Economic Estimation of Heat Storage Type Geothermal Source Heat Pump System Applied in K-Ward Office Building

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1 Economic Estimation of Heat Storage Type Geothermal Source Heat Pump System Applied in K-Ward Office Building Myung Jin Ko 1, a, Yong Shik Kim 2, b, Yong In Kim 3, c, Eun Taek Lee 4, d, Joong Heon Kim 5, e, Seung Ho Shin 6, f 1, 2 Department of Architectural Engineering, University of Incheon, Incheon, Korea, NOW Consulting Engineers co. LTD, Seoul, Korea, 4, 5, 6 Samsung Engineering and Construction, Gyunggido, Korea, a whistlemj@nate.com, b newkim@incheon.ac.kr, c nowmec@chol.com, d leeet@samsung.com, e kjh5955@samsung.com, f seungho.shin@samsung.com ABSTRACT Geothermal-energy has been getting popular as a natural energy source for green buildings these days. Public building with gross area more than 3000 m2, planned after March, 2005, should spend about 5% of total building on equipment run by natural energy source (e.g. geothermal, solar heat, solar power,etc) according to renewable energy promotion law in Korea. As a result Geothermal Source Heat Pump System (GSHPs) was being recognized effective alternative systems to conventional heating and cooling systems owing to their higher energy utilization efficiency. But GSHPs has not been popularized thereby the large a mount of initial of the system and insufficiency of studies for Economic Estimation. Therefore GSHPs are being developed to make up for the weak points that are the large a mount of initial of the system and much annual electricity consumption. In this paper, Economic Estimation was analyzed by Payback Period method and it shows that the Pay Back Period of Heat Storage Type Geothermal source Heat Pump System was calculated 6.8 years compared with the absorption Chiller-Heater system and 8.2 years compared with the Ice storage-boiler system. Heat Storage Type GSHPs also has the lower annual source energy consumption than the conventional heating and cooling systems because of using Nighttime electricity. KEYWORDS: Economic Estimation, Payback Period method, Heating-cooling plant system, Geothermal Source Heat Pump Systems (GSHPs) 1. INTRODUCTION The Republic of Korean government is actively promoting development and revitalization of new & renewable energy to improve this situation of energy demand and supply and to protect global environment. For this reason, government has made every effort to develop the technics and to revitalize the supply of new & renewable energy of eleven classes (e.g. geothermal, solar heat, solar power, etc) according to renewable energy promotion law in Korea, Public buildings with gross area more than 3,000 m2 planned after March, 2005, should spend about 5% of total building on equipment run by natural energy source. In advanced country, Geothermal-energy has been used as space heating and cooling energy source owing to its superiority in aspect of continuity and safety. In domestic country, building application with geothermal-energy is get increased, based on importance of building energy saving and being brought into relief of environmental protection. It also get enhanced by the development of relevant technics and protection law for the energy. But this application of Geothermal-energy using system is still limited to public buildings and a few of private 795

2 buildings, because of the large amount of initial of the system. So Geothermal-energy using system is being developed to reduce initial recently. There haven't been only a number of studies concerning on performance and economic estimation of GSHPs such as Lim et al. (2004), Shon et al. (2004) and Shin et al. (2005), but also a number of studies concerning on performance and actual proof of Heat Storage Type GSHPs such as Choi et al. (2003) and Choi et al. (2004). But it was insufficient that economic estimation of Heat Storage Type GSHPs. On this background, this research aims at economic estimation to the 4 classes heatingcooling plant systems including Heat Storage Type GSHPs. K-ward office building is examined for this research. Payback period based on initial and running of each systems is considered for the economic efficiency of this systems. 2. TARGET BUILDING AND HEATING-COOLING PLANT SYSTEM 2.1 Target Building Figure 1 shows the facade of the target building. Table 1 shows the synopsis of the target building. Target building is the K-ward office building under construction in Seoul and has the size of the Gross Area 39,075 m2. Maximum cooling load is 1,200 USRt, maximum heating load is 3,629 Mcal/h. Table 1. Target Building Figure 1. Target Building 2.2 Target Heating-cooling plant system Items Contents Location K-ward, Seoul Floor 12 Floors and 2 basement floors Occupancy A ward office building, parliament, A public health center, An assembly hall Plottage 17,200m 2 Gross Area 39,075m 2 Structure SRC + Steel Structure Cooling Load 1,200 USRt Heating Load 3,629 Mcal/h (a)heat Storage Type GSHPs (b) GSHPs (c) Ice Storage-Boiler system Figure 2. Selected Systems (d) Absorption Chiller-Boiler system Target building which is public building should spend about 5% of total building on equipment run by natural energy source. In this paper, Geothermal-energy is supposed to be as natural energy source of target building. Also it was selected heating-cooling systems for economic 796

3 estimation GSHPs, Heat Storage Type GSHPs, Ice Storage-Boiler system and Absorption Chiller- Heater system which have been applied. Fig 2 shows configuration of the selected systems for economic estimation 3. ANALYSIS OF INTIAL COST 3.1 Analysis method of Initial Table 2 shows the synopsis of the analysis method of Initial. Analysis items are set Equipment, Construction and Support. Equipment which is the of equipment was limited the of heat source equipment. Construction of SYSTEM-A and SYSTEM-B which is used geothermal heat pump adds the of SCW(Standing Column Well). Construction of SYSTEM- C and SYSTEM-D which use LNG as fuel adds the construction of gas piping and gas duct. Equipment and construction data is based on Korea Information Corporation and field estimation data. Also support of government and public institutions is considered. Table 2. Analysis method of Initial Categories Contents Data Equipment Heat source equipment Construction Support 3.2 Analysis results of Initial Table 3. Initial of SYSTEM-A Equip. Const. "B" Piping, Automatic control, SCW, Electrical equipment, Gas/Gas-duct, Government A tax favor, Financial support Korea Electric Power Corp. Installation support, A design bounty Korea Gas Corp. Installation support, A design bounty Categories Capacity Quantity Heat Cooling (USRt) ,000 pump Heating (Mcal/h) 340 Storage tank (USRt h) 1, ,000 accumulation of cold ,000 pump (Hp heat release ,000 heat exchanger ,000 deep well , ,500 automatic valve (A) ,800 chilled and hot water heat 604, ,500 exchanger (kcal/h) Geothermal source heat exchanger (kcal/h) 375, ,000 minor total 442,800 heat storage/ Geothermal source pipe 140,000 Automatic control 57,000 SCW 490,000 Electric power Equipment 30,000 minor total 717,000 Support Installation support 86,400 "C" minor total 86,400 Table 4. Initial of SYSTEM-B Equip. Const. "B" Support "C" Heat pump pump (Hp Categories Capacity Quantity Cooling (USRt) Heating (Mcal/h) heat exchanger Korea Information Corp, Field Estimation Data 4 436, ,000 deep well ,000 heat exchanger 375, ,000 minor total 505,000 Geothermal source pipe 140,000 Automatic control 57,000 SCW 980,000 Electric power Equipment 55,000 minor total 1,232,000 Installation support - minor total - Initial A+B-C 1,073,400 Initial A+B-C 1,737,

4 Table 5. Initial of SYSTEM-C Equip. Categories Capacity Quantity Table 6. Initial of SYSTEM-D Categories Capacity Quantity Cooling Daytime Refrigerator Absorption (USRt) 2 96, ,400 (USRt) chiller-heater Heating Nighttime (Mcal/h) Cooling tower(rt) ,000 Equip. Cooling tower(rt) ,000 Storage tank (USRt/h) 1, ,000 Circulation cooling water ,500 Circulation cooling ,000 pump(hp) Brine ,500 pump water near by storage ,800 minor total 282,400 tank 3-way valve near by heat ,600 Cooling water 65,000 exchanger Boiler(ton/h) ,800 Automatic control pipe 40,000 Brine(ton) ,200 Const. Heat exchanger(kcal/h) 604, ,500 Electric power 10,000 minor total 426,900 "B" Equipment Cooling water/brine pipe 85,000 Gas Piping/Gas duct 60,000 Automatic control 45,000 Const. Electric power Equipment 35,000 "B" Gas Piping/Gas duct 60,000 minor total 225,000 Support Installation support 86,400 "C" minor total 86,400 Support "C" minor total 175,000 Installation support 4,000 minor total 4,000 Initial A+B-C 565,500 Initial A+B-C 453,400 Table 3~Table 6 Shows results of Initial of each systems. Initial is appeared highly in the order of GSHPs, Heat Storage Type GSHPs, Ice Storage-Boiler system and Absorption Chiller- Heater system in that order 4. ANALYSIS OF RUNNING COST 4.1 Analysis method of Running Table 7. Analysis method of Running Table 7 shows analysis method of running. It Categories Contents needs energy consumption of each systems for analysis Standard Cooling-Heating Load Index of of running and consideration against cooling load, Load factor Korea Electric Power Corp. heating load and using form and so on of target Operating hours 08:00 ~ 18:00, 10 hours building for analysis of energy consumption. In this Running days 25 days paper, Cooling-heating load of the target building is analyzed with using Standard Cooling-Heating Load Index of Korea Electric Corporation. Cooling load and heating load of the target building is analyzed 1,200 USRt, 3,629 Mcal/h respectively. Also allotted cooling-heating load as base load of the target systems against cooling-heating load of the target building was set 400 USRt, 1,210 Mcal/h respectively. Operating hours of the target systems are 10 hours from 08:00 to 18:00, running days are 25 days. Figure 3~Figure 4 shows cooling load for month of the target building and assigned load of the target systems. Figure. 3. Cooling Load for month Figure. 4. Heating Load for month 798

5 4.2 Analysis results of running Running of the target systems is analyzed reflecting price of energy source after energy consumption calculation of the target systems. Table 8 shows results of the each systems energy consumption. GSHPs and Heat Storage Type GSHPs use only electric energy when they work, and Ice Storage-Boiler system and Absorption Chiller-Heater system use electric energy and LNG for operating. Also Ice Storage-Boiler system is operated using electric energy only in cooling period. Table 9 shows the prices of electric energy of Korea Electric Corporation and gas energy of Korea Gas Corporation. Table 10 shows cooling, heating and annual running reflecting annual energy consumption and price of energy source of each system. GSHPs was most expensive in cooling and so was Absorption chiller-heater system in heating. Cooling and heating of Heat Storage Type GSHPs was lowest among the target systems. Running of Absorption Chiller- Heater system is the most expensive among the target systems and annual running of Heat Storage Type GSHPs is less than a half GSHPs by reason of characteristic of Heat Storage Type GSHPs which use moderate night thermal-storage power. Table 8. Annual energy consumption of each system SYSTEM-A SYSTEM-B SYSTEM-C SYSTEM-D Categories Elec. (kwh) LNG Elec. LNG Elec. (kwh) LNG Elec. LNG Nighttime Other-time (N m3 ) (kwh) (N m3 ) Nighttime Other-time (N m3 ) (kwh) (N m3 ) Jan. 71,525 58, , ,470 32,011 3,626 33,587 Feb. 71,525 58, , ,470 32,011 3,626 33,587 Mar. 71,525 58, , ,470 32,011 3,626 33,587 Apr. 71,525 39, , ,118 27,443 3,109 28,495 May. 46,000 32, , ,429 33, ,744 21,371 Jun. 46,000 60, , ,429 66, ,325 28,495 Jul. 46,000 60, , ,429 66, ,325 28,495 Aug. 46,000 60, , ,429 66, ,325 28,495 Sep. 46,000 60, , ,429 66, ,325 28,495 Oct. 46,000 19, , ,429 20, ,065 17,952 Nov. 71,525 58, , ,470 32,011 3,626 33,587 Dec. 71,525 58, , ,470 32,011 3,626 33,587 total 705, , ,236, , , , , ,733 unit : 1000 won Table 9. of energy source Classification Demand charge (won per kw) Power Demand charge (won per kwh) Service-B High Voltage Power A Choice ( Ⅱ ) Charge Night thermal-storage power service(b) Peak period Hours July, August October~March The others Heavy-peak period hours ,130 Maximum-peak period hours Application charge (5,730won/kw) Winter Night-time (consumption between 8 a.m. and 10 p.m. ) other season (monthly total consumption) Other-time Minimum charge of Night thermal-storage power service(b) : 570 won per kw LNG (Seoul) Consumption charge for cooling : won/n m3, Consumption charge for heating : won/n m3 Table 10. Running of each systems Cooling Heating Categories SYSTEM -A SYSTEM -B SYSTEM -C SYSTEM -D Elec. 31,103 66,051 35,168 17,154 Gas ,045 minor total 31,103 66,051 35,168 59,199 Elec. 38,052 78,551 1,178 1,730 Gas ,824 99,495 minor total 38,052 78,551 96, ,224 Total 69, , , ,

6 5. PAYBACK PERIOD ANALYSIS OF EACH SYSTEMS Payback period is analyzed of the difference between initial and running exclusive of interest rate and price escalation rate. Payback period of GSHPs and Heat Storage Type GSHPs is calculated 81.1 years and 6.8 years respectively compared with the Absorption Chiller-Heater system which is equipment in nomal service. Accordingly GSHPs has hardly any economic feasibility, Heat Storage Type GSHPs has economic feasibility. It is the reason that Heat Storage Type GSHPs uses moderate night thermal-storage power contrary to GSHPs. Payback period of Heat Storage Type GSHPs was calculated 8.2 years compared with the Ice Storage-Boiler system whereas payback of GSHPs was impossible and Payback period of Absorption Chiller-Heater system was calculated deficit after 3.8 years. Accordingly Heat Storage Type GSHPs was disadvantageous in the initial aspect as compared with Ice Storage-Boiler system and Absorption Chiller-Heater system but has economy in the running aspect. 6. CONCLUSION 1) Initial Initial s was appeared highly in the order of GSHPs, Heat Storage Type GSHPs, Ice Storage- Boiler system and Absorption Chiller-Heater system in that order. 2) Running GSHPs was most expensive in cooling and so was Absorption chiller-heater system in heating. Cooling and heating of Heat Storage Type GSHPs is lowest among the target systems. Also Absorption chiller-heater system was most expensive in annual running. Annual running of Heat Storage Type GSHPs is less than a half GSHPs. 3) Payback period GSHPs has hardly any economic feasibility because payback period of GSHPs was calculated 81.1 years compared with the Absorption chiller-heater system. Heat Storage Type GSHPs has economic feasibility because payback period of Heat Storage Type GSHPs was calculated 6.8 years compared with the Absorption chiller-heater system. Whereas Payback period of Heat Storage Type GSHPs is calculated 8.2 years compared with the Ice Storage-Boiler system, payback of GSHPs was impossible. Payback period of Absorption Chiller-Heater system is calculated as deficit after 3.8 years compared with the Ice Storage-Boiler system. Accordingly Heat Storage Type GSHPs is disadvantageous in the initial aspect as compared with Ice Storage-Boiler system and Absorption Chiller-Heater system but has economy in the running aspect. From now on, it would be necessary for Life cycle to be more deeply executed, regarding to specific factors of system and changing factors like interest rate, price escalation rate and so on. REFERENCES Lim, H.J., Song, Y.S., Kong, H.J., Park, S.K., "Performance Evaluation and Economic Estimation of Ground Source Heat Pump Cooling and Heating System" Journal of Energy Engineering, 13(4), pp Sohn, B.H., Shin, H.J., Park, S.K., 2004, "Comparative Analysis of Life-Cycle Costs of Ground Source Heat Pump and Conventional HVAC System", Proceedings of the SARAK 2004 Summer Annual Conference, pp Shin, H.J., Cho, C.S., Hwang, I.J., Lee, S.W., Sohn, B.H., Lim, H.J., Park, S.K., Song, Y.S., Kong, H.J., 2005, "Construction of Performance Evaluation Methods and Technical Standards for Ground Source Heat Pump Systems" Choi, B.Y., Lee, S.H., J, Y.H., Chai, K.H., 2003, "An Experimental Study for Heat Storage Type Ground Source Heat Pump System" Proceedings of the SARAK 2003 Winter Annual Conference, pp Choi, B.Y., Lee, S.H., Kim, J.H., Lee, D.W., 2004, "The Field Test of Ground Heat Source Water Thermal Storage Type Heat Pump Cooling & Heating System" Proceedings of the SARAK 2004 Summer Annual Conference, pp