An Environmental and Economic Assessment for Selecting the Optimal Ground Heat Exchanger by Considering the Entering Water Temperature
Abstract
:1. Introduction
2. Establishing the Basic Information and Selecting Key Factors Affecting Ground Heat Exchanger (GHE) Performances
2.1. Regional Factors of a Ground Source Heat Pump (GSHP) System
2.2. Design Factors of GHE for a GSHP System
- •
- Borehole length (BL): Borehole length usually affects largely the performances and cost of GHE, and, accordingly, multi-studies are being conducted on the design of optimal length. The optimal length is decided by all the factors affecting GHE such as underground environment, GHE components and G-function.
- •
- Number of boreholes and arrangement: The number and arrangement of boreholes is a factor that can affect the total length of the borehole and accounts for a significant portion of the cost. Besides, as the distribution of temperature transferred to underground varies according to a type of arrangement such as L-, U- and rectangle types, this factor affects the performances of boreholes.
- •
- Borehole spacing (BS): As heat capacity differs according to the type of ground, optimal spacing should be designed to prevent a reduction in GHE performances caused by intersection of the scopes of ground-source heats emitted and absorbed by each borehole.
- •
- Borehole diameter (BD): Borehole diameter is designed in consideration of the U-pipe through which fluid flows and the volume of grout that fills a borehole. As borehole thermal resistance is higher with an increase in the volume of grout, the performance decreases. If its volume is too small, the inner components protected by grout can be impaired. Thus, it is necessary to make proper thickness.
- •
- U-pipe spacing (PS), pipe size and pipe type: It is necessary to combine these factors to meet temperature load in consideration of the speed of fluid that flows inside a pipe and its related heat transfer capacity. These factors, which are related to the flowing fluid the pipe directly touches, require a strength and durability above a certain level.
- •
- Grout conductivity: Grout conductivity is an element that constitutes a borehole. The higher its thermal conductivity, the lower the overall borehole resistance.
- •
- Fluid type, flow rate: Fluid type and flow rate are variables of heat transfer that occur while fluid flows in a pipe. The usual mix with other material keeps fluid from freezing.
Table 1. Overview of key factor. Category Key Factor (Unit) References Regional Factor Ground temperature (°C), Soil type, Ground thermal conductivity (W/mK), Ground heat capacity (kJ/K·m3) [50,51,52,53] Ground Heat Exchanger Borehole length (BL) (m), Borehole spacing (BS) (m), Borehole diameter (BD) (mm), U-pipe spacing (PS) (mm), Number of boreholes: arrangement, Grout conductivity (W/mK), Borehole thermal resistance (K/(W/m)), Pipe type, Pipe size, Fluid type, Flow rate (L/s), Entering water temperature (°C) [54,55,56,57,58,59,60,61,62] Heat Pump Capacity (kW), Power input (kW), Heat of rejection (kW), Heat of extraction (kW), Coefficient of performance, Energy efficient rating, Entering water temperature (°C) [27,63,64,65] Figure 2. Components of Ground Source Heat Pump (GSHP) system. - •
- Borehole thermal resistance: Borehole thermal resistance, which is the thermal resistance of the overall borehole determined by a mix of the above factors, affects the design of a borehole.
- •
- Entering water temperature (EWT): EWT, which is an indicator that can evaluate the final performance by a mix of each key factor, is the GHE outlet temperature that meets the energy demand of the building [66]. To calculate the EWT, Equation (1) was used [67]. EWT is designed to provide water at a high temperature in the case of heating, and at a low temperature in the case of cooling, which can minimize the load of a heat pump. Hence, the design process of the GHE will be a core factor in the design of the overall GSHP system.
2.3. System Factors (Heat Pump) of GSHP System
3. Creating Possible Alternatives for the GHE Installation by Considering Entering Water Temperature (EWT)
3.1. Selection of a Facility for Case Study
- •
- According to the 2013 Annual End-Use Energy Statistics, the total energy and CO2 emissions from high energy consumption buildings that use 2000 toe per year reached 2,307,000 toe and 10,083,000 ton-CO2, respectively. The energy used by the schools among them reached 336,000 toe with CO2 emissions of 1,397,000 ton-CO2, which accounted for around 15% of the total amount used by buildings [1].
- •
- The GSHP system among an NRE system can be installed underground and designed around the systematic characteristics. Accordingly, the region with the lowest high building density should be selected.
- •
- A building that fully uses an air cooling and heating GSHP system was selected to calculate the environmental and economic effects of a GSHP system according to GHE scenarios.
Category | University Facilities |
---|---|
Year established | 2012 |
Location | Seoul |
Building type | Educational facility |
Electricity system | On-grid |
Heating system | Individual heating |
Progressive tax | No |
Floor space of gym | 1197.54 m2 |
Major energy service | Ground source heat pump (GSHP) |
Installation of capacity | Cooling: 204 kW/Heating: 218 kW |
Borehole | Length: 143 m/hole: 22 EA |
3.2. Establishment of a Basic GHE Energy Model
3.3. Establishment of GHE Design Scenarios Considering EWT
4. Environmental and Economic Assessment for Selecting the Optimal GHE by Considering EWT
4.1. System Boundary Conditions for Life-Cycle Assessment (LCA) and Life-Cycle Cost (LCC) Analyses
Maximum Entering Water Temperature: 23 °C, Minimum Entering Water Temperature: 5 °C | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Number of Boreholes: Arrangement (U) | Borehole Spacing | Grout Conductivity (W/mK) | U-Tube Type and Size | U-Tube Type and Size | U-Tube Type and Size | |||||||||
PN10, DN25 | PN10, DN32 | PN10, DN40 | ||||||||||||
Borehole Diameter | Borehole Diameter | Borehole Diameter | ||||||||||||
125 mm | 150 mm | 125 mm | 150 mm | 125 mm | 150 mm | |||||||||
U-Pipe Spacing | U-Pipe Spacing | U-Pipe Spacing | ||||||||||||
3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | |||
22 (EA): 8 × 8 | 4 m | 1 W/mK | 249.1 | 227.3 | 251.9 | 232.6 | 212.1 | 194.1 | 215.1 | 198.7 | 182.5 | 168.3 | 185.2 | 173.3 |
1.4 W/mK | 216.7 | 196.9 | 217.7 | 199.7 | 189.0 | 174.6 | 189.8 | 177.1 | 166.2 | 154.2 | 167.0 | 156.5 | ||
1.8 W/mK | 195.8 | 181.1 | 195.8 | 182.4 | 174.7 | 162.1 | 166.6 | 163.0 | 155.8 | 145.3 | 155.2 | 145.9 | ||
5 m | 1 W/mK | 247.6 | 225.4 | 250.5 | 231.1 | 210.4 | 192.5 | 213.4 | 197.2 | 180.3 | 166.0 | 183.1 | 170.8 | |
1.4 W/mK | 214.9 | 195.2 | 216.1 | 198.1 | 187.3 | 172.2 | 188.2 | 174.8 | 164.0 | 152.2 | 164.8 | 154.4 | ||
1.8 W/mK | 194.4 | 179.0 | 194.3 | 180.2 | 172.3 | 159.8 | 172.0 | 160.7 | 153.8 | 143.6 | 153.3 | 144.2 | ||
6 m | 1 W/mK | 246.6 | 224.0 | 249.5 | 229.9 | 209.1 | 191.4 | 207.8 | 195.8 | 179.2 | 165.1 | 181.9 | 169.7 | |
1.4 W/mK | 212.8 | 194.3 | 214.7 | 196.9 | 186.0 | 171.1 | 182.3 | 173.9 | 163.0 | 151.1 | 163.8 | 153.4 | ||
1.8 W/mK | 193.2 | 177.9 | 193.1 | 179.0 | 171.5 | 158.7 | 166.6 | 159.6 | 152.7 | 142.5 | 152.2 | 143.1 |
Number of Scenario | Max./Min. Entering Water Temperature | Number of Boreholes: Arrangement (U) | Borehole Spacing | Grout Conductivity (W/mK) | U-Tube Type and Size | Borehole Diameter | U-Pipe Spacing | Borehole Length |
---|---|---|---|---|---|---|---|---|
Scenario #1 | 30/5 °C | 22 (EA): 8 × 8 | 6 m | 1.8 W/mK | PN10, DN25 | 150 mm | 20 mm | 90 m |
Scenario #2 | 27/5 °C | 107 m | ||||||
Scenario #3 | 25/5 °C | 123 m | ||||||
Scenario #4 (exist GHE) | 23/5 °C | 143 m | ||||||
Scenario #5 | 20/5 °C | 195 m |
4.1.1. Establishment of System Boundary and Assumptions for LCA
- •
- Step 1. Goal and scope definition: Based on the information available in whole life cycle, environmental impact generated from the material manufacturing phase and use and maintenance stage are analyzed. The functional unit is defined as “the entire building supplied from design and use and maintenance for a whole service life”.
- •
- Step 2. LCI analysis: Using the LCI analysis results by life-cycle phase, the environmental-impact substances can be calculated. First, using input-output (I-O) LCA, energy source quantity utilized to produce the material for each life-cycle phase was calculated. Second, employing a process-based LCA, the national LCI database of South Korea established that the environmental-impact substances produced in the material and energy production process can be calculated (refer to Equation (5)) [71,72].
- •
- Step 3. Life-cycle impact assessment: LCIA converts the environmental-impact substances from the LCI analysis into the environmental impacts. LCIA is made up four categories: (i) Classification; (ii) Characterization; (iii) Normalization; (iv) Weighting [70,71]. In this study, classification and characterization were used to calculate the characterized environmental impact. The process of classification and characterization was calculated by Equation (6) [71,72]. To calculate characterized impacts (CCIl), the characterization factor (CFl,i) of each substance is required. Based on the “environmental labeling type III” standard, the characterized environmental impacts on six environmental-impact categories (i.e., RDP, GWP, ODP, AP, EP, and POCP) were presented.
- •
- Step 4. Results and interpretations: Using the estimated environmental impact, environmental and economic values are calculated. Environmental cost signifies the cost generated using end-point LCA methodology [70,73,74]. In this study, the environmental-cost conversion factor proposed in EPS 2000 was used to convert the environmental impact to environmental cost [75] (refer to Table A5). By analyzing the relative degree of the impact on the global environment of the environmental-impact categories, all the environmental impacts can be converted into environmental cost.
4.1.2. Establishment of System Boundary and Assumptions for LCC
- •
- Analysis approach: For the analysis approach, net present value (NPV) was selected for the LCC analysis. NPV is the method used to convert the future value of a design alternative into the present value by considering the discount rate and the time value (refer to Equation (7)). If NPV > 0, the project is deemed feasible; if NPV = 0, the break-even point is deemed to have been reached [76].
- •
- Analysis period: Generally, the analysis period for the LCC analysis can be established based on the service life of a product, which is based on the building’s structural type [71]. In this study, a 40-year time frame was used for the analysis period of the LCC.
- •
- Interest rate (refer to Equation (8)): In this study, the real discount rate was calculated using the nominal interest rate and various inflation rates (refer to Table A6) [71]. It can be used for converting various benefits and costs into present values.
- •
- Significant cost of ownership: From the life-cycle perspective, the initial investment cost and the use and maintenance cost need to be considered. The material consumption information was collected from the bill of quantities of the GHE and heat pump. The energy consumption information, on the other hand, was established through energy simulation, which was allocated to the energy cost among the use costs. Meanwhile, the repair rate, repair cycle, and replacement cycle of each material should be considered to calculate the cost in the maintenance phase. In this study, resources such as “Public Procurement Service”, “Ministry of National Defense” and “Implementing Regulations of the Housing Act in Korea (Appendix 5)”, which are provided by respectable institutions, were used [71].
4.2. Optimal GHE in Terms of Environmental and Economic Effects
- •
- First, life-cycle environmental cost: Saving effect of life-cycle environmental cost of Scenario #3 was determined at 2.2% compared with the existing GHE (Scenario #4). Although the initial investment environmental cost is higher than that of the existing GHE, the operation and maintenance environmental cost is lower than that of the existing GHE.
Table 5. Life-cycle environmental and economic cost of scenarios. Scenario Classification Environmental Impact Category Environmental Cost Economic Cost Total Cost RDP GWP ODP AP EP POCP (kg-Sb-eq) (kg-CO2-eq) (kg-CFC11-eq) (kg-SO2-eq) (kg-PO43-eq) (kg-C2H4-eq) Scenario #1 Initial cost 260 151,144 - 804 62 227 23,136 94,638 117,774 O and M cost 1275 724,427 - 1244 231 2 108,246 104,664 212,909 Total cost 1535 875,572 - 2047 293 229 131,381 199,302 330,683 Scenario #2 Initial cost 288 168,762 - 898 69 250 25,819 103,296 129,115 O and M cost 1150 653,432 - 1122 209 2 97,638 96,079 193,716 Total cost 1437 822,194 - 2020 277 252 123,457 199,375 322,831 Scenario #3 Initial cost 315 186,416 - 993 76 274 28,508 111,969 140,477 O and M cost 1096 622,723 - 1069 199 2 93,049 92,421 185,469 Total cost 1411 809,139 - 2062 275 276 121,557 204,390 325,947 Scenario #4 Initial cost 352 210,223 - 1121 85 305 32,133 123,610 155,743 O and M cost 1085 616,970 - 1059 197 2 92,189 91,824 184,014 Total cost 1437 827,193 - 2180 282 307 124,322 215,434 339,756 Scenario #5 Initial cost 439 265,811 - 1419 107 379 40,600 150,977 191,578 O and M cost 966 549,094 - 943 175 2 82,047 83,713 165,760 Total cost 1405 814,905 - 2362 282 381 122,647 234,690 357,337 Notes: Unit (US$); operation and maintenance phase (O and M); resource depletion potential (RDP); global warming potential (GWP); ozone layer depletion potential (ODP); acidification potential (AP); eutrophication potential (EP); and photochemical oxidation potential (POCP). - •
- Second, life-cycle economic cost: Saving effect of life-cycle economic cost of Scenario #1 was determined to be 7.5% as compared to the existing GHE (Scenario #4). Although the initial investment cost is higher than that of the existing GHE, the operation and maintenance cost is lower than that of the existing GHE.
- •
- Third, life-cycle environmental and economic cost: Saving effect of total cost of Scenario #2 was determined to be 5.0% compared with the existing GHE (Scenario #4). Although the initial investment cost is higher than that of the existing GHE, the operation and maintenance cost is lower than that of the existing GHE.
5. Conclusions
- •
- Life-cycle environmental cost: Saving effect of life-cycle environmental cost of Scenario #3 was determined to be 2.2% compared with existing GHE (Scenario #4).
- •
- Life-cycle economic cost: Saving effect of life-cycle economic cost of Scenario #1 was determined at 7.5% compared with existing GHE (Scenario #4).
- •
- Life-cycle environmental and economic cost: Saving effect of total cost of scenario #2 was determined at 5.0% compared with existing GHE (Scenario #4).
Acknowledgements
Author Contributions
Conflicts of Interest
Appendix
Maximum Entering Water Temperature: 30 °C, Minimum Entering Water Temperature: 5 °C | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Number of Boreholes: Arrangement (U) | Borehole Spacing | Grout Conductivity (W/mK) | U-Tube Type and Size | U-Tube Type and Size | U-Tube Type and Size | |||||||||
PN10, DN25 | PN10, DN32 | PN10, DN40 | ||||||||||||
Borehole Diameter | Borehole Diameter | Borehole Diameter | ||||||||||||
125 mm | 150 mm | 125 mm | 150 mm | 125 mm | 150 mm | |||||||||
U-Pipe Spacing | U-Pipe Spacing | U-Pipe Spacing | ||||||||||||
3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | |||
22 (EA): 8 × 8 | 4 m | 1 W/mK | 157.4 | 142.4 | 159.3 | 145.8 | 134.1 | 123.0 | 135.7 | 126.3 | 114.7 | 105.7 | 116.4 | 108.8 |
1.4 W/mK | 136.5 | 125.1 | 137.1 | 126.9 | 119.1 | 109.7 | 119.7 | 111.3 | 104.2 | 96.9 | 104.8 | 98.2 | ||
1.8 W/mK | 124.3 | 113.9 | 124.3 | 114.6 | 109.8 | 101.5 | 109.6 | 102.1 | 97.9 | 91.8 | 97.5 | 92.2 | ||
5 m | 1 W/mK | 156.1 | 141.4 | 157.9 | 144.7 | 133.2 | 121.9 | 134.8 | 125.1 | 113.5 | 104.3 | 115.3 | 107.5 | |
1.4 W/mK | 135.6 | 123.9 | 136.2 | 125.8 | 117.9 | 108.5 | 118.5 | 110.1 | 102.9 | 95.7 | 103.4 | 97.0 | ||
1.8 W/mK | 123.2 | 112.7 | 123.1 | 113.4 | 108.5 | 100.2 | 108.4 | 100.8 | 96.6 | 90.6 | 96.3 | 91.0 | ||
6 m | 1 W/mK | 155.4 | 140.7 | 157.3 | 144.0 | 132.4 | 120.8 | 134.0 | 124.2 | 112.7 | 103.8 | 114.4 | 106.9 | |
1.4 W/mK | 134.9 | 123.0 | 136.5 | 124.8 | 117.1 | 107.8 | 117.7 | 109.4 | 102.3 | 95.3 | 102.9 | 96.6 | ||
1.8 W/mK | 122.3 | 111.9 | 122.2 | 112.7 | 107.9 | 99.8 | 107.7 | 100.3 | 96.2 | 90.1 | 95.9 | 90.4 |
Maximum Entering Water Temperature: 23 °C, Minimum Entering Water Temperature: 5 °C | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Number of Boreholes: Arrangement (U) | Borehole Spacing | Grout Conductivity (W/mK) | U-Tube Type and Size | U-Tube Type and Size | U-Tube Type and Size | |||||||||
PN10, DN25 | PN10, DN32 | PN10, DN40 | ||||||||||||
Borehole Diameter | Borehole Diameter | Borehole Diameter | ||||||||||||
125 mm | 150 mm | 125 mm | 150 mm | 125 mm | 150 mm | |||||||||
U-Pipe Spacing | U-Pipe Spacing | U-Pipe Spacing | ||||||||||||
3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | |||
22 (EA): 8 × 8 | 4 m | 1 W/mK | 186.5 | 169.1 | 188.5 | 173.1 | 158.4 | 144.6 | 160.7 | 148.5 | 135.7 | 122.4 | 133.7 | 125.8 |
1.4 W/mK | 161.8 | 147.0 | 162.7 | 149.3 | 140.3 | 130.4 | 141.0 | 132.2 | 124.1 | 112.9 | 121.5 | 114.4 | ||
1.8 W/mK | 146.1 | 134.9 | 146.0 | 135.7 | 130.5 | 120.8 | 130.3 | 121.5 | 114.0 | 107.0 | 113.5 | 107.4 | ||
5 m | 1 W/mK | 185.0 | 167.5 | 187.2 | 171.5 | 156.8 | 143.3 | 159.0 | 147.1 | 132.0 | 122.1 | 133.6 | 125.6 | |
1.4 W/mK | 160.0 | 145.7 | 161.0 | 147.9 | 139.1 | 129.1 | 139.8 | 131.0 | 120.5 | 112.3 | 121.1 | 113.9 | ||
1.8 W/mK | 144.8 | 133.8 | 144.8 | 134.5 | 129.2 | 119.4 | 129.0 | 120.0 | 113.4 | 106.3 | 113.0 | 106.7 | ||
6 m | 1 W/mK | 184.1 | 166.9 | 186.3 | 170.8 | 156.0 | 142.5 | 158.2 | 146.3 | 131.9 | 121.9 | 133.6 | 125.3 | |
1.4 W/mK | 159.3 | 144.9 | 160.0 | 147.1 | 138.3 | 128.0 | 139.0 | 129.9 | 120.1 | 111.9 | 120.8 | 113.5 | ||
1.8 W/mK | 144.1 | 132.9 | 144.0 | 133.7 | 128.0 | 118.3 | 127.9 | 118.9 | 113.0 | 105.9 | 112.6 | 107.0 |
Maximum Entering Water Temperature: 23 °C, Minimum Entering Water Temperature: 5 °C | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Number of Boreholes: Arrangement (U) | Borehole Spacing | Grout Conductivity (W/mK) | U-Tube Type and Size | U-Tube Type and Size | U-Tube Type and Size | |||||||||
PN10, DN25 | PN10, DN32 | PN10, DN40 | ||||||||||||
Borehole Diameter | Borehole Diameter | Borehole Diameter | ||||||||||||
125 mm | 150 mm | 125 mm | 150 mm | 125 mm | 150 mm | |||||||||
U-Pipe Spacing | U-Pipe Spacing | U-Pipe Spacing | ||||||||||||
3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | |||
22 (EA): 8 × 8 | 4 m | 1 W/mK | 212.6 | 192.9 | 215.4 | 197.0 | 181.5 | 166.3 | 184.1 | 170.4 | 155.1 | 142.6 | 157.5 | 146.8 |
1.4 W/mK | 185.2 | 168.8 | 186.1 | 171.3 | 161.3 | 148.1 | 162.1 | 150.3 | 140.8 | 132.2 | 141.5 | 133.8 | ||
1.8 W/mK | 168.0 | 154.0 | 168.0 | 155.0 | 148.1 | 137.7 | 147.9 | 138.3 | 133.4 | 125.1 | 132.9 | 125.6 | ||
5 m | 1 W/mK | 211.2 | 191.5 | 213.8 | 195.7 | 179.8 | 164.4 | 182.2 | 168.6 | 153.4 | 141.2 | 155.7 | 145.3 | |
1.4 W/mK | 183.5 | 166.9 | 184.4 | 169.5 | 159.3 | 146.4 | 160.2 | 148.6 | 139.5 | 130.8 | 140.1 | 132.6 | ||
1.8 W/mK | 166.1 | 152.3 | 166.1 | 153.3 | 146.5 | 136.5 | 146.3 | 137.1 | 132.1 | 123.5 | 131.6 | 124.0 | ||
6 m | 1 W/mK | 210.1 | 190.6 | 212.8 | 197.8 | 178.8 | 163.6 | 181.1 | 167.7 | 182.9 | 140.3 | 154.8 | 144.4 | |
1.4 W/mK | 182.4 | 166.3 | 183.4 | 168.5 | 158.4 | 145.5 | 159.3 | 147.7 | 138.5 | 129.6 | 139.2 | 131.5 | ||
1.8 W/mK | 165.3 | 151.4 | 165.2 | 152.4 | 145.6 | 135.5 | 145.4 | 136.1 | 130.9 | 122.1 | 130.4 | 122.6 |
Maximum Entering Water Temperature: 23 °C, Minimum Entering Water Temperature: 5 °C | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Number of Boreholes: Arrangement (U) | Borehole Spacing | Grout Conductivity (W/mK) | U-Tube Type and Size | U-Tube Type and Size | U-Tube Type and Size | |||||||||
PN10, DN25 | PN10, DN32 | PN10, DN40 | ||||||||||||
Borehole Diameter | Borehole Diameter | Borehole Diameter | ||||||||||||
125 mm | 150 mm | 125 mm | 150 mm | 125 mm | 150 mm | |||||||||
U-Pipe Spacing | U-Pipe Spacing | U-Pipe Spacing | ||||||||||||
3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | 3 mm | 20 mm | |||
22 (EA): 8 × 8 | 4 m | 1 W/mK | 338.8 | 306.9 | 342.7 | 314.1 | 287.2 | 263.6 | 291.4 | 270.1 | 247.3 | 230.1 | 250.9 | 236.0 |
1.4 W/mK | 293.8 | 267.9 | 295.4 | 271.3 | 255.8 | 237.6 | 257.2 | 240.7 | 226.7 | 209.7 | 228.5 | 213.0 | ||
1.8 W/mK | 266.5 | 245.9 | 266.4 | 247.2 | 237.7 | 220.9 | 237.5 | 222.1 | 211.9 | 198.8 | 211.1 | 199.1 | ||
5 m | 1 W/mK | 337.1 | 305.4 | 341.1 | 312.4 | 285.5 | 261.8 | 289.6 | 268.7 | 245.5 | 227.2 | 249.0 | 233.9 | |
1.4 W/mK | 291.6 | 266.1 | 293.3 | 269.9 | 254.0 | 235.5 | 255.4 | 238.8 | 224.2 | 206.9 | 225.4 | 210.6 | ||
1.8 W/mK | 264.6 | 243.8 | 264.5 | 245.3 | 235.7 | 218.3 | 235.4 | 219.5 | 209.6 | 195.9 | 208.8 | 196.6 | ||
6 m | 1 W/mK | 335.9 | 304.2 | 340.0 | 311.2 | 284.3 | 260.5 | 288.4 | 267.7 | 274.3 | 225.5 | 247.6 | 232.3 | |
1.4 W/mK | 290.3 | 264.9 | 292.0 | 268.9 | 252.8 | 234.0 | 254.1 | 237.0 | 222.2 | 205.1 | 223.7 | 208.7 | ||
1.8 W/mK | 263.4 | 242.3 | 263.2 | 243.8 | 234.2 | 216.4 | 233.9 | 217.6 | 207.3 | 194.1 | 206.5 | 194.9 |
Environmental Impact | Environmental Cost Conversion Factor |
---|---|
resource depletion potential (RDP) | 2.439 US$/kg-Sb-eq |
global warming potential (GWP) | 0.167 US$/kg-CO2-eq |
ozone layer depletion potential (ODP) | 145.172 US$/kg-CFC11-eq |
acidification potential (AP) | 0.032 US$/kg-SO2-eq |
eutrophication potential (EP) | 0.029 US$/kg-PO43-eq |
photochemical oxidation potential (POCP) | 2.675 US$/kg-C2H4-eq |
Classification | Detailed Classification | Detailed Description |
---|---|---|
Analysis Approach | Present Worth Method (NPV40) | |
Analysis Period | 40 years | |
Realistic Discount Rate | Interest | 3.30% |
Electricity | 0.66% | |
Gas | 0.11% | |
KCERs | 2.66% | |
Significant Cost of Ownership | Initial construction cost | Initial investment cost |
Operation and maintenance cost | Replacement/repair cost | |
Energy consumption cost | ||
Operation and maintenance benefit | Gas savings, electricity savings | |
Benefit from KCERs |
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Kim, J.; Hong, T.; Chae, M.; Koo, C.; Jeong, J. An Environmental and Economic Assessment for Selecting the Optimal Ground Heat Exchanger by Considering the Entering Water Temperature. Energies 2015, 8, 7752-7776. https://doi.org/10.3390/en8087752
Kim J, Hong T, Chae M, Koo C, Jeong J. An Environmental and Economic Assessment for Selecting the Optimal Ground Heat Exchanger by Considering the Entering Water Temperature. Energies. 2015; 8(8):7752-7776. https://doi.org/10.3390/en8087752
Chicago/Turabian StyleKim, Jimin, Taehoon Hong, Myeongsoo Chae, Choongwan Koo, and Jaemin Jeong. 2015. "An Environmental and Economic Assessment for Selecting the Optimal Ground Heat Exchanger by Considering the Entering Water Temperature" Energies 8, no. 8: 7752-7776. https://doi.org/10.3390/en8087752