# Multiple-Criteria Decision-Making for Assessing the Enhanced Geothermal Systems

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## Abstract

**:**

## 1. Introduction

## 2. Background

#### 2.1. Decision-Making Support Tool for Optimal Usage of Geothermal Energy (DMS-TOUGE)

_{2}emission schemes, security of energy supply issues). In order to better anticipate and include future events, different possible scenarios are evaluated and accounted and accordingly the tool can use forecasted data (load, prices, etc.) which can occur over the operation lifetime of EGS technology. Some of the most important environmental (external) factors that are integrated into the tool are: proximity of nearest suitable power system grid and/or nearest suitable district heating system where EGS could be integrated into, proximity and availability of water for water cooling mechanism, possibility for different usage of geothermal energy for agricultural, industrial and district heating needs, and geopolitical environment and relevant legislative framework. The DMS-TOUGE relies on optimization algorithms to value/quantify different technologies. It will be used to quantify environmental and social impacts and calculate system levelized cost of energy (sLCOE) of technology in order to find the best-suited option for a given site. Moreover, when assessing the best-suited option and technology for a given site, malicious and faulty components should be taken into account since, in reality, it is illusory to expect that all components of the geothermal system are functioning without problems. An example of addressing this issue is presented in Reference [25]. Therefore, it is mandatory to include any possible risks involved with different components of the system. As an integral part of the DMS-TOUGE, any possible risks will be analyzed, such as market (price) risks and technical issues: thermal effects, scaling effect, radioactive deposits, and mechanical effect of the casing through the conditional value-at-risk (CVaR) measure [26,27,28]. Technical issues and risk of escalating costs need to be managed and hedged because of the potential damages likely to take place on an operational plant. The DMS-TOUGE will be verified and validated based on the comparison between tool output and real-life expert analyses on existing operating EGS sites and also historical data related to existing EGS sites. Output data of DMS-TOUGE will be available as raw data or in a form of directives and suggestions that are suitable for decision makers and investors. The raw data will be processed by a special subprocess, a separate MCDM, into a decision. The MCDM will be further discussed in Section 3. The schematic depiction of the main features of the DMS-TOUGE is shown in Figure 1. It should be emphasized that DMS-TOUGE as a whole is still in the development phase, and some parts have been modelled, including MCDM described later.

#### 2.2. Geothermal Project Development Phases

- Discover and establish a viable resource;
- Develop the project to the point necessary to obtain the power purchase agreement (PPA);
- Complete the project development once the PPA is obtained, and
- Operate the power plant facility.

#### 2.3. Extraction Technology

#### 2.4. Geothermal Facility Arrangement

## 3. Multiple-Criteria Decision-Making Analysis

#### 3.1. First Criterion: Installed Power, ${x}_{i,1}$

#### 3.2. Second Criterion: Fluid Heat Flow, ${x}_{i,2}$

^{3}/s), $\rho $ is fluid density (kg/m

^{3}), ${c}_{p}$ is specific heat capacity of fluid at constant pressure (J/kg·K). ${T}_{H}$ is the fluid temperature at the wellhead (°C), ${T}_{C}$ is the fluid temperature at the exit of the steam turbine (°C).

^{3}/h and 100 m

^{3}/h and when temperatures are between 80 °C and 160 °C, since those ranges correspond to operative conditions for an ORC plant. For this criterion, the temperature range is modified for the values between 60 °C and 160 °C, since one of the focus of the ongoing H2020 MEET project is to make those temperatures also exploitable (Table 2).

#### 3.3. Third Criterion: Theoretical Maximum Efficiency, ${x}_{i,3}$

#### 3.4. Fourth Criterion: Geothermal Gradient, ${x}_{i,4}$

#### 3.5. Fifth Criterion: The Fluid Temperature at Wellhead, ${x}_{i,5}$

#### 3.6. Sixth Criterion: Global Efficiency, ${x}_{i,6}$

#### 3.7. Seventh Criterion: Corrosion and Scaling Hazard, ${x}_{i,7}$

#### 3.8. Eighth Criterion: Distance from Power/Heating Grid, ${x}_{i,8}$

#### 3.9. Ninth Criterion: Load Factor, ${x}_{i,9}$

#### 3.10. Tenth Criterion: sLCOE, ${x}_{i,10}$

#### 3.11. Eleventh Criterion: Social Impact, ${x}_{i,11}$

#### 3.12. Twelfth Criterion: Environmental Impact, ${x}_{i,12}$

^{2}/kW, and the range was estimated according to Reference [37]. The noise impact during routine operation is mainly caused by cooling towers and electrical transformers, and according to Reference [38], typical acceptable levels are 71–83 dB at 900 m distance from the facility. When considering atmospheric emissions, closed cycles, such as binary plants, have no gaseous emissions or they are close to zero and so do not contribute to air pollution. Considering objects of interest in this research (Figure 3), the impact on surface waters can be excluded. Groundwater contamination may occur if the casings in reinjection wells should fail, allowing fluid to leak. According to WHO, the range of total dissolved solids (TDS) and pH values was determined for the quantification of this sub-criterion. Radioactivity is mainly caused by interaction between the geothermal fluid and certain formations containing radioactive elements. As emphasized in Reference [39], the content of radionuclides in acidic magmatic rocks is generally higher compared to sedimentary rocks. Furthermore, uranium (U) and thorium (Th) are the most common radioactive elements found in granites. As defined in Reference [39], different types of rocks can contain different radioelements. Therefore, this sub-criterion is defined with the ranges of the forenamed most common radioactive elements but also taking into account the type of the rock – granitic rocks, shales, basaltic rocks, sandstones, and carbonates - in ascending order of the weights. The environmental impact criterion will be obtained by the average of performances of the following sub-criterions shown in Table 12:${x}_{i,12,1}$ subsidence sub-criterion, ${x}_{i,12,2}$ potential seismicity sub-criterion, ${x}_{i,12,3}$ land use sub-criterion, ${x}_{i,12,4}$ noise sub-criterion, ${x}_{i,12,5}$ potential water contamination sub-criterion, and ${x}_{i,12,6}$ radioactivity sub-criterion. Each sub-criterion will be evaluated with a weight in a range from 1 to 5.

## 4. Results

#### 4.1. Economic Parameters

#### 4.2. First Scenario—Electricity Production Only

#### 4.3. Second Scenario—Heat Production Only

#### 4.4. Sensitivity Analysis

#### 4.5. Discussion

## 5. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

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**Figure 1.**Schematic description of the main processes in Decision-Making Support Tool for Optimal Usage of Geothermal Energy (DMS-TOUGE).

**Figure 2.**Capital costs included in Decision-Making Support Tool for Optimal Usage of Geothermal Energy (DMS-TOUGE) determination of a system levelized cost of energy (sLCOE).

**Figure 3.**Extraction technologies: (

**a**) producer-injector doublet, (

**b**) borehole heat exchanger single U-tube, (

**c**) borehole heat exchanger double U-tube, (

**d**) coaxial borehole heat exchanger.

**Figure 4.**Schematic description of the possible end-user options: (

**a**) direct use, (

**b**) only electricity production, (

**c**) combined heat and power (CHP)–series configuration, (

**d**) CHP–parallel configuration.

**Figure 5.**Schematic diagram of a basic binary cycle geothermal power plant: (

**a**) water-cooled condenser and (

**b**) air-cooled condenser.

**Figure 6.**Total employment – full-time jobs function depending on the installed capacity of the project

**Figure 7.**Tornado plot showing the sensitivity of the calculated levelized cost of energy (LCOE) to changes in a selection of parameters.

Ratio (p.u.) | $0\text{}\le {\text{}\mathit{P}/\mathit{P}}_{\mathit{r}}\text{}0.3$ | $0.3\text{}\le \mathit{P}/{\mathit{P}}_{\mathit{r}}\text{}0.6$ | $0.6\text{}\le \text{}\mathit{P}/{\mathit{P}}_{\mathit{r}}\text{}0.9$ | $0.9\text{}\le \mathit{P}/{\mathit{P}}_{\mathit{r}}\text{}1.2$ | $1.2\text{}\le \mathit{P}/{\mathit{P}}_{\mathit{r}}\text{}\mathbf{\infty}$ |
---|---|---|---|---|---|

${\mathit{x}}_{\mathit{i},\mathbf{1}}$ | 1 | 2 | 3 | 4 | 5 |

Ratio | $1.67\text{}\le \frac{\mathit{q}}{{\mathit{T}}_{\mathit{H}}}\text{}\mathbf{\infty}$ | $0.679\text{}\le \frac{\mathit{q}}{{\mathit{T}}_{\mathit{H}}}\text{}1.67$ | $0.357\text{}\le \frac{\mathit{q}}{{\mathit{T}}_{\mathit{H}}}\text{}0.679$ | $0.056\text{}\le \frac{\mathit{q}}{{\mathit{T}}_{\mathit{H}}}\text{}0.357$ | $0\text{}\le \frac{\mathit{q}}{{\mathit{T}}_{\mathit{H}}}\text{}0.056$ |
---|---|---|---|---|---|

${\mathit{x}}_{\mathit{i},\mathbf{2}}$ | 1 | 2 | 3 | 4 | 5 |

Efficiency of Conversion for ORC Plant (%) | ${\mathit{\eta}}_{\mathit{max}}\text{}\text{}4$ | $4\text{}\le {\text{}\mathit{\eta}}_{\mathit{max}}\text{}\text{}6$ | $6\text{}\le {\text{}\mathit{\eta}}_{\mathit{max}}\text{}\text{}10$ | $10\text{}\le {\text{}\mathit{\eta}}_{\mathit{max}}\text{}12$ | ${\mathit{\eta}}_{\mathit{max}}\text{}\ge \text{}12$ |

${\mathit{x}}_{\mathit{i},\mathbf{3}}$ | 1 | 2 | 3 | 4 | 5 |

Efficiency of Conversion for Other Cases (%) | ${\mathit{\eta}}_{\mathit{max}}\text{}\text{}\mathbf{30}$ | $\mathbf{30}\text{}\le {\mathit{\eta}}_{\mathit{max}}\text{}\text{}\mathbf{40}$ | $\mathbf{40}\text{}\le {\mathit{\eta}}_{\mathit{max}}\text{}\text{}\mathbf{50}$ | $\mathbf{50}\text{}\le {\mathit{\eta}}_{\mathit{max}}\text{}\mathbf{60}$ | ${\mathit{\eta}}_{\mathit{max}}\text{}\ge \text{}\mathbf{60}$ |

${\mathit{x}}_{\mathit{i},\mathbf{3}}$ | 1 | 2 | 3 | 4 | 5 |

Geo.gra. (°C/100 m) | ${\mathit{G}}_{\mathit{T}}\text{}\text{}0.5$ | $0.5\text{}\le {\text{}\mathit{G}}_{\mathit{T}}\text{}\text{}2$ | $2\text{}\le {\text{}\mathit{G}}_{\mathit{T}}\text{}\text{}4$ | $4\text{}\le {\text{}\mathit{G}}_{\mathit{T}}\text{}\text{}6$ | ${\mathit{G}}_{\mathit{T}}\text{}\ge \text{}6$ |
---|---|---|---|---|---|

${\mathit{x}}_{\mathit{i},\mathbf{4}}$ | 1 | 2 | 3 | 4 | 5 |

Temp. (°C) | ${\mathit{T}}_{\mathit{H}}\text{}\le \text{}60$ | ${60\text{}\text{}\mathit{T}}_{\mathit{H}}\text{}\le \text{}90$ | ${90\text{}\text{}\mathit{T}}_{\mathit{H}}\text{}\le \text{}120$ | ${120\text{}\text{}\mathit{T}}_{\mathit{H}}\text{}\le \text{}150$ | ${150\text{}\text{}\mathit{T}}_{\mathit{H}}\text{}\le \text{}\mathbf{\infty}$ |
---|---|---|---|---|---|

${\mathit{x}}_{\mathit{i},\mathbf{5}}$ | 1 | 2 | 3 | 4 | 5 |

Global Efficiency | ${\mathit{\eta}}_{\mathit{G}}<\text{}0.2$ | $0.2\text{}\le {\text{}\mathit{\eta}}_{\mathit{G}}\text{}0.3$ | $0.3\text{}\le {\text{}\mathit{\eta}}_{\mathit{G}}\text{}0.4$ | $0.4\text{}\le {\text{}\mathit{\eta}}_{\mathit{G}}\text{}0.6$ | ${\mathit{\eta}}_{\mathit{G}}\ge \text{}0.6$ |
---|---|---|---|---|---|

${\mathit{x}}_{\mathit{i},\mathbf{6}}$ | 1 | 2 | 3 | 4 | 5 |

LSI | $1.5\text{}\text{}\mathbf{LSI}\text{}\le \text{}2$ | $1\text{}\text{}\mathbf{LSI}\text{}\le \text{}1.5$ | $0.5\text{}\text{}\mathbf{LSI}\text{}\le \text{}1$ | $0\text{}\text{}\mathbf{LSI}\text{}\le \text{}0.5$ | $\mathbf{LSI}=0$ |
---|---|---|---|---|---|

${\mathit{x}}_{\mathit{i},\mathbf{7}}$ | 1 | 2 | 3 | 4 | 5 |

Distance (km) | $\mathit{d}\text{}\text{}4$ | $3\text{}\le \text{}\mathit{d}\text{}\text{}4$ | $2\text{}\le \text{}\mathit{d}\text{}\text{}3$ | $1\text{}\le \text{}\mathit{d}\text{}\text{}2$ | $\mathit{d}\text{}\text{}1$ |
---|---|---|---|---|---|

${\mathit{x}}_{\mathit{i},\mathbf{8}}$ | 1 | 2 | 3 | 4 | 5 |

Load Factor | ${\mathit{f}}_{\mathit{L}}\text{}\le \text{}0.2$ | ${0.2\text{}\text{}\mathit{f}}_{\mathit{L}}\text{}\le \text{}0.4$ | ${0.4\text{}\text{}\mathit{f}}_{\mathit{L}\text{}}\le \text{}0.6$ | $0.6\text{}\le {\text{}\mathit{f}}_{\mathit{L}}\text{}\le \text{}0.8$ | ${0.8\text{}\text{}\mathit{f}}_{\mathit{L}}\text{}\le \text{}1$ |
---|---|---|---|---|---|

${\mathit{x}}_{\mathit{i},\mathbf{9}}$ | 1 | 2 | 3 | 4 | 5 |

Ratio | $1\text{}\le \text{}\frac{\mathit{s}\mathit{L}\mathit{C}\mathit{O}\mathit{E}}{\overline{\mathit{\pi}}}\text{}\text{}\mathbf{\infty}$ | $0.8\text{}\le \text{}\frac{\mathit{s}\mathit{L}\mathit{C}\mathit{O}\mathit{E}}{\overline{\mathit{\pi}}}\text{}\text{}1$ | $0.6\text{}\le \text{}\frac{\mathit{s}\mathit{L}\mathit{C}\mathit{O}\mathit{E}}{\overline{\mathit{\pi}}}\text{}0.8$ | $0.4\text{}\le \frac{\mathit{s}\mathit{L}\mathit{C}\mathit{O}\mathit{E}}{\overline{\mathit{\pi}}}\text{}0.6$ | $0\text{}\le \frac{\mathit{s}\mathit{L}\mathit{C}\mathit{O}\mathit{E}}{\overline{\mathit{\pi}}}\text{}0.4$ |
---|---|---|---|---|---|

${\mathit{x}}_{\mathit{i},\mathbf{10}}$ | 1 | 2 | 3 | 4 | 5 |

Social Acceptance Costs of Direct Use or Electricity Production$\left(\u20ac\xb7{10}^{3}\right)$ | ${\mathbf{sac}}_{\mathit{D}\mathit{U}}>\text{}295$ | ${145<\mathbf{sac}}_{\mathit{D}\mathit{U}}\le 295$ | ${30\text{}\mathbf{sac}}_{\mathit{D}\mathit{U}}\le \text{}145$ | ${4.5\text{}\mathbf{sac}}_{\mathit{D}\mathit{U}}\le \text{}30$ | ${\mathbf{sac}}_{\mathit{D}\mathit{U}}\le \text{}4.5$ |

${\mathit{x}}_{\mathit{i},\mathbf{11},\mathbf{1}}$ | 1 | 2 | 3 | 4 | 5 |

Social Acceptance Costs of Combined Heat – Electricity$\left(\u20ac\xb7{10}^{3}\right)$ | ${\mathbf{sac}}_{\mathbf{CHP}\text{}}\text{}\mathbf{6155}$ | $\mathbf{2640}\text{}$ ${\mathbf{sac}}_{\mathbf{CHP}}\text{}\le \text{}\mathbf{6155}$ | $\mathbf{880}\text{}$ ${\mathbf{sac}}_{\mathbf{CHP}}\text{}\le \text{}\mathbf{2640}$ | $\mathbf{350}\text{}$ ${\mathbf{sac}}_{\mathbf{CHP}}\text{}\le \text{}\mathbf{880}$ | ${\mathbf{sac}}_{\mathbf{CHP}}\text{}\le \text{}\mathbf{350}$ |

${\mathit{x}}_{\mathit{i},\mathbf{11},\mathbf{2}}$ | 1 | 2 | 3 | 4 | 5 |

Employment FT$\left(\frac{dFT}{d{P}_{inst.}}\right)$ | ${\mathbf{e}}_{\mathbf{FT}}\text{}\text{}\mathbf{1}$ | $\mathbf{1}\text{}\le {\text{}\mathbf{e}}_{\mathbf{FT}}\text{}\text{}\mathbf{1.5}$ | $\mathbf{1.5}\text{}\le {\text{}\mathbf{e}}_{\mathbf{FT}}\text{}\text{}\mathbf{2}$ | $\mathbf{2}\text{}\le {\text{}\mathbf{e}}_{\mathbf{FT}}\text{}\text{}\mathbf{4}$ | ${\mathbf{e}}_{\mathbf{FT}}\text{}\ge \text{}\mathbf{4}$ |

${\mathit{x}}_{\mathit{i},\mathbf{11},\mathbf{3}}$ | 1 | 2 | 3 | 4 | 5 |

Employment C&M$\left(person\times year\right)$ | ${\mathbf{e}}_{\mathbf{C}\text{\&}\mathbf{M}\text{}}\le \text{}\mathbf{50}$ | ${\mathbf{50}<\text{}\mathbf{e}}_{\mathbf{C}\text{}\mathbf{M}}\le \text{}\mathbf{150}$ | ${\mathbf{150}<\text{}\mathbf{e}}_{\mathbf{C}\text{}\mathbf{M}}\le \mathbf{250}$ | ${\mathbf{250}<\text{}\mathbf{e}}_{\mathbf{C}\text{}\mathbf{M}}\le \mathbf{350}$ | ${\mathbf{e}}_{\mathbf{C}\text{\&}\mathbf{M}\text{}}\mathbf{350}$ |

${\mathit{x}}_{\mathit{i},\mathbf{11},\mathbf{4}}$ | 1 | 2 | 3 | 4 | 5 |

Total Social Impact | $\mathbf{AV}\text{}\le \text{}\mathbf{1}$ | $\mathbf{1}\text{}\text{}\mathbf{AV}\text{}\le \text{}\mathbf{2}$ | $\mathbf{2}\text{}\text{}\mathbf{AV}\text{}\le \text{}\mathbf{3}$ | $\mathbf{3}\text{}\text{}\mathbf{AV}\text{}\le \text{}\mathbf{4}$ | $\mathbf{4}\text{}\text{}\mathbf{AV}\text{}\le \text{}\mathbf{5}$ |

${\mathit{x}}_{\mathit{i},\mathbf{11}}$ | 1 | 2 | 3 | 4 | 5 |

$\mathbf{Subsidence}\text{}{\mathbf{v}}_{\mathbf{h}}\text{}(\mathit{mm}/\mathit{year})$ | ${\mathbf{v}}_{\mathbf{h}}\text{}\ge \text{}100$ | ${100\text{}\text{}\mathbf{v}}_{\mathbf{h}}\text{}\ge \text{}60$ | ${60\text{}\text{}\mathbf{v}}_{\mathbf{h}\text{}}\ge \text{}40$ | ${40\text{}\text{}\mathbf{v}}_{\mathbf{h}}\text{}\ge \text{}20$ | ${\mathbf{v}}_{\mathbf{h}}\text{}\text{}20$ |

${\mathit{x}}_{\mathit{i},\mathbf{12},\mathbf{1}}$ | 1 | 2 | 3 | 4 | 5 |

Potential SeismicityPGV (cm/s) PGA (cm/s ^{2}) | $\mathbf{0.5}\text{}\le \text{}\mathbf{PGV}\text{}\le \text{}\mathbf{1.6}$ $\mathbf{9}\text{}\le \text{}\mathbf{PGA}\text{}\le \text{}\mathbf{43}$ | $\mathbf{0.2}\text{}\le \text{}\mathbf{PGV}\text{}\le \text{}\mathbf{0.6}$ $\mathbf{4}\text{}\le \text{}\mathbf{PGA}\text{}\le \text{}\mathbf{18}$ | $\mathbf{0.07}\text{}\le \text{}\mathbf{PGV}\text{}\le \text{}\mathbf{0.23}$ $\mathbf{1.5}\text{}\le \text{}\mathbf{PGA}\text{}\le \text{}\mathbf{7.3}$ | $\mathbf{0.03}\text{}\le \text{}\mathbf{PGV}\text{}\le \text{}\mathbf{0.09}$ $\mathbf{0.6}\text{}\le \text{}\mathbf{PGA}\text{}\le \text{}\mathbf{3}$ | $\mathbf{0.01}\text{}\le \text{}\mathbf{PGV}\text{}\le \text{}\mathbf{0.02}$ $\mathbf{0.2}\text{}\le \text{}\mathbf{PGA}\text{}\le \text{}\mathbf{1.2}$ |

${\mathit{x}}_{\mathit{i},\mathbf{12},\mathbf{2}}$ | 1 | 2 | 3 | 4 | 5 |

Land Use(m ^{2}/kW) | $\mathbf{LUI}\text{}\text{}\mathbf{40}$ | $\mathbf{40}\text{}\ge \text{}\mathbf{LUI}\text{}\text{}\mathbf{30}$ | $\mathbf{30}\text{}\ge \text{}\mathbf{LUI}\text{}\text{}\mathbf{20}$ | $\mathbf{20}\text{}\ge \text{}\mathbf{LUI}\text{}\text{}\mathbf{10}$ | $\mathbf{LUI}\text{}\le \text{}\mathbf{10}$ |

${\mathit{x}}_{\mathit{i},\mathbf{12},\mathbf{3}}$ | 1 | 2 | 3 | 4 | 5 |

Noise(dB) | $\mathbf{dB}\text{}\ge \text{}\mathbf{100}$ | $\mathbf{100}\text{}\text{}\mathbf{dB}\text{}\ge \text{}\mathbf{90}$ | $\mathbf{90}\text{}\text{}\mathbf{dB}\text{}\ge \text{}\mathbf{80}$ | $\mathbf{80}\text{}\text{}\mathbf{dB}\text{}\ge \text{}\mathbf{70}$ | $\mathbf{dB}\text{}\text{}\mathbf{70}$ |

${\mathit{x}}_{\mathit{i},\mathbf{12},\mathbf{4}}$ | 1 | 2 | 3 | 4 | 5 |

Potential Water ContaminationTDS (mg/L); (pH) | $\mathbf{TDS}\text{}\ge \text{}\mathbf{1200}\text{};$ $\mathbf{pH}\text{}\le \text{}\mathbf{3}\text{}\mathrm{or}$ $\mathbf{pH}\text{}\text{}\mathbf{8.5}$ | $\mathbf{900}\text{}\le \text{}\mathbf{TDS}\text{}\text{}\mathbf{1200}\text{};$ $\mathbf{3}\text{}\text{}\mathbf{pH}\text{}\text{}\mathbf{4}$ | $\mathbf{600}\text{}\le \text{}\mathbf{TDS}\text{}\text{}\mathbf{900}\text{};$ $\mathbf{4}\text{}\le \text{}\mathbf{pH}\text{}\text{}\mathbf{5}$ | $\mathbf{300}\text{}\le \text{}\mathbf{TDS}\text{}\text{}\mathbf{600}\text{};$ $\mathbf{5}\text{}\le \text{}\mathbf{pH}\text{}\text{}\mathbf{6.5}\text{}\mathrm{or}$ $\mathbf{7.5}\text{}\text{}\mathbf{pH}\text{}\le \text{}\mathbf{8.5}$ | $\mathbf{TDS}\text{}\text{}\mathbf{300}\text{};$ $\mathbf{6.5}\text{}\le \text{}\mathbf{pH}\text{}\le \text{}\mathbf{7.5}$ |

${\mathit{x}}_{\mathit{i},\mathbf{12},\mathbf{5}}$ | 1 | 2 | 3 | 4 | 5 |

Radioactivity(ppm) | $\mathbf{2}\text{}\le {\text{}\mathbf{K}}^{\mathbf{40}}\text{}\mathbf{6}$ $\mathbf{1}\text{}\le \text{}\mathbf{Th}\text{}\le \text{}\mathbf{25}\text{}$ $\mathbf{1}\text{}\le \text{}\mathbf{U}\text{}\le \text{}\mathbf{7}$ | $\mathbf{8}\text{}\le \text{}\mathbf{Th}\text{}\le \text{}\mathbf{18}\text{}$ $\mathbf{1.5}\text{}\le \text{}\mathbf{U}\text{}\le \text{}\mathbf{5.5}$ | $\mathbf{0.2}\text{}\le {\text{}\mathbf{K}}^{\mathbf{40}}\text{}\mathbf{2}$ $\mathbf{0.5}\text{}\le \text{}\mathbf{Th}\text{}\le \text{}\mathbf{10}\text{}$ $\mathbf{0.2}\text{}\le \text{}\mathbf{U}\text{}\le \text{}\mathbf{0.4}$ | $\mathbf{0.7}\text{}\le {\text{}\mathbf{K}}^{\mathbf{40}}\text{}\mathbf{3.8}$ $\mathbf{0.7}\text{}\le \text{}\mathbf{Th}\text{}\le \text{}\mathbf{3.8}$ $\mathbf{0.2}\text{}\le \text{}\mathbf{U}\text{}\le \text{}\mathbf{0.6}$ | $\mathbf{0}\text{}\le {\text{}\mathbf{K}}^{\mathbf{40}}\text{}\mathbf{2}$ $\mathbf{0.1}\text{}\le \text{}\mathbf{Th}\text{}\le \text{}\mathbf{7}$ $\mathbf{0.1}\text{}\le \text{}\mathbf{U}\text{}\le \text{}\mathbf{9}$ |

${\mathit{x}}_{\mathit{i},\mathbf{12},\mathbf{6}}$ | 1 | 2 | 3 | 4 | 5 |

Total Environmental Impact | $\mathbf{AV}\text{}\le \text{}\mathbf{1}$ | $\mathbf{1}\text{}\text{}\mathbf{AV}\text{}\le \text{}\mathbf{2}$ | $\mathbf{2}\text{}\text{}\mathbf{AV}\text{}\le \text{}\mathbf{3}$ | $\mathbf{3}\text{}\text{}\mathbf{AV}\text{}\le \text{}\mathbf{4}$ | $\mathbf{4}\text{}\text{}\mathbf{AV}\text{}\le \text{}5$ |

${\mathit{x}}_{\mathit{i},\mathbf{12}}$ | 1 | 2 | 3 | 4 | 5 |

**Table 13.**Input parameters for the multiple-criteria decision-making (MCDM) matrix for four selected geothermal sites.

Parameter | Unit | Site 1 | Site 2 | Site 3 | Site 4 |
---|---|---|---|---|---|

$\mathrm{Brine}\text{}\mathrm{flow}\text{}\mathrm{rate},q$ | L/s | 83.33 | 20 | 5.5 | 77.1 |

$\mathrm{Inlet}\text{}\mathrm{temperature},\text{}{T}_{H}$ | °C | 170 | 80 | 140 | 80 |

$\mathrm{Outlet}\text{}\mathrm{temperature},\text{}{T}_{C}$ | °C | 70 | 32 | 70 | 40 |

Geothermal gradient | °C/100 m | 6.18 | 6.1 | 3 | 6 |

Number of wells | No. | 1 | 1 | 1 | 1 |

$\mathrm{Specific}\text{}\mathrm{heat}\text{}\mathrm{capacity},\text{}{c}_{p}$ | J/kgK | 4185.5 | 4185.5 | 4185.5 | 4185.5 |

Corrosion and scaling | LSI | 1.5 | 0.5 | 0.5 | 0.5 |

$\mathrm{Fluid}$ | kg/m^{3} | 897.3 | 971.76 | 925.9 | 971.76 |

$\mathrm{Th}.\text{}\mathrm{efficiency},\text{}{\eta}_{max,ele}$ | % | 6.18 | 6.1 | 3 | 6 |

$\mathrm{Max}.\text{}\mathrm{efficiency},\text{}{\eta}_{max,heat}$ | % | 76.47 | 62.5 | 78.57 | 53.33 |

^{1}Density of the geothermal water changes with the temperature according to Reference [40].

Parameter | Unit | Value |
---|---|---|

Specific costs | €/MW | 4,500,000; 6,750,000 ^{1}; 9,000,000 |

OPEX | €/MWh | 10; 20 ^{1}; 30 |

$\mathrm{Discount}$ | % | 6; 7 ^{1}; 8.7 |

$\mathrm{Lifetime}$ | years | 20; 30 ^{1}; 40 |

$\mathrm{Energy}\text{}\mathrm{produced},\text{}{E}_{t}$ | MWh (annual) | Calculated ^{2} |

^{1}Base case values are used in the base case scenario, left values represent decreased and right values increased values compared to the base case scenario that is used in the sensitivity analysis;

^{2}The annual produced electricity or heat is calculated as a product of Equation (2) and (3) or Equation (4).

Criterion | Site 1 | Site 2 | Site 3 | Site 4 |
---|---|---|---|---|

${x}_{i,1}$ | 4 | 1 | 1 | 1 |

${x}_{i,2}$ | 1 | 2 | 4 | 1 |

${x}_{i,3}$ | 3 | 1 | 2 | 1 |

${x}_{i,4}$ | 5 | 5 | 3 | 5 |

${x}_{i,5}$ | 5 | 2 | 4 | 2 |

${x}_{i,6}$ | 1 | 1 | 1 | 1 |

${x}_{i,7}$ | 1 | 4 | 4 | 4 |

${x}_{i,8}$ | 4 | 5 | 4 | 5 |

${x}_{i,9}$ | 5 | 5 | 5 | 5 |

${x}_{i,10}$ | 3 | 3 | 3 | 3 |

${x}_{i,11}$ | 5 | 5 | 5 | 5 |

${x}_{i,12}$ | 5 | 5 | 5 | 5 |

Final | 3.5 | 2.83 | 3 | 2.75 |

Criterion | Site 1 | Site 2 | Site 3 | Site 4 |
---|---|---|---|---|

${x}_{i,1}$ | 4 | 5 | 4 | 4 |

${x}_{i,2}$ | 1 | 2 | 3 | 1 |

${x}_{i,3}$ | 5 | 5 | 5 | 5 |

${x}_{i,4}$ | 5 | 5 | 3 | 5 |

${x}_{i,5}$ | 5 | 2 | 4 | 2 |

${x}_{i,6}$ | 4 | 4 | 4 | 4 |

${x}_{i,7}$ | 1 | 4 | 4 | 4 |

${x}_{i,8}$ | 3 | 4 | 3 | 4 |

${x}_{i,9}$ | 2 | 2 | 2 | 2 |

${x}_{i,10}$ | 1 | 1 | 1 | 1 |

${x}_{i,11}$ | 4 | 5 | 4 | 5 |

${x}_{i,12}$ | 5 | 5 | 5 | 5 |

Final | 3.33 | 3.67 | 3.5 | 3.5 |

Input Parameter | Unit | Decrease | Base | Increase |
---|---|---|---|---|

CAPEX | €/MW | 4,500,000 | 6,750,000 | 9,000,000 |

Discount rate | % | 6 | 7 | 8 |

OPEX | €/MWh | 20 | 30 | 40 |

Lifetime | years | 20 | 30 | 40 |

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Raos, S.; Ilak, P.; Rajšl, I.; Bilić, T.; Trullenque, G. Multiple-Criteria Decision-Making for Assessing the Enhanced Geothermal Systems. *Energies* **2019**, *12*, 1597.
https://doi.org/10.3390/en12091597

**AMA Style**

Raos S, Ilak P, Rajšl I, Bilić T, Trullenque G. Multiple-Criteria Decision-Making for Assessing the Enhanced Geothermal Systems. *Energies*. 2019; 12(9):1597.
https://doi.org/10.3390/en12091597

**Chicago/Turabian Style**

Raos, Sara, Perica Ilak, Ivan Rajšl, Tena Bilić, and Ghislain Trullenque. 2019. "Multiple-Criteria Decision-Making for Assessing the Enhanced Geothermal Systems" *Energies* 12, no. 9: 1597.
https://doi.org/10.3390/en12091597