholders are keen on understanding the power performance of their wind turbines. The manufacturers’ monitoring software allows the power curve to be tracked in real time. Deviations from normal operation and underperformance can quickly be identified. However, these power curves cannot be trusted for evaluating upgrades and particular changes made to the wind turbine. The power curve is highly sensitive to small deviations in wind speed output of the nacelle anemometer. Upgrades which impact the air flow at the nacelle will introduce significant wind speed bias in such power curves. Thus owners are lacking appropriate tools for evaluating past events’ impact on power performance.

    The focus of this work lies on testing an alternative approach to measuring change in power performance using only historical wind turbine log data. Side-by-Side Testing as explained by Axel Albers was tested on real wind turbine data. This method uses no wind measurements, but instead simulates the wind speed using a deducted power relation to a neighbouring wind turbine and an assumed power curve behaviour. This allows any change in power output to be tracked onto the power curve, relying only on power output measurements.

    A full power performance analysis was performed by constructing Side-by-Side Testing in Microsoft Excel exclusively for this MSc thesis work.  It was applied on a wind farm whose recent blade upgrade had never before been analysed. Two neighbouring identical 2.3 MW wind turbines were considered for the analysis, one which in May 2013 installed blade add-ons featuring serrated trailing edges to the blades. The analysis was executed completely off site.

    The power performance analysis was completed, producing meaningful results with known uncertainty levels. The test results indicate an improvement of power performance throughout the power curve, corresponding to an increase of 0.53% in annual energy production, at ±1.35% uncertainty. The analysis needs further work and validation, as the power curve shows signs of artefacts. The complex wind farm settings increase the uncertainty levels. The method could likely be tested in flat terrain or offshore with lower uncertainty of results, targeting below ±0.5% uncertainty in annual energy production.

  • 124.
    Carlqvist, Anneli
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    MSc Thesis Guide2011Report (Other (popular science, discussion, etc.))
    Abstract [en]

    The scientific research is the performing of a methodical study in order to prove a hypothesis or to provide a solution to a specific question/problem. A hypothesis is the statement created by a researcher when he/she speculates upon the outcome of a research or experiment, requiring some kind of interpretation and an opinion from the researcher regardless of the field of study.

    In order to prove the hypothesis or to find a solution to the specific problem one has to follow a systematic series of steps. In scientific research generally a variable/s must be identified and are to be manipulated in order to achieve the desired objectives.

  • 125.
    Carlqvist, Anneli
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Overview of Concentrating Solar Power for Electricity Production, with Emphasis on Steam Turbine Aspects2009Report (Refereed)
    Abstract [en]

    The European Union targets a reduction of greenhouse gas emissions by 20% of renewable energy sources in the EU energy mix by 2020. New generations of technologies have to be developed through breakthroughs in research if the vision is to be met. The deregulation of the electric power market has opened the market to investors seeking profits and growth via the installation of additional capacity. This literature review report is a introductory step towards a more detailed and targeted work for a system concept evaluation, analysis and optimization of solar turbines in concentrating solar thermal power production. Concentrating Solar Power (CSP) has grown in recent years to be the largest bulk producer of solar electricity in the world and every square meter of a CSP field that produces 400 - 500 kWh of electricity per year, saves 0,45 ton of CO

    2and contributes to a 0,1 ton reduction of fossil fuels use annually. The CSP is divided in two concepts and three main technologies: Linear– and point focus concept; Parabolic trough -, Power Tower- and dish- Stirling engine technologies. Whereas the Power Tower technology has the best gross efficiency, the parabolic trough has the advantage to be the most mature technology, being in grid connected power plant operation for at least two decades. Dish-Stirling engine systems have the highest net efficiency but suffer from the sensibility to insolation fluctuations and lack of storage. There are various thermal storage medias and storage concepts to help achieving the best thermal characteristics for charging and discharging to the CSP technology in question. The dispatch time ranges from 0,5 hour for maintenance and service up to 16-24 hours thermal energy dispatchability. The most recently commercialized thermal storage media is phase change material, i.e. salt mixtures with good thermal characteristics. Research for other kind of media suitable for CSP-technology is performed continuously. The operation modes of a CSP plant depends on the choice of electricity production; dispatch electricity during day-time hours or prolonging the electricity production beyond sunset. The Organic Rankine Cycle (ORC) is another CSP concept using organic thermal fluid instead of steam to the turbine, at a lower temperature and pressure range. The power output is of range 1–5 MW for electricity production. The ORC ability to use simpler components and the possibility to deployment in rural areas as well as on limited space in urban areas, make it more economical feasible. The organic fluid is for example n-pentane and toluene. The net efficiency for ORC-plants has been proven to achieve 30% under optimal conditions, comparing to the Rankine cycle practical efficiency of 36-40 %. The experiences from CSP plant operation have raised a demand for improvement of the steam turbine’s work performance. The steam turbine has until recently being designed to be in continuous work. The steam turbine operating in solar thermal plants should have the capability to start up directly and go from idle to rated condition in a matter of minutes. The CSP-plant start-ups per year is higher where the cycling thermal stresses can cause material fatigue leading to shorter life time. Efficient collector, storage design and optimal turbine operation should reduce the number of start-ups and shutdowns per year and the transient loads on the steam turbine.

  • 126.
    Carlqvist, Anneli
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Proposal of new course description, Renewable Technology, RET I & II2011Other (Other (popular science, discussion, etc.))
    Abstract [en]

    After three years of experience the work outcome in RET II and as a result of a KTH course taken in "Teaching and learning in higher education, LU1", an evaluation of the educational material of solar part of the RET I and RET II course was done. The intention was to investigate the lecture content and the relation of the assignments given.

    The report is discussing the educational material and learning activities of the solar technology of the RET I and RET II with emphasis on the alignment of the two courses where RET I is the basic course managing the fundamentals of the topic, and RET II is the natural step up from the basic course, managing the more advanced issues of the same topic. The work does not consider the lecturers activities as for knowledge, competence or performance.

    The main objective is to suggest new course descriptions for RET I and RET II with better alignment between the courses and within the courses’ work tasks as for educational material and learning activities. The goal is to get a coherent educational content that gives the students a stepwise increasing level of knowledge of the area of topic and to achieve a higher learning quality and quantity. Three years of supervising the student assignments has resulted in a basis of evaluation material. A course in "Teaching and learning in higher education" at KTH provided material, ideas and possibilities to develop a new course description.

    The result is two course structures of the solar technology component in RET I and RET II. RET I aims to focus on the solar fundamentals and low temperature solar thermal and PV applications for domestic use. RET II would thereafter focus on high temperature solar thermal and Photovoltaic applications for larger system applications. The social and economical view would also be an addition to a more elaborate solar technology course.

    The mandatory submitting work tasks are the assignments. In RET, the exercises, study visits and assessments are all a part of the aligned learning content the students have individual responsible for, to perform in order to be successful at the exam. The assessment can be passed at submitting, keeping track of the student’s study advancement and activity. The study visits are meant to be of flat plate and PV/parabolic solar collectors that are already on the market.

    The RET II course is more demanding than the RET I course, where the components are spanning over several separate but related topics. The study visit is replaced by a project assignment, where the students have to practice their achieved knowledge from RET I and RET II

  • 127.
    Carrasco Mora, Enrique
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Variable Stator Nozzle Angle Control in a Turbocharger Inlet2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Turbochargers are becoming an essential device in internal combustion engines as they boost the intake air with more pressure in order to increase the power output. These devices are normally designed for a single steady design point but the pulsating flow delivered from the internal combustion engine is everything but steady. The efficiency drop experienced in the off-design points by the fixed geometry turbochargers have made some research groups to look into new variable geometry solutions for turbocharging.

    A nozzle ring is a device which normally achieves a higher performance under design conditions, but the efficiency rapidly drops at off-design conditions. In this paper, a variable angle nozzle ring is designed and implemented in the model of a radial turbine of a turbocharger in order to study its potential when working under real internal combustion engine cycles. To understand the profit margin the turbine performance is compared with two turbines with the same impeller geometry: one without nozzle ring and one with a nozzle ring with a fixed angle.

    The results show that the maximum efficiency angle function calculated for the variable angle nozzle ring achieves an improvement in the total efficiency of 5 % when comparing with a turbine with a fixed angle and 18 % when comparing with a vaneless turbine. The improved guidance achieved due to the variable blade angle leads to less turbine losses and therefore more mechanical energy can be extracted from the exhaust mass flow throughout all the combustion cycle but a further study should be made in order to match all the engine operations points. Notably, taking the pulsating boundary conditions into consideration, a remarkable improvement is achieved already for the fixed angle nozzle ring. 

  • 128.
    Castillo Ochoa, Luis Ramon
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Techno-economic Analysis of Combined Hybrid Concentrating Solar and Photovoltaic Power Plants: a case study for optimizing solar energy integration into the South African electricity grid2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The cooperation between large scale Concentrated Solar Power plants (CSP) and Solar Photovoltaic (PV) parks can offer stability in power supply and enhance the capacity factor of the CSP plant intended to cover a common demand on the power system. Moreover, it can offer an investment option with lower risk. This Master thesis project presents optimum plant configurations for both technologies under the same meteorological and market conditions. The study is based in the South African electricity market and the Renewable Energy Independent Power Producer Program currently in place in the country. Using MATLAB and TRNSYS softwares, a series of detailed codes were designed in order to model both technologies energy transformation process. The main approach was to design the nominal operation point of both technologies for a given typical meteorological year data and respective technical conditions for each case. Then, a transient simulation was done in order to obtain the electricity yield. The intention was to measure the internal rate of return, levelized cost of electricity and capacity factor for each technology and the combined configuration (CSP-PV plant) under different scenarios and operation modes while a firm capacity was maintained. It was found that the plants can be economically feasible by sizing a storage unit capable of just covering the peak hours. The solar multiple sizes can vary depending on the scenario and plant configuration. Moreover, the internal rate of return increases with the capacity of the CSP in all cases. After the results were obtained, a comparison with a single CSP plant and the optimum CSP-PV plant was done in order to evaluate the performance of the proposed cooperation. Even though the internal rate of return of the CSP-PV plant was found to be within a good range for investment, the CSP-alone alternative offered always higher internal rate of return and lower levelized cost of electricity values. Nonetheless, it was found that the capacity factor of the combined configuration was favored by the integration of PV. The PV alone configuration hold the lowest levelized cost of electricity, thus considered the best option for and investment in South Africa due to its independence towards incentives. Combined PV-CSP systems were also found to be an attractive investment under the South African scheme if the CSP capacity is similar to the PV power plant.

  • 129.
    Castro Flores, José Fiacro
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. IMT Atlantique (École des Mines de Nantes - EMN), Energy Systems and Environment - DSEE.
    Low-temperature based thermal micro-grids: operation and performance assessments2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Energy use in the urban environment is vital for the proper functioning of our society, and in particular, comfort heating –or cooling– is a central element of our energy system often taken for granted. Within this context, district energy systems and especially, district heating (DH) systems must evolve to adapt to the upcoming decades-long transition towards a sustainable energy system. This dissertation seeks to introduce, discuss, and assess from a techno-economic perspective the concept of low-temperature (LT) based thermal micro-grids (subnets) as active distribution thermal networks. It explores the role of the subnet at the system distribution level supervised by an active agent (DH substation), performing tasks of heat supply and demand management (storage and dispatch), as well as coordinating bidirectional flows.

     

    Here, a mixed methodological approach based on analytical simulation for the assessment of alternatives to evaluate a set of technologies is developed and discussed. This approach covers: the identification of knowledge gaps through the state-of-the-art analysis; a collection of incremental technical and/or economic performance assessments; and the analysis of a measurement data set from an existing LTDH demonstration project.

     

    Key findings of this work include: an updated and improved model of aggregated heat loads; identification of differences in load and temperature patterns for certain LT subnets; analysis of benefits and drawbacks of active substations with distributed heat sources and/or storage; and the impact on the reduction of the primary network return temperature as a consequence of the increase in the share of LT subnets, leading to lower generation and operating costs.

     

    These outcomes reveal that the integrated design and operation of the active thermal micro-grid have the potential to improve both the performance of the subnet, and that of the primary network. It further enhances the capability of the overall system to integrate unconventional and distributed heat sources together with energy efficient buildings by increasing the system’s flexibility and controllability. Active thermal distribution networks will likely become a subsequent step in the technological development of DH technologies, to address the matter of providing comfort heating in an effective and cost-efficient manner. This work advances the current DH knowledge by identifying synergies and challenges that arise with these new developments, in order for DH technology to play a key role in the future smart and sustainable energy system.

  • 130.
    Castro Flores, José Fiacro
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. École des Mines de Nantes - EMN, Energy Systems and Environment - DSEE.
    Chiu, NingWei Justin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Lacarrière, Bruno
    École des Mines de Nantes - EMN, Energy Systems and Environment - DSEE.
    Le Corre, Olivier
    École des Mines de Nantes - EMN, Energy Systems and Environment - DSEE.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Conceptual study of a solar-assisted low-temperature district heating substation2015In: Book of abstracts: International Conference on Smart EnergySystems and 4th Generation District Heating: Low-temperature district heating and buildings / [ed] Lund, H. (Ed.), & Mathiesen, B. V., Copenhagen, DK: Aalborg Universitetsforlag, 2015Conference paper (Refereed)
    Abstract [en]

    At present, the viability of Low-Temperature District Heating (LTDH) systems has already been tested and demonstrated. Even so, for LTDH to be successfully implemented, further ideas are needed in order to improve the flexibility and effectiveness. In this study, we analyze the performance of a local LTDH network for a multi-dwelling low-energy building supplied by both a roof-mounted solar collector and the conventional DH network via a LTDH substation. The DH network serves as a short-term storage buffer, so no heat storages are required. The collector’s size is chosen based on the available roof area, independently from the building’s loads, and three possible connection configurations were simulated. A mix of both the existing DH forward and return flows are used as thermal energy sources. The results show that more than 15% of the summer heat demand in the LTDH network can be covered by the roof-mounted solar collector. With a feed-in contract, heat costs savings range 3-6% annually according to the Swedish system. System integration in LTDH from the design phase has the potential to enhance the recovery of solar thermal energy, increase its conversion efficiency, and in general, to improve the utilization of low-grade thermal energy sources.

  • 131.
    Castro Flores, José Fiacro
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. École des Mines de Nantes - EMN, Energy Systems and Environment - DSEE.
    Chiu, NingWei Justin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Le Corre, Olivier
    École des Mines de Nantes - EMN, Energy Systems and Environment - DSEE.
    Lacarrière, Bruno
    École des Mines de Nantes - EMN, Energy Systems and Environment - DSEE.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Energetic and exergetic analysis of alternative low-temperature based district heating substation arrangements2016In: International Journal of Thermodynamics, ISSN 1301-9724, Vol. 19, no 2, p. 71-80Article in journal (Refereed)
    Abstract [en]

    District Heating (DH) technology is an efficient and cost-effective solution to provide heating services to the built environment. However, the existing DH technology may not be technically and economically effective to service buildings with low energy demands. Here, low-temperature based district heating (LTDH) can provide a better match between supply and demand in terms of energy quality and quantity. This paper deals with the energy and exergy analyses of a LTDH substation supplying a secondary LTDH network as a subnet of the existing DH system. In order to improve the temperature match, a mix of supply and return streams from the main DH network are used to supply the substation. Based on modelling and simulation, an energy and exergy analysis is employed to compare the performance of two proposed substation configurations to that of a conventional DH substation operating at low temperatures. The results of this analysis show that the proposed LTDH substation reduced the share of energy demand covered by the main DH supply by 20% to 25%. Likewise, by using the flow from the main DH return pipe, the final exergy efficiency of the overall system increased by 5% on average. The exergy destruction occurring at the system components was also identified and compared: during high heat demands the substation heat exchanger is responsible for the largest share of exergy destruction, whereas for low heat demands, it is due to the pumping effort. Based on these results, the proposed system is seen as an effective approach to increase the quality and quantity match between the low-temperature network and the conventional supply.

  • 132.
    Castro Flores, José Fiacro
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. École des Mines de Nantes - EMN, Energy Systems and Environment - DSEE.
    Lacarrière, Bruno
    École des Mines de Nantes - EMN, Energy Systems and Environment - DSEE.
    Chiu, NingWei Justin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Assessing the techno-economic impact of low-temperature subnets in conventional district heating networks2017In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 116, no C, p. 260-272Article in journal (Refereed)
    Abstract [en]

    The 4th generation Low-Temperature District Heating (LTDH) is envisioned as a more efficient and environmentally friendly solution to provide heating services to the building stock. Specifically, in countries already with a large share of well-established DH systems, conventional DH and LTDH technologies will be operating simultaneously in the near future. Newly built or refurbished buildings have lower heat demands, which in combination with LTDH brings potential savings compared to conventional DH. This work explores the advantages in DH operation by connecting these loads via LTDH subnets to a conventional DH system, supplied by a Combined Heat and Power (CHP) plant. A techno-economic analysis was performed, through modelling and simulation, by estimating the annual DH operating costs and revenues achieved by the reduction in return temperatures that LTDH would bring. The savings are related to: (1) the reduction in distribution heat losses in the return pipe; and (2) lower pumping power demand. Likewise, additional revenues are assessed from: (3) improved Power-to-Heat ratio for electricity production; and (4) enhanced heat recovery through Flue Gas Condensation (FGC). The annual savings per kWh of delivered heat are estimated as a function of the penetration percentage of ‘energy efficient’ loads over the conventional DH network. Key outcomes show the trade-offs between the potential savings in operating costs and the reduction in heat demand: relative losses in this scenario are maintained at 13.1% compared to 15.3% expected with conventional DH; and relative pumping power demand decreased as well. In other words, the costs of supplying heat decrease, even though the total heat supplied is reduced.

  • 133.
    Castro Flores, José Fiacro
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. École des Mines de Nantes - EMN, Energy Systems and Environment - DSEE.
    Lacarrière, Bruno
    École des Mines de Nantes - EMN, Energy Systems and Environment - DSEE.
    Le Corre, Olivier
    École des Mines de Nantes - EMN, Energy Systems and Environment - DSEE.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Study of a district heating substation using the return water of the main system to service a low-temperature secondary network2014In: Proceedings of The 14th International Symposium on District Heating and Cooling: Low temperature district heating and key developments for future energy systems / [ed] Anna LAND, Stockholm, SE: Swedish District Heating Association , 2014Conference paper (Refereed)
    Abstract [en]

    The development of district heating (DH) systems is facing the challenge of servicing areas with lower energy demands whose connection might not be either effective or profitable if the conventional DH technology is used. The purpose of this paper is to propose a complementary approach on how to effectively service low-energy building (LEB) areas using the existing DH networks. The proposed solution consists in supplying a secondary low-temperature (LT) network by means of a ‘low temperature’ substation that uses the return water from the main DH network as a substitute for the primary energy source, together with a minor portion of the main DH supply. Two types of LT substations are proposed and compared to a reference substation: First, a one-stage heat exchanger that uses a mixture of the main DH network return and supply flows as thermal energy source. Second, a two-stage heat exchanger that is fed by both the main DH return and supply flows. The system subject to this study consists on the LT substation with supply/return temperatures at 55/25 °C average. The system energetic performance is analysed though thermodynamic simulation. Outdoor ambient temperatures variations throughout the year are considered for two specific locations, assuming full and partial load operation. The results show that it is possible to supply 20-50% of the total annual heat demand of a LTDH network using the return flow from the main DH network. The solution presented in this paper is seen as being of potential interest to deliver thermal energy services to LEB areas.

  • 134.
    Castro Flores, José Fiacro
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. École des Mines de Nantes - EMN, Energy Systems and Environment - DSEE.
    Rossi Espagnet, Alberto
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Chiu, NingWei Justin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lacarrière, Bruno
    IMT Atlantique - Energy Systems and Environment - DSEE.
    Techno-Economic Assessment of Active Latent Heat Thermal Energy Storage Systems with Low-Temperature District Heating2017In: International Journal of Sustainable Energy Planning and Management, ISSN 2246-2929, E-ISSN 2246-2929, p. 5-17Article in journal (Refereed)
    Abstract [en]

    Thermal energy storage (TES) is a set of technologies with the potential to enhance the efficiency and flexibility of the 4th generation of district heating systems. This study presents a comparative techno-economic assessment of active TES systems suited to operate with low-temperature district heating (LTDH) for short-term heat storage applications. Latent heat systems (LH-TES) are compared qualitatively and quantitatively to water-based sensible heat systems (SH-TES). It is concluded that latent heat TES systems are still more expensive than water-based systems regarding energy storage cost (EUR/kWh) ranging from 1.5 to 4 times more, mainly due to the cost of the storage media. However, considering distributed TES systems integrated to LTDH, small-scale active LH-TES systems will become more cost-competitive as storage media costs are expected to decline in the future. This study represents a step forward in the development and improvement of the DH system through the integration of TES which will play a key role in the future smart energy system.

  • 135.
    CATY, Fabien
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    DESIGN OF SECONDARY AIR SYSTEM AND THERMAL MODELS FOR TRIPLE SPOOL JET ENGINES2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis deals with the understanding of the secondary air system of athree spool turbofan. The main purpose is the creation of secondary air systemand thermal models to evaluate the behavior of this kind of engine architectureand estimate the pros and cons in comparison with a typical two spool turbofan. Afinite element model of the secondary air system of the engine has been designedbased on the experience of typical jet engines manufactured by Snecma. Theinner thermodynamic pattern and mass flow rates of the engine were obtained.Some local improvements were then made by making analogies with the enginesmanufactured by Snecma. After having communicated the results to theperformance unit to get updates thermodynamic cycles, a quite reliable model wasobtained and

  • 136.
    Cerra, Noemi
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    An Energy Management Oriented Analysis: Case Study of a Waste to Energy Plant in Lecco, Italy2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The ISO 50001 standard on energy management systems was released in 2011 with the aim of providing organizations with a standardised guideline for the evaluation and continual improvement of energy performance. Complex structures such as the waste to energy (WTE) sector, which must comply with social, environmental, economic and productivity objectives, can benefit from the development of a compliant energy management system (EnMS). Energy efficiency and energy savings contribute to the mitigation of the heavy cost of such a facility, while the benchmark analysis allows verifying the state of the system and the potential areas for improvement. The energy performance improvements can be valorised on an environmental base, and proper promotion of the process can contribute to the mitigation of social opposition.

    This thesis reviews the energy performance of a waste to energy facility located in Lecco, Italy, using the information available from the control system already installed in the company. Regression analysis is used to fit linear and polynomial functional forms to the energy consumption data and create the energy baseline for the areas of significant energy use and production with a predictive power of 59 – 92%. The difference among the baseline and the actual energy consumption is proposed as energy performance indicator, in order to appreciate the results of the improvement opportunities, and a set of key performance indicators are evaluated for internal and external benchmarking of the facility.

    The economic feasibility of a selection of sectorial Best Available Technologies (BATs) and the related energy performance improvement is evaluated, revealing that 2 – 16 M€ can be invested in the system retrofit; the creation of synergies with the facility heating, cooling and electricity demand is also suggested. Lastly, an energy, economic and environmental analysis is suggested as a ranking system for the identified improvement opportunities.

    The methodology and results of this study are intended to provide a proper energy review for Silea Spa, suggest a review procedure for other WTE facilities willing to develop a compliant EnMS and enrich the literature with a case study on WTE.

    For the Italian context, which is currently facing difficulties in the modernization of the waste management system (WMS), the ISO 50001 application on WTE facilities offers a unified structure that can be used by the government to map the current status of each facility and develop the legislative framework in accordance to the needs of the WMS, the circular economy and the public opinion.

  • 137.
    Cerutti, Stefano
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Validation and Verification of Flutter CFD Tools for Steam Turbines with Cascade Measurements2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This work has been commissioned by Alstom Power with the scope of assessing the validity of a new flutter calculation method to be integrated in the current stream turbines blade design process.

    Flutter is universally defined as an aeroelastic unstable phenomenon which occurs when energy is transferred to a structure from the flow surrounding it. If the structure’s mechanical damping is not sufficient to dissipate the added energy, vibration in the blade can escalate until material failure is reached. It is the task of engineers to ensure that a blade design will not encounter a flutter condition during its normal operation. Numerical methods offer today the most cost- and time-effective approach to the problem.

    In the present study three different tools are considered: ANSYS CFX 12.1 (periodic boundary conditions), ANSYS CFX 14.0 (phase-shifted boundary conditions) and AU3D (phase-shifted boundary conditions). Two test cascade profiles, the FUTURE-EPFL and the Standard Configuration 11, are analysed. The first features subsonic, attached flow and the latter a transonic separated flow. The influence of simulation parameters and numerical discretisation on steady and unsteady results is assessed. For each case, the numerical solution is compared to experimental measurement data covering a comprehensive range of inter-blade phase angles.

    It is concluded that the periodic boundary conditions method generally offers a more consistent approach, at the cost of a greater computational time. Phase-shift methods, on the other hand, showed a potential for calculating aerodynamic damping in a time- effective way; although a greater time step dependency was revealed.

    A new method for computing aerodynamic damping in CFX is described in this document. The method consists in performing the Fourier transform on pressure coefficients in the solver, so that the periodicity of the solution can directly be monitored during the run. 

  • 138.
    Chandramouli, Sathyanarayanan
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Gojon, Romain
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Fridh, Jens
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Mihaescu, Mihai
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Numerical characterization of entropy noise with a density based solver2017In: 12th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics, ETC 2017, KTH Royal Institute of Technology, 2017Conference paper (Refereed)
    Abstract [en]

    In this work, dbnsTurbFoam, a new coupled density based solver, written in the framework of FOAM-EXTEND, is considered. The solver is first assessed on two canonical compressible flow scenarios, namely the Sod's shock tube and the ONERA S8 transonic channel. Results are compared with analytical formulations and experiments, respectively. 2-D Unsteady Reynolds Averaged Navier-Stokes simulations and 3-D Large Eddy Simulations of the flow within the passages of a geometrically simplified High Pressure Turbine Nozzle Guide Vane are then performed. Results are compared against experimental data in order to justify the geometrical simplifications made. Finally, the case of a sinusoidal temperature forcing at the inlet is considered in order to study the phenomenon of indirect combustion noise. Notably, the impact of the forcing on the vortex shedding dynamics and on the losses is discussed.

  • 139.
    Chen, Mingming
    et al.
    Tianjin Univ, Sch Chem Engn & Technol, China.
    Zhang, Hongjuan
    Fan, Liangdong
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Wang, Chengyang
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. Hubei Univ, Fac Phys & Elect Sci, Hubei Collaborat Innovat Ctr Adv Organ Chem Mat, China.
    Ceria-carbonate composite for low temperature solid oxide fuel cell: Sintering aid and composite effect2014In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 39, no 23, p. 12309-12316Article in journal (Refereed)
    Abstract [en]

    In this study, the effect of carbonate content on microstructure, relative density, ionic conductivity and fuel cell performance of Ce0.8Sm0.2O1.9-(Li/Na)(2)CO3 (SDC-carbonate, abbr. SCC) composites is systematically investigated. With the addition of carbonate, the nanoparticles of ceria are well preserved after heat-treatment. The relative densities of SCC pellets increase as the carbonate content increases or sintering temperature rises. Especially, the relative density of SCC2 sintered at 900 degrees C is higher than that of pure SDC sintered at 1350 degrees C. Both the AC conductivity and DC oxygen ionic conductivity are visibly improved compared with the single phase SDC electrolyte. Among the composites, SDC-20 wt% (Li/Na)(2)CO3 (SCC20) presents high dispersion, relative small particle size, and the dense microstructure. The optimized microstructure brings the best ionic conductivity and fuel cell performance. It is hoped that the results can contribute the understanding of the role of carbonate in the composite materials and highlight their prospective application.

  • 140.
    Cherif, Mohamed
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Noralm, Zeerak
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Design and development of a simple data acquisition system for monitoring and recording data2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 141.
    Ching, Diego
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Upgrading of biomass: alternative ways for biomass treatment2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As the world population and wealth increases it is necessary to look for sustainable alternatives to guarantee modern living standards. With depleting resources and the threat of global warming, biomass is emerging as a promising alternative to lay the basis for a bio-based sustainable economy. New biomass upgrading trends lead to the concept of biorefinery, where a large array of chemicals, fuels and energy can be produced, maximizing the value of biomass. The aim of the present work is to find industrial biorefinery processes developed to produce chemicals and fuels but that at the same time yield considerable amounts of combustible by-products that can be employed as a fuel in Vattenfall´s power plants. This paper is focused on lignocellulosic biomass as a feedstock.

    A comprehensive review of existing technologies at different maturity levels to upgrade biomass is done. The review covers biomass pretreatment operations, thermochemical, chemical and biochemical processes. It starts by describing simple unitary operations that are used to build complex biorefinery systems. A selection of some of the possible biorefinery schemes is briefly described. After listing and describing different biomass upgrading processes, three process were selected for further analysis. Two biorefinery processes with different maturity levels were selected: the Biofine process and Lignocellulosic Ethanol. A process to produce a solid fuel, Hydrothermal Carbonization, was selected as well. The process selection was done according to Vattenfall´s interests.

    The three processes selected were further analyzed performing a mass and energy balance. To achieve these tasks, a model of the processes using Microsoft Excel was done. The estimation of the product yields and energy usage was done assuming woodchips as a feedstock. Sensitive operating conditions where the energy usage can be improved are identified. After the mass and energy balance an economical evaluation by means of OPEX and CAPEX calculations was done to determine the profitability of the processes. Opportunities for each process are identified and conditions to achieve or improve the profitability of the processes were pinpointed.

    The biorefinery concept is an emerging technology and as any new technology there are obstacles that need to be surpassed for being introduced into the market. A discussion on these issues was made as they will drive R&D efforts, industrial development and policies in the upcoming years. The importance of innovation in technology through R&D and market push policy measures was analyzed as it plays a fundamental role in the industrial dynamics of emerging technologies. Synergies and cooperation between the pulp and paper, forest, petrochemical and energy industries should be seek to tackle the challenges these technologies present and endorse a sustainable bio-based economy.

  • 142.
    Chiodetti, Matthieu
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Bifacial PV plants: performance model development and optimization of their configuration2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Bifacial solar modules can absorb and convert solar irradiance to current on both their front side and back side. Several elements affects the bifacial yield, especially the ground albedo around the system or the installation configuration. In this document, investigations carried out at EDF R&D facilities regarding the use of bifacial modules in large scale PV farm are presented. Tests on the outdoor facilities were conducted to validate and improve a bifacial stand model developed under a Dymola/Modelica environement. Furthermore, a global optimization method was implemented to determine the optimal configuration of a large bifacial plant with modules facing south. Investigations showed the importance of a new albedo model to accurately evaluate the irradiance received on the rear side. The new model shows a relative error on the rear irradiance under 5% when compared with experimental data. Techno-economical optimization of a bifacial plant was conducted at different locations and for different ground albedo. The results shows that the gain on the specific production can vary between 7.2 and 14.2% for a bifacial plant when compared with a monofacial plant. Bifacial plants are expected to become more profitable than monofacial plants in some of the cases tested when their module cost will reach 68 c€/Wp.

  • 143.
    Chitas, Dimosthenis
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Modeling and Simulation of a Small-Scale Polygeneration Energy System2015Independent thesis Advanced level (degree of Master (Two Years)), 60 credits / 90 HE creditsStudent thesis
    Abstract [en]

    The polygeneration is an innovative and sustainable solution which has become an attractive concept. The simultaneous production of electricity, heating and cooling including hot and cold water respectively in autonomous smaller energy systems can manage a more flexible and environmentally friendly system. Furthermore distributed generation and micro scale polygeneration systems can perform the increase of the utilized renewable energy sources in the power generation. The aforementioned energy systems can consist of several power generation units however the low emission levels, the low investment costs and the fuel flexibility of microturbines are some of the reasons that the study of the microturbines in polygeneration systems is a crucial necessity.

    In this study, an autonomous small-scale polygeneration energy system is investigated and each component is analyzed. The components of the system are a microturbine, a heat recovery boiler, a heat storage system and an absorption chiller. The purpose of this work is the development of a dynamic model in Matlab/Simulink and the simulation of this system, aiming to define the reliability of the model and understand better the behavior of such a system. Special focus is given to the model of the microturbine due to the complexity and the control methods of this system. The dynamic model is mainly based on thermodynamic equations and the control systems of the microturbine on previous research works. The system has as a first priority the electricity supply while thermal load is supplied depending on the electric demand. The thermal load is supplied by hot water due to the heat recovery which takes place at the heat recovery boiler from the flue gases of the microturbine. Additionally the design of the system is investigated and an operational strategy is defined in order to ensure the efficient operation of the system. For this reason, after creating the load curves for a specific load, two different cases are simulated and a discussion is done about the simulation results and the future work.

  • 144.
    Chitrakar, Sailesh
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. Kathmandu University.
    FSI analysis of Francis turbines exposed to sediment erosion2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Sediment erosion is one of the key challenges in hydraulic turbines from a design and maintenanceperspective in Himalayas and Andes. Past research works have shown that the optimization of theFrancis turbine runner blade shapes can decrease erosion by a signicant amount. This study conductedas a Master's Thesis has taken the proposed designs from past works and conducted a CFDanalysis on a single passage of a Francis runner blade to choose an optimized design in terms of erosionand eciency. Structural analyses have been performed on the selected design through one-way andtwo-way FSI to compare the structural integrity of the designs.Two types of cases have been considered in this thesis work to dene the boundary condition of thestructural model. In the rst case, a runner blade is considered to have no in uence of the joint andother stier components. In the second case, a sector of the whole runner has been modeled withnecessary boundary conditions. Both one-way and two-way FSI have been performed on the casesfor the designs. Mesh independent studies have been performed for the designs, but only for the rstcase, whereas in the second case, a ne mesh has been used to make the analysis appropriate.The loads have been imported into the structural domain from the uid on the interfaces for one-wayFSI. In the case of two-way FSI, the Multi-Field Solver (MFX) supported by ANSYS has been usedto solve the coupled eld analysis. A fully coupled FSI in ANSYS works by writing an input le inthe structural solver containing the information about the interfaces in the structural domain, whichis imported in the uid solver. The interaction between the two domains is dened in ANSYS-CFX,including the mesh deformation and solver setups. The results have been post-processed in CFX-Post,where the results from both the elds are included. It has been found that the structural integrity ofthe optimized design is better than the reference design in terms of the maximum stress induced inthe runner. The two-way FSI analysis has been found as an inevitable part of the numerical analysis.However, with the advancement of the computational capability in the future, there could be a greatscope in the research eld to carry out a fully-coupled transient simulation for the whole runner toget a more accurate solution.

  • 145.
    Chiu, Justin N. W.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Castro Flores, José Fiacro
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lacarrière, B.
    Industrial surplus heat transportation for use in district heating2016In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 110, p. 139-147Article in journal (Refereed)
    Abstract [en]

    M-TES (Mobile Thermal Energy Storage) technology is explored in this paper for transportation of industrial surplus heat for use in LTDH (low temperature district heating network). LTDH has promising potential in utilizing low grade heat, on the other hand, 20%–50% of industry generated surplus heat is often released to the ambient environment. M-TES is used to match thermal energy supply and demand that occur at different locations and that are shifted in time. In this paper, design of M-TES is conducted, optimization in operating strategies is performed, sensitivity analysis on levelized cost is studied, and environmental impact of CO2 emissions due to transportation is evaluated. The results of the study show an array of transportation means and storage operating strategies under which M-TES is technically, economically and environmentally sound for transportation of industrial surplus heat for use in LTDH network. © 2016 Elsevier Ltd

  • 146.
    Chiu, Justin N. W.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Industrial surplus heat storage in smart cities2015In: ASME 2015 9th International Conference on Energy Sustainability, ES 2015, collocated with the ASME 2015 Power Conference, the ASME 2015 13th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2015 Nuclear Forum, American Society of Mechanical Engineers , 2015Conference paper (Refereed)
    Abstract [en]

    Surplus heat generated from industrial sectors amounts to between 20% and 50% of the total industrial energy input. Smart reuse of surplus heat resulted from industrial sectors and power generation companies is an opportunity to improve the overall energy efficiency through more efficient use the primary energy sources. A potential solution to tackle this issue is through use of thermal energy storage (TES) to match user demand to that of the generated surplus heat. A mobile TES (MTES) concept of transportation of industrial surplus heat from production sites to end customers has shown promising results. One commissioned demonstration project using industrial heat for swimming pool water temperature regulation in Dortmund, Germany proved the interest and attention given to this concept. In this paper, a techno-economic case study in Sweden of transportation of surplus thermal energy to district heating in smart cities is presented. The application consists of heat storage at 110°C- 130°C through the use of phase change materials (PCM) based TES, notably with use of Erythritol (90 kWh/ton) for the considered temperature range, to remote district heating network located at 48 km from the thermal energy generation site. The advantages of using latent heat based PCM are the high enthalpy density per unit volume and per unit mass, as well as the quasi-constant temperature during charging and releasing of heat. The M-TES in this study has a total storage capacity of 2.1 MWh, the optimization of charge/discharge time to the amount of stored/released energy and to that of energy transportation rate is presented in this paper. Contrary to logical thinking, it is shown through this work that under certain conditions, it is more cost-effective to operate at partial load of storage units albeit the increased number of transport trips and charge/discharge cycles.

  • 147.
    Chiu, Justin NingWei
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Heat Transfer Aspects of Using Phase Change Material in Thermal Energy Storage Applications2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Innovative methods for providing sustainable heating and cooling through thermal energy storage (TES) have gained increasing attention as heating and cooling demands in the built environment continue to climb. As energy prices continue to soar and systems reach their maximal capacity, there is an urgent need for alternatives to alleviate peak energy use. TES systems allow decoupling of energy production from energy utilization, both in location and in time. It is shown in this thesis that successful implementation of TES in the built environment alleviates peak energy load and reduces network expansion as well as the marginal energy production cost.

    This thesis analyzes phase change material (PCM) based TES systems in terms of material property characterization, numerical modeling and validation of thermal storage, as well as case specific techno-economic feasibility studies of system integration. The difficulties identified in latent heat TES design, such as heat transfer aspects, subcooling and identification of phase separation, have been analyzed through Temperature-History mapping and TES numerical modeling with experimental validation. This work focuses on the interdependency between resource availability, thermal charge/discharge power and storage capacity. In a situation where resource availability is limited, e.g. when using free cooling, waste heat or off-peak storage, the thermal power and storage capacity are strongly interrelated and should always be considered in unison to reach an acceptable techno-economic solution. Furthermore, when considering TES integration into an existing thermal energy distribution network, three adverse aspects are revealed in the Swedish case study: the single tariff system, the low-return temperature penalty, and the low storage utilization rate. These issues can be overcome through better adapted policies and optimized storage control strategies. Finally, despite the currently unfavorable conditions in the Swedish energy system, it is shown that TES has the potential to mitigate climate change through greenhouse gas emission reduction by displacing fossil-fuel based marginal thermal energy production.

  • 148.
    Chiu, Justin NingWei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Gravoille, Pauline
    Ecole Nationale Supérieure de l'Energie, l'Eau et l'Environnement.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Active Free Cooling Optimization with Thermal Energy Storage in Stockholm2012In: InnoStock The 12th International Conference on Energy Storage: Book of Abstract / [ed] Stock Conference, 2012, p. 106-107Conference paper (Refereed)
    Abstract [en]

    In the goal of reaching an environmental benign society, energy saving through green building design has gained increasing attention. Passive buildings may cut down the energy requirement in winter through use of solar based heating, increased insulation and smart design of energy management. However it has also been shown that over insulated structures also create excessive heat gain in summer generating thus an increased cooling demand [1,2].

    In countries where the ambient environment is at sufficiently low temperature at night to act as a heat sink, thermal energy displacement from period when cold is available to period when cooling is needed may alleviate fossil fuel based cooling produced with conventional means. The displacement of thermal energy may be reliably achieved with use of Thermal Energy Storage (TES), such systems in buildings have been shown to provide better indoor thermal comfort by a number of researchers [3,4,5]. Direct advantages of using TESs are reduction in size of cooling equipment, decrease in electricity consumption, and better utilization of renewable sources.

    Phase change materials (PCMs) that rely on use of latent heat for storage of thermal energy prove to lead to more compact design of energy system and a steadier source temperature [6]. An environmentally friendly active free cooling solution with use of Latent Heat Thermal Energy Storage (LHTES) is proposed in this work where an optimization between cost, comfort level and storage design is studied and compared against conventional chillers in Stockholm climate.

  • 149.
    Chiu, Justin NingWei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Gravoille, Pauline
    National Institute of Energy, Hydraulic and Environmental Engineering, Grenoble, France.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Active free cooling optimization with thermal energy storage in Stockholm2013In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 109, no SI, p. 523-529Article in journal (Refereed)
    Abstract [en]

    Latent heat thermal energy storage (LHTES) integrated active free cooling stores night time cold and serves as heat sink for cooling when demand rises. Passive buildings, albeit their advantages in limiting heat loss during winter time, are often paired with excessive internal overheating in summer, as shown in the first part of this study. Under the climate condition in Stockholm, LHTES systems may provide solutions for sustainable cooling with use of renewable cooling sources. This study presents a multi-objective optimization on system cost and cooling supply for various LHTES configurations followed with a sensitivity analysis on phase change material cost and energy price. Results indicate that optimized LHTES may meet cooling needs while retaining economic viability. However, LHTES based cooling systems may require substantially higher electricity demand than conventional air conditioning unit for applications where high cooling thermal power rate is to be met, a tradeoff to indoor comfort level needs to be considered to reach the concept of sustainable free cooling. We here provide a novel techno-economic feasibility study of active free cooling LHTES in Stockholm as well as new insights to cost, comfort level and energy requirement with use of multi-objective optimization algorithm.

  • 150.
    Chiu, Justin NingWei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Furberg, Richard
    Advanced Thermosyphon Cooling with Nanoporous Structured Mini Channel Evaporators2010In: PROCEEDINGS OF THE ASME MICRO/NANOSCALE HEAT AND MASS TRANSFER INTERNATIONAL CONFERENCE, VOL 3, NEW YORK: AMER SOC MECHANICAL ENGINEERS , 2010, p. 183-189Conference paper (Refereed)
    Abstract [en]

    Attention has been given to enhance boiling surfaces in order to decrease the temperature difference and to increase heat transfer coefficient. Structured surfaces may provide both surface enlargement and artificial nucleation sites, thus ameliorate the heat transfer coefficient. The goal of the present experimental work is to analyze the influence on heat transfer coefficient (HTC) of enhanced surface structures coated on mini channel heat exchanger working in a closed loop thermosyphon system. Experimental tests were carried out with three types of surface enhanced mini channel evaporators: smooth surface, threaded structure and nanoporous coating. The evaporators are single channel half circularly shaped, adapted for filming purpose, measuring 30mm in length and 3mm in diameter. Surface areas of channels are 1.41cm(2). Experiments were conducted in refrigerant 134a at 4.87bar (reduced pressure pr=0.12) and at heat fluxes ranging from 0.7W/cm(2) to 63.8W/cm(2). A high speed video camera was used for visualization of the two-phase flow in the evaporator channel. It is shown that threaded surface provides the highest heat transfer coefficient (HTC) from no load to heat flux of 7.1W/cm(2), the nanoporous structure shows the highest performance between 7.1W/cm(2) and 49.6W/cm(2), and the smooth surface channel exhibits the best HTC from 49.6W/cm(2) and higher. In this paper, the influences of heat flux and surface structures on HTC are discussed, and the impact of refrigerant flow regimes on heat transfer performance is also highlighted.

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