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  • 901.
    Zhang, Y.
    et al.
    KTH Royal Institute of Technology, Stockholm, Sweden.
    Lundblad, Anders
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. KTH Royal Institute of Technology, Stockholm, Sweden.
    Campana, Pietro Elia
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. KTH Royal Institute of Technology, Stockholm, Sweden.
    Employing battery storage to increase photovoltaic self-sufficiency in a residential building of Sweden2016In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 88, p. 455-461Article in journal (Refereed)
    Abstract [en]

    Photovoltaic (PV) or hybrid PV-battery systems are promising to supply power for residential buildings. In this study, the load profile of a multi apartment building in Gothenburg and the PV production profile under local weather conditions are compared and analyzed. Three different types of batteries, including lead acid, NaNiCl (Sodium-Nickel-Chloride) and Lithium ion, are studied in combination with the PV systems. It is found that Lithium ion battery system is superior in achieving higher Self-Sufficiency Ratio (SSR) with the same Life Cycle Cost (LCC). Achieving high SSR with the hybrid PV-battery system is unrealistic because of the seasonal mismatch between the load and electricity production profile. The capacity match between the PV and battery to maximize SSR was investigated, showing different trends under system LCC range of 0.1-40 Million SEK (1SEK≈0.12USD). The system LCC should be lower than 10.6 Million SEK (at the SSR of 36%) in order to keep the payback time positive. 

  • 902. Zhang, Y.
    et al.
    Ma, T.
    Campana, Pietro Elia
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Yamaguchi, Y.
    Dai, Y.
    A techno-economic sizing method for grid-connected household photovoltaic battery systems2020In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 269, article id 115106Article in journal (Refereed)
    Abstract [en]

    Battery storage provides an effective solution to alleviate the burden of the intermittent photovoltaic production on the grid and increase photovoltaic penetration in residential houses. Despite several existing work dedicated to the evaluation of photovoltaic battery system, the research on system sizing and operation strategy of the household system still has substantial areas to be explored such as techno-economic analysis under different electricity tariffs and comprehensive parametric analyses. In this paper, the mathematical model of a photovoltaic battery system is developed to investigate system performance, based on the various economic and technical indicators. This study demonstrates that the integration of battery energy storage could increase the value of self-consumption and self-sufficiency rates while making payback period longer. Substantial photovoltaic battery systems have been simulated under practical dynamic electricity tariffs in a typical electricity market. Eight cases with different technical performances from the recommended reference combinations are compared and studied in detail. The energy flows among photovoltaic, battery bank, grid and household user are discussed, revealing that systems with high self-sufficiency rate lead to more schedulable photovoltaic production, sold electricity and lower battery usage rate than those with high self-consumption rate. Besides, the entire lifecycle economic analysis indicates that a higher self-sufficiency rate refers to higher initial investment but shorter payback period and larger profit. The revenues breakdown of the cases shows that subsidies have a significant impact, especially for cases with high self-sufficiency rate. The levelized cost of electricity of photovoltaic and photovoltaic battery systems ranges from 0.373 to 0.628 CNY/kWh, demonstrating the possibility of partial grid parity under the current situation in Shanghai. © 2020 Elsevier Ltd

  • 903.
    Zhang, Yang
    et al.
    KTH Royal Inst Technol, Sweden.
    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.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. KTH Royal Inst Technol, Sweden.
    Comparative study of hydrogen storage and battery storage in grid connected photovoltaic system: Storage sizing and rule-based operation2017In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 201, p. 397-411Article in journal (Refereed)
    Abstract [en]

    The paper studies grid-connected photovoltaic (PV)-hydrogen/battery systems. The storage component capacities and the rule-based operation strategy parameters are simultaneously optimized by the Genetic Algorithm. Three operation strategies for the hydrogen storage, namely conventional operation strategy, peak shaving strategy and hybrid operation strategy, are compared under two scenarios based on the pessimistic and optimistic costs. The results indicate that the hybrid operation strategy, which combines the conventional operation strategy and the peak shaving strategy, is advantageous in achieving higher Net Present Value (NPV) and Self Sufficiency Ratio (SSR). Hydrogen storage is further compared with battery storage. Under the pessimistic cost scenario, hydrogen storage results in poorer performance in both SSR and NPV. While under the optimistic cost scenario, hydrogen storage achieves higher NPV. Moreover, when taking into account the grid power fluctuation, hydrogen storage achieves better performance in all three optimization objectives, which are NPV, SSR and GI (Grid Indicator). 

  • 904. 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)
  • 905.
    Zhang, Yang
    et al.
    KTH Royal Inst Technol, Div Energy Proc, SE-10044 Stockholm, Sweden..
    Campana, Pietro Elia
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. KTH Royal Inst Technol, Div Energy Proc, SE-10044 Stockholm, Sweden.; Malardalen Univ, Sch Business Soc & Engn, SE-72123 Vasteras, Sweden..
    Lundblad, Anders
    RISE Res Inst Sweden, Div Safety & Transport Elect, SE-50462 Boras, Sweden..
    Zheng, Wandong
    Tianjin Univ, Sch Environm Sci & Technol, Tianjin 300072, Peoples R China..
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. KTH Royal Inst Technol, Div Energy Proc, SE-10044 Stockholm, Sweden.; Malardalen Univ, Sch Business Soc & Engn, SE-72123 Vasteras, Sweden..
    Planning and operation of an integrated energy system in a Swedish building2019In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 199, article id 111920Article in journal (Refereed)
    Abstract [en]

    More flexibility measures are required due to the increasing capacities of variable renewable energies (VRE). In buildings, the integration of energy supplies forms integrated energy systems (IES). IESs can provide flexibility and increase the VRE penetration level. To upgrade a current building energy system into an IES, several energy conversion and storage components are needed. How to decide the component capacities and operate the IES were investigated separately in studies on system planning and system operation. However, a research gap exists that the system configuration from system planning is not validated by actual operation conditions in system operation. Meanwhile, studies on system operation assume that IES configurations are predetermined. This work combines system planning and system operation. The IES configuration is determined by mixed integer linear programming in system planning. Actual operation conditions and forecast errors are considered in system operation. The actual operation profiles are obtained through year-round simulations of different energy management systems. The results indicate that the system configuration from system planning can meet energy demands in system operation. Among different energy management systems, the combination of robust optimization and receding horizon optimization achieves the lowest yearly operation cost. Meanwhile, two scenarios that represent high and low forecast accuracies are studied. Under the high and low forecast accuracy scenarios, the yearly operation costs are about 4% and 6% higher than that obtained from system planning.

  • 906.
    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.

  • 907.
    Zhanga, C.
    et al.
    Royal Institute of Technology, Stockholm, Sweden.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Business model innovation on the photovoltaic water pumping systems for grassland and farmland conservation in China2014In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 61, p. 1483-1486Article in journal (Refereed)
    Abstract [en]

    Penetration of the renewable market of Photovoltaic PV technologies calls for the extension of the additional values generated from the technology including climate and social co-benefits as radical innovations in a new business model. Compared with existing PV business models, this paper extends the value proposition into operation system and customer segmentation, investigated by a pilot demonstration of PV water pumping (PVWP) systems for the conservation of grassland and farmland in China. The paper suggests that the integrated PVWP systems can combine the implementation of technology with environmental co-benefits, agricultural products by developing an interactive interface to link a social network. This can further disseminate benefits to stimulate the active participations of investments from individuals and corporations. Discounted cash flow (DCF) model and net present value (NPV) evaluations have been conducted on the traditional PV roof, PVWP pilot and PVWP scale up scenarios. The results show that the scenario of integrated PVWP system with social network products can significantly improve the payback period (PP) and increase internal rate of return (IRR). Based on the PVWP pilots and relevant industrial environments, the results in this paper provide how the innovative PV business model innovation can improve the present practices and policies on PV technologies implementation.

  • 908.
    Zhao, R.
    et al.
    Ministry of Education of China, Tianjin, China.
    Deng, S.
    Ministry of Education of China, Tianjin, China.
    Wang, S.
    Tianjin University, Tianjin, China.
    Zhao, L.
    Ministry of Education of China, Tianjin, China.
    Zhang, Y.
    Ministry of Education of China, Tianjin, China.
    Liu, B.
    Ministry of Education of China, Tianjin, China.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Yu, Z.
    University of Stavanger, Stavanger, Norway.
    Thermodynamic research of adsorbent materials on energy efficiency of vacuum-pressure swing adsorption cycle for CO2 capture2018In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 128, p. 818-829Article in journal (Refereed)
    Abstract [en]

    This paper presents a comprehensive thermodynamic research on energy efficiency of vacuum-pressure swing adsorption (VPSA). The study examined the influence from four types of typical adsorbent materials on the energy efficiency of VPSA by cycle parameters. The selected adsorbent materials are activated carbons, zeolite 5A, zeolite 13X, silica gels, and metal-organic frameworks (MOFs). The study also analyzes the effects of separation temperature, adsorption pressure, desorption pressure, CO2 concentration and percent of unused bed on the energy-efficiency of VPSA cycle. The examined performance parameters are CO2 working capacity, proportionality factor, energy consumption and second-law efficiency. The results show that the energy consumption is approximately 2.0–4.5 MJ/kg and the second-law efficiencies are 4–7% for VPSA cycles using the five adsorbent materials. The effect of adsorbent materials on the energy efficiency mainly depends on the proportionality factor of CO2 working capacity (β) of VPSA cycle, which is important to screen materials at the fixed cyclic boundary conditions and preliminary calculation of second-law efficiency for VPSA cycles. For existing adsorbent materials which are Type I commonly, the lower values of β would lead to the higher second-law efficiencies. The development of new adsorbents of Type III would be extremely urgent in near future. 

  • 909.
    Zhao, R.
    et al.
    KTH Royal Institute of Technology, Stockholm, Sweden.
    Liu, L.
    KTH Royal Institute of Technology, Stockholm, Sweden.
    Zhao, L.
    Ministry of Education of China, Tianjin, China.
    Deng, S.
    Ministry of Education of China, Tianjin, China.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thermodynamic analysis on carbon dioxide capture by Electric Swing Adsorption (ESA) technology2018In: Journal of CO2 Utilization, ISSN 2212-9820, E-ISSN 2212-9839, Vol. 26, p. 388-396Article in journal (Refereed)
    Abstract [en]

    This study explores the impacts of materials, such as adsorbents and electrodes, on the energy efficiency of a 4-step ESA cycle for CO2 capture. Three types of adsorbents including activated carbon honeycomb monolith (ACHM) and two hybrid adsorbents are compared, and two kinds of electrodes such as aluminum and brass are combined for comparative analysis. Process description of ESA cycle, including feed, electrification, electrification with purge and cooling, is presented via the adsorption isotherm diagram. By the theory of thermodynamic carbon pump, sensitivity analysis of cycle parameters is evaluated in terms of the second-law efficiency (Eff2nd) and the electrical heating efficiency (Effele). The results show that Eff2nd of the employed adsorbents is in the range of 1.17%-6.15%, and Effele of the selected electrodes is between 27.46% and 60.91%. Among the three adsorbents, Eff2nd of ACHM is the lowest one compared to the others. Similarly, Effele of the combination with brass is superior to that of the groups with aluminum. However, the actual efficiency of ESA cycle is the production of both Eff2nd and Effele, which is approximately 1.03%-3.66%. Typical measures are proposed to reduce the heat loss of the adsorbents and electrodes as well for future work. 

  • 910.
    Zhao, R.
    et al.
    Royal Institute of Technology, Sweden.
    Liu, L.
    Royal Institute of Technology, Sweden.
    Zhao, L.
    Tianjin University, Ministry of Education, China.
    Deng, S.
    Tianjin University, Ministry of Education, China.
    Li, S.
    Tianjin University, Ministry of Education, China.
    Zhang, Y.
    Tianjin University, Ministry of Education, China.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Techno-economic analysis of carbon capture from a coal-fired power plant integrating solar-assisted pressure-temperature swing adsorption (PTSA)2019In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 214, p. 440-451Article in journal (Refereed)
    Abstract [en]

    This paper presents a techno-economic study to seek the feasibility about the proposed system that integrating solar-assisted pressure-temperature swing adsorption (PTSA) into an 800MWe coal-fired power plant. Solar energy has the potential to supply thermal energy demand for carbon capture, which can avoid the energy consumption of the traditional method such as the steam extraction. The performance of the proposed system is largely affected by the climatic conditions and solar collector's types. The assessment criteria include carbon emission intensity (CEI), levelized cost of electricity (LCOE) and cost of CO2 avoidance (COA). By the parametric analysis, the results show that CEI of the novel system with solar thermal collectors is approximately 2g/kWh lower than that of the referenced power plant with CO2 adsorption capture. In addition, CEI of the novel system can be further decrease with the decline of desorption temperature, adsorption pressure and desorption pressure. For the sake of lower LCOE and COA, the prices of the power plant capacity, adsorbents and solar collectors should be reduced. Specifically, LCOE of the system with evacuated tube collector will be lower than that of the reference system with CO2 capture as the price of solar field is lower than 46.08 USD/m2.

  • 911.
    Zhao, R.
    et al.
    KTH Royal Institute of Technology, Stockholm, Sweden.
    Liu, L.
    KTH Royal Institute of Technology, Stockholm, Sweden.
    Zhao, L.
    Ministry of Education of China, Tianjin, China.
    Deng, S.
    Ministry of Education of China, Tianjin, China.
    Li, S.
    Ministry of Education of China, Tianjin, China.
    Zhang, Y.
    Ministry of Education of China, Tianjin, China.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thermodynamic exploration of temperature vacuum swing adsorption for direct air capture of carbon dioxide in buildings2019In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 183, p. 418-426Article in journal (Refereed)
    Abstract [en]

    Abrupt climate change such as the loss of Arctic sea-ice area urgently needs negative emissions technologies. The potential application of direct air capture of carbon dioxide from indoor air and outdoor air in closed buildings or crowded places has been discussed in this paper. From the aspects of carbon reduction and indoor comfort, the ventilation system integrating a capture device is of great value in practical use. For ultra-dilute carbon dioxide sources, many traditional separation processes have no cost advantages, but adsorption technologies such as temperature vacuum swing adsorption is one of suitable methods. Thermodynamic exploration has been investigated regarding minimum separation work and second-law efficiency at various concentrations in the air. The influence of concentration, adsorption temperature, desorption temperature and desorption pressure on the energy efficiency has also been evaluated. Results show that the minimum separation work for the level of 400 ppm is approximately 20 kJ/mol. The optimal second-law efficiencies are 44.57%, 37.55% and 31.60%, respectively for 3000 ppm, 2000 ppm and 1000 ppm. It means that a high energy-efficiency capture device in buildings merits attention in the exploration of the possibility of approaching negative carbon buildings. 

  • 912.
    Zhao, R.
    et al.
    Ministry of Education of China, Tianjin, China.
    Zhao, L.
    Ministry of Education of China, Tianjin, China.
    Wang, S.
    Tianjin University, Tianjin, China.
    Deng, S.
    Ministry of Education of China, Tianjin, China.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Yu, Z.
    University of Stavanger, Stavanger, Norway.
    Solar-assisted pressure-temperature swing adsorption for CO2 capture: Effect of adsorbent materials2018In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 185, p. 494-504Article in journal (Refereed)
    Abstract [en]

    Because of the ability to utilize the low-grade solar thermal energy for regeneration, a CO2 capture system characterized by solar-assisted pressure temperature swing adsorption (SOL-PTSA) is studied on the effects of adsorbent materials. A detailed cycle description is firstly presented within the diagram of adsorption isotherm for the energy-efficiency analysis. Typical adsorbent materials, including zeolites and chemical adsorbent, are assessed in terms of sensible heat and latent heat, etc. Then, the energy consumption and the second-law efficiency, which can be considered as lumped indicators from such material parameters, are chosen as performance indicators as well. The influence of separation temperature, desorption temperature, CO2 concentration and CO2 adsorption pressure on system performance are finally obtained. For the chosen three adsorbent materials, the energy consumption of SOL-PTSA system is at the range of 25.96–87.76 kJ/mol, and the corresponding second-law efficiencies are at the range of 9.18–26.89%. The effect of adsorbent materials on the energy-efficiency of SOL-PTSA system mainly depends on specific heat, CO2 working capacity and cycle design. In addition, the integration options of solar energy into PTSA technology are also discussed from the standpoint of the utilization of solar grade heat due to two energy loads required for PTSA's operation.

  • 913.
    Zheng, W.
    et al.
    Tianjin University, Tianjin, China.
    Hennessy, Jay
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. RISE Research Institutes of Sweden, Borås, Sweden.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Reducing renewable power curtailment and CO2 emissions in China through district heating storage2020In: Wiley Interdisciplinary Reviews: Energy and Environment, ISSN 2041-8396, E-ISSN 2041-840X, Vol. 9, no 1, article id e361Article in journal (Refereed)
    Abstract [en]

    Emissions reductions are often achieved through the increased share of renewable energy sources (RES) and China is the leader in the growth of RES in the power sector. This growth has led to high levels of curtailment of RES power due to insufficient reinforcement of the electricity grid to support such growth and due to competition with other power sources. Although the problem of curtailment has been alleviated in recent years, large amounts of power are still discarded, and it is important to consider how to address this problem in the short term and how much CO2e emissions could be avoided as a result. The use of district heating systems to reduce the curtailment of renewable power has seen increasing interest in recent years. Based on a review of potential energy storage in district heating, the current paper assesses the capability to use the national storage potential of district heating systems in China to reduce curtailment and to determine what effects that may have on avoiding CO2e emissions. The distribution networks and the thermal inertia of buildings connected to district heating are considered as two major forms of storage that can be “charged” using power that would otherwise be curtailed. The results show that there may be sufficient storage available to absorb all renewable power that is currently curtailed in those provinces using district heating during the heating season, resulting in avoided emissions of up to 14 MtCO2e/annum. This article is categorized under: Energy and Climate > Economics and Policy Wind Power > Climate and Environment Energy Infrastructure > Climate and Environment Energy and Urban Design > Climate and Environment.

  • 914.
    Zhu, C.
    et al.
    Building Energy Research Center, Department of Building Science, Tsinghua University, Beijing, China; Oak Ridge National Laboratory, Building Equipment Research, Energy & Transportation Science Division, Oak Ridge, United States.
    Gluesenkamp, K. R.
    Oak Ridge National Laboratory, Building Equipment Research, Energy & Transportation Science Division, Oak Ridge, United States.
    Yang, Z.
    Lyle School of Civil Engineering, Purdue University, West Lafayette, United States.
    Blackman, Corey
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. SaltX Technology AB, Stockholm, Sweden; Dalarna University, Borlänge, Sweden.
    Unified thermodynamic model to calculate COP of diverse sorption heat pump cycles: Adsorption, absorption, resorption, and multistep crystalline reactions2019In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 99, p. 382-392Article in journal (Refereed)
    Abstract [en]

    A straightforward thermodynamic model is developed in this work to analyze the efficiency limit of diverse sorption systems. A method is presented to quantify the dead thermal mass of heat exchangers. Solid and liquid sorbents based on chemisorption or physical adsorption are accommodated. Four possible single-effect configurations are considered: basic absorption or adsorption (separate desorber, absorber, condenser, and evaporator); separate condenser/evaporator (two identical sorbent-containing reactors with a condenser and a separate direct expansion evaporator); combined condenser/evaporator (one salt-containing reactor with a combined condenser/evaporator module); and resorption (two sorbent-containing reactors, each with a different sorbent). The analytical model was verified against an empirical heat and mass transfer model derived from component experimental results. It was then used to evaluate and determine the optimal design for an ammoniate salt-based solid/gas sorption heat pump for a space heating application. The effects on system performance were evaluated with respect to different working pairs, dead thermal mass factors, and system operating temperatures. The effect of reactor dead mass as well as heat recovery on system performance was also studied for each configuration. Based on the analysis in this work, an ammonia resorption cycle using LiCl/NaBr as the working pair was found to be the most suitable single-effect cycle for space heating applications. The maximum cycle heating coefficient of performance for the design conditions was 1.50 with 50% heat recovery and 1.34 without heat recovery. 

  • 915.
    Zhu, K.
    et al.
    Tianjin University of Commerce, China.
    Cui, Z.
    Tianjin University of Commerce, China.
    Wang, Y.
    Tianjin University of Commerce, China.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Tianjin University of Commerce, China.
    Zhang, X.
    ABB Corporate Research, Sweden.
    Franke, C.
    Estimating the maximum energy-saving potential based on IT load and IT load shifting2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 138, p. 902-909Article in journal (Refereed)
    Abstract [en]

    Cooling system consumes more than 35% of total electricity in most data centers. The provided cooling normally exceeds the actual demand of IT equipment in order to assure the safe operation, resulting in a low energy efficiency. In this paper, a novel method based on demand response was proposed to precisely control the cooling supply, and the energy saving potential was assessed systematically. Compared to the reference case, in which the cooling demand is determined by assuming all of servers are in the running status, when the cooling demand was determined based on the measured dynamic IT load at room level, row level, rack level and server level, it can be reduced by 7.9%, 14.2%, 15.6% and 17.9% respectively for the random selected 48 h. In addition, IT load shifting also has a big potential to save energy, as it can make the cooling system working at a higher energy efficiency, which varies with loads. Two cases were studied: even distribution of IT load and optimized IT load shifting. Compared to the best case that determines the cooling demand according to the IT load at server level, they can further reduce the electricity consumption of cooling systems by 0.9%, and 1.2%. 

  • 916.
    Zhu, K.
    et al.
    Tianjin Key Laboratory of Refrigeration technology, Tianjin University of Commerce, Tianjin 300134, China.
    Li, X.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Tianjin Key Laboratory of Refrigeration technology, Tianjin University of Commerce, Tianjin 300134, China.
    Chen, X.
    Tianjin Key Laboratory of Refrigeration technology, Tianjin University of Commerce, Tianjin 300134, China.
    Wang, Y.
    Tianjin Key Laboratory of Refrigeration technology, Tianjin University of Commerce, Tianjin 300134, China.
    Optimization of a loop heat pipe (LHP) with wick separated from heating surface2019In: Energy Procedia, Elsevier Ltd , 2019, Vol. 158, p. 2409-2416Conference paper (Refereed)
    Abstract [en]

    A novel LHP, in which the wick is separated from the heating surface, has been proposed. And then, a steam chamber is formed, which can effectively use the pressure head of evaporation. This work is to optimize the key parameters in order to further improve the performance of such a novel LHP. A mathematical model, based on the node analysis method, had been established, which was validated against the experimental data. The height of steam chamber, the type of working fluids, and the material of wick were identified as key parameters to be optimized. The heating surface temperature, which was the highest temperature, and the start-up time were selected as the key performance indicators. Results showed there existed an optimal height of steam chamber (3mm) and charging ratio (55%) to achieve the lowest heating surface temperature and the shortest start-up time. For different working fluids, ammonia showed the best performance, followed by acetone, ethanol, and water. And the ceramic wick, with low thermal conductivity, demonstrated a better performance than the steel-nickel wick and copper wick with high thermal conductivity.

  • 917.
    Zhu, K.
    et al.
    Tianjin Key Laboratory of Refrigeration technology, Tianjin University of Commerce, Tianjin 300134, China.
    Li, X.
    Tianjin Key Laboratory of Refrigeration technology, Tianjin University of Commerce, Tianjin 300134, China.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Tianjin Key Laboratory of Refrigeration technology, Tianjin University of Commerce, Tianjin 300134, China.
    Yang, Z.
    Tianjin Key Laboratory of Refrigeration technology, Tianjin University of Commerce, Tianjin 300134, China.
    Wang, Y.
    Tianjin Key Laboratory of Refrigeration technology, Tianjin University of Commerce, Tianjin 300134, China.
    Experimental investigation on the effect of heat sink temperature on operational characteristics of a new-type loop heat pipe2019In: Energy Procedia, Elsevier Ltd , 2019, Vol. 158, p. 2423-2429Conference paper (Refereed)
    Abstract [en]

    With the development of the miniaturization and the high integration of electronic chip, the thermal management of the high power electronic becomes a major challenge. In this paper the influence of heat sink temperature on operational characteristics was comprehensively conducted and the 35% of charging ratio was selected through the experiment study. To evaluate the LHP system, temperatures, start-up time, thermal resistance, and evaporator heat transfer coefficient were selected as performance indicators. The result showed that, there existed an optimal heat sink temperature (18 o C) to obtain the lowest evaporator bottom temperature (77 o C), the shortest start-up time (1000s), the smallest thermal resistance (0.29k/W), and the highest evaporator heat transfer coefficient (3.110 4 W/(m 2 ·k)). The temperature range to keep a high performance of LHP system was 14-20 o C. The conclusion obtained through the experiment can provide the reference of design the cooling system when the LHP system applied into the electric cooling.

  • 918.
    Zhu, K.
    et al.
    Tianjin University of Commerce, Tianjin, China.
    Li, X.
    Tianjin University of Commerce, Tianjin, China.
    Wang, Y.
    Tianjin University of Commerce, Tianjin, China.
    Chen, X.
    Tianjin University of Commerce, Tianjin, China.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dynamic performance of loop heat pipes for cooling of electronics2017In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 142, p. 4163-4168Article in journal (Refereed)
    Abstract [en]

    With the performance improvement of electronics, the recent trends in electronic industry pose a big challenge on heat dissipation. Conventional methods, i.e. air cooling, may not be able to handle the fast increasing heat flux. Using heat pipes, which have numerous advantages such as high heat transfer coefficient, non-movable components, longer transport distance, and compact structures, emerges to be one competitive option for electronics cooling. Based on the node analysis method and the conservation of energy and mass, this work develops a mathematic model to simulate the operation of heat pipes. After it is validated against experimental data, it is further applied to evaluate the dynamic performance of using a heat pipe for electronics cooling. Results show that the operation temperature of evaporator ranges from 47.5°C to73.1°C, which implies that the heat pipe can effectively cool down the CPU at different running status. The charging ratio of working fluid is identified as a key parameter and exists an optimal value. When keeping the charging ratio constant, a larger evaporator area can achieve a lower operating temperature. 

  • 919.
    Zhu, K.
    et al.
    Tianjin Key Laboratory of Refrigeration Technology, Tianjin University of Commerce, Tianjin, China.
    Li, Xueqiang
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. School of Environmental Science and Engineering, Tianjin University, Tianjin, China.
    Campana, Pietro Elia
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. School of Chemical Science & Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    Techno-economic feasibility of integrating energy storage systems in refrigerated warehouses2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 216, p. 348-357Article in journal (Refereed)
    Abstract [en]

    This work evaluates the techno-economic feasibility of integrating the cold energy storage system and the electrical energy storage system in a refrigerated warehouse for shifting the power consumption. A dynamic model has been developed in TRNSYS®. Based on the dynamic simulation, the performance and benefit of those two types of energy storage systems were compared. Results showed that, the integration of a cold energy storage can reduce the electricity consumption and operational cost by 4.3% and 20.5%, respectively. Even though integrating a battery system will increase the electricity consumption by 3.9%, it can reduce the operational cost by 18.7%. The capacity of the energy storage systems, the battery price and the peak electricity price had been identified as key parameters affecting the performance and benefit. To achieve a payback period less than 3 year, for the integration of a cold energy storage system, the peak electricity price should be increased by 25% from the current level, while for the integration of a battery system, the battery price should drop to 0.7 kRMB/kWh.

  • 920.
    Zhu, K.
    et al.
    Key Laboratory of Refrigeration Technology of Tianjin, Tianjin University of Commerce, Tianjin, China.
    Li, Xueqiang
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Key Laboratory of Refrigeration Technology of Tianjin, Tianjin University of Commerce, 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.
    Experimental and theoretical study of a novel loop heat pipe2018In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 130, p. 354-362Article in journal (Refereed)
    Abstract [en]

    In order to reduce the heat leakage from the evaporator and achieve a longer transport distance, a new type of loop heat pipe (LHP) has been proposed based on a hypothesis that the circulation of working fluids is driven by not only the capillary head, but also the pressure head due to evaporation. In the evaporator, the wick is separated from the heating surface by a chamber, which can effectively use the pressure head generated by evaporation. In this work, a prototype of such a LHP was studied experimentally and theoretically. In order to understand the mechanism of operation, a new mathematical model was established. Comparing the simulated results with the experimental data about the operation temperature, a good agreement was observed that the average absolute deviation and the maximum absolute deviation were in ranges of 0.67–1.21 °C and −1.3 to 6 °C, respectively. With the validated model, the two driving forces were investigated. Results showed that the ratio of the pressure head of evaporation to the capillary head was in a range of 59–54% corresponding to heating powers from 30 W to 110 W. It confirms that the pressure head due to evaporation plays an important role in the circulation of working fluids.

  • 921.
    Zhu, Kai
    et al.
    Tianjin University of Commerce, Tianjin, China .
    Chen, Xiaoqing
    Tianjin University of Commerce, Tianjin, China .
    Dai, Baomin
    Tianjin University of Commerce, Tianjin, China .
    Zheng, Mingzhu
    Tianjin University of Commerce, Tianjin, China .
    Wang, Yabo
    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 .
    Operation characteristics of a new-type loop heat pipe (LHP) with wick separated from heating surface in the evaporator2017In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 123, p. 1034-1041Article in journal (Refereed)
    Abstract [en]

    The loop heat pipe (LHP) has been widely used for cooling devices with high heat flux. In addition to the capillary pumping force, the pressure head due to evaporation has been assumed to play an important role in the circulation of working fluid. Based on such a hypothesis, a new LHP is designed, in which the wick is separated from the heating surface in the evaporator. Experiments show that such a LHP can start up successfully and reach steady operation, which indirectly verified the hypothesis. The influences of heating power, height of steam chamber, pore radius and porosity of wick are comprehensively investigated. The results show that the start-up time of the new-designed LHP is shorter and the temperature fluctuation is smaller at higher heating power. The steam chamber height has clear impacts on the start-up time and the thermal resistance. The start-up time with the steam chamber height of 2 mm is shorter than that of 3 mm, but the thermal resistance is relatively higher. Moreover, a larger pore radius and a higher porosity of the wick can lead to a shorter start-up time and a smaller thermal resistance of the new LHP.

  • 922.
    Zhu, Z. -S
    et al.
    Beijing Institute of Technology.
    Liao, H.
    Beijing Institute of Technology.
    Cao, H. -S
    Beijing Institute of Technology.
    Wang, L.
    Beijing Institute of Technology.
    Wei, Y. -M
    Beijing Institute of Technology.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    The differences of carbon intensity reduction rate across 89 countries in recent three decades2014In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 113, p. 808-815Article in journal (Refereed)
    Abstract [en]

    In the recent decades, most countries' CO2 intensity has decreased, but their decline rates are significantly different. Based on the data set of 89 countries from 1980 to 2008, this paper tries to quantitatively investigate the potential reasons for their differences, and discusses the possibility for developing countries to maintain a high carbon intensity reduction rate in the future as before. The econometric analysis implicate that (1) the decline rate of CO2 intensity in countries with high initial carbon intensity will be higher, which means CO2 intensity across the world has a significant convergence trend; and (2) keeping fast and steady economic growth can significantly help CO2 intensity decline, yet total carbon dioxide emissions will grow dramatically. Therefore, with the two objectives of intensity reduction and total amount control, carbon abatement policies need to weigh one against another. The results are robust to the initial year selection and country classification.

  • 923.
    Zimmerman, Nathan
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Vanadium Redox Flow Battery: Sizing of VRB in electrified heavy construction equipment2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In an effort to reduce global emissions by electrifying vehicles and machines with internal combustion engines has led to the development of batteries that are more powerful and efficient than the common lead acid battery.  One of the most popular batteries being used for such an installation is lithium ion, but due to its short effective usable lifetime, charging time, and costs has driven researcher to other technologies to replace it.  Vanadium redox flow batteries have come into the spotlight recently as a means of replacing rechargeable batteries in electric vehicles and has previously be used mainly to store energy for load leveling.  It possesses many qualities that would be beneficial to electrify vehicles.  The battery has the ability for power and energy to be sized independently which is not dissimilar to internal combustion vehicles.  It also has the potential for a tolerance to low discharges, fast response time, and can quickly be refueled by replacing the electrolyte; just like is done when a car refuels at the gas station. 

    The purpose of the study is to determine the possibility of using vanadium redox flow batteries to power heavy construction equipment, a wheel loader, with a finite amount of space available for implementation.  A model has been designed in MATLAB to determine how long the battery could last under typically applications for the wheel loader which needs a peak power of 200 kW.  From the volume available it has been determined that the battery can be installed with an energy capacity of 148 kWh.  The results of the model show that vanadium redox flow batteries can be used to power a wheel loader but due to the limiting energy density and cell components it remains to be impractical.

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  • 924.
    Zimmerman, Nathan
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Kyprianidis, Konstantinos
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Towards On-line Fault Detection and Diagnostics in District Heating Systems2017In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 105, p. 1960-1966Article in journal (Refereed)
    Abstract [en]

    This paper gives a brief introduction for detecting faults in pressure sensors and diagnostics in a district heating network.  Proper pressure throughout the network is essential in maintaining the requirements for the end-user.  A district heating network library has been constructed in OpenModelica for the purpose of developing a district heating network representation of Skultuna, Sweden.  The use of object-oriented program will give the ease of expanding the network to encompass the entire network distribution from Mälarenergi AB, Västerås, Sweden. The physical model can then be used in conjunction with sensor data to calculate residual values.  These residuals are then used as input into a Bayesian Network to determine the possibility of three different operating outcomes. This approach will allow for operators to evaluate a systems performance, help in decision support mechanisms, and can provide assistance in scheduling maintenance.  

  • 925.
    Zimmerman, Nathan
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    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 Force Measurement, Västerås, Sweden.
    Achieving lower district heating network temperatures using feed-forward MPC2019In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 15, article id 2465Article in journal (Refereed)
    Abstract [en]

    The focus of this work is to present the feasibility of lowering the supply and return temperatures of district heating networks in order to achieve energy savings through the implementation of feed-forward model predictive control. The current level of district heating technology dictates a need for higher supply temperatures, which is not the case when considering the future outlook. In part, this can be attributed to the fact that current networks are being controlled by operator experience and outdoor temperatures. The prospects of reducing network temperatures can be evaluated by developing a dynamic model of the process which can then be used for control purposes. Two scenarios are presented in this work, to not only evaluate a controller's performance in supplying lower network temperatures, but to also assess the boundaries of the return temperature. In Scenario 1, the historical load is used as a feed-forward signal to the controller, and in Scenario 2, a load prediction model is used as the feed-forward signal. The findings for both scenarios suggest that the new control approach can lead to a load reduction of 12.5% and 13.7% respectively for the heat being supplied to the network. With the inclusion of predictions with increased accuracy on end-user demand and feed-back, the return temperature values can be better sustained, and can lead to a decrease in supply temperatures and an increase in energy savings on the production side.

  • 926.
    Zimmerman, Nathan
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    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 .
    Agglomeration Detection in Circulating Fluidized Bed Boilers Using Refuse Derived Fuels2016In: 2016 9th EUROSIM Congress on Modelling and Simulation, IEEE Computer Society, 2016, p. 123-128Conference paper (Refereed)
    Abstract [en]

    The formation of agglomerates in a refuse derived fuel (RDF) fired circulating fluidized bed (CFB) boiler has been investigated by implementing a dynamic model of the combustion process. The nature of refuse derived fuel, which is complex in composition, leads to an increased tendency for agglomerate formation. Notwithstanding the fact that a robust control scheme is essential in preventing the decrease in boiler efficiency from accelerated agglomerate formation. Therefore, a mechanism for detecting agglomeration through a physical model by looking at the minimum fluidization is presented. As agglomerates form between the fuel ash and bed sand the average diameter of the sand will increase and therefore the minimum fluidization velocity. Samples of bed material have been sieved and measured from a 150MW circulating fluidized bed boiler fired with refuse derived fuel to determine bed material size distribution. The findings have been correlated and match an increase in the minimum fluidization velocity during a seven day sampling period where the bed material size distribution increases above the average sand diameter.

  • 927.
    Zimmerman, Nathan
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    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 Force Measurement, Västerås, Sweden.
    Waste fuel combustion: Dynamic modeling and control2018In: Processes, ISSN 2227-9717, Vol. 6, no 11, article id 222Article in journal (Refereed)
    Abstract [en]

    The focus of this study is to present the adherent transients that accompany the combustion of waste derived fuels. This is accomplished, in large, by developing a dynamic model of the process, which can then be used for control purposes. Traditional control measures typically applied in the heat and power industry, i.e., PI (proportional-integral) controllers, might not be robust enough to handle the the accompanied transients associated with new fuels. Therefore, model predictive control is introduced as a means to achieve better combustion stability under transient conditions. The transient behavior of refuse derived fuel is addressed by developing a dynamic modeling library. Within the library, there are two models. The first is for assessing the performance of the heat exchangers to provide operational assistance for maintenance scheduling. The second model is of a circulating fluidized bed block, which includes combustion and steam (thermal) networks. The library has been validated using data from a 160 MW industrial installation located in Västerås, Sweden. The model can predict, with satisfactory accuracy, the boiler bed and riser temperatures, live steam temperature, and boiler load. This has been achieved by using process sensors for the feed-in streams. Based on this model three different control schemes are presented: a PI control scheme, model predictive control with feedforward, and model predictive control without feedforward. The model predictive control with feedforward has proven to give the best performance as it can maintain stable temperature profiles throughout the process when a measured disturbance is initiated. Furthermore, the implemented control incorporates the introduction of a soft-sensor for measuring the minimum fluidization velocity to maintain a consistent level of fluidization in the boiler for deterring bed material agglomeration.

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