geothermal power plant projects in central america - Orkustofnun

More documents

Recommendations

Info

eaches the maximum limit, and for higher values of a temperature resource, the optimum pressure forthe HP separator remains constant.4.3.3 Organic Rankine cycleIn the optimization process of theORC, the boiler pressure is chosenas the variable to maximize thespecific net power output; comparedto flashing technologies, in the ORCoptimization there is no constraintrelated to the vapor quality at theturbine exhaust due tocharacteristics of the organicworking fluid. Wet fluids like waterusually need to be superheated,while many organic fluids, whichmay be dry or isentropic, do notneed superheating (Andersen andBruno, 2005). In addition, a recentstudy by Chen et al. (2010)concluded that superheating has anegative effect on cycle efficiencywhen dry fluids are used in ORC;therefore, superheating is notrecommended.Specific Net Power Output [kW]Specific net power output [ kW/kg/s ]30025020015010050300250200Specific net power output HP Separator LP Separator00160 180 200 220 240 260 280 300 320 340Resource temperature [°C]Specific net power outputAs shown in Table 5, four1500.85isentropic fluids (isobutane, n-butane, isopentane and n-pentane)are considered as candidates in thisstudy. It is quite clear that the100500.800.7500.70selection of the working fluid plays160 180 200 220 240 260 280 300 320 340a key role in ORC performance,Resource temperature [ °C ]where the critical temperature offluid is a factor. For each workingfluid, the optimum specific powerFIGURE 6: Specific net power output and steam qualityof turbine output from DF cycleoutput is plotted against theresource temperature as illustrated in Figure 23.TABLE 5: Organic working fluids properties (Dipippo, 2008)LP Steam quality at turbine outputWorking fluid Critical Temperature (°C) Critical Pressure (kPa)isobutane 135.92 3,685n-butane 150.98 3,718isopentane 187.8 3,409n-pentane 193.9 3,204The optimum value of the specific net power output (Figure 23) and the corresponding boiler pressure(Figure 24) are proportional to a resource temperature of 100 to 180°C for ORC operating with n-butane, isopentane or n-pentane, and from 100 to 160°C for ORC operating with isobutane.An ORC cycle run with isobutene for resource temperatures below 160°C gives a slightly higherpower output compared with the rest of the working fluids. For temperatures above 160°C, themaximum working pressure for isobutane with 3200 kPa is reached at 86% of the critical pressure.4000350030002500200015001000FIGURE 5: Specific net power output and separator pressurefrom DF cycle5001.000.950.90Separator pressure [kPa]Steam quality [ - ]25
Specific net power output [ kW/kg/s ]Specific net power output (isopentane)Specific net power output (n-butane)706050403020100100 120 140 160 180Resource temperature [ °C ]Specific net power output (n-pentane)Specific net power output (isobutane)FIGURE 7: Specific net power output from ORCusing different working fluidsThe resulting shift of the pinchpoint, from the inlet of the boiler tothe inlet of the preheater (Figure25), leads to higher efficiencycompared to the other workingfluids. Heberle et al. (2011) made itclear that this effect takes placebecause the maximum processingpressure of the ORC fluid isreached, which leads to a highquantity of thermal energy coupledto the cycle. As a result, operatingORC with isobutane cools thegeothermal resource mosteffectively; however, there is areduction in the temperature of thereinjection temperature, close to theworking fluid input temperature(Figure 25).In this study, the selection of the working fluid is based on the optimum specific power output; thereinjection temperature is not a restriction. Based on these considerations, isobutane is the mostsuitable working fluid for the ORC cycle at the resource temperature for the majority of thetemperatures in the range evaluated. Supplementary calculations show that for an increasing resourcetemperature of more than 180°C, n-butane, isopentane and n-pentane also have a tendency to reachmaximum work pressure limits.4.3.3 Comparison of power output between SF, DF and ORCFigure 26 presents a comparison of the optimal power outputs of the three power technologiesoperating at different geothermal resource temperatures. It can be seen that the size of power plants isdetermined principally byBoiler pressure (isopentane) Boiler pressure (n-pentane) geothermal resource characteristics,Boiler pressure (n-butane) Boiler pressure (Isobutane) but these are not the only factorsthat affect it.Boiler Pressure [ kPa ]40003500300025002000150010005000100 120 140 160 180Resource temperature [ °C ]FIGURE 8: Boiler pressure from ORC usingdifferent working fluidsIn this study, flashing technologiesare evaluated for resourcetemperatures between 160 and340°C. As shown in Figure 23, thespecific power output of a DFpower plant is higher with respect tothe SF power plant. DF is moreeffective than SF because a largerportion of the resource is utilizedfor electricity generation. It isimportant to note that in SF and DFcycles at lower temperatures thesteam fraction becomes smaller andonly a small fraction of the energyin the geothermal fluid can beutilized for electricity generation. However, also under consideration at temperatures between 100and 180°C is an ORC operated with a secondary working fluid (isobutane) which has a low boilingpoint and high vapor pressure at low temperatures in contrast to steam. When comparing theseprocesses with regard to the net power output at lower temperatures between 160 and 180°C, theregenerated ORC results in a higher power output than the SF and DF systems.26
Page 1 and 2: GEOTHERMAL TRAINING PROGRAMMEHot sp
Page 3 and 4: This MSc thesis has also been publi
Page 5 and 6: ACKNOWLEDGEMENTSMy gratitude to the
Page 7 and 8: TABLE OF CONTENTSPage1. INTRODUCTIO
Page 9 and 10: PageAPPENDIX A: FINANCIAL MODEL ...
Page 12 and 13: 1. INTRODUCTIONRecent research on r
Page 14 and 15: 2. CENTRAL AMERICAN DATA2.1 Power p
Page 16 and 17: 2.2.3 HondurasThe Honduran electric
Page 18 and 19: NET INJECTION BY SOURCE (2010)INSTA
Page 20 and 21: income taxes for a period of 10 yea
Page 22 and 23: annual temperature ranges from 17 t
Page 24 and 25: egional reconnaissance in 1981ident
Page 26 and 27: 4. GEOTHERMAL ELECTRICAL POWER ASSE
Page 28 and 29: The net contribution of that power
Page 30 and 31: Introducing , = , and , = ,
Page 32 and 33: 9ProductionWellBoiler5Turbine~1046P
Page 34 and 35: TABLE 3: Parameters and boundary co
Page 38 and 39: 160180140160tc vap[i], th vap[i]120
Page 40 and 41: average results, and combining them
Page 42 and 43: The base cost ( ) can be calculate
Page 44 and 45: calculation for another separator c
Page 46 and 47: mass flow rate (kg/s) on the plant
Page 48 and 49: Table 11 shows a summary of costs f
Page 50 and 51: 5.6.4 Comparison of capital costs b
Page 52 and 53: 6. FINANCIAL FEASIBILITY ASSESSMENT
Page 54 and 55: 6.2 Model structureThe financial fe
Page 56 and 57: CCF = EBITDA − ∆Working Capital
Page 58 and 59: Interest on loansFleischmann (2007)
Page 60 and 61: IRR30%25%IRR CapitalIRR Equity20%Si
Page 62 and 63: FIGURE 42: Allocation of funds for:
Page 64 and 65: 340IRR Free Cash Flow to Equity [ %
Page 66 and 67: flash technology is between 0.3 and
Page 68 and 69: Energy Price Availability Factor O&
Page 70 and 71: FIGURE 50: Density and cumulative p
Page 72 and 73: In Chapter 6, Figure 44 illustrated
Page 74 and 75: The internal rate of return is offs
Page 76 and 77: Cengel, Y. and Tuner, R., 2005: Fun
Page 78 and 79: IEAb, 2011: Technology roadmap: Geo
Page 80 and 81: Salmon, J., Meurice, J., Wobus, N.,
Page 82 and 83: APPENDIX A: SUMMARY OF FINANCIAL MO
Page 84 and 85: APPENDIX C: INVESTMENT AND FINANCIN
Page 86 and 87:
APPENDIX E: BALANCE SHEETBALANCE SH
show all

geothermal power plant projects in central america - Orkustofnun

Create successful ePaper yourself

Delete template?

Save as template?