• Energy Research
• Closed Access close
• Embargo close
• SE close
• AE close
• CA close
• CN close
• English close

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.

Original data for the study: Lí, et al. Subarctic winter-warming promotes soil microbial resilience to freeze-thaw cycles and enhances the microbial carbon-use efficiency. This dataset mainly contains the data showing the legacy effect of field winter warming on the dynamic response of soil microbial growth, respiration, and C-use efficiency during an imposed freezing-thawing perturbation. Six sheets are included in an Excel file named "Open data for WinterWarmingFTW.xlsx" as follows: Figure1. Field temp & moist Table1. Soil variables & PLFAs Figure2. PCA of PLFAs Figure3. Bac & Fung grwoth Figure4. Resp Figure5. FB & CUE

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.

To date, the majority of world's primary energy is derived from fossil fuels. However, the fossil fuel recourses are in an inevitable decline as energy demand continues to grow exponentially with population growth, urbanization, and improved standards of living. Crude oil prices have recently risen several times and their current annual volatility exceeds 30%. The potential scarcity of fossil fuels has prompted a global search for alternative energy resources. Biodiesel fulfills the major requirements for production of alternative fuels such as feedstock availability, technical feasibility, and economic competitiveness. Together with other renewable biofuels, the use of biodiesel as a substitute of fossil-based fuels is expected to reduce the dependence on imported petroleum and associated political and economic vulnerability, decrease greenhouse gas emissions, and revitalize the economy. The objective of this article was to provide an update of the most recent technological advancements toward clean and sustainable biodiesel production through a thorough overview of biodiesel feedstocks, most promising transesterification processes, and opportunities for glycerol utilization for value-added products. A critical analysis of the techno-economical barriers and environmental challenges that need to be addressed in future R&D efforts toward commercialization and establishment of a sustainable and cost-efficient biodiesel production is provided. Keywords: biodiesel; waste oil; microbial oil; transesterification; microwave irradiation; lipase; glycerol; triacetin; greenhouse gas emissions; trends in biodiesel R&D

In this letter we report the preliminary validation of a low-cost paradigm for photovoltaic power generation that utilizes a prismatic Fresnel-like lens to simultaneously concentrate and separate sunlight into continuous laterally spaced spectral bands, which are then fed into spectrally matched single-junction photovoltaic cells. A prismatic lens was designed using geometric optics and the dispersive properties of the employed material, and its performance was simulated with a raytracing software. After device optimization, it was fabricated by injection molding, suitable for large-scale mass production. We report an average optical transmittance of ~ 90% over the VNIR range with spectral separation in excellent agreement with our simulations. Finally, two prototype systems were tested: one with GaAsP and c-Si photovoltaic devices and one with a pair of copper indium gallium selenide based solar cells. The systems demonstrated an increase in peak electrical power output of 51% and 64% respectively under white light illumination. Given the ease of manufacturability of the proposed device, the reported spectral splitting approach provides a costeffective alternative to multi-junction solar cells for efficient light-to-electricity conversion ready for mass production.