Techno-Economic Analysis of Organic Rankine Cycles for a Boiler Station Energy System Modeling and Simulation Optimization
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UPTEC ES 19036 Examensarbete 30 hp December 2019 Techno-Economic Analysis of Organic Rankine Cycles for a Boiler Station Energy system modeling and simulation optimization Jamel Hudson Abstract Techno-Economic Analysis of Organic Rankine Cycles for a Boiler Station Jamel Hudson Teknisk- naturvetenskaplig fakultet UTH-enheten The Organic Rankine Cycle (ORC) may be the superior cycle for power generation using low temperature and low power heat sources due to Besöksadress: the utilization of high molecular mass fluids with low boiling Ångströmlaboratoriet Lägerhyddsvägen 1 points. They are flexible, simple, easy to operate and maintain, and Hus 4, Plan 0 offer many possible areas of application including waste heat recovery, biomass power, geothermal power and solar power. Therefore, Postadress: they may prove to be of significant importance in the reduction of Box 536 751 21 Uppsala global greenhouse gas emissions and the mitigation of climate change. Telefon: In this thesis, the technical feasibility and economic profitability 018 – 471 30 03 of implementing an ORC in a district heating boiler station is Telefax: investigated. A model of the ORC connected to the hot water circuit 018 – 471 30 00 of a biomass boiler is simulated. The achieved evaporation temperature is estimated to 135°C and the condensation temperature is Hemsida: found to vary in the range of 70-100°C. The results show that it is http://www.teknat.uu.se/student both possible and profitable to implement an ORC in the studied boiler station. A maximum net present value of 2.3 MSEK is achieved for a 400 kW system and a maximum internal rate of return of 8.5%, equivalent to a payback period of 9.5 years, is achieved for a 300 kW system. Furthermore, the investment is found to be most sensitive to changes in electricity price, net electric efficiency and capital expenditure cost. Handledare: Marcus Guldstrand Ämnesgranskare: Ali Al-Adili Examinator: Petra Jönsson ISSN: 1650-8300, UPTEC ES 19036 Acknowledgements The idea of the thesis originated from my passion for sustainable energy technology and from Claes Nyl´en,manager at WSP, who was able to find a suitable project in cooperation with Alings˚as Energi. I would therefore like to thank Claes Nyl´en,for his help to initiate the thesis, in addition to the management of Alings˚asEnergi, in particular manager Einar Str¨om. Thank you. I also thank my supervisor Marcus Guldstrand for his support, expertise, and tough questions, which helped the analysis progress in the right direction. Without Marcus the technical level of the thesis would not be what it is. Thank you. Furthermore, I give thanks to my subject reviewer Ali Al-Adili who has thoroughly reviewed the report and provided constructive feedback. Without Ali the standard of the report would not be what it is. Thank you. Bj¨ornSamuelsson of Svenska Rotor Maskiner AB and Elin Ledskog of Againity AB have both been helpful in providing me with insights and details regarding the workings of commercial ORC systems. The talks and study visits have been helpful, interesting, and enjoyable. Therefore, I give thanks to both Bj¨ornand Elin. Thank you. i Popul¨arvetenskaplig sammanfattning Klimatf¨or¨andringartill f¨oljdav m¨anniskans anv¨andningav fossila br¨anslen ¨arallvarliga och n˚agotvi b¨orf¨ors¨oka undvika. F¨oratt lyckas med det beh¨over vi minska v˚aranv¨andningav fossila br¨anslen, fr¨amstolja, kol och naturgas som i dagsl¨agetanv¨andsf¨oratt producera elektricitet. Elektriciteten produceras genom att br¨ansletsf¨orbr¨annsmed syfte att koka och f¨or˚angavatten under ett h¨ogt tryck, varefter vatten˚angantrycks genom en turbin vilket ger upphov till en rotationsr¨orelse.Tur- binens rotationenergi omvandlas sedan till en elektrisk effekt med hj¨alpav en generator. Majoriteten av v¨arldenselektricitet produceras p˚aett s˚adant s¨att,och det leder till stora v¨axthusgasutsl¨app. F¨oratt minska utsl¨appen av v¨atxhusgaser beh¨over vi d¨armedbyta ut fossilbaserad elproduktion- skapacitet mot f¨ornybar s˚adan.Men hur ska vi g¨oradet? Fritt fl¨odande energi, i form av fr¨amst sol- och vindenergi, p˚ast˚asav m˚angavara l¨osningp˚amorgondagens energif¨ors¨orjning| men vad g¨orvi n¨arvarken solen skiner eller vinden bl˚aser?Man kan t¨anka sig att anv¨andandet av batterier ¨arl¨osningen,men en storskalig reglering av v¨arldenseln¨atenbart med battrier ¨arvarken h˚allbar eller tekniskt m¨ojligmed dagens batteriteknologi. Allra helst skulle vi vilja ha en f¨ornybar baskraft, som kan producera elektricitet kontinuerligt, dygnet runt. Organiska rankinecykler ¨arv¨armemaskiner baserade p˚aorganiska fluider med l¨agrekokpunkt ¨an vatten. De till˚aterelproduktion med v¨armek¨allorav l˚agtemperatur (l¨agre¨an400 °C) samt ¨aven av l˚ageffekt (l¨agre¨an10 MW), f¨orvilka vanliga ˚angkraftverk ¨arotillr¨ackliga. Det ¨arav stor betydelse eftersom mycket av den tillg¨anligav¨armeeffekten,s˚asom spillv¨armei industrier och geotermisk v¨arme,ofta karakt¨ariseras av att vara av l˚agtemperatur och men ¨aven av l˚ageffekt. Av den anled- ningen kan organiska Rankinecykeler spela en viss roll i begr¨ansningenav klimatf¨or¨andringarna. I det h¨ararbetet studeras b˚adeden tekniska genomf¨orbarhetenoch ekonomiska l¨onsamhetenav att implementera en organisk rankinecykel i ett fj¨arrv¨armeverk i s¨odraSverige. F¨ordelenmed att till¨ampaorganiska rankinecykler i just fj¨arrv¨armeverk ¨aratt det medf¨oren h¨ogenergiverkningsgrad, till f¨ojd av att den v¨armeenergisom inte omvandlas till elektricitet kan tas omhand om och anv¨andas i fj¨arrv¨armen¨atet.F¨oratt bed¨omaden organiska rankinecykelns p˚averkan p˚afj¨arrv¨armeverket, och l¨onsamheten,skapas en modell av fj¨arrv¨armeverket med v¨armemaskinenintegrerad i systemet. ii Modellen simuleras med befintlig produktionsdata och l¨onsamhetenbest¨ams. Resultatet visar p˚a att det ¨arfullt m¨ojligtoch l¨onsamt att implementera organiska Rankinecykler i fj¨arrv¨armeverk. Dock s˚avisar det sig att l¨onsamheten ¨arstarkt kopplad till systemets nominella effekt, elpriset och kapitalkostnaderna. Dessutom s˚ap˚avisasatt l¨onsamheten ¨arstarkt kopplad till fj¨arrv¨armever- kets returtemperatur, och att h¨ogrel¨onsamhet d¨armed kan n˚asgivet att returtemperaturen s¨anks. Studiens resultat kan anv¨andassom underlag f¨orbeslutsfattare som funderar p˚aatt implementera organiska rankinecykler i deras fj¨arrv¨armeverk. Studien ¨ar¨aven av nytta f¨orandra till¨ampning- somr˚aden¨anjust fj¨arrv¨armeverk eftersom en generell metod f¨oratt modellera organiska rankinecyk- ler utvecklas och beskrivs. iii Executive Summary Introduction ORCs may contribute to renewable electricity generation and thus play a role in the mitigation of climate change. The technical feasibility and economic profitability of implementing an ORC at S¨avelundsverket is therefore studied, with the aim of finding the optimal power rating and plant operation. The effects of a) lowering the DHS supply and return temperatures and b) connecting an ORC to the hot water circuits of all three boilers is also investigated. Method The chosen ORC system integration into the plant is illustrated in figure 4.15. Figure 1: Model of the boiler station with an ORC integrated. The boiler plant with the ORC model, connected after the flue gas condenser belonging to the boiler of line C, is modeled and simulated. This is chosen as the best location due to the high temperature of the hot water circuit belonging to boiler C, and it is placed after the flue gas condenser such that the power output of the flue gas condenser is unaffected. The electric power output of the ORC depends on the pressure difference over the expander, which is determined by the temperature difference of the heat source and the cooling flow. More precisely, the condenser iv pressure is determined by the exit temperature of the cooling flow through the condenser; a low temperature cooling flow results in a low condenser pressure which is desirable. However, the exit temperature of the cooling flow depends on the thermal power output and the net electric efficiency of the ORC. Therefore an iterative approach is used in order to model and simulate the system. The ORC is modeled with the parameters listed in table1, and the profitability is determined using the parameters listed in table2. Table 1 List of parameters of the ORC model Parameter Value Fluid R1233ZD(E) [C3ClF3H2] Expander isentropic efficiency 80% Pump isentropic efficiency 80% Generator electric efficiency 95% Condenser HX TTD 10 °C Evaporator HX TTD 10 °C Evaporation temperature 135 °C Energy losses Neglected Piping pressure losses Neglected Maximum allowable thermal power input 10 · PRAT ED Part load performance Accounted for by correction factor Table 2 List of economic parameters Parameter Value Discount rate 5% [60] Economic lifetime 20 years [4][53][55] Electricity price 0.45 SEK⁄MWh Electricity certificate price 0.05 SEK⁄MWh [61] Electricity distribution cost 0.05 SEK=kW h [60] Power charge fee 172 SEK⁄kW [60] High load power charge fee 256 SEK⁄kW [60] Fuel price 0.200 SEK⁄MWh [60] ORC unit cost 10-30 kSEK⁄kW [4][53][55] Installation cost 20% of ORC unit cost Operation and maintenance cost 2% of ORC unit cost [4][53][55] v Results Simulating the model, a maximum net present value (NPV) of 2.3 MSEK for a 400 kW machine and internal rate of return (IRR) of 8.5% for a 300 kW machine is found. A sensitivity analysis show that the profitability of the investment is very sensitive to changes in electricity price, net electric efficiency and capital expenditure cost. Figure 2: Net present value as a function of power rating and electricity price. vi Key insights I Integrating an ORC into the HWC of a boiler in a heat-only boiler station is both possible and profitable.