In this thesis I deal with the issue of stand-alone solar system development. This system ensures the supply of all the energy needed for a reference house. It consists of a solar concentrator and a heat reservoir. I used mathematical models to solve this issue. The calculations showed, that the concentration of solar radiation into the heat reservoir can usually achieve 69 % efficiency. The efficiency can be even higher when using a very reflective materials of the solar concentrator. In this thesis, the thermal reservoir is described and its improvements are suggested based on the optimization calculations. Thanks to knowledge gained during solving this issue, a prototype of the stand-alone solar system is going to be built. All findings will be experimentally verified with this prototype.

Resumo: Este texto descreve as linhas de pesquisa em que o autor atuou após o seu doutorado relacionadas a área de energia, abrangendo os seguintes tópicos: análise exergética e análise exergoeconômica. As produções científicas aqui descritas foram resultados obtidos a partir das pesquisas do autor e de orientações de alunos de pós-graduação, além de resultados de colaborações com outros pesquisadores do grupo de pesquisa que participa. Dentre as principais contribuições dos artigos publicados, estão o desenvolvimento e aplicação de metodologia de análise exergoeconômica para diversas configurações de sistemas de geração de energia térmica e elétrica, e também a participação na construção de um protótipo reformador a vapor de biogás e de um gaseificador de leito fluidizado no Laboratório de Otimização de Sistemas Energéticos da UNESP, campus de Guaratinguetá. O autor está classificado na base Scopus com um índice h igual a 9, e no Google Acadêmico com um índice h igual a 11, demonstrando a relevância de suas 19 publicações em revistas indexadas de elevado fator de impacto / Abstract: This text describes the lines of research in which the author acted after his doctorate related to the energy area covering the following topics: exergetic analysis and exergoeconomic analysis. The scientific productions described herein were results obtained from the author's research and guidance from graduate students, besides the results of collaborations with other researchers from the research group that participates. Among the main contributions of the articles published, are the development and application of exergoeconomic analysis for various configurations of thermal and electrical generation systems, and also the participation in the construction of a biogas steam reformer prototype and a fluidized bed gasifier in the Energy Systems Optimization Laboratory of UNESP, Guaratinguetá campus. The author is classified in the Scopus base with an h index of 9, and in Google scholar with an h index equal to 11, demonstrating the relevance of its 19 publications in indexed journals with high impact factor

In order to increase the efficiency of an adsorption heat pump system, a stratified thermal heat storage can be used to enable regeneration of heat between the different phases of the process. It’s crucial to avoid mixing and to keep layers intact inside the storage tank. As mixing generally occurs during charging and discharging, the aim of this project is minimizing these effects by introducing porous media into the region of the inlet ports. The impact of porous media on laminar and turbulent flow inside stratified thermal storage tanks is qualitatively and quantitatively investigated. Two thermal storage tanks are examined in which polyurethane foam is used as porous medium. Numerical results are compared with experimental results in order to study the effects of the porous medium and validating numerical models. For the quantitative investigation, equations describing flow in porous media are obtained and implemented into computational fluid dynamics (CFD) models. Simulations of storage tanks are performed by means of 2D-axisymmetric domain models. Tanks are investigated qualitatively using two methods; background oriented schlieren (BOS) and ink colored inlet water, in order to visualize flow and mixing inside tanks. Thermo elements are also used to measure temperatures at given locations. Results from experimental- and numerical cases show how porous media influence stratification in a positive way. Flow visualizing experiments (using ink and BOS) showed decrease in thermocline thickness when using polyurethane foam. This could also be seen for the numerical cases. Experimental- and numerical investigations of the ability of porous media to damp turbulence intensity and kinetic energy, showed a positive effect. Further improvements have to be done, adjusting numerical models to experimental results. Comparison between the numerical- and experimental results showed differences both in flow fields and temperature distributions. Results indicate however, that porous media could play an increasing role in the development of stratified heat storages. / Stratifierade värmelagringstankar kan användas för att öka effektiviteten hos adsorptionsvärmepumpsprocesser genom att möjliggöra regeneration av värme mellan faserna. För att dessa effektivt ska kunna användas är det viktigt att temperaturskikt hålls intakta inuti lagringstankarna och att omröring undviks. Då omröring oftast uppstår vid laddning och tömning av lagringstankarna är målet för det här projektet att minska denna effekt genom att använda porösa medier vid deras inlopp. Porösa mediers inverkan på flöden och temperaturskikt inuti värmelagringstankar undersöks både kvalitativt och kvantitativt i det här projektet. Två tankar undersöks där polyuretanskum används som poröst medium. Numeriska resultat jämförs med experimentella för att undersöka effekterna av de porösa medierna, samt för att validera de numeriska modeller som används. Ekvationer som beskriver flödet genom porösa medier implementeras i CFD (computational fluid dynamics) modeller och lagringstankarna modelleras som 2D-axelsymmetriska domäner. Bakgrundsorienterad schlierenteknik (BOS) och färgning av inloppsvatten används för den kvalitativa undersökningen och termoelement används för att mäta temperaturer vid olika positioner. Numeriska och experimentella resultat visar hur porösa medier har en positiv inverkan på temperaturskiktningen. Resultat från experiment då BOS teknik och färgning av vatten används visar en minskning av det termoklina skiktets tjocklek med en ökad polyuretanskumtjocklek. Detta kunde också ses för de numeriska fallen. Numeriska och experimentella resultat visar även att porösa medier har en positiv inverkan på dämpningen av turbulens och kinetisk energi. Fortsatt arbete krävs för att anpassa numeriska modeller till experimentella data. Jämförelser mellan numeriska och experimentella resultat uppvisar skillnader både hos flödesfält samt hos temperaturfördelningar inuti tankarna. Resultaten visar dock att porösa medier skulle kunna spela en betydande roll för utvecklingen av stratifierade värmelagringstankar.

Idag står världen inför en rad olika miljörelaterade problem. Ett av dessa och det kanske mest omtalade är hur utsläpp av växthusgaser sakta men säkert höjer planetens medeltemperatur. Hållbar utveckling är ett begrepp som driver diskussionen framåt om vad vi behöver göra och hur vi behöver förändras för att lösa problemen. Växthusgaserna och deras hot mot klimatet är starkt relaterat till energi. Förnyelsebara energikällor skulle kunna vara en dellösning på problemet men de kräver energilagring av olika former för att kunna ersätta sina fossila konkurrenter. Termisk energilagring är ett sätt att lagra energi på och kan delas upp i tre olika grupper. Dessa är sensibel, latent och termokemisk värmelagring. Syftet med denna litteraturstudie var att kartlägga olika applikationer av latent värmelagring som kan bidra till ett mer hållbart samhälle i framtiden. Resultatet visar att det finns många olika typer av så kallade fasomvandlingsmaterial (PCMs). Beroende på vid vilka temperaturer värme ska lagras vid används olika PCMs. PCMs kan användas för latent värmelagring inom många olika områden. Byggnader är ett av dessa områden där PCMs kan användas för att kyla och värma utrymmen antingen genom integration i ventilationssystem eller i själva byggnadsmaterialen. Latent värmelagring kan också användas i termiska solkraftverk. Latent värmelagring har på senare tid fått stor uppmärksamhet tack vare PCMs förmåga att lagra värme i små volymer och under konstant temperatur. Dock möter tekniken problem vid värmeöverföringen vilket t.ex. är fallet i lagring av termisk solenergi. Forskning pågår därför för att generellt höja PCMs termiska egenskaper. Ett exempel på detta är Nano-PCM. Resultatet visar även att latent värmelagring idag används av företag som affärsidé för olika tillämpningar. Från resultatet går det att dra slutsatsen att latent värmelagring används idag men att det krävs ytterligare forskning för att tekniken ska kunna konkurrera med andra värmelagringsmetoder. / Today, the world faces a number of environmental-related problems. One of these and perhaps most discussed is how emissions of greenhouse gases slowly but surely raise the planet’s average temperature. Sustainable development is a concept that drives the discussion forward and tells us what we need to do and how we need to change to solve the problems. Greenhouse gases and their threats to the climate are strongly related to energy. Renewable sources of energy could be a partial solution to the problem, but they require energy storage of different forms to replace their fossil competitors. Thermal energy storage is a way of storing energy and can be divided into three different groups. These are sensible, latent and thermochemical heat storage. The purpose of this literature study was to map different applications of latent heat storage that can contribute to a more sustainable society in the future. The result shows that there are many different types of phase changing materials (PCMs). Depending on the temperature at which heat is to be stored, different PCMs are used. PCMs can be used for latent heat storage in many different areas. Buildings are one of these areas where PCMs can be used to cool and heat spaces either through integration into ventilation systems or in the building materials itself. Latent heat storage can also be used in thermal solar power plants. Latent heat storage has recently received great attention thanks to PCMs ability to store heat in small volumes and under constant temperature. However, the technology is experiencing problems in the heat transfer, such is the case in the storage of thermal solar energy. Research is therefore ongoing to generally increase PCMs thermal properties. An example of this is Nano-PCM. The result also shows that latent heat storage today is used by companies as a business concept for various applications. From the result, it can be concluded that latent heat storage is used today, but that further research is required for the technology to compete with other heat storage methods.

No description available.

Irreversible electroporation has recently emerged as an effective focal ablation technique. When performed clinically, the procedure involves placing electrodes into, or around, a target tissue and applying a series of short, but intense, pulsed electric fields. Oftentimes, patient specific treatment plans are employed to guide procedures by merging medical imaging with algorithms for determining the electric field distribution in the tissue. The electric field dictates treatment outcomes by increasing a cell's transmembrane potential to levels where it becomes energetically favorable for the membrane to shift to a state of enhanced permeability. If the membrane remains permeabilized long enough to disrupt homeostasis, cells eventually die. By utilizing this phenomenon, irreversible electroporation has had success in killing cancer cells and treating localized tumors. Additionally, if the pulse parameters are chosen to limit Joule heating, irreversible electroporation can be performed safely on surgically inoperable tumors located next to major blood vessels and nerves. As with all technologies, there is room for improvement. One drawback associated with therapeutic irreversible electroporation is that patients must be temporarily paralyzed and maintained under general anesthesia to prevent intense muscle contractions occurring in response to pulsing. The muscle contractions may be painful and can dislodge the electrodes. To overcome this limitation, we have developed a system capable of achieving non-thermal irreversible electroporation without causing muscle contractions. This progress is the main focus of this dissertation. We describe the theoretical basis for how this new system utilizes alterations in pulse polarity and duration to induce electroporation with little associated excitation of muscle and nerves. Additionally, the system is shown to have the theoretical potential to improve lesion predictability, especially in regions containing multiple tissue types. We perform experiments on three-dimensional in vitro tumor constructs and in vivo on healthy rat brain tissue and implanted tumors in mice. The tumor constructs offer a new way to rapidly characterize the cellular response and optimize pulse parameters, and the tests conducted on live tissue confirm the ability of this new ablation system to be used without general anesthesia and a neuromuscular blockade. Situations can arise in which it is challenging to design an electroporation protocol that simultaneously covers the targeted tissue with a sufficient electric field and avoids unwanted thermal effects. For instance, thermal damage can occur unintentionally if the applied voltage or number of pulses are raised to ablate a large volume in a single treatment. Additionally, the new system for inducing ablation without muscle contractions actually requires an elevated electric field. To ensure that these procedures can continue to be performed safely next to major blood vessels and nerves, we have developed new electrode devices that absorb heat out of the tissue during treatment. These devices incorporate phase change materials that, in the past, have been reserved for industrial applications. We describe an experimentally validated numerical model of tissue electroporation with phase change electrodes that illustrates their ability to reduce the probability for thermal damage. Additionally, a parametric study is conducted on various electrode properties to narrow in on the ideal design. / Ph. D.

The construction industry strives for climate neutrality by 2045-2050 with a focus oncollaboration, innovation, and efficient use of resources to reduce greenhouse gasemissions and promote sustainable construction methods. This degree project from theBuilding Engineering program at Halmstad University investigates energy efficiency andoptimization of the asphalt manufacturing process, especially heat storage in silos, incollaboration with Skanska Industrial Solutions.The study applies qualitative methods, including interviews with experts and visits to anasphalt plant in Sperlingsholm, Halmstad. The theoretical framework includes sustainabledevelopment, sustainable road networks, hot mix asphalt (HMA), and design andmaterials for heat storage silos.The research methodology included data collection, interviews, field visits andsimulations with COMSOL Multiphysics to analyse temperature changes and comparedifferent silo design options. Autodesk AutoCAD was used to create 2D drawings.The results emphasize energy efficiency and sustainability in asphalt manufacturing, withthe potential to reduce greenhouse gas emissions through optimized silo design andinsulation. Specifically, the implementation of heat storage silos shows a significantreduction in oil consumption and 𝐶𝑂2 emissions. The study further recommends researchfor validation and improvement in real production environments and contributes withinsights into sustainable construction methods, underscoring the need for technologicalinnovation to meet the environmental challenges in the construction industry.

Thesis (MEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: Solar energy is a time dependent, high-temperature radiant energy resource. The utility of a solar thermal energy system increases if the hot temperature source is available when it is needed most. This is realized by the thermal storage of the solar energy. Thermal storage gives greater versatility to a solar energy system by decoupling the heat source from the heat sink. A large quantity of energy may be stored during the melting process in a phase change material (PCM) within a small temperature range. This molten PCM can then deliver its absorbed heat at a constant temperature in a heating application. In this study a phase change storage system (PCS) is developed and proposed for a solar water heating application. This PCS system stores more heat per unit mass than would be possible with water across the same temperature range. The heat transfer rate in and out of many PCMs is slow because of the low thermal conductivity of the PCM. However, heat transfer enhancers (HTE), such as heat pipes and fins may be added to enhance heat absorption and heat removal rates. Heat pipes have the inherent capability to transfer heat at high rates across large distances, even where the temperature difference is small. In this thesis a description is given of a PCS system consisting of paraffin wax as the PCM and which uses rectangular heat pipes in conjunction with aluminium fins to enhance heat transfer. The storage design is modular and each module has the characteristic that enhanced heat transfer in and out of the PCM is possible when the module is heated or cooled. It also has the capability to quickly absorb or alternatively to supply heat at a nearly constant temperature during the phase change of the module. A rectangular module was designed and built. The module was then analysed under controlled heat absorption and heat removal cycles. The heat up experiment involved an electrical kettle as the hot temperature source. The heat sink was a mains water heat exchanger. The experimental results were compared to those of a transient numerical model, which calculates theoretically how the module will perform thermally under the given test conditions. The numerical model of the experimental set-up was validated when it was found that the numerical model results resemble the experimental results. The numerical model was then adapted to simulate a novel solar water heater (SWH) with an additional PCS container. The improvement over previous designs is that the additional storage container can be heated to a higher temperature than the allowable geyser temperature. The system also heats up and cools down at a faster rate than would be possible without the HTEs. From the numerical simulation the size and performance of such a system is determined. This numerical analysis indicated that a phase change storage system in a SWH application will increase the hot water delivered by a given solar collector and geyser by increasing the storage capacity and by heating up the geyser overnight for early morning hot water use. / AFRIKKANSE OPSOMMING: Son energie is ‘n tyd afhanklike, hoë temperatuur radiasie energiebron. Die bruikbaarheid van ‘n sontermiese energie sisteem verhoog indien die hoë temperatuur bron beskikbaar is wanneer dit die meeste benodig word. Dit kan verwesenlik word deur die sonenergie termies te stoor. Termiese storing bied groter veelsydigheid aan ‘n sontermiese stelsel deur effektief die hittebron te ontkoppel van die hitte sink. ‘n Groot hoeveelheid energie kan, gedurende die smeltingsproses in ‘n faseveranderingsmateriaal binne ‘n nou temperatuurband gestoor word. Hierdie gesmelte materiaal kan weer op sy beurt in die waterverhittingstoepassing, die geabsorbeerde hitte teen ‘n konstante temperatuur oordra. In hierdie studie word ‘n sonwaterverwarmer stelsel wat aangepas is deur ‘n addisionele latente hittestoor daaraan te heg, voorgestel. Hierdie faseverandering hittestoor kan meer hitte stoor as wat water in dieselfde temperatuur band sou kon. Die hitteoordrag tempo na en van baie van die faseveranderingsmateriale (FVM) is egter as gevolg van die lae termiese geleidingskoëfisient, stadig. Hierdie eienskap kan gelukkig verbeter word deur hittepype en hitteoordrag verhogings materiaal soos vinne by te voeg. Hittepype het die inherente eienskap om hitte teen ‘n hoë tempo oor groot afstande, oor te dra, selfs oor ‘n klein temperatuurverskil. In hierdie tesis word ‘n ondersoek rakende ‘n faseverandering storingsisteem wat bestaan uit paraffien was as die FVM en reghoekige hittepype wat te same met met aluminium finne gebruik word om die hitteoordragtempo te verhoog, beskryf. Die stoorontwerp is modulêr en elke module het die kenmerk van hoë hitteoordrag na en van die FVM. Die module het verder ook die eienskap om vining hitte te absorbeer of hitte af te gee. Dit gebeur teen ‘n konstante temperatuur gedurende die faseverandering van die FVM. Presies so ‘n reghoekige module is ontwerp en gebou en onder beheerde hitte absorbering- en hitte verwyderingsiklusse analiseer. Tydens die verhittings eksperiment is ‘n elektriese ketel van gebruik gemaak wat gedien het as die hoë temperatuur bron. Die hitte sink was ‘n hitteruiler wat kraanwater van ‘n konstante hoogte tenk ontvang het. Die resultate van die volledige toets is met die resultate van tydafhanklike numeriese model vergelyk. Hierdie numeriese model bereken teoreties wat die module se storing verrigting onder gegewe toets omstandighede sal wees. Die numeriese model se resultate het goed vergelyk met die resultate van die eksperimente. Die numeriese model van die module is toe aangepas om ‘n sonwaterverwarmer met addisionele stoortenk wat fase verandering materiaal gebruik, te simuleer. Hierdie ontwerp is anders as vorige ontwerpe in die sin dat hoër temperature as wat die warmwatertoestel kan hanteer, in die faseverandering storingstenk, bereik kan word. Die sisteem kan ook as gevolg van die hitteoordrag verhoging materiaal, vinniger verhit of afkoel en teen ‘n vinniger tempo. Die simulasie van die sonwaterverwarmer met FVM word gebruik om die grootte en verrigting van die sisteem te bepaal. Hierdie numeriese model toon aan dat wanneer ‘n addisionele faseverandering storingstelsel in ‘n sonwaterverwarmer toepassing gebruik word, die warm water wat die verbruiker uit die sisteem kan verkry, kan verhoog. Die rede hiervoor is dat meer hitte gestoor kan word, wat beskikbaar gemaak word aan die warm water tenk.

The dissertation investigates typical operation modes of the heat storage tank in the small-scale cogeneration (CHP) plant, analyses formation of thermal stratifi-cation in such storage tank and presents the simulation of the stratification. The main aim of the dissertation is to investigate peculiarities of operation modes of heat storage tank in small-scale CHP plant, develop an algorithm allowing to choose the storage tank volume and present a model allowing determination of thermal stratification in the storage tank at any time of its operation. / Disertacijoje nagrinėjami būdingi šilumos akumuliacinės talpos veikimo režimai, susiformuojantys nedidelės galios kogeneracinėje jėgainėje, tiriamas šiluminės stratifikacijos susidarymas tokioje talpoje ir atliekamas jos modeliavimas. Pagrindinis disertacijos tikslas – ištirti nedidelės galios kogeneracinės jėgainės šilumos akumuliacinės talpos veikimo režimų ypatumus, sudaryti algoritmą, padedantį parinkti tokios talpos tūrį ir pateikti modelį, leidžiantį nustatyti šiluminę stratifikaciją akumuliacinėje talpoje bet kuriuo jos veikimo metu.

Phase change materials (PCMs) are a viable option for compact thermal energy storage. Effective designs using PCMs require accurate knowledge of the thermal and physical properties, but for many PCMs these are not well known, and when known the knowledge is sometimes contradictory. Therefore, physical characteristics of several promising PCMs (K3PO4·7H2O, FeCl3·6H2O, Mn(NO3)2·4H2O) were determined. In addition, a life cycle assessment (LCA) of dodecanoic acid in a solar thermal energy storage system was carried out to determine the environmental impact for energy storage. This LCA showed that dodecanoic acid in a solar energy system would save energy and facilitate CO2 reductions. However, the economic cost is high and is unlikely to be implemented without incentives. Finally an experimental testbed for a solar thermal system utilizing dodecanoic acid was built. Preliminary measurements demonstrated the utility of this system.