Energy poverty is defined as the lack of access of households in developing countries to modern energy sources, and their consequent reliance on solid biomass fuels for cooking. So-called “Improved stoves” have been promoted by various public and private actors since the 1970s to tackle various environmental and health challenges associated with biomass use. Impact studies of such projects are usually based on on-site surveys about the stoves’ use, and thus are extremely site-specific, and difficultly generalizable. This thesis project aims to introduce a novel approach to impact assessment of improved cooking stoves on both local energy needs and deforestation in the area. This approach will base most of its figures and assumptions on calculated energy needs rather than survey reports. This will result in a highly flexible energy model, which can be used and adapted to help decision and policy makers in their function. The area of Nyeri County, Kenya, where the author completed a one-month field study, is used throughout the thesis as a case study in order to validate the model.

The world energy production, transformation, storage, and usage are under a dramatic change. Actions are being taken by Governments to slow down the effects of the climate change. Wind energy is expected to be a central pillar for this change. However, a key issue facing the expansion of wind energy, especially in Sweden, is the integration of the massive amounts of new generation into the electricity grid (Energinet et al., 2021; Ingeberg, 2019; IVA, 2020). Another challenge facing the expansion of the wind energy is that it can’t be used by end-sector which rely on energy-dens carriers (IRENA, 2020b). In the pursuit of solutions to these challenges, green hydrogen produced by offshore wind energy emerges an alternative. Motivated by the recent Swedish plans to develop offshore wind power capacity in the Baltic Sea, as well as the problematic environmental statues in the Baltic Sea, this work investigate the cost of green hydrogen produced from offshore wind energy in Sweden and evaluates the environmental impacts of utilizing by-product oxygen on the marine ecosystem in the Baltic Sea.  The first step of this work considers the economic feasibility of a 2 GW offshore wind energy dedicated for hydrogen production in the Baltic Sea outside Sweden, with three alternative electrolyzer placement: onshore electrolyzer (III), centralized offshore electrolyzer (II), and decentralized offshore electrolyzer (I). The proposed assessment of this work investigated the hydrogen production cost using electricity from offshore wind energy in the Baltic Sea in Sweden. The LCoE and LCoH in relation to three configurations reflecting the electrolyzer placement were analyzed and compared. The electrolyzer operation at nominal capacities of 06%, 65%, and 70% were considered for the three configurations. The results shows that the LCoE and LCoH differed between the three configurations. The results showed that the lowest LCoE and LCoH is achieved by the configuration where the electrolyzer system decentralized at the turbine platform at a price of 1.7 €/kg. Reflecting the impact of the electrolyzer nominal capacities, which are at 60%, 65%, and 70%, on the LCoH, the result showed that the three configurations are equally competitive. However, when the nominal capacity of 65% were compared among the three configurations, it was showed that the LCoH at the onshore electrolyzer were 2.6 €/kg compared to the LCoH at the centralized electrolyzer which resulted in LCoH of 2.7 €/kg. The second step of this work considers the evaluation of the environmental impact of artificial oxygenation by reviewing existing studies. The results of the reviewed studies on the environmental impacts of artificial oxygenation indicate that the utilization of the by-product oxygen would contribute to important environmental benefits for the Baltic Sea. The use of the by-product oxygen to oxygenate would maintain the processes that removes nutrients, keep the sea water oxygenated, and the seabed habitable for marine animal. There are, however, some aspects that need to be considered and understood when planning for oxygenation, such as the complicated physical and biogeochemical interactions. Hence, this requires further studies and investigations.

<p>Solar thermosiphons integrated into the thermal envelop of buildings has been studied for their potential to take advantage of solar energy in heating buildings. The annual performance of solar thermosiphons cannot currently be predicted with the correlations from previous research. Also, no work has been done on the supply mode of a solar thermosiphon even though it has the potential to provide heating and fresh ventilation air. An investigation was done with the goal of developing a numerical model that could predict the performance of the supply mode of a solar thermosiphon. The numerical model included infrared thermal radiation and conduction through the glass, phenomenon which had not been used in previous numerical models. To validate the numerical model a novel steady state experiment was developed. This experiment included radiation as the heat source and the ability to vary geometric lengths. The performance parameters of mass flow rate and thermal efficiency were comparable between the numerical predictions and experimental results. However, due to uncertainties in the current experimental setup, full validation of the numerical model was not possible. These uncertainties would have to be addressed before the numerical model that was developed can be fully validated and used for generating correlations. After consideration of practical implementation constrains, it was shown that it was easier to implement the indoor air curtain mode of a solar thermosiphon than the supply mode. The indoor air curtain mode provides the same amount of energy from solar radiation to heat a building as the supply mode of a solar thermosiphon.</p> / Master of Applied Science (MASc)

<p>In an effort to better understand the physical mechanisms responsible for pool boiling heat transfer, an analytical model is developed that better describes the changing shape and size of a growing bubble. Indeed, any analysis of thermal transport due to nucleate pool boiling requires bubble frequency predictions which are intimately linked to bubble volume. The model is developed and validated for quasi-static bubble growth due to gas injection and for bubble growth due to vaporization within the heat-transfer controlled growth regime; it highlights the need to include the asymmetric nature of growing bubbles when modeling bubble growth.</p> <p>In addition, a numerical study of quasi-static bubble shape for both adiabatic bubble growth and vapour bubble growth provides insight into the dependence the bubble shape evolution has on the Bond number. In so doing, bubble profiles generated from a numerical treatment of the Capillary equation are benchmarked to quasi-static gas injected bubble formations and to heat-transfer controlled vapour bubble formations.</p> <p>The numerical treatment of bubble shape evolution leads to a simplifying bubble geometry for low Bond number applications. The geometric model accounts for bubble shape transformation throughout the bubble growth cycle including the necking phenomenon. An analytical model of quasi-static adiabatic bubble growth is accordingly developed based on the proposed low Bond number geometric model; it is coupled with a geometric detachment relation and a force balance detachment criterion that are dependent on the Bond number. The resulting predicted bubble growth characteristics, such as profile, volume, centre of gravity and aspect ratio, are validated with the benchmarked numerical treatment of the problem.</p> <p>Furthermore, the low Bond number geometric model is applied to bubble growth due to vaporization. In order to solve the mass-energy balance at the vapour bubble interface, a spherical surface area is commonly assumed. This leads to the need for correction factors and provides little insight into the physical mechanism responsible for bubble shape. In this study, the transitioning shape of a vapour bubble is considered in the integral analysis of the interfacial mass-energy balance. The model predicts the following bubble growth characteristics: profile, volume, centre of gravity, and aspect ratio.</p> / Doctor of Philosophy (PhD)

<p>With the rising prices of energy and the harmful environmental effects many of conventional energy generation techniques the world is pushing for new, cleaner, more efficient and more environmental renewable energy sources. Thermoelectric generators are one of the potential solutions to these problems of unclean and expensive energy. Thermoelectric generators are solid state devices that convert thermal energy into useful electrical energy.</p> <p>Over the last ten years the progress in materials science have led to advancements in thermoelectrics. However as of yet no standardised method of testing thermoelectric generators has been established and as such data provided for thermoelectric generators is regarded as questionable. This thesis deals with two commercial thermoelectric generator models, TEG1 12610-5.1 AND TEG1B 12610-5.1, and quantifies the deviation of the manufacturer’s specifications to what is experimentally achieved by the generators as 147% and 22% respectively. The variance of the outputs between thermoelectric generators was measured by comparing the maximum power output for the models in question over a sample size of four, it was found to be as much as 20% and 8% respectively.</p> <p>A full characterisation of the thermoelectric generators is performed on the two generator models to obtain the data as to their power output and thermal conductivity for the purpose of design of a waste energy harvesting device. The full characterisation was also used to validate the testing apparatus as a device capable for the use as a standardised method of characterising the performance of thermoelectric generation modules.</p> <p>A mechanistic model is created using the experimental characterisation data. This mechanistic model has the ability to accurately predict the voltage and current output of the thermoelectric generator models under any given temperatures and electrical loading condition with a minimum R-squared value of 0.94. The thermal conductivity is also found to be predictable using an established equation modified with an empirical constant.</p> / Master of Applied Science (MASc)

There has been an increased interest in renewable energy systems in recent years as a result of concerns on depleting fossil fuel reserves and climate change. Wind and solar energy are amongst the most popular renewable energy technologies. In order to use the full or maximum possible extent of a renewable energy resource in a region, hybrid systems extracting wind and solar energy simultaneously are a popular and obvious choice. It is desired to design hybrid systems that enhance the renewable energy output without increasing the foot print area compared to the base case of only wind or only solar energy. One potential way forward is to consider a vertical axis wind turbine with an enhanced surface area which can be used for mounting solar cells. This way the foot print area remains the same while both wind and solar power are obtained simultaneously. Renewable Energy Solutions LLC has manufactured a novel 2 m high and 2 m in diameter vertical axis wind turbine called Marilyn which has an enhanced surface area, which can be used for the aforementioned purpose. This thesis focuses on the development of a hybrid solar-wind turbine design based on the Marilyn system. Firstly, the wind and solar resource was assessed at Austin, TX using weather monitoring instruments. Typical Meteorological Year 3 (TMY3) data was also used in conjunction with the measured data to estimate the wind and solar resource at Austin, TX. Secondly, the wind turbine performance was assessed based on whether is it able to achieve grid tie in for wind power production starting at wind speeds of 3-4 m/s. It was found that replacing the current generator with different model featuring higher voltage output at lower rotational speeds could help achieve this. Based on this suggested replacement and using the wind resource data, the yearly wind energy production was estimated to be 240 kWh. Finally, a theoretical analysis was performed for estimating the yearly solar energy production. A base case analysis was first made on power production on a particular day of the year if only the top portion of every alternate face of the turbine is covered with flexible 3.4 % efficient solar cells. This analysis is subsequently extended to the case when flexible 20 % efficient solar cells cover the entire top surface of the turbine and the corresponding conservative yearly solar energy output was estimated to be 310 kWh. Thus the total yearly energy output from the Marilyn hybrid system is 550 kWh, which is around 5 % of the annual electricity usage of a typical American home / text

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.

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.