| 1. |
- Pecunia, Vincenzo, et al.
(författare)
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Roadmap on energy harvesting materials
- 2023
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Ingår i: Journal of Physics. - : IOP Publishing. - 2515-7639. ; 6:4
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Tidskriftsartikel (refereegranskat)abstract
- Ambient energy harvesting has great potential to contribute to sustainable development and address growing environmental challenges. Converting waste energy from energy-intensive processes and systems (e.g. combustion engines and furnaces) is crucial to reducing their environmental impact and achieving net-zero emissions. Compact energy harvesters will also be key to powering the exponentially growing smart devices ecosystem that is part of the Internet of Things, thus enabling futuristic applications that can improve our quality of life (e.g. smart homes, smart cities, smart manufacturing, and smart healthcare). To achieve these goals, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. By bringing together the perspectives of experts in various types of energy harvesting materials, this Roadmap provides extensive insights into recent advances and present challenges in the field. Additionally, the Roadmap analyses the key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, the Roadmap outlines promising directions for future research to fully harness the potential of energy harvesting materials for green energy anytime, anywhere.
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| 2. |
- Allgurén, Thomas, 1986, et al.
(författare)
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The Influence of Alkali, Chlorine and Sulfur on Aerosol Formation
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The use of low-quality fuels in power generation is typically motivated by a potential reduction in fuel costs or CO2 emissions, the latter in case the fuel is based on biomass. These features make low quality fuels attractive at the same time as such fuels are usually problematic to use in power generation due to fuel composition. One of the main issues is deposition of aerosols upon heating surfaces reducing heat transfer and causing high-temperature corrosion (HTC). The later most often related to alkali chlorides, and these are formed from alkali species and chlorine when released during the combustion process. The present work aims to investigate how the gas phase chemistry are connected to the formation aerosols and their characteristics. This is an ongoing work why only part of the preliminary results is presented focusing on the interaction between alkali, sulfur and chlorine in the gas phase. The results presented here indicate a clear correlation between the S/Cl ratio and the formation of alkali sulfates over chlorides. It is also indicated that the local conditions at which the species are released and available in the gas phase is important for the resulting formation of alkali sulfates.
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| 3. |
- Arendt, Richard G., et al.
(författare)
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JWST NIRCam Observations of SN 1987A : Spitzer Comparison and Spectral Decomposition
- 2023
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 959:2
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Tidskriftsartikel (refereegranskat)abstract
- JWST Near Infrared Camera (NIRCam) observations at 1.5–4.5 μm have provided broadband and narrowband imaging of the evolving remnant of SN 1987A with unparalleled sensitivity and spatial resolution. Comparing with previous marginally spatially resolved Spitzer Infrared Array Camera (IRAC) observations from 2004 to 2019 confirms that the emission arises from the circumstellar equatorial ring (ER), and the current brightness at 3.6 and 4.5 μm was accurately predicted by extrapolation of the declining brightness tracked by IRAC. Despite the regular light curve, the NIRCam observations clearly reveal that much of this emission is from a newly developing outer portion of the ER. Spots in the outer ER tend to lie at position angles in between the well-known ER hotspots. We show that the bulk of the emission in the field can be represented by five standard spectral energy distributions, each with a distinct origin and spatial distribution. This spectral decomposition provides a powerful technique for distinguishing overlapping emission from the circumstellar medium and the supernova ejecta, excited by the forward and reverse shocks, respectively.
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| 4. |
- Bäckström, Daniel, 1985, et al.
(författare)
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Measurement of the size distribution, volume fraction and optical properties of soot in an 80 kW propane flame
- 2017
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Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180 .- 1556-2921. ; 186, s. 325-334
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Tidskriftsartikel (refereegranskat)abstract
- This work presents measurements of the size distribution, volume fraction, absorption and scattering coefficients of soot in an 80 kW swirling propane-fired flame. Extractive measurements were performed in the flame using an oil-cooled particle extraction probe. The particle size distribution was measured with a Scanning Mobility Particle Sizer (SMPS) and the optical properties were measured using a Photo Acoustic Soot Spectrometer (PASS-3). A detailed radiation model was used to examine the influence of the soot volume fraction on the particle radiation intensity. The properties of the gas were calculated with a statistical narrow-band model and the particle properties were calculated using Rayleigh theory with four different complex indices of refraction for soot particles. The modelled radiation was compared with measured total radiative intensity, the latter which was measured with a narrow angle radiometer. The results show that the measured soot volume fraction yields particle radiation that corresponds well with the determined difference between gas and total radiation. This indicates that the presented methodology is capable of quantifying both the particle and gaseous radiation in a flame of technical size. (C) 2017 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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| 5. |
- Bäckström, Daniel, 1985, et al.
(författare)
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Particle composition and size distribution in coal flames - The influence on radiative heat transfer
- 2015
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Ingår i: Experimental Thermal and Fluid Science. - : Elsevier BV. - 0894-1777 .- 1879-2286. ; 64, s. 70-80
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Tidskriftsartikel (refereegranskat)abstract
- Radiative heat transfer in a 77 kWth swirling lignite flame has been studied. The aim is to characterize different particle types present in a coal flame and to determine their influence on the radiative heat transfer. The study combines extractive particle measurements, radiative intensity measurements and detailed radiation modelling. The size distribution of the extracted particles was measured with a low pressure impactor and some of the size fractions were analysed with SEM–EDX. The measured total radiative intensity is compared with the modelled intensity based on the particle measurements in the same cross-section of the flame. The particle properties were calculated with Mie theory and the gas properties with a statistical narrow-band model. The results show that the contribution of coal/char particles dominates the radiative heat transfer in the investigated cross-section of the flame. The methodology applied in this work shows promising results for characterization of particle radiation in flames of practical size.
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| 6. |
- Draper, Teri, et al.
(författare)
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A comparison of industrial-scale (471 MWe) radiometer heat flux measurements between pulverized-coal and 85% coal/15% biomass co-firing combustion
- 2021
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work evaluates and compares radiative heat transfer measurements conducted at the 471 MWe Hunter Powerplant Unit 3 utility boiler in Utah, USA, during commercial operation with coal and during tests with co-firing of coal and biomass. The coal used was a Utah sourced bituminous coal, which was mixed with 15 wt% of torrefied wood in the co-firing test. The measurements were gathered using two different narrow angle radiometers and one ellipsoidal radiometer to measure the radiative heat flux. Data were gathered at several floors through port openings in the boiler wall and the samplings were spread out over several hours. Additionally, the gas temperature was measured at positions close to the inner walls of the different floors. Overall, the measured heat fluxes decreased with increasing boiler floor level, and while the measurement data spread is rather high for each measurement, the data spreads for both fuel conditions significantly overlap each other, indicating that it is likely the heat flux profile remains unchanged when running either type of fuel.
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| 7. |
- Gall, Dan, et al.
(författare)
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A new technique for real-time measurements of potassium and sodium aerosols based on field-reversal surface ionization
- 2021
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Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 32:7
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Tidskriftsartikel (refereegranskat)abstract
- A new method for real-time measurements of potassium and sodium containing aerosol particles is described and verified. The method is based on surface ionization technique and may be used to explore the alkali chemistry related to high temperature chemistry processes. The measurement device is a further development of the simple and cost-effective surface ionization detector previously used for online alkali measurements in combustion and gasification research. The discrimination between sodium and potassium is possible due to differences in their surface desorption kinetics and facilitated by rapidly reversing the field potential between the ion source and the nearby collector. The instrument is evaluated in a series of laboratory experiments using size-selected alkali salt particles containing KCl, NaCl, K2SO4, Na2SO4, KNO3 and NaNO3. The filament temperature was found to be a key influencing factor in order to optimize the strength and Na-K deviation of the observed ion current. The ability to simultaneously report absolute concentrations of Na and K makes the instrument attractive for solid fuel conversion of alkali-rich fuels such as low-grade biomass and to explore behavior deviations of Na and K in high temperature processes. © 2021 The Author(s). Published by IOP Publishing Ltd.
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| 8. |
- Gall, Dan
(författare)
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Alkali Metals and Tar in Biomass Thermochemical Conversion: Development and Application of Online Measurement Techniques
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biomass is a renewable resource that can substitute the fossil-based products we depend on today. However, the conversion techniques require further improvement in order to be competitive with the traditional industry. One of the limitations is associated with the absence of measurement methods with sufficient time resolution that can be used to characterize the complex systems and optimize process conditions. This thesis presents the development and application of novel measurement methods, capable of time-resolved characterization of tar and alkali metals, which are key components in biomass gasification. The measurement methods are mainly adapted from aerosol science and based on thermal analysis and surface ionization of aerosol particles. Long-term measurements are achieved by dilution and conditioning of hot product gas, which allow condensable components to form aerosol particles that are subsequently analyzed. The developed methods are used to determine alkali, tar and particle concentrations in industrial scale facilities for biomass gasification. The aerosol characterization methods are also applied in flame chemistry and radiation research. Studies performed in dual-fluidized bed (DFB) gasification systems indicate that the alkali metal content of biomass to a large extent is emitted during the gasification process, and observed concentrations are close to the levels predicted by equilibrium calculations. The high alkali concentrations have implications for catalytic processes in the fluidized beds and for downstream processes including corrosion, fouling, and upgrading to commercial products. The developed methods are employed to characterize the transient conditions when changes in operational parameters and additives are used to optimize the gasification process. A significant increase of the alkali metal concentration was observed when alkali salts were inserted directly to a gasifier, which suggests a fast volatilization in the reducing environment. Additives to the combustion side of the DFB imposed notable effects in the product gas, and the results provide information regarding the transfer mechanisms of inorganic compounds in the system. Additions of olivine and ilmenite reduced the gas-phase alkali metal concentration, indicating a fast reaction between alkali metal compounds and the minerals. The applied changes also affected the formation of condensable tar, and the tar concentration was found to anti-correlate with the alkali metal concentration when a sand bed was used, while no clear trend was observed with an olivine bed. The studies confirm that several options are available to improve the alkali metal and tar behavior in biomass gasification, and suggest that online monitoring is needed to study and optimize the underlying processes.
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| 9. |
- Gall, Dan, 1981, et al.
(författare)
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Alkali Monitoring of Industrial Process Gas by Surface Ionization─Calibration, Assessment, and Comparison to in Situ Laser Diagnostics
- 2021
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 35:24, s. 20160-20171
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we present rigorous calibration and assessment of a surface ionization detector (SID) for alkali monitoring in industrial process gases and compare it to an in situ laser diagnostic method called collinear photofragmentation and atomic absorption spectroscopy (CPFAAS). The side-by-side comparison of the time-resolved alkali concentration was performed in a technical-scale gas burner seeded with selected alkali salts, corresponding to alkali molar fractions of 10-100 ppm in the flue gas. The SID operates at room temperature and relies on extraction, dilution, and conditioning of the sample gas, whereas CPFAAS provides in situ molecular data. During KCl addition, the instruments were in good agreement: 80.1 ppm (SID) and 88.5 ppm (CPFAAS). In addition to the field measurements, internal validation of SID performance parameters (flow, electric field strength, and filament temperature) and external parameters (particle size and salt composition) was performed. The difference in sensitivity toward different alkali salts was found to be considerable, which limits the quantitative assessment for a sample gas of unknown composition. The results demonstrate the capability and limitations of the SID and show that a SID can satisfactory monitor KCl levels in a process gas over several days of continuous measurements. However, for heterogeneous fuels with deficient characterization of the gas composition, the obtained SID signal is difficult to interpret without supportive diagnostics. The generic ability of the SID to detect Na and K in both gas and particle phases makes it a valuable complement to alkali diagnostics, such as spectroscopic techniques.
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| 10. |
- Gall, Dan, et al.
(författare)
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Online Measurements of Alkali and Heavy Tar Components in Biomass Gasification
- 2017
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 31:8, s. 8152-8161
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Tidskriftsartikel (refereegranskat)abstract
- Tar and alkali metal compounds are released during biomass gasification and have a major impact on the operation and performance of gasification processes. Herein we describe a novel method for characterization of alkali and heavy tar compounds in the hot product gas formed during gasification. Gas is continuously extracted, cooled and diluted, which results in condensation of tar and alkali into aerosol particles. The thermal stability of these particles is subsequently evaluated using a volatility tandem differential mobility analyzer (VTDMA) method. The technique is adopted from aerosol science where it is frequently used to characterize the thermal properties of aerosol particles. Laboratory studies show that pure and mixed alkali salts and organic compounds evaporate in well-defined temperature ranges, which can be used to determine the chemical composition of particles. The performance of the VTDMA is demonstrated at a 4 MWth dual fluidized bed gasifier using two different types of online sampling systems. Alkali metal compounds and a wide distribution of heavy tar components with boiling points above 400°C are observed in the product gas. Implications and potential further improvements of the technique are discussed.
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