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Home My WebLink About2017 ORC Published ArticleAn Alaska case study: Organic Rankine cycle technology Ben Loeffler, and Erin Whitney Citation: Journal of Renewable and Sustainable Energy 9, 061707 (2017); View online: https://doi.org/10.1063/1.4986583 View Table of Contents: http://aip.scitation.org/toc/rse/9/6 Published by the American Institute of Physics Articles you may be interested in An Alaska case study: Solar photovoltaic technology in remote microgrids Journal of Renewable and Sustainable Energy 9, 061704 (2017); 10.1063/1.4986577 An Alaska case study: Energy storage technologies Journal of Renewable and Sustainable Energy 9, 061708 (2017); 10.1063/1.4986580 Wind power project size and component costs: An Alaska case study Journal of Renewable and Sustainable Energy 9, 061703 (2017); 10.1063/1.4986579 An Alaska case study: Biomass technology Journal of Renewable and Sustainable Energy 9, 061705 (2017); 10.1063/1.4986578 An Alaska case study: Diesel generator technologies Journal of Renewable and Sustainable Energy 9, 061701 (2017); 10.1063/1.4986585 Heat pump technology: An Alaska case study Journal of Renewable and Sustainable Energy 9, 061706 (2017); 10.1063/1.4986584 An Alaska case study: Organic Rankine cycle technology Ben Loeffler and Erin Whitney Alaska Center for Energy and Power, University of Alaska Fairbanks, P.O. Box 755910, Fairbanks, Alaska 99775-5910, USA (Received 6 June 2017; accepted 26 September 2017; published online 21 December 2017) Organic Rankine cycle (ORC) technology is mature for larger-scale power generation, but ORC systems appropriate for smaller-capacity generators, typical of Alaska vil- lage and other Arctic community power plants, are still new to the market or in the prototype phase. Many villages are being approached by product developers to invest in this new technology, and there is a signiﬁcant value in the dissemination of the real world performance and costs of existing systems. In this analysis of ORC installations across Alaska, capacity factors ranged from 33% to 52%. Low utilization levels are attributed to insufﬁcient waste heat resources (in Unalaska and Cordova) and to higher than expected maintenance costs in a prototype pre-commercial model (in Tok). Signiﬁcant annual fuel savings have been realized for each installation, with annual demonstrated savings of $70000 in Unalaska and projected annual savings of over $300000 in Cordova. Modifying existing generation for an ORC system has proven to be challenging and expensive. Project cost data indicate that Alaska projects should expect total capital expenditures to be two to three times the cost of the ORC unit itself. Some systems have been highly reliable and cost-effective, while other installa- tions have been neither. The most cost effective ORC system may be best imple- mented with a ground-up new generator design and install. Of the installations in Alaska, only the Unalaska Green Machines have achieved reliable operation beyond a few weeks. The smallest reliable system, which operates in Unalaska, has a 50kW nameplate capacity and requires 500kW of waste heat, indicating that this technology is best suited for communities with 1MW or more of diesel generation.Published by AIP Publishing.https://doi.org/10.1063/1.4986583 INTRODUCTION Diesel generators are the main source of electrical generation in remote Alaska communi- ties. The best diesel generator systems convert roughly 40% of the diesel fuel energy content into electricity, with the rest of the fuel energy converted to heat. This heat, if not captured by heat recovery devices, is lost to the atmosphere through the exhaust and cooling systems. The most efﬁcient use of waste heat is for direct heating of adjacent building spaces or domestic water. When such a direct use of engine waste heat is precluded by geographic or infrastructure constraints, this heat energy can be used to generate additional electricity through Organic Rankine Cycle (ORC) technology. The Rankine cycle is a thermodynamic cycle that converts heat into mechanical work, such as spinning an electrical generator. An organic Rankine cycle uses an organic ﬂuid with a boil- ing point lower than that of water to convert waste heat from the cooling jackets and exhaust stacks of generators into electricity. The ORC is utilized as a waste heat to power (WHP) system to generate electricity that is supplied to the grid. This study evaluated four ORC units imple- mented in communities in Alaska. The potential for waste heat recovery through a Rankine cycle is dependent on the temper- ature of the waste heat source. Exhaust stack gases can reach high temperatures (over 1000 F), while cooling jacket water is a lower temperature (as low as 165 F). Cooling jacket water is an appealing waste heat source, as an ORC can often be plumbed with the engine’s existing cool- ant lines. Exhaust stack heat recovery offers the potential for higher ORC ﬂuid temperatures 1941-7012/2017/9(6)/061707/10/$30.00 Published by AIP Publishing.9, 061707-1 JOURNAL OF RENEWABLE AND SUSTAINABLE ENERGY 9, 061707 (2017) (300 F or more) and increased ORC efﬁciencies but requires the additional capital costs of adding a heat exchanger to the engine’s exhaust system. In addition, the presence of the exhaust heat exchanger can change the exhaust gas composition and may not be compatible with emis- sion controls. Working ﬂuid choices can affect the operating efﬁciency of the ORC unit. All ORC units in Alaska use either R-245fa (pentaﬂuoropropane) or ammonia as the working ﬂuid. Other proven working ﬂuids include pentane, propane, CO2, benzene, toluene, and p-Xylene. Polar molecules such as water, ammonia, and ethanol (due to strong hydrogen bonds) are not the most appropriate working ﬂuids due to larger vaporizing enthalpy (Liu et al., 2004). Organic Rankine cycle working ﬂuids should also have high decomposition temperatures and high criti- cal and condensing temperatures and be chosen to work within the temperature range of avail- able waste heat and cold resources (Bourji et al., 2010). ORC system manufacturers select working ﬂuids based on anticipated waste heat temperatures and hardware compatibility. The goal of adding ORC products to an existing generator system is to convert some waste heat into additional electricity generation, increasing the overall generating efﬁciency of the power plant. While ORC technology is mature for larger-scale power generation, ORC systems appropriate for smaller-capacity generators typical of Alaska village and other Arctic commu- nity power plants are still new to the market or in the prototype phase. Many villages are being approached by product developers to invest in this new technology, and there is signiﬁcant value in the dissemination of the real world performance and costs of existing systems. This review of ORC technology in Alaska is a result of Alaska Senate Bill (SB) 138. In this bill, the Alaska State Legislature created an uncodiﬁed section of law entitled: “Plan and Recommendations to the Legislature on Infrastructure Needed to Deliver Affordable Energy of the State to Areas That Do Not Have Direct Access to a [proposed] North Slope Natural Gas Pipeline.” To support the Alaska Energy Authority (AEA) in its development of an Alaska Affordable Energy Strategy, the Alaska Center for Energy and Power (ACEP) contracted with AEA to document technology development needs speciﬁc to Alaska with regard to renewable and sustainable energy technologies. The intention was to identify targeted energy technology development solutions than can be implemented in Alaska to make energy more affordable in the Alaska Affordable Energy Study area. While the focus was on technology research solu- tions, other factors such as logistics, labor, and training were also addressed. Drafts of technol- ogy reviews were vetted by expert roundtables in late February and early March 2016. These reviews are not meant to be exhaustive discussions of energy technologies in Alaska or proper designs for each technology, and they should not be used as guides for the choice and installation of speciﬁc systems. As such, not all possible issues with power production and each technology are addressed. Data for each technology were collected from surveys and pub- lically available databases. Only projects with clearly reported or projected data were included in each technology analysis. These distinctions and descriptions of data sources are included in each technology review. METHODS Alaska ORC installations This paper evaluates four ORC generator systems that have been or are being installed in different parts of Alaska. Each system is evaluated based on the publically available cost and performance data. A summary of the installations is shown in Table I. In Cordova, a Renewable Energy Fund (REF) grant enabled the installation of a new 3.6MW diesel generator and a dedicated ORC waste-heat recovery system. The installation was completed in March 2013, and the generator and the ORC system ran for approximately 2months before being shut down for economic reasons. The diesel generator is too often supplanted by hydroelec- tric generation, and the air coil cooling tower design for the ORC proved to be insufﬁcient (Cordova Electric Cooperative, 2008a,b,c). In Unalaska, three ElectraTherm 4200 50kW stand-alone ORC modules were installed to capture waste heat off three of the powerhouse’s diesel generators. The city considered the 061707-2 B. Loeffler and E. Whitney J. Renewable Sustainable Energy 9, 061707 (2017) ORC systems of more than a dozen manufacturers before selecting the ElectraTherm units. The Unalaska ORC installation was completed in October 2014, and the units are still in operation, requiring only routine maintenance. As of March 2016, the ORC system has offset 44501 gal- lons of fuel usage, saving the city $101686. Kotzebue recently completed the installation of a waste-heat recovery system to use waste heat from the exhaust stack of its largest generator. The system is being installed simulta- neously with district heating upgrades and a new absorption chiller system that produces ice for the local ﬁshing industry. The Kotzebue ORC system has not yet been commissioned. The ORC system in Tok was initially installed at the ACEP Power Systems Integration Laboratory for testing. The system was then moved to the Tok power plant, where it ran contin- uously from October 2, 2013, to November 19, 2013, when an expander failure shut down the system. The manufacturer stated that it was aware of the problem and implemented design and lubricant changes in subsequent models. In Tok, the ORC expander was not rebuilt, and the system was and remains bypassed. ANALYSIS Utilizing available data and projections, each of the four Alaska ORC installations consid- ered in the report were analyzed for system performance, capital and O&M costs, and economic impact. Capacity factor Every energy system is expected to perform below peak capacity in the real world. The capacity factor is deﬁned as the actual ORC system electrical output as a percentage of the system nameplate capacity. The Kotzebue application projects a capacity factor of 96%, but the real- world performance of the other three systems indicates that 30%–50% is a more realistic expecta- tion. Table II shows the demonstrated power, energy output, run time, and capacity factor of the ORC systems in Alaska. The estimated values are in italics. Capital costs and operation and maintenance costs The capital costs for each installation were calculated for both nameplate and demonstrated average power outputs. Capital costs represent the total “overnight” expenses incurred prior to the ﬁrst production of electricity. The annual operation and maintenance (O&M) costs were cal- culated based on the nameplate and demonstrated annual energy output. The Cordova installation coincided with a new diesel generator installation, and the Kotzebue installation coincides with a new absorption chiller and district heating loop installa- tion. To the extent possible, the ORC system costs were isolated from the total project costs for Cordova and Kotzebue. TABLE I. Summary of Alaska ORC installations. Installation location Manufacturer Model Heat source Cold source Nameplate capacity (kW) Number units Total capacity (kW) Cordova Pratt and Whitney PureCycle 280 Cooling jacket Air coil 260 1 260 Kotzebue Energy Concepts a Ammonia Power Cycle Exhaust stack City water and air cooler 162 1 162 Unalaska ElectraTherm Green Machine Cooling jacket Sea water 50 3 150 Tok ElectraTherm Green Machine Block 1 b Cooling jacket Well water 50 1 50 aKotzebue Renewable Energy Fund (REF) application data are for an Energy Concepts ORC, but a General Electric brand system was actually purchased. bBlock 1 machine was a prototype, pre-commercial model. 061707-3 B. Loeffler and E. Whitney J. Renewable Sustainable Energy 9, 061707 (2017) Table III compiles the system total capital and O&M costs on a nameplate and actual per- formance basis. The nameplate ﬁgure represents the system running at nameplate capacity 363days a year (2days ofﬂine for maintenance). Estimated and projected ﬁgures are identiﬁed in Table III in italics. The data from Table III are plotted in Fig.1 for comparison. The nameplate quantities are represented with triangles, and the demonstrated quantities are represented with circles. The quantities for each installation are connected by color-coded lines. A 2015 report from Oak Ridge National Labs (ORNL) (Elson et al., 2015) predicts an installed cost for ORC systems between 50 and 500kW capacity of 4500 $/kW. ElectraTherm quotes turnkey prices for three of their ORC modules ranging from 35kW to 110kW. In Fig.2, the capital costs of the Alaska installations are plotted with the ORNL and ElectraTherm values for comparison. Installed costs by major components Capital costs were compared on a per-kilowatt nameplate basis and broken into categories of ORC units, materials, labor, shipping, and other costs. In Table IV, the nameplate capital costs of each project category are compiled. The ORC unit itself accounted for 34%–53% of the total capital costs, indicating that projects in Alaska should expect total capital expenditures to be two to three times the cost of the ORC unit itself. Capital costs per kW are graphed in Fig.3. Kotzebue’s numbers are based on expected costs and performance from their REF appli- cation, with actual installed costs expected to be higher and actual performance expected to be lower. TABLE II. Summary of ORC power output and energy production in Alaska (estimated values in italics). Location Power output Energy production Name-plate (kW) Average demonstrated (kW) Total demonstrated runtime (h) Name-plate (kWh/yr) Average demonstrated (kWh/yr) Capacity factor (%) Cordovaa 260 134.0 382 2265120 1167408 52 Kotzebueb 162 154.7 … 1411344 1348164 96 Unalaskac 150 57.4 30000 1306800 500064 38 Tokd 50 16.6 1138 435600 144619 33 aCordova performance from the 2013 ACEP case study. bKotzebue performance based on 2008 REF application estimates. cUnalaska performance data submitted through March 2016 by the City of Unalaska. dTok performance data from 2013 ACEP report ﬁeld data. TABLE III. Capital costs and O&M costs of ORC systems installed in Alaska (estimated values in italics). Location Capital cost O&M costs Capital cost (USD) Nameplate ($/kW) Actual ($/kWavg) Annual O&M ($/yr) Nameplate ($/kWh) Actual ($/kWh) Cordovaa $1934376 $7440 $14436 $17555 $0.00775 $0.01504 Kotzebueb $1056042 $6519 $6824 $20222 $0.01433 $0.01500 Unalaskac $1889381 $12596 $32916 $1200 $0.00092 $0.00240 Tokd $280500 $5610 $16898 $7600 $0.01745 $0.05255 aCordova capital costs from the REF application cost worksheet; O&M costs projected based on the ACEP case study. bKotzebue costs from REF application estimates. cUnalaska capital costs from REF application. Unalaska O&M actual costs reported by the City of Unalaska. dTok capital costs based on installation of the pre-production module at the ACEP Power Systems Integration Laboratory; O&M costs estimated by the ACEP study. 061707-4 B. Loeffler and E. Whitney J. Renewable Sustainable Energy 9, 061707 (2017) FIG. 1. Alaska ORC capital and O&M costs. The nameplate quantities are represented with triangles, and the demonstrated quantities are represented with circles. The quantities for each installation are connected by color-coded lines. FIG. 2. Alaska ORC capital costs compared with commercial expectations in the Lower 48. Elevated nameplate costs can be attributed to higher costs of shipping, labor, and materials in Alaska’s remote areas. TABLE IV. Capital cost breakdown based on nameplate capacity. Kotzebue’s numbers are based on expected costs and performance from their REF application, with actual installed costs expected to be higher and actual performance expected to be lower. Cordova Kotzebue a Unalaska Tok ORC unit $/kW $3961 $2932 $4256 $2388 % total 53% 45% 34% 43% Materials $/kW $0 b $1533 $4615 $1439 % total 0% 24% 37% 26% Labor $/kW $3452 $1080 $2089 $1780 % total 46% 17% 17% 32% Shipping $/kW $28 c $753 $500 $0 % total 0% 12% 4% 0% Other $/kW $0 $220 $1135 $3 Total $/kW $7440 $6519 $12596 $5610 aBased on expected costs and performance. bORC unit costs not separated from other materials. cShipping from Whittier to Cordova only. 061707-5 B. Loeffler and E. Whitney J. Renewable Sustainable Energy 9, 061707 (2017) From the Unalaska and Kotzebue estimates, it appears that shipping constitutes 4%–12% of the capital costs of an ORC installation in Alaska. Available shipping information is shown in Table IV. Diesel offset The magnitude of the diesel offset is dependent on the generating efﬁciency of the existing diesels, the ORC capacity factor, and the efﬁciency of the ORC system, which is dependent on the temperature of the waste heat and the proper sizing of the system. The total annual savings is the cost savings from the diesel offset minus the ORC O&M expenses. Diesel and cost sav- ings data are compiled in Table VI with estimated or projected values in italics. Levelized cost of energy The estimated cost of energy of each system over a 20-year life was calculated using the National Renewable Energy Laboratory’s Energy Analysis Calculator (http://www.nrel.gov/anal- ysis/tech_lcoe.html). The simple levelized cost of renewable energy (sLCOE) reﬂects the aver- age cost of energy over 20years from a renewable system and is calculated assuming a 3% dis- count rate. Table VII presents the speciﬁc capital and O&M costs along with the capacity factor and 20-year sLCOE. DISCUSSION ORC real world performance While a 20-year design life (Venables, 2014;ElectraTherm, 2015) is the industry standard for commercial ORC generators, of the installations in Alaska to date, only the Green Machines FIG. 3. ORC nameplate capital cost per kilowatt by cost category. TABLE V. Transportation costs for systems to communities in Alaska. Cordova $7220 Barge: Whittier to Cordova Unalaska $75053 Land: Reno to Seattle (706 mi) Barge: Seattle to Unalaska (1951 mi) Kotzebue $122000 Unknown Tok Costs were not separated out Land/Barge: Reno to Tok (2700 mi) 061707-6 B. Loeffler and E. Whitney J. Renewable Sustainable Energy 9, 061707 (2017) located in Unalaska have achieved reliable operation beyond a few weeks. The City of Unalaska reports show that their ORC modules have required only normal maintenance. An important metric in evaluating an ORC’s real world operation is the system’s capacity factor. Real world capacity factors frequently fall short of design values due to maintenance downtime or reduced or intermittent waste heat availability. For the three systems that have operated in Alaska, the Cordova PureCycle brieﬂy demonstrated 52% capacity, the Unalaska ElectraTherm units are achieving 38% capacity, and the Tok ElectraTherm unit demonstrated 33% capacity. The data used in this analysis do not include real time data that could be used to attribute reduced capacity factors to either systems being ofﬂine for repairs and maintenance or reduced outputs due to insufﬁcient heat resources. The percentage of waste heat that can be converted into mechanical work for electricity generation is limited by the thermodynamic availability of the energy in the system, as deﬁned by the Carnot efﬁciency equation: g ¼1 Tc =ThðÞ: Maximum possible ORC system efﬁciency,g, is dependent on both the waste heat tempera- ture, Th, and the available cold temperature resource, Tc (generally the ambient air temperature or natural cold-water sources), where the temperature units are in Kelvin. Typical waste heat to power systems achieve a Carnot efﬁciency of around 1/3 (Elson et al., 2015). Waste heat and power output data were available for all three operating ORC systems. The average waste heat temperatures and calculated operating efﬁciencies achieved by these systems are shown in Fig.3, along with a curve of 1/3 Carnot efﬁciency (assuming a 40 F cold source temperature). Based on waste heat temperatures noted in the available reports, we can see that TABLE VI. Alaska ORC annual diesel offset and cost savings. a Estimated and projected ﬁgures are given in italics. Cordova Kotzebue Unalaska Tok Annual diesel generation b Diesel cost ($/gal) $3.87 $5.20 $2.28 $5.00 Annual generation (kWh) 11490065 20300000 45719844 9776160 Diesel consumption (gal/yr) 841763 1400000 2921748 698297 Electricity fuel price ($/kWh) $0.28 $0.36 $0.15 $0.36 Diesel efﬁciency (kWh/gal) 13.82 14.5 15.69 14 ORC Output Average power (kW) 134 155 57 17 Annual energy (kWh)1167408 1348164 500064 144619 ORC annual impact Diesel offset (gal/yr)84472 92977 31872 10330 Fuel savings ($/yr)$326908 $483480 $72667 $51650 Fuel savings (%)10 6.6 1.1 1.5 Combined efﬁciency (kWh/gal)15.04 15.46 15.82 14.21 Annual savings (Fuel–O&M) ($/yr)$309353 $463258 $71467 $44050 aFuel prices and savings calculated utilizing costs reported for the period of evaluation. bAnnual generation information from REF applications. TABLE VII. Alaska ORC speciﬁc costs and 20-year sLCOE. Location Nameplate capacity (kW) Capital costs ($/kW) O&M costs ($/kWh) Capacity factor (%) 20-yr sLCOE ($/kWh) Cordova 260 $7440 $0.00775 52 $0.117 Kotzebue 162 $6519 $0.01433 96 $0.066 Unalaska 150 $12596 $0.00092 38 $0.254 Tok 50 $5610 $0.01745 33 $0.130 061707-7 B. Loeffler and E. Whitney J. Renewable Sustainable Energy 9, 061707 (2017) only the Unalaska system operated near the expected efﬁciency (Fig.4). Data on the waste heat stream in Unalaska indicate that the waste heat ﬂow was not sufﬁcient to operate the ORC sys- tem at full rated output. Tok and Cordova appear to have produced electricity at a rate below what would be expected for their waste heat resource, reducing their capacity factor. It was noted in the Green Machine report (Lin, 2014) that the amount of waste heat available in most communities may not be enough to run an ORC unit at full capacity year-round, as waste heat availability in summer in some communities may decrease, reducing the operational period of the ORC to 7.5months, or less, a year. ORC real world economics Nameplate capital costs for Alaska projects are greater than those predicted by ORNL and Electratherm data. Elevated nameplate costs can be attributed to higher costs of shipping, labor, and materials in Alaska’s remote areas. Demonstrated capital costs in Alaska are up to seven times greater than expected capital costs in the Lower 48. Much of this difference can be attrib- uted to the Alaska installations operating with relatively low capacity factors, which likely are the result of either maintenance/reliability-related downtime or improper system sizing. Improper sizing can result in an ORC that requires more heat to operate at rated output than that can be supplied or inefﬁcient performance due to ineffective cooling on the cold side of the ORC. The ORC presence in Alaska is not sufﬁcient to comment on cost changes over time. The installation in Unalaska, which is a newer version of the ElectraTherm pre-production ORC sys- tem in Tok, has exhibited improved reliability and decreased O&M costs. Technology trends Organic Rankine cycle system performance is highly dependent on the quantity and temperature of available waste heat, the availability of a low-temperature heat sink, and the properties of the working ﬂuid. New systems are being developed that use efﬁcient working ﬂuids better suited to particular waste heat source temperatures. Exhaust heat captured from diesel generators allows elevated cycle temperatures but may conﬂict with tightening emis- sion restrictions, as the heat exchangers can interfere with exhaust composition. The ORC offers the potential to combine multiple waste heat sources of different qualities or to incor- porate solar thermal and biomass heat sources. FIG. 4. ORC efﬁciency as a function of waste heat temperature. Expected efﬁciency assumes a cold source temperature of 40 F and achievement of 1/3 Carnot efﬁciency. 061707-8 B. Loeffler and E. Whitney J. Renewable Sustainable Energy 9, 061707 (2017) Tech-specific storage systems The energy generated by the ORC unit is integrated into the main power plant electric gen- eration grid. The heat used to generate power through the ORC comes from the power plant directly as waste heat. Some systems use thermal storage when combined with other renewable energy sources such as solar photovoltaic power. CONCLUSIONS Capacity factors range from 33%–52% for installations that have already been installed. Low utilization levels are a result of insufﬁcient waste heat rather than inefﬁcient ORC opera- tion (in Unalaska), as well as the use of a prototype pre-commercial model (in Tok). While operation and maintenance costs vary, signiﬁcant annual fuel savings have been realized for each installation, with annual demonstrated savings of $70,000 in Unalaska and projected annual savings of over $300000 in Cordova. A 20-year design life is the industry standard for commercial ORC generators although of the installations in Alaska, only the Unalaska Green Machines have achieved reliable operation beyond a few weeks. Modifying existing generation for an ORC system has proven to be challenging and expen- sive. Project cost data indicate that Alaska projects should expect total capital expenditures to be two to three times the cost of the ORC unit itself. Some systems have been highly reliable and cost-effective, while other installations have been neither. The most cost effective ORC system may be best implemented with a ground-up new generator design and installation. Of the installations in Alaska, only the Unalaska Green Machines have achieved reliable operation beyond a few weeks. The smallest reliable system, which operates in Unalaska, has a 50kW nameplate capacity and requires 500kW of waste heat, indicating that this technology is best suited for communities with 1MW or more of diesel generation. Organic Rankine cycle generators are most efﬁcient with higher-temperature waste heat sources. The choice of working ﬂuid is also a factor in efﬁciency. All ORC units in Alaska use either R-245fa (pentaﬂuoropropane) or ammonia. Looking forward, new ORC systems are being developed that use efﬁcient working ﬂuids better suited to particular waste heat source tempera- tures. An ORC offers the potential to combine multiple waste heat sources of different qualities or to incorporate solar thermal and biomass heat sources. Heat capture from diesel generator exhaust allows elevated ORC temperatures and increased efﬁciencies but may conﬂict with tightening emission restrictions, as heat exchangers can interfere with the exhaust composition. There is also difﬁculty in receiving performance guarantees from ORC manufacturers. Installations that are more efﬁcient require approved rate adjustments to recover debt and cost; however, rate proceedings are very expensive and time- consuming. The ORC unit itself accounts for a third to a half of the total capital costs, indicating that Alaska projects should expect total capital expenditures to be two to three times the cost of the ORC unit itself. Shipping is less than 10% of the cost in all installations. Table VIII compares the projected sLCOE for the ORC systems with the existing cost of diesel generated electricity. All installations except for Unalaska projected ORC sLCOE repre- senting a savings over current diesel generation costs. TABLE VIII. Comparison of ORC sLCOE with the existing Diesel generation electricity cost. Location ORC 20-yr sLCOE ($/kWh) Existing generation fuel cost ($/kWh) Cordova $0.117 $0.28 Kotzebue $0.066 $0.36 Unalaska $0.254 $0.15 Tok $0.130 $0.36 061707-9 B. Loeffler and E. Whitney J. Renewable Sustainable Energy 9, 061707 (2017) ACKNOWLEDGMENTS The authors wish tothank the Alaska Energy Authority for its funding tosupport this project. Many people have contributed insight and information to this report. For their review and comments, we wish to thank Bob Grimm and Ben Beste of Alaska Power and Telephone; Earl George and David Burlingame from Electric Power Systems; Bob Deering, Renewable Energy Coordinator for the United State Forest Service Alaska Region; Dan Winters, Director of Public Utilities for the City of Unalaska; Dave Messier, Rural Energy Coordinator at the Tanana Chiefs Conference;and Devany Plentovich andNeil McMahon ofthe Alaska Energy Authority. Borji, A., Barnhart, J., Winningham, J., and Winstead, A., “Convert waste heat into eco-friendly energy. New develop- ments, such as the organic Rankine cycle, help operations go ‘green,’” Hydrocarbon Process.89, 57–61 (2010). Cordova Electric Cooperative,ftp://www.aidea.org/REFund/Round%201/Applications/22_OrcaPlantEfﬁciencyUpgrade_ CordovaElectricCooperative/C%20-%20AEA%20ORCA%20Application.pdf for REF grant application text, 2008a. Cordova Electric Cooperative,ftp://www.aidea.org/REFund/Round%201/Applications/22_OrcaPlantEfﬁciencyUpgrade_ CordovaElectricCooperative/E%20-%20AEA%20ORCA%20Budget.pdf for REF grant application budget, 2008b. Cordova Electric Cooperative,ftp://www.aidea.org/REFund/Round%201/Applications/22_OrcaPlantEfﬁciencyUpgrade_ CordovaElectricCooperative/D%20-%20AEA%20ORCA%20Costworksheet.pdf for REF grant application cost work- sheet, 2008c. ElectraTherm,4400 Speciﬁcation Sheet (ElectraTherm, 2015). Elson, A., Tidball, R., and Hampson, A.,Waste Heat to Power Market Assessment (ICF International for Oak Ridge National Laboratory, 2015). Kotzebue Electric Association,ftp://www.aidea.org/REFund/Round%202/Applications/235_Kotzebue%20HR%20 and%20Ammonia%20Power%20Cycle/AEA-REF-WasteHeat.pdf for Proposal for Renewable Energy Fund Alaska Energy Authority Grant: Ammonia Power Cycle Waste Heat Recovery System, 2008. Lin, C.-S.,Green Machine Organic Rankine Cycle Field Test May–December 2013 (Alaska Center for Energy and Power, 2014). Liu, B.-T., Chien, K.-H., and Wang, C.-C., “Effect of working ﬂuids on organic Rankine cycle for waste heat recovery,” Energy 29, 1207–1217 (2004). Venables, J.,Case Study of the PureCycle 280 Organic Rankine Cycle Machine Installed in Cordova, Alaska (Alaska Center for Energy and Power, 2014). Whealy, R. E., Taylor, W., and George, E., City of Unalaska Powerhouse Exhaust Gas Waste Heat to Energy Project Final Report EPS Project No. 10-0159, Electric Power Systems, Inc., 2012. 061707-10 B. Loeffler and E. Whitney J. Renewable Sustainable Energy 9, 061707 (2017)