https://orcid.org/0000-0002-9668-6654
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ABSTRACT
The exergoeconomic analysis of an energy conversion system is helpful to decide about topics like the cost of fuel required to produce each unit of energy, electricity sales prices affecting energy production cost amounts and how to allocate R&D funds to develop system equipment. With this aim, exergoeconomic assessment of a binary geothermal power plant (GPP) with organic Rankine cycle (ORC) is researched in detail. Therefore, a parametric study about the effect of well head and ambient temperatures, electricity production, and CO2 release is conducted for the GPP. The study shows that the exergy efficiency, exergy destruction ratio and exergoeconomic factor for the GPP are, respectively, 39.1%, 31.4%, and 58.1%. The highest total operating costs and exergy destruction rate belong to the condenser in the system with values of 186 $/h and 2.49 MW. The costs per unit exergy for the liquid and steam geothermal fluid in the GPP are 1.2 $/GJ and 370 $/GJ, respectively. The total operating cost of the GPP is nearly 1,218.38 $/h, while the cost rate per unit of electricity produced by the GPP is 0.055 $/kWh. As the ambient temperature increased, there is a 10% increase in total operating cost and this results in a 21% increase in cost per electricity produced. With the brine input temperatures of 160°C, 165°C, and 170°C, the costs per unit CO2 output are, respectively, 110 $/h, 167.50 $/h, and 307 $/h. In conclusion, as the amount of steam brine entering the GPP increases, the amount of CO2 released to the atmosphere ascends.
Acknowledgments
The authors would like to thank for the support provided by the Maren Geothermal Inc., Turkey.
Declarations of interest
The authors declared that there is no conflict of interest.
Nomenclature
| c | = | cost per exergy unit ($/GJ) |
| Ċ | = | unit cost rate ($/h) |
| CGE | = | cost of generating electricity ($/kWh) |
| CRF | = | capital recovery factor (-) |
| = | annual levelized cost ($/yr) | |
| = | exergy destruction rate (W) | |
| Ėx | = | exergy rate (J/s or W) |
| f | = | exergoeconomic factor (%) |
| h | = | specific enthalpy (J/kg) |
| i | = | interest (%) |
| M | = | annually saved petroleum/CO2 (L/year) |
| ṁ | = | mass flow rate (kg/s) |
| n | = | lifetime (year) |
| OM | = | operating-maintenance cost ($/year) |
| P | = | pressure (kPa) |
| PEC | = | purchased equipment cost ($) |
| = | present worth ($) | |
| PWF | = | present worth factor |
| = | heat rate or heat (J/s or W) | |
| r | = | relative cost difference (%) |
| s | = | specific entropy (J/kgK) |
| SV | = | salvage cost ($) |
| T | = | temperature (°C or K) |
| Ẇ | = | work rate or power (J/s or W) |
| y | = | exergy destruction ratio (%) |
| Ż | = | annually levelized cost value ($/h) |
| = | Greek symbols | |
| = | exergy/exergetic or second law efficiency (%) | |
| τ | = | annual operating hour (h/year) |
| ψ | = | specific flow exergy (J/kg) |
| = | Subscripts | |
| D | = | destruction |
| F | = | fuel |
| i,j | = | state |
| in | = | inlet |
| k | = | component |
| L | = | loss |
| LB | = | liquid brine |
| out | = | outlet |
| P | = | product |
| Q | = | heat |
| SB | = | stream brine |
| tot | = | total/overall |
| W | = | work |
| 0 | = | reference state |
| = | Superscripts | |
| CI | = | capital investment |
| n | = | lifetime |
| OM | = | operating-maintenance |
| = | Abbreviations | |
| CON | = | condenser |
| GEN | = | generator |
| GPP | = | geothermal power plant |
| NCG | = | noncondensing gas |
| ORC | = | organic Rankine cycle |
| PRE-HE | = | preheater |
| PU | = | pump |
| RECUP | = | recuperator |
| SPECO | = | specific exergy costing |
| TURB | = | turbine |
| VAP | = | vaporizer |