Field Test Analysis of a Urban Sewage Source Heat Pump System Performance

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World Engineers Summit – Applied Energy Symposium & Forum: Low Carbon Cities & Urban Energy Joint Conference, WES WES-CUE 2017, 19–21 21 July 2017, Singapore World Engineers Summit – Applied Energy Symposium & Forum: Low Carbon Cities & Urban Energy Joint Conference, WES WES-CUE 2017, 19–21 21 July 2017, Singapore Field Test The Analysis of a Urban Sewage Source Heat Pump System 15th International Symposium on District Heating and Cooling

Field Test Analysis of a Urban Sewage Source Heat Pump System Performance Assessing the feasibility of using the heat demand-outdoor Performance a, a a Qunli Zhang *,Zhiming ,Zhiming ,ChaohuiYin ,Qianheat Niea,Liwen Jinbforecast temperature function for aWang long-term district demand a

Qunli Zhang a,*,Zhiming ,Zhiming Wanga,ChaohuiYina,Qian Niea,Liwen Jinb I. Andrić *, A. Pina , P. Ferrão , J. Fournier ., B. Lacarrière , O. Le Corre

Beijing Municipal Key Lab of Heating, Gas Supply, Ventilating and Air Conditioning Engineering, Beijing Advanced Innovation Center for a,b,c a a b c c Future Urban Design,Beijing Beijing University of Civil Engineering and Architecture Architecture,Beijing ,Beijing and 100044,China b a Beijing Key Lab of Heating, Gas Supply, VentilatingBuilding and Air Environment Conditioningand Engineering, Advanced Innovation for Group of Municipal Building Environment and Sustainability Technology, EquipmentBeijing Engineering, Xi’an JiaotongCenter U University, a Future UrbanTechnology Design,Beijing Beijing of Civil Engineering and Architecture Architecture,Beijing 100044,China Xi’an and 710049,China IN+ Center for Innovation, and University Policy Research - Instituto Superior Técnico, Av.,Beijing Roviscoand Pais 1, 1049-001 Lisbon, Portugal b b Group of Building Environment and Sustainability Building Environment and Equipment Engineering, University, Veolia Recherche & Technology, Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France Xi’an Jiaotong U c Xi’an and 710049,China Département Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France

Abstract Abstract Abstract The sewage flow rate of the urban drainage system is relatively large and generally stable, its sewage temperature

range varies relatively lightly and maintains 10~15 10~15℃ in winter. The sewage in the drainage system can be the low The sewage flow ratefor of are thelding urbanheating drainage is relatively andthegenerally stable,solutions itscan sewage temperature District heating networks commonly addressed in the literature aslarge one heat of most technology effective for decreasing the grade thermal source building andsystem cooling. Sewage source pump efficiently extract range variesgas relatively lightly andfrom maintains 10~15 10~15℃ in drainage winter. The sewage the drainage can beThe the low from the building These systems require high investments which aresystem returned through the heat orgreenhouse discharge theemissions amount of heat thesector. sewage in the system for in building heating or cooling. field grade for building lding heating andand cooling. source heat pump pump technology can efficiently extract sales. Dueactual to source theoperation changed climate conditions building renovation policies, heat demand in the future decrease, test ofthermal the thermal performance of the Sewage sewage source heat were carried out and could investigated. orprolonging discharge amount of heatperiod. from thewere sewage in the drainage system heating cooling. The field investment The sewagethethe source heat return pump system continuously measured for for 72 building hours. Based onorthe test datum, the test theCOP actual thermal performance sewage source heat were carriedoffunction out andfor investigated. Theofmain scope this paper is to assess the feasibility ofthe using the between heat demand – pump outdoor temperature heatenergy demand average ofofoperation the heat pump was 4.5. The of relationship energy consumption system and The sewage heat pumparesystem were continuously measured hours. on theistest datum, the forecast. Thesource district of Alvalade, located in Lisbon (Portugal), wasthat used aspump a72 case The district consisted 665 consumption of transportation analyzed. The analysis shows thefor ofstudy. this Based system cannot match theofload average COP of the heat pump was 4.5. The relationship between energy consumption of system and energy buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district change well and the use of variable frequency pump can improve the energy efficiency of the system. Before the use consumption ofsource transportation aresystem, analyzed. analysiscoal showsTo thatboiler the pump of thisobtained system cannot match the load renovation scenarios (shallow, intermediate, deep). estimate theair-cooled error, heat demand values were of the sewage urcewere heatdeveloped pump theThe traditional coal-fired and cooled chiller are the heating and change well andresults the ofbuilding. pump can improve the energy ofand the authors. system. Before the use compared with from avariable dynamic frequency heat demand model, previously developed andefficiency validated the cooling system of use this Compared with the traditional coal coal-fired boiler by air-cooled cooled chiller, the of theresults sewage urce pump system, the traditional coal coal-fired boiler cooled chiller are heating and The showed thatheat when only weather change is considered, thesaving, margin of and errorair-cooled could beenvironmental acceptable for the some applications advantages of source sewage source heat pump system in energy economy and nvironmental protection are cooling of demand this building. Compared with the traditional coal-fired andtype air-cooled cooled the (the errorsystem in annual was than 20% for all original weather scenarios considered). However, after introducing renovation analyzed. The results show that:lower Compared with the system, coal direct irect heat boiler exchange sewage chiller, source heat advantages ofcan sewage source heat pump system in energy economy andoperatin environmental nvironmental are scenarios, the error value53% increased upprimary to 59.5% (depending on the saving, weather scenarios combination pump system save of the energy consumption, reduceand therenovation annual operating g cost by protection 11%,considered). increase analyzed. results show that: Compared with original system, direct irect exchange typethat sewage source heat Theinitial valueThe of slope coefficient increased on average within the range of 3.8% upheat to 8% per decade, corresponds to the the investment by a factor of 14.3%, and the the payback period of incremental investment is about 4.7 years. pump system save 53% of thehours primary energyduring consumption, reduce annual operating g costthe bylocal 11%, increase decrease in thecan number heating of 22-139h thecapital heating seasonthe (depending on the combination of weather and This method not only of has better energy saving, saving benefit, but also operatin can reduce pollutant the initial investment byenvironmental a factorOnofthe 14.3%, andreduction the payback period of incremental investment is about 4.7 years. renovation scenarios considered). other hand, function intercept increased for 7.8-12.7% per decade (depending on the emission, n, and has better emission benefits. This method not only has better energy saving, saving capital also can the local pollutant coupled scenarios). The values suggested could be used to modify thebenefit, function but parameters for reduce the scenarios considered, and © 2017 Authors. Published by Ltd. emission, n,the and has better environmental emission reduction benefits. improve accuracy of heat demand estimations. © 2017 The The Authors. Published by Elsevier Elsevier Ltd. Peer-review under responsibility of the scientific committee of the World Engineers Summit – Applied Energy Symposium & Forum: Low Authors. Carbon Cities & Urban Energy Joint Conference. ©©2017 2017The The Authors.Published PublishedbybyElsevier ElsevierLtd. Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. * Corresponding author. Tel.: 13522898182; E-mail address: [email protected] Keywords: Heat demand; Forecast; Climate change * Corresponding author. Tel.: 13522898182; E-mail address: [email protected] Ltd. 1876-6102© 2017 The Authors. Published by Elsevier Ltd

Peer-review review under responsibility of the scientific committee of the World Engineers Summit – Applied Energy Symposium & Ltd. 1876-6102© The Authors. by Elsevier Forum: Low2017 Carbon Cities &Published Urban Energy JointLtd Conference Conference. Peer-review review under responsibility of the scientific committee of the World Engineers Summit – Applied Energy Symposium & 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Forum: Low Carbon Cities & Urban Energy Joint Conference Conference.

Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the World Engineers Summit – Applied Energy Symposium & Forum: Low Carbon Cities & Urban Energy Joint Conference. 10.1016/j.egypro.2017.12.660

2

Qunli Zhang/ Energy Procedia 00 (2017) 000–000

Peer-review under responsibility of the scientific committee of /the World Engineers Summit – Applied Energy Symposium & 132 Qunli Zhang et al. Energy Procedia 143 (2017) 131–136 Forum: Low Carbon Cities & Urban Energy Joint Conference.

Keywords: Sewage source heat pump, Heating, Cooling, Energy saving;

1. Introduction Urban sewage water temperature and rate of flow stable throughout the year, and the characteristics of the temperature warm in winter and cool in summer[1]. Urban sewage contains rich resources of low grade thermal energy[2]. Chinese 13th Five Year Plan points out in the hot summer and cold winter areas to actively push the sewage source heat pump[3].The sewage source heat pump is a heat pump as cold heat source by sewage , through a small amount of electricity heating and cooling for the building[4].The sewage source heat pump system has significantly energy saving efficiency. According to the way of sewage heat exchanger, the sewage source heat pump system can be divided into direct sewage source heat pump system and indirect sewage source heat pump system[5]. Indirect sewage source heat pump system is a kind of system that is not directly connected with heat pump heat pump, first, the sewage and clean water heat exchange, then the intermediary water into the heat pump heat pump. The direct sewage source heat pump system is the system of the heat transfer of the sewage directly into the evaporator or condenser of the heat pump heat pump. 2. Direct heat exchange sewage source heat pump system scheme The sewage source heat pump system for the hotel building air conditioning system, located in Changchun of the cold area. The hotel construction area of 15 thousand square meters, the main purpose is to provide high standard rooms. Prior to the transformation of the project, the use of coal-fired boiler room heating, cooling air cooling chillers in summer;now direct heat exchange sewage source heat pump system for heating / cooling. The reconstructed heat pump is shown in Figure 1, the system flow chart is shown in Figure 2.

Fig.1 Sewage source heat pump heat pump

Fig.3 Sewage temperature and outdoor temperature in summer

Fig.2 Direct sewage source heat pump system

Fig.4 Sewage temperature and outdoor temperature in winter

Sewage flow and sewage temperature have a great influence on the operation of sewage source heat pump system. There is a diameter of 1000mm trunk sewer distance 15 meters from the building. The actual measurement of the minimum flow rate is 1000m3/h-1500m3/h. In winter, the temperature of sewage water is 12 ~13℃, and the temperature in summer is 22~24 ℃, pH value is neutral. After operation, the inlet temperature and outdoor air



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temperature in summer and winter were tested. The sewage average temperature in summer is 21 ℃, which is higher than the outdoor air temperature of 7℃, 7 up to 13~14 ℃, as shown in figure 3.In .In winter, the average temperature of the sewage temperature is 12.9℃, 12.9 which is higher than the average outdoor temperature perature by as much as 29℃, as shown in figure 4. 3. Test and performance analysis of sewage source heat pump system 3.1. Test method After the operation of the system is stable, the system is tested in summer ummer cooling condition and winter heating condition. The test includes: indoor ndoor and outdoor temperature, sewage ewage inlet and outlet temperature and flow rate, chilled water supply and return water temperature and flow rate, heating eating circulating water supply and return water temperature and flow rate, heat eat pump power consumption and pump power consumption. 3.2. Analysis of refrigeration condition of sewage source heat pump system

Fig.5 5 Comparison of test results of unit data

Fig.6 Refrigeration condition heat pumps and system

Figure 5 is the change curve of the system COP and unit COP calculated according to the test results of the system. We can see from figure 5 the average COP of the heat pump is 6.0 and the average COP of the system is 3.9.It can be seen that the sewage source heat pump system works wo well in refrigeration condition.

Fig.7 Heat pump, pump and system power in refrigeration efrigeration condition

efrigeration condition Fig.8 Heat pump power and pump power in refrigeration

As can be seen from Figure 5, the unit cooling capacity of up to 319.7kW, the minimum cooling capacity of 198.5kW, the difference between the two 61%;The system power consumption is not a change in the day, because of the constant flow of water pump operating constant power consumption of about 25.2kW.As can be seen from Figure 8, the he pump power consumption accounts for about 34% of the system power consumption, while the general air-conditioning conditioning pump power consumption accounted for 15%~20%.It 15%~20%.It can be seen that the pump power consumption in the system accounts for a large share of the system power consumption, it is recommended to use variable frequency pump to match the system load load changes in each period, which is conducive to the improvement of system performance.

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3.3. Analysis of heating condition of sewage source heat pump system Through the test, the average winter water temperature is 12.9℃, 12.9 , through measuring the sewage outlet outl temperature, the measured average winter heat temperature of 2.6℃, 2.6 , the maximum temperature and minimum temperature difference of heat is 0.5℃,, within twenty-four twenty four hours of heat temperature difference is basically stable, as shown in figure 9.

Fig.9 Heat extraction temperature difference of sewage ewage in winter

Fig.10 Heating condition heat pumps and system COP

Fig.11 Relationship between heat pump cop and sewage inlet temperature

Fig.12 Relationship between heat pump COP and circulating water return temperature

According to the test data, the COP of the sewage source heat pump unit and the system are calculated, and the average COP of the direct heat exchange hange sewage source heat pump unit is 4.5, and the average COP of the sewage source heat pump system is 3.7, as shown in Figure 10.It can be seen that the sewage source heat pump system has good operation effect in winter.

temperature the Figure 11 is the relationship between the sewage source heat pump heat pump and sewage inlet temperature. unit COP increases with increasing inlet temperature. temperature. Figure 12 is the relationship between heat pump COP and circulating water return temperature. From the graph we can see that the higher the circulating return water temperature, the lower the heat pump cop. 4. Economic

energy gy saving analysis

Because urban sewage is a good cold and heat source，compared source compared with the traditional heating and cooling system, the sewage source heat pump system has great energy saving and low operating cost. As a kind of clean energy, urban sewage can reduce the burning of fossil fuels and the emission of pollutants[7].Sewage source heat pump system is compared with traditional coal-fired fired boiler and air-cooled air cooled chiller in economical efficiency, energy saving and environmental protection. 4.1.Energy efficiency analysis fired boiler, the daily coal oal saving of the sewage source heat pump heat pump Compared with the traditional coal-fired in the heating season is:



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Qd 1 1 (  ) qe  g eCOPr

(1)

Ql 1 1 (  ) 3 3.6 10  a COPl

(2)

M1  M g  M W 

Where: M1 is the daily coal saving, kg; Mg is daily consumption of coal of traditional coal fired boiler, kg; Mw is daily consumption of coal of sewage source heat pump system, kg; Qd is daily heating capacity,8.424×107kJ;qe is calorific value of standard coal,29.31×103kJ/kg[8];ηg is traditional coal-fired boiler efficiency,60%[8];ηe is power input efficiency,30%[8];COPr is 4.5. Compared with the air-cooled chiller, the daily power saving of the sewage source heat pump heat pump in the cooling season is:

ΔD  D f  Dw 

Where: ΔD is daily save electricity in summer, kWh; Dfis air cooled chiller daily power consumption, kWh; Ql is daily cooling capacity,3.888×107kJ;εais refrigerating performance coefficient of air cooled chiller, εa=4[9];COPl, 6. The daily coal saving of the sewage source heat pump heat pump in the cooling season is:

M2 

ΔD  3600 q e  f

(3)

Where: M2 is the daily coal saving in the cooling season, kg; ηf is primary energy efficiency,35%[8]. According to the calculation, the sewage source heat pump system compared with the traditional coal-fired boiler can save 2661.1kg standard coal one day in heating condition, compared with air-cooled chiller can save electricity 900kWh (315.8kg standard coal) one day in cooling condition. Changchun heating season is 165 days and cooling season is 90 days ,one year can save standard coal 467503.5kg.It can be seen that the annual primary energy consumption of sewage source heat pump system is 53% lower than that of traditional coal-fired boiler and aircooled chiller system. 4.2 Economic benefit analysis Compared with air cooling chiller, sewage source heat pump system can save operating cost in cooling season is: Cl  D  P  n l (4) Where: Cl is cost saving in cooling season, yuan; P is electricity price,0.525yuan/kWh; nl is days of cooling season, 90 days. Compared with the traditional coal-fired boiler, sewage source heat pump system can save operating cost in heating season is:   Qd Qd  pr   P   nr Cr   (5)  q   1000  COPr  3600  e g  Where: Cr is cost saving in heating season, yuan; pr is standard coal price,550yuan/t; nr is days of heating season,165 days. Saving operating costs one year is: C  Cl  Cr (6) Table1.Sewage source heat pump system and the initial investment of the original system System form Unit (10000 yuan) Boiler (10000 yuan) Auxiliary equipment (10000 yuan) Construction (10000 yuan) Total (10000 yuan)

Coal fired boiler + aircooled chiller 59 57 31.91 45.96 193.87

Sewage source heat pump system 160.94 0 20.4 40.33 221.67

According to the calculation, one year's total operating cost savings of 58266 yuan, compared with the original system, the annual operating costs decreased by 11%.Table 1 shows that the sewage source heat pump system compared with the original system of more than 278 thousand yuan investment, incremental investment payback period of 4.7 years.

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4.3 Environmental benefit analysis Pollutant emission reduction in heating season is:

Δm w,i  M1  ΔR w,i

(7) Where: Δmw,i is daily emission reduction of NOi pollutants in heating season, kg; i represent CO2, NOx, SOx and dust; ΔRw,i is quality of NOi pollutants produced by heat pump mass coal combustion, kg/kg, data are shown in Table 2. Table 2[9].Emission quota of pollutants in China Pollutant Standard coal/kg•kg-1 Electric power/kg•kWh-1

The results are shown in Table 3.

CO2 2.75 1.126

NOx 0.004 0.0016

SOx 0.03 0.0123

Dust 0.02 0.082

Table 3.Daily pollutant emission reduction of sewage source heat pump system Pollutant Emission reduction in heating season kg/d Emission reduction in cooling season kg/d

CO2 7318.0 1013.4

NOx 10.6 1.44

SOx 79.8 11.07

Dust 53.2 73.8

From the above data we can see that compared with the traditional coal-fired boiler and air-cooled chiller, the sewage source heat pump system has good environmental benefits. Therefore, the use of sewage source heat pump system for building heating and cooling, is an effective way to alleviate environmental pollution. It is also an effective way to solve the energy shortage.

5. Conclusion (1)The performance of the unit increases with the increase of inlet temperature, and decreases with the increase of circulating water temperature. The energy consumption of the pump can not be changed with the change of the load. In order to save the energy consumption, it is suggested to use the variable frequency pump to match the change of the load. In order to make the unit run more efficiently, it is necessary to clean the fouling of the heat exchanger. (2)Compared to air-cooled chiller and coal-fired boiler system, heat pump system of the hotel by the sewage source of primary energy consumption a year savings of 53%, annual operating costs reduced by 11%, the incremental investment recovery period is 4.7 years, while reducing the emission of pollutants and has better energy efficiency, economic benefit and emission reduction benefits. (3)In consideration of the advantages of sewage source heat pump, we should give priority to the use of sewage source heat pump in a conditional area. References [1]Zhou Wenzhong,Li Jianxing,Tu Guangbei.Prospect of sewage source heat pump systems and cooling and heating energy utilization of sewage[J].Heating Ventilating & Air Conditioning,2004,34(8):25-29. [2]Yin Jun,Chen Lei,Wang Heli.Recycling of municipal sewage and recycling of heat energy. Beijing: Chemical Industry Press,2003. [3]General Office of the State CouncilNDRC[2016]2705. [4]Wang Jianhui,et al.Experimental research on small-sized sewage source heat pumps. Hebei Industrial Technology,2014(01):78-82. [5]Yang Shengdong,et al.Application of sewage source heat pump air conditioning system. Heilongjiang Science and Technology Information,2014(19):116 [6]Zhu An,Zhao Qiming,Yu Yonghui,et al. Analysis on the Feasibility and Environmental Benefits of the Application of Sewage Source Heat Pump in Guiyang City[J].Anhui Agriculture University,2010,28(5):2522-2524 [7] Qian Jianfeng,Sun Dexing,Ji Amin,et al. Analysis of Direct Sewage Source Heat Pump System and Its Characteristics on Energy Efficiency and Environmental Protection[A].China Refrigeration Institute Proceedings of the 2009 annual meeting[C].Tianjin: China Refrigeration Institute,2009. [8]Yin Jun,Chen Lei,Bai Li. Municipal wastewater reclamation and thermal energy utilization technology[M].Beijing Chemical Industry Press,2010. [9]Su Jianfeng,Han Wei,Lin Rumou,et al. Tower Type Solar Energy-based Thermal Power Generation System with a Two-stage Heat Storage and Dual Operating Mode[J].Journal of Engineering for Thermal Energy and Power,2009,24(1):132-137.