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The photovoltaic industry attracts a lot of interest from researchers worldwide due to active integration of the solar cells. The main idea here is to convert solar energy into electricity. One type of solar cell that shows potential in replacing today’s crystalline silicon cells is the thin film solar cell (TFSC). Yet, the sun absorbing semiconductors used in the commercial TFSCs contain scarce elements such as indium, cadmium and tellurium, which may cause problems if the technique is going to grow to a big scale energy producer. Earth abundant sun absorbing materials are therefore of great interest, and several possible replacements are under investigation. In this project two olivine structured ternary metal chalcogenides were investigated: manganese silicon sulfide (Mn2SiS4) and iron silicon sulfide (Fe2SiS4). The goal was to deposit thin films by reactive magnetron sputtering from manganese/iron and silicon targets with mixture of Ar and H2S gas. Afterwards the films were crystallized by a sulfurization process at high temperature. The samples were created with a composition gradient and investigated by SEM, EDS and XRD. Results showed that a single phase of Mn2SiS4 was successfully created in thin film form for the first time. Multiple attempts on manufacturing Fe2SiS4 were performed, but didn't show sufficient progress yet. The analysis showed formation of pyrite (FeS2), pyrrhotite (Fe1-xS, x<0.2) and SiS2 phases instead of the targeted material. In both cases it is important to provide additional studies to determine if the selected compounds could be used as an absorber layer in TFSC structures.

Hydroelectricity has for a long time been considered climate neutral due to it being a renewable source of energy. During the last years however, studies have shown that emission magnitudes from hydroelectric reservoirs may be equal to those of fossil fuel power plants. Reservoir emissions are largest in tropical regions, where CO2 diffusion and CH4 ebullition are main contributors to the overall emission rate. It is also in tropical regions where extraction of hydroelectricity is expected to experience a sharp rise in coming years. In a study published 2011 it was hypothesised that previous estimates have completely missed ebullition hotspots in reservoirs, and thereby underestimated CH4 emission by at least one order of magnitude. Spatial variability of CH4 ebullition rates has been estimated for two tropical reservoirs: nutrient-poor Chapéau d’Uvas Reservoir (CDU) and nutrient-rich Funil Reservoir (FUN). Spatial variability of diffusion and the total emission rate has furthermore been estimated for CDU. Additionally, two methods used for measuring gas transfer rates (a parameter important for explaining diffusion) have been compared. The obtained estimate in total emission rate was 3,094 mg CO2-eq m-2 day-1, which amounts to half of the average in the most recent global assessment for tropical reservoirs. The estimation of ebullition emission in FUN was 4,000 times lower than in CDU, likely due to a higher rate of increase in hydrostatic pressure during sampling in FUN. Similarities identified between CH4 ebullition, CO2 diffusion and CO2 concentration were: generally higher rates in bays and in the main inflow than in the main reservoir area. No statistically significant differences in spatial variability of ebullition between inflow areas and non-inflow areas were identified. The method-comparison for gas transfer rate measurements indicated that the discrepancy between the methods increased with higher average values measured. Vattenkraft har sedan länge ansetts vara klimatneutral eftersom den är en förnyelsebar energikälla. De senaste åren har dock studier visat att utsläppsnivåer från vattenkraft-verkens magasin kan vara i samma storleksordning som de från kolkraftverk. Utsläpp från vattenmagasin är högst i tropikerna, där diffusion av koldioxid (CO2) samt uppbubbling av metan (CH4) bidrar stort till det totala utsläppet. Det är även i tropiska regioner som vattenkraftutvinning förväntas öka som mest de kommande åren. I en studie publicerad 2011 antogs det att tidigare uppskattningar helt och hållet missat ”hotspots” av upp-bubbling i vattenmagasin, och därmed underskattat utsläpp av CH4 med åtminstone en storleksordning. Rumslig variation av uppbubbling har uppskattats för två tropiska vattenmagasin: näringsfattiga Chapéau d’Uvas Reservoir (CDU) och näringsrika Funil Reservoir (FUN). I CDU har även uppskattningar för den rumsliga variationen av diffusion och det totala utsläppet från magasinet inkluderats. Därutöver har två metoder som används för att mäta gasöverföringshastighet (en parameter som förklarar stor del av diffusionen) jämförts där. Den totala utsläppsnivån uppmättes till 3 094 mg CO2-ekv m-2 dag-1, vilket uppgår till häften av uppskattade nivåer för tropiska vattenmagasin i den senaste globala under-sökningen. Estimering av utsläpp från uppbubbling i FUN var 4 000 gånger lägre än i CDU, vilket troligtvis beror på ett kraftigare tilltagande hydrostatiskt tryck under provtagning i FUN. Likheter som identifierades mellan uppbubbling av CH4, diffusion av CO2 och koncentration av CO2 var: Generellt högre värden i vikar och i huvudinflödet än i huvudfåran av vattenmagasinet. Inga statistiskt relevanta rumsliga skillnader kunde identifieras. Metod-jämförelsen för mätningar av gasöverföringshastighet antydde en ökad avvikelse mellan metoderna för högre uppmätta värden.