• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2381-2384
• /
• 2008

The heat exchange between the Borehole Heat Exchanger(BHE) and the surrounding ground depends directly on ground thermal conductivity k at the certain site. The k is thus a key parameter in designing BHE and coupled geothermal heat pump systems. Currently, although a thermal hydraulic Response Test(TRT) is mostly used in practice, the thermal hydraulic TRT needs additional power and is generally time-consuming. A new, simple wireless probe for hi-speed k determination was introduced in this paper. This technique using a wireless probe is less time-consuming and requires no external source of energy for measurement and predicts local thermal properties by measuring soil temperatures along the depth. Measured temperature data along the depth was analyzed. As a result, the electronic wireless probe can replace the conventional hydraulic TRT method after carrying out the additional research on a lot of local heat flow, etc.

• The Journal of Engineering Geology
• /
• v.23 no.4
• /
• pp.389-398
• /
• 2013

Studies of the thermal properties of various rock types obtained from several locations in Korea have revealed significant differences in thermal conductivities in the thermal response test (TRT), which has been applied to the design of a ground-source heat pump system. In the present study, we aimed to compare the thermal conductivities of the samples with those obtained by TRT. The thermal conductivities of soil and rock samples were 1.32W/m-K and 2.88 W/m-K, respectively. In comparison, the measured TRT value for thermal conductivity was 3.13W/m-K, which is 10% higher than that of the rock samples. We consider that this difference may be due to groundwater flow because abundant groundwater is present in the study area and has a hydraulic conductivity of 0.01. It is natural to consider that the object of TRT is to calculate the original thermal conductivity of the ground, following the line source theory. Therefore, we conclude that the TRT applied to a domestic standing column type well is not suitable for a line source theory. To solve these problems, values of thermal conductivity measured directly from samples should be used in the design of ground-source heat pump systems.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.06a
• /
• pp.600-603
• /
• 2009

We compared relative importance of thermal conductivity and initial ground temperature in designing borehole heat exchanger network and also we test accuracy of ground temperature estimation in thermal response test using a proven 3-D T-H modeler. The effect of error in estimating ground temperature on calculated total length of borehole heat exchanger was more than 3 times larger than the case of thermal conductivity in maximum 20% error range. Considering 10% of error in estimating thermal conductivity is generally acceptable, we have to define the initial ground temperature within 5% confidence level. Utilizing the mean annual ground surface temperature and the geothermal gradient map compiled so far can be a economic way of estimating ground temperature with some caution. When performing thermal response test for estimating ground temperature as well as measuring thermal conductivity, minimum 100 minutes of ambient circulation is required, which should be even more in case of very cold and hot seasons.

• The Journal of Engineering Geology
• /
• v.21 no.1
• /
• pp.35-43
• /
• 2011

Time series analysis was applied to groundwater level, water temperature, and electrical conductivity data obtained from monitoring wells around ground-source heat pumps at Sangji University of Wonju (standing column well type) and at Jungwon University of Goesan (closed loop type), from 21 May to 12 October 2010. We found large temporal variations in the characteristics of groundwater at Wonju, but only minor variations at Goesan. These results may improve our understanding of the effects of ground-source heat pumps on the characteristics of surrounding groundwater, according to the installation method for the pumps.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.27 no.11
• /
• pp.581-586
• /
• 2015

In this study, an analysis was performed on the performance of the solar water heating system with geo-thermal heat pump for a detached house. This system has a flat plate solar collector ($8\;m^2$) and a 3 RT heat pump. The heat pump acts as an auxiliary heater of the solar water heating system. These systems were installed at four individual houses with the same area of $100\;m^2$. The monitoring results for one year are as follows. (1) The average daily operating time of the solar system appeared to be 313 minutes in spring (intermediate season), and 135 minutes and 76 minutes in winter and summer respectively. The reason for the short operating time in summer is the high storage temperature due to low water heating load. The high storage temperature is caused by a decrease in collecting efficiency as well as by overheating. (2) The geothermal heat pump as an auxiliary heater mainly operates on days of poor insolation during the winter season. (3) Despite controlling for total house area, hot water consumption varies greatly according to the number of people in the family, hot water usage habits, etc. (4) The yearly solar fraction was 69.8 to 91.5 percent, which exceeds the maximum value of 80% as recommended by ASHRAE. So the solar collector area of $8\;m^2$ appeared to be somewhat greater for the house with an area of $100\;m^2$. (5) The observed annual efficiency of solar systems was relatively low at 13.5 to 23.6%, which was analyzed to be due to the decrease in thermal efficiency and the overheating caused by a high solar fraction.

• Tunnel and Underground Space
• /
• v.21 no.1
• /
• pp.11-19
• /
• 2011

Geothermal energy is believed to be an important source among the renewable energy sources to provide the base load electricity. Although there has been a drastic increase in the use of geothermal heat pump in Korea, there is no geothermal power plant in operation in Korea. Fortunately, the first EGS (Enhanced Geothermal System) Project in Korea has started in Dec 2010. This five year project is divided into two stages; two years for exploration and drilling of 3 km depth to confirm the minimum target temperature of 100 degrees, and another three years composed drilling 5 km doublet, hydraulic stimulation of geothermal reservoir with expected temperature of 180 degrees (40 kg/s) and construction of MW geothermal power plant in the surface. This EGS project would be a landmark effort that invited a consortium of industry, research institutes and university with expertises in the fields of geology, hydrogeology, geophysics, geomechanics and plant engineering.

• 한국태양에너지학회:학술대회논문집
• /
• 2009.04a
• /
• pp.91-96
• /
• 2009

First, the base model of multi-family residential buildings are selected, and then the $CO_2$ reduction building technologies that are applicable for multi-family residential buildings are induced by analyzing the examples and then an optimal plan for when the $CO_2$ reduction building technologies can be integrated and applied to the base model was formulated. In the results of converting the energy consumption and reduction amount from the building technologies into $CO_2$ emissions to analyze the distribution ratio compared to the entire $CO_2$ emissions; the heat recovery ventilator is 0.5%, the photovoltaic system is $1.9%{\sim}5.9%$, the solar hot water heating system is $6.3%{\sim}13.1%$ and the ge thermal heat-pump system is 39.0% when both heating and hot water heating are applied. An optimally integrated application method for the building technologies is in charge of heating and hot water heating through the geothermal source heat pump system and in charge of the electricity load through the photovoltaic system(45.2%).

• Economic and Environmental Geology
• /
• v.39 no.3 s.178
• /
• pp.255-268
• /
• 2006

Recent 22-year (1981-2002) meteorological data of 58 Korea Meteorological Adminstration (KMA) station were analyzed to investigate spatial and temporal variation of surface air temperature (SAT) and ground surface temperature (GST) in Korea. Based on the KMA data, multiple linear regression (MLR) models, having two regression variables of latitude and altitude, were presented to predict mean surface air temperature (MSAT) and mean ground surface temperature (MGST). Both models showed a high accuracy of prediction with $R^2$ values of 0.92 and 0.94, respectively. The prediction of MGST is particularly important in the areas of geothermal energy utilization, since it is a critical parameter of input for designing the ground source heat pump system. Thus, due to a good performance of the MGST regression model, it is expected that the model can be a useful tool for preliminary evaluation of MGST in the area of interest with no reliable data. By a simple linear regression, temporal variation of SAT was analyzed to examine long-term increase of SAT due to the global warming and the urbanization effect. All of the KMA stations except one showed an increasing trend of SAT with a range between 0.005 and $0.088^{\circ}C/yr$ and a mean of $0.043^{\circ}C/yr$. In terms of meteorological factors controlling variation of GST, the effects of solar radiation, terrestrial radiation, precipitation, and snow cover were also discussed based on quantitative and qualitative analysis of the meteorological data.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.19 no.4
• /
• pp.27-38
• /
• 2023

The Government the Republic of Korea is showing a lot of interest in net zero-energy buildings (NZEBs) to reduce energy consumption of buildings and to promote green growth policy in construction sector. The application of building passive technologies and renewable energies is essential to achieving NZEBs. Green remodeling reinforced the insulation of the exterior walls and roofs of the buildings and replaced high-efficiency windows and doors. In this study, the energy performance before and after green remodeling applied in a detached house was comparatively analyzed for baseline scenario and three different ones, ALT 1, ALT 2 and ALT 3. A building modeling and simulation software (DesignBuilder V7.0) with EnergyPlus (V9.4) calculation engine was used to calculate the energy demand and energy consumption for each scenario. Based on the calculation results of the building's energy demand for baseline, it was determined that the target building required more heating energy than cooling energy. The simulation results also showed that the implementation of building envelope performance improvement technologies (ALT 1) could notably decrease the heating energy consumption of the building. After the remodeling (ALT 1), the source energy consumption per unit floor area was assessed to be reduced by 65.2%, compared to prior remodeling of 338.7 kWh/m² -y. Meanwhile, ALT 2 can achieve energy savings of 67.7% and ALT 3 can achieve savings of 73.1%. Following completion of the remodeling project, actual construction costs, and on-site measurements and verification results will be gathered and compared with the simulation results. Additionally, economic analysis including construction costs and payback period will be conducted using actual site data.

• Journal of Soil and Groundwater Environment
• /
• v.10 no.4
• /
• pp.54-61
• /
• 2005

An aquifer thermal energy storage (ATES) system can be very cost-effective and renewable energy sources, depending on site-specific parameters and load characteristics. In order to develop the ATES system which has certain hydrogeological characteristics, understanding the thermohydraulic process of an aquifer is necessary for a proper design of an aquifer heat storage system under given conditions. The thermohydraulic transfer for heat storage was simulated according to two sets of simple pumping and waste water reinjection scenarios of groundwater heat pump system operation in a two-layered aquifer model. In the first set of the scenarios, the movement of the thermal front and groundwater level was simulated by changing the locations of injection and pumping wells in a seasonal cycle. However, in the second set the simulation was performed in the state of fixing the locations of pumping and injection wells. After 365 days simulation period, the shape of temperature distribution was highly dependent on the injected water temperature and the distance from the injection well. A small temperature change appeared on the surface compared to other simulated temperature distributions of 30 and 50 m depths. The porosity and groundwater flow characteristics of each layer sensitively affected the heat transfer. The groundwater levels and temperature changes in injection and pumping wells were monitored and the thermal interference between the wells was analyzed to test the effectiveness of the heat pump operation method applied.