能源效率表现多能源供热和热水供应系统-外文翻译.doc

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1、外文文献：Energy efficiency performance of multi-energy district heating and hot water supply systemSchool of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China Central South University Press and Springer-Verlag Berlin Heidelberg 2012J. Cent. South Univ. (2012) 19: 13771382D

2、OI: 10.1007/s11771-012-1153-8Energy efficiency performance of multi-energy district heating andhot water supply systemJIN Nan(金楠), ZHAO Jing(赵靖), ZHU Neng(朱能)School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China Central South University Press and Springer-Verlag

3、Berlin Heidelberg 2012Abstract: A district heating and hot water supply system is presented which synthetically utilizes geothermal energy, solar thermal energy and natural gas thermal energy. The multi-energy utilization system has been set at the new campus of Tianjin Polytechnic University (TPU).

4、 A couple of deep geothermal wells which are 2 300 m in depth were dug. Deep geothermal energy cascade utilization is achieved by two stages of plate heat exchangers (PHE) and two stages of water source heat pumps (WSHP). Shallow geothermal energy is used in assistant heating by two ground coupled h

5、eat pumps (GCHPs) with 580 vertical ground wells which are 120 m in depth. Solar thermal energy collected by vacuum tube arrays (VTAs) and geothermal energy are complementarily utilized to make domestic hot water. Superfluous solar energy can be stored in shallow soil for the GCHP utilization. The s

6、ystem can use fossil fuel thermal energy by two natural gas boilers (NGB) to assist in heating and making hot water. The heating energy efficiency was measured in the winter of 20102011. The coefficients of performance (COP) under different heating conditions are discussed. The performance of hot wa

7、ter production is tested in a local typical winter day and the solar thermal energy utilization factor is presented. The rusults show that the average system COP is 5.75 or 4.96 under different working conditions, and the typical solar energy utilization factor is 0.324.Key words: geothermal energy;

8、 solar thermal energy; district heating; hot water supply1 IntroductionBuilding energy consumption takes about 23% in the total energy consumption in China at present and it is in growth trend 1. Heating loads, cooling loads and hot water loads are the main items of building energy consumption. Rene

9、wable energy has been widely used in China for recent years. Geothermal energy and solar thermal energy are most commonly used in buildings. Independent utilization of single renewable energy is popular, but integrated utilization of several kinds of renewable energy is relatively scarce. A district

10、 heating and hot water supply system wasdesigned for the new campus of Tianjin Polytechnic University, China. In this system, geothermal plate heat exchanger (PHE), water source heat pump (WSHP),ground coupled heat pump (GCHP) and natural gas boiler (NGB) are used synthetically to heat the campus bu

11、ildings;geothermal PHE, vacuum tube array (VTA) and NGB are used complementarily to make domestic hot water.There are some case studies on geothermal district heating in Turkey in resent years 27. Some researches focused on energy analysis of geothermal heating systems 815. In these researches, deep

12、 geothermal energy is the only source of heating. This system uses multi-energy in heating, including deep geothermal energy, shallow geothermal energy and natural gas thermal energy. The system uses solar thermal energy, deep geothermal energy and natural gas thermal energy to make dwells hot water

13、. Though there was previous research on solar energy used in heating and cooling 16, solar hot water used directly as dwells hot water is a direct and highly efficient way to utilize solar thermal energy. The coefficients of performance (COPs) under different heating conditions are discussed accordi

14、ng the actual measurement data in the winter of 20102011. The performance of solar hot water production in a local typical sunshine winter day is presented. The design idea of this system can be referred in other multi-energy building system designs.2 Systems and operation strategyThe geothermal, so

15、lar thermal and natural gas thermal energy coupling utilization system for district heating and central hot water supply of TPUs new campus consists of two parts: multi-energy district heating system (MEDH) (Fig. 1) and multi-energy central hot water supply system (MECHWS) (Fig. 2). Foundation item:

16、 Project(2010DFA72740-06) supported by International Science & Technology Cooperation Program of China Received date: 20110726; Accepted date: 20111114 Corresponding author: ZHAO Jing, PhD; Tel: +862227409188; E-mail: zhaojing2.1 MEDHThe MEDH utilizes both geothermal energy of deep layer and shallow

17、 layer. Natural gas thermal energy is used as an auxiliary and assistant heating source. A couple of geothermal wells that reach the Ordovician in depth of 2 300 m were dug. Each well was set in a well house and equipped with well mouth equipments. Groundwater is drawn up by a variable frequency sub

18、mersible pump (VFSP). Then, the groundwater is pumped to well water heat exchangers (WWHE) and the hot water heat exchangers (HWHE) of the MECHWSs. The control valve (CV) in Fig. 1 is only opened when the MECHWS needs geothermal water. The WWHEs are divided into two stages. The groundwater is pumped

19、 through the hot side of the first stage of the WWHE (WWHE-I). The cold side of the WWHE-I is connected to the water feeder and collector of the MEDHs. The circular flow pumped by the pump P1 through the cold side of the WWHE-I is a part of the heating flow. The groundwater is divided into two flows

20、 after it comes out the hot side of the WWHE-I by an electric control valve (ECV). One part is sent to the hot side of the second stage of the WWHE (WWHE-II) and the flow rate is set according to the outlet water temperature of the cold side of WWHE-II. The outlet water of the WWHE-II is pumped to t

21、he evaporators of the WSHP. When the temperature exceeds 24 C, the ECV will decrease the groundwater flow rate to the WWHE-II until the temperature is below 24 C. When the temperature is below 20 C, the ECV will do the opposite operation. This is because exorbitant evaporator water temperature would

22、 cause the compressor lubricating oil to be carbonized and the low evaporator water temperature would lead to an inferior COP of the WSHP. The groundwater flows are combined and sent to the inverted well after cascade utilization, as shown in Fig. 1. The groundwater can be inverted to 100% due to th

23、e local geological structure and there is no need for pressure inverted pumps. The WSHPs are divided into two stages too, WSHP-I and WSHP-II. The cold side circular flow of the WWHE-II pumped by P2 is just the heat source of the WSHP. The circular flow is sent into the evaporator of WSHP-I and then

24、the evaporator of the WSHP-II gives off heat in sequence. The condensers of the WSHP are paralleled and connected to the water feeder and collector of the MEDHs. The circular flow through the condensers pumped by the pump P3 is another part of the heating flow. The WSHP are also used as freezers in

25、summer with the cold source of cooling towers. Two GCHPs are paralleled to heat and cool the buildings too. 580 vertical double U-tube ground heat exchangers (VDUGHE) are used to absorb and release heat. The holes of U-tubes are 120 m in depth. The GCHPs are connected to the water feeder and water c

26、ollector of the MEDHs to supply heating and cooling flows. Two parallel NGBs are used to assist in heating when the geothermal energy cannot fulfill the peak heat load or the geothermal energy equipments are broken.2.2 MECHWSsThe MECHWSs utilize solar thermal energy, geothermal energy and natural ga

27、s thermal energy in a complementary way. Two parallel VTAs are used to collect solar thermal energy. Each of the VTAs consists of 120 collectors. Each collector has 50 vacuum tubes in parallel connection. Every 5 collectors are set in series and 24 such series are paralleled each other to constitute

28、 an array. The total absorber area of two VTAs is 1 500 m2. The solar hot water is used as hot water of dwells directly. The water is circulated by the pump P4 between the VTA and a solar hot water tank (SHWT) which is 20 t in capacity. The water temperatures in the middle height of the tank and the

29、 outlet of the VTA are tested by platinum resistance thermometers. The temperature signals are sent to an electric control casing (ECC-1) which controls the water circulation between the VTA and the SHWT. The water in the SHWT can be pumped by the pump P5 to a central hot water tank (CHWT) which is

30、200 t in capacity and the water in the CHWT can be pumped to the SHWT by the pump P6. The water temperature in the CHWT is tested by a platinum resistance thermometer. This temperature signal and the SHWT water temperature signal are sent to the second electric control casing (ECC-2). The water circ

31、ulation between the SHWT and the CHWT is controlled by the ECC-2. If the collected solar thermal energy cannot meet the energy requirement to make enough hot water of dwells, geothermal energy will be used to heat water through the HWEC. Natural gas thermal energy is also used as an auxiliary and as

32、sistant source to heat the water in theCHWT through the HWEC. The water of the CHWT will be circulated by the pump P7 when it needs to be heated through the HWEC. The hot water circulation between the CHWT and the campus building ends is pumped by the pump P8. The solar thermal energy collected by t

33、he VTAcannot be consumed in summer vacation and needs to be stored. The heat load is higher than the cold load of the new campus. There is a need to replenish heat to the soil coupled with the VDUGHE. So, a device was designed and installed for solarsoil heat transformation (SSHT) to resolve the two

34、 problems. This device connects the SHWT and 580 VDUGHE. Corrugated heat exchange tubes were set in the SHWT. It was connected to the main inlet and outlet tubes of the VDUGHE. The water circulated by the pump P9 can transfer the redundant solar heat from the SHWT to the shallow soil layer. The heat

35、 is stored in the soil and waits for the GCHP exploitation.2.3 Operation strategy2.3.1 District heatingThe heat load is relatively low in the beginning and the end periods of a heating season. The heat load and electric power consumption of the GCHP are lower than those of the WSHP in the system. So

36、, the WWHE-I and the GCHP are used in parallel in beginning and end heating periods. Only one of the GCHP is used usually, and the other one is used to fulfill the peak heat load. In the middle period of a heating season, the heat load is always high and the WSHPs are operated instead of the GCHPs.

37、The WWHE-I is always used. The WSHP-I and the WSHP-II are used according to the priority to fulfill the heat load. If the WWHE-I and the WSHP-I could fulfill the campus heat load, the WWHE-II will not be used or be used only to meet the peak heat load.The VFSP is easy to be damaged in its running su

38、rrounding: The deep geothermal well. When it is broken, the WWHE-I and the WSHP cannot be used to supply heat. The GCHP and the NGB will be combined to supply heat at that time.2.3.2 Hot water productionWhen the outlet water temperature of the VTA is higher than that of the SHWT at a variable set va

39、lue in the ECC-1, for example 6 C, the ECC-1 can activate the pump P4 to circulate the water. The circulation will be ended when the water temperature difference is under another set value in the ECC-1, for example 3 C. The same rule is used in the ECC-2 to control the circulation between the SHWT a

40、nd the CHWT by activating the pumps P5 and P6. If the CHWT is not full, the ECC-2 can only activate the pump P5 to supply hot water to the CHWT. The SHWT is connected to a tap water pipe. When the water level is lower than half of the SHWT, the ECC-1 will open the solenoid pilot actuated valve (SPAV

41、) on the tap water pipe to supply water to the SHWT. The above solar thermal energy collection strategy can be used in summer and transition seasons. In such seasons, the water temperature of the SHWT is usually higher than 40 C and it can be used as bath water. But the rule is not applicable in col

42、d winter days. The SHWT water temperature can usually reach 2030 C under the above rule in sunshine cold winter days. The water temperature of the CHWT is always higher than 40 C by the contribution of geothermal energy and natural gas thermal energy. So, the circulation between the SHWT and the CHW

43、T cannot be activated. If the water consumption in the CHWT is only supplemented by tap water, the collected solar thermal energy will not be used. The water of 2030 C can be sent to the CHWT, but it must be heated through the HWHE to reach the bath water temperature (at least 44 C in winter). The b

44、ath water demand in winter is relatively low and it is more convenient and economic to supply smaller amount with higher temperature solar hot water to the CHWT than larger amount with lower temperature water. So, the strategy of solar thermal energy utilization in winter is as follows. The auto cir

45、culation is ended in the morning and the circulation between the VTA and the SHWT is manually activated when the water temperature of the VTA reaches the top of a day and begins to fall at 14:00 to 15:00. When the inlet water temperature of the SHWT is equal to its outlet water temperature, thecircu

46、lation is ended manually. The temperature of the SHWT is usually around 50 C at this time. Then, the water in the SHWT is totally pumped to the CHWT. The water in the CHWT is not pumped back to the SHWT in this condition. After the manual operation, the ECC-1 will be set to auto control and tap wate

47、r will recharge the SHWT. The auto circulation between the SHWT and the VTA will continue until the next morning. In the evening, if the VTA water temperature is lower than the SHWT water temperature by a set value, the ECC-1 will activate the pump P4 to start circulation for freezing prevention. If

48、 the water temperature of the CHWT is not high enough to be supplied as bath hot water, the operators will manually open the CV in Fig. 1 and open the pump P7 in Fig. 2 to heat the water by geothermal energy through the HWHE. The NGB will be used to heat water when the VFSP is broken or the geotherm

49、al energy is totally used in heating and has no surplus for hot water of dwells. The NGB is also used as the heat source of HWHE if the VFSP is stopped in summer and transition seasons.3 Test results and discussion3.1 Heating performanceCOP is defined as the ratio of heating load to electric power consumption. The COP of heating equipments and the whole combination system under different conditions are analyzed according to test data. The geothermal energy utilization factor (GEUF) is d