• Energy Research

The dataset contains raw data and experimental results of thermodynamic properties of different compositions of KCl-CuCl molten salt. Thermal stability, melting point and hydrolysis rate of compositions are studied experimentally.

Abstract Carbon Capture in Molten Salts (CCMS) is a high temperature method for extracting CO 2 from a variety of flue gases related to power generation and carbon-intensive industries. The chemical principles are similar to those in calcium looping in the solid state; a carbonation reaction of CaO with CO 2 to form CaCO 3 followed by regeneration of CO 2 through the reverse reaction. In CCMS, the active substances (CaO/CaCO 3 ) are dissolved or partly dissolved in molten salts, allowing fast reaction kinetics, high CO 2 sorption capacities, and avoiding solids attrition issues. In our previous studies, the focus has been on the total CO 2 sorption capacity and demonstration of cyclic absorption and desorption. Experiments have been performed with up to 20 wt% CaO in molten CaCl 2 and eutectic CaF 2 /CaCl 2 . It has been demonstrated that up to 85% of the CaO reacts during absorption, and ∼100% of the CaCO 3 is decomposed during desorption. No degradation of the sorbent has been observed after 12 cycles. In the present study, the focus is turned to the reaction kinetics between CO 2 and CaO. The raw data from previous experiments are analyzed to obtain the sorption capacity (g CO 2 / 100 g sorbent) as a function of time, and the linear region of the capacity is further used to evaluate the reaction kinetics. The effect of absorption temperature, molten salt composition, CaO content and cyclic CO 2 capture is studied. The results show that CaF 2 /CaCl 2 is more favorable for CCMS than pure CaCl 2 ; the kinetically controlled regime lasts longer and the total sorption capacity is higher. For both of the salt mixtures, the sorption capacities are stable during cyclic CO 2 capture, without any deterioration of the reaction kinetics.

Correlations between defect-related luminescence (DRL) and recombination mechanisms of multicrystalline silicon wafers are investigated by hyperspectral photoluminescence (PL) imaging at cryogenic temperatures (∼80 K) and by PL-based techniques for charge carrier lifetime at room temperature. This unique combination of measurement techniques is used to spectrally compare the DRL in n-type and p-type wafers and to investigate the DRL as a function of block height in a p-type block. Further, the dependence of DRL on interstitial and precipitated metallic impurities has been investigated by comparison of simulated concentration profiles of interstitial and precipitated iron with the spatial distribution of DRL. Our results indicate that the origins of the dislocation-related emission lines (D-lines) are independent of the doping type and suggest that the spectral shape, rather, is determined by the dominating recombination mechanism in the material. In regions with high structural defect density, we observe increased intensities of the D-lines D1–D4 in the DRL spectrum. In regions with a high concentration of either iron or other metallic precipitates, we observe reduced emission intensities of D3 and D4. It is, thus, likely that precipitates of either iron or other impurities partly supress the D3 and D4 emission intensities.

The present work is a demonstration of how near infrared (NIR) hyperspectral photoluminescence imaging can be used to detect defects in silicon wafers and solar cells. Chemometric analysis techniques such as multivariate curve resolution (MCR) and partial least squares discriminant analysis (PLS-DA) allow various types of defects to be classified and cascades of radiative defects in the samples to be extracted. It is also demonstrated how utilising a macro lens yields a spatial resolution of 30 µm on selected regions of the samples, revealing that some types of defect signals originate in grain boundaries of the silicon crystal, whereas other signals show up as singular spots. Combined with independent investigation techniques, hyperspectral imaging is a promising tool for determining origins of defects in silicon samples for photovoltaic applications.

AbstractCapture and storage of fossil carbon emitted to the atmosphere from anthropogenic sources has been identified as a key technology for keeping human‐induced global warming below 2°C. Available technologies have not achieved widespread impact due to costs related to increased energy consumption and expensive, large process equipment. Here, we show how molten inorganic halide salt‐based mixtures containing CaO may be utilized for selective capture and subsequent controlled release of carbon dioxide from diluted flue gases. Highly efficient absorption is demonstrated in a fluoride‐based liquid, absorbing close to 100% of the CO2 from a simulated flue gas with an absorbing column height of only 10 cm. Greater than 90% carbonation with >80% regeneration to CaO was recorded. Excellent cyclability has been achieved with a chloride‐based liquid with 60% carbonation and 100% regeneration to CaO during four cycles. The high efficiencies may enable extraction of CO2 from highly diluted gas mixtures.

CO2 capture by CaO in molten salts is a variant of calcium looping in which the active substances (CaO/CaCO3) are dissolved or in a slurry with inorganic molten salts. One of the main advantages is the nonexistence of degradation in the reactivity between the active material and CO2. Previous research has revealed good absorption and desorption characteristics with CaO contents up to 20 wt% in eutectic CaF2-CaCl2. The hypothesis is that the formed CaCO3 continuously dissolves in the melt, leaving highly reactive CaO readily available for the incoming CO2. In the present study, the CaO content is increased to 40 wt%, and the absorption characteristics is investigated with focus on the sorption capacity and CO2 removal rate. The chemical system is also evaluated experimentally with regards to viscosity and solubility of the formed CaCO3 during CO2 absorption, with the aim of determining chemical upscaling limitations. The results show that the practical CaO content limit is 30 wt%, in which a sorption capacity of 20 g CO2/100 g sorbent is observed, without any deterioration of the reaction kinetics. For 40 wt% CaO, the sorption capacity is higher, but on the expense of the CO2 removal rate and CaO conversion. This is attributed to a significant increase in viscosity and the solubility limit of CaCO3 being exceeded.

AbstractThe characteristics of CO2 reacting with CaO in a molten eutectic mixture of CaF2 and NaF has been investigated. Calculations of the Gibbs free energy, temperature analysis of the decomposition of the formed carbonates, and XRD analyses of quenched samples taken during CO2 absorption or desorption were employed to identify the phases present in the melt. Efficient CO2 absorption from a simulated flue gas was observed, due to a combined reaction where CaO initially reacts with CO2 and forms CaCO3. Subsequently, Na2CO3 is formed by an ion exchange reaction between CaCO3 and NaF. It was found that the CaO activity is highest in the temperature range 826–834°C. Increasing the CaO concentration from 5 to 20 wt% in the molten salt resulted in reduced CO2 reactivity efficiency, probably because of precipitation and agglomeration of the sorbent. The total carbonation conversion was independent of the CO2 concentration in the inlet gas, and the sorbent carrying capacity was in the range 0.722–0.743 g CO2/g CaO corresponding to 0.037–0.144 g CO2/g total liquid. Decarbonation was conducted by raising the temperature. 40% conversion back to CaO was recorded at 1160°C. The recorded curves for the CO2 concentration in the outlet gas exhibited a rapid desorption step followed by a slow step.

Abstract Oxygen-related Thermal Donors in n-type Czochralski silicon (Cz-Si) wafers have been investigated using hyperspectral photoluminescence imaging and OxyMap. Thermal Donors give rise to two photoluminescence emissions, one narrow peak at 0.767 eV, and one broad band with centre peak at 0.72 eV that is also measurable at room temperature. The spectral imaging was first carried out on the sample cooled to 90 K, then repeated at room temperature (300 K). The possibility to delimitate at room temperature defects-rich zones with hyperspectral photoluminescence imaging is evidenced.