| 1. |
- Bai, Q., et al.
(författare)
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Experimental investigation on the solidification behavior of phase change materials in open-cell metal foams
- 2017
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Ingår i: Energy Procedia. - : Elsevier Ltd. - 1876-6102. ; , s. 3703-3708
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Konferensbidrag (refereegranskat)abstract
- This study presented an experimental investigation on solidification behavior of fluid saturated in highly porous open-cell copper foams. Particular attention has been made on the effect of pore parameters (pore density and porosity) on the solidification behavior. A purposely-designed apparatus was built for experimental observations. Results showed that the copper foam had a great effect on solidification and the full solidification time can be saved up to 50%, especially preventing the decrease in solidification rate during the later stage of phase change. The smaller the porosity is, the faster the solidification rate will be. Pore density was found to have little influence upon the solidification rate. In addition, the local natural convection does exist but it has a slight effect on solidification, leading to the slant of the solid-liquid interface.
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| 2. |
- Gao, X., et al.
(författare)
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Experimental investigation of the cubic thermal energy storage unit with coil tubes
- 2017
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Ingår i: Energy Procedia. - : Elsevier Ltd. ; 142, s. 3709-3714
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Konferensbidrag (refereegranskat)abstract
- This study presented experimental investigations on the thermal performance of a thermal energy storage (TES) unit with coil tubes. A designed test rig was built and the melting heat transfer characteristics (melting front and temperature distribution) inside the TES unit were examined. The effects of charging flow rate on the overall phase change process were examined. The results showed that natural convection accelerated the thermal energy transport in the melt phase in the top region, but weakened the heat transfer in the bottom region; this resulted in the unmelt PCM at the bottom. The melting heat transfer was overall enhanced by the increase in inlet flow rate, indicating that the full charging time can be shortened by a larger flow rate.
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| 3. |
- Li, Hailong, 1976-, et al.
(författare)
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Feasibility study about using a stand-alone wind power driven heat pump for space heating
- 2018
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Ingår i: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 228, s. 1486-1498
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Tidskriftsartikel (refereegranskat)abstract
- Reducing energy consumption and increasing the use of renewable energy in the building sector are crucial to the mitigation of climate change. Wind power driven heat pumps have been considered as a sustainable measure to supply heat to the detached houses, especially those that even do not have access to the electricity grid. This work is to investigate the dynamic performance of a heat pump system driven by wind turbine through dynamic simulations. In order to understand the influence on the thermal comfort, which is the primary purpose of space heating, the variation of indoor temperature has been simulated in details. Results show that the wind turbine is not able to provide the electricity required by the heat pump during the heating season due to the intermittent characteristic of wind power. To improve the system performance, the influences of the capacity of wind turbine, the size of battery and the setpoint of indoor temperature were assessed. It is found that increasing the capacity of wind turbines is not necessary to reduce the loss of load probability; while on the contrary, increasing the size of battery can always reduce the loss of load probability. The setpoint temperature clearly affects the loss of load probability. A higher setpoint temperature results in a higher loss of thermal comfort probability. In addition, it is also found that the time interval used in the dynamic simulation has significant influence on the result. In order to have more accurate results, it is of great importance to choose a high resolution time step to capture the dynamic behaviour of the heat supply and its effect on the indoor temperature.
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| 4. |
- Salman, Chaudhary Awais, 1986-, et al.
(författare)
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A polygeneration process for heat, power and DME production by integrating gasification with CHP plant : Modelling and simulation study
- 2017
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Ingår i: Proceedings of the 9th International Conference on Applied Energy. - Amsterdam : Elsevier. ; 142, s. 1749-1758
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Konferensbidrag (refereegranskat)abstract
- Biofuels are a good substitute for the transport sector petroleum fuels to minimize carbon footprint and greenhouse gases emissions. Di-Methyl Ether (DME) is one such alternative with properties similar to liquefied petroleum gas but with lower SOx, NOx, and particulate emissions. In this work, a polygeneration process, integrating an existing combined heat and power (CHP) plant with biomass gasification to synthesize DME, is proposed and modelled. Process integration is based on a hypothesis that the CHP plant provides the necessary heat to run the co-located gasification plant for DME synthesis and the waste heat from the gasification process is recovered and transferred to the CHP plant. The feed for gasification is taken as refuse derived fuel (RDF) instead of conventional wood derived biomass. The process integration leads to higher overall combined efficiency (up to 71%) which is greater than stand-alone efficiencies (up to 63%) but lower than stand-alone CHP plant efficiency (73.2%). The further technical evaluation shows that the efficiency of the polygeneration process is depends heavily on the gasifier capacity integrated with the existing CHP plant and also on the conversion route selected for DME synthesis i.e. recycling of unconverted syngas to the DME reactor or transferring it to the boiler of the CHP plant. The simulation results also indicate that once-through conversion yields less DME than recycling, but at the same time, once-through conversion affects the district heat and electric power production of the CHP plant lesser than by using the recycling route.
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| 5. |
- Xu, Nan, et al.
(författare)
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Global optimization energy management for multi-energy source vehicles based on "Information layer - Physical layer - Energy layer- Dynamic programming" (IPE-DP)
- 2022
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 312
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Tidskriftsartikel (refereegranskat)abstract
- To reveal the energy-saving mechanisms of global energy management, we propose a global optimization framework of "information layer-physical layer-energy layer-dynamic programming " (IPE-DP), which can realize the unity of different information scenarios, different vehicle configurations and energy conversions. The deterministic dynamic programing (DP) and adaptive dynamic programming (ADP) are taken as the core algorithms. As a benchmark for assessing the optimality, DP strategy has four main challenges: standardization, real-time application, accuracy, and satisfactory drivability. To solve the above problems, the IPE-DP optimization framework is established, which consists of three main layers, two interface layers and an application layer. To be specific, the full-factor trip information is acquired from three scenarios in the information layer, and then the feasible work modes of the vehicle are determined in the physical layer based on the proposed conservation framework of "kinetic/potential energy & onboard energy ". The above lays a foundation for the optimal energy distribution in the energy layer. Then, a global domain-searching algorithm and action dependent heuristic dynamic programming (ADHDP) model are developed for different information acquisition scenarios to obtain the optimal solution. To improve the computational efficiency under the deterministic information, a fast DP is developed based on the statistical rules of DP behavior, the core of which is to restrict the exploring region based on a reference SOC trajectory. Regarding the stochastic trip information, the ADHDP model is established, including determining the utility function, network design and training process. Finally, two case studies are given to compare the economic performance of the vehicle under different information acquisition scenarios, which lays a foundation for analyzing the relationship between the amount of information input and energy-saving potential of the vehicle. Simulation results demonstrate that the proposed method gains a better performance in both real-time performance and global optimality.
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| 6. |
- Yan, Jinyue, et al.
(författare)
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CO2 capture with the absorbent of a mixed ionic liquid and amine solution considering the effects of SO2 and O2
- 2017
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Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 194, s. 9-18
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Tidskriftsartikel (refereegranskat)abstract
- Room-temperature ionic liquids (ILs) have recently been proposed as a potential candidate for CO2 capture. In this study, experiments were conducted in an absorption-desorption loop system to investigate the effects of SO2 and O2 on CO2 capture using an aqueous amine solution mixed with IL. The gas mixture containing CO2, O2, SO2 and N2 in the composition range of flue gas from a coal-fired power plant after flue gas desulfurization was selected as the feed gas. It was found that the addition of hydrophilic IL of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) to a monoethanolamine (MEA) aqueous solution reduced the losses of MEA and water by lowering the saturated vapour pressure of the mixed absorbent. For hydrophobic IL of 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([hmim][Tf2N]), the MEA loss for 30 wt% MEA + 70 wt% [hmim][Tf2N] increased dramatically with the system running because carbonate, which was formed by MEA reacting with CO2, was insoluble in [hmim][Tf2N] at the absorber operation temperature of 323 K. The effects of O2 and SO2 were relatively insignificant for the MEA and water losses. The aqueous amine solution mixed with [bmim][BF4] showed good performances with a CO2 removal efficiency of above 90% and the SO2 concentration at the absorber outlet below 20 ppb. No obvious IL loss was detected. For the absorbent of 30 wt% MEA + 50 wt% [bmim][BF4] + 20 wt% H2O, the thermal energy consumption for absorbent regeneration is 33.8% lower than that of the aqueous MEA solution.
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| 7. |
- Yang, Ying, et al.
(författare)
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Peak-shaving and profit-sharing model by Aggregators in residential buildings with PV- a case study in Eskilstuna, Sweden
- 2017
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Ingår i: Proceedings of the 9th International Conference on Applied Energy. - : Elsevier. ; 142, s. 3182-3193
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Konferensbidrag (refereegranskat)abstract
- Nowadays, photovoltaic (PV) system combined with energy storage systems is playing increasing significant role in residential buildings in Sweden. At the same time it brings reliability problems because of the intermittency of electricity production and exceptionally distributed reservoir which is followed by the peak-valley electricity prices and power grid fluctuations. There is an increasing need for new business model and economic paradigm for a third party aggregator to bridge the gap between Power Grid and end-users. Providing the valuable electricity services at scale and breaking regulatory arbitrage, aggregators help to deliver desired levels of residents' engagements, value-added services and feasible level of unbundling of electricity market. This paper analyzes how the aggregators grab the indisputable business opportunity to interact between residents and Power Grid from the perspective of physical electricity flows and benefits share of peak-shaving. We employ a real case in Eskilstuna in Sweden to design new business model and validate using data. And the result indicates the compatibility of the aggregator service and its business model. It further sheds light on the pricing model of generated electricity by PV system, and benefits share ratio design.
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| 8. |
- Zhang, Chi, et al.
(författare)
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Can Solar Energy be an Alternative Choice of Milk Production in Dairy Farms? : -A Case study of Integrated PVWP System with Alfalfa and Milk Production in Dairy Farms in China
- 2017
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Ingår i: 8th International Conference on Applied Energy, ICAE 2016; Beijing; China; 8 October 2016 through 11 October 2016. - : Elsevier. ; 105, s. 3953-3959
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Konferensbidrag (refereegranskat)abstract
- As China's dairy consumption grows, both the domestic milk production and the importation of dairy products are increasing to meet market demands. The objective of this study was to quantify electricity usage and cost of milk production with data analysis of dairy farms and evaluate the potential alternative energy supply-solar energy generated by PV water pumping system (PVWP). We collected data in milk production processes from 11 dairy farms in China. By selecting the optimal dairy farm, we simulate the scenario of solar power generation with PVWP system to provide power both for milk and alfalfa production. With estimations of electricity saving, economic cost saving and CO2 saving on every kg milk produced under PVWP system, we conclude that scenario PVWP with alfalfa and milk production can results in value add-ins, new sources of revenue, energy supply and emission reductions.
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| 9. |
- Bai, Fan, et al.
(författare)
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Application of similarity theory in modeling the output characteristics of proton exchange membrane fuel cell
- 2021
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Ingår i: International journal of hydrogen energy. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0360-3199 .- 1879-3487. ; 46:74, s. 36940-36953
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Tidskriftsartikel (refereegranskat)abstract
- Proton Exchange Membrane Fuel Cell (PEMFC) has attracted widespread interest. In the present work, similarity analysis is adopted for a three-dimensional single-phase isothermal model of PEMFC to derive similarity criteria. Seven kinds of input criteria (Pi(1) similar to Pi(7)) are obtained, relevant to the fluid flow, pressure drop, flow resistance in a porous medium, activity loss, diffusion mass transfer, convective mass transfer and ohmic loss in PEMFC respectively. Dimensionless voltage and dimensionless current density are defined as two output criteria. Numerical verifications show that if the seven criteria keep their individual values with their components vary in a wide range, the dimensionless polarization curves keep the same with a deviation about 1%, showing the validity and feasibility of the present analysis. From the effect on the dimensionless polarization curve, sensibility analysis shows that the seven criteria can be divided into three categories: strong (Pi(4) and Pi(7), -94.9% similar to +349.2%), mild to minor (Pi(5) and Pi(6), -4.5% similar to +5.0%), and negligible (Pi(1), Pi(2) and Pi(3), -1.2% similar to +1.1%). The similarity analysis approach can greatly save computation time in modeling the output characteristics of PEMFC. (C) 2021 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.
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| 10. |
- Campana, Pietro Elia, et al.
(författare)
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Managing agricultural drought in Sweden using a novel spatially-explicit model from the perspective of water-food-energy nexus
- 2018
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Ingår i: Journal of Cleaner Production. - : Elsevier. - 0959-6526 .- 1879-1786. ; 197, s. 1382-1393
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Tidskriftsartikel (refereegranskat)abstract
- Using a multi-disciplinary approach, this paper integrated spatial analysis with agricultural and energy system modelling to assess the impacts of drought on crop water demand, water availability, crop yield, and electricity requirements for irrigation. This was done by a novel spatially-explicit and integrated water-food-energy nexus model, using the spatial climatic data generated by the mesoscale MESAN and STRANG models. In this study, the model was applied to quantify the effects of drought on the Swedish irrigation sector in 2013, a typical drought year, for a specific crop. The results show that drought can severely affect the crop yield if irrigation is not applied, with a peak yield reduction of 18 t/ha, about 50 % loss as compared to the potential yield in irrigated conditions. Accordingly, the water and energy requirements for irrigation to halt the negative drought effects and maintain high yields are significant, with the peaks up to 350 mm and 700 kWh per hectare. The developed model can be used to provide near real-time guidelines for a comprehensive drought management system. The model also has significant potentials for applications in precision agriculture, especially using high-resolution satellite data.
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