복합용도 건물에 적용된 400RT급 수직형 지열시스템의 입주전 성능평가

황광일(Hwang Kwang-Il),신동걸(Shin Dong-Keol),김중헌(Kim Joong-Hun),신승호(Shin Seung-Ho),정명관(Jung Myoung-Kwan) 한국태양에너지학회 2008 한국태양에너지학회 논문집 Vol.28 No.3

400RT geothermal system which is the biggest capacity among on-operations at present in Korea is measured and evaluated on 23rd~26th Jan. 2008 during those days building is not allowed owners and/or tenants to move in. The geothermal system is consist with vertical-typed 112 geothermal heat exchangers which are installed circle-like 1 row with 4m interval, and has 16 units of 25USRT geothermal-source heat pump(GSHP)s. And each 5 units of circulation pump are running for geothermal heat exchangers and hot water supplies. The followings are the results. The temperatures at G.L. -70m of 2 boreholes are varied quite similarly. The average temperature difference between inlet and outlet of geothermal pipes is 4.1℃, and that of hot water supply is 3.2℃, of Zone 3's each 4 GSHPs when being operated. Despite temperature fluctuations by heating loads, the average temperature difference between main pipes of inlet and outlet of geothermal heat exchangers is measured as 4.1℃. This study propose "Geothermal System COP" which includes not only consumed electric power by compressor but also circulation pumps and auxiliary utilities. By comparing the geothermal system COP with GSHP's performance specification, it is clear that the performances of GHSPs of this site are satisfied with the specification.

EGS 지열 저류층 유체 유동에 의한 SP 반응 모델링

송서영 ( Seo Young Song ),김빛나래 ( Bitnarae Kim ),남명진 ( Myung Jin Nam ),임성근 ( Sung Keun Lim ) 한국지구물리·물리탐사학회 2015 지구물리와 물리탐사 Vol.18 No.4

자연 전위(SP, self-potential)의 발생에는 여러 요인이 있으나 이 연구에서는 지하수의 유동에 의해 자연적으로 발생하는 유동 전위(streaming potential) 또는 전기역학적 전위(electrokinetic potential)에 대해 주로 논의한다. 유동 전위는 다공질 매질에서의 물의 흐름에 의해 인공적인 전류원 없이 전류가 발생하여 야기된 전위이다. 기존의 유동 전위를 이용한 지열 저류층 해석에서는 지표면 전위 분포 계산을 위해 일반적으로 시추공에서 주입되거나 생산되는 지하수로부터 발생하는 SP 이상만을 고려하였고, 온도 차이가 나는 지열 저류층에서의 지열수 순환에 따라 발생할 수 있는 SP에 대한 수치 모델링에는 한계가 있었다. 이에 따라 사면체 요소를 바탕으로 한 3차원 전기비저항 유한요소법에 기초하여 지열 저류층 내에서의 주입정, 생산정에 의한 SP 이상뿐만 아니라 지열 저류층에서의 지열수 순환에 따른 SP 이상까지 고려할 수 있는 알고리듬을 개발하였다. 본 논문에서는 개발한 알고리듬을 검증 한 후, 간단한 지열 저류층 모델에 지열수주입과 양수의 효과에 의한 SP 이상대의 SP 반응을 분석하였다. 향후 개발한 알고리듬을 이용하여 지층의 물성을 고려한 지열수 유동 속도 등도 고려함으로써 보다 심도 있게 지열 저류층 SP 반응을 분석하고자 한다. Self-potential (SP) is sensitive to groundwater flow and there are many causes to generate SP. Among many mechanisms of SP, pore-fluid flow in porous media can generate potential without any external current source, which is referred to as electrokinetic potential or streaming potential. When calculating SP responses on the surface due to geothermal fluid within an engineered geothermal system (EGS) reservoir, SP anomaly is usually considered to be generated by fluid injection or production within the reservoir. However, SP anomaly can also result from geothermal water fluid within EGS reservoirs experiencing temperature changes between injection and production wells. For more precise simulation of SP responses, we developed an algorithm being able to take account of SP anomalies produced by not only water injection and production but also the fluid of geothermal water, based on three-dimensional finiteelement- method employing tetrahedron elements; the developed algorithm can simulate electrical potential responses by both point source and volume source. After verifying the developed algorithm, we assumed a simple geothermal reservoir model and analyzed SP responses caused by geothermal water injection and production. We are going to further analyze SP responses for geothermal water in the presence of water production and injection, considering temperature distribution and geothermal water flow in the following research.

Physical properties of G-class cement for geothermal well cementing in South Korea

Won, Jongmuk,Lee, Dongseop,Na, Kyunguk,Lee, In-Mo,Choi, Hangseok Elsevier 2015 RENEWABLE ENERGY Vol.80 No.-

<P><B>Abstract</B></P> <P>The cement material adopted for a new geothermal well project in South Korea is specialized as the G-class cement, which is commonly used in the oil-well industry, and regulated by the API (American Petroleum Institute). In order to maintain the optimal generating performance of geothermal wells, physical properties of the cementing material should be satisfactory. In this paper, the significant material properties (i.e., groutability, uniaxial compressive strength, thermal conductivity, bleeding potential, phenolphthalein indication) of the G-class cement were experimentally examined, with consideration of various water–cement (w/c) ratios as mix proportion. Important findings through the experiments are as follows; (1) Groutability of the G-class cement increases with the addition of a small amount of retarder. (2) There would be a structural problem when the w/c ratio is kept extremely high in order to obtain acceptable groutability. (3) Thermal conductivity of the G-class cement is small enough to prevent heat loss during circulating up hot steam or water from the deep underground to the ground surface. (4) The G-class cement used for geothermal-well cementing causes no bleeding problem. (5) The phenolphthalein indicator is applicable to distinguishing the G-class cement from the drilling mud.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Groutability of G-class cement increases with addition of a small amount of retarder. </LI> <LI> The optimum retarder–cement ratio is recommended between 0.01 and 0.015. </LI> <LI> The water–cement ratios of 0.55, 0.6, 0.7, and 0.8 will not cause structural problems. </LI> <LI> Thermal conductivity of G-class cement decreases with the water–cement ratio. </LI> <LI> The G-class cement for geothermal-well causes no bleeding problem. </LI> </UL> </P>

주상복합 건축물에 적용된 지열이용 히트펌프 시스템의 냉방성능 평가

김용식(Kim Yong-Shik),김중헌(Kim Jung-Heon),황광일(Hwang Kwang-Il) 한국태양에너지학회 2006 한국태양에너지학회 논문집 Vol.26 No.4

Geothermal-energy has been getting popular as a natural energy source for green buildings these days. Public building with gross area more than 3000㎡, planned after March, 2005, should spend about 5% of total building cost for 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-energy using heat pump system is emerging as a effective alternative for realistic and economic plan although design guidelines and construction code for the system is in progress and technical data is far from sufficient. The quantitative analysis on the performance of geothermal-energy using heat pump system is insufficient for appropriate design of it. In this paper, cooling performance of geothermal-energy using heat pump system of residential and retail etc. mixed-use building has been analyzed on the basis of temperature comparison between inlet and outlet of heat exchangers of the operating system. Additionally, dry-bulb temperature and relative humidity have been measured and analyzed together as an index of indoor thermal environment.

Deep Geothermal-water Characteristics of Tertiary Pohang in South Korea

( Woori Lim ),( Se-yeong Hamm ),( Cholwoo Lee ),( Seho Hwang ),( In-hwa Park ),( Yoon-ho Song ),( Hyeong-chan Kim ),( Chung-ryul Ryoo ),( Sul-min Yun ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

Pohang area displays a larger potential of geothermal energy with the highest heat flow of ~83 mWm^-2 in South Korea. This study aims to reveal geothermal characteristics of four wells(BH-1 to BH-4 wells) of ~2,000 m in depth in Pohang area, using geophysical logs. The geology of the study area is composed of tertiary mudstone of 200 - 359.1 m, tuff of 73 - 240 m, sandstone/mudstone of 46 - 907 m, rhyolite of 259 - 375 m, and andesitic volcanic breccia of 8 34 m in thicknesses from the surface, with granodiorite at bottom. By the result, temperature and maximum electrical conductivity are 69.5°C at 1,502.6 m and 1,162 μS/cm at BH-2, 44.4°C at 912.3 m and 1,105 μS/cm at BH-3, and 82.5°C at 1,981.3 m and 3,412 μS/cm at BH-4. Thermal conductivity values at saturated state are 2.14 - 3.95 W/m-K at BH-1 and 2.36 - 3.61 W/m-K at BH-4. ß (determining heat flow rate and up/down direction) values were estimated by using 1-D steady-state heat transfer equation and were determined as -0.77 - 0.99 with the geothermal gradients (Ks) of 42.5 - 46.3°C/km at BH-1, -3.15 - 3.05 with the Ks of 25.0 - 29.1°C/km at BH-2, -1.80 - 2.09 with the Ks of 20.0 - 23.0°C/km at BH-3, and -4.10 - 5.18 with the Ks of 30.2 - 39.0°C/km at BH-4. Most depths of all the wells showed upward heat transfer. Based on the geophysical logs, the main aquifer is located between 200 and 300 meters.

Studies on the Temperature Control System of the Geothermal-Source Heat Pump under Different Modes

Hu Tao,Su Huashan,Hong Feng,Xiao Renzheng,Zhu Jialing 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.3

Geothermal-source heat pump technology can increase the production efficiency and reduce the energy consumption. However, the application performance of the control system for the geothermal-source heat pump is always poor; such as a larger system operation energy consumption, low efficiency, poor stability and time effectiveness. In order to solve this issue, two advanced control strategies based on the research object of the geothermal-source heat pump temperature control system with different modes are developed: one is a feedforward-feedback control based on the variable speed integral PID control algorithm (“FFC-VSIPC”), the other is a feedforward-feedback control based on the fuzzy control algorithm (“FFC-FC”). The simulation and experimental studies of the effects of temperature control system in a geothermal-source heat pump by different models are carried out. The results shows that: (1) The overshoot of FFC-VSIPC is slightly larger than the FFC-FC when the set value is abruptly changed, but the adjustment time of FFC-VSIPC is shorter and there is no static error after the stabilization; (2) Changing the rate of flow interference suddenly, both FFC-VSIPC and FFC-FC can effectively eliminate the effects of interference with adding a feedforward control, also the adjustment time of FFC-VSIPC is greatly shortened than FFC-FC, but the stability of the adjustment is worse; (3) When the frequency amplification factor is suddenly changed, FFC-FC shows a non-stable control state of divergence gradually, FFC-VSIPC shows good robustness. The further comparisons between simulations and experiments reveal that FFC-VSIPC is better than FFC-FC in terms of the energy regulation and controlling of the geothermal source heat pump. Therefore, FFC-VSIPC is an advanced control strategy, which is worthy of research and application promotion.

지중열과 수열로 구성된 혼합열원 히트펌프 시스템의 난방성능분석

최홍식(Hong Sik Choi),민경천(Kyong Chon Min),손병후(Byonghu Sohn),임효재(Hyo Jae Lim) 대한설비공학회 2017 대한설비공학회 학술발표대회논문집 Vol.2017 No.6

The purpose of this study is to examine the initial cost down effects of geothermal and hydrothermal mixed source heat pump. Generally, construction cost of ground heat exchanger is higher than that of hydrothermal, especially surface water heat exchanger. Thus the natural or artificial pond nearby can be used as good heat source and sink. The residence building was selected for experiment and systematical data acquisition was conducted for analysis. From three cases of test, geothermal, hydrothermal and mixed(geothermal+hydrothermal), we could get following results. Heat pump COP in heating is 3.3 for mixed case and 2.8 for ground only. Also, system COP in heating is 2.5 for mixed case and 2.9 for ground only. Because of the over estimated circulation pump, COP shows a little low. Thus additional study needs for cooling performance and for raising of COP.

투자비회수기간법을 이용한 공공청사 적용 축열식 지열히트펌프 시스템의 경제성 평가

고명진(Ko Myung-Jin),오중근(Oh Jung-Keun),김용인(Kim Yong-In),김용식(Kim Yong-Shik) 한국태양에너지학회 2007 한국태양에너지학회 논문집 Vol.27 No.4

Geothermal-energy has been getting popular as a natural energy source for green buildings these days. 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 amount of initial cost 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 amount of initial cost of the system and much annual electricity consumption. In this paper, economic estimation was conducted by payback period method and it shows that the pay back period of Heat Storage Type GSHPs 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.

Analytic Method for the Design and Analysis of Geothermal Energy-Integrated Space Heating and Cooling Systems

김진국,Kim Soo Hyun,Lee Sunghoon,서영웅 한국화학공학회 2024 Korean Journal of Chemical Engineering Vol.41 No.1

Novel analytic modeling and design method is proposed for the analysis of geothermal-integrated energy systems which provide space heating and cooling. Rather than building a complex optimization framework, an analytic design procedure is developed to determine hourly and monthly distribution of renewable-sourced energy and its sizing in a systematic manner by considering renewable characteristics and energy storage. The new design method also allows to fully realize the advantage of geothermal energy through the seasonal supply of heating and cooling and to accommodate variable generation of other renewables. The benefi t of this short-cut design method has been fully illustrated with two case studies in which geothermal energy is used for the provision of combined heat and cooling in domestic and commercial applications. Case studies also demonstrate the impact of time-dependent generation of renewable energy on the sizing of energy suppliers and its seasonal or hourly allocation of working loads.

주택용 지열/태양광 최적 융복합시스템 연구

함형율(Hyeong-Yul Ham),정의권(Eui-Kwon Jeong),김용래(Yong-Rae Kim),허철영(Cheol-Young Heo),최익(Ick Choy),최주엽(Ju-Yeop Choi) 한국태양에너지학회 2019 한국태양에너지학회 학술대회논문집 Vol.2019 No.4