Investigation on energy consumption of public buildings in Tianjin

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Energy Procedia 158 Energy Procedia 00(2019) (2017)3427–3432 000–000 www.elsevier.com/locate/procedia

10th th

International Conference on Applied Energy (ICAE2018), 22-25 August 2018, Hong Kong, 10 International Conference on Applied Energy China(ICAE2018), 22-25 August 2018, Hong Kong, China

Investigation on energy consumption of public buildings in Tianjin The on 15thenergy International Symposium on of District Heating and Cooling Investigation consumption public buildings in Tianjin Hongting Maaa, Chen Lia,a,*, Junwen Laiaa, Fan Yangaa, Zihao Liaa Hongting , Chen Li *,of Junwen , Fan Yang , Zihao Li Assessing theMafeasibility usingLaithe heat demand-outdoor a

School of Environmental Science and Engineering, Tianjin University, Tianjin 300350, China

School of Environmental Science Engineering, Tianjin University, Tianjin China temperature function for a and long-term district heat300350, demand forecast a

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a

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b

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*, A. Pina , P. Ferrão , J. Fournier ., B. Lacarrière , O. Le Corre Abstract I. Andrić Abstract a Center forand Innovation, Technology anddata Policy Superior Técnico, Rovisco Pais 1,According 1049-001 Lisbon, BasicIN+ information energy consumption of Research 50 public- Instituto buildings in Tianjin haveAv. been collected. to thePortugal statistical b Veolia Recherchedata & Innovation, 291buildings Avenue Dreyfous Daniel, 78520 Limay, France 2in Tianjin Basic information and energy consumption of 50 public have been collected. According to the statistical consumption results, in 2016, the total building area of 50 samples is 1582628.53 m , the total power and comprehensive energy c Département Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France 4the total building power comprehensive energy consumption results, in 2016, areatce. of 50 1582628.53 m2, the total kWh and 41686.58 Thesamples averageispower and comprehensive energyand consumption per building area value is is 11562.91×10 2 and26.34 41686.58 tce.(m The average and comprehensive energy consumption per consumption. building area value is is 11562.91×10 73.06 kWh/ (m422kWh ·a) and kgce/ ·a) . The power building function has obvious influence on energy Among 73.06 kWh/ (mschool ·a) and 26.34 and kgce/ (m2·a) . The building obvious influence on energy consumption. Among office building, building hospital building, hospitalfunction buildinghashas the highest energy consumption. In addition to office building, building and hospital building, building has the energy consumption. In addition to building function,school the type of cooling and heating source,hospital construction structure andhighest the performance of building envelope have Abstract building function, the type of cooling and heating source, construction structure and the performance of building envelope have obvious effect on energy consumption. obvious on energy consumption. Districteffect heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the Copyright © 2018 Elsevier Ltd. All rights reserved. greenhouse gas emissions fromby theElsevier building sector. These systems require high investments which are returned through the heat © 2019 The Authors. Published Ltd. Copyright © 2018 Elsevier Ltd. Allresponsibility rights reserved. International Conference on Applied Selection and peer-review under of scientific committee of the heat 10th demand sales. Due to the changed climate conditions andthebuilding renovation policies, in the future could decrease, This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) th Selection andthepeer-review under period. responsibility of the scientific committee of the 10 International Conference on Applied Energy (ICAE2018). prolonging investment return Peer-review under responsibility of the scientific committee of ICAE2018 – The 10th International Conference on Applied Energy. Energy (ICAE2018). The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand

Keywords: building;ofEnergy consumption; saving(Portugal), suggestion was used as a case study. The district is consisted of 665 forecast. Public The district Alvalade, locatedEnergy in Lisbon Keywords: Public building; Energy consumption; Energy saving suggestion

buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were 1.compared Introduction with results from a dynamic heat demand model, previously developed and validated by the authors. 1.The Introduction results showed that when only weather change is considered, the margin of error could be acceptable for some applications of China's economy the acceleration of urbanization, theafter construction is (theWith errorthe in rapid annualdevelopment demand was lower than 20% for alland weather scenarios considered). However, introducingindustry renovation With the ofup China's economy and the the acceleration ofrenovation urbanization, construction is scenarios, therapid error value to 59.5% (depending on the weatherofand combination considered). also changing withdevelopment eachincreased passing day. However, with increase total amountscenarios of the buildings, more industry and more also with coefficient each passing day. on However, with the increase of transportation total buildings, more and more The changing value of slope increased averagebuilding, within theindustry range ofand 3.8% up amount to 8% perof decade, that constituted corresponds to the energy consumption will be consumed. In China, have already three decrease in theof number of consumption heating hours [1]. of during theindustry heating season (depending onhave the combination ofbuildings weather and energy consumption will be consumed. In22-139h China, building, and transportation already constituted three major sources energy Statistics suggest that the total construction area of existing in 2 consumption renovation considered). the [1]. otherStatistics hand, intercept increased for perof decade (depending on in the major sources of energy that the total area existing buildings , and it isOnstill growing at function a suggest rate of 2 billion m2 aconstruction year7.8-12.7% [2], building energy consumption China is 46scenarios billion m 2 values suggested could be used to modify the function 2 parameters for the scenarios considered, and coupled scenarios). The andtotal it is social still growing a rate consumption of 2 billion m [2], energy buildingconsumption energy consumption China is 46 accounts for billion 28.5% m of , the terminalatenergy [3].a Inyear China, per unit improve the estimations. accounts foraccuracy 28.5% of of heat the demand total social terminal energy consumption [3]. In China, energy consumption per unit © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and * Corresponding author. Tel.: +86-18222123710. Cooling. * E-mail Corresponding Tel.: +86-18222123710. address:author. [email protected] E-mail address: [email protected] Keywords: Heat demand; Forecast; Climate change

1876-6102 Copyright © 2018 Elsevier Ltd. All rights reserved. 1876-6102 Copyright © 2018 Elsevier Ltd. All of rights reserved. committee of the 10th International Conference on Selection and peer-review under responsibility the scientific SelectionEnergy and peer-review under responsibility of the scientific committee of the 10th International Conference on Applied (ICAE2018). 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.2019.01.932

Hongting Ma et al. / Energy Procedia 158 (2019) 3427–3432 Chen Li et al./ Energy Procedia 00 (2018) 000–000

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construction area in public building is more than twice as much as residential building [4]. Thus, public buildings account for a greater proportion of building energy consumption . Jiang [5] analyzed the current situation of building energy consumption in China and put forward energy saving targets such as reducing heating energy consumption of northern buildings. Wan et al. [6] took 16 public buildings in Wuhan as an example and analyzed energy consumption characteristics by using the method of energy consumption calculation and decomposition. Li et al. [7] set up an evaluation index system of operating energy consumption of air conditioning system in public buildings based on the actual building energy consumption and operation data which can be used for reference in optimizing operation management of air conditioning system. Through detailed investigation and test of lighting system of an office building, Liu [8] analyzed the characteristics of lighting energy consumption, and put forward corresponding suggestions for energy saving. 2. Basic information of 50 public buildings In order to investigate the current situation of energy consumption of public buildings in Tianjin, the authors conducted energy audit. By field research, basic information and energy consumption data of 50 public buildings have been collected. In the present work, 50 samples include 27 office buildings, 12 school buildings and 11 hospital buildings, accounting for 54%, 24% and 22 %, respectively. All the surveyed samples can be segmented into brick-concrete structure, concrete shear wall, frame structure, steel structure. According to construction structure, each occupies 44 %, 30 %, 14 %, 12 %, respectively. Among 50 public buildings, 18 buildings were built before 2000, however, 32 buildings were built after 2000, accounting for 36 % and 64 %, respectively. There are 28 buildings with construction area less than 15000 m 2, the other 22 buildings are more than 15000 m2. The distribution proportion according to construction structure, age and area are shown in Fig. 1a, b and c.

(a)

(b)

Chen Li et al./ Energy Procedia 00 (2018) 000–000 Hongting Ma et al. / Energy Procedia 158 (2019) 3427–3432



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(c) Fig. 1. Distribution proportion of construction structure, age and area

Based on the statistics, the heating source mainly contains municipal heating, coal-fired boiler, gas-fired boiler, ground source heat pump and direct-fired machine. Cooling source mainly contains split air conditioning, VRV, water chiller unit, ground source heat pump and direct-fired machine, distribution frequency are shown in Fig. 2a and b.

(a)

(b) Fig. 2. Distribution frequency of heating source and cooling source

According to Fig. 2, municipal heating is the most commonly heating source used, taking up 48%, which is followed by gas-fired boiler, taking up 18%. Split air conditioning is the most commonly used cooling source, taking up 54%, which is followed by water chiller unit, taking up 14%. 3. Comparison of energy consumption of public buildings with different functions 3.1. Total energy consumption of 50 public buildings In 2016, the total building area of 50 samples is 1582628.53 m2, the total power and comprehensive energy consumption is 11562.91×104 kWh and 41686.58 tce, respectively. Through calculation, average power and comprehensive energy consumption per building area value is 73.06 kWh/ (m2·a) and 26.34 kgce/ (m2·a). 3.2. Power and energy consumption of different functional buildings There is a great difference in energy consumption because of functions of public buildings. The power consumption of office buildings, school buildings and hospital buildings per building area ranges from 11.66 to 310.19 kWh/ (m2·a), 6.85 to 83.12 kWh/ (m2·a), 41.70 to 1103.54 kWh/ (m2·a), respectively. The comprehensive energy consumption of office buildings, school buildings and hospital buildings per building area ranges from 2.48to 107.22 kgce/ (m2·a), 4.32 to 31.39 kgce/ (m2·a), 16.56 to 305.24 kgce/ (m2·a), respectively. Table 1 shows more detailed energy consumption data.

Hongting Ma et al. / Energy Procedia 158 (2019) 3427–3432 Chen Li et al./ Energy Procedia 00 (2018) 000–000

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Table 1. Energy consumption of different functional public buildings. Building function

Total building area (m2)

Total power consumption(kW h)

Average power consumption per building area (kWh/ (m2·a))

Total comprehensive energy consumption (tce)

Average comprehensive energy consumption per building area (kgce/ (m2·a))

Office

570397.22

3279.38×104

57.49

16490.14

28.91

605650.91

2277.53×10

4

37.60

9199.63

15.19

6006.00×10

4

147.72

15996.80

39.34

School Hospital

406580.40

According to Table 1, it is obvious that the function of public buildings has a significant impact on building energy consumption. Average power and comprehensive energy consumption per building area of hospital buildings is the highest among three building types, which is followed by office buildings, and school buildings is the least. The main reasons for the high energy consumption in hospital buildings are as follows:  Hospitals have numbers of medical equipment, although the service time of equipment is short, its safeguard system needs to be on standby for a long time which consumes electric energy a lot [9].  Hospitals have many operating rooms and clean rooms with higher requirements for temperature, relative humidity, wind speed and cleanliness. As a result, air conditioning and ventilation system has greater load.  Because patients have higher requirements for comfort, service time of heating and air conditioning is longer each year. Thus, heating and air conditioning energy consumption is also higher. 4. Comparison of two school public buildings Two school public buildings are selected as examples to analyze the influence of some other factors on the energy consumption. Table 2 shows detailed information of two school public buildings. Table 2. Information of two school public buildings.

Construction age 2

Construction area(m )

School A

School B

2011

1993

29702

27124

256.33×104

672.55×104

Comprehensive energy consumption(kWh) Comprehensive energy consumption per building area(kWh/ (m2·a)) Construction structure Is there thermal insulation layer on building envelope? Glass type

86.30

247.95

Concrete shear wall

Brick-concrete structure

Yes

No

Hollow glass

Ordinary single glass window

Heating source

Ground source heat pump

Municipal heating

Cooling source

Ground source heat pump

Split air conditioning

According to Table 2, comprehensive energy consumption per building area of school A is 65.18% lower than school B. The main reasons are as follows:  School A uses ground source heat pump to replace the traditional cooling and heating source. It consumes a small amount of electricity to realize the transfer from shallow ground thermal energy to high-grade thermal energy [10] which has advantages of eco-friendly, high efficiency, energy saving and so on.  Construction structure of school B is brick-concrete without thermal insulation layer on building envelope. However, school A is concrete shear wall with thermal insulation layer which has a better heat insulation effect.  Glass type of school A and B is hollow glass and ordinary single glass window, respectively. At 20℃, coefficient of thermal conductivity of air is 0.026 W/ (m·K), while that of ordinary single glass is 0.76 W/ (m·K), the ratio is



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1:29 [11]. Hollow glass binds two (or more) pieces of glass to the sealing and fills the dry air between them, leading to the increase of thermal resistance, which is conducive to energy saving. 5. Energy saving suggestions of public buildings According to the investigation, it is found that there are some common problems in energy management and utilization. Energy saving measures can be taken to further reduce consumption, including:  To formulate the energy consumption quota and assessment methods, adopt appropriate penalties and incentives, and improve the level of energy management.  To train energy administrators and operators regularly to improve their professional ability and skills.  Metering device should be added to measure separately the energy consumption of air conditioning, office electricity (including lighting and socket), integrated service system to tap energy saving potential.  In order to reduce the energy loss of valve throttling, the circulating pump should be equipped with frequency converter. Since the power consumption of the pump is proportional to the third power of the rotational speed, the electric energy consumption can be reduced obviously by using the frequency converter in circulating pump.  To clean the filter of VRV and split air conditioning regularly, which can strengthen heat transfer and air flow effect.  The operators should be able to reduce or raise the outlet temperature of heat pump according to the climate change. By optimizing the operation management, the performance coefficient of the heating or cooling source can be improved and the power consumption can be reduced. 6. Conclusions Some conclusions can be drawn by auditing and analyzing energy consumption data of 50 public buildings in Tianjin, they are as follows:  Average power consumption per building area value of 50 public buildings is 73.06 kWh/ (m2·a). But the value of office buildings, school buildings and hospital buildings is 57.49 kWh/ (m2·a), 37.60 kWh/ (m2·a), 147.72 kWh/ (m2·a), respectively.  Different building functions have obvious influence on energy consumption. Average comprehensive energy consumption per building area value of 50 public buildings is 26.34 kgce/ (m2·a). But the value of office buildings, school buildings and hospital buildings is 28.91 kgce/ (m2·a), 15.19 kgce/ (m2·a), 39.34 kgce/ (m2·a), respectively.  It displays that, besides the function of building, the type of cooling and heating source, construction structure and the performance of building envelope also have effects on energy consumption through comparison of two school public buildings.  Public buildings in Tianjin still have great energy saving potential. They can set up reward and punishment mechanism, train operators regularly, carry out itemized metering, install frequency converter in circulating pump, clean the filter of VRV and split air conditioning regularly and optimize operation strategy of equipment to further reduce building energy consumption. Acknowledgements This research was funded by the National Natural Science Foundation of China(51576137). References [1] Qi Fu. Energy consumption of buildings in China and effective ways to save energy. Building Technology Development, 2017, 44(01): 150151. [2] Qingqin Wang, Rongxin Zhu. HVAC. Construction Science and Technology, 2016(24): 18-20. [3] Jianli Gao, Jiaxi Lou. Investigation and analysis of building energy consumption. Energy Research and Utilization, 2015(05): 48-49+52. [4] Ping Jiang. Analysis of national and local energy-efficiency design standards in the public building sector in China. Energy Sustain, Dev. 15 (2011) 443–450.

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[5] Yi Jiang. Study on building energy saving strategy in China. Chinese Engineering Science, 2011,13(06):30-38. [6] Lida Wan, Qian Liu, Anbang Li, et al. Analysis of energy consumption characteristics of public buildings in Wuhan. Refrigeration and Air Conditioning, 2016,30(02):211-216. [7] Haoru Li, Xiaofeng Li, Ying Wang. Study on energy consumption evaluation method of air conditioning system in public buildings. HVAC, 2017,47(07):15-20+26. [8] Zhuxiong Liu. Analysis on energy efficiency of office building lighting system and energy saving suggestions. Fujian Construction Science and Technology, 2012(05):61-62+73. [9] Lingling Liu. Analysis of energy use in Beijing hospital and diagnosis of energy saving. China Refrigeration Institute air conditioning heat pump Specialized Committee: China Refrigeration Society, 2010: 1. [10] Tong Wu, Yuying Liu, Zhe Dong, et al. Research and application status of ground source heat pump. Refrigeration Technology, 2014, 34(04): 71-75. [11] Shuting Tong, Xiaoyun Feng. Heat transfer characteristics of insulating glass and its influencing factors. Journal of Building Materials, 2004(01): 52-57.