Numerical and experimental investigations of tidal current energy extraction have been conducted in this study. A laboratory-scale water flume was simulated using commercial computational fluid dynamics (CFD) code FLUENT. In the numerical model, the tidal current turbine is represented with an actuator disk, which produces a pressure drop associated with energy loss. The free water surface is considered in the model using a volume of fluid method and is allowed to deform freely. Numerical results identified that a localised wake is formed behind the tidal current turbine and there is considerable localised flow acceleration around and most especially, under the energy extraction device. A free water surface drop is visualised in the model results due to the energy extraction and this free surface drop is believed to have an impact on the recovery of turbine wake. The influence of other parameters like water depth, ambient turbulence and flow speed on the tidal current energy extraction are also testified, based on the numerical model. Numerical results demonstrated that, because of the existence of a free water surface, tidal turbine interaction with the flow is a complicated three dimensional problem. Therefore, completely using the theoretical methods of wind turbines for tidal current turbine study would be inappropriate. Two physical tests were deigned for the experimental investigation of energy extraction from tidal currents and were carried out under different testing conditions: one was in moving water using a natural open channel and the other was in still water using a towing tank. Comparing experimental and numerical results of wake velocity profiles, good qualitative agreement has been obtained, which proves that the proposed numerical model can provide essential insight into the mechanism of wake development behind tidal current turbines. Experimental results also confirmed that, although moving water is the real operational condition of tidal turbines, a towing tank is still an ideal facility for the experimental study of tidal turbines, especially at the early stages of understanding of the detailed physical processes governing the performance of rotors and turbine wake behaviour. This study is a comprehensive investigation into tidal current energy extraction at laboratory scale. Environmental impact of tidal current energy extraction is further recognized and an appropriate experimental facility for the model testing of tidal energy extraction devices is recommended.

Detta examensarbete utfördes på uppdrag av Umeå Kommun. Uppgiften bestod av att utvärdera dagens användning av en borrhålsbrunn samt undersöka vad som är det optimala användningsområdet för borrhålsbrunnen. Borrhålsbrunnen används i dagsläget för att förvärma samt kyla utomhusluft in till kontorsbyggnaden Kubens ventilationsaggregat. Ventilationens förvärmning består av två delar, en markkanal och ett geoenergibatteri. Viktiga parametrar hos förvärmningen analyserades med hjälp av mätvärden för temperatur och flöde. Resultaten jämfördes därefter med alternativet att använda borrhålsbrunnen tillsammans med en värmepump. Då borrhålsbrunnens kapacitet inte var tillräcklig för att klara byggnadens hela uppvärmningsbehov, undersöktes det hur en värmepump skulle kunna köras i kombination med fjärrvärme. Två driftstrategier, Bas och Kapatoppar, undersöktes. Bas leverar en basproduktion under hela vinterperioden medan Kapatoppar startar vid -6°C för att sänka effekttoppar. Utvärderingen av förvärmningen visade att geoenergibatteriet är mer kompatibelt med ventilationsaggregat av VAV-typ (Variable Air Volume) än vad markkanalen är. Däremot är inte förvärmning i kombination med roterande värmeväxlare ett bra koncept för byggnaden som den används idag. På grund av att förvärmningen är placerad före den roterande värmeväxlaren så är bara 15-20 % av förvärmningseffekterna energibesparande. Detta kombinerat med en optimerad drift av aggregatet sett till tidsstyrning och behovsstyrning av flöde gör att förvärmningen har en liten påverkan både på byggnadens maximala effektbehov och totala energibehov. Att köra värmepump i kombination med fjärrvärme för uppvärmning var ekonomiskt lönsamt främst på grund av att värmepumpen kunde kapa byggnadens effektoppar. Kostnaden för storleken på den abonnerade effekten uppgår idag till drygt 40 % av den totala fjärrvärmekostnaden. Dagens relation mellan el- och fjärrvärmepriser bidrog naturligtvis också till att värmepumpsalternativet var lönsamt. För de undersökta förutsättningarna så blev paybacktiden för en värmepump med den lönsammaste driftstrategin, Bas, 4,4 år.

Biomass is characterized by highly variable properties. It can be converted to more valuable energy forms and products through a variety of conversion processes. This thesis focuses on addressing several important issues related to combustion and pulping. Experimental investigations were carried out on a biomass-fired industrial fluidized-bed boiler. The observed combustion asymmetry was explained by an imbalance in the fuel feed. Increased levels of carbon monoxide were detected close to boiler walls which contribute significantly to the risk of wall corrosion. Moreover, extensive literature analysis showed that near-infrared spectroscopy (NIRS) has a great potential to provide property information for heterogeneous feedstocks or products, and to directly monitor processes producing/processing biofuels in real-time. The developed NIRS-based models were able to predict characteristics such as heating value, ash content and glass content. A study focusing on the influence of different spectra acquisition parameters on lignin quantification was carried out. Spectral data acquired on moving woodchips were found to increase the representativeness of the spectral measurements leading to improvements in model performance. The present thesis demonstrates the potential of developing NIRS-based soft-sensors for characterization of biomass properties. The on-line installation of such sensors in an industrial setting can enable feed-forward process control, diagnostics and optimization.

Ethiopia has been facing problems regarding power generation, distribution, balancingbetween demand and supply and access to modern energy service. About 92.4% of energysupply is from biomass (mostly in traditional) 5.7% oil which is not friendly with theenvironment and about 1.6% of energy supply is from renewable energy resource,hydropower plants.Being dependent on hydropower plant causes the country to face many challenges indistribution and balancing demand and supply. This thesis provides another way ofconsidering and implementing renewable energy resource (solar energy resource) throughtechnologies like grid-connected roof mounted solar PV system and CSP plant with the helpof PVGIS, PVWatt and SAM software.This thesis aims to come up with an idea that will work out for current engineering, socialand political issue that is seen in the country. Considering new way in planting PV system onthe roof is strongly recommended and increasing the alternative sites for power generationalong with the appropriate technology is recommended as another way. The possibility andpower generating efficiency is checked through each application.Based on the demonstration in all software’s used, it is clearly visible that the country couldhave been satisfied the needed demand and become the hub of east Africa as mentioned inthe policy and strategy. However, this dependency causes the country to insufficiently supplythe need. Apart from the possibilities and estimation, ideas that might help the country tocome over these challenges are provided in recommendation section.

The use of plug-in electric vehicles (PEV) is rapidly growing in many countries. In Sweden the number of PEVs in the transport system grew from about 43 000 in December 2017 to almost 58 000 in July 2018. To fully load a discharged PEV battery in a reasonably brief time will require high charging powers, which might cause high peaks in the power grid. The purpose of this project was to investigate the possibilities for electricity production in combined heat and power (CHP) plants to balance the demand peaks in the power grid caused by charging PEV. Data were obtained from different heat production plants in two Swedish cities, Borlänge and Falun. The cities, which have interconnected district heating systems, have a broad spectrum of different types of heat producing plants, and thus functions as an example model of a “typical northern Europe” heating system. An artificial charging load profile was created for a system of a large number of PEVs forming a scalable load. The charging load profile was then used as input in CHP plant models, to generate the heat production profile for the CHP plants in the system. The heat profiles were then used as inputs in a district heating simulation software. The complete Borlänge-Falun heat production system was simulated to find out whether it is possible to operate the CHP plants based on the PEV charging load profile. The generated heat production profiles were similar and clearly followed a pattern that was in line with how the heat and electricity output relate in a CHP plant. The results showed that during periods when the heat demand is high, the CHP plants can operate at full load and are thus capable to fully regulate the charging of the PEVs. During periods when the heat demand is low, and the CHP plants are unable to operate on full load, there is a discrepancy between the CHP plants ability to produce electricity and the PEVs charging demand. If the plants are operated at full load even though the heat demand is low, the heat surplus will be lost unless the system is equipped with a large heat storage. This lost heat will lead to increased costs unless there are control means to compensate the CHP plant operator for the peak regulating services as such provided. Furthermore, constructing an energy system were heat is intentionally wasted might not be considered a sustainable solution. The CHP plant regulating system can, however, be combined with other local regulating, e.g. load control, to minimise the heat wasted.

The expansion of photovoltaic plants has increased significantly within the EU and in Sweden, where a contributing cause has been a higher environmental thinking and lower prices for solar cell installations. Interest in installing solar cells has increased in society as a whole and an increasing number of municipalities are interested in solar cells. One of these municipalities is Forshaga municipality, which strives to be climate neutral until 2030. This study examined whether a number of selected municipal properties in the Forshaga municipality were suitable for installing solar cells based on the degree of self-use and the degree of self-sufficiency and the electricity cost of produced electricity (LCOE - Levelized cost of energy). The study also examined whether these selected properties would be suitable for solar cells if certain conditions were changed to simulate that they were located in another location with different conditions. Of the properties included in the study, there was a care home, two schools, Forshaga municipal house, a wastewater treatment plant and a waterplant. Of the examined municipal properties, a school, the nursing home and the municipal house were considered most suitable for solar cells based on the above criteria. The property that was considered most suitable was the Grossbolskolan which was the smaller of the two schools. Grossbolskolan had a self-utilization rate and a self-sufficiency rate of 87 and 15 percent respectively and the lowest cost for the produced electricity by about 0.88 SEK/kWh. The municipal house and the care home had a slightly higher production cost for the produced electricity. Some conclusions could be drawn from the part of the study that examined whether the properties were suitable for mounting solar cells if they had been placed in another location with other conditions. One conclusion was that the properties should have a similar electricity consumption as the investigated properties in this study, with a higher electricity consumption daytime when the solar cells produce the most to obtain a high self-use. The degree of selfuse was highest for the plants that were located in the east / west direction, which indicates that the electricity consumption in these type properties was more suitable for solar cell installations whose production is more widespread throughout the day. In order for the repayment period not to exceed the assumed life expectancy of the solar cell plant of 25 years, the self-use rate should not be less than 50 to 60 percent. Finally, the study also found that the properties recommended as suitable had between 1 - 3.5 m2 solar cells / MWh annual electricity use in the property, which can be used as a guideline value to see if the property is suitable for solar cells. If this value were lower, the self-sufficiency rate was low, if it was greater, the self-utilization rate was low.

Sustainable development is a development that meets the needs of the present without compromising the ability of future generations to meet their own needs. However, today’s use of resources is higher than what earth can sustain and therefore the linear economy, where resources become waste right after usage, needs to evolve into a more circular one, an economy that uses and reuses resources in a more efficient way. To enable a development into a more circular economy, it’s important to design products that can be repaired, reused and recycled. Both the steps before and after waste arise are of importance. In upstream management the focus is on design and manufacturing of products and in downstream management the focus is on waste management methods. This master thesis studies the future urban district, Ebbepark, which is under development in Linköping, Sweden. The thesis studies the role of communication, design and visualization to minimize the environmental impact from waste management in an urban area with a mix of housing and offices. It is studied how the waste system can be designed to facilitate for its users to make the right decisions and how to reach out with messages and information about waste and consumption. The focus of the work lies on finding strategies to develop the waste management according to the waste hierarchy introduced by the European Union. A literature review was conducted laying the ground for the study. Interviews were held with people with knowledge and experience of waste management. A web survey was done with office workers in Linköping to find out their experiences regarding the waste system and consumption in the office environment and at home. Psychology and behavioral economics were studied to ascertain how human behavior can be altered. Important factors when it comes to waste are ease and information. To be able to leave your waste close to home is important and many would appreciate if recycling bins were included in their homes, which the housing enterprises should consider. In a densified district, lack of space is extra obvious and space for waste is seldom prioritized. According to Swedish law, commercial and domestic waste need to be treated separately, which means that a lot of space is required in Ebbepark to handle waste from households and offices. A great part of the commercial waste can however be thrown away at the same places as the domestic waste in Ebbepark. With services collecting office paper, a proposed collaboration regarding packaging material and access to the pneumatic waste system, only 1-4 % of the office waste remains and must be treated separately. The social impact people feel can be used in the waste system to improve human behavior. Collection sites that for example are light and open and located at places where people move, contribute to the social norm and increase the feeling of safety. The system information should be simple and straightforward and pictures and colour coordination can facilitate. At the same time people must have the right conditions to make sustainable choices. Strategies should be built on peoples experienced obstacles and advantages. Information and communication should be designed after their conditions and nudge them in the right direction. The housing enterprises have a responsibility to make sure there is a range of services that prevent waste and reuse products. Plastic is a material with great environmental impact in downstream management, partly because of the release of fossil carbon dioxide when incinerated, why actions to reduce the use of plastic material and increase the recycling is needed. Future studies should investigate how larger lifestyle changes can be achieved and how the municipal waste monopoly and the producer responsibility should be designed in the future to favor circular solutions. / Hållbar utveckling är en utveckling som tillgodoser dagens behov utan att äventyra kommande generationers möjlighet att tillfredsställa sina behov. Dagens resursutnyttjande är dock högre än vad jorden klarar av och dagens linjära ekonomi, där resurser används och sedan blir till avfall, behöver utvecklas till en mer cirkulär ekonomi, där resurser tas tillvara och blir till nya produkter efter användning. För att möjliggöra utvecklingen mot en cirkulär ekonomi är det viktigt att produkter designas för att kunna repareras, återanvändas och till sist materialåtervinnas. För att hanteringen av avfall ska bli mer hållbar är det därför viktigt att både fokusera på stegen innan avfall har blivit till och hanteringen av avfallet. Därför talas det om uppströms arbete, där fokus ligger på design och tillverkning av produkter och nedströms avfallshantering där fokus ligger på olika behandlingsmetoder för avfall. Det här examensarbetet studerar den framtida stadsdelen Ebbepark som byggs i Linköping. I arbetet studeras hur kommunikation, design och visualisering kan användas för att på ett effektivt sätt minska miljöpåverkan från avfallshantering i ett område med en blandning av kontor och bostäder. Det studeras hur avfallssystemet kan utformas för att underlätta för användarna att göra rätt samt hur budskap och information kring avfall och konsumtion kan nås ut med. Fokus i arbetet ligger på att hitta strategier för att lyckas utveckla avfallshanteringen i enlighet med EU:s avfallshierarki. En litteraturstudie har genomförts för att lägga grund till arbetet, därefter har intervjuer med personer insatta i avfallsområdet hållits samt en enkät har skickats ut till människor som arbetar i Sankt Kors kontorslokaler samt Swecos kontor i Linköping för att undersöka deras syn på avfallshantering och konsumtion på arbetet och i hemmet. För att studera hur människors beteende gällande konsumtion och avfall kan ändras har psykologi och beteendeekonomi studerats. Viktiga faktorer när det kommer till avfall är bekvämlighet och information. Att kunna lämna avfall nära hemmet är en viktig faktor. Många skulle uppskatta att det ingår kärl för källsortering i deras bostäder, vilket bostadsföretagen bör ta hänsyn till. I en förtätad stadsdel blir utrymmesbrist extra påtagligt och avfallsutrymmen prioriteras gärna bort. Verksamhetsavfall och hushållsavfall måste hanteras separerat idag enligt lagstiftning, vilket bidrar till att mycket utrymme måste tas i anspråk för att hantera avfallet från bostäder och kontor i Ebbepark. Det finns dock möjlighet att slänga en stor del av verksamheternas avfall i samma utrymmen som hushållsavfallet i Ebbepark. Med tjänster för hämtning av kontorspapper, ett föreslaget samarbete kring emballage och tillgång till sopsugen återstår endast 1–4 % av verksamheternas avfall som måste hanteras separat. Den sociala påverkan som människor känner kan användas i avfallssystem för att beteenden ska förbättras. Insamlingsplatser som exempelvis är ljusa och öppna och ligger på en plats med mycket rörelse bidrar till den sociala normen och ökar tryggheten. Information i systemet måste vara enkel och tydlig, gärna med bilder och färgkoordinering. Samtidigt måste det finnas förutsättningar för att göra hållbara val. Strategier bör bygga på människors upplevda hinder och fördelar och information och kommunikation bör utformas utifrån deras förutsättningar som knuffar dem i rätt riktigt. Fastighetsbolagen har ett ansvar att se till att det finns ett utbud av verksamheter och tjänster för att förebygga avfall och återanvända produkter. Plast är ett material som har stor miljöpåverkan nedströms i avfallshanteringen, delvis på grund av koldioxidutsläpp vid förbränning, därför bör åtgärder riktas mot att minska användningen och öka materialåtervinningen av plast. Vidare behövs det studeras hur större livsstilsförändringar kan fås igenom samt hur det kommunala monopolet och producentansvaret ska utformas i framtiden för att gynna cirkulära lösningar.

In a risk situation the flow through a hydropower turbine must be reduced under a short amount of time. The reduction in flow causes low pressures in the region called draft tube under the runner in the turbine. If the pressure drops below vapor pressure the water in the turbine may evaporate and form large cavities. The phenomenon called water column separation describes the situation when these cavities of vapor forms and eventually collapses which may damage the unit and canbe a danger to personnel at site. Different types of flow reducing maneuvers are tested before commissioning turbines in order to detect dangerously low pressures but these measurements can be difficult to interpret. The measured draft tube pressure can be filtered numerous ways and in addition other measured or calculated parameters must be studied to fully understand the consequence of a measured emergency stop. In this paper the different ways of filtering and interpreting the measurements from stops in Kaplan turbines were analyzed. The results show that the choice of filtering method can significantly impact the interpretation of a stop and that the filter parameters often used do not result in equivalent results. The standard way to filter draft tube pressure with moving average filters is shown to result in much higher draft tube pressures than low-pass filters and the filter parameter used needs to be further investigated to correctly isolate pressures caused by water column separation. The main difference between different companies when it comes to these measurements are the used cutoff frequency when using low-pass filters and the sampling frequency of measurements.

This thesis will investigate possible energy storages in Luleå Energi’s power grid within a five-year period. The transition to a more sustainable and efficient energy system, in response to climate change, creates new challenges for the power grid. Energy storage has, according to many sources, the potential to contribute to meet the challenges that arise from a larger share of intermittent renewables, a growing number of electrical vehicles and increased demands for reliability and stability. Several reports conclude that currently energy storages are most profitable in customer applications, especially in combination with micro-production, e.g. solar cells. Therefore, this report will investigate if battery storages could be installed in three multi-residential properties with solar cells, with the purpose to increase self-use of electricity generated from the solar cells and peak-shaving. Batteries have been chosen as storage technology, since they currently seem to be the technology with the most potential. Possible savings for the customer as well as potential benefits for the grid will be considered. Based on data for the properties’ consumption and solar power production, an analysis has been made to see how much excess electricity the solar cells generate and to identify peak demands. Regarding the solar cells, data has only been available for a few months. For other days, the production has been estimated base on measurements of global radiation over Luleå municipality. A simulation in MATLAB has then been carried out to dimension the battery. When customers connect micro-production to the grid, the voltage may rise above permissible limits, especially in weaker rural grids. As a result, reinforcements of the grid may be necessary, which means expenses for the grid owner. Installation of a battery, that can store energy and keep the voltage within permissible limits, could be an alternative. The report considers such a case and makes a comparison between reinforcements of the grid and installation of a battery.   The results of the report show that energy storages have several potential benefits, both for customers, grid owners and system operators. Forecasts point to a strong growth, as well as lowered battery prices, which could lead to investments that are more profitable. The study of installing a battery in properties with solar cells shows that an increased self-use and peak shaving is possible. However, the economic results show negative net values. This means that currently the investment is not profitable. Approximately, battery prices must be cut in half to reach profitability. The calculation concludes that power tariffs enables most savings for the customers and gives them incentives for peak-shaving. The report also shows that the amount of micro-production in a rural grid can be limited by the strength of the grid. If five customers in the investigated part of the grid each would install 8.6 kW solar power, the voltage rise at the point of common coupling would go above permissible values, and the grid would have to be reinforced. The economical comparison between investing in new cables and installing a battery storage shows that currently, a battery storage is more expensive than a new cable. The overall conclusion from the report is that energy storage has the potential to contribute to the transition of the energy system. However, regulations and battery prices currently limit the possibilities for profitable investments. It is recommended to do an oversight of regulations and new business models to enable more investments in energy storage. Studying alternative tariffs is also important, to create incentives for a more efficient use of the power grid.

This thesis studied the possibilities to monitor disconnectors’ operating times to indicate when maintenance needs to be performed. The main hypothesis of this study was that the operational time in a disconnector manoeuvre, open or close, correlates with the resistance in the mechanical components. If the operational time deviates too much from the baseline duration, then this may indicate that the disconnector needs to be maintained. Five substudies were conducted to study if it was possible to monitor the operating time and if the logged operating times had been affected by external conditions. Together they illustrated it might be possible to monitor operating times, but this study cannot state it with certainty based on the available data. From the results, it was possible to see that normal operating times for disconnectors varied within a group of disconnectors of the same type and manufacturer. Why it differed within groups of the same type and manufacturer might be explained by the effects of external conditions. It was shown that a varying transfer time occurred when logging the operation times in the front end processor. Furthermore, the year of production of the disconnector affected the median operating time, but it did not affect the operating time in an intuitive way, that is the operating time did not get longer for older disconnectors. Also, the geographical position of the disconnector may affect the operating time. When these external conditions were considered, disconnectors were concluded necessary to be studied individually. If disconnectors would be studied individually condition monitoring might be possible, although, it is not possible at the moment because of the lack of observations per disconnector.