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  • 1.
    Yan, Jinyue
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. KTH Royal Inst Technol, Dept Chem Engn, Stockholm, Sweden..
    Zhang, Z.
    Chongqing University, Chongqing, China.
    Carbon Capture, Utilization and Storage (CCUS)2019In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 235, p. 1289-1299Article in journal (Refereed)
  • 2.
    Liu, Shengchun
    et al.
    Tianjin University of Commerce, China.
    Wu, Sicheng
    Tianjin University of Commerce, China.
    Hu, Yukun
    University College London, UK.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Comparative analysis of air and CO2 as working fluids for compressed and liquefied gas energy storage technologies2019In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. feb, p. 608-620Article in journal (Refereed)
    Abstract [en]

    With the large-scale use of intermittent renewable energy worldwide, such as wind energy and solar energy, energy storage systems are urgently needed and have been rapidly developed. Technologies of compressed gas energy storage (CGES) and liquefied gas energy storage (LGES) are playing an important role, and air has been commonly used as working fluid. CO2 is another potential working fluid and attracting more and more attention due to the rise of CO2 capture and utilization. However, it is still unclear which is the better working fluid. This paper comparatively analyzed the performance of CGES and LGES systems using air and CO2 as working fluids. Both diabatic and adiabatic CGES are considered. Simulation results show that except diabatic CGES systems, using CO2 could achieve a similar or even higher round-trip efficiency than using air. In addition, the use of CO2 instead of air as a working fluid has additional advantages, such as a lower storage temperature can be achieved at the same storage pressure for the adiabatic CGES system; and a higher condensing temperature can be achieved at the same condensing pressure for the LGES system, which can benefit the system design and operation.

  • 3.
    Lennermo, Gunnar
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Energianalys AB, Alingsås, Sweden.
    Lauenburg, P.
    Lund university, Sweden.
    Werner, S.
    Halmstad university, Sweden.
    Control of decentralised solar district heating2019In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 179, p. 307-315Article in journal (Refereed)
    Abstract [en]

    The purpose of decentralised solar district heating plants is to feed solar heat directly into district heating networks. This decentralised heat supply has to consider two major output conditions: a stable required feed-in supply temperature and a feed-in heat power equal to the heat output from the solar collectors. However, many installations cannot achieve the second output condition, since severe oscillations appear in the feed-in heat power. This problem can be solved by two different control concepts with either temperature- or flow-control. Detailed measurements from two reference plants are provided for these two different control concepts. One main conclusion is that a robust control system is characterized by the ability to provide required flows and temperatures. The major difference between robust and less robust control is that the supply temperatures and/or flows do not fluctuate even if the input conditions are unfavourable. 

  • 4.
    Song, C.
    et al.
    Tianjin University, 92 Weijin Road, Nankai District, Tianjin, China.
    Liu, Q.
    Tianjin University, 92 Weijin Road, Nankai District, Tianjin, China.
    Deng, S.
    Ministry of Education, Tianjin, China.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Kitamura, Y.
    University of Tsukuba, Japan.
    Cryogenic-based CO2 capture technologies: State-of-the-art developments and current challenges2019In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 101, p. 265-278Article in journal (Refereed)
    Abstract [en]

    CO2 capture, utilization and storage has been recognized as a primary option to mitigate the issue of climate change caused by the utilization of fossil fuels. Several CO2 capture strategies have been developed, such as absorption, adsorption, membrane, chemical looping, hydrating and biofixation. Among different technologies, particular attention has been given to cryogenic CO2 capture by phase change. The aim of this study is to improve interest in cryogenic technologies for CO2 capture by providing an overview of the actual status of CCS. To reach this goal, the major strategies and technologies for CO2 capture from fossil fuel combustion have been reviewed. Simultaneously, the characteristics of cryogenic technologies for CO2 capture are summarized. The existing challenges that need to be overcome in cryogenic technology include cold energy sources, capture costs and impurities, etc. Finally, opportunities for the future development of cryogenic-based technologies are discussed. The results of this investigation indicated that cryogenic CO2 capture processes can be easily retrofitted to the existing industrial emission facilities and avoid the challenges associated with chemical solvents or physical sorbents. 

  • 5.
    Li, Yangyang
    et al.
    Tsinghua University.
    Jin, Yiying
    Tsinghua University.
    Borrion, Aiduan
    University College London.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Current status of food waste generation and management in China2019In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 273, p. 654-665Article in journal (Refereed)
  • 6.
    Liu, Shengchun
    et al.
    Tianjin University of Commerce.
    Li, Zheng
    Tianjin University of Commerce.
    Dai, Baomin
    Tianjin University of Commerce.
    Zhong, Zhifeng
    Tianjin University of Commerce.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Song, Mengjie
    Sun, Zhili
    Energetic, economic and environmental analysis of air source transcritical CO2 heat pump system for residential heating in China2019In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 148, p. 1425-1439Article in journal (Refereed)
    Abstract [en]

    Using air source heat pump system for residential heating is a practical way to replace coal-fired boiler in China to alleviate the haze problem, and CO2 is a promising candidate to replace hydrochlorofluorocarbon (HCFC) or hydrofluorocarbon (HFCs) charged into the system. A mathematical model is developed to comprehensively evaluate the energetic, economical and environmental performances of CO2 heat pump system compared with other three traditional heating methods. The results indicate that the primary energy ratio of CO2 heat pump is the highest and it is a rational way to utilize renewable energy with the renewable energy contribution ratio of 0.60–0.69. The initial capital cost of CO2 heat pump is much higher due to the dominant compressor cost. The emission of CO2 heat pump is lower than that of coal-fired boiler at seasonal performance factor above 2.44. The initial and operation cost can be gradually reduced with the mass production and energy efficiency improvement of CO2 heat pump. It is believe that air source CO2 heat pump system can be employed for home heating in China, especial for the hot summer and cold winter region.

  • 7.
    Campana, Pietro Elia
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Royal Institute of Technology, Stockholm, Sweden.
    Wästhage, Louise
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Nookuea, Worrada
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Tan, Y.
    Royal Institute of Technology, Stockholm, Sweden.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Royal Institute of Technology, Stockholm, Sweden.
    Optimization and assessment of floating and floating-tracking PV systems integrated in on- and off-grid hybrid energy systems2019In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 177, p. 782-795Article in journal (Refereed)
    Abstract [en]

    Considering the targets of Thailand in terms of renewable energy exploitation and decarbonization of the shrimp farming sector, this work evaluates several scenarios for optimal integration of hybrid renewable energy systems into a representative shrimp farm. In particular, floating and floating-tracking PV systems are considered as alternatives for the exploitation of solar energy to meet the shrimp farm electricity demand. By developing a dynamic techno-economic simulation and optimization model, the following renewable energy systems have been evaluated: PV and wind based hybrid energy systems, off-grid and on-grid PV based hybrid energy systems, ground mounted and floating PV based hybrid energy systems, and floating and floating-tracking PV based hybrid energy systems. From a water-energy nexus viewpoint, floating PV systems have shown significant impacts on the reduction of evaporation losses, even if the energy savings for water pumping are moderate due to the low hydraulic head. Nevertheless, the study on the synergies between water for food and power production has highlighted that the integration of floating PV represents a key solution for reducing the environmental impacts of shrimp farming. For the selected location, the results have shown that PV systems represent the best renewable solution to be integrated into a hybrid energy system due to the abundance of solar energy resources as compared to the moderate wind resources. The integration of PV systems in off-grid configurations allows to reach high renewable reliabilities up to 40% by reducing the levelized cost of electricity. Higher renewable reliabilities can only be achieved by integrating energy storage solutions but leading to higher levelized cost of electricity. Although the floating-tracking PV systems show higher investment costs as compared to the reference floating PV systems, both solutions show similar competiveness for reliabilities up to 45% due to the higher electricity production of the floating-tracking PV systems. The higher electricity production from the floating-tracking PV systems leads to a better competitiveness for reliabilities higher than 90% due to lower capacity requirements for the storage systems.

  • 8.
    Li, X.
    et al.
    School of Environmental Science and Engineering, Tianjin University, Tianjin, China.
    Zhu, K.
    School of Environmental Science and Engineering, Tianjin University, Tianjin, China.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Key Laboratory of Refrigeration Technology of Tianjin, Tianjin University of Commerce, Tianjin, China.
    Chen, X.
    Key Laboratory of Refrigeration Technology of Tianjin, Tianjin University of Commerce, Tianjin, China.
    Wang, Y.
    Key Laboratory of Refrigeration Technology of Tianjin, Tianjin University of Commerce, Tianjin, China.
    Performance comparison regarding loop heat pipes with different evaporator structures2019In: International journal of thermal sciences, ISSN 1290-0729, E-ISSN 1778-4166, Vol. 136, p. 86-95Article in journal (Refereed)
    Abstract [en]

    The design of evaporator can clearly affect the performance of loop heat pipes (LHPs). In order to understand the influence, three different designs of evaporators were compared, including embedding vapor channels on the heating surface (Config_1), embedding vapor channels in the wick (Config_2), and separating the wick from the heating surface (Config_3). Based on the validated model, the operating temperature, the start-up time, and the transport distance, as key performance indicators, were studied. Results show that, to improve the performance of LHP, it is of importance to reduce the contacting area between the wick and the heating surface. Due to the existence of the steam chamber, the wick was separated from the heating surface in Config_3, resulting in the lowest operating temperature and the shortest start-up time. The pressure head of evaporation is also an important component of the driving force. For Config_3, since the evaporation happened in the steam chamber rather than in the wick, it had a longer transport distance than Config_1 and Config_2 at the same heat load.

  • 9.
    Jurasz, Jakub
    et al.
    Mälardalen University.
    Campana, Pietro Elia
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    The potential of photovoltaic systems to reduce energy costs for office buildings in time-dependent and peak-load-dependent tariffs2019In: Sustainable cities and society, ISSN 2210-6707, Vol. 44, p. 871-879Article in journal (Refereed)
    Abstract [en]

    Electrical power generation across the world is facing dramatic changes for a variety of reasons related to reliability, economics and environmental concerns. Over recent years a significant increase has been observed in installed capacity of photovoltaic systems. Due to their typical seasonal and diurnal energy conversion patterns their integration into power systems creates new opportunities as well as threats. This paper intends to show how photovoltaics can contribute to reducing peak load in office buildings and thereby minimise expenditure on electricity during time- and peak-load-dependent energy prices/tariffs. An additional benefit is also provided to the national power system by reducing the need for peaking power stations. The calculations are performed for energy tariffs commonly used for commercial buildings in Poland. The simulation relies on climatic and price data for 2016. The results show significant potential for photovoltaics to reduce the peak load (from almost 60 kW to slightly over 44 kW) whilst simultaneously minimising energy costs to the building (from 1.2% up to 5.8% depending on the selected tariff). This study demonstrates the economic benefits of using PV system for reducing peak loads. A sensitivity analysis with regard to photovoltaics investment costs is carried out showing that the increasing investment costs have different impact on total energy cost depending on the considered energy tariff.

  • 10.
    Hakalehto, E.
    et al.
    Finnoflag Oy, Kuopio and Siilinjärvi, Finland.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    A microbiological approach to the ecosystem services2018In: Microbiological Environmental Hygiene, Nova Science Publisher Inc. , 2018, p. 433-474Chapter in book (Other academic)
    Abstract [en]

    Man has always exploited the environment for securing human life and culture. This “tradition” is both embedded into our instincts as well as a mode of behavior and a learnt method of survival in our societies. However, alongside with the globalization of the economy, internationalization, industrialization and population growth, the consequences of the one-sided approach of the past have become unbearable for the environment. Consequently, in order to maintain life on earth in its current form, we should establish new thinking and modes of action. Therefore, the survival strategies for Mankind should inherently contain the strive for sustainability, as well as the tendency to avoid past mistakes, and to repair them instantaneously whenever possible. The agricultural tradition of different nations leans on the centuries old wisdom of human civilization in a good sense. For example, the East Asian agricultural societies have learnt to handle each piece of land in their possession in an individual manner, taking into account the local environmental conditions. These principles are now more and more unanimously accepted, at least in theory. Also, the industrial ecosystem needs to be functioning in the natural way, and in balance with the environment. This is a necessity in the reversion or prevention of any developing environmental catastrophes that could wait behind the corner. As the major vehicles for the circulation of matter, microbes are in a key position and provide means for finding the solutions to serve the global ecosystems. In the aftermath of a vast environmental crisis, namely the oil leakage from the “Deepwater Horizon” oil platform well in the Mexican Gulf in the year 2010, it was noticed that the dramatic consequences of the spill were mitigated and the worst scenario of destruction avoided thanks to the cleaning actions of the marine micro-organisms. This was a positive result both ecologically and in economic sense. It further encouraged the scientists to find and isolate microbial strains which could be used for such operations. Although the natural microflora compensated and mitigated the effects of the Deepwater Horizon accident surprisingly well in 2010, there have been observations and concerns about the long term effects of this ecocatastroph (Geggel, 2015).

  • 11.
    Campana, Pietro Elia
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Cioccolanti, Luca
    François, B.
    Jurasz, J.
    Zhang, Yang
    Stridh, Bengt
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    A Multi-Country Economic Analysis Of Lithium-Ion Batteries For Peak Shaving And Price Arbitrage In Commercial Buildings2018Conference paper (Refereed)
  • 12. Prabaharan, N.
    et al.
    Campana, Pietro Elia
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Jerin, A.R.A.
    Palanisamy, K.
    A new approach for grid integration of solar photovoltaic system with maximum power point tracking using multi‐output converter2018Conference paper (Refereed)
  • 13.
    Farooq, U.
    et al.
    East China University of Science and Technology, Shanghai, China.
    Danish, M.
    University of Engineering and Technology Lahore, Faisalabad Campus, Pakistan.
    Lu, S.
    East China University of Science and Technology, Shanghai, China.
    Naqvi, Muhammad
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Qiu, Z.
    East China University of Science and Technology, Shanghai, China.
    Sui, Q.
    Shanghai Institute of Pollution Control and Ecological Security, Shanghai, China.
    A step forward towards synthesizing a stable and regeneratable nanocomposite for remediation of trichloroethene2018In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 347, p. 660-668Article in journal (Refereed)
    Abstract [en]

    Synthesizing supported heterogeneous catalysts is always considered as a persistent approach for degradation of contaminants. However, the stability of these nanocomposites and improvement of process conditions influencing target pollutants degradation are still limited. Herein, on the basis of self-adhesive nature of polydopamine (PDA) and its strong electrostatic interaction with metallic ions, we synthesized a facile, stable, magnetically separable, and environmentally benign PDA decorated, reduced graphene oxide (rGO) supported Fe nanocatalyst (PDA@Fe/rGO). The effects of process variables (pH, PDA@Fe/rGO, and persulphate (PS) dose) on the degradation performance of trichloroethene (TCE), a model chlorinated organic pollutant selected in this study, were investigated. PDA not only encapsulated the host Fe/rGO magnetic particles but also exhibited high magnetization. PDA wrapping tremendously enhanced the thermal stability of nanocatalyst with just 24.1% weight loss at elevated temperature compared to solo Fe/rGO (40.2%). Moreover, TCE degradation mechanism was interpreted by ESR and radical scavenger tests, validating OH[rad], SO4 [rad]− and O2 [rad]− radicals being responsible for TCE degradation. Considering its eminent catalytic activity, simple synthesis approach and excellent kinetics, this recyclable and improved PDA assisted Fe/rGO nanocatalyst further opens a door for practical implementation in the field of contaminated groundwater remediation. 

  • 14.
    Stangeland, Kristian
    et al.
    University of Stavanger.
    Kalai, Dori Yosef
    University of Stavanger.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Yu, Zhixin
    Universitetet i Stavanger.
    Active and stable Ni based catalysts and processes for biogas upgrading: The effect of temperature and initial methane concentration on CO2 methanation2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 227, p. 206-212Article in journal (Refereed)
    Abstract [en]

    CO2 hydrogenation to methane (CO2 methanation) is gaining increasing interest as a major chemical synthesis process for chemical storage of fluctuating renewable energy and producing synthetic natural gas by providing an effective process for biogas upgrading. In this study, a series of 12 and 20 wt% Ni/Al2O3 catalysts, either unpromoted or promoted by 0.5 wt% Ru, were prepared by the incipient wetness method for the CO2 methanation reaction from a feed of pure CO2 or biogas. The catalysts were characterized by N-2 physisorption, XRD, TPR and H-2 chemisorption. The activity for the 12 wt% Ni catalyst increased continuously in the temperature range from 250 degrees C to 400 degrees C. Increasing the Ni loading and Ru promotion greatly improved the activity of the catalyst. At 350 degrees C, the highest CO2 conversion of 82% and CH4 selectivity of 100% was achieved over the 20Ni0.5Ru/Al2O3 catalyst. Thereafter, methanation of a simulated biogas mixture was investigated over the 20Ni/Al2O3 and 20Ni0.5Ru/Al2O3 catalysts. The results showed that the CO2 conversion and CH4 selectivity were only mildly affected by the feed composition. Furthermore, the stability of the catalysts was similar regardless of the feed composition. This study demonstrates that high purity CH4 can be achieved from a biogas feed over our Ni based catalysts.

  • 15.
    Rossi, I.
    et al.
    University of Genoa, Genova, Italy.
    Zaccaria, Valentina
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Traverso, A.
    University of Genoa, Genova, Italy.
    Advanced Control for Clusters of SOFC/Gas Turbine Hybrid Systems2018In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 140, no 5, article id 051703Article in journal (Refereed)
    Abstract [en]

    The use of model predictive control (MPC) in advanced power systems can be advantageous in controlling highly coupled variables and optimizing system operations. Solid oxide fuel cell/gas turbine (SOFC/GT) hybrids are an example where advanced control techniques can be effectively applied. For example, to manage load distribution among several identical generation units characterized by different temperature distributions due to different degradation paths of the fuel cell stacks. When implementing an MPC, a critical aspect is the trade-off between model accuracy and simplicity, the latter related to a fast computational time. In this work, a hybrid physical and numerical approach was used to reduce the number of states necessary to describe such complex target system. The reduced number of states in the model and the simple framework allow real-time performance and potential extension to a wide range of power plants for industrial application, at the expense of accuracy losses, discussed in the paper. 

  • 16.
    Song, C.
    et al.
    Tianjin University, Tianjin, China.
    Liu, Q.
    Tianjin University, Tianjin, China.
    Ji, N.
    Tianjin University, Tianjin, China.
    Deng, S.
    Ministry of Education, Tianjin, China.
    Zhao, J.
    Ministry of Education, Tianjin, China.
    Li, Y.
    Chinese Academy of Sciences, Tianjin, China.
    Song, Y.
    Tianjin University, Tianjin, China.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Alternative pathways for efficient CO2 capture by hybrid processes—A review2018In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 82, p. 215-231Article in journal (Refereed)
    Abstract [en]

    CO2 capture and storage technologies have been recognized as the primary option to mitigate the issue of climate change caused by the utilization of fossil fuels. In the last decades, several CO2 capture approaches have been developed, such as absorption, adsorption, membrane, cryogenic, hydrate and chemical looping combustion etc. However, the energy penalty is a general challenge for each technology. To overcome the disadvantages of standalone technology, the combination of two or more approaches (namely hybrid CO2 capture processes) has been considered as a potential option. In this work, the status and development of hybrid CO2 capture processes is presented in a classification of primary technology as absorption-based, adsorption-based, membrane-based and cryogenic-based. The detail configuration of each hybrid process is introduced. Simultaneously, the characteristics, advantages and potential challenges of each hybrid process are also summarized. Compared to the standalone methods, hybrid processes showed the superiority not only in CO2 recovery and energy penalty, but also in the installation investment. Therefore, hybrid processes can be a promising alternative to conventional CO2 capture technologies in future.

  • 17.
    Hermansson, K.
    et al.
    Sigholm Konsult, Västerås, Sweden.
    Kos, C.
    Flowocean AB, Västerås, Sweden.
    Starfelt, F.
    Vattenfall AB, Uppsala, Sweden.
    Kyprianidis, Konstantinos
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Lindberg, Carl-Fredrik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. ABB Corporate Research, Västerås, Sweden.
    Zimmerman, Nathan
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    An Automated Approach to Building and Simulating Dynamic District Heating Networks2018In: IFAC-PapersOnLine, ISSN 2405-8963, Vol. 51, no 2, p. 855-860Article in journal (Refereed)
    Abstract [en]

    In Nordic countries, district heating accounts for a large share of the consumers’  heat demand. In Sweden, roughly 50% of the total heat demand is attributed to district heating. Which, over the past few years, is equivalent to around 50 TWh, and imposes a difficult balance between supply and demand for the suppliers of district heating. For large networks the propagation of heat from supplier to end-user can vary several hours. Further complexities of large networks, which can consist of multiple overlapping rings, is that during transient conditions the flow can actually change direction. A dynamic modeling library has been developed in Modelica using OpenModelica for district heating networks. Methods for modeling, handling data, simulating and the visualization of results has been developed using Matlab. The model has been validated using data from Mälarenergi  AB, a local provider of district heating in Västerås, Sweden. The model provides to an acceptable degree in predicting the heat propagation and temperature distribution in a localized case study. Adding a higher level of robustness, the model has the capacity to handle bi-directional and reversing flows in complex ring structures. Through this work, the combination of OpenModelica and Matlab, a framework for automating the building and simulation of district heating networks is obtainable. The implications of automating network modeling from computer-aided design drawings allows for a quick robust overview of how the network is working and how prospective additions to the network could impact the end-users. Furthermore, incorporating visual aspects for heat propagation in a network contributes to a higher understanding of complex network structures. 

  • 18.
    Lv, Y.
    et al.
    Qilu University of Technology, School of Mechanical and Automotive .
    Si, P.
    School of Architecture, Tsinghua University, Peking, China.
    Rong, X.
    China Southwest Architecture Design and Research Institute Corp. Ltd., Chengdu, China.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    An Optimization Method for CCHP and River Water Source Heat Pump Combined System2018In: Energy Procedia, Elsevier Ltd , 2018, p. 592-597Conference paper (Refereed)
    Abstract [en]

    Combined Cooling, Heating and Power (CCHP) systems have been widely utilized in the buildings to achieve high efficiency cascade utilization of energy. Heat pump is another widely utilized technology to improve the building energy efficiency. The paper presents a hybrid system which integrates the CCHP with river water source heat pump to combine the advantages of these two technologies. A physical model with energy storage module was firstly developed for the combined system. A case study was further carried out to investigate the optimized configuration and operation performance of the combined system.

  • 19.
    Olsson, Jesper
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Forkman, T.
    Swedish University of Agricultural Sciences, Sweden.
    Gentili, F.G.
    Swedish University of Agricultural Sciences, Sweden.
    Zambrano, Jesús
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Schwede, Sebastian
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Anaerobic co-digestion of sludge and microalgae grown inmunicipal wastewater: A feasibility study2018In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 77, no 3, p. 682-694Article in journal (Refereed)
    Abstract [en]

    In this study a natural mix of microalgae grown in wastewater of municipal character was co-digested with sewage sludge in mesophilic conditions, in both batch and semi-continuous modes. The semicontinuous experiment was divided into two periods with OLR 1 (Organic Loading Rate) of 2.4 kg VS m3 d-1 and HRT1 (Hydraulic Retention Time) of 15 days, and OLR2 of 3.5 kg VS m3 d-1 and HRT2 of 10 days respectively. Results showed stable conditions during both periods. The methane yield was reduced when adding microalgae (from 200 ± 25 NmL CH4 g VSin-1 , to 168±22 NmL CH4 g VSin-1). VS reduction was also decreased by 51%. This low digestability was confirmed in the anaerobic batch test. However, adding microalgae improved the dewaterability of the digested sludge. The high heavy metals content in the microalgae resulted in a high heavy metals content in the digestate, making it more difficult to reuse the digestate as fertilizer on arable land. The heavy metals are thought to originate from the flue gas used as a CO2 source during the microalgae cultivation. Therefore the implementation of CO2 mitigation via algal cultivation requires careful consideration regarding thesource of the CO2-rich gas.

  • 20.
    Diehl, Stefan
    et al.
    Lund Univ, Ctr Math Sci, POB 118,Lund, Sweden..
    Zambrano, Jesus
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Carlsson, Bengt
    Uppsala Univ, Dept Informat Technol, POB 337, Uppsala, Sweden..
    Analysis of photobioreactors in series2018In: Mathematical Biosciences, ISSN 0025-5564, E-ISSN 1879-3134, Vol. 306, p. 107-118Article in journal (Refereed)
    Abstract [en]

    A photobioreactor (PBR) contains microalgae which under illumination consume carbon dioxide and substrate dissolved in water, and produce oxygen. The process is used in water recovery resource facilities with a continuous flow of wastewaster through the PBR. With several PBRs in series the reduction of substrate can be improved. This paper contains a thorough analysis of a model of PBRs in series, where each PBR is modelled with a system of three ordinary differential equations for the concentrations of dissolved substrate and biomass (algae), and the internal cell quota of substrate to biomass. Each PBR has a certain volume and irradiation. The absorption rate of substrate into the cells is modelled with Monod kinetics, whereas the biomass growth rate is modelled with Droop kinetics, in which both a minimum and a maximum internal cell quota are assumed. The main result is that the model has a unique stable steady-state solution with algae in all PBRs. Another stable steady-state solution is the wash-out solution with no algae in the system. Other steady-state solutions are combinations of these two with no algae in some of the first PBRs and algae in the rest of the PBRs in the series. Conditions on the illumination, volumetric flow and volumes of the PBRs are given for the respective solution. Numerical solutions illustrate the theoretical results and indicate further properties.

  • 21.
    Goldberg, C.
    et al.
    Cranfield University, Bedfordshire, United Kingdom.
    Nalianda, D.
    Cranfield University, Bedfordshire, United Kingdom.
    Sethi, V.
    Cranfield University, Bedfordshire, United Kingdom.
    Pilidis, P.
    Cranfield University, Bedfordshire, United Kingdom.
    Singh, R.
    Cranfield University, Bedfordshire, United Kingdom.
    Kyprianidis, Konstantinos
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Assessment of an energy-efficient aircraft concept from a techno-economic perspective2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 221, p. 229-238Article in journal (Refereed)
    Abstract [en]

    An increase in environmental awareness in both the aviation industry and the wider global setting has led to large bodies of research dedicated to developing more sustainable technology with a lower environmental impact and lower energy usage. The goal of reducing environmental impact has necessitated research into revolutionary new technologies that have the potential to be significantly more energy efficient than their predecessors. However, for innovative technologies in any industry, there is a risk that adoption will be prohibitively expensive for commercial application. It is therefore important to model the economic factors of the new technology or policy at an early stage of development. This research demonstrates the application of a Techno-economic Environmental Risk Assessment framework that may be used to identify the economic impact of an energy-efficient aircraft concept and the impact that environmental policy would have on the viability of the concept. The framework has been applied to a case study aircraft designed to achieve an energy saving of 60% in comparison to a baseline 2005 entry-into-service aircraft. The model compares the green aircraft concept to a baseline conventional aircraft using a sensitivity analysis of the aircraft direct operating cost to changes in acquisition and maintenance cost. The research illustrates an economically viable region for the technology. Cost margins are identified where the increase in operating cost due to expensive novel technology is counterbalanced by the reduction in cost resulting from low energy consumption. Viability was found to be closely linked to fuel price, with a low fuel price limiting the viability of energy-efficient aviation technology. In contrast, a change in environmental taxation policy was found to be beneficial, with the introduction of carbon taxation incentivising the use of an environmentally optimised aircraft.

  • 22.
    Roberto Caetano, N.
    et al.
    Aerospace Engineering, Department of Mechanical Engineering, Federal University of Santa Maria, Brazil.
    Schmitz Venturini, M.
    Aerospace Engineering, Department of Mechanical Engineering, Federal University of Santa Maria, Roraima Avenue, 1000, Santa Maria, RS, Brazil.
    Roman Centeno, F.
    Department of Mechanical Engineering, Federal University of Rio Grande do Sul, Brazil.
    Katiuscia Lemmertz, C.
    Department of Mechanical Engineering, Federal University of Rio Grande do Sul, Sarmento Leite Street, 425, Porto Alegre, RS, Brazil.
    Kyprianidis, Konstantinos
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Assessment of mathematical models for prediction of thermal radiation heat loss from laminar and turbulent jet non-premixed flames2018In: Thermal Science and Engineering Progress, ISSN 2451-9049, Vol. 7, p. 241-247Article in journal (Refereed)
    Abstract [en]

    Radiation plays an important role in several processes, being of particular interest to energy efficiency and safety of staff and facilities, mainly in the aerospace industry. In this context, along the last years mathematical models have been developed and reported in the literature aiming to obtain reliable predictions of thermal radiation in combustion applications. Some simplified models consider that thermal radiation emmited by a flame is mainly governed by the flame temperature, while other ones also account for the contribution of the combustion products. On the other hand, more detailed models include both flame geometry and composition. Many efforts have been made by several scientists in order to develop these models, however, there is no validation applied in different operating conditions found in the literature. Thus, the novelty brought by this work consists in an assessment on the comparison between the experimental data of thermal radiation emitted by jet non-premixed flames and the results obtained by calculations applying these models on several flame conditions, encompassing a wide range of applications: laminar and turbulent flames, buoyancy and momentum-driven flames, low-carbon and high-carbon fuels. Such assessments are important to assist combustion system designers on selecting the most adequate thermal radiation model during the project of a combustion system or process. The results found in the current investigation pointed out to a good agreement between experimental data and predictions obtained by detailed models, which consider flame geometry and radiative properties. On the other hand, simplified models must be avoided if accurate predictions of radiation are being sought, despite this, they can be employed as engineering tools for risk analysis, once, in general, they provided higher predictions when compared to the experiments, resulting in a safety factor to engineers and designers.

  • 23.
    Sylwan, Ida
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Runtti, Hanna
    Oulu University, Finland.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Zambrano, Jesus
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Westholm, Lena Johansson
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    BIOCHAR ADSORPTION FOR SEPARATION OF HEAVY METALSIN MUNICIPAL WASTEWATER TREATMENT2018Conference paper (Other academic)
  • 24. Zhang, Yang
    et al.
    Campana, Pietro Elia
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Anders, Lundblad
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Zhang, Chi
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. KTH, Sweden.
    Building Energy System: From System Planning To Operation2018Conference paper (Refereed)
  • 25.
    Feng, J. -C
    et al.
    School of Engineering, Sun Yat-Sen University, Guangzhou, China.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. School of Chemical Science and Engineering, Royal Institute of Technology, Teknikringen 42, Stockholm, Sweden.
    Yu, Z.
    School of Engineering, Sun Yat-Sen University, Guangzhou, China.
    Zeng, X.
    School of Engineering, Sun Yat-Sen University, Guangzhou, China.
    Xu, W.
    School of Engineering, Sun Yat-Sen University, Guangzhou, China.
    Case study of an industrial park toward zero carbon emission2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 209, p. 65-78Article in journal (Refereed)
    Abstract [en]

    Industrial park shoulders heavy responsibilities for economic development, and in the meantime, acts the role as energy consumer and carbon emitter. Under the background of holding the average global temperature increase limited in 2 °C compared to the pre-industrial level, which was proposed in the Paris Agreement, the development of zero carbon emission at the industrial park level is of great importance. This study investigated how to realize zero carbon emission at an industrial park level. In addition, a practical case study of the Southern China Traditional Chinese Medicine Industrial Park located in the Zhongshan City, Guangdong Province of China was conducted. Scenario analyses were projected to realize zero carbon emission in this industrial park and the results show that zero carbon emission can be realized under all the three scenarios. Economic assessments found that purchasing carbon offsets get the minimum cost effectiveness under current market situation. However, purchasing carbon offset may not be the best choice from the aspect of absolute reduction. Sensitivity analyses illustrate that the cost effectiveness of carbon reduction is remarkably influenced by the carbon price and solar energy cost reduction ratio. Meanwhile, applying large-scale renewable energy and producing more carbon offset can harvest more economic and carbon reduction benefits when the current solar energy cost has been reduced by 90%. Moreover, challenges of building zero-carbon industrial park as well as the corresponding solution schemes were discussed.

  • 26.
    Naqvi, Salman Raza
    et al.
    Natl Univ Sci & Technol NUST, Sch Chem & Mat Engn, Islamabad, Pakistan..
    Naqvi, Muhammad
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Catalytic fast pyrolysis of rice husk: Influence of commercial and synthesized microporous zeolites on deoxygenation of biomass pyrolysis vapors2018In: International journal of energy research (Print), ISSN 0363-907X, E-ISSN 1099-114X, Vol. 42, no 3, p. 1352-1362Article in journal (Refereed)
    Abstract [en]

    Research on utilization of abundant rice residue for valuable bioenergy products is still not explored completely. A simple, robust, cheap, and one-step fast pyrolysis reactor is still a key demand for production of bioenergy products, ie, high quality bio-oil and biochar. Bio-oil extracted from fast pyrolysis does not have adequate quality (eg, acidic and highly oxygenated). Catalytic fast pyrolysis using zeolites in the fast pyrolysis process effectively reduces the oxygen content (no H-2 required). In this paper, the zeolites with different pore sizes and shapes (small pore, SAPO-34 (0.56) and ferrierite (30); medium pore, ZSM-5 (30), MCM-22 (30), and ITQ-2 (30); and large pore zeolite, mordenite (30)) were tested in a drop-type fixed-bed pyrolyzer. Catalytic deoxygenation is conducted at 450 degrees C at the catalyst/biomass ratio of 0.1. Zeolite catalysts, its pore size and shape, could influence largely on deoxygenation. It was found that the small pore zeolites did not produce aromatics as compared to higher amount of aromatics formed in case of medium pore zeolites. ZSM-5 and ITQ-2 zeolites were especially efficient for the higher deoxygenation of biomass pyrolysis vapors due to better pore dimension and higher acidity.

  • 27. Jianguo, Li
    et al.
    Shaokai, Zhang
    Li, Hailong
    Mälardalen University, School of Innovation, Design and Engineering. Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Xinhua, Ouyang
    Liulian, Huang
    Yonghao, Ni
    Lihui, Chen
    Cellulase pretreatment for enhancing cold caustic extraction-based separation of hemicelluloses and cellulose from cellulosic fibers2018In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 251, p. 1-6Article in journal (Refereed)
  • 28. Zhang, Chi
    et al.
    Campana, Pietro Elia
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Liu, C.
    Zhang, Yang
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. KTH, Sweden.
    Wang, K.
    Choice Preferences And Willingness‐To‐Pay For Crowd‐Funding With Integrated Photovoltaic Water Pumping System In Dairy Milk Production In China2018Conference paper (Refereed)
  • 29.
    Chaudhary, R.
    et al.
    Indian Inst Technol, Ctr Environm Sci & Engn, Maharashtra, India.
    Tong, Y. W.
    Natl Univ Singapore, Dept Chem & Biomol Engn, Singapore..
    Dikshit, Anil Kumar
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. IndianInst Technol, Ctr Environm Sci & Engn, Maharashtra, India; Asian Inst Technol, Sch Environm Resources & Dev, Pathumthani,Thailand.
    CO2-assisted removal of nutrients from municipal wastewater by microalgae Chlorella vulgaris and Scenedesmus obliquus2018In: International Journal of Environmental Science and Technology, ISSN 1735-1472, E-ISSN 1735-2630, Vol. 15, no 10, p. 2183-2192Article in journal (Refereed)
    Abstract [en]

    Axenic culture of microalgae Chlorella vulgaris ATCC((R)) 13482 and Scenedesmus obliquus FACHB 417 was used for phycoremediation of primary municipal wastewater. The main aim of this study was to measure the effects of normal air and CO2-augmented air on the removal efficacy of nutrients (ammonia N and phosphate P) from municipal wastewater by the two microalgae. Batch experiments were carried out in cylindrical glass bottles of 1L working volume at 25 degrees C and cool fluorescent light of 6500lux maintaining 14/10h of light/dark cycle with normal air supplied at 0.2Lmin(-1) per liter of the liquid for both algal strains for the experimental period. In the next set of experiments, the treatment process was enhanced by using 1, 2 and 5% CO2/air (vol./vol.) supply into microalgal cultures. The enrichment of inlet air with CO2 was found to be beneficial. The maximum removal of 76.3 and 76% COD, 94.2 and 92.6% ammonia, and 94.8 and 93.1% phosphate after a period of 10days was reported for C. vulgaris and S. obliquus, respectively, with 5% CO2/air supply. Comparing the two microalgae, maximum removal rates of ammonia and phosphate by C. vulgaris were 4.12 and 1.75mgL(-1)day(-1), respectively, at 5% CO2/air supply. From kinetic study data, it was found that the specific rates of phosphate utilization (q(phsophate)) by C. vulgaris and S. obliquus at 5% CO2/air supply were 1.98 and 2.11day(-1), respectively. Scale-up estimation of a reactor removing phosphate (the criteria pollutant) from 50 MLD wastewater influent was also done.

  • 30.
    Olsson, Jesper
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Co-digestion of microalgae and sewage sludge - A feasibility study for municipal wastewater treatment plants2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The increased emissions of anthropogenic greenhouse gases over the last 100 years is the reason for the acceleration in the greenhouse effect, which has led to an increase of the globally averaged combined land and ocean surface temperature of 0.85 °C between 1880 and 2012. A small fraction of the increased anthropogenic greenhouse gases originates from municipal wastewater treatment plants (WWTPs).

    This doctoral thesis was part of a larger investigation of using an alternative biological treatment based on the symbiosis of microalgae and bacteria (MAAS-process (microalgae and activated sludge)). This solution could be more energy efficient and potentially consume carbon dioxide from fossil combustion processes and also directly capture carbon dioxide from the atmosphere and thereby reduce the addition of anthropogenic greenhouse gases to the air.

     The objective of the thesis was to explore the effects when the microalgae-derived biomass from the biological treatment were co-digested with sewage sludge. The results from these experimental studies were then used to evaluate the effects on a system level when implementing microalgae in municipal WWTP.

     Microalgae grown from a synthetic medium improved the methane yield with up to 23% in mesophilic conditions when part of the sewage sludge was replaced by the microalgae. The microalgae grown from municipal wastewater showed no synergetic effect.

     In the semi-continuous experiments the methane yield was slightly reduced when implementing the microalgae. Furthermore the digestibility of the co-digestion between sewage sludge and microalgae were lower compared to the digestion of sewage sludge.

     The digestates containing microalgal substrate had higher heavy metals content than digestates containing only sewage sludge. This could have a negative effect on the potential to use this digestate on arable land in future, due to strict limits from the authorities.  Filterability measurements indicated that the addition of microalgae enhanced the dewaterability of the digested sludge and lowered the demand for polyelectrolyte significantly.

     When a hypothetical MAAS-process replaced a conventional ASP-process the amount of feedstock of biomass increased significantly due to the increased production from the autotrophic microalgae. This increased the biogas production by 66-210% and reduced the heavy metal concentration in the digestate due to a dilution effect from the increased biomass production.

     The thesis demonstrates that microalgae in combination with bacteria from a MAAS-process can be a realistic alternative feedstock to WAS in the anaerobic digestion at a municipal WWTP. A few drawbacks need to be considered when choosing a MAAS-process as biological treatment.

  • 31.
    Thorin, Eva
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Olsson, Jesper
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Schwede, Sebastian
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Co-digestion of sewage sludge and microalgae: Biogas production investigations2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 227, p. 64-72Article in journal (Refereed)
    Abstract [en]

    In municipal wastewater treatment plants (WWTPs), algae could be utilised for cleaning the water and, at thesame time, produce a biomass that can be used for energy. Through anaerobic digestion, microalgae can contributeto biogas production when co-digested with sewage sludge. In this paper, previous published results onthe co-digestion of sewage sludge and microalgae are summarised and reviewed, and any remaining knowledgegaps are identified. The batch tests currently documented in literature mostly concern digestion under mesophilicconditions, and studies investigating thermophilic conditions are less common. The average biochemicalmethane potential (BMP) for 29 different mixtures co-digested under mesophilic conditions is 317 ± 101 N cm3CH4 gVS−1 while the result for 12 different mixtures investigated under thermophilic conditions is a BMP of318 ± 60 N cm3 CH4 gVS−1. An evaluation of the heat required for increasing the temperature from mesophilicto thermophilic conditions shows that increased methane production under thermophilic conditions can beenough to create a positive energy balance. For a full-scale WWTP, using thermophilic digestion on sludge, or acombination of sludge and microalgae could therefore be of interest. This is dependent on the demands onsanitation of the sludge and the possibilities for heat recovery.Most of the mesophilic investigations indicate a synergetic effect for co-digestion, with enhancements of up toalmost 70%. However, the results are uncertain since the standard deviations for some of the BMP tests are in thesame order of magnitude as the identified enhancement. Neither of the presented publications provide an understandingof the basic mechanisms that led to higher or lower BMP when microalgae were mixed with wastewatersludge. We, therefore, call for care to be taken when assuming any effects related to the specification ofsubstrates. Microalgae and wastewater sludge have several similarities, and the specific results of BMP in themixtures relate more to the specifics of the respective materials than the materials themselves.Investigations into semi-continuous processes of co-digestion of microalgae and sludge are scarce. The yieldsfor three co-digestion studies show high variation, with an average of 293 ± 112 N cm3 gVSin−1. The availableresults show strong potential for co-digestion of sewage sludge and microalgae. Further investigations are requiredto identify optimal conditions for biogas production, and analysis of microalgae implementation onwastewater treatment at a system level is also needed to identify the total mass balance of substrate and nutrientrecovery.

  • 32.
    Yang, Xiaohu
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Institute of the Building Environment & Sustainability Technology, School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, China.
    Bai, Q.
    Institute of the Building Environment & Sustainability Technology, School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, China.
    Guo, Z.
    Institute of the Building Environment & Sustainability Technology, School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, China.
    Niu, Z.
    Institute of the Building Environment & Sustainability Technology, School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, China.
    Yang, C.
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, Singapore.
    Jin, L.
    Institute of the Building Environment & Sustainability Technology, School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, China.
    Lu, T. J.
    State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing, China.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Department of Chemical Engineering and Technology/Energy Processes, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Comparison of direct numerical simulation with volume-averaged method on composite phase change materials for thermal energy storage2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 229, p. 700-714Article in journal (Refereed)
    Abstract [en]

    Melting heat transfer in open-cell metal foams embedded in phase-change materials (PCMS) predicted by the volume-averaged method (VAM) was systematically compared with that calculated using direct numerical simulation (DNS), with particular attention placed upon the contribution of natural convection in the melt region to overall phase change heat transfer. The two-temperature model based on the assumption of local thermal non-equilibrium was employed to account for the large difference of thermal conductivity between metallic ligaments and PCM (paraffin). The Forchheimer extended Darcy model was employed to describe the additional flow resistance induced by metal foam. For the DNS, a geometric model of metal foam based on tetrakaidehedron cells was reconstructed. The DNS results demonstrated significant temperature difference between ligament surface and PCM, thus confirming the feasibility of local thermal non-equilibrium employed in VAM simulations. Relative to the DNS results, the VAM combined with the two-temperature model could satisfactorily predict transient solid-liquid interface evolution and local temperature distribution, although pore-scale features of phase change were lost. The presence of natural convection affected significantly the melting front shape, temperature distribution and full melting. The contribution of natural convection to overall phase change heat transfer should be qualitatively and quantitatively given sufficient consideration from both macroscopic (VAM) and microscopic (DNS) point of views. Besides, practical significance and economic prospective using metal foam in TES unit for WHR system to provide residential heating or hot water is discussed and analyzed.

  • 33.
    Jaradat, Omar
    Mälardalen University, School of Innovation, Design and Engineering. Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Contracts-Based Maintenance of Safety Cases2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Safety critical systems are those systems whose failure could result in loss of life, significant property damage, or damage to the environment. System safety is a major property that shall be adequately assured to avoid any severe outcomes in safety critical systems. Safety assurance should provide justified confidence that all potential risks due to system failures are either eliminated or acceptably mitigated. System developers in many domains (e.g., automotive, avionics, railways) should provide convincing arguments regarding the safe performance of their systems to a national or international regulatory authority and obtain approvals before putting the system into service.  Building 'Safety cases' is a proven technique to argue about and communicate systems' safety and it has become a common practice in many safety critical system domains. System developers use safety cases to articulate claims about how systems meet their safety requirements and objectives, collect and document items of evidence, and construct a safety argument to show how the available items of evidence support the claims.

    Safety critical systems are evolutionary and constantly subject to preventive, perfective, corrective or adaptive changes during both the development and operational phases. Changes to any part of those systems can undermine the confidence in safety since changes can refute articulated claims about safety or challenge the supporting evidence on which this confidence relies. Hence, safety cases need to be built as living documents that should always be maintained to justify the safety status of the associated system and evolve as these systems evolve. However, building safety cases are costly since they require a significant amount of time and efforts to define the safety objectives, generate the required evidence and conclude the underlying logic behind the safety case arguments. Safety cases document highly dependent elements such as safety goals, assumptions and evidence. Seemingly minor changes may have a major impact. Changes to a system or its environment can necessitate a costly and painstaking impact analysis for systems and their safety cases. In addition, changes may require system developers to generate completely new items of evidence by repeating the verification activities. Therefore, changes can exacerbate the cost of producing and maintaining safety cases.  

    Safety contracts have been proposed as a means for helping to manage changes. There have been works that discuss the usefulness of contracts for reusability and maintainability. However, there has been little attention on how to derive them and how exactly they can be utilised for system or safety case maintenance.

    The main goal of this thesis is to support the change impact analysis as a key factor to enhance the maintainability of safety cases. We focus on utilising safety contracts to achieve this goal. To address this, we study how safety contracts can support essential factors for any useful change management process, such as (1) identifying the impacted  elements  and  those  that  are  not  impacted, (2) minimising the number of impacted  safety  case  elements, and (3) reducing the  work  needed  to  make  the  impacted  safety  case  elements valid again. The preliminary finding of our study reveals that using safety contracts can be promising to develop techniques and processes to facilitate safety case maintenance. The absence of safety case maintenance guidelines from safety standards and the lack of systematic and methodical maintenance techniques have motivated the work of this thesis. Our work is presented through a set of developed and assessed techniques, where these techniques utilise safety contracts to achieve the overall goal by various contributions. We begin by a framework for evaluation of the impact of change on safety critical systems and safety cases. Through this, we identify and highlight the most sensitive system components to a particular change. We propose new ways to associate system design elements with safety case arguments to enable traceability. How to identify and reduce the propagation of change impact is addressed subsequently.  Our research also uses safety contracts to enable through-life safety assurance by monitoring and detecting any potential mismatch between the design safety assumptions and the actual behaviour of the system during its operational phase. More specifically, we use safety contracts to capture thresholds of selected safety requirements and compare them with the runtime related data (i.e., operational data) to continuously assess and evolve the safety arguments.

    In summary, our proposed techniques pave the way for cost-effective maintenance of safety cases upon preventive, perfective, corrective or adaptive changes in safety critical systems thus helping better decision support for change impact analysis.

  • 34.
    Lv, Y.
    et al.
    School of Mechanical and Automotive Engineering, Qilu University of Technology, Jinan, China.
    Xia, L.
    School of Mechanical and Automotive Engineering, Qilu University of Technology, Jinan, China.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Bi, J.
    School of Mechanical and Automotive Engineering, Qilu University of Technology, Jinan, China.
    Design of a Hybrid Fiber Optic Daylighting and PV Solar Lighting System2018In: Energy Procedia, Elsevier Ltd , 2018, p. 586-591Conference paper (Refereed)
    Abstract [en]

    Residential buildings with limited natural lighting are generally lit by fuel-based electricity which contributes to increase of CO2 concentration in the atmosphere. This paper presents the design of a hybrid fiber-optic daylighting and PV solar lighting system for household applications. The system is composed of a light collecting subsystem, a light guiding subsystem, an optical fiber light diffuser subsystem and corresponding control system. Preliminary system performance shows that, the developed system could provide comfortable and natural indoor illumination. Meanwhile, the hybrid lighting system can provide an average of 9h of electric lighting under clear sky conditions, and reduce 158.2kg of carbon dioxide emission in a year within the tested dark room of 5m2.

  • 35.
    Lv, Y.
    et al.
    Qilu University of Technology (Shandong Academy of Sciences), Jinan, China.
    Si, P.
    Tsinghua University, Peking, China.
    Rong, X.
    China Southwest Architecture Design and Research Institute Corp. Ltd., Chengdu, China.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Royal Institute of Technology, Stockholm, Sweden.
    Feng, Y.
    China Southwest Architecture Design and Research Institute Corp. Ltd., Chengdu, China.
    Zhu, X.
    Sichuan Provincial Architectural Design Institute, Chengdu, China.
    Determination of optimum tilt angle and orientation for solar collectors based on effective solar heat collection2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 219, p. 11-19Article in journal (Refereed)
    Abstract [en]

    Determination of optimum tilt angle and orientation of solar collectors by maximizing the total solar radiation may overestimate the energy production benefits, because a considerable amount of solar radiation is ineffective for practical solar collectors. In this paper, the concept of effective solar heat collection is proposed to rule out the ineffective solar radiation that could not be converted to available energy. Accordingly, an optimized mathematical model is developed and used to determine the optimum tilt angle and orientation of solar collectors installed in Lhasa during the heating season. Compared with the total solar radiation based optimum results, there is a deviation of 5° in the optimum orientations based on the effective solar heat collection. The case study shows that it is not advisable to adjust the optimum tilt angle on a monthly basis because there is no significance change in total solar energy gains in comparison with the case of no such adjustment during the heating season. In addition, the correction factors to achieving the maximum effective solar heat collection are given at different tilt angles and orientations to guide installation of solar collectors in practical engineering applications.

  • 36.
    Rahman, Moksadur
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Zaccaria, Valentina
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Xin, Zhao
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Kyprianidis, Konstantinos
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Diagnostics-Oriented Modelling of Micro Gas Turbines for Fleet Monitoring and Maintenance Optimization2018In: Processes, ISSN 2227-9717, E-ISSN 1099-5862, Vol. 6, no 11Article in journal (Refereed)
    Abstract [en]

    The market for the small-scale micro gas turbine is expected to grow rapidly in the coming years. Especially, utilization of commercial off-the-shelf components is rapidly reducing the cost of ownership and maintenance, which is paving the way for vast adoption of such units. However, to meet the high-reliability requirements of power generators, there is an acute need of a real-time monitoring system that will be able to detect faults and performance degradation, and thus allow preventive maintenance of these units to decrease downtime. In this paper, a micro gas turbine based combined heat and power system is modelled and used for development of physics-based diagnostic approaches. Different diagnostic schemes for performance monitoring of micro gas turbines are investigated.

  • 37.
    Wang, C.
    et al.
    Tianjin University, Tianjin, China.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. KTH, Stockholm, Sweden.
    Marnay, C.
    Lawrence Berkeley National Laboratory, CA, United States.
    Djilali, N.
    University of Victoria, Victoria, Canada.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Wu, J.
    Cardiff University, Cardiff, United Kingdom.
    Jia, H.
    Tianjin University, Tianjin, China.
    Distributed Energy and Microgrids (DEM)2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 210, p. 685-689Article in journal (Refereed)
  • 38.
    Zhang, C.
    et al.
    Energy Processes Division, Royal Institute of Technology, Stockholm, Sweden.
    Campana, Pietro Elia
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Energy Processes Division, Royal Institute of Technology, Stockholm, Sweden.
    Yang, J.
    School of Humanities and Economic Management, China University of Geosciences, Beijing, China.
    Yu, C.
    Department of Earth System Science, Tsinghua University, Beijing, China.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Energy Processes Division, Royal Institute of Technology, Stockholm, Sweden.
    Economic assessment of photovoltaic water pumping integration with dairy milk production2018In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 177, p. 750-764Article in journal (Refereed)
    Abstract [en]

    As dairy consumption grows, domestic dairy farms face challenges in reducing the cost of feeds and the production of high-quality milk for market demands. This paper aims to introduce and integrate solar energy into the milk production chain to investigate its economic performance. By collecting data on milk production processes from 11 dairy farms in China, we quantified electricity usage and costs of milk production to identify the best and worst cases. Crop yields response to the water demand and the electricity requirements of the dairy farms were considered. The study simulated scenarios of self-sufficiency at 20%, 80%, and 100%, in the identified farms by integrating a photovoltaic water pumping (PVWP) system to provide both power and water for alfalfa and other feeds’ irrigation and subsequent milk production. We evaluated annual discounted cost, revenue and net profit under each scenario and case. The results showed that a dairy farm with an integrated PVWP system and self-sufficient feeds would lead to value add-ins, such as electricity saving with solar energy generation, economic cost saving of crops, and CO2 emission reduction. The analysis on return on investment (ROI) and internal rate of return (IRR) revealed that not all the self-sufficient feeds can bring positive marginal profit. Among the investigated scenarios and cases, the dairy farm marked out by the highest ROI with 3.12 and IRR with 20.4%, was the farm where the integrated PVWP system was used to reach 20% self-sufficiency (self-production of only alfalfa). The other scenarios and cases with higher levels of self-sufficiency showed lower ROIs and IRRs. This indicates that high self-production levels of feeds decrease the total profit due to high investment cost. Sensitivity analyses of crop price and operational cost were conducted for ROI with single and double factor approaches. Scale and production of feeds proportions should be carefully considered in improving the economic performance of dairy milk production.

  • 39.
    Ding, Y.
    et al.
    College of Electrical Engineering, Zhejiang University, Hangzhou, ChinaCollege of Electrical Engineering, Zhejiang University, Hangzhou, ChinaCollege of Electrical Engineering, Zhejiang University, Hangzhou, ChinaCollege of Electrical Engineering, Zhejiang University, Hangzhou, ChinaCollege of Electrical Engineering, Zhejiang University, Hangzhou, ChinaCollege of Electrical Engineering, Zhejiang University, Hangzhou, China.
    Shao, C.
    College of Electrical Engineering, Zhejiang University, Hangzhou, China.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Division of Energy Processes, KTH-Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
    Song, Y.
    College of Electrical Engineering, Zhejiang University, Hangzhou, China.
    Zhang, C.
    Division of Energy Processes, KTH-Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
    Guo, C.
    College of Electrical Engineering, Zhejiang University, Hangzhou, China.
    Economical flexibility options for integrating fluctuating wind energy in power systems: The case of China2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 228, p. 426-436Article in journal (Refereed)
    Abstract [en]

    The inherent stochastic nature of wind power requires additional flexibility during power system operation. Traditionally, conventional generation is the only option to provide the required flexibility. However, the provision of the flexibility from the conventional generation such as coal-fired generating units comes at the cost of significantly additional fuel consumption and carbon emissions. Fortunately, with the development of the technologies, energy storage and customer demand response would be able to compete with the conventional generation in providing the flexibility. Give that power systems should deploy the most economic resources for provision of the required operational flexibility, this paper presents a detailed analysis of the economic characteristics of these key flexibility options. The concept of “balancing cost” is proposed to represent the cost of utilizing the flexible resources to integrate the variable wind power. The key indicators are proposed respectively for the different flexible resources to measure the balancing cost. Moreover, the optimization models are developed to evaluate the indicators to find out the balancing costs when utilizing different flexible resources. The results illustrate that exploiting the potential of flexibility from demand side management is the preferred option for integrating variable wind power when the penetration level is below 10%, preventing additional fuel consumption and carbon emissions. However, it may require 8% of the customer demand to be flexible and available. Moreover, although energy storage is currently relatively expensive, it is likely to prevail over conventional generation by 2025 to 2030, when the capital cost of energy storage is projected to drop to approximately $ 400/kWh or lower.

  • 40.
    Yan, Jinyue
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. KTH-Royal Institute of Technology, Sweden.
    Wu, J.
    Tongji University, China.
    Yang, Ying
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Wang, H.
    Tongji University, China.
    Wang, X.
    Tongji University, China.
    Editorial cleaner energy for cleaner city2018In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 152, p. 1-2Article in journal (Refereed)
  • 41.
    Yu, J.
    et al.
    Xi'an Jiaotong University, Xi'an, China.
    Yang, Ying
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Yang, Xiaohu
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Xi'an Jiaotong University, Xi'an, China.
    Kong, Q.
    Xi'an Jiaotong University, Xi'an, China.
    Liu, Y.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Royal Institute of Technology (KTH), Stockholm, Sweden.
    Effect of porous media on the heat transfer enhancement for a thermal energy storage unit2018In: Energy Procedia, Elsevier Ltd , 2018, p. 984-989Conference paper (Refereed)
    Abstract [en]

    Thermal energy storage (TES) can effectively recover thermal energy from low-temperature waste heat and it has now been received increasing attentions in practical engineering applications. Nevertheless, the relatively low thermal conductivity of engineering available phase change materials (PCMs) greatly limits the energy efficiency of TES applications. To enhance the phase change process, open-cell metal foam with a porosity of 0.94 and pore density of 15 PPI (pore per inch) was employed to be inserted either in heat transfer fluid (HTF) or in phase change material (PCM). A two-dimensional axis-symmetric problem was numerically solved and was validated through comparing temperature history at selected points. Results demonstrated that the involvement of open-cell metal foam can effectively enhance the phase change heat transfer, greatly reducing the full melting time. By comparing the four cases (without metal foam, inserting metal foam into HTF, PCM and both domains), the case that both HTF and PCM domains were embedded with porous media can provide the best heat transfer enhancement, from which practical applications with thermal engineering may benefit. Copyright © 2018 Elsevier Ltd. All rights reserved.

  • 42.
    Aslanidou, Ioanna
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Rosic, Budimir
    University of Oxford, United Kingdom.
    Effect of the Combustor Wall on the Aerothermal Field of a Nozzle Guide Vane2018In: Journal of turbomachinery, ISSN 0889-504X, E-ISSN 1528-8900, Vol. 140, no 5, article id 051010Article in journal (Refereed)
    Abstract [en]

    In gas turbines with can combustors the trailing edge of the combustor transition duct wall is found upstream of ev- ery second vane. This paper presents an experimental and numerical investigation of the effect of the combustor wall trailing edge on the aerothermal performance of the nozzle guide vane. In the measurements carried out in a high speed experimental facility, the wake of this wall is shown to in- crease the aerodynamic loss of the vane. On the other hand, the wall alters secondary flow structures and has a protective effect on the heat transfer in the leading edge-endwall junc- tion, a critical region for component life. The different clock- ing positions of the vane relative to the combustor wall are tested experimentally and are shown to alter the aerothermal field. The experimental methods and processing techniques adopted in this work are used to highlight the differences be- tween the different cases studied. 

  • 43.
    Song, Jingjing
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Wallin, Fredrik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Effectiveness of introducing heat storage to repress cost increase2018Conference paper (Refereed)
    Abstract [en]

    District heating companies have been adapting their price models to reflect the changes in production cost caused by penetration of renewable fuels, and promote the applications of energy conservation measures that benefit the system efficiency. One of the approaches is to introduce a peak demand component in the price model, which has been proved to be effective to benefit users with lower peak demand. Whereas, this approach also significantly increase the cost for users with high peak demand. One of the measures that could help with high peak demand is installing energy storage on the demand side. In order to understand how the energy storage could change the users’ cost and help DH users to make informed decision, this study analyses the economic benefits of demand-side heat storage, namely if installing low-investment, low-tech, short-term hot-water storage on demand side could effectively repress the cost increase caused by new price models. Five types of building are considered here: multifamily house, commercial building, hospital and social services, industrial building, and office and school. One user of each type, whose costs increased the most during the price model transition process have been included. The result shows that heat storage could efficiently repress the cost increase, and all the investments will be paid back within 3 years, which means introducing heat storage is an efficient measure for cost saving under the circumstances.

  • 44.
    Dai, B.
    et al.
    Tianjin University of Commerce, Tianjin, China.
    Liu, S.
    Tianjin University of Commerce, Tianjin, China.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Tianjin University of Commerce, Tianjin, China.
    Sun, Z.
    Tianjin University of Commerce, Tianjin, China.
    Song, M.
    The University of Tokyo, Chiba, Japan.
    Yang, Q.
    Tianjin University of Commerce, Tianjin, China.
    Ma, Yitai
    The University of Tokyo, Chiba, Japan.
    Energetic performance of transcritical CO2 refrigeration cycles with mechanical subcooling using zeotropic mixture as refrigerant2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 150, p. 205-221Article in journal (Refereed)
    Abstract [en]

    Transcritical CO2 refrigeration cycle integrated with mechanical subcooling (MS) cycle operating with zeotropic mixture is proposed in this study, based on the concept of Lorenz cycle. An energetic model is developed and analyses are conducted in detail. A maximum overall coefficient of performance (COP) is achieved at the optimum discharge pressure and optimum subcooling degree. The maximum overall COP, optimum subcooling degree and discharge pressure are closely related to the temperature glide of the mixtures. The energy efficiency of the transcritical CO2 refrigeration cycle can be efficiently improved, and the high pressure can be reduced when mixtures with proper temperature glide are used as MS cycle refrigerant. Compared with pure R32, the overall COP is enhanced by 4.91%, and the discharge pressure decreases by 0.11 MPa at evaporation temperature of −5 °C and ambient temperature of 35 °C when R32/R1234ze(Z) (55/45) is employed as MS refrigerant. The mixtures with proper temperature glide are recommended. The thermal performance of the overall cycle can be enhanced more significantly for hot and warm climate regions, or relative low evaporation temperature applications, though a high subcooling degree is required to meet the optimum operation condition.

  • 45.
    Sylwan, Ida
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Zambrano, Jesus
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Energy demand for phosphorus recovery from municipal wastewater2018In: Innovative Solutions for Energy Transitions / [ed] Elsevier, 2018Conference paper (Refereed)
    Abstract [en]

    Phosphorus (P) is one of the essential nutrients for production of food. In modern agriculture, a large part of P comes from finite sources. There are several suggested processes for reuse of P from wastewater. In this paper, the energy use of direct reuse of sludge in agriculture is compared to the energy demand connected to use of mineral P and to reuse of P after thermal processing of sludge. The study is based on literature data from life cycle analysis (LCA). In the case of direct sludge reuse the sludge stabilization processes applied and the system boundaries of the LCA has a large impact on the calculated energy demand. The results though indicate that direct reuse of sludge in agriculture is the reuse scenario that potentially has the lowest energy demand (3-71 kWh/kg P), compared to incineration and extraction of P from sludge ashes (45-70 kWh/kg P) or pyrolysis of sludge (46-235 kWh/kg P). The competitiveness compared to mineral P (-4-22 kWh/kg P) depends on the mineral P source and production. For thermal processing, the energy demand derives mainly from energy needed to dry sludge and supplement fuel used during sludge incineration together with chemicals required to extract P. Local conditions, such as available waste heat for drying, can make one of these scenarios preferable.

  • 46.
    Zhang, Y.
    et al.
    KTH-Royal Institute of Technology, Stockholm, Sweden.
    Campana, Pietro Elia
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. KTH-Royal Institute of Technology, Stockholm, Sweden.
    Yang, Ying
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Stridh, Bengt
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Lundblad, A.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. RISE Research Institutes of Sweden, Borås, Sweden.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. KTH-Royal Institute of Technology, Stockholm, Sweden.
    Energy flexibility from the consumer: Integrating local electricity and heat supplies in a building2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 223, p. 430-442Article in journal (Refereed)
    Abstract [en]

    The increasing penetration level of renewable energy requires more flexibility measures to be implemented in future energy systems. Integrating an energy consumer’s local energy supplies connects multiple energy networks (i.e., the electrical grid, the district heating network, and gas network) in a decentralized way. Such integration enhances the flexibility of energy systems. In this work, a Swedish office building is investigated as a case study. Different components, including heat pump, electrical heater, battery and hot water storage tank are integrated into the electricity and heat supply system of the building. Special focus is placed on the flexibility that the studied building can provide to the electrical grid (i.e., the building modulates the electricity consumption in response to the grid operator’s requirements). The flexibility is described by two metrics including the flexibility hours and the flexibility energy. Optimization of the component capacities and the operation profiles is carried out by using Mixed Integer Linear Programming (MILP). The results show that the system fully relies on electricity for the heat demand when not considering the flexibility requirements of the electrical grid. This suggests that district heating is economically unfavorable compared with using electricity for the heat demand in the studied case. However, when flexibility requirements are added, the system turns to the district heating network for part of the heat demand. The system provides great flexibility to the electrical grid through such integration. The flexibility hours can be over 5200 h in a year, and the flexibility energy reaches more than 15.7 MWh (36% of the yearly electricity consumption). The yearly operation cost of the system slightly increases from 62,273 to 65,178 SEK when the flexibility hours increase from 304 to 5209 h. The results revealed that flexibility can be provided from the district heating network to the electrical grid via the building.

  • 47.
    Zhang, Yang
    et al.
    KTH Royal Institute of Technology, Stockholm, Sweden.
    Campana, Pietro Elia
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Yang, Ying
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Lundblad, Anders
    Division Safety and Transport/Electronics, RISE Research Institutes of Sweden, SE-50462 Borås, Sweden.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Energy Flexibility through the Integrated Energy Supply System in Buildings: A Case Study in Sweden2018In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 145, p. 564-569Article in journal (Refereed)
    Abstract [en]

    The increasing penetration level of renewable energies requires more flexibility measures at the consumption side. Flexible energy prices have been placed by energy providers to promote flexibility measures from energy users. However, because of the current energy supply system in buildings, these flexible energy prices haven’t been fully taken advantage of. This study focuses on the integrated energy supply system in buildings. A Swedish office building is used as the case study. The integrated energy supply system is built by installing new components, including battery, heat pump and electrical heater, and hot water tank. Mixed Integer Linear Programming (MILP) problems are solved to determine the optimal component capacities and operation profiles. The results indicate that all the studied system configurations achieve lower net present cost (NPC) than the current system. It suggests that the integrated energy supply system can take advantage of the flexible energy prices and lower the overall energy cost in the building. Among the studied configurations, the combination of air source heat pump (ASHP) and electrical heater (EH) has the lowest investment cost. This combination also has the lowest NPC except in the scenario with low borehole cost.

  • 48.
    Wang, Y.
    et al.
    Tianjin University of Commerce, Tianjin, China.
    Wang, B.
    Tianjin University of Commerce, Tianjin, China.
    Zhu, K.
    Tianjin University of Commerce, Tianjin, China.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Tianjin University of Commerce, Tianjin, China.
    He, W.
    Tianjin University of Commerce, Tianjin, China.
    Liu, S.
    Tianjin University of Commerce, Tianjin, China.
    Energy saving potential of using heat pipes for CPU cooling2018In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 143, p. 630-638Article in journal (Refereed)
    Abstract [en]

    Air cooling is the most common cooling solution for central processing units (CPUs). However, the heat dissipation capacity of conventional air-cooled heatsinks is limited because of non-uniform temperature distribution in the base of heatsinks. Embedded heat pipes into the heatsink is an effective method to improve the heat dissipation of the CPU and make the temperature distribution of the heatsink base more uniform. This work studied the cooling performance of the heat pipe embedded heatsinks, including the surface temperature, the average temperature of base, the thermal resistance and the power consumption. The impact of the different arrangements of heat pipes on the temperature distribution was also investigated. Results show that to obtain the same CPU temperature, a lower air velocity was needed for the heatsink with embedded heat pipe at the same heat flux. The minimum thermal resistance of the studied heat pipe embedded heatsinks was 0.15 °C/W, which is lower than that of the reference conventional heatsink, 0.22 °C/W. In addition, the heatsink with H-shape arrangement of embedded heat pipes had the best overall performance, which cooling capacity was increased by 22.5% and the weight of the heatsink was reduced by 30.1% compared with the heatsink without heat pipes. The energy saving potential was also evaluated based on the measured real operating status of CPUs. The dynamic simulation results show that the total fan power consumption can be effectively reduced when using a heat pipe embedded heatsink to replace the conventional heatsink, which can be up to 66.2%. 

  • 49.
    Xu, J.
    et al.
    Tongji University, Shanghai, China.
    Luo, P.
    Tongji University, Shanghai, China.
    Lu, B.
    Tongji University, Shanghai, China.
    Wang, H.
    Tongji University, Shanghai, China.
    Wang, X.
    Tongji University, Shanghai, China.
    Wu, J.
    Tongji University, Shanghai, China.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Royal Institute of Technology, Sweden.
    Energy-water nexus analysis of wastewater treatment plants (WWTPs) in China based on statistical methodologies2018In: Energy Procedia, Elsevier Ltd , 2018, p. 259-264Conference paper (Refereed)
    Abstract [en]

    Wastewater treatment plants (WWTPs) are considered as energy-intensive facilities. Against the background of stricter policy requirements and discharge standard, thousands of municipal WWTPs are experiencing upgrading and reconstruction in China. However, the accompanying energy consumption cannot be ignored. Based on the statistical analysis of energy consumption and relevant factors from data of more than six thousand WWTPs over China, in this paper we analyzed the most influential factors related to energy consumption, which include treatment technology, wastewater amount, removed pollutants, social and economic characteristics, etc. Furthermore, we set up systematic method of energy performance assessment for WWTPs and explored the potential of energy saving in WWTPs. Results showed that processing capacity, organic pollutant concentration, discharge standard and economic factors have major effects on energy efficiency. Although sludge treatment and disposal normally consume intensive energy, it is possible to recover energy from biomass in the sludge. The results indicate that there is huge potential for energy saving and recovery in WWTPs, and we propose a conceptual roadmap for energy efficiency improving in WWTPs in China.

  • 50.
    Bürger, Raimund
    et al.
    Universidad de Concepción, Concepción, Chile.
    Careaga, Julio
    Lund University, Sweden.
    Diehl, Stefan
    Lund University, Sweden.
    Merckel, Ryan
    University of Pretoria, South Africa.
    Zambrano, Jesús
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Estimating the hindered-settling flux function from a batch test in a cone2018In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 192, p. 244-253Article in journal (Refereed)
    Abstract [en]

    The hindered-settling velocity function for the modelling, simulation and control of secondary settling tanks can be determined from batch tests. The conventional method is to measure the velocity of the descending sludge-supernatant interface (sludge blanket) as the change in height over time in a vessel with constant cross-sectional area. Each such experiment provides one point on the flux curve since, under idealizing assumptions (monodisperse suspension, no wall-effects), the concentration of sludge remains constant just below the sludge blanket until some wave from the bottom reaches it. A newly developed method of estimation, based on the theory of nonlinear hyperbolic partial differential equations, is applied to both synthetic and experimental data. The method demonstrates that a substantial portion of the flux function may be estimated from a single batch test in a conical vessel. The new method takes into consideration that during an ideal settling experiment in a cone, the concentration just below the sludge blanket increases with time since the mass of suspended solids occupy a reduced volume over time.

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