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Wang, X., Xia, L., Bales, C., Zhang, X., Copertaro, B., Pan, S. & Wu, J. (2020). A systematic review of recent air source heat pump (ASHP) systems assisted by solar thermal, photovoltaic and photovoltaic/thermal sources. Renewable energy, 146, 2472-2487
Open this publication in new window or tab >>A systematic review of recent air source heat pump (ASHP) systems assisted by solar thermal, photovoltaic and photovoltaic/thermal sources
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2020 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 146, p. 2472-2487Article in journal (Refereed) Published
National Category
Energy Engineering
Research subject
Energy and Built Environments
Identifiers
urn:nbn:se:du-30632 (URN)10.1016/j.renene.2019.08.096 (DOI)2-s2.0-85071196687 (Scopus ID)
Available from: 2019-08-23 Created: 2019-08-23 Last updated: 2019-09-17Bibliographically approved
Huang, P., Fan, C., Zhang, X. & Wang, J. (2019). A hierarchical coordinated demand response control for buildings with improved performances at building group. Applied Energy, 242, 684-694
Open this publication in new window or tab >>A hierarchical coordinated demand response control for buildings with improved performances at building group
2019 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 242, p. 684-694Article in journal (Refereed) Published
Abstract [en]

Demand response control is one of the common means used for building peak demand limiting. Most of the existing demand response controls focused on single building’s performance optimization, and thus may cause new undesirable peak demands at building group, imposing stress on the grid power balance and limiting the economic savings. A few latest studies have demonstrated the potential benefits of demand response coordination, but the proposed methods cannot be applied in large scales. The main reason is that, for demand response coordination of multiple buildings, associated computational load and coordination complexity, increasing exponentially with building number, are challenges to be solved. This study, therefore, proposes a hierarchical demand response control to optimize operations of a large scale of buildings for group-level peak demand reduction. The hierarchical control first considers the building group as a ‘virtual’ building and searches the optimal performance that can be achieved at building group using genetic algorithm. To realize such optimal performance, it then coordinates each single building’s operation using non-linear programming. For validations, the proposed method has been applied on a case building group, and the study results show that the hierarchical control can overcome the challenges of excessive computational load and complexity. Moreover, in comparison with conventional independent control, it can achieve better performances in aspects of peak demand reduction and economic savings. This study provides a coordinated control for application in large scales, which can improve the effectiveness and efficiency in relieving the grid stress, and reduce the end-users’ electricity bills.

Keywords
Peak demand limiting, Demand response, Building group coordination, Economic cost, Grid interaction
National Category
Energy Engineering
Research subject
Energy and Built Environments
Identifiers
urn:nbn:se:du-29729 (URN)10.1016/j.apenergy.2019.03.148 (DOI)000470045800054 ()2-s2.0-85063025035 (Scopus ID)
Available from: 2019-03-20 Created: 2019-03-20 Last updated: 2019-07-22Bibliographically approved
Huang, P., Fan, C., Zhang, X. & Wang, J. (2019). A hierarchical coordinated demand response control for buildings with improved performances at building group. Applied Energy, 242, 684-694
Open this publication in new window or tab >>A hierarchical coordinated demand response control for buildings with improved performances at building group
2019 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 242, p. 684-694Article in journal (Refereed) Published
Abstract [en]

Demand response control is one of the common means used for building peak demand limiting. Most of the existing demand response controls focused on single building’s performance optimization, and thus may cause new undesirable peak demands at building group, imposing stress on the grid power balance and limiting the economic savings. A few latest studies have demonstrated the potential benefits of demand response coordination, but the proposed methods cannot be applied in large scales. The main reason is that, for demand response coordination of multiple buildings, associated computational load and coordination complexity, increasing exponentially with building number, are challenges to be solved. This study, therefore, proposes a hierarchical demand response control to optimize operations of a large scale of buildings for group-level peak demand reduction. The hierarchical control first considers the building group as a ‘virtual’ building and searches the optimal performance that can be achieved at building group using genetic algorithm. To realize such optimal performance, it then coordinates each single building’s operation using non-linear programming. For validations, the proposed method has been applied on a case building group, and the study results show that the hierarchical control can overcome the challenges of excessive computational load and complexity. Moreover, in comparison with conventional independent control, it can achieve better performances in aspects of peak demand reduction and economic savings. This study provides a coordinated control for application in large scales, which can improve the effectiveness and efficiency in relieving the grid stress, and reduce the end-users’ electricity bills.

Keywords
Peak demand limiting, Demand response, Building group coordination, Economic cost, Grid interaction
National Category
Building Technologies
Research subject
Energy and Built Environments
Identifiers
urn:nbn:se:du-30843 (URN)10.1016/j.apenergy.2019.03.148 (DOI)
Available from: 2019-09-30 Created: 2019-09-30 Last updated: 2019-10-01Bibliographically approved
Li, G., Tang, L., Zhang, X. & Dong, J. (2019). A review of factors affecting the efficiency of clean-in-place procedures in closed processing systems. Energy, 178, 57-71
Open this publication in new window or tab >>A review of factors affecting the efficiency of clean-in-place procedures in closed processing systems
2019 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 178, p. 57-71Article in journal (Refereed) Published
Abstract [en]

This paper reviews the current state of researches on improvement of Clean-In-Place (CIP) procedures in closed processing system thus saving energy, with a special attention paid to the hydrodynamic effects of cleaning fluid and the numerical and experimental approaches to investigate the identified controlling factors. The paper discussed the fouling problems of processing plants and the importance of sufficient CIP procedures, the forces contributing to cleaning with a special focus on the hydrodynamic effects. In general, it is possible to enhance hydrodynamic removal forces by local introduction of, among others, high wall shear stress and fluctuation rate of wall shear stress without consuming more energy. A theoretical model of particle removal in flow was also reviewed which supports the factors identified. The paper therefore further reviewed and compared the current state of modelling and experimental techniques on CIP improvement. To simulation the CIP process, it is necessary to consider 3D time-resolved Large Eddy Simulation with a Hybrid RANS-LES WMLES as Sub-Grid-Scale model because it captures both the mean and fluctuation rate of flow variables, while affordable for industrial flows. The wall shear stress measurement techniques and cleanablity test methods were also discussed and suggested.

Keywords
Clean-in-place, Efficiency, Hydraulic factors, Wall shear stress, CFD
National Category
Environmental Engineering
Research subject
Energy and Built Environments
Identifiers
urn:nbn:se:du-30009 (URN)10.1016/j.energy.2019.04.123 (DOI)000472686300005 ()2-s2.0-85065074591 (Scopus ID)
Available from: 2019-05-10 Created: 2019-05-10 Last updated: 2019-07-22Bibliographically approved
Han, M., May, R., Zhang, X., Wang, X., Pan, S., Yan, D., . . . Xu, L. (2019). A review of reinforcement learning methodologies for controlling occupant comfort in buildings. Sustainable cities and society, 51, Article ID 101748.
Open this publication in new window or tab >>A review of reinforcement learning methodologies for controlling occupant comfort in buildings
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2019 (English)In: Sustainable cities and society, ISSN 2210-6707, Vol. 51, article id 101748Article in journal (Refereed) Published
National Category
Building Technologies
Research subject
Complex Systems – Microdata Analysis
Identifiers
urn:nbn:se:du-30601 (URN)2-s2.0-85070980900 (Scopus ID)
Available from: 2019-08-08 Created: 2019-08-08 Last updated: 2019-10-11Bibliographically approved
Shen, J., Zhang, X. & Copertaro, B. (2019). An early-stage analysis of climate-adaptive designs for multi-family buildings under future climate scenario: case studies in Rome, Italy and Stockholm, Sweden.
Open this publication in new window or tab >>An early-stage analysis of climate-adaptive designs for multi-family buildings under future climate scenario: case studies in Rome, Italy and Stockholm, Sweden
2019 (English)In: Article in journal, Editorial material (Refereed) In press
Abstract [en]

This paper presents a preliminary case study for climate-adaptive residential multifamily building designs located in urban centre at early stage, to allow thermal comfort and minimum energy use from today to the last part of 21st century. The generated future climate data combined with comfort model assessment has been proposed as a new way including future climate scenarios in preliminary building design for two representative sites, in Rome, Italy and Stockholm, Sweden. The existing vulnerability to the expected climate conditions from psychometric analysis indicates that: (1) the climate trend in Rome would gradually lead to more failures in the majority of conventional adaptive design measures, as the cooling and dehumidification demands would rise from 5.3% to 23.6%, while the heating and humidification demands would decrease from 27% to 16%; (2) the climate trend in Stockholm would result in an increased comfort period by exploiting more adaptive design measures, since the heating and humidification demands would be reduced from 67% to 53%. However, the cooling and dehumidification demands would increase slightly from 0% to 1.5%. Accordingly, four main key risks are identified: 1) overheating would become a rising increasing public health threat for buildings in Rome that rely exclusively on natural ventilation; 2) open questions remain for the design team in the area of correct cooling load selection, additional space for the future installation and the effectiveness of current cooling device etc.; 3) occasional heat waves and gradual rising humidity levels are expected to be a vulnerable topic for conventional lightweight building in Stockholm; 4) buildings with a heavy heating load would tend to have greater cooling demand, especially those with poor ventilation resources or greater internal gains. In conclusion, it is suggested that envelope optimization, whichever climate type, is one of the most efficient and effective adaptation measures towards future climate conditions.

Keywords
Climate Change; Weather data morphing; Climate Adaptive Building Design; Thermal Comfort model; Psychrometric Analysis
National Category
Civil Engineering
Research subject
Energy and Built Environments, ENSECO - Produktion och process för utformning och konstruktion av energisjälvförsörjande containerbyggnader
Identifiers
urn:nbn:se:du-30824 (URN)
Projects
Energiinnovation i Sverige
Available from: 2019-09-30 Created: 2019-09-30 Last updated: 2019-09-30Bibliographically approved
Zhang, X., Wu, J., Pan, S. & Han, M. (2019). An economic analysis of the solar photovoltaic/thermal (PV/T) technologies in Sweden: A case study. In: IOP Conference Series: Materials Science and Engineering. Paper presented at Solaris 2018, The 9th edition of the international SOLARIS conference30th-31st of August, 2018, Chengdu, China. , 556(1), Article ID 012002.
Open this publication in new window or tab >>An economic analysis of the solar photovoltaic/thermal (PV/T) technologies in Sweden: A case study
2019 (English)In: IOP Conference Series: Materials Science and Engineering, 2019, Vol. 556, no 1, article id 012002Conference paper, Published paper (Refereed)
National Category
Energy Engineering
Research subject
Energy and Built Environments
Identifiers
urn:nbn:se:du-30821 (URN)10.1088/1757-899X/556/1/012002 (DOI)2-s2.0-85072132529 (Scopus ID)
Conference
Solaris 2018, The 9th edition of the international SOLARIS conference30th-31st of August, 2018, Chengdu, China
Available from: 2019-09-27 Created: 2019-09-27 Last updated: 2019-09-27Bibliographically approved
Pan, S., Du, S., Wang, X., Zhang, X., Xia, L., Liu, J., . . . Wei, Y. (2019). Analysis and interpretation of the particulate matter (PM10 and PM2.5) concentrations at the subway stations in Beijing, China. Sustainable cities and society, 45, 366-377
Open this publication in new window or tab >>Analysis and interpretation of the particulate matter (PM10 and PM2.5) concentrations at the subway stations in Beijing, China
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2019 (English)In: Sustainable cities and society, ISSN 2210-6707, Vol. 45, p. 366-377Article in journal (Refereed) Published
Abstract [en]

The particulate matters (PM10 and PM2.5) inside urban subway stations greatly influence indoor air quality and passenger comfort. This study aims to analyze and interpret the concentrations of PM10 and PM2.5, measured in several subway stations from October 9th to 22nd, 2016 in Beijing, China. The overall methodology was based on the Statistical Package for Social Science (SPSS) software while General linear model (GLM) and correlation analysis were further applied to examine the sensitivities of different variables to the particle concentrations. The data analysis showed the average overall mass ratio of PM concentrations inside subway station is about 68.7%, much lower than outdoor condition (79.6%). In the areas of the station hall and platform, the real-time PM10 and PM2.5 concentrations varied periodically. In working and operation offices, all rooms had much higher PM concentrations than the outdoor environment when its pollution level was level 3, in which the facility room reached the highest level, while the closed meeting room had the lowest. Correlation analysis results indicated that PM10 and PM2.5 concentrations were mutually correlated (average R2 = 0.854), and a strong linear correlation (R2 = 0.897) of the subway-station PM concentrations to the outdoor PM conditions, regardless of the outdoor atmospheric PM concentrations pollution level was. Nevertheless, the impact of passenger number and temperature & humidity on the station PM concentrations was less, when compared to the outdoor environment. This paper is expected to provide useful information for further research and design of effective prevention measures on PM in local subway stations, towards a more sustainable and healthier built environment in the city underground. 

Keywords
Correlation analysis, Influencing factors, PM10, PM2.5, Subway station
National Category
Energy Engineering Energy Systems
Research subject
Energy, Forests and Built Environments
Identifiers
urn:nbn:se:du-28908 (URN)10.1016/j.scs.2018.11.020 (DOI)000455274500032 ()2-s2.0-85057734557 (Scopus ID)
Available from: 2018-11-19 Created: 2018-11-19 Last updated: 2019-01-24Bibliographically approved
Zhang, X., Xiao, M., He, W., Qiu, Z. & Zhao, X. (2019). Heat Pump Technologies and Their Applications in Solar Systems. In: Xudong Zhao, Xiaoli Ma (Ed.), Advanced Energy Efficiency Technologies for Solar Heating, Cooling and Power Generation: (pp. 311-339). Springer
Open this publication in new window or tab >>Heat Pump Technologies and Their Applications in Solar Systems
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2019 (English)In: Advanced Energy Efficiency Technologies for Solar Heating, Cooling and Power Generation / [ed] Xudong Zhao, Xiaoli Ma, Springer, 2019, p. 311-339Chapter in book (Refereed)
Abstract [en]

As the well known that global energy demand is on a trend of continuous growth, reducing energy demand and making good use of renewable energy are thought to be the major routes toward low carbon and sustainable future, in particular for the building sector. Compared to traditional gas-fired heating systems, heat pumps have been proved to be an energy-efficient heating technology which can save fossil fuel energy and consequently reduce CO2 emission. However, the most outstanding challenges for the application of heat pumps lie in their high demand for electrical power, and the insufficient heat transfer between the heat source and the refrigerant. To overcome these difficulties, a solar-assisted heat pump has been proposed to tackle these challenges. A solar-assisted heat pump combines a heat pump with a solar collector, enabling the use of solar energy to provide space heating and hot water for buildings. This chapter introduces heat pump technologies and their applications in solar systems. Two types of solar-assisted heat pump, direct and indirect expansion, are illustrated in details. This work has provided the fundamental research and experience for developing a solar heat pump system and contributing to a significant fossil fuel saving and carbon reduction in the global extent.

Place, publisher, year, edition, pages
Springer, 2019
Series
Green Energy and Technology
Keywords
Heat pump, PV, Loop heat pipe, Micro-channels-evaporator, Performance
National Category
Energy Engineering
Research subject
Energy and Built Environments
Identifiers
urn:nbn:se:du-30577 (URN)10.1007/978-3-030-17283-1_9 (DOI)2-s2.0-85068761593 (Scopus ID)978-3-030-17282-4 (ISBN)978-3-030-17283-1 (ISBN)
Available from: 2019-07-24 Created: 2019-07-24 Last updated: 2019-07-24Bibliographically approved
Petrovic, B., Myhren, J. A., Zhang, X., Wallhagen, M. & Eriksson, O. (2019). Life cycle assessment of a wooden single-family house in Sweden. Applied Energy, 251, 113-253, Article ID 113253.
Open this publication in new window or tab >>Life cycle assessment of a wooden single-family house in Sweden
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2019 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 251, p. 113-253, article id 113253Article in journal (Refereed) Published
Abstract [en]

To understand the reasons behind the large environmental impact from buildings the whole life cycle needs to be considered. Therefore, this study evaluates the carbon dioxide emissions in all stages of a single-family house in Sweden from the production of building materials, followed by construction and user stages until the end-of-life of the building in a life cycle assessment (LCA). The methodology applied is attributional life cycle assessment (LCA) based on ‘One Click LCA’ tool and a calculated life span of 100 years. Global warming potential (GWP) and primary energy (PE) are calculated by using specific data from the case study, furthermore the data regarding building materials are based on Environmental Product Declarations (EPDs). The results show that the selection of wood-based materials has a significantly lower impact on the carbon dioxide emissions in comparison with non-wood based materials. The total emissions for this single-family house in Sweden are 6 kg CO 2 e/m 2 /year. The production stage of building materials, including building systems and installations represent 30% of the total carbon dioxide equivalent emissions, while the maintenance and replacement part represents 37%. However, energy use during the in-use stage of the house recorded lower environmental impact (21%) due to the Swedish electricity mix that is mostly based on energy sources with low carbon dioxide emissions. The water consumption, construction and the end-of-life stages have shown minor contribution to the buildings total greenhouse gas (GHG) emissions (12%). The primary energy indicator shows the largest share in the operational phase of the house.

Keywords
Carbon dioxide equivalent emission, Environmental product declaration, Global warming potential, Life cycle assessment, Primary energy, Single-family house
National Category
Energy Systems
Research subject
Energy and Built Environments
Identifiers
urn:nbn:se:du-30118 (URN)10.1016/j.apenergy.2019.05.056 (DOI)2-s2.0-85065788114 (Scopus ID)
Available from: 2019-05-31 Created: 2019-05-31 Last updated: 2019-06-03Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-2369-0169

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