Masters’s thesis describes the use of solar energy for solar thermal systems used for domestic hot water heating. It is about the size of the incident solar radiation on Earth. Distributes various types of solar collectors for water heating. It deals with the monitoring, remote management of this system and the design of optimal control used in this area.

No description available.

In order to reduce emissions from the building sector, which stands for than a fifth of the global energy consumption today, efficient and fossil free heating and cooling systems are of importance. This study investigates the combination of solar photovoltaic thermal collectors and ground source heat pump systems in order to regenerate energy to the ground in combination with free cooling. Research questions investigated was how techno-economically efficient a system with photovoltaic thermal collectors, ground source heat pumps and free cooling in a commercial building is. Moreover, the study evaluates what benefits and challenges such system can have. In addition, Polysun as a modeling tool was evaluated for modeling a system includingthese components. Polysun was used as a model tool to first set up a replication of an existing system in TRNSYS provided by researchers at KTH. The model was then scaled and adjusted with parameters to represent a commercial building using free cooling from Vasakronan, a Swedish property company. Photovoltaic thermal collectors were added to the model of the existing building, with two different configurations, and the heating and cooling demand of the building was varied. The results showed that a configuration with photovoltaic thermal collectors added after the evaporator side of the heat pump generated more energy to the system compared with an installation before the evaporator side of the heat pump. The possibilities of free cooling decreased with increasing number of solar collectors, due to the rise of temperature in the ground. From an economic perspective, photovoltaic thermal collectors are more expensive than photovoltaic modules, since it has an additional cost for the hydraulic system that depends on the building. However, photovoltaic thermal collectors also provide thermal energy that can help balancing borehole systems and reduce the risk for a need of additional drilling. The study performed an uncertainty and sensitivity analysis of the results, showing that the electricity price is the most sensitive parameter to the net present value of investing in photovoltaic thermal collectors. With the electricity price assumed in this study, the net present values were positive for all cases for the given interest rate and lifetime of 25 years. It was also concluded that the modeling tool Polysun has a user friendly interface where energy systems easily can be modeled. In terms of borehole configurations, there is a lack of modeling alternatives which resulted in unexpected temperature rises in the ground for the model. / Byggnadssektorn står idag för mer än en femtedel av den globala energiförbrukningen, där över hälften av energin kommer från fossila bränslen. Därför är det viktigt med effektiva och fossilfria uppvärmnings- och kylsystem för att minska utsläppen, där värmepumpar är ett bra alternativ. Denna studie undersöker kombinationen av termiska solceller och bergvärmepumpssystem i kommersiella fastigheter, med syfte att återladda energi till marken i kombination med frikyla. Syftet var att undersöka hur teknoekonomiskt effektivt ett sådant system är och vilka fördelar samt nackdelar som finns. Dessutom utvärderades modelleringsverktyget Polysun som användes föratt modellera systemen. Arbetet inleddes med att efterlikna ett befintligt system i Polysun från en tidigare studie från KTH som använt modelleringsverktyget TRNSYS. Därefter justerades detta system så att det skulle efterlikna en av Vasakronans byggnader som idag använder bergvärme och frikyla. Tre scenarier konstruerades till basmodellen där samtliga innefattade termiska solceller. Resultaten visade att antalet termiska solceller kunde minska i antal då dessa var kopplade efter förångarsidan av värmepumpen, jämfört med om de är installerade före förångarsidan av värmepumpen. Genom att öka antalet termiska solceller i systemet ökade temperaturen i borrhålen, vilket ledde till en minskad möjlig användning av frikyla. Ur ett ekonomiskt perspektiv är termiska solceller dyrare än solceller som enbart genererar elektricitet, med en extra kostnad för det hydrauliska systemet som även beror på byggnadens utformning. Dock finns det andra fördelar med termiska solceller såsom att de kan hjälpa till att balansera borrhålssystem och minska behovet för att borra ytterligare borrhål. I studien utfördes en osäkerhets- och känslighetsanalys av resultaten, vilken visade att elpriset har stor påverkan på nettonuvärdet av en investering i termiska solceller. Med det elpris som antogs i denna studie var nettovärdet positivt för alla fall med den givna kalkylräntan och livstiden för systemet. Polysun visade sig vara ett modelleringsverktyg med ett användarvänligt gränssnitt där energisystem lätt kan modelleras. När det gäller konfigurationer av borrhål finns det begränsade modelleringsalternativ, där resultaten visade oväntade temperaturstegringar för marken i modellen.

Sverige har en hög andel installerade bergvärmepumpar, som är en typ av vätska-vatten värmepump. Ett problem som finns för befintliga bergvärmesystem är att berget med tiden kyls ned då returslangen till borrhålet konstant levererar kyla till berget. Till följd av detta mister systemet en betydande del av sin verkningsgrad samtidigt som det i extrema fall kan leda till permanent isbildning i borrhålet. Ett sätt att motverka detta problem är att tillämpa termisk energilagring i bergvärmesystemets borrhål. Den internationella benämningen för denna teknik är ”Borehole Thermal Energy Storage, BTES”. Rapporten har behandlat en friliggande enplansvilla med ett befintligt bergvärmesystem som tillämpar termisk energilagring i bergvärmesystemets borrhål med solvärme. Två beräkningsfall har gjorts och resultatet från simuleringarna i en upprättad beräkningsmodell visar att en temperaturhöjning i borrhålet inte alltid innebär en årlig energibesparing. Vid varje grads temperaturhöjning sker en ökning av värmepumpens COP med ca 1,85 % enligt ett linjärt samband för höga temperaturdifferenser över värmepumpen. Detta motsvarar en kostnadsbesparing på 1,02 %/°C. Detta gäller för normala förhållanden med en framledningstemperatur för tappvarmvatten och rumsvärmare på 55 ⁰C. Med en högre energiförbrukning finns alltså större besparingar att göra. Vid mycket låga temperaturdifferenser mellan förångare och kondensor sker dock större procentuella förändringar, vilket medför att lågtemperatursystem kan bidra till en större energibesparing. I normalfallet är dessa system svåra att räkna hem för småhus. För en god lönsamhet krävs en optimerad systemlösning och effektiv styrning av cirkulationspumpar och andra samspelande komponenter med en PLC. I framtiden kommer dock sannolikt värmepumparnas mekaniska verkningsgrad att öka med bättre teknik och även energipriset som följd av politiska beslut, tillgång etc. Detta innebär att varje besparad kilowattimme kommer att bli mer värd. / Sweden has a high proportion of installed geothermal heat pumps, which are a type of liquid -water heat pump. One problem that exists for existing geothermal heating systems is that the rock in time cool down when the return hose to the borehole constantly supply cooling to the rock. As a result of this the system loses a significant portion of their efficiency while in extreme cases has led to the permanent ice in the borehole. One way to counter this problem is to apply thermal energy storage in the geothermal heating systems borehole. The international term for this technique is "Borehole Thermal Energy Storage, BTES". This report has analyzed a detached single storey house with an existing geothermal heating system utilizing thermal energy storage in the geothermal heating systems borehole with solar heating. Two calculation cases has been made and the results of the simulations in an established computational model shows that an increase in temperature in the borehole does not always result in an annual energy savings. Each degree of increased temperature is an increase in the heat pumps COP of 1.85 %, according to a linear relationship for high temperature differences across the heat pump. This results in a cost saving of 1.02 %/°C. This applies to normal conditions with a radiator temperature at 55 ⁰ C. With higher energy consumption can greater savings be made. At very low temperature differences between the evaporator and condenser is however larger percentage changes made, which means that low temperature systems can lead to greater energy savings. Typically, these systems are difficult to recoup for small detached houses. For a good profitability requires an optimized system solution and efficient control of circulation pumps and other interacting components with a PLC. In the future the heat pump mechanical efficiency will probably increase with better technology and even energy prices as a result of political decisions, access, etc. This means that each spared kilowatt hour will be worth more.

As energy prices keep increasing, energy efficiency measures have come to the spotlight, especially in the residential sector. In this context, energy audits appear as powerful tools in order to assess the energy use and cost of energy of a dwelling, and identify possible energy saving measures that increase the energy efficiency and reduce costs. This work performs an energy audit of a single-family house (SFH) built in the 1970s which uses district heating, located in Gävle, Sweden. An empirical and quantitavive approach is followed, where energy data from the bills of 2022 together with on-site ventilation measurements is combined as a way to determine the energy inflows and outflows of the dwelling. Results concluded that the ventilation needs to be improved as a way to meet the Swedish building regulations. In addition, the energetic situation could be improved by means of the installation of solar photovoltaic (PV) modules to cover part of the electricity demand and solar thermal collectors to cover part of the domestic hot water demand. These measures would decrease the costs of the energy bills 4689 SEK/year at the time they would provide a source of renewable energy. The replacement of windows was also studied, concluding the payoff time to be excessively long to be accepted.

No description available.

[pt] Altas resistências elétricas em série e baixas resistências em paralelo são fontes de perdas em dispositivos Fotovoltaicos (PV). Em dispositivos que operam sob concentração, esses costumam ser os principais fatores limitantes para o aumento da eficiência de conversão. Excluindo fatores externos associados a falhas no processo de produção, a resistência elétrica em série depende de fatores intrínsecos aos materiais e à estrutura de camadas do dispositivo fotovoltaico. Dessa forma, para minimizar o seu valor é extremamente importante planejar adequadamente esses parâmetros construtivos antes da produção dos dispositivos. Um dos fatores mais impactantes na resistência em série é o desenho da malha de dedos coletores do contato elétrico frontal. Por outro lado, minimizar a resistência em série do contato elétrico requer o aumento da área metálica da superfície frontal, que serve de janela para a radiação solar. Portanto, deve haver um compromisso na redução das perdas elétricas e ópticas. Nesse trabalho, apresentamos os resultados da otimização do desenho da malha de dedos coletores para o contato elétrico frontal para três diferentes geometrias obtidas por algoritmos genéticos. As geometrias escolhidas foram a retangular, tradicional para a produção desse tipo de dispositivo, a hexagonal e a diamante. Além disso, comparamos os resultados obtidos com os de um dispositivo produzido com uma malha otimizada por um método de cálculo analítico. Ao final, discutimos as melhorias introduzidas pelas novas geometrias e apresentamos a configuração otimizada, que foi obtido para uma célula solar de tamanho 5x5 mm com uma estrutura retangular de fingers, com uma redução de perdas de 54,42 por cento que leva a um aumento aproximado de 1,40 por cento em eficiência. / [en] High electrical resistances in series and low resistances in parallel are sources of losses in Photovoltaic (PV) devices. In devices that operate under concentration, these are often the main limiting factors for increasing conversion efficiency. Excluding external factors associated with failures in the production process, the series electrical resistance depends on factors intrinsic to the materials and the layer structure of the photovoltaic device. Thus, to minimize their value it is extremely important to properly plan these constructive parameters prior to the production of the devices. One of the most striking factors in the series resistance is the design of the mesh of collecting fingers of the frontal electrical contact. On the other hand, minimizing the series resistance of the electrical contact requires the increase of the metallic area of the frontal surface, which serves as a window for solar radiation. Therefore, there must be a commitment to reduce electrical and optical losses. In this work, we present the results of the optimization of the design of the mesh of collecting fingers for the frontal electrical contact for three different geometries obtained by genetic algorithms. The geometries chosen were the rectangular, traditional for the production of this type of device, hexagonal and diamond. In addition, we compared the results obtained with those of a device produced with an optimized mesh by an analytical calculation method. At the end, we discussed the improvements introduced by the new geometries and presented the optimized configuration. which was obtained for a solar cell of size 5x5 mm with a rectangular structure of fingers, with a reduction in losses of 54.42 percent that leads to an approximate increase of 1.40 percent in efficiency.

In 1890, famed Scottish novelist Robert Louis Stevenson settled with his family at an estate called Vailima, outside Apia, Samoa, following two years of cruising around the Pacific. While in Oceania, the family assembled a large collection of tapa, or barkcloth, from various islands, the majority of which were received as gifts from Indigenous associates, staff, and dignitaries. These textiles are evidence of, witnesses to, and participants in a remarkably global and interwoven history of Victorian-era colonial exchange. My dissertation utilizes this suite of objects to reposition Stevenson’s legacy in the region as well as to challenge existing methodological norms in the history of collecting, expanding the possibilities of how we determine provenance in the colonial Pacific. Drawing on the framework of collaborative collecting, or co-collecting, established by Sean Mallon, I expand the attribution of this collection to multiple actors, recognizing many proactive Pacific Islanders who strategically gave the family gifts of barkcloth, including chief Mata’afa Iosefo. I also argue that Stevenson’s wife Fanny should be viewed as a passionate collector of barkcloth and I situate her activities in a broader conversation about gender and the controls frequently imposed on female collectors. I turn in closing to contemporary Samoan writers and thinkers, centering their explorations of Stevenson’s legacy in Samoa. The tapas I center are revelatory objects, and studying their exchange illuminates their givers and receivers, as well as the social and cultural networks in which they circulated.

The aim of this thesis is to determine the mechanical properties of copper, titanium and carbon thin films deposited on foil substrates, and identify how the properties are affected by the deposition process. This is important when such coated foils are subjected to mechanical deformation during applications. Three coating materials, Cu, Ti, and C, were evaluated on PET and Al foils. The materials were deposited by direct current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HiPIMS). The crack initiation and propagation during tensile tests were investigated in-situ by a SEM. The coatings’ crack onset strain (COS), cohesive strength, interfacial shear strength (IFSS), and Weibull shape and scale parameters were successfully determined from the experimental data. The results showed the Cu coatings had similar cohesive strengths and IFSS, independent of the deposition process. The main difference was the COS, where thin films deposited with ion assistance displayed a higher value. The coatings also displayed different morphologies that clearly influenced the crack propagation. Larger grains hindered the crack propagation and resulted in a more ductile fragmentation, with coatings displaying short and tortuous cracks. All Ti films displayed similar fragmentation and thus mechanical properties, despite small differences in morphology. However, the surface roughness of the Al foil influences the results. Localized stresses arise in the rolling tracks from the foil production and facilitates the crack propagation, thus affecting the fragmentation of the coatings. Lastly, it could be shown that the addition of a thin Ti adhesion layer resulted in a fully adherent C film.

No description available.