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Science – Society – Technology

Table 3 Parametrization for Case 1 (conventional geothermal system) and Case 2 (enhanced geothermal system)

From: Sustainable operation of geothermal power plants: why economics matters

Parameter Symbol Case 1 Case 2 Unit Source/section
Thermal capacity of reservoir rock \({c}_{\text{r}}\) 800 1000 (J kg−1 K−1) Proske (undated: 7)
Stober and Bucher (2014: 10)
Density of reservoir rock \({\rho }_{\text{r}}\) 2600 2700 (kg m−3) Proske (undated: 7)
Specific thermal capacity of fluid \({c}_{\text{f}}\) 4120 4120 (J kg−1 K−1)
Density of heat carrying fluid \({\rho }_{\text{f}}\) 1000 1000 (kg m−3)
Porosity \(\Phi\) 20 1 (%) Björnsson and Bodvarsson (1990: 19)
Moeck (2014: 878)
Reservoir volume \(V\) 4.5  109 3  109 (m3)
Bine.info (2009)
Reservoir temperature TR 270 180 (°C) Björnsson and Bodvarsson (1990: 19)
Gerard and Kappelmeyer (1987: 399)
Surface temperature TS 14 14 (°C) Walter (2016: 7)
Measured drilling depth MD 1500 4000 (m) Bignall et al. (2010: 6)
Moeck (2014: 875)
Recovery factor R 20 5 (%) cf. “Recovery factor
Temperature of produced fluid \({T}_{\text{prod}}\) 260 175 (°C) Björnsson and Bodvarsson (1990: 19) bine.info (2009)
Temperature of reinjected fluid \({T}_{\text{rein j}}\) 65 65 (°C) cf. “Reinjection
Bine.info (2009)
Heat from radioactive decay \({H}_{\text{R}}\) 2.7  10–6 3  10–6 (W m−3) Hasterok and Webb (2017: 925)
Rybach (1976)
Heat flow from earth’s interior \({H}_{\text{F}}\) 13.3 0.105c (W m−2) O'Sullivan et al. (2010: 315)
Reservoir surface area \(A\) 3∙107 3  106 (m2) O'Sullivan et al. (2010: 315)
Bine.info (2009)
Net conversion efficiency \(\eta\) 14 8 (%) cf. “Conversion efficiency
Average productivity per well \(\bar{w}\) 5 1.5 (MWe) cf. “Well productivity
Electricity price/feed-in tariff \(p\) 50 240d (€ MWh−1) EEX (2019)
BDEW (2017: 36)
Discount rate \(i\) 5 5 (%)
Reference initial production decline rate \({D}_{\text{i}}\) 5 5 (%) cf. “Production decline
Reference initial capacitya \({W}_{\text{i}}\) 100 25 (MWe) cf. “Production decline
Well reserve factor \(r\) 10 0 (%) cf. “Production decline
Tax rate \(\text{tax}\) 20b e (%)
Surrounding thermal compensation \(\beta\) 1 6 (%) cf. “Recovery factor
Plant type   Flash Binary   O'Sullivan et al. (2010: 315)
Bine.info (2009)
Capacity factor cap 0.95 0.95 (%) cf. “Capacity factor
Start for make-up well drilling   1 1 (a) cf. “Costs (Number of wells required)”
  1. aDue to the strong convective setting, reference production decline capacity was set to 100 MWe
  2. bWe chose a very moderate tax rate, as the model currently does not take into account realization of tax savings
  3. cValue of the heat flow from Cooper Basin, an HDR project in South Australia (O'Sullivan et al. 2010: 315)
  4. dCase 2 is calculated with the current German feed-in tariff for geothermal electricity as normal electricity prices were not sufficient for profitable operation
  5. eTaxes have been neglected for Case 2