| 1. |
- Diller, Katharina, et al.
(författare)
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Polyphenylsilole multilayers - an insight from X-ray electron spectroscopy and density functional theory
- 2015
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 17:46, s. 31117-31124
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Tidskriftsartikel (refereegranskat)abstract
- We present a combined investigation by means of X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy of condensed multilayers of two polyphenylsiloles, namely hexaphenylsilole (HPS) and tetraphenylsilole (TPS). Both compounds exhibit very similar spectroscopic signatures, whose interpretation is aided by density functional theory (DFT) calculations. High-resolution XPS spectra of the Si 2p and C 1s core levels of these multilayers indicate a positively charged silicon ion flanked by two negatively charged adjacent carbon atoms in the silole core of both molecules. This result is corroborated quantitatively by DFT calculations on isolated HPS (TPS) molecules, which show a natural bond orbital partial charge of + 1.67 e (+1.58 e) on the silicon and -0.34 e (-0.58 e) on the two neighbouring carbon atoms in the silole ring. These charges are conserved in direct contact with a Cu(111) substrate for films of submonolayer coverage, as evidenced by the Si 2p XPS data. The C K-edge NEXAFS spectra of HPS and TPS multilayers exhibit distinct and differing features. Their main characteristics reappear in the simulated spectra and are assigned to the different inequivalent carbon species in the molecule. The angle-dependent measurements hardly reveal any dichroism, i.e., the molecular p-systems are not uniformly oriented parallel or perpendicular with respect to the surface. Changes in the growth conditions of TPS, i.e., a reduction of the substrate temperature from 240 K to 80 K during deposition, lead to a broadening of both XPS and NEXAFS signatures, as well as an upward shift of the Si 2p and C 1s binding energies, indicative of a less ordered growth mode at low temperature.
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| 2. |
- Li, Nian, et al.
(författare)
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Morphology Phase Diagram of Slot-Die Printed TiO2 Films Based on Sol-Gel Synthesis
- 2019
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Ingår i: Advanced Materials Interfaces. - : WILEY. - 2196-7350. ; 6:12
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Tidskriftsartikel (refereegranskat)abstract
- Mesoporous titania films with tailored nanostructures are fabricated via slot-die printing, which is a simple and cost-effective thin-film deposition technique with the possibility of a large-scale manufacturing. Based on this technique, which is favorable in industry, TiO2 films possess the similar advantage with polymer semiconducting devices like ease of large-scale production. The titania morphologies, including foam-like nanostructures, nanowire aggregates, collapsed vesicles and nanogranules, are achieved via a so-called block-copolymer-assisted sol-gel synthesis. By adjusting the weight fraction of reactants, the ternary morphology phase diagram of the printed titania films is probed after template removal. The surface and inner morphology evolutions are explored with scanning electron microscopy and grazing incidence small-angle X-ray scattering, respectively. Special focus is set on foam-like titania nanostructures as they are of especial interest for, e.g., solar cell applications. At a low weight fraction of the titania precursor titanium(IV)isopropoxide (TTIP), foam-like titania films are achieved, which exhibit a high uniformity and possess large pore sizes. The anatase phase of the highly crystalline titania films is verified with X-ray diffraction and transmission electron microscopy.
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| 3. |
- Liu, S., et al.
(författare)
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Performance analysis of two-stage compression transcritical CO2 refrigeration system with R290 mechanical subcooling unit
- 2019
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Ingår i: Energy. - : Elsevier Ltd. - 0360-5442 .- 1873-6785. ; 189
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Tidskriftsartikel (refereegranskat)abstract
- The use of carbon dioxide (CO2) as refrigerant is driven by the need to phase down the traditional synthetic refrigerant so as to mitigate the warming climate. In this study, the thermal performance of a two-stage compression transcritical CO2 refrigeration system with R290 mechanical subcooling unit is conducted. The goal is to obtain the maximum coefficient of performance (COP) of five different mechanical subcooling systems under the optimal subcooling temperature and compressor discharge pressure. The two-throttling and two-stage compression high-pressure mechanical subcooling system is found to have a higher COP. When the evaporation temperature is −30 °C, the COP of the two-throttling and two-stage compression high-pressure mechanical subcooling system is improved by 76.74%. The COP of the two-throttling and two-stage compression high-pressure mechanical subcooling system is 1.52 at an ambient temperature of 40 °C, which is 21.87% higher than that of the two-throttling and two-stage compression low-pressure mechanical subcooling system. The power consumption ratio of one-throttling and two-stage compression low-pressure mechanical subcooling system is significantly higher than that of other systems. From a comprehensive analysis of the proposed four systems, the two-throttling and two-stage compression high-pressure mechanical subcooling system has the best performance over all other systems.
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| 4. |
- Nian, V., et al.
(författare)
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A Comparative Cost Assessment of Energy Production from Central Heating Plant or Combined Heat and Power Plant
- 2016
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; , s. 556-561
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Konferensbidrag (refereegranskat)abstract
- The levelized cost of electricity (LCOE) is a common approach in evaluating the economic competitiveness of a power generation technology. The same approach can be applied for evaluating the levelized cost of heat (LCOH) production. There are a number of approaches in calculating the LCOE and or LCOH from a combined heat and power (CHP) plant. In this study, we explore three alternative methods in calculating the LCOE and LCOH of a CHP and compare the results with that those of a heating only plant. The results can be used as indicators for identifying a suitable pricing mechanisms for the heating market.
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| 5. |
- Nian, V., et al.
(författare)
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A feasibility study on integrating large-scale battery energy storage systems with combined cycle power generation – Setting the bottom line
- 2019
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Ingår i: Energy. - : Elsevier Ltd. - 0360-5442 .- 1873-6785. ; 185, s. 396-408
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Tidskriftsartikel (refereegranskat)abstract
- Strong attention has been given to the costs and benefits of integrating battery energy storage systems (BESS) with intermittent renewable energy systems. What's neglected is the feasibility of integrating BESS into the existing fossil-dominated power generation system to achieve economic and environmental objectives. In response, a life cycle cost-benefit analysis method is introduced in this study taking into consideration three types of battery technologies, namely, vanadium redox flow battery, zinc bromine flow battery, and lithium-iron-phosphate battery. The objective is to evaluate the life cycle carbon emissions and cost of electricity production by combined cycle power generation with grid-connected BESS. Findings from the Singapore case study suggest a potential 3–5% reduction in the life cycle carbon emission factors which could translate to a cumulative carbon emission reduction of 9–16 million tonnes from 2018 to 2030 from electricity generation. Grid-connected BESS could reduce the levelized cost of electricity by 4–7%. A synergistic planning of CCGT and BESS could theoretically reduce the system level power generation capacity by 26% albeit a potential increase in the overall capital cost at the current cost of batteries. The projected battery cost reduction is critical in improving the feasibility of large-scale deployment.
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| 6. |
- Wang, Y., et al.
(författare)
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Life cycle analysis of integrated gasification combined cycle power generation in the context of Southeast Asia
- 2018
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 11:6
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Tidskriftsartikel (refereegranskat)abstract
- Coal remains a major source of electricity production even under the current state of developments in climate policies due to national energy priorities. Coal remains the most attractive option, especially to the developing economies in Southeast Asia, due to its abundance and affordability in the region, despite the heavily polluting nature of this energy source. Gasification of coal running on an integration gasification combined cycle (IGCC) power generation with carbon capture and storage (CCS) represents an option to reduce the environmental impacts of power generation from coal, but the decarbonization potential and suitability of IGCC in the context of Southeast Asia remain unclear. Using Singapore as an example, this paper presents a study on the life cycle analysis (LCA) of IGCC power generation with and without CCS based on a generic process-driven analysis method. We further evaluate the suitability of IGCC with and without CCS as an option to address the energy and climate objectives for the developing economies in Southeast Asia. Findings suggest that the current IGCC technology is a much less attractive option in the context of Southeast Asia when compared to other available power generation technologies, such as solar photovoltaic systems, coal with CCS, and potentially nuclear power technologies.
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| 7. |
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