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Cooperative Performance of Potentially Developed Thermochromic Glazing under Different Climates
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Energy Procedia 158 Energy Procedia 00(2019) (2017)3094–3100 000–000 www.elsevier.com/locate/procedia
10th International Conference on Applied Energy (ICAE2018), 22-25 August 2018, Hong Kong, 10th International Conference on Applied Energy China(ICAE2018), 22-25 August 2018, Hong Kong, China
Cooperative Performance of Potentially Developed Thermochromic 15th InternationalofSymposium on District Heating and Cooling CooperativeThePerformance Potentially Developed Thermochromic Glazing under Different Climates Glazing under Different Climates Assessing the feasibility ofa, Robin usingWilson the heat demand-outdoor a a Runqi Liang , Yanyi Sun , Yupeng Wuaa* a a a Runqi Liang , for Yanyi , Robin Wilson , Yupeng Wu * temperature function a Sun long-term district heat demand forecast Department of Architecture and Built Environment, Faculty of Engineering, University of Nottingham, University Park, Nottingham, 2RD, UK University of Nottingham, Department of Architecture and Built Environment, FacultyNG7 of Engineering,
a b c c Park, ,Nottingham, NG7 2RD, UK Lacarrière , O. Le Corre I. Andrića,b,c*, A. Pinaa, University P. Ferrão J. Fournier ., B. a Abstract IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal b Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France Abstract c Département Systèmes Énergétiques et Environnement - IMTtransmitted Atlantique, 4into rue Alfred Kastler, Nantes, France window Thermochromic (TC) windows are able to adjust solar radiation buildings in 44300 response to different surface temperature. most common TC material for TCin window, can reduce near Thermochromic (TC)Vanadium windows Dioxide are able (VO to adjust solar radiation transmitted intoused buildings responseasto itdifferent window 2) is the infrared (NIR) solar transmittance to block(VO undesired gains during the hotused day when surface as temperature abovenear its surface temperature. Vanadium Dioxide mostheat common TC material for TCthewindow, it can reduce 2) is thesolar transition(NIR) temperature. However, few have undesired studied the effect TC window onhot theday indoor luminous environment. Inabove order its to infrared solar transmittance to block solar heatofgains during the when the surface temperature Abstractthe daylighting control, an innovative iron-liquid based TC window film with control on the visible spectrum was improve transition temperature. However, few have studied the effect of TC window on the indoor luminous environment. In order to introduced applied in control, cooperation with VO2 based TC material study. The of these two types improve theand daylighting an innovative iron-liquid based in TCthis window film cooperative with controlperformance on the visible spectrum was District heating networks areunder commonly addressed in literature as one are ofThe the most Shanghai effective solutions decreasing the of TC materials was discussed three conditions in China, which Beijing, and Guangzhou. The introduced and applied in cooperation withclimatic VO TCthe material in this study. cooperative performance offorthese tworesults types 2 based greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat show their energy saving under potential and daylighting regulation ability thatare affected byShanghai the cooperative implement is results highly of TC that materials was discussed three climatic conditions in China, which Beijing, and Guangzhou. The sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, depended climates. show that on their energy saving potential and daylighting regulation ability that affected by the cooperative implement is highly prolonging the investment return period. depended on climates. The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand Copyright © 2018 Elsevier Ltd. All rights reserved. forecast. The districtPublished of Alvalade, locatedLtd. in Lisbon (Portugal), was used as a caseth study. The district is consisted of 665 © 2019 The Authors. by responsibility Elsevier Selection and peer-review under of the scientific committee of the 10 International Conference on Applied Copyright © 2018 Elsevier Ltd. All rights reserved. This is an open the CC period BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) buildings that access vary inarticle both under construction and typology. Three weather scenarios (low, medium, high) and three district Energy (ICAE2018). Selection and peer-review under responsibility of the scientific committee theInternational 10th International Conference on Applied Peer-review responsibility of the scientific of ICAE2018 Theof10th Conference on Applied Energy. renovation under scenarios were developed (shallow,committee intermediate, deep). To– estimate the error, obtained heat demand values were Energy (ICAE2018). compared with results from a dynamic heat demand model, previously developed and validated by the authors. Keywords: Thermochormic; EnergyPlus; Cooperation; Energy Consumption; Daylighting. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications Keywords: Thermochormic; EnergyPlus; Cooperation; Energy Consumption; Daylighting. (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). 1. Introduction The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the 1. Introduction decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and Solar radiation penetrates through a window system offers heat for gains and illumination to the indoor renovation scenariosthat considered). On the other hand, function intercept increased 7.8-12.7% per decade (depending on the Solar radiation that penetrates through a window system offers heat gains and illumination to the indoor environment of a building, therefore, affects thermal and visual comfort for occupants in a building [1-3]. coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and environment of (TC) a building, therefore, affects and visual comfort for occupants in a building [1-3]. Thermochromic glazing as one of thethermal chromogenic window technologies, has the capacity of reversible improve the accuracy ofsmart heat demand estimations.
Thermochromic (TC) smart glazing as one of the chromogenic window technologies, has the capacity of reversible © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. * Corresponding author. Tel.: +44 (0) 115 74 84011.
E-mail address:author. [email protected], * Corresponding Tel.: +44 (0) 115 74 [email protected] Keywords: Heat demand; Forecast; Climate change [email protected] E-mail address: [email protected], 1876-6102 Copyright © 2018 Elsevier Ltd. All rights reserved. th Selection and peer-review under responsibility the scientific 1876-6102 Copyright © 2018 Elsevier Ltd. All of rights reserved. committee of the 10 International Conference on Applied Energy (ICAE2018). Selection and peer-review under responsibility of the scientific committee of the 10th International Conference on Applied Energy (ICAE2018).
1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. 1876-6102 © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of ICAE2018 – The 10th International Conference on Applied Energy. 10.1016/j.egypro.2019.01.1002
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transformation on spectral transmittance according to temperature variations. A considerable volume of previous studies showed that Vanadium Dioxide (VO2) based TC windows have the advantages to improve the energy efficient and thermal comfort level of the buildings that applied them, especially in hot climates [4-8]. However, the TC windows that have a significant adjustment on daylighting and visual comfort have rarely been discussed. In this paper, an iron-liquid based TC film with transmittance variation occurs within the visible spectrum was introduced to adjust the daylit luminous environment. In addition, this iron-liquid based TC film was proposed to work in cooperation with VO2 based TC material to explore the most potential development of TC windows under different climates for improving both energy and daylight performance of buildings. A typical office Building with TC windows applied was comprehensively studied using EnergyPlus, aiming to provide some guidance for the further development and application of the potential TC materials. 2. Methodology A typical office model was built in EnergyPlus to carry out the prediction of building performance affected by different TC cooperative implement cases. Under three different climates, energy consumption and useful daylight illuminance (UDI) of the model was analysed to find out the most optimal cooperation between the two types of TC films. 2.1. Climates Beijing, Shanghai and Guangzhou were selected, representing three climatic zones in China that has the potential to employ TC windows: 1) Beijing stands for cold zone with the most frequent temperature of 0-10oC and solar incident angle of 20-30o; 2) Shanghai is for hot summer and cold winter zone with the most frequent temperature of 20-30oC and solar incident angle of 30-40o; 3) Guangzhou represents hot summer and warm winter zone, it has the most frequent temperature of 30-40oC and solar incident angle of 40-50o. 2.2. Model Setup A mid-floor office, which has the external dimensions of 6m×5m×3m (length × width × height), of a multistoried building was modelled in EnergyPlus. Adjacent offices were assumed to be in the same conditions as the studied office. The south wall with the window installed is the unique facade exposed to the outdoor environment, according to building standard in China [9], U-value of external wall is 0.43W/m2k, while that of double glazing window is 2.7W/m2k. Standard equipment and lighting loads were set up as 13 W/m2 and 11 W/m2 separately. Occupant density was 18.6 m2/per person and working time is between 9 am to 5 pm on weekdays. HVAC was applied to control the indoor temperature as constant 21ºC [10]. Using a constant thermostat temperature for both summer and winter operating condition is essential to minimise the impact of varying indoor temperature on selected TC windows. Two illuminance zones along the depth axis were assigned to investigate the daylight performance of the proposed TC windows, exploring their impact on artificial lighting energy consumption and daylit illuminance levels. An automatic dimming control of artificial lighting was applied to meet the target illuminance at work plane of 500lux [11], being monitored by two sensors placed at 1.5 meters (sensor 1) and 4.5 meters (sensor 2) away from the window, respectively, along with the central axis of the room. 2.3. TC glazing materials As aforementioned, simulations in this study based on two selected TC materials: 1) VO2 nanoparticle (i.e., VO2_Nano) film, which has the feature of apparent reduction in the NIR spectrum of the transmitted solar radiation when its temperature increases above the transition temperature, while with a slight decrease of transmittance within the visible spectrum [12] ; 2) A composite film of Ionic-liquid containing [bmim]2 NiCl4 (TC_IL-NiII), which has the capable of reducing the visible transmittance with temperature increasing [13]. The spectral transmittances of VO2_Nano and TC_IL-NiII are shown in Fig. 1 (a) and (b), respectively. In Fig. 1, T (Clear) represents for the clear state while T (Tinted) represents for the tinted state. Based on previous studies[14], enlarging the variation of solar
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transmittance between clear and tinted states of VO2_Nano and TC_IL-NiII films was able to achieve significant improvement in energy and daylight performance. To embody the consideration of these advanced scenarios, materials with enlarged solar transmittance variation for both TC windows were further studied in this work and labelled as T (Tinted_L) in Fig. 1. In order to further explore the potential development of both TC windows, VO2_Nano and TC_IL-NiII windows with enlarged solar transmittance variation were employed cooperatively. Since the TC windows are temperature-dependent, both VO2_Nano (i.e., mainly with NIR transmittance changing) and TC_IL-NiII (i.e., mainly with visible (VIS) transmittance changing) films were numerically analysed at three transition temperatures (Tt): 20, 30 and 40°C. The pairwise cooperation permutations resulted in 9 pairs of scenarios in total. They were classified into three groups: 1) the cooperative cases with VO2_Nano and TC_IL-NiII having the same transition temperatures of 20°C, 30°C and 40°C were labelled as ‘Same Tt20’, ‘Same Tt30’ and ‘Same Tt40’, respectively; 2) the cooperative cases with VO2_Nano having lower transition temperatures than that of TC_IL-NiII were labelled as ‘NIR_20 VIS_30’, ‘NIR_20 VIS_40’, and ‘NIR_30 VIS_40’, respectively. It means that, with the temperature increasing, the NIR transmittance would decrease firstly, and then the visible transmittance decreases at a higher temperature. For instance, ‘NIR_20 VIS_30’ represents that the VO2_Nano film with Tt of 20°C is cooperating with TC_IL-NiII film with Tt of 30°C; 3) accordingly, the cooperation cases with TC_IL-NiII having lower transition temperatures than VO2_Nano were named as ‘VIS_20 NIR_30’, ‘VIS_20 NIR_40’, and ‘VIS_30 NIR_40’. A reference case with standard double glazing (DG) was investigated, in order to find out the advantages and disadvantages caused by the different TC cooperative implement cases.
Fig. 1. Spectral transmittance of VO2_Nano (a) and TC_IL-NiII (b)
3. Results and discussion 3.1. Energy performance and UDI distributions The energy consumption and UDI distribution that affected by the three groups of cooperative cases between the two typical TC materials are shown in Fig. 2. When the pairwise TC films have the same transition temperature, cooperative case ‘Same_Tt30’ leads to the most significant energy saving potential in Beijing, with a 14.57% reduction of energy consumption when compared with DG. However, in Shanghai, the most appropriate cooperation case is ‘Same Tt40’, reaching maximum energy conservation of 13.50% when compared with DG. In Guangzhou, with the increase of transition temperature, the decrease of lighting demand is complementary to the increase of cooling demand, resulting in similar overall energy consumption for ‘Same_Tt20’, ‘Same_Tt30’ and ‘Same_Tt40’. As can be seen in Fig. 2 (b) (d) (f), in Beijing and Shanghai, ‘Same Tt 20’ case results in the highest percentage of working hours falling into UDI500-2000lux (a useful bin meeting the illuminance requirement of working environment, 500 lux < illuminance value < 2000 lux), which is 48.12% and 63.49%, respectively. While in Guangzhou, the highest UDI500-2000lux of 64.58% occurs when implementing the ‘Same Tt 30’ case.
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‘NIR_20 VIS_30’, ‘NIR_20 VIS_40’, and ‘NIR_30 VIS_40’ cases indicate that NIR solar radiation transmitted into the room got the adjustment earlier than that of visible solar radiation with the temperature increasing. When comparing with DG, the results present that ‘NIR_30 VIS_40’ is the most energy effective case under the climates of Beijing and Shanghai with an energy saving of 17.5% and 15.55%. However, the improvement in UDI500-2000lux offered by ‘NIR_30 VIS_40’ is restricted. In Guangzhou, ‘NIR_20 VIS_30’ provides the most significant energy reduction. Meanwhile, the percentage of working hours within the illuminance range from 500lux to 2000 lux is approaching 67%, which is higher than any other cases in this group.
Fig. 2. Energy consumption and annual UDI levels at sensor 1 affected by TC windows of scenario III with different transition temperatures and lower visible transmittance at tinted state under three climates.
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‘VIS_20 NIR_30’, ‘VIS_20 NIR_40’, and ‘VIS_30 NIR_40’ cases indicate that visible light transmitted into the room got the adjustment earlier than that of NIR solar radiation with the temperature increasing. Fig. 2(a) (c) (e) shows that in Beijing and Shanghai the case of ‘VIS_30 NIR_40’ induces the most energy saving when compared with DG, but less improvement of UDI500-2000lux, than the other two cases. However, in Guangzhou, ‘VIS_20 NIR_30’ case leads to the most energy saving (13.68% energy reduction when compared with DG), and the highest value of UDI500-2000lux (~65%) among the three cases. 3.2. Further comparison between cooperative cases and individual cases In order to further explore the significance of cooperative implementing, the percentage of energy saving and improvement of daylighting performance (UDI500-2000lux) affected by cooperative cases of VO2_Nano and TC_IL-NiII films were compared with cases of applying each film individually at various transmission temperatures. And the results were shown in Table 2, green area shows the performance of each cooperative implement case, while yellow area presents that of each individual VO2_Nano window case, and the blue shows individual TC_IL-NiII window case. Table 2: Energy saving and improvement of UDI500-2000lux at sensor I affected by the revised TC windows and cooperative cases (* Better performance than revised VO2_Nano or revised TC_IL-NiII; ** Better performance than revised VO2_Nano and revised TC_IL-NiII)
In Beijing, 4 (i.e., marked with two stars in green area) out of 9 cooperative cases have an improvement in energy and daylighting performance compared with each of the individual case. Among that, the cooperation between VO2_Nano Tt40 and TC_IL-NiII Tt30 (i.e., VIS_30 NIR_40) has the most significant increase of energy saving (2.46%) and improvement of UDI500-2000lux (15.96%) when compared with applying VO2_Nano Tt40 window individually. It reveals that adjusting visible transmittance at a lower temperature than NIR transmittance under the climatic condition of Beijing is more effective than any other cooperative cases.
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In Shanghai, 2 out of 9 cooperative cases have better energy and daylighting performance than using each of the individual TC_IL-NiII or VO2_Nano windows respectively. The TC_IL-NiII Tt30 cooperatively implementing with the VO2_Nano Tt40 (i.e., VIS_30 NIR_40) results in 14.06% increase of energy saving, and 38.69% increase of UDI500-2000lux, which is the most effective case for both energy and daylighting. Meanwhile, it can be seen that under the climatic conditions of Shanghai, most of the individual VO2_Nano cases perform more energy efficient than cooperative cases, while the improvement in UDI500-2000lux is the most significant contribution of cooperative cases. It means that the properties of individual VO2_Nano window are suitable for Shanghai. In Guangzhou, 5 out of 9 cooperative cases are detected to be significant for both energy and daylighting improvement. The TC_IL-NiII Tt40 cooperating with VO2_Nano Tt30 results in the improvement of energy saving when compared with each individual case with energy saving increased by 3.11%, while the increase of UDI500II 2000lux is restricted by 2.37%. On the other hand, the cooperation between TC_IL-Ni Tt30 and VO2_Nano Tt20 or Tt30 case leads to improvement in energy saving by up to 1.97%, while the UDI500-2000lux is significantly increased by 30%. To sum up, in Guangzhou, reducing NIR transmittance at a lower temperature than reduction of visible transmittance is able to improve both energy and daylighting performance. 4. Conclusions Building simulation conducted by EnergyPlus shows that cooperation between TC_IL-NiII and VO2_Nano films enables a further improvement in both energy and daylighting performance. Depending on climatic conditions, the optimal cooperative scenarios are varying: In Beijing, ‘VIS_30 NIR_40’ is the best case, i.e., reducing the oversupplied daylighting on cold days, and both overlit and overheat on hot days; In Shanghai, both improved VO2_Nano working alone and ‘VIS_30 NIR_40’ are all suitable due to its moderate warm climates; In Guangzhou, adjusting the overheat as a matter of priority is beneficial to both energy and daylighting performance. Acknowledgements This work was supported by the Faculty of Engineering, the University of Nottingham through a PhD studentship to Runqi Liang. References [1] [2] [3] [4] [5] [6] [7] [8] [9]
Wong, Ing Liang, A review of daylighting design and implementation in buildings. Renewable and Sustainable Energy Reviews, 2017. 74: p. 959-968. Huang, Yu, Niu, Jian-lei, and Chung, Tse-ming, Comprehensive analysis on thermal and daylighting performance of glazing and shading designs on office building envelope in cooling-dominant climates. Applied Energy, 2014. 134: p. 215-228. Sun, Yanyi, Wu, Yupeng, and Wilson, Robin, Analysis of the daylight performance of a glazing system with Parallel Slat Transparent Insulation Material (PS-TIM). Energy and Buildings, 2017. 139: p. 616-633. Ye, Hong, Long, Linshuang, Zhang, Haitao, Xu, Bin, Gao, Yanfeng, Kang, Litao, and Chen, Zhang, The demonstration and simulation of the application performance of the vanadium dioxide single glazing. Solar Energy Materials and Solar Cells, 2013. 117: p. 168-173. Long, Linshuang and Ye, Hong, Discussion of the performance improvement of thermochromic smart glazing applied in passive buildings. Solar Energy, 2014. 107: p. 236-244. Saeli, Manfredi, Piccirillo, Clara, Parkin, Ivan P., Binions, Russell, and Ridley, Ian, Energy modelling studies of thermochromic glazing. Energy and Buildings, 2010. 42(10): p. 1666-1673. Hoffmann, Sabine, Lee, Eleanor S., and Clavero, César, Examination of the technical potential of nearinfrared switching thermochromic windows for commercial building applications. Solar Energy Materials and Solar Cells, 2014. 123: p. 65-80. Ye, Hong and Long, Linshuang, Smart or not? A theoretical discussion on the smart regulation capacity of vanadium dioxide glazing. Solar Energy Materials and Solar Cells, 2014. 120: p. 669-674. Construction, Ministry of and General Administration of Quality Supervision, Inspection and Quarantine,
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GB50189-2005 Design Standard for Energy Efficiency of Public Buildings. 2005, Ministry of Construction. CIBSE, GuideA: Environmental design. 1999, The Chartered Institution of Building: Services Engineers London. BSI, BS EN 12464-1:2011 Light and lighting - Lighting of work places. Indoor work places. 2011, BSI Stardard. Li, Shuyi, VO2-based Thermochromic and Nanothermochromic Materials for Energy-Efficient Windows, in Science and technology. 2013, Uppsala University. p. 142. Wei, Xianjun, Yu, Linpo, Jin, Xianbo, Wang, Dihua, and Chen, George Z., Solar-thermochromism of Pseudocrystalline Nanodroplets of lonic Liquid-Ni Complexes immobilized inside translucent Microporous PVDF Films. Advanced Materials, 2009. 21: p. 776-780. Liang, Runqi, Sun, Yanyi, Aburas, Marina, Wilson, Robin, and Wu, Yupeng, Evaluation of the thermal and optical performance of thermochromic windows for office buildings in China. Energy and Buildings, 2018. 176: p. 216-231.
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Energyonline Procedia 00 (2018) 000–000 Available onlineatat www.sciencedirect.com Available www.sciencedirect.com Energy Procedia 00 (2018) 000–000
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www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia
Energy Procedia 158 Energy Procedia 00(2019) (2017)3094–3100 000–000 www.elsevier.com/locate/procedia
10th International Conference on Applied Energy (ICAE2018), 22-25 August 2018, Hong Kong, 10th International Conference on Applied Energy China(ICAE2018), 22-25 August 2018, Hong Kong, China
Cooperative Performance of Potentially Developed Thermochromic 15th InternationalofSymposium on District Heating and Cooling CooperativeThePerformance Potentially Developed Thermochromic Glazing under Different Climates Glazing under Different Climates Assessing the feasibility ofa, Robin usingWilson the heat demand-outdoor a a Runqi Liang , Yanyi Sun , Yupeng Wuaa* a a a Runqi Liang , for Yanyi , Robin Wilson , Yupeng Wu * temperature function a Sun long-term district heat demand forecast Department of Architecture and Built Environment, Faculty of Engineering, University of Nottingham, University Park, Nottingham, 2RD, UK University of Nottingham, Department of Architecture and Built Environment, FacultyNG7 of Engineering,
a b c c Park, ,Nottingham, NG7 2RD, UK Lacarrière , O. Le Corre I. Andrića,b,c*, A. Pinaa, University P. Ferrão J. Fournier ., B. a Abstract IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal b Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France Abstract c Département Systèmes Énergétiques et Environnement - IMTtransmitted Atlantique, 4into rue Alfred Kastler, Nantes, France window Thermochromic (TC) windows are able to adjust solar radiation buildings in 44300 response to different surface temperature. most common TC material for TCin window, can reduce near Thermochromic (TC)Vanadium windows Dioxide are able (VO to adjust solar radiation transmitted intoused buildings responseasto itdifferent window 2) is the infrared (NIR) solar transmittance to block(VO undesired gains during the hotused day when surface as temperature abovenear its surface temperature. Vanadium Dioxide mostheat common TC material for TCthewindow, it can reduce 2) is thesolar transition(NIR) temperature. However, few have undesired studied the effect TC window onhot theday indoor luminous environment. Inabove order its to infrared solar transmittance to block solar heatofgains during the when the surface temperature Abstractthe daylighting control, an innovative iron-liquid based TC window film with control on the visible spectrum was improve transition temperature. However, few have studied the effect of TC window on the indoor luminous environment. In order to introduced applied in control, cooperation with VO2 based TC material study. The of these two types improve theand daylighting an innovative iron-liquid based in TCthis window film cooperative with controlperformance on the visible spectrum was District heating networks areunder commonly addressed in literature as one are ofThe the most Shanghai effective solutions decreasing the of TC materials was discussed three conditions in China, which Beijing, and Guangzhou. The introduced and applied in cooperation withclimatic VO TCthe material in this study. cooperative performance offorthese tworesults types 2 based greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat show their energy saving under potential and daylighting regulation ability thatare affected byShanghai the cooperative implement is results highly of TC that materials was discussed three climatic conditions in China, which Beijing, and Guangzhou. The sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, depended climates. show that on their energy saving potential and daylighting regulation ability that affected by the cooperative implement is highly prolonging the investment return period. depended on climates. The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand Copyright © 2018 Elsevier Ltd. All rights reserved. forecast. The districtPublished of Alvalade, locatedLtd. in Lisbon (Portugal), was used as a caseth study. The district is consisted of 665 © 2019 The Authors. by responsibility Elsevier Selection and peer-review under of the scientific committee of the 10 International Conference on Applied Copyright © 2018 Elsevier Ltd. All rights reserved. This is an open the CC period BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) buildings that access vary inarticle both under construction and typology. Three weather scenarios (low, medium, high) and three district Energy (ICAE2018). Selection and peer-review under responsibility of the scientific committee theInternational 10th International Conference on Applied Peer-review responsibility of the scientific of ICAE2018 Theof10th Conference on Applied Energy. renovation under scenarios were developed (shallow,committee intermediate, deep). To– estimate the error, obtained heat demand values were Energy (ICAE2018). compared with results from a dynamic heat demand model, previously developed and validated by the authors. Keywords: Thermochormic; EnergyPlus; Cooperation; Energy Consumption; Daylighting. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications Keywords: Thermochormic; EnergyPlus; Cooperation; Energy Consumption; Daylighting. (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). 1. Introduction The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the 1. Introduction decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and Solar radiation penetrates through a window system offers heat for gains and illumination to the indoor renovation scenariosthat considered). On the other hand, function intercept increased 7.8-12.7% per decade (depending on the Solar radiation that penetrates through a window system offers heat gains and illumination to the indoor environment of a building, therefore, affects thermal and visual comfort for occupants in a building [1-3]. coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and environment of (TC) a building, therefore, affects and visual comfort for occupants in a building [1-3]. Thermochromic glazing as one of thethermal chromogenic window technologies, has the capacity of reversible improve the accuracy ofsmart heat demand estimations.
Thermochromic (TC) smart glazing as one of the chromogenic window technologies, has the capacity of reversible © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. * Corresponding author. Tel.: +44 (0) 115 74 84011.
E-mail address:author. [email protected], * Corresponding Tel.: +44 (0) 115 74 [email protected] Keywords: Heat demand; Forecast; Climate change [email protected] E-mail address: [email protected], 1876-6102 Copyright © 2018 Elsevier Ltd. All rights reserved. th Selection and peer-review under responsibility the scientific 1876-6102 Copyright © 2018 Elsevier Ltd. All of rights reserved. committee of the 10 International Conference on Applied Energy (ICAE2018). Selection and peer-review under responsibility of the scientific committee of the 10th International Conference on Applied Energy (ICAE2018).
1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. 1876-6102 © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of ICAE2018 – The 10th International Conference on Applied Energy. 10.1016/j.egypro.2019.01.1002
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transformation on spectral transmittance according to temperature variations. A considerable volume of previous studies showed that Vanadium Dioxide (VO2) based TC windows have the advantages to improve the energy efficient and thermal comfort level of the buildings that applied them, especially in hot climates [4-8]. However, the TC windows that have a significant adjustment on daylighting and visual comfort have rarely been discussed. In this paper, an iron-liquid based TC film with transmittance variation occurs within the visible spectrum was introduced to adjust the daylit luminous environment. In addition, this iron-liquid based TC film was proposed to work in cooperation with VO2 based TC material to explore the most potential development of TC windows under different climates for improving both energy and daylight performance of buildings. A typical office Building with TC windows applied was comprehensively studied using EnergyPlus, aiming to provide some guidance for the further development and application of the potential TC materials. 2. Methodology A typical office model was built in EnergyPlus to carry out the prediction of building performance affected by different TC cooperative implement cases. Under three different climates, energy consumption and useful daylight illuminance (UDI) of the model was analysed to find out the most optimal cooperation between the two types of TC films. 2.1. Climates Beijing, Shanghai and Guangzhou were selected, representing three climatic zones in China that has the potential to employ TC windows: 1) Beijing stands for cold zone with the most frequent temperature of 0-10oC and solar incident angle of 20-30o; 2) Shanghai is for hot summer and cold winter zone with the most frequent temperature of 20-30oC and solar incident angle of 30-40o; 3) Guangzhou represents hot summer and warm winter zone, it has the most frequent temperature of 30-40oC and solar incident angle of 40-50o. 2.2. Model Setup A mid-floor office, which has the external dimensions of 6m×5m×3m (length × width × height), of a multistoried building was modelled in EnergyPlus. Adjacent offices were assumed to be in the same conditions as the studied office. The south wall with the window installed is the unique facade exposed to the outdoor environment, according to building standard in China [9], U-value of external wall is 0.43W/m2k, while that of double glazing window is 2.7W/m2k. Standard equipment and lighting loads were set up as 13 W/m2 and 11 W/m2 separately. Occupant density was 18.6 m2/per person and working time is between 9 am to 5 pm on weekdays. HVAC was applied to control the indoor temperature as constant 21ºC [10]. Using a constant thermostat temperature for both summer and winter operating condition is essential to minimise the impact of varying indoor temperature on selected TC windows. Two illuminance zones along the depth axis were assigned to investigate the daylight performance of the proposed TC windows, exploring their impact on artificial lighting energy consumption and daylit illuminance levels. An automatic dimming control of artificial lighting was applied to meet the target illuminance at work plane of 500lux [11], being monitored by two sensors placed at 1.5 meters (sensor 1) and 4.5 meters (sensor 2) away from the window, respectively, along with the central axis of the room. 2.3. TC glazing materials As aforementioned, simulations in this study based on two selected TC materials: 1) VO2 nanoparticle (i.e., VO2_Nano) film, which has the feature of apparent reduction in the NIR spectrum of the transmitted solar radiation when its temperature increases above the transition temperature, while with a slight decrease of transmittance within the visible spectrum [12] ; 2) A composite film of Ionic-liquid containing [bmim]2 NiCl4 (TC_IL-NiII), which has the capable of reducing the visible transmittance with temperature increasing [13]. The spectral transmittances of VO2_Nano and TC_IL-NiII are shown in Fig. 1 (a) and (b), respectively. In Fig. 1, T (Clear) represents for the clear state while T (Tinted) represents for the tinted state. Based on previous studies[14], enlarging the variation of solar
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transmittance between clear and tinted states of VO2_Nano and TC_IL-NiII films was able to achieve significant improvement in energy and daylight performance. To embody the consideration of these advanced scenarios, materials with enlarged solar transmittance variation for both TC windows were further studied in this work and labelled as T (Tinted_L) in Fig. 1. In order to further explore the potential development of both TC windows, VO2_Nano and TC_IL-NiII windows with enlarged solar transmittance variation were employed cooperatively. Since the TC windows are temperature-dependent, both VO2_Nano (i.e., mainly with NIR transmittance changing) and TC_IL-NiII (i.e., mainly with visible (VIS) transmittance changing) films were numerically analysed at three transition temperatures (Tt): 20, 30 and 40°C. The pairwise cooperation permutations resulted in 9 pairs of scenarios in total. They were classified into three groups: 1) the cooperative cases with VO2_Nano and TC_IL-NiII having the same transition temperatures of 20°C, 30°C and 40°C were labelled as ‘Same Tt20’, ‘Same Tt30’ and ‘Same Tt40’, respectively; 2) the cooperative cases with VO2_Nano having lower transition temperatures than that of TC_IL-NiII were labelled as ‘NIR_20 VIS_30’, ‘NIR_20 VIS_40’, and ‘NIR_30 VIS_40’, respectively. It means that, with the temperature increasing, the NIR transmittance would decrease firstly, and then the visible transmittance decreases at a higher temperature. For instance, ‘NIR_20 VIS_30’ represents that the VO2_Nano film with Tt of 20°C is cooperating with TC_IL-NiII film with Tt of 30°C; 3) accordingly, the cooperation cases with TC_IL-NiII having lower transition temperatures than VO2_Nano were named as ‘VIS_20 NIR_30’, ‘VIS_20 NIR_40’, and ‘VIS_30 NIR_40’. A reference case with standard double glazing (DG) was investigated, in order to find out the advantages and disadvantages caused by the different TC cooperative implement cases.
Fig. 1. Spectral transmittance of VO2_Nano (a) and TC_IL-NiII (b)
3. Results and discussion 3.1. Energy performance and UDI distributions The energy consumption and UDI distribution that affected by the three groups of cooperative cases between the two typical TC materials are shown in Fig. 2. When the pairwise TC films have the same transition temperature, cooperative case ‘Same_Tt30’ leads to the most significant energy saving potential in Beijing, with a 14.57% reduction of energy consumption when compared with DG. However, in Shanghai, the most appropriate cooperation case is ‘Same Tt40’, reaching maximum energy conservation of 13.50% when compared with DG. In Guangzhou, with the increase of transition temperature, the decrease of lighting demand is complementary to the increase of cooling demand, resulting in similar overall energy consumption for ‘Same_Tt20’, ‘Same_Tt30’ and ‘Same_Tt40’. As can be seen in Fig. 2 (b) (d) (f), in Beijing and Shanghai, ‘Same Tt 20’ case results in the highest percentage of working hours falling into UDI500-2000lux (a useful bin meeting the illuminance requirement of working environment, 500 lux < illuminance value < 2000 lux), which is 48.12% and 63.49%, respectively. While in Guangzhou, the highest UDI500-2000lux of 64.58% occurs when implementing the ‘Same Tt 30’ case.
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‘NIR_20 VIS_30’, ‘NIR_20 VIS_40’, and ‘NIR_30 VIS_40’ cases indicate that NIR solar radiation transmitted into the room got the adjustment earlier than that of visible solar radiation with the temperature increasing. When comparing with DG, the results present that ‘NIR_30 VIS_40’ is the most energy effective case under the climates of Beijing and Shanghai with an energy saving of 17.5% and 15.55%. However, the improvement in UDI500-2000lux offered by ‘NIR_30 VIS_40’ is restricted. In Guangzhou, ‘NIR_20 VIS_30’ provides the most significant energy reduction. Meanwhile, the percentage of working hours within the illuminance range from 500lux to 2000 lux is approaching 67%, which is higher than any other cases in this group.
Fig. 2. Energy consumption and annual UDI levels at sensor 1 affected by TC windows of scenario III with different transition temperatures and lower visible transmittance at tinted state under three climates.
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‘VIS_20 NIR_30’, ‘VIS_20 NIR_40’, and ‘VIS_30 NIR_40’ cases indicate that visible light transmitted into the room got the adjustment earlier than that of NIR solar radiation with the temperature increasing. Fig. 2(a) (c) (e) shows that in Beijing and Shanghai the case of ‘VIS_30 NIR_40’ induces the most energy saving when compared with DG, but less improvement of UDI500-2000lux, than the other two cases. However, in Guangzhou, ‘VIS_20 NIR_30’ case leads to the most energy saving (13.68% energy reduction when compared with DG), and the highest value of UDI500-2000lux (~65%) among the three cases. 3.2. Further comparison between cooperative cases and individual cases In order to further explore the significance of cooperative implementing, the percentage of energy saving and improvement of daylighting performance (UDI500-2000lux) affected by cooperative cases of VO2_Nano and TC_IL-NiII films were compared with cases of applying each film individually at various transmission temperatures. And the results were shown in Table 2, green area shows the performance of each cooperative implement case, while yellow area presents that of each individual VO2_Nano window case, and the blue shows individual TC_IL-NiII window case. Table 2: Energy saving and improvement of UDI500-2000lux at sensor I affected by the revised TC windows and cooperative cases (* Better performance than revised VO2_Nano or revised TC_IL-NiII; ** Better performance than revised VO2_Nano and revised TC_IL-NiII)
In Beijing, 4 (i.e., marked with two stars in green area) out of 9 cooperative cases have an improvement in energy and daylighting performance compared with each of the individual case. Among that, the cooperation between VO2_Nano Tt40 and TC_IL-NiII Tt30 (i.e., VIS_30 NIR_40) has the most significant increase of energy saving (2.46%) and improvement of UDI500-2000lux (15.96%) when compared with applying VO2_Nano Tt40 window individually. It reveals that adjusting visible transmittance at a lower temperature than NIR transmittance under the climatic condition of Beijing is more effective than any other cooperative cases.
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In Shanghai, 2 out of 9 cooperative cases have better energy and daylighting performance than using each of the individual TC_IL-NiII or VO2_Nano windows respectively. The TC_IL-NiII Tt30 cooperatively implementing with the VO2_Nano Tt40 (i.e., VIS_30 NIR_40) results in 14.06% increase of energy saving, and 38.69% increase of UDI500-2000lux, which is the most effective case for both energy and daylighting. Meanwhile, it can be seen that under the climatic conditions of Shanghai, most of the individual VO2_Nano cases perform more energy efficient than cooperative cases, while the improvement in UDI500-2000lux is the most significant contribution of cooperative cases. It means that the properties of individual VO2_Nano window are suitable for Shanghai. In Guangzhou, 5 out of 9 cooperative cases are detected to be significant for both energy and daylighting improvement. The TC_IL-NiII Tt40 cooperating with VO2_Nano Tt30 results in the improvement of energy saving when compared with each individual case with energy saving increased by 3.11%, while the increase of UDI500II 2000lux is restricted by 2.37%. On the other hand, the cooperation between TC_IL-Ni Tt30 and VO2_Nano Tt20 or Tt30 case leads to improvement in energy saving by up to 1.97%, while the UDI500-2000lux is significantly increased by 30%. To sum up, in Guangzhou, reducing NIR transmittance at a lower temperature than reduction of visible transmittance is able to improve both energy and daylighting performance. 4. Conclusions Building simulation conducted by EnergyPlus shows that cooperation between TC_IL-NiII and VO2_Nano films enables a further improvement in both energy and daylighting performance. Depending on climatic conditions, the optimal cooperative scenarios are varying: In Beijing, ‘VIS_30 NIR_40’ is the best case, i.e., reducing the oversupplied daylighting on cold days, and both overlit and overheat on hot days; In Shanghai, both improved VO2_Nano working alone and ‘VIS_30 NIR_40’ are all suitable due to its moderate warm climates; In Guangzhou, adjusting the overheat as a matter of priority is beneficial to both energy and daylighting performance. Acknowledgements This work was supported by the Faculty of Engineering, the University of Nottingham through a PhD studentship to Runqi Liang. References [1] [2] [3] [4] [5] [6] [7] [8] [9]
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