| 1. |
- Nagaraja, Ch., et al.
(författare)
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Opening remarks
- 2016
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Konferensbidrag (refereegranskat)
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| 2. |
- Cornelissen, Johannes H C, et al.
(författare)
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Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes
- 2007
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 10:7, s. 619-627
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Tidskriftsartikel (refereegranskat)abstract
- Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide.Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.
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| 3. |
- Zhao, R., et al.
(författare)
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Thermodynamic research of adsorbent materials on energy efficiency of vacuum-pressure swing adsorption cycle for CO2 capture
- 2018
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Ingår i: Applied Thermal Engineering. - : Elsevier Ltd. - 1359-4311 .- 1873-5606. ; 128, s. 818-829
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a comprehensive thermodynamic research on energy efficiency of vacuum-pressure swing adsorption (VPSA). The study examined the influence from four types of typical adsorbent materials on the energy efficiency of VPSA by cycle parameters. The selected adsorbent materials are activated carbons, zeolite 5A, zeolite 13X, silica gels, and metal-organic frameworks (MOFs). The study also analyzes the effects of separation temperature, adsorption pressure, desorption pressure, CO2 concentration and percent of unused bed on the energy-efficiency of VPSA cycle. The examined performance parameters are CO2 working capacity, proportionality factor, energy consumption and second-law efficiency. The results show that the energy consumption is approximately 2.0–4.5 MJ/kg and the second-law efficiencies are 4–7% for VPSA cycles using the five adsorbent materials. The effect of adsorbent materials on the energy efficiency mainly depends on the proportionality factor of CO2 working capacity (β) of VPSA cycle, which is important to screen materials at the fixed cyclic boundary conditions and preliminary calculation of second-law efficiency for VPSA cycles. For existing adsorbent materials which are Type I commonly, the lower values of β would lead to the higher second-law efficiencies. The development of new adsorbents of Type III would be extremely urgent in near future.
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| 4. |
- Berisa, Aldin, et al.
(författare)
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AVB-aware Routing and Scheduling for Critical Traffic in Time-sensitive Networks with Preemption
- 2022
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Ingår i: ACM International Conference Proceeding Series. - New York, NY, USA : Association for Computing Machinery. - 9781450396509 ; , s. 207-218
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Konferensbidrag (refereegranskat)abstract
- The Time-Sensitive Network (TSN) amendments and protocols add capabilities on top of standard 802.1 Ethernet for guaranteeing the timeliness of both (isochronous) scheduled traffic (ST) and shaped (audio-video) communication (AVB) in distributed applications. ST streams are guaranteed via an offline computed schedule controlling the time-aware gate mechanism of IEEE 802.1Qbv, while AVB real-time streams are shaped via a credit-based shaper (CBS) and scheduler with lower-priority than ST. Although the two traffic classes use different TSN mechanisms, they are interrelated as the ST traffic class schedule influences the latency of AVB traffic. In this paper, we propose a method for the integration of the ST schedule synthesis with an analysis for the AVB class featuring IEEE 802.1Qbu frame preemption under different configurations to reduce the interference between the two classes. We first present a new worst-case response-time (WCRT) analysis for the AVB traffic class in TSN networks with preemption, considering an arbitrary number of AVB queues and different configurations for the CBS credit behavior. Then, we integrate the creation of ST schedule tables with the schedulability analysis of AVB traffic using a heuristic algorithm featuring frame preemption and a novel routing mechanism aimed at maximizing AVB schedulability. Finally, we evaluate our approach using both real-world and synthetic use cases showing the efficiency both in terms of schedule creation runtime and in terms of increasing the schedulability of lower-priority AVB traffic.
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| 5. |
- Fang, Z., et al.
(författare)
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Achieving an ultralow emission of nitrogen oxides by using activated carbon with hydrophobic modification
- 2021
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Ingår i: Journal of Cleaner Production. - : Elsevier Ltd. - 0959-6526 .- 1879-1786. ; 315
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Tidskriftsartikel (refereegranskat)abstract
- Selective noncatalytic reduction (SNCR) systems have been widely used for denitrification in small capacity boilers, such as biomass- and waste-fueled boilers. However, these systems cannot meet the requirements of ultralow emission regulations, i.e., 50 mg m−3. This work proposes a new solution that combines SNCR and activated carbon (AC). To solve the problem caused by the wettability of AC, which can significantly reduce the quantity of NOx that can be adsorbed and block active cites, hydrophobic modification was employed to amend the properties of AC. The influences of the key operating parameters on the denitrification of AC, including the reaction temperature, O2 concentration, feed gas flow rate, and contents of SO2 and CO2, have been investigated experimentally. A novel solution that combines AC and SNCR was proposed for industrial applications, and the economic feasibility has been verified. The results have demonstrated that this hybrid solution can achieve a low levelized cost of denitrification, which is 59.8% and 33.7% lower than those of SCR and hybrid SNCR/SCR.
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| 6. |
- Yang, S., et al.
(författare)
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Economic feasibility of using fuel cells as backup power supply in data centers
- 2024
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Ingår i: Sustainable Energy Technologies and Assessments. - : Elsevier Ltd. - 2213-1388 .- 2213-1396. ; 69
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Tidskriftsartikel (refereegranskat)abstract
- The backup power system (BPS) is essential to data centers (DCs) in case of grid outage. Currently, the diesel generator (DG) is the most commonly used solution. However, due to the need of decarbonization, fuel cells (FCs) are emerging as a promising alternative. This paper conducts a holistic economic analysis to investigate the benefit from using FCs to replace DGs, which takes into account more key impact factors. Different requirements by different Tiers of DCs, such as on the BPS runtime and the BPS test time, are considered. Under the benchmark condition, i.e. 800 USD/kW for the FC capital cost, 4.8 USD/kg, 1.25 USD/L and 90 USD/ton for hydrogen, diesel, and CO2 prices, the payback period is 13.4 years and 13.1 years when using FCs to replace DGs for Tier 1–2 DCs and Tier 3 DCs. Since Tier 4 DCs require more units, FCs can be economically feasible if the FC capital cost reduces by 20.3 %, the diesel price increases by 19.7 %, or the green hydrogen price decreases by 35.5 %, compared to the benchmark conditions. Among the factors, the FC capital cost, the diesel price, and the hydrogen price are found to affect the payback period mostly.
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| 7. |
- Gao, Y., et al.
(författare)
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Cooling pitch cabinets in wind turbines using a pulsating heat pipe : A case study
- 2023
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Ingår i: Case Studies in Thermal Engineering. - : Elsevier Ltd. - 2214-157X. ; 50
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Tidskriftsartikel (refereegranskat)abstract
- As the electric capacity of wind turbine increases, heat dissipation in pitch cabinets becomes challenging owing to the limited space and rotating conditions. To cool down the pitch cabinet more effectively and allow heat dissipation, we designed and implemented a pulsating heat pipe (PHP) in this study. We designed PHP parameters and conducted performance tests to compare the cooling performance of the fabricated PHP with that of an air-based cooling system in a 1.5 MW wind turbine. The results demonstrated steady PHP operation under rotating conditions (17.3 rpm). At a heat load of 1000 W, the evaporator outlet temperature was only 76.1 °C. However, increasing the ambient temperature adversely affected PHP operation, resulting in higher temperature and thermal resistance. The heat-pipe-based cooling system lowered the insulated gate bipolar transistor (IGBT) temperature by about 20.4 °C in relation to the air-based cooling system, while being suitable under varied conditions. Additionally, the system could successfully operate when the heat load of IGBT was 2350 W, corresponding to a 7 MW electric capacity of the wind turbine. Reducing the manufacturing cost of the heat pipe would further enhance the applicability of this system for pitch cabinet IGBT cooling, such as decreasing payback period.
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| 8. |
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| 9. |
- Guo, S., et al.
(författare)
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Mobilized thermal energy storage : Materials, containers and economic evaluation
- 2018
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Ingår i: Energy Conversion and Management. - : Elsevier Ltd. - 0196-8904 .- 1879-2227. ; 177, s. 315-329
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Tidskriftsartikel (refereegranskat)abstract
- The transportation of thermal energy is essential for users who are located far away from heat sources. The networks connecting them achieve the goal in efficient heat delivery and reasonable cost, especially for the users with large heat demands. However, it is difficult to satisfy the heat supply of the detached or emergent users with the existing pipelines. Therefore, a promising alternative, called mobilized thermal energy storage (M-TES), was proposed to deliver the heat flexibly without the restriction of networks. In this paper, a review of studies on M-TES is conducted in terms of materials, containers and economic evaluation. The potential candidates of materials, such as sugar alcohols, hydrated salts, alkalies and zeolite are reviewed and compared based on their thermophysical properties, price, advantages and disadvantages. Various containers, including the shell-and-tube, encapsulated, direct-contact, detachable and sorptive types, are discussed from the aspects of configuration, performance and utilization. Furthermore, the studies on the economic evaluation of M-TES systems are summarized and discussed based on the analysis of the economic indicators, including initial cost, operating cost, revenue, subsidy and energy cost. Finally, the challenges and future perspectives for developing M-TES are presented.
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| 10. |
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