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Geothermal Studies of Low Temperature & Binary systems 3-90 - 5-93
from Cb Segal Urxlaz Baw MEG See fn oaasJey,-@ MancetinaFAYZB+32g-BSOw 7 -[Gn Miko ts/S-BM Fay 30 3-120-4L4G ALASKA-ICELAND ENTERPRISES 705 West 6th Avenue,Suite 209 Anchorage,Alaska 99501 Phone:(907)272-6773 Fax:(907)274-1303 FAX Total Pages:-/- May 25,1993 To:Mr.David Eberle,Alaska Energy AuthorityFrom:Mr.William Noll Thank you for your call regarding generators.Here is the name of our colleague In tceland. Mr.Ingvar Nielsson Icelaska IS-107 Reykjavik Tomasarhagi 29 Iceland Phone:(354-1)622524 Fax:(354-1)621592 Mr.Nielsson Is very experienced with the subject of geo-thermal energy. He himself has served in goverment posts dealing with geo-thermal in Iceland. Alaska-Iceland Enterprises has established a relationship with Mr.Nielsson.He himseif is well-versed in the areas we have been discussing with you,and he also is well connected throughout Iceland with other experts. _With regard to the organic rankin cycle generators you asked about,please fee! free to your inquiry directly to Mr.Nielsson (copy us,please)or through our firm.Thank you again for your call.We look forward to hearing from you. Best regards, Alaska-iceland Enterprises iiam C.Noll Managing Partner cc:Mr.Ingvar Nielsson 05/21/91 NATIONAL GEOTHERMAL ASSOCIATION Page .LIST OF ATTENDEES . May 6-7,1991 "POWER GENERATION FROM LOW TEMPERATURE GEOTHERMAL RESOURCES" David Anderson Geothermal Resources Council PO Box 1350 Davis CA 95617 Phone:916/758-2360 Fax:916/758-2839 Ronald C Barr Earth Power Energy & Minerals Inc. 1795 Granite Drive Reno NV 89509 Phone:702/829-2030 Carl Bliem Idaho National Engineering Lab PO Box 1625 Mail Stop 3526 Idaho Falls ID 83415 Phone:208/526-9895 Fax:208/526-0969 Shaun Brady Pacific Gas &Electric Co -Geysers Power Plant PO Box 1310 Healdsburg CA 95461 Phone:707/431-6070 Dave Brown Power Systems Corporation Bulding One,Suite 255 4000 Kruse Way Place Lake Oswego OR 97035 Phone:503/697-1736 Jeff Canon Power Systems Corporation Geothermal Services P.O.Box 838 Holtville CA 92250 Phone:619/356-5501 Ralph M Aviles UNOCAL Geothermal Division 1912 Eversley Place Santa Rosa CA 95401 Phone:707/545-7600 Fax:707/545-8746 Kelly J.Birkinshaw California Energy Commission 2144 Castro Way Sacramento CA 935818 Phone:916/324-3466 Gordon Bloomquist Washington State Energy Office 6206 Tiger Tail Drive Southwest Olympia WA 98502 Phone:206/956-2016 Fax:206/753-2397 John G.Broadus UNOCAL Corp. 800 W.Ist Street Los Angeles CA 90012 Phone:213/977-7100 Richard Campbell The Ben Holt Company 201 South Lake Avenue Suite 308 Pasadena CA 91101 8 Phone:213/684-2541 Fax:818/584-9210 Stephen Christensen Provo City Power PO Box 1058 Beaver UT 84713 Phone:801/379-6840 05/21/91 NATIONAL GEOTHERMAL ASSOCIATION Page 3 « : LIST OF ATTENDEES May 6-7,1991 "POWER GENERATION FROM LOW TEMPERATURE GEOTHERMAL RESOURCES" Larry Jones Northern Calif Power Agency 1514 Lupine Road Healdsburg CA 95448 Phone:707/433-4918 Alex I.Kalina Exergy,Inc. 22320 Foothill Blvd Suite 540 Hayward CA 94541 Phone:415/537-5881 G.E.Kluppel Hudson Products Corp 6855 Harwin Drive Houston TX 77236 Phone:713/972-8108 Quirino S.Kolimlim Unocal Geothermal Division 3733 Mocha Lane Santa Rosa CA 95403 Phone:707/579-1734 Fax:707/545-8746 Raymond J LaSala U.S.Department of Energy Geothermal Division,CE-122 1000 Independence Avenue,SW Washington DC 20585 Phone:202/586-4198 Fax:202/896-4198 Cecilia Liang-Nichol Sierra Pacific Power Company P.O.Box 10100 Reno NV 89520 Phone:702/689-3966 Douglas Jung Two Phase Engineering &Resch 3209 Franzvalley Road Santa Rosa CA 95404 Phone:707/523-4585 Richard G.Klaren Scheffers of America Inc. 2203 Limberlock Place Suite 234 The Woodlands TX 77380 Phone:713/363-3121 Lauri Knox 4110 Goebell Avenue Palo Alto CA 94306 Phone:415/494-7422 Fax:415/494-3539 Paul Kruger Stanford University Civil Engineering Department Stanford CA 94305 Phone:415/497-4123 William Laughlin Los Alamos National Laboratory ESS-1 MS D-462 Los Alamos NM 87545 Phone:505/667-6711 ws Grant S Lyddon COSO Exploration Company Inc 947 Berkeley Street Santa Monica CA 90403 Phone:213/828-6970 Fax:213/829-0040 05/21791 NATIONAL GEOTHERMAL ASSOCIATION Page -LIST OF ATTENDEES May 6-7,1991 "POWER GENERATION FROM LOW TEMPERATURE GEOTHERMAL RESOURCES" Dennis Markus Exergy Incorporated 22320 Foothill Blvd Suite 540 Hayward CA 94541 Phone:415/537-5881 Fax:415/537-8621 David Mendive Geothermal Development Assoc 251 Ralston Street Reno NV 89503 Phone:702/322-0938 Kenneth E Nichols Barber-Nichols Inc 6325 West 55th Avenue Arvada CO 80002 Phone:303/421-8111 Fax:303/420-4679 Robert Reichhelm Hudson Products Corp 16861 Encino Hills Drive Encino CA 91436 . Phone:818/981-7046 Fax:818/981-7217 Joel L.Renner Idaho National Engineering Lab PO Box 1625 MS 3526 Idaho Falls ID 83415 Phone:208/526-9824 Fax:208/526-0969 Gary Shulman Geothermal Power Company Inc 1460 West Water Street Elmira NY 14905 Phone:607/733-1027 Fax:607/734-2709 ee re ee ce ee ae ae em es ee ee ee ee ee ee ee ee i ew we a wow oe Graciela Mata Geothermal Resources Council PO Box 1350 Davis CA 95617 Phone:916/758-2360 Fax:916/758-2839 George Morse Provo City Power PO Box 1058 Beaver UT 84713 Phone:801/379-6840 Raymond F Ponden Los Alamos National Laboratory P.O.Box 1663 Los Alamos NM 87545 Phone:505/667-4318 Zvi Reiss OESI Power Corp. 610 E.Glendale Sparks NV 89510 Phone:702/356-9111 Rudi Schoenmackers SW Tech.Develop.Inst. PO Box 30001 Department 3 SOL Las Cruces NM 88003-0001 ., Phone:505/646-2639 Alex Sifford Geothermal Program Manager Oregon Department of Energy 625 Marion Street NE Salem OR 97310 Phone:503/378-2778 Fax:503/373-7806 WSNOSE1-Z219S6BlusojeD'sinegOSE}xO"g'O'dNOILVIDOSSVTWNYSHLOZSIWNOILVNNATIONAL GEOTHERMAL ASSOCIATION Short course on Power Generation from Low Temperature _|,,,.; Geothermal | Resources 350°F (170°C) or less May 6-7,1991 John Ascuaga's Nugget Hotel Sparks,Nevada PROGRAM Monday,May 6 7:30 am.-8:30 a.m.REGISTRATION AND CHECK-IN 8:30 a.m.-8:40 am.WELCOME AND PURPOSE OF COURSE David N.Anderson,National Geothermal Association 8:40 a.m,-9:40 am.LOW TEMPERATURE GEOTHERMAL RESER- VOIRS AND POWER GENERATION-Reservoir distribution and low-temperature power plant installations in the Western U.S. Thomas Flynn,University of Nevada,Las Vegas 9:40 a.m.-9:55 a.m.BREAK LOW TEMPERATURE POWER GENERATION _ TECHNOLOGY 9:55 am.-10:55 am.DESIGN OF LOW TEMPERATURE BINARY CYCLE POWER PLANTS Richard Campbell,The Ben Holt Company 10:55 a.m.-12:00 p.m.LOW TEMPERATURE FLASH STEAM POWER PLANTS Gary Shulman,Geothermal Power Corporation and Larry Green and David Mendive,Geothermal Development Associates 12:00 p.m.-1:30 p.m.LUNCH (everyone on own) 1:30 p.m.-2:30 p.m.IMPLEMENTATION OF MODULAR BINARY POWER SYSTEMS Yona Yahalom,Ormat Inc. 2:30 p.m.-3:30 p.m.MINIMIZING COSTS OF BINARY POWER SYS- TEMS -How to lower the cost per kw. Ken Nichols,Barber-Nichols Inc. 3:30 p.m.-3:45 p.m.BREAK 3:45 p.m.-4:45 p.m.A NEW APPROACH TO BINARY TECHNOLOGY Alex Kalina,Exergy Inc. Tuesday,May 7 8:30 am.-9:30 am.BINARY HEAT EXCHANGERS AND CON- DENSERS -Discussion on both Vaporizers and Condensers Homer Fager,Westland Engineering Company and D.G.Klaren, Scheffers of America,Inc. 9:30 a.m.-10:30 am.DOWNHOLE PRODUCTION PUMPS -Submer- sible and line shaft Jorge Gonzalez,Johnston Pump Company 10:30 a.m.-10:45 a.m.BREAK 10:45 a.m.-12:00 p.m.DRY COOLING TOWER TECHNOLOGY Robert Reichelm,Hudson Products Corp. 12:00 p.m.-1:30 p.m.LUNCH (everyone on own) 1:30 p.m.-2:30 p.m.WET COOLING TOWER TECHNOLOGY -Indud- ing cross flow and counter flow. Gary Harbison,Marley Cooling Towers2:30 p.m.-3:30 p.m.RECENT HEAT CYCLE RESEARCH Carl Bliem,Idaho National Engineering Lab 3:30 p.m.-3:45 p.m.BREAK 3:45 p.m.-4:45 p.m.COMPUTERIZED PRODUCTION MONITORING EQUIPMENT 'Robert Verity,Mesquite Group Inc. Kotzebue and Nome Coal Study Final Report January 1990 Purpose: To determine ways to utilize the coal reserves of northwestern Alaska as an abundant,economic, stable priced energy alternative to fuel oil for communities,military installations,and industries along the northern and western coasts of Alaska. Scope: Evaluate available coal resources,update the coal conversion and power conversion technologies and recommend a system concept to meet the energy needs of Kotzebue and Nome. Results: After consideration of potential coal-based power and district heating concepts and technologies, a recommended overall system was derived.The proposed system consists of burning coal in a circulating fluidized bed combustor (CFB).Heat generated by the CFB will be used as the motive heat source for an externally fired Brayton cycle,(air turbine).Compressed air from the air turbine compressor will flow through a regenerator to an external heat exchanger (in the fluidized bed)where it is expanded through the turbine section.A generator connected to the air turbine converts the power generated in the turbine section to electrical power for distribution to the community.The exhaust heat from the CFB combustor and the air turbine exhaust would be utilized as the heat source for the respective district heating systems. Delivered outputs from the system will be 4160 volt electric power and 250°F hot water for use in the district heating system. A district heating system would transfer the waste heat from the power system to the homes and buildings.Hot water produced by the heat exchangers in the power plant would be circulated by pumps through heating loops under the streets to the buildings to be served.These loops will consist of two paralleled insulated pipes,each of the same diameter.In one of these pipes will flow hot,(250°F),pressurized water from the power pliant and in the second pipe the cooler water (160°F),will flow back to the power plant. The proposed power plants and district heating facilities for Kotzebue and Nome are anticipated to come on line in 1995.One CFB combustor and one air turbine will make up a power system module of 2.5 MW capacity. The proposed replacement plant for Nome will consist of three power modules for a total installed capacity of 7.5 MW.It is anticipated the peak demand for Nome will be about 7 MW by 1995. The proposed power plant for Kotzebue will consist of two power modules for a total install capacity of 5 MW.The 1995 peak demand is estimated at 4152 KW. The report concludes that the abundance,quality and favorable economics of Deadfall coal make it the preferred energy source for this project. Continuing use of diesel generators to provide power in Nome over the next 20 years will require a subsidy of over $213 million.Switching to the proposed coal-fired power generation system will reduce the required subsidy to zero and provide a surplus (profit)of between $26 to zero and provide a surplus (profit)of between $26 million and $45 million. In Kotzebue,the results over 20 years are similar.The diesel option will require a subsidy of $137 million versus a profit of $68 million for a coal-fired power system with district heating. Since the economic and technical feasibility of mining western Arctic coal has been established in previous work and since the preliminary results of the Kotzebue and Nome Coal Study are encouraging in that it appears Kotzebue and Nome can be developed to use western Arctic coal economically and in an environmentally acceptable way,it is recommended the next stage of development include an in-depth engineering feasibility assessment of developing:1) coal-fired power plant and district heating facilities for the communities of Kotzebue and Nome; and 2)a coal mining industry in the western Arctic designed to meet the energy demand of both communities.Completion of this next phase of the project would provide final economic assessment and substantial design completion of all facilities associated with the mine and both communities.The completed documents would be used as a control document for project permitting,design document and bid preparation,and construction. Cost of Study: Funded by:Alaska Energy Authority (Contract No.LC 1822001) Work Performed by:Arctic Slope Consulting Group;Mechanical Technology,Inc. REDUCING THE CAPITAL COST OF BINARY POWER PLANTS Ken Nichols NGA -SHORT COURSE ON POWER GENERATION FROM LOW TEMPERATURE GEOTHERMAL RESOURCES Nugget Hotel Sparks,Nevada May 6-7,1991 INTRODUCTION The purpose of this paper is to consider the basic cost elements and equipment that make up a binary power plant and to look at the factors that affect the individual cost of' these elements.Under certain conditions,there are options available to the plant designer that will result in cost savings that should lower the installed cost per kilowatt.The conditions referred to are specific to the geothermal resource and the site where the plant will be located. The paper wil!attempt to show at least some of the relationships between the plant cost elements as well as the cost to produce the geothermal resource.om DESCRIPTION OF A BINARY POWER PLANT The elements of the binary power plant that will be considered for this study are as follows: RESOURCE PRODUCTION e Production wells e Pumps e Injection wells e Piping PLANT EQUIPMENT e Heat exchangers e Cooling system condensers e Turbine-generator e Feed pump e Piping and valves e Controls e Switchgear and protective relays os PLANT CONSTRUCTION e Civil work (includes concrete) e Mechanical (equipment placement and piping) e Electrical (wiring and hook-up) e Start-up ENGINEERING e Design and specifications e Construction coordination e Plant start-up SPRAY COOLING POND 3%COST 50Z PARASITICTURBINEGENERATORCINUENSE20COST,ceaseaeLADDDA)SL » || LP ee J _.=} FEED PUMP 1%COST ELECTRICAL AND CONTROLS 50%PARASITIC 10%COST = IY.IVIV/V/*DF COST BRINE HEAT EXCHANGER ON SITE CIVIL 2 9%COST |ON SITE MECHANICAL 10 DN SITE ELECTRICAL 10 _ENGINEERING g ] "THER "19WELLS&WELL PUMPS = BARBERNICHOLS BINARY PLANT COST AND PARASITIC POWER CONSUMPTION 3 MAY 1991 NH5-MOOULAR POWER PLANT os PLANT PERFORMANCE The overall plant performance can be stated as the watts produced per unit flow rate of the geothermal fluid as watts per pound per hour of flow.This is a useful parameter for evaluating and comparing plant designs because it indicates the amount of geo resource that must be produced.This performance factor is commonly called the brine utilization. This utilization factor is actually a function of two variables: 1.The amount of heat energy removed from the geofluid (the ST across the heat exchangers). 2.The cycie efficiency which is ratio of heat actually converted to electrical output to the total heat input. The cycle efficiency should include all internal plant parasitics such as feed pump and cooling system loads. Two different plants could have the same overall utilization factors.One plant might remove more heat from the fluid,but have a lower cycle efficiency while the other plant removes less heat,but converts this heat more efficiently.os NETOUTPUTMW/10°LB/HRUTILIZATION OF GEO-FLUID 2.0 :: 's0 S C«DSSCSSOSC"S*S*SCSMOTT BO RESOURCE TEMPERATURE F Barber-Nichols Inc.6 May 91 7 This is not as simple a trade-off as it first appears when considering the cost of heat exchangers.The heat transferred per unit area is a function of the driving AT.The AT's can be increased producing more heat into the system,but this usually lowers cycle efficiency in a detrimental way. To generalize,the most cost effective plant for a given utilization factor will be one with high cycle efficiency that minimizes the Btu's in and out as well as those running around internal to the cycle. The cost of producing the geofluid can vary widely.The cost to produce a deep,low productivity resource can be as high as $750-$1000/kW while a low temperature,shallow resource with high permeability can be produced for $200-$300/kW.The high cost resource becomes a major portion of the total facility cost and would drive one to use a high utilization factor.os. PLANT COSTS A breakdown of plant costs are shown in Table I.These plant costs are felt to be representative for a 4 to 20 MW,plant that would consist of one or more modules.This cost breakdown is based on a power cycle using ammonia as the working fluid which appears to offer a cost advantage for resource temperatures below 300°F.The schematic of this power plant shows a spray cooling system.The spray pond approach appears to have a significant advantage over a conventional cooling tower when the cost of land is low.The parasitics and cost are both lower than other heat rejection systems. The cooling system is much more expensive if dry cooling,i.e..air-cooled condensers are required.The cooling system is closer to $450/kW for dry cooling including the extra exhaust side piping and manifolding.The cooling parasitics are 200%higher requiring more resource and a larger plant for the same net output. Table II shows a comparison of the NH;plant to an IC,plant with the same net output.The IC,plant has the same utilization factor;however,it has higher internal parasitics which increases the cost of some elements.Also,the heat exchangers require more area due to lower heat transfer coefficients associated with IC,,.as TABLE I COST BREAKDOWN NH;-MODULAR PLANT Heat Exchangers Heat Rejection Components Turbine-Generator Feed Pump Piping and Valves Controls and Control Room Electrical Equipment Engineering Construction Management Bonds and Insurance Contingency Profit os 10 TABLE II COST COMPARISON NH; (S/kW) Heat Exchangers 107 Heat Rejection Components 125 Turbine-Generator 230 Feed Pump 18 Piping and Valves 50 Controls and Control Room 30 Electrical Equipment 34 Engineering 123 Construction 205 Management 35 Bonds and Insurance 55 Contingency 110 Profit _100 11 TABLE III HEAT REJECTION SYSTEMS .- Condenser/Spray Pond Condenser/Cooling Tower Air-Cooled Condenser Parasitic Power (%of Generator Gross Output) 6.5 11.8 HOT SPRINGS POWER COMPANY 6200 S.Syracuse Way *Suite 125 Englewood,Colorado 80111 (303)721-9550 Fax (303)779-8082 RECEIVED JUL 15 1992 July 7,1992 ALASKA ENERGY AUTHORITY Mr.Brent Petrie VIA FACSIMILE ALASKA ENERGY AUTHORITY (907)561-8584 P.O.Box 190869 Anchorage,Alaska RE:Unalaska Project Dear Brent: Thank you for taking my call regarding the Unalaska project.I first learned of the project from engineers and consultants with whom we work.You requested some information on our company. Hot Springs Power Company and its affiliates are experienced developers of independent power projects.We have substantial experience in geothermal, other projects have ranged from hydroelectric to cogeneration.Our most recent project,which is now successfully completing start-up,is the "Brady" project,a 28Mw (gross)plant supplying power to Sierra Pacific.We undertook the reorganization of a bankrupt geothermal company thereby acquiring the assets of geothermal leases and certain water rights.We typically focus on more difficult projects as in the Brady Project.We typically permit the plant,negotiate power sales agreements and prove-up the geothermal resource through drilling,and provide design and construction.We retain long-term ownership in the projects.We,also,provide the early development capital and bring in an institutional partner at the beginning of construction.I look forward to talking to you further about this opportunity. Sincerely, HOT SPRINGS POWER COMPANY flontyABteryhy?-BY:Randy §.Goldenhersh President RSG:bn FDC Freedom Development Co. May 12,1992 Brent Petrie cee \arAlaskaEnergyAuthority[etP.O.Box 190869 S Anchorage,AK 99519 Dear Brent Petrie: Alaska's Natural resources are going up in smoke.The people of Alaska are losing millions of dollars per year in lost State revenue.A new technology called the Biphase Tur- bine can separate oil and gas directly at the well head ata fraction of the cost of today's large gas refiners.I wrotetoalltheoilcompaniesinAlaskaandthey(Alaskan Oil Companies)are not interested in the Biphase turbine.RightnowthepeopleofAlaskaarelosingmillionsofdollarsan- nually because of the fact that the Oil companies have no interest in the Biphase turbine.YES the Biphase turbine worksl!!!.Right now Alaska gas resources are being wasted. The Biphase turbine was developed at the Jet Propulsion Laboratory in California by Dr.Lance Hays and Dr.David G. Elliot.The Biphase turbine has been used for Geothermal pow- er to separate brine and water.Please find enclosed a brief on Biphase turbine opens new geothermal reserves.Unfortu- nately the Biphase turbine has not been applied to the sepa- ration of oil and gas.But,top scientists say the Biphase turbine would be ideal for the separation of gas and oil at the well head. Naturally the oil companies are not interested sincethey(the Oil Companies)do not understand the Biphase tur- bine.But top U.S.Scientists who researched the Biphase tur- bine for many years say the Biphase turbine is very compactandwillopenuplargereservesofU.S.Gas (Like AlaskanGas)which will generate millions of dollars of State reve- nue for the State of Alaska. 8 Arlington Street @ Auburn,Massachusetts 01501 @ (508)755-9316 page two Brent Petrie,I need creativity from your staff to tap into State funds to build a multimillion dollar manufactur- ing factory in the City of Anchorage which will manufacture Biphase turbines to be used to separate oil and gas in Alas- ka.Creativity has to be used since we have no available funds to obtain a loan through conventional loaning chan- nels. As you can see Brent,we need your help in obtaingStatefunds,in which the State of Alaska and it's people will be payed off handsomely from the Sale of Gas which isnowbeingwasted. I hope you have the right people on your staff that can pulltherightstringstoobtainStatefundstobuildBiphase turbines to turn a "wasted"by product into a major money maker for the Alaskan people. I await your reply. Very truly yours, DOM DEVHLOPMENT COMPANY Daniel J Mahoney Presiden i i luable gas fromPS:The Biphase turbine not only separates va _f£4theoil,pat generates electricity in the process from it's rotating shaft. opens new geothermal reserves ete NB me Ne ue.Teg ste ate ©te eer ge be we Sade' Now portable plants can tap energy from superhot steam and liquid By JIM SCHEFTER DRAWING BY RUSSELL VON SAUERS At 45-plus tons,the unique turbine and its flanking generators hardly looked portable.The eight-by-30-footskidholdingtheequipmentisnot something you'd carry along to the wilderness or tuck in a corner of your garage for emergency use. But by industrial standards,the 2.2-megawatt geothermal power plant is writing a new definition for portability.Developed at Biphase En- ergy Systems in Santa Monica,Calif.,it is based on a significant advance inturbinetechnology.The portable plant was recently installed on a sin- gle geothermal well in Utah and has been undergoing shakedown tests. "It's designed as a general unit that can go on any geothermal well,”Dr. David Klipstein,managing director of Biphase,told me. If a well cools off or goes dry,the turbine unit can be picked up and moved elsewhere.And because one power plant works from one well,it's not necessary to bring in an entire geothermal field and build a large, permanent facility before generating electricity. "This system will allow a producer to begin generating power and recov- ering investment much earlier than before,”Klipstein said. The advance that makes this possi- ble,and opens a wider range of geo- thermal temperatures to electric gen- eration,is a biphase turbine,so called because it generates power from both the liquid and steam phases of super- heated water.Ordinary turbines use only the steam.Furthermore,the biphase turbine handles mixtures of steam and liquid,separating them with extraordinary efficiency while it extracts their energy. "This is a wet system,”Klipstein explained,"operating under much more variable conditions than dry- steam systems powered by the geysers in northern California.” The system is so flexible,in fact, that versions can be used for water desalination,,industrial waste-heat recovery,oil and gas separation,and marine power plants.Because of its design,liquids pass through the tur-bine in a fraction ofa second.That's sofastthatthetraditionalproblemsof salt scaling and corrosion caused by geothermal brine or other liquids are significantly reduced. Magnetohydrodynamics spinoff Inventors Lance Hays and David G. Elliot came up with the biphase con- cept while working on magnetohydro- dynamics |PS,Aug.'78]at the Jet Pro-* pulsion Laboratory.They founded Bi- phase Energy Systems,then were acquired by Research-Cottrel!Energy Companies.Commercial deliveries of biphase turbine systems,under a joint venture with Transamerica Delaval,: are expected to begin in 1982. The basic biphase turbine has three major components-a two-phase noz- zle,a rotary separator,and a liquid turbine.Depending on the applica- tion,the liquid turbine can be left out or be replaced by some other device. In standard flash-steam and geo- thermal systems,a two-phase flow of steam and water droplets is forcedunderpressurethroughaflashorifice.Beyond the orifice,the available vol- ume expands suddenly.Steam . "flashes”and moves on;the water' droplets fall away to become a flowing !liquid.Only the steam goes on to pov ' er the turbine blades. In the biphase system,a two-phase nozzle replaces the flash orifice.Tre nozzle's cross section gradually shrinks,increasing pressure;then.gradually enlarges,reducing pres-. sure.The result is a uniform mix com.| posed of steam and brine droplets, with the droplets accelerated by the steam. Now the motion energy of the steamandthebrine,as well as the thermi energy of the steam,can be extract.d (see diagram). The power piant installed at Roose: velt Hot Springs,Utah,where geo- thermal temperatures are about 360 degrees F,employs both a 600-kilo- watt steam turbine at one end of the portable skid and a 1.6-megawatt liq- uid turbine at the other end.Power is fed into the local utility grid. The system's dual rotary separa'>r wheels are 54 inches in diamet r. There is enough residual energy in the brine to power a diffuser used to rein- ject the used liquid into the ground. Reinjection not only prolongs the life of the well but eliminates environ- mental concerns about waste-brine disposal and maintains subterranean hydraulic pressure to prevent terrain subsidence. For cooler wells,only the liquid tur bine generator and a reinjection pu:1p would be used.The biphase system can be installed on geothermal wells of less than 300 degrees to more than 500 degrees.Until now,cost has keptthecovlerwellsfrombeingexploited for energy. "The hotter wells are competitive now,”Klipstein told me,"but it's the cooler wells that will ultimately be the ed Energy extraction starts in a biphase tur- bine when a mixture of hot brine and steam feaves the two-phase nozzle and strikes the primary separator et about 99 psi.Steam,spun off by centrifugal force, can be routed t8 another turbine to help power an electric generator (diagram, right).The liquid spins the separator and =flows around the rim and through holes toinsidethewheel.Smalt,U-shape tubes mounted on the power turbine intercept this ring of liquid,spinning the power tur- bine and the power-out shaft for the gen- erator.Brine flow is switched 180 degrees by the U-tubes,supplying high torque and spinning the secondary separator in the opposite direction.This concentrated brine is then tapped for reinjection into the geothermal well.In some biphase-tur- bine applications,such as waste-heat recovery,the water from the turbine exhaust and condenser is pumped back into the two-phase nozzle.Other versions have also been developed. How biphase turbines tap the Earth's energy PRIMARY SEPARATOR GEOTHERMAL-BRINE INLET FLOW TWO-PHASE NOZZLE SEPARATED STEAM BIPHASE TURBINE ELECTRIC GENERATORTWO-PHASE . FROM WELL POWER =TURBINE STEAM |OUTPUT\SHAFT EXHAUST TURBINE CONCENTRATED HIGH-PRESSURE CONDENSER BRINE REINJECTED INTO WELL SECONDARY SEPARATOR a workhorses of the geothermal busi- ness.” Klipstein estimates that a biphase power system can be installed forabout51,000 per kilowatt.That com- Par:.-rith current costs of between $1,+and $1,500 per kilowatt forlargecoal-fired plants,he said.Cost of energy over the lifetime of the system would be in the range of six to 10 cents _Per kilowatt hour. Smaller biphase systems were test-ed in 1979 and 1980 on geothermalWellsinCalifornia's Imperial Valley,Raft River,Idaho,and the Utah site.e field experience confirmed calcu-lation.that a biphase turbine wouldent20to40percentmoreelec-tricity from a given well than wouldashsteamsystems.f t was proof that led to the currentwll-scale Utah demonstration,Klip-Stein reported. "Measured performance in the labo- ratory and in the field agreed to with- in 10 percent of the predicted values,” he said.° Klipstein expects utilities with geo- thermal resources to "take this whole business very seriously.”The industry already is looking at 50-megawatt installations-10-20 geothermal wells,each with a biphase-turbineunitinstalled&s soon as a well is drilled and proven. Turbine economics "There is no end of fascinating applications for biphase-turbine tech- nology,”Klipstein said."But each one needs to prove itself economically.” Among applications already being studied or in development: @ Using industrial-flow streams, such as blowdown from large boilers, tems require expensive equipment to separate steam from water droplets before injection into a turbine.The biphase turbine takes a blowdown mixture as is and produces power as part of the separation process. @ Replacing current equipment used to separate oil and natural gas coming from the same well.The biphase turbine not only separates the two,but would generate electricity in the process. @ Power generation from industri- al heat now wasted.Even such simple heat-catchers as exhaust mufflers can provide enough energy to drive a biphase turbine generator. "People are fascinated by biphase turbines,”Klipstein said."We con- stantly hear from outsiders with new ideas.But we're so tied up with our own fascinations that we don't have time to pursue them.”to generate electricity.Present sys- Pee ee mm sey ee AN INTRODUCTION TO GEOTHERMAL R ES O URCES ;4 Cathearal Hill Hotel San Francisco,California March 22 -23,1992 National Geothermal Association P.O.Box 1350 +Davis,CA 95617-1350 (916)758-2360 ©Fax:(916)758-2839 Course An Introduction to Geothermal Resources Cathedral Hill Hotel *San Francicso,California March 22-23,1992 The Course This course is being offered at the request of numerous companies and agencies who have new employces on thcir staffs with little or no overall knowledge of geothermal exploration and exploitation.The function is designed to provide a broad view of geothermal energy,which will allow an attendee to understand his or her part in its development.The back- ground provided can immediately enhance an attendece's understanding of your present geothermal program and potentially save valuable man- hours in the future. The last time this course was offered was in 1988 by the GRC,and it may not be offered again until 1994. Special Consideration This course has been scheduled just prior to the U.S.Department of Energy's 1992 Geothermal Program Review,which will be convened in the same hotel from March 24-26.For further information on the 1992 DOE Program Review Meeting conta:t:Linda Kurkowski or Mary Janes at BNF Technologies Inc.,4300 King Strect,Suite 310,Alexandria,VA 22302; phone:(703)671-0100,fax:(703)998-3832.By scheduling this function on the Sunday and Monday just prior to the DOE Program Review,the following benefits can be obtained: 1.Air travel will be less expensive,as attendees will have to stay over Saturday night. 2.You or your employee will only be out of the office during one work day. 3.Room rates will be also be less expensive,due to the room block acquired by DOE. 4,Attendees can accomplish two tasks:attend the course and the Program Review with only one trip. 5.Attendees can spend a weekend in San Francisco. SL Speakers The speakers have been drawn from a wide range of disciplines.All have considerable expertise and experience in their fields,and have been specifically selected to lecture on various aspects in their vocation.Collec- tively,the data and thought to be presented by the speakers will be related to the state-of-the-art in geothermal exploration and development. Study Guide Each attendee will receive,upon registration of the course,a compila- tion of papers,notes and outlines related to the topics to be discussed. These papers will be contained in an indexed three ring binder which will be available during the course registration. Who Should Attend The course will be extremely useful to anyone new to geothermal development.This includes earth scientists,engineers,biologists,pro- gram managers,economists,financiers,accountants and administrators. Location The course will be held in the Cathedral Hill Hotel,1101 Van Ness at Geary,San Francisco,California 94109-6986,(415)776-8200,(800)227-4730 in the continental U.S.or (800)622-0855 in California. Hotel Reservations Reservations should be made directly with the hotel using the attached form by March 9,1992.A block of sleeping rooms has been reserved for the nights of March 21-22.Room rates are $79 single and double,plus 11 percent room tax.A first nights deposit must accompany Reservation Form.When making telephone reservations,be sure to mention the DOE Geothermal Program Review in order to receive the reduced rate. Check-in time is 3:00 p.m.,check-out time is 1:00 p.m. NOTE:After March 9,1992,all rooms in the DOE's block not already reserved will be released for sale to the public.The NGA cannot guarantee participants a room at the convention rate after that date. Parking Parking is complimentary for hotel guests.All other participants receive a discounted rate of $7 per day. Airport Bus Airport bus service is available to the Cathedral Hill. e Associated Limo .............(415)431-7000;$10.00 *Door-to-Door Airport Express .(415)775-5121;$9.00 ¢Lorrie's Travel &Tour ........(415)334-9000;$9.00 ¢Super Shuttle ................(415)558-8500;$10.00 *Yellow Airport Van Service ...........00e0005 $9.00 When leaving the hotel for the airport,please make arrangements at least 24 hours in advance to confirm your seat. Registration To register,complete the attached form and mail with payment,pur- chase order,or credit card number (Visa,MasterCard,American Express or Diners Club)to National Geothermal Association,P.O.Box 1350,Davis, California 95617.Fees for the course are: $375 -Current 1992 GRC/NGA Members . (includes employees of 1992 Corporate Members) $400 -Non-Members $100 -Full Time (accredited)Students Cancellation Policy If you must cancel your registration,be sure to call the NGA office by March 9,1992.Cancellations received before March 9,1992 will be refunded,less a $25 handling fee.Cancellations received after March 9, 1992 cannot be refunded.SUBSTITUTIONS MAY BE MADE AT ANY TIME. PROGRAM Saturday,March 21 5:30 p.m.-7:30 p.m.-EARLY REGISTRATION CHECK-INpoalaseeees Sunday,March 22 7:30 a.m.-8:30 a.m.-LATE REGISTRATION AND CHECK-IN 8:30 a.m.-8:45 am.-WELCOME AND INTRODUCTION David N.Anderson,Geothermal Resources Council 8:45 a.m.-10:00 am.-NATURE AND OCCURRENCE OF GEOTHERMAL RESOURCES:The resource,its various manifes- tations,world distribution,occurrence in the western United States, types of reservoirs and a brief history of development. Mike Wright,University of Utah Research Institute 10:00 a.m.-10:15 a.m.-BREAK 10:15 a.m.-11:45 am.-EXPLORATION TECHNIQUES AND STRA- TEGIES:Discussion of the exploration methods and techniques now in use,their value,limitations and various exploration strategies being used by resource developers. Mike Wright,University of Utah Research Institute 11:45a.m.-1:15 p.m.-LUNCH 1:15 p.m.-2:45 pm.-DRILLING GEOTHERMAL WELLS:Well planning,drill site construction,drilling mediums (air,mud,etc.) tools,types of rigs and special adaptations,blowout prevention, preliminary reservoir tests,and other considerations. Pat Sullivan,Grace Drilling Company becaeleatak 2:45 p.m.-4:00 p.m.--WELL COMPLETION:Casing design,cement- ing methods,cements,casing problems,wellhead design,wellhead problems and production valves. Louis Capuano,ThermaSource Inc. 4:00 pm.-4:15 p.m.-BREAK 4:15 pm.-5:15 pm.-INSTITUTIONALV/ENVIRONMENTAL: Overview of local,state,and federal regulations,legal problems,and status of development.Comprehensive view of environmental problems,mitigation measures,long-term effects and related problems. Dana Brock,Dames and Moore Monday,March 23 8:00 am.-9:00 am.-NON-ELECTRIC USES:Introduction and historic use worldwide,occurrence,exploration and development, range of uses,heat pumps and economics. Paul Lineau,Oregon Institute of Technology, Geo Heat Center 9:00 a.m.-10:30 am.--RESERVOIR ENGINEERING AND FIELD DEVELOPMENT:Common reservoir types and their characteris- tics,limitations,assessment,well and field performance,unitization and development requirements and injection of waste fluids. Subir Sanyal,GeothermEx,Inc. 10:30 a.m.-10:45 am.-BREAK 10:45 a.m.-12:00 p.m.-POWER PLANTS:Basic power cycles,match- ing systems to reservoirs,descriptions of most used systems and their limitations,corrosion/scaling problems,reactor/clarifier sys- tems,mineral recovery,modular units,world statistics,trends and basic problems. Ben Holt,The Ben Holt Co. 12:00 p.m.-1:30p.m.-LUNCH 1:30 p.m.-2:30 p.m.-EXPLORATION AND FIELD DEVELOP- MENT ECONOMICS:Leasing,exploration,permitting,environ- mental reporting,drilling,well completion,and reservoir evalua- tion. Susan Petty,Consultant 2:30 p.m.-3:30 p.m.-POWER PLANT ECONOMICS:Competing energy sources,power cycle decision and plant design costs,power plant construction,operation and maintenance costs. James Kuwada,Consultant 3:30 p.m.-3:45p.m.-BREAK 3:45 p.m.-4:45 p.m.-FINANCING GEOTHERMAL DEVELOP- MENT:Project planning,basic considerations,go/no-go decisions, reservoir evaluation,risk analysis,funding packages and funding sources. Domenic Falcone,Creston Financial Group 4:45 p.m.ADJOURNMENT Hotel Reservation Form U.S.Department of EnergyProgramReview10 March 20 -28,1992 PLEASE PRINT Name(s) Company Address City State Zip Phone()Fax() Anival Date Anival Time Departure Date No.of Nights No,of Guests No.of Rooms 1 $79 Single -plus 11%tax 0 $79 Double -plus 11%tax QO $125 -$160 -Hilltop Club O)Non-Smoking (subject to availability) (Concierce floor) DEPOSIT AMOUNT §(First Night) One night's deposit or credit card number (MasterCard,Visa,American Express,Diners Club)must accompany this form or reservations will be automatically cancelled.Forty-eight hour notice of cancellation is required for refund of deposit. Charge card information (Circle one) M/C Visa Am/Ex Diners Club Account No.Exp.Date Signature Check-in time is 3:00 p.m.;Check-out time is 1:00 p.m. Reservation requests received after March 9,1992 will be confirmed subject to room availability. Mail to:Cathedral Hill Hotel Attn:Room Reservations 1101 Van Ness at Geary San Francisco,Califomia 94109-6986 Or call:(415)776-8200 or (800)662-0855 (in California)Makrhe Registration Form An Introduction to Geothermal Resources March 22-23,1992 OFFICE USE ONLY Cathedral Hill Hotel San Francisco,California Receipt No. (1)check here if this is a new address or address correction. PLEASE PRINT and use a separate REGISTRATION FORM for each person registering. NAME (LAST)FIRST M ORGANIZATION/COMPANY - ADDRESS USA CITY STATE ZIP. PHONE FAX REGISTRATION FEE:(Poyment MUST accompany this form) _____$375 Current 1992 GRC,NGA Members (includes employees of 1992 corporate members) -__.$400 Non-Members $100 Full-Time (accredited)Students CANCELLATION POUCY:If you must cancel your registration,be sure to call the GRC office by March 9,1992.Cancellations received before March 9,1992 will be refunded less a $25 handling fee.Cancellations received after March 9,1992 cannot be refunded.SUBSTITU-TIONS MAY BE MADE AT ANY TIME. PAYMENT (Check appropriate method) ____Check enclosed (make payable to GRC) Our Purchase Order is attached (Government Agencies Only) __.__.Charge my Credit Card ___VISA M/C ___A/E _Diners Club Card Number Exp.Date SIGNATURE DATE Please retum this form fo the NATIONAL GEOTHERMAL ASSOCIATION P.O.Box 1350 «>Davis,CA 95617-1350 ©USA.©(916)758-2360 Fox:(916)758-2839 +Telex:882410 NATIONAL GEOTHERMAL ASSOCIATION P.O.Box 1353 Davis,California 95617-1350 USA David Denig-ChakroffAlaskaPowerAuthorityFOBox190869AncharageAK93519-0869 FIRST CLASS MAIL | U.S.POSTAGE PAID DAVIS,CA Permit No.32 | "kL DESIGN OF LOW TEMPERATURE BINARY CYCLE POWER PLANTS Richard CampbellTheBenHoltCo. Pasadena,California osI.Cycle Optimization A.Cooling Options 1.water-cooled cycles a.require cooling water supply b.chemical requirements c.cooling tower plumes d.cooling water blowdown disposal 2.air-cooled cycles B.Thermodynamic Optimimum 1.match heating curve of working fluid to cooling curve of brine pure fluids vs.mixtures consider heat recovery (regenerators)-YNthermodynamic optimum is probably not economic optimum,but is good starting point for economic optimization C.Resource Utilization 1.maximum brine utilization gives highest kWh/Ib brine Page 1 oweee2.limited by resource characteristics (eg.minimum injection temperature)osD.Economic Optimization and Final Cycle Selection 1.key working fluid properties a.cost b.availability c.potential hazards 1.toxicity 2.flammability d.vapor pressure at operating temperatures 1.if below atmospheric will draw air into system 2.high vapor pressures cause high equipment costs 2.power sales agreement a.peak-weighted power sales may influence type of cooling and other parameters 3.environmental and permitting constraints 4.balance thermodynamic optimum with equipment costs (eg. approach temperatures in heat exchangers) 5.financial constraints (eg.use of proven technology to convince a lender to finance a project) 6.optimum design is one which gives highest return on investment Page 2 Materials of Construction A.Working Fluid Loop 1.usually a noncorrosive fluid 2.carbon steel can generally be used B.Geothermal Brine Side 1.depends upon the resource 2.carbon steel can frequently be used Equipment Selection A.Turbines 1.radial in-flow 2.axial flow B.Heat Exchangers 1.shell-and-tube 2.low-fin vs.bare tubes Page 3 os C.Pumps 1.geothermal production 2.geothermal injection 3.working fluid circulation D.Heat Rejection 1.air-cooled cycles utilize air-cooled condensers 2.water-cooled cycles a.cooling towers b.condensers c.cooling water pumps E.Other 1.electrical 2.auxiliary systems a.instrument air b.firewater Page 4 osa EXERGY,INC. HAYWARD,CA Alexander I.Kalina President SYSTEM AND PROCESS(THERMODYNAMICPOWERCYCLE)FOR | CONVERSION OF GEOTHERMAL HEAT TO ELECTRIC POWER Introduction Conversion of geothermal energy into electric power represents an important and growing area of power generation.Geothermal power plants fall into three categories:steam,flash and binary.In the first two,the geothermal source is utilized to produce steam,which is then expanded in a turbine to gen- erate electrical power.In binary plants,the heat extracted from the geofluid is used to evaporate the working fluid of the power cycle,which is then expanded to produce power. The technology currently being used for low-temperature geothermal heat sources is the organic Rankine cycle.However,this design contains some sig- nificant irreversible thermodynamic losses.For example,there is a mismatch between the hot brine as it enters the evaporator and the much cooler work- ing fluid leaving the evaporator.This thermodynamic loss manifests itself as lower efficiency and higher brine consumption per unit of electrical output. The Kalina cycle system 12 is a more efficient alternative for low temperature geothermal applications.This higher efficiency results in reduced costs and improved economics.The Kalina cycle systems 3 and 11 also offer significant improvements for low temperature geothermal resources.These topics are discussed more fully in the following sections.os Kalina Cycle System 12 (KCS12) The subject power cycle operates at an efficiency significantly higher than that of a supercritical Rankine cycle and even more so than a_subcritical organic Rankine cycle.The working fluid used in the process of the presented system is a mixture of two components -low boiling and high boiling.It is well known that mixtures boil at variable temperatures.Thus,the temperature at which boiling begins at any given pressure (bubble point)is lower than the temperature at which evaporation is complete (dew point).Conversely,if the mixture is condensed,the temperature at which condensation starts is higher than the temperature at which condensation ends.The difference between the dew point and bubble point depends on the properties of the com- ponents and the composition of the mixture itself.The distinctive feature of the subject system is that the mixture selected has an initial temperature of boiling at high pressure (boiler pressure),which is significantly lower than the initial temperature of condensation at low pressure (condenser pressure). This feature allows utilization of rejected heat (turbine exhaust)to be used for initial evaporation and preheating of the working fluid.As a result,the heat extracted from geothermal brine is used only for high temperature purposes. This increases thermodynamic reversibility and results in increased effi- ciency of the power cycle. A.Operation The subject system is presented in Figure 1 and Table 2 and works as follows: The completely condensed working fluid at a temperature which is close to ambi-ent,point 14,is pumped by P-1 to high pressure at point 21.Thereafter, the working fluid at point 21 passes through a recuperative preheater HE-2, where it is preheated by a returning stream at point 60.The working fluid at point 60 is near the boiling point,i.e.,saturated liquid or slightly subcooled. There-after,a stream of working fluid is split into two substreams,points 61 and 62,respectively.Substream,point 61,passes through heat exchanger HE- 3,where it boils,being heated by a stream of geofluid.This substream exits af HPT LPT 1 25 3 8 32 HE-7 q HE-6& 26 7 T 8 68 3 36 |HE-S eet Tt 64 63 3 ¥|HE-3 1 |HE-4 51 62 38 HE-2 --=232421a ' |{|He-1 | 23 4 0 aaao >Kalina Cycle/14 y = Pa CONCEPTUAL FLOW DIAGRAM LEGEND . SYSTEM 12 Working solution , (38 Mar 1998) Brine Cooling water KCSle2 FIGURE 1 Be os KALINA CYCLE -SYSTEM 12 STATE POINTS Stream P(psia Fluid TCE)H(Bru/]b)Flowflb/hr) ]Brine 330.00 4.000,000 2 Brine 270.27 4,000,000 3 Brine 239.22 +,000,000 4 Brine 170.00 4,000,000 5 Brine 330.00 2,803,417 6 Brine 330.00 1,196,583 7 Brine 270.27 2,803,417 8 Brine 270.27 1,196,583 9 Brine 170.00 4,000,000 14 123.96 A-A 75.00 8.38 1,324,240 21 457.75 A-A 75.00 9.93 1,324,240 23 Water 68.00 41,393,895 24 Water 81.28 41,393,895 25 437.82 A-A 315.00 725.33 1,324,240 26 256.34 A-A 257.72 .688.95 1,324,240 29 127.54 A-A 123.87 423.46 1,324,240 30 248.34 A-A 315.00 744.00 1,324,240 36 134.88 A-A 228.60 700.96 1,324,240 38 130.38 A-A 170.00 525.59 1,324,240 60 452.70 A-A 165.00 112.06 1,324,240 61 452.70 A-A 165.00 112.06 727,008 62 452.70 A-A 165.00 112.06 597,232 63 449,92 A-A 223.60 500.94 727,250 64 449.92 A-A 223.60 500.94 597,232 66 449.92 A-A 223.60 500.94 1,324,240 68 445.62 A-A 257.72 596.35 1,324,240 A-A represents 87.3 weight percent ammonia in water mixture. TABLE 1 as heat exchanger HE-3 at point 63.Another substream at point 62 passes through recuperative heat exchanger HE-4,where it is heated by a returning stream of condensing working fluid and is partially evaporated.This substream leaves heat exchanger HE-4 at point 64. Thereafter,both substreams,at points 63 and 64,respectively,are recombined into one stream,at point 66.A stream of working fluid at point 66 passes through heat exchanger HE-5,where it is heated by a stream of geofluid and is evaporated completely or almost completely and exits heat exchanger HE-5 at point 68.While the stream of working fluid at point 68 is usually in a state of saturated vapor,it can be as well in a state of non-completely evaporated mix- ture or superheated vapor.Thereafter,a stream of working fluid at point 68 passes through heat exchanger HE-6,where it is superheated by a stream of geofluid to point 25.The stream at point 25 is sent into the high pressure tur- bine (HPT)where it expands,producing power and exits at point 26.The stream at point 26 is then sent into the reheater HE-7,where it is reheated again by a stream of geofluid to point 30.The stream at point 30 is sent to the low pressure turbine (LPT)where it is finally expanded,producing power and exits at point 36. In the subject system,the stream of working fluid at point 36 is close to or in a state of saturated vapor.The pressure at point 36 is chosen in such a way to provide complete condensation of this stream at available temperature of the cooling medium,i.e.,water or air.The stream at point 36 passes through heat exchanger HE-4,where it partially condenses,providing part of heat needed for initial evaporation of oncoming stream (process 36-38 versus 62-64)to point 38.Thereafter,the stream at point 38 passes through recuperative preheater HE-2,where it further condenses,providing heat for preheating the oncoming stream of working fluid.The returning stream of working fluid exits recuperative preheater HE-2 at point 29 (process 38-29 versus 21-60). Partially condensed returning stream of working solution finally enters con- denser HE-1,where it is cooled by water or air (stream 23-24)and finally com- pletely condenses to point 14.The cycle is closed.os A stream of geofluid initially at point 1 is split into substreams at points 5 and 6,respectively.A substream of geofluid at points 5 and 6 passes through heat exchangers HE-6 and HE-7,respectively,providing heat for superheating of oncoming stream HE-6 and reheating of working fluid vapor in between tur- bines via HE-7.The substream,initially at point 5,exits heat exchanger HE-6 at point 7,and a substream of geofluid,initially at point 6,exits heat exchanger HE-7 at point 8.Thereafter,substreams of geofluid at points 7 and 8,res-| pectively,are combined into one stream at point 2.The stream of geofluid at point 2 passes through heat exchanger (boiler)HE-5,where it is cooled,pro- viding heat for final evaporation of the entire oncoming stream of working fluid and exits this heat exchanger at point 3(process 2-3 versus 66-68).There- after,the stream of geofluid passes through heat exchanger HE-3,where it is finally cooled,providing heat for initial evaporation of only part of oncoming stream of working fluid (another part of oncoming stream of working fluid is initially evaporated by recuperation of heat from returning stream).There- after,a stream of geofluid exits heat exchanger HE-3 at point 4,after which it is reinjected into the geofluid strata. B,Performance Utilization of the heat available from the vapor turbine exhaust to preheat the working fluid after the condenser is a well-known feature of power systems. The specific and unique feature of KCS12,as mentioned before,is that the initial temperature of condensation of the returning stream (point 36)is higher than the initial temperature of boiling of the oncoming high pressure Stream (point 60),which allows partial evaporation by heat recuperation. As a result of the variable boiling temperature of the working fluid and high degree of recuperation,the KCS12 is much more efficient than other systems. In a recent study,Calpine Corporation compared a cascade binary Rankine cycle (CRC)to the KCS12.They assumed an initial temperature of 330°F,a final temperature of 170°F,and a flow rate of 4,000,000 Ibs/hr.(This is the case pre- sented in Figure 2.)They concluded that,from an identical resource,the CRC os would produce 17.8 MW net,whereas the KCS12 would generate 25.5 MW net. This is a 43%increase in output.See Table 2. Cc.Cost Comparison The Calpine study concluded that the cost per unit of power from KCS12 is approximately 40%less than with the CRC.This reduction is due to several fac- tors.First,the increase in efficiency means that less brine needs to be pro- cessed for each kW of electricity produced.Thus,for each unit of output,there is a reduction in well cost,brine gathering system,heat transfer surface,cool- ing tower,etc.Second,since the molecular weight of ammonia is very similar to that of water,standard steam turbines may be used.This reduces the rela- tive cost of the turbine.Finally,the necessary surface per unit of heat trans- ferred is reduced because the specific heat of ammonia/water mixtures is more than twice that of hydrocarbons or chlorofluorocarbons.Tables 3 and 4 contain a detailed cost comparison of the two systems. D.Economic Comparison The significantly lower cost of producing electricity with the KCS12 results in a decrease in the threshold sales price of electricity.For example,using the costs described above,a sales price of 5.5¢/kWh would generate a 16%return with KCS12,whereas a sales price of 9.0¢/kWh is required to produce the same retum with the CRC. The impact of the lower cost on returns to the investor is compelling.An economic comparison was made of two 30 MW plants,one using the KCS12 and the other using the CRC.Plant and wellfield costs were taken from the report by Calpine.With the exception of cost,all other assumptions for the two plants were held constant.See Table 5 for a list of the major assumptions. At an electricity sales price of 6¢/kWh,the after-tax return using the KCS12 is 18%,and the net present value at 15%is $7.1 million.Using the CRC,the after- tax return is 7%and the net present value at 15%is 34.7 million.os Gross Output (MW) Parasitics (MW) Net Output (MW) Initial Brine Temperature (°F) Final Brine Temperature (°F) Brine Flow Rate (lbs/hr) Cooling Water Temperature (°F) Specific Brine Flow (Ib/kW) TABLE 2 4.0 million 68 156.9 4.0 million 68 224.7 os Site Work Civil Work Structural Architectural Mechanical Electrical Insulation and Painting Start-Up and Indirects Equipment Purchase TABLE 3 Pow Plan Total Plant Equipment and Installation Engineering,Procurement, Management and Start-Up Contingency @ 15%for KCS12 10%for CRC Construction TOTAL ESTIMATED INSTALLED PLANT COST Wellfield Costs TOTAL ESTIMATED PLANT AND FIELD Cost Per Kilowatt KCS12 405,000 3,849,000 216,000 94,000 2,230,000 2,354,000 770,000 1,668,000 18,813,000 30,399,000 5,117,000 4,560,000 40,076,000 18,709,000 $58,785,000 $2,306 CRC 419,000 3,249,000 120,000 129,000 1,700,000 2,500,000 770,000 1,668,000 31,394,000 41,949,000 4,907,000 4,195,000 51,051,000 18,709,000 $69,760,000 $3,924 os TABLE 4 Heat Exchanger Pressure Vessels Pumps Cooling Tower,Fumish &Install Turbine/Generator Control Panel Pipe,Valves &Fittings BV-1 Storage Drums,2 each BP-1,I-Cs5 Transfer Pumps,2 each Cooling Tower,Fumish &Install Rankine Cycle Modules Control Panel Pipe,Valve &Fittings $3,200,000 931,000 2,382,000 2,625,000 6,180,000 1,797,000 1.698.000 $18,813,000 $656,000 2,320,000 2,625,000 21,090,000 1,400,000 3.303.000 $31,394,000 as. TABLE 5 Economi mparison Sales Price: Utilization: Operating Costs: Maintenance Costs: Debt Repayment: Interest Rate: Tax Depreciation: Technology Licensing Fees: 6.0¢/kWh with 5%escalation 7800 hours 0.5¢/kWh 2.5%of plant cost Straight line over 15 years 11% Straight line Not Included os Other Systems There are two other Kalina cycle systems for low temperature geothermal applications with which it is important to be familiar. A.System 3 -Very Low Temperature Resources The Kalina cycle system 3 (KCS3)was designed for resources below about 260°F.See Figure 2 for a schematic of KCS3.At this relatively low tempera- ture,the brine required to generate each kW is fairly high for any system. However,the relative improvement of the Kalina cycle over the organic Ran- kine cycle increases as the temperature of the brine falls.At 260°F,the effi- ciency improvement of the Kalina cycle rises to approximately 65%.With this increase in output,there are situations where it is economic to build a plant for such a low temperature resource. The most typical situation is an existing plant which is rejecting brine,fre- quently from a single or double flash process.In this case,the brine collec- tion field and all of the plant infrastructure (roads,buildings,etc.)are in place.The higher cost of the plant is offset by omitting these other items. B.System I1 -Combination of Brine and Steam The Kalina cycle system 11 (KCS11)was developed to provide a simple,yet highly efficient,solution to resource condition in which there is both brine and steam.See Figure 3 for a schematic of KCS11.This demonstrates the ease with which the Kalina cycle can be adapted to varying resource conditions. For the brine/steam case,KCS11 generates even greater output than KCS12 and at a lower cost per kilowatt.Since this system has only one turbine stage and fewer heater exchangers,the equipment and installation cost is reduced.of (ill!_"\7 30 G |i one) °. -__ i "-s5 |6 FT 2 36 13 712 7 ss 34 2}?4}43 iz RPH-1 |}|RPH-2 20k Sh mE 38 7 m1 =™ 25el24777 1 ||}|e | 23! oo P LEGEND Kalina CycleBrine Working Solution Basic Solution Enriched Solution Lean Solution Cooling Water CONCEPTUAL FLOW DIAGRAM SYSTEM 3 (31 Aug 1998) KCS3 FIGURE-2 O--_14 Figure 3 steam 1 | | l | 7 1 ie 68 ij brine 6 |'36 Y | 66 3 al 63 64 Y A Ay 61 62 384-a]- 60 Ay 21 29 A y Kalina Cycle System 11 Geothermal brine/steam os Application of the Kalina Cycle Technology Geothermai Resources Council,TRANSACTIONS,Vol.13,October 1989 to Geothermal Power Generation A.I.Kalina H.M.Leibowitz EXERGY INC. Abstract technology.It is not a single design but rather a family of new designs applicable over a wide 3,4TheKalinacycletechnologyisideallysuitedforrangeoftemperaturesanduses.(3-4), low-temperature,liquid-dominated sources that These designs normally feature a highlyarenowbeingservedbybinaryRankinecycle The technology focuses on structural changes to the design,high degrees of recupera- tion,and the use of working fluid mixtures.As a result,output is often 50 percent greater than that of a comparable Rankine cycle plant. plants. A SMW plant design is presented,giving perform-ance,thermodynamic state points,and _heatexchangerdutycurves.Preliminary sizing of the plant's heat exchangers are presented as the initial step in establishing plant cost.Extrapo- lation to and comparison with the Heber ORC plant is also presented. A hybrid flash/Kalina plant temperatures. is shown for higher Introduction For geothermal source temperatures normally too low for flash steam designs (somewhere around 350°F),economics favor the use of an organic Rankine cycle,often referred to as the binary cycle.The additional cost of heat exchangers in the binary cycle is offset by the reduction inbrineconsumptionperkW_generated. thermodynamic effici- is superior to the flash temperatures,there are within the binary cycle While the binary cycle''s ency (kW/lb/hr of brine) steam cycle at lower inherent structural losses that keep its efficiency substantially lower than that achievable (based on thermodynamic Second Law principles).More advanced binary designs, such as the supercritical plant built at Heber,(!) have attempted to improve performance by operating with mixtures at supercritical pressures to reduce the mismatch between the brine and cycle working fluid.Stull.Heber's design only reaches approximately 50 percent{2)of its Second Law potential. There is another design approach for binary plants.This new approach embodies a metho-dology often referred to as the Kalina Cycle 605 recuperative cycle using a mixture of two fluids having substantially different boiling tempera- tures,typically water and ammonia.Other pairs are possible as well.Often the composition of the working fluid changes throughout the cycle.Recuperation is achieved by judicious selection of the mixture composition and usually a need to change composition from one part of the cycle toanother,e.g.boiler vs.condenser.Operating pressures are kept subcritical as a maximum and above atmospheric as a minimum. In the design that follows,a geothermal plant is shown to operate at a Second Law efficiency near 70 percent..This is approximately 40 percent better than the Heber binary design. i 12.(K Based on a brine inlet temperature of 367°F,a flowrate of 440,000 lb/hr,and reinjection temperature of 170°F,the design of a SMW KCS12 plant is established and presented in Figure 1.The accompanying heat and mass balance state points are presented in Table 1. The selection of the working fluid composition is crucial to this design.It was chosen at .83 (by weight of NH3/H20)so that the dew point temperature at the turbine exit (point 36,90.9 psia) is higher than the bubble point of the oncoming fluid entering the evaporator (point 21,432.4 psia).This results in a high degree of recuper- ation,i.e.all liquid preheat and 33 percent of the vaporization duty in heat exchangers HE-2 and HE-4,respectively,is achieved recuperatively. The cycle design is shown in temperature enthalpy coordinates in Figure 2. Heat acquisition to the working fluid occurs between points 21 and 30.A substantial portion of this heat is provided by the turbine exhaust.The heat between points 36 and 38 is used to vaporize a portion of the working fluid between points 66 and 60.The heat in the turbine exhaust between points 38 and 29 is used to preheat the oncoming os Kalina KCS12 Conceptual Flow Diagram j5! | 3}2 s Ise !!1!|He ?7 {{{none |I t }J r : ze J }Bei oare --L-1 i sey 53 136 I | |He-5 i ] a ein LSS63!i oi) j | i |He-3 14 ME=4 ! bahBlangopoe2!-_-r tal pate ryVy|{We-2]1! 21i...izsi | i |HE-1 ! I J ! LEGEND -------:working selution ---a Beine ---a---Cooling water Figure 1 liquid from point 21 to point 60.In total,the heattransferredtotheplantis850.0 Btu/lb of workingfluid.Of this,323.6 Btuflb,or 38 percent,isprovidedbydirectrecuperation. The plant's operation is straightforward.Brine atpoint1issplitintotwostreams,§and 6,where itentersthesuperheaterand_reheater,respectively.The streams recombine at point 2 and pass througha_vaporizer/superheater,HE-5,and then vaporizerHE-3.At the outlet of HE-3,the brine has beencooledtoitsminimumtemperatureof170°F,where it is reinjected back to ground at point 4, 606 On the process side,the working fluid leaves the condenser,HE-l,is pumped to the evaporatorpressureof432psia,and then passes through thepreheaterHE-2 and evaporators HE-3 and HE-S. The working fluid is superheated to 352°F at point25,is expanded through the high-pressure turbinedownto232psiaatpoint26,and is then reheated to352°F at point 30.From there,it is expanded in the low-pressure turbine ¢o 90.9 psia at point 36,having a temperature of 222.2°F (near Saturation).The heat remaining in the exhaust is used recuperatively in HE-4 and HE-2 to vaporize andpreheattheoncomingliquid.At point 29,havingfulfilleditsrecuperationmission,the workingfluidisfullycondensedthroughHE-1. TABLE 1 : Thermodynamic State Points Pressure Temperanre _-_Enthalpy Flow/ Point (psia)Composition "F (Buw/lb)Flow 25 1 Brine 367.00 -2.6269 2 -Brine 333.96 -2.6269 3 -Brine 222.26 -2.6269 4 -Brine "170,22 -2.6269 5 -Brine 367.00 -9851 6 -Brine 367.00 -1.6418 7 -Brine 333.96 -9851 8 -Brine 333.96 -1.6418 9 -Brine 170.00 -2.6269 14 89.30 0.8305 60.00 20.33 1.0000 21 432.44 0.8305 60.00 18.78 1.0000 23 -Water $3.00 -16.8761 24 -Water 78.07 -16.8761 25 402.44 0.8305 352.00 776.80 1.0000 26 232.20 0.8305 273.78 736.73 1.0000 2 89.60 0.8305 121.93 402.82 1.0000 30 227.20 0.8305 352.00 792.06 1.0000 36 90.90 0.8305 222.26 726.46 1.0000 38 89.90 0.8305 170.00 519.86 1.0000 60 422.44 0.8305 165.00 98.25 1.0000 61 422.44 0.8305 165.00 98.25 4029 62 422.44 0.8305 165.00 98.25 5971 63 412.44 0.8305 217.26 444,29 4029 64 412.44 0.8305 217.26 444,29 5971 66 412.44 0.8305 217.26 444,29 1.0000 68 407.44 0.8305 307.75 743.60 1.0000 oF eee {25,80.ee KCS12 Temperature vs.Enthalpy 68 Loa re2s7”|L536 200 be'a a!Lis 130 ZC”Recup./KK Boiling'00 V =x 'Recup.Preheating 5 pal}a |{°eo dee os Jon qua 0d Guo too 4090 h Bub FIGURE 2 aot Performance Using a brine flowrate of 440,000 Ib/nr on a 60°Fday(53°F cooling water),the plant's net output(not including brine pumping or reinjectionpower)is 4961 kW.The plant's thermal (FirstLaw)and thermodynamic (Second Law)effici-encies are 19.2 percent and 69.7 percent,respectively.This corresponds to 88.7 Ib/kWh ofbrineconsumption.A summary of the plant'sperformanceispresentedinTable2. TABLE 2 SMW KCS12 Performance Summary (S3F Cooling Water) Geothermal Fluid Weight Flow 440,000 Ibs/hr Working Fluid Weight Fiow at 25 167,500 Ibs/hr Heat Input From Brine 528 Btu/lb Turbine New Output 5056 kw Pump Power 95 kW Net Power Output 4961 kW NET THERMAL EFFICIENCY 19.2% Second Law Efficiency Limit 27.5% Second Law Efficiency 69.7% Specific Brine Consumption 88.7 lb/kWh KCS12_vs._§itical Bi The SMW KCS12 design was extrapolated to 70MW gross output and its performance was compared to that of the Heber plant'2),Slight adjustments weremadetoassessperformanceatthesame_sourcetemperatureandcoolingwatertemperature,367°F and 65°F,respectively.The comparison is pre- sented in Table 3. TABLE 3 KCS12 vs.Supercritical Binary ORC SupercriticalKCS12ORC Dual Flash Gross Power Output (kW)70,000 70,000 70,000 Power Cycle Output (kW)68,500 59,200 70,000 Net Power Output (kW)57,490 46,600 63,300 Heat Source Temperature (F)367 367 367 Cooling Water Temperature (F)65 65 65 Brine Flow Rate (mm {b/hr)6.6 x 106 7.4%10 10.9 x 10 Cooling Water Flow (mm lb/hr)45.8 x 10 67.1 x 10 68.6 x 10 Cooling Water Pump Power (kW)2,030 3,000 3,070 Working Fluid Flow (mm lb/hr)2.710 7.65 x 10 134%10 Working Fluid Pump Power (kW)1,460 10,800 : .- Brine Pump Power (kW)5,150 7,600 2,630 Miscellaneous Parasitics (kW)2,370 2,000 1,000 Boiler Duty (mm Btu/hr)1349 x 10 1546 x 10 -- Power Cycle Efficiency (%)17.3 13.1 -- Plant Efficiency (%)14.5 10.3 - Specific Brine Flow (Ib/nr-kW)114.8 158.7 172.3 607 Kalina On a net basis,the output of KCS12 is 40 percent better than the supercritical ORC.This is evident in a comparison of the plant's thermal (First Law) efficiency and specific brine flow (Ib/kWh).A significant portion of the improvement is due to seven-fold difference in working fluid pumping losses,10.8MW vs.1.46MW.This is directly attn- butable to the difference in working fluid flow rate (7.7 million Ib/hr vs.2.7 million Ib/hr)and pump pressure rise (S00 psia vs.330 psia). Hybrid FlashSteam/KCS12 For higher temperature sources,where double flash steam is more economic than binary,the KCS12 plant may be integrated with the flash steam plant to produce a hybrid plant that is more economical than either the flash or KCS12 designs would be by themselves. In a double flash plant,some portion,typically 5 to 20 percent,of the brine flashes to steam during its delivery from the well bore to the power plant. This steam is then passed through a separator and expanded directly in a turbine down to condensingpressure.The unflashed fluid is then throttled(flashed)to generate an additional amount of steam,typically half the amount initially entering the plant.The steam from the second flash is admitted to the low-pressure section of the turbine where it,too,expands down to condensingpressure.The remaining unflashed liquid, approximately 70 to 80 percent of that entering the plant,is reinjected back to ground.Typically, flash plants with source temperatures of 350°F to 400°F require 120 to 200 Ib/kWh of brine con- sumption..See Figure 3A. As an alterative,the KCS12 plant is substituted for the second flash process as shown in Figure 3B.In so doing,the destruction of thermodynamic availability (exergy)by throttling down to low pressure in the second flash tank and subsequent rejection of the hot liquid brine is substantially reduced. For the purpose of comparison,it is assumed that the brine enters the hybrid plant at 367°F with a quality of 10 percent.The 10 percent vapor is expanded to condensing pressure in the usual steam plant manner.The 90 percent unflashed brine is then delivered to the KCS12 evaporator at 367°F.As was shown in Table 2,this design consumes 88.7 Ib/kWh of brine.Considering only 0.9 of the brine is used in the KCS12 portion,the actual consumption per unit of brine entering the plant is 98.5 !b/kWh. On the other hand,if the 367°F brine is flashed in a second step at 17.2 psia/220°F,an additional 14 percent of steam is produced (based on geofluid entering Flash No.1).Condensing down to 3 inches Hg absolute at a theoretical steam rate of 21.49 Ib/kWh yields .00546 kW per Ib/hr of geofluid.This corresponds to 183.2 Ib/kWh.The net effect of substituting KCS12 for the second flash state is a reduction in brine consumption from 183.2 Ib/kWh to 98.5 Ib/kWh.oi Kalina Cooling|Water i Figure 3A .in .DOUBLE FLASH STEAM PLANT 3.8 in Hg abs G=-2.1 heli35.7 --er or G=8.14167psianels4 |367 F Lan SEPARATOR 17.2 psta |223 F pa SEPARATOR G=8.93 h=339.7 G=28.76 ,(a)ho188.2 |A G=!.8 |367 F 1 Notes nh:Btu/lb G:flo atiq7masswoP Figure 38 al A HYBRID REHEAT FLASH STEAM 7 KCS12 PLANT r-%i rae to Serltr G=8,5 ne332-? ries FvAes RECUPERATOR/PREHEATER 167 peta Sorktr mae Cooling Water sey er]<CONDENSER78F af Geometry for each heat exchanger was initially The premium paid to achieve the higher output ofKCS12isheatexchangersurface.To assess this premium,surface areas were calculated usingempiricalheattransfercorrelationsoftwo-phase mixtures in a model developed by Exergyspecificallyforwater/ammonia mixtures. 608 estimated.Based on the assumed configuration, the pressure drops on the shell and tube sides werecalculatedandcomparedwiththoseallowable. When the pressure drops complied with design values,the surface areas were calculated for thesegeometries.A summary of the heat exchangers ispresentedinTable4.The heat duty vs.tempera- Kalina ture protile tor each of the heat exchangers is ospresented in Figures 4 through 10.Because the HE-1 (Condenser) profiles are often curved,typical of mixtures,the 3s 1modeldividesthedutyintotensectionsforL.accurate measurement of the mean temperature a"4differences.- 1s ® . =]asInall,there are 41,400 ft2 of surface area tequired 2 vo for the 4.96MW plant,of which 27,700 ft2 are for sl 8sheatacquisitionandrecuperation.All exchangers a *A ° are conventional shell and tube and,because all &|73 aa -- are in contact with liquid on one side or both,all a ----r"tubes are unfinned.The material for each is plain ss _-_-< carbon steel.According to (5),the cost of the heat -acquisition/recuperation surface is $339,000 based 5s on $12/ft2 for material and 50 man hours per Total Heat Duty 71.3 MBtu/nor10,000 ft2 for installation.Based on 4700 kW of KCS12 output,the specific cost of the additional FIGURE 4 surface is $72/kW. TABLE4 KCS12 Heat Exchanger Summary :HE-2 (Liquid Preheater) U |Pressure Drop (psi)Dury rv Area is aHeatExchangerShellTube(million Btu/fhr)-hr-sq.ft.-"F)(sq.ft.)col ise al Ea 1 -Condenser 0.05 123 71.3 370 13,700 -oa 2 Le a2-Liquid Prebeater 0.06 ..5qui2.1 19.2 260 3,350 5 138 =i 3 -Vaporizer 1 0.63 «4.9 28.3 460 4,600 »9 "lie _4 -Recuperative 024 4.4 36.8 430 6,400 a]UaVaporizeriS"A |Cl sa5-Vaporizer 2 1.08 4.3 48.4 420 8,150 =py | 6-Superheaer 2.21 0.7 $.7 110 2.750 78 *Re;|7 -Reneater 3.87 4.1 9.5 1 .*2.450 Totai Heat Duty 19.2 MBtu/ar 41.400 IGURE 5 Conditions Brine flow#440E3 lb/hrBrineinlet=367°F wo.fue .Brine outiet =170°F aes RE-3 (Vaporizer) Coolingwater=65°F pets <1 In a double flash plant,where a total installed cost 'olees |a of $2,000/kW is assumed,the cost of the resource is a {a4 VA typically 25 percent of the total plant,or S|ies L.$500/kW5),This,of course,varies with the depth =Faofthewellbore.At a 33 percent reduction in 2 7” specific brine flow (115 vs.172 Ib/kWh),the =}'*aresourcesizecanbereducedbyone-third,with a 2 -commensurate savings of $167/kKW.The result is a 175 a net savings of $95/kW for KCS12.Although this is -far short of a comprehensive economic analysis,it 16s does suggest that the additional heat exchang. surface is more than offset by the savings in the Total Heat Duty 25.3 MBtu/nr development of the resource.FIGURE 6 609 Kalina HE-4 (Recuperative Vaporizer) ees aausTol ="|4asa |ees w a 5 1398 as 5]tes wsSg|Lt ois mine iss - Lf Total Heat Duty 36.2 MBtu/hr FIGURE 7 HE-5 (Vaporizer 2)368 a |328 Gq ¢c sae LO " :A Slee a a a.i u } Olece . =| @ f2eesA ; 228 |1I!{ Tetal Heat Duty 48.4 MBtu/her FIGURE @ HE-6 (Suserheater)378 ||uA sca .a _i |"| te 7 a frai -|ase =ao S|ee : o a ai Ess} Ulises g Pa&328&i a sin Total Heat Duty 5.7 M8tu/hr FIGURE 9 610 HE-7 (Reheater) i ]|36s i to T en ass (iN335 b 323 a Temperature275 Pia Total Heat Duty 9.5 MBtu/hr FIGURE 10 Turbi Selecti The turbine design for a water/ammonia cycle differs significantly from one specified for an organic Rankine (binary)cycle.The molecular weight of ammonia (17.03)is almost identical to that of water (18).As a result,the ammonia/water turbine's blading,passage heights and diameters are the same as that specified for conventional steam turbines.On the other hand,ORC turbines operating with hydrocarbons such as_isobutane (C4H10)or chloro-fluorocarbon refrigerants,¢.g. R113,R114,are substantially different in geometry due to their much higher molecular weight than ammonia or water.The molecular weight has direct bearing on the sonic velocity which,in turn,dictates the relationship between the fluid speed to blade speed.Further,these hydrocarbon fluids have relatively low enthalpy drops compared to ammonia/water and therefore need to circulate a much greater volume of fluid for the same power output.Thus,the ORC turbine's size is much larger than an ammonia/water turbine. This is also why pumping parasitic losses are much lower with ammonia/water. Finally,while the KCS12 turbine enjoys the convenience of using conventional steam turbine design and manufacturing practice,it does not suffer the downside that penalizes condensing applications such as with flash plants.Rather,the KCS12 turbine's discharge of 95 psia_totally eliminates the need for the expensive,large volume condensing stages.Low exhaust kinetic leaving losses are incurred.The exhaust is also dry,meaning that no wetness losses or erosion damage occurs. It is envisioned that the SMW turbine for the KCS12 plant will be an axial,back-pressure design consisting of three or four high-pressure and a similar quantity of low-pressure stages rotating on a common shaft at approximately 7500 rpm.As output and volume flow increase,the shaft speed will decrease to synchronous speed (3600 rpm or 1800 rpm)where no gear reducer is required.os (aterial Select A comprehensive chemical stability and corrosion test.program was conducted?)to identify materials that are suitable for ammonia/water duty.Plain carbon steel (A106B)and T22 alloy (2.25 Cr,1 Mo) were evaluated at 200°F and S00°F,respectively,for an exposure period of 720 hours.No evidence of decomposition was found,and corrosion levels less than .0002 inches (0.2 mils)per year weremeasured,Based on this,all heat exchangers shown in KCS12 are specified with A106B plain carbon steel. Conclusions The application of the Kalina Cycle technology for low-temperature geothermal sources provides significant improvement in output over conven- tional binary ORC and flash steam designs. Preliminary cost estimates based on heat exchange surface requirements indicate that the premium paid for additional surface is more than offset by the reduction in resource requirements and balance of plant. The KCS12 turbine specification is of standard No vacuum condens- Standard equipment and the plant. back-pressure steam design. ing stages are required. materials are used throughout From the standpoint of process design,equipment and material selection,the KCS12 design contains virtually no technological risk.Overall,it contains less risk than the supercritical binary ORC approach. 611 Kalina References 1)Heber Geothermal Binary Demonstration Plant:Design,Construction and Early Startup, Electric Power Research Institute,October 1987,AP-5146. (2)See Ref.1.p.4-56. (3)Kalina,A.,and Leibowitz,H.,Applying Kalina Technology to a Bottoming Cycle for Utility Combined Cycles,ASME 87-GT-35,Anaheim, California,June 1987. (4)Kalina,A.,Kalina Cycle Technology Applied to Direct-Fired Power Plants,Joint Power Conference,Dallas,Texas,October 1989 (to be published). a (5)Page,J.S..Conceptual Cost Estimating Manual, Gulf Publishing Company,Houston,Texas, 1984, (5)DiPippo,R..Geothermal Energy as a Source of Electricity,DOE/RA/28320-1,USDOE Publish- ing,January 1980.. (7)Kalina,A.,and Leibowitz,H.,Off-Design Performance,Equipment Considerations and Material Selection for a Kalina System 6 Bottoming Cycle,Cogen UI Turbo Conference, Nice,France,August 1989 (to be published).os ECONOMIC PERFORMANCE OF GEOTHERMAL POWER PLANTS USING THE KALINA CYCLE TECHNOLOGY H.M. D.W. Leibowitz Markus EXERGY INC. Hayward, Abstract The economics of geothermal powcr using liquid- dominated resources in the 300°F to 350°F (149°C to 177°C)range is substantially improved using an ammonia/water Kalina cycle,designated as System 12 (KCS12).The best features of flash steam systems and the binary Rankine cycle are combined {o produce a plant design that is 40 percent less expensive per unit of installed capacity than current commercial binary plants. A plant design is presented for a 30MW unit.Plant costs are dcveloped using vendor quotations and factored estimates for construction and installation. Bascd on unit costs of capacity,i.e.S/kW,.project returns to the equity investor are presented. Esonomies of Evistines Svstems are Poor in Today's Power Marke! Mest liquid-dominated resources,as vet undeveloped.are at tempcratures equal to or below 250°F (177°C).In this range.both flash and binary organic Rankine cycles are not economic at current competitive electricity prices.e.g.$.05 to $.06 per KWh., A.las am Fiash stcam systems perform reasonably well at higher temperatures.say 40f°F (204°C)by virtue of their simplicity and low capital cost.Very little heat exchange equipment is required,except for the condenser,and conventional steam turbines are specified.These turbines.except for some biadetreatmenttoprotectagainstthesolidscarryoverin the stcam such as H2S,are identical to those that have been used in utility and industrial steam plants for the past century.In large sizes,these turbines sell for less than $200/kW.However,as the source temperature decreases,the production of steam per unit of brine decreases precipitously.Remember that the production of flashed steam is a function of the temperature difference between the sousee and flash temperature.not the absolute temperature of the source.For example.a 65 psia (4 bar)single flash plant consumcs more than three times the amount of brine at a 230°F (166°C)source temperature than one at 400°F (204°C). California B.Binary Rankine a The other compcting tcchnology that has been developed specifically for lower temperature sources suffers for different reasons.The thermodynamic process of transferring heat from the source to the organic (hydrocarbon or chlorofluorocarbon)working fluid is inefficient. Except for experimental supercritical plants operating with hydrocarbon mixtures,¢!) commercial binary plants employ a_single- component working fluid which is vaporized in a subcritical boiler.The result is a thermodynamic mismatch between the hot brine as it enters the evaporator and the much cooler working fluid leaving the evaporator.This is an irreversible thermodynamic loss that manifests iisclf as lower efficiency and higher brine consumption. Further,the hydrocarbons used in binary plants. such as pentane,impose a much different turbine specification.making them more expensive than conventional stcam turbines.There is a much smaller enthalpy drop during the expansion of hydrocarbons compared to steam.So,in order to produce the same amount of power,the hvdrocarbon mass flowrate must be increased proportionately.This makes the turbine very large. albeit with few stages of expansion.With such a departure from conventional steam turbine practice,relatively few vendors offer these machines and,accordingly.at a higher price.Alt present.commercial binary plants have turbines limited to SMW modules.The vast majority have one-megawatt modules.Building a plant with ten or more modules may improve on-line availability somewhat,but if certainly results in much higher capital cost.For example,twenty hydrocarbon turbines at one megawatt are three to five times more expensive per kilowatt than one twenty- megawatt steam turbine. Finally,hydrocarbons exhibit)poor heat transport propertics.Their specific heat is less than one-half of that of water.Thus,heat exchange surface is increased,further adding to cost. }ive:K 2 The design features of the Kalina Cycle System 12 (KCS12)were first reported in 1989¢2),It achieves a os Leibowitz/Markus thermodynamic efficiency (brine effectiveness) that is approximately 50%greater than binary Rankine plants while using standard steam turbines to produce a plant design that ts economically superior to either the flash or hydrocarbon binarydesignsforresourcesinthe300°F to 350°F (149°C to 177°C)range.The design of KCS12 ts shown in Figure 1,The working Mutd is a mixture of ammonia and water having a concentration of O.85 ammonia. rr| HPT,LPY BRINE |GENERATORfromproduction wells |HE-6 C HE?a Dy a HE-5 rr _¥--_{|HE-4 amMed,- HE-3 |r}a ito\'a reinjectlon a LweilsWauenOT! cooling water (7%scycre pump FIGURE 1} RCSi2 Plant Design Upon entering the pliant.the brine is split inte two Streams:one is used to superheat the working fluid vapor in HE-6 and the other to reheat the vapor in HE-7.After leaving these two exchangers.the brine streams are merged and then used for evaporation and preheat duty in HE-5 and HE-3.After leaving tne preheater.the brine is reinjected to sround.On the working fiuid side.the vapor i:condensed against cooling water in HE-1 and pumped to boiler iniet pressure.From there.the liquid ts preheated recuperatively in HE-2 and HE-4 and then on to the main boiler,HE-3.3 and 6. superheated state.the vapor is expanded through the high-pressure turbine stages.then reheated in HE-7 before entering the low-pressure turbine Stage.After compicting the second expansion.the saturated vapor enters the recuperative boiler,HE-<,. where it begins to condense.As the vapor condenses,its heat is given up to vaporize a stream of the oncoming working fluid. The features that distinguish KCSI2 from the flash and hydrocarbon binary Rankine plants are: After leaving HE-6 in a 1.Vari ilin ig The .85 ammonia/water mixture boils along a variable temperature process in a conventional subcritical boiler.Ata.pressure of 453 psia (31.2 bar),the working fluid begins to boil (bubble point)at t6S°F (74°C)and completes boiling (dew point)at 300°F (149°C).This produces a very good working «fluid/brine*match.See Figure 2. Thermodynamic losses are reduced. 160 Y 140 Brine , 2 =120 Em KCS!2 Evaporator 2 100 80 va 0 100 200 Heat Duty (MWip) FIGURE 2 Heat Acquisition 2.Highty Recurerative The two recuperative heat exchangers (HE-4 and HE-2:provide approximately 38 percent of the total nea:transferred to the working fluid.This improves the net brine effectiveness.i.c.Wh/kg. Only through the use of mixtures is it possibic to transfer heat from the turbine's exhaust at 134 psia (9.2 bar)te the oncoming working fluid at 453 psia (31.2 bar}.Even though the turbine exhaust pressure is lower than in the boiler,the temperature at which the exhaust vapor begins tocondense(dew point)is approximately 63°F (35°C) higher than the temperature at which the working fluid begins to boil,By contrast,the turbine exhaustinconventionalbinaryplantscannotbeusedfor bolting.The recuperation is limited to the smailamountsofsuperheatremainingintheexhaust. which may be used for minor liquid preheat duty. 43.Standard Steam Turbines The molecular weight of ammonia is very similar to that of water,17 vs.18.Thus,standard steam turbines may be used for ammonia/water duty.Molecular weight determines the fluid's sonicvelocitywhich.in turn.sets the blade heights and rotational speed.Exccpt for a zero leakage mechanical seal.the ammonia/water turbine is identical to conventional steam turbines.Furthermore.KCSi2 operates at above-one atmosphere at all times.This eliminates the need forthelarge.expensive condensing stages that are usec osned in all steam power plants,including flash geothermal.Erosion protection is also unnecessary because the exhaust is clean,dry saturated vapor. 4.64H xchanger The specific heat of ammonia/water mixtures is more than twice that of hydrocarbons or chlorofluorocarbons.,albeit)mixtures have lower conductances than pure components.Surface per unit of heat transferred is reduced proportionately. Carbon stecl is specificd throughout. The improvements described in !and 2 above result in superior thermodynamic performance.Net brine effectiveness for KCS12 is approximately 40 to 60 percent better than comparahie hydrocarbon binary Rankine plants.KCS12.performance is presented in Figure 3.The combined effect of improved performance and the ability to use a centrally located,conventional steam turbine and smal!heat exchanger surfaces (items 3 and 4)play a major role in reducing the plant's capital cost. 39 or as > =| 320:J '3 20 J = 2 10-; - | i |0 + 120 s%160 i$20 Resource Temperature 1°C) FIGURE 3 KCS12 Perfermance Capital Cost A study was conducted to estimate the installed capacity cost of KCSi!2 under the followingconditions: Site:Central Nevada Brine Inlet Temperature/Reinjection Temperature:330°F (166°C)/i 70°F (77°C) Brine Flowrate:4,000,000 Ib/hr (1.82 kg x 106/hr) Cooling Water Inlet Temperature:§5°F (13°C) Leibowitz/Markus Based on the above conditions,the KCS12 plant's performance is summarized below: Net Output of the Power Island:32.2MW Net Output Delivered to the Grid:25.5MW Working Fluid:.85 ammonia/water Turbine Inlet:435 psia (30 bar)/315°F (157°C) Turbine Exhaust:10 psia (7.6 bar/220°F (l0s°C) Based on the conditions cited above and heat exchanger specifications shown in Table 7,an estimate of equipment and construction costs was Amade.A plot plan is shown in Figure 4. Aajor i Cost (S000) Heat Exchangers §,260 Vessels and Tanks 620 ' Pumps 2.050 Turbine Generator 450 Subtotal 14,380 Construction Cooling Tower 3.600 Piping 3.200 Power and Lighting 2.300 Foundations 1.000 Structures 1,100 Buildings 330 Instruments 1,000 Insulation :760 Miscellaneous Ria) Subtotal 14,140 Engineering and Home Office 2.600 Field Labor and Indirects 3.000 Subtotal 6600 Total 38,120 Resource development*LS,.000 Total In-Ground Costs $3,120 Legal and Project Fees @ 3%1,600 Total Project Cost $54,726 Net Power to Grid 23,500kW Capacity Cost $2146/KW *Estimate by Calpine Corporation. 2¥i ;Ki j ¥Sis To demonstrate the bencfit of the KCS12 from the investor's perspective,a simple cash fiow analysis was performed comparing the KCSi2 to the binary Rankine cycle (BRC).Based on published(3.4)data for commercial installations,the capacity cost of saleable net power for a BRC was estimated to be $3800/kW.os Leibowitz/Markus Heat Exchanger aNWheTable J Summary of KCS12 Heat Exchangers Duty 539 (157.9) 144 (42.2) 253 (74.1) 198 (58.0) 123 (36.0) 194 (56.8) 83 (24.3)=I)10%Brofir (MWind toOQoo_tn=t2t2babeoobto&ooootefwa©):pO__..D=NC)ilii©OOO},()TSASEESSI.|AOOOO|ACTESS ROAD A.1yodology.an The identical model was run for two plants,a KCS12 and a BRC,each costing $60 million. estimated from was assumed cach Thus, plant was the KCS1i2 based on an underlying cost Assumptions of $2150/kW, The output of the per-kW to produce 27.9MW whereas FIGURE 4 KCSi2 Plot Plan All other assumptions were held both plants so that even if one or more of individual assumptions is not particular Price. the BRC delivered I5.8MW using a cost of $3800/AW.eewoawnNe®Wnbetepepetnnewneo%Sseeproject.the two technologies should Ae si r cooling water §.0 (34) brine 19)3.80 (.26) brinc brine brine BRINE HOLDING POND BRINE DUMP EXHAUST CHAMBER BRINE DUMP EXHAUST CHAMBER VALVE PIT FIRE WATER STORAGE TANK FIPE PUMP SKID POND WATER POMPS SOLIDS SEPARATORS COOLING ICWER STAIRWELLS AQUA AMMONIA TRANSFER CONDENSATE AUX.DRUM CONDENSATE DRUM ACTA AMMONTA CYCLE PUMFS OUTLET SOMPS AND SCREEN STRUCTURES COOLING WATER PUMPS FINAL CONDENSERS PRE-CONDENSERS (ECONOMIZER BRINE PRE-REATERS VAPORICER/SUPERAZATER VAPORIZERS K.¢.DRUM REHEATERS TURBINE GENERATOR BRINE INJECTION POMPS PRE-REATEPS BATTERY ROCM CONTRCL ROOM 7 COOLING TOWER UNIT AUX.TRANSFORMER UNIT TRANSFORMER GENEPATOR TRANSFORMER LINE DISCONNECTS CIRCTIT BREAKERS remain valid. Ss: constant representative relative comparison os Major assumptions: «Sales price of energy:5.5¢/kWh «Annual utilization:7800 hours «Operating costs:0O.5¢/kWh *Debt ratio:85%of combined plant and and resource cost *Debt repayment:Straight line amortization +Interest rate:12% «Plant life:30 years +Insurance:1%of power train «Property tax:1%of power train and resource *Tax depreciation:Straight line *Tax benefits:Used as incurred *Development period:One year *Resource acquisition costs and transmission lines:Not included *Technology licensing fees:Not included It is worthwhile noting that the tax depreciation assumption is very conservative.Under the appropriate circumstances.U.S.regulations maypermitdepreciationoveramuchshorterlife,whichwouldgeneratesubstantialtaxbenefitsfora qualified investor. B.Results 1.Inzernal Rate of Return The impact of the much lower cost per kW for the KCS12 is a dramatically higher return. Whereas the BRC plant .generates an,after-tax internal rate of return of only 7%,the KCS12 yields 22%.Driving these results is the fact that the two piants have almost identicai cost structures,but theC512produces77%more revenue.Assuming a I5% investment threshole.the BRC plant described in this example would not be built. 2.Cumulative ash Flows The comparison plants are of identical total cost so that the absoiute cash flows can be compared. in both cases.the 15%initial equity investment plus interest during the one-vear development period results in an initiagi $11.1 million cash outiay at the time of plant operation.In contrast to the KCS12, which generates positive cash flow in the first year, the BRC does not have a positive cash flow until the eighth vear of operation.Over the estimated 30- vear life of the two projects,the KCS12 vields net after-lax cask flow of $191 million versus only $56 million for the BRC plant. a 3.ia ve Lenders to these projects are generally concerned that they have adequate security for the payment of principal and interest on their loan.One frequently used test is the ratio of a project'searningsbeforeinterestandtaxestotherequiredinterestpayment.A ratio of one means that there isexactlyenoughcashflowtopaytheinterest. Although a geothermal project with a power sale contract from a strong utility may be a relatively secure risk.it would be typical for a lender to require an interest coverage ratio of somewhat greater than one. Leibowitz/Markus In this example,the KCS12 has an_initial interest coverage ratio of 1.61,which is sufficiently high that lenders may be willing to increase the leverage on the project.Alternatively,the BRC has an interest coverage ratio of only 0.84.In this case, it is possible that the lender would not proceed with an 85%loan without additional security of some type. Cc Sensitivity Analysis The results presented above were tested for their sensitivity lo changes in some of the most important assumptions. 1.Sale Price The single most critical variable is the price at which electric power can be sold.The graph in Figure 5 (and the accompanying data points in Table 2)demonstrates the relationship between the internal rate of return and the sale price of power for both plants. If the cost of equity capital for these projects is assumed to be 15%,then the KCSi2 creates a viable investment alternative at a sales price of 4.5¢per kWh whereas the BRC requires a sales price of 7.5¢ per kWh to meet the same threshold.During the early 1980s,when public utilities were granting Standard Offer 04 (SO-4)power sales contracts,the energy sales price frequently was between 7¢and 9c per kWh.At these prices.the existing BRC technology offered an economically sound alternative for developing geothermal resources. Since the expiration of the SO-+contracts.sales prices have fallen.The KCS12 is one was to provides an adequate return i@ attract equity investment for geothermal development.RateofResuraNhfe}4lateral()¢r r 2 4 6 8 Cents/kWh -o-KCSI2 --e-BC FIGURE §& Internal Rate of Return vs. Electricity Sales Price af Leibowitz/Markus Table2 Data Points: Internal Rate of Return vs,Electricity Sales Price Sales Price (Cenis/k Wh)KeSst2 BRC 3.0¢5% 3.5¢8% 4.0¢12%0% 4.5¢15%3% 5.0¢18%5% §.5¢22%7% 6.0¢25%9% 6.5¢29%11% 7.0¢32%13% 7.5¢36%15% 8.0c 39%17%, 8.5¢42%19% 9.0c¢46%20% 9.5¢49%22% 10.0¢§2%24% 2.Cost per kW The costs of developing a resource and building a plant can vary over a wide range.Table 3containstheratesofreturnwhichresultifthecost per kW is varied while all other assumptions remainconstant.The percentage of the total cost allocated io development of the resource was unchanged.In the case of the KCS12,a 20%increase in the cost per KW to $2600 still yields a 16%return to the equity investor. Table3 Internal Rate of Return vs,Cos:nor KN Resie BRE SEW Return Siew Return $1,800 29 $2.506 9% 1,906 26%3.600 8% 2,000 24%3,790 8% =.100 23%3,800 7% 2.200 21%3,900 6 Se 2.300 296 €.000 6 Se 2.90 18%S.106 6% 2.506 17%=,200 3% 2.600 16%4.300 % 3.Leverage In general,the more debt the lender is willins to provide,the higher the return to the investor,Table 4 shows the impact on the internal rate of return of 10%increments in permissible leverage over the range of 90%to 50%. The KCS12 demonstrates the traditional relationship of a falling return as the leverage decreases.In the BRC case.the return on assets is approximately the same as the after-tax cost of debt.resulting in very little benefit from increasing leverage.Ac higher sales prices.where the return on asscis exceeds the cost of debt.the BRC would exhibit the typical characteristic of higher return with increasing leverage. Table4 Leverage vs.Internal Rate of Return Percentage Debt KCSI BRC 90% ° 25%1% 80%20%1% 70%17%1% 60%16%1% 50%15%1% The KCS12.offers an cconomically superior alternative.It improves thermodynamic efficiency and also lowers cost through the use of standard steam turbines.It is estimated that the cost per kW for the KCS12 is approximately 40%less than for a binary system.With this dramatic decrease,even al current clectricity prices,equity returns provided by the KCS12 are quite attractive,even at 20%over the estimated cost. Acknowledgements The authors wish to acknowledge the contributions made by Mr.Richard Pelletier of Exergy in thegenerationofthetechnicaldataandMr.WilliamThomasofCalpineCorporationinassistinginthe overall plant design. References i Heber Geothermal BRC Demonstration Pian:: nsir fo)n any an-Up.EPRI. AP-5146.October 1987. 'Kalina,AL.and Leibowitz,H.M..Application of the Kalina Cycle Technoiogy to Geothermai Power Generation.Geothermal Resources Council,Transactions Vol.13,October 1989. '33 Geothermal Resources Buyllctin.Voi.18.No.£ p.26.Net output =Rated outpur x 0.75. '*)Ram,H.,and Kreiger,Z..Innovative Geothermal Power Plants The Ormar Way,Gcothermal Resources Council.Transactions Vol.13.October 1989. (3)Nunez,M.G..BRC Cycle:Potential Exploitation of the Residual Brine at Cerro Prieto,Gcothermal! Resources Council,Transactions Vol.12,October 1988. (6)Private communication with Mr.William Thomas of Calpine Corporation,March 1990.