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Nome Waste Heat Utilization Project Phase I-Preliminary Assessment 1983
NOM 002 NOME WASTE HEAT UTILIZATION PROJECT Phase I — Preliminary Assessment prepared for the NOME JOINT UTILITIES BOARD City of Nome, Alaska S.D. Wolfe, Manager electrical power : MAY 1983 (building space heating diesel electric generator water jacket water heating exchanger polarconsult alaska, inc. CONSULTING ENGINEERS AND PLANNERS ols Econ cenietnaon LETTER OF TRANSMITTAL ANCHORAGE, ALASKA 99507 (907) 561-1933 Telex 26708 PCA AHG ro AlASKA fue AueRty —-_lER Ry’ Leen | WE ARE SENDING YOU OO Shop drawings 1 Copy of letter DATE JOB NO. Gt BZ Ni ‘Nome Waste Hear | PREM NOR FINENESS ttached (©) Under separate cover via________the following items: 0 Prints 0 Plans 0 Samples 0 Specifications Cl Change order ~~ kein || " ConCerTOL cosy Sm ATE THESE ARE TRANSMITTED as checked below: CO For approval seor your use CAs requested (For review and comment ( Co FOR BIDS DUE REMARKS CO Approved as submitted ( Resubmit copies for approval OC Approved as noted 2 Submit copies for distribution C Returned for corrections OC Return corrected prints n os Co PRINTS RETURNED AFTER LOAN TO US top ip cferere| Whernatten os - COPY TO : = Rr If anclnsuras are no tae nated kindly notify us _ NOME WASTE HEAT UTILIZATION PROJECT Phase 1 — Preliminary Assessment prepared for the NOME JOINT UTILITIES BOARD _ City of Nome, Alaska S.D. Wolfe, Manager MAY 1983 MARK NEWELL Project Manager : PETER N. HANSEN _ Energy Engineer (Mechanical) _ © COPRIGHT 1983, POLARCONSULT ALASKA, INC. TABLE OF CONTENTS Description Page EXECUTIVE SUMMARY SECTION 1 - INTRODUCTION Exiating Conditians occu cn ue ano he55 55 6446 80 tees 1.1 62 Future Facilities cecwncnnetacaacteaenwewen seek eee ewe 1.3 Plan for Future Generator Installation .........cceee0- FNF SECTION 2 - WASTE HEAT CHARACTERISTICS Waste Heat from Diesel Generation ...cecrscesceecceees 8 Seasonal Variations ....... COO e ee eee eeserc eee ceeesce 10 Diurnal Varlations 026.0 c ccc cscccccvccccccccccccvcce 13 Operational Variations ....... CASSETTE ee TC KRS 18 Future Waste Heat AvallabI lity .....cccccccccccccece 18 NNNNN eo 6 © 2 UPA Ne Seite « oe ee SECTION 3 - WASTE HEAT USE OPTIONS SUMMArY Mere cle lore elec sleleieiciele cele eles eleiciejeiene wielctele crete cleleleterereies ae City Water Heating at Belmont Point ......ceccceeeccese 22 Remote Generator at the Nome/Beltz High School ....... 23 Upgrading of the Snake River Power Plant Heating (Sy SiGeMni 6 a si0.001s.0.6 01,5. 6. 619)0):6).0),¢e010).01 16 wepekeleloleneiiehelonepene.e miech District Heating Loop In the Power Plant Vicinity .... 26 District Heating Loop to the Airport ......eeee eiatetehelens 26 District HeatIng Loop In Downtown Nome ..... cliclieliclieielelelere mia.) Greenhouse Project ..cccccccccccccs oifelioile (ee 016,610) sue\ieilelo io eus 3 28 Other ..... SSCS RCKRER ESE ESTEE HOSS siisialetelsle ole clalisioiclieleiele sco WWW Ww ee FUNDe WNW WwWw ee eee Wwonau SECTION & - OTHER CONSIDERATIONS hel General wccccccccccee CORNER ERR |S Case deleiiiswccces SO U2 ENERGY MSLORAGE Me. oo aiciciclclelcle cletalielslichsielsretoisre c's «selene erect OU 4.3 Reserve Capacity RequirementS ....ccccceccccccccccseee SL 5% Water Tank Leekag@ ceccncssunceweweuewessasscasenessssss 32 SECTION 5 - ECONOMIC ANALYSIS 5.1 General wccccccccccce Cee errr rcsesccesececceccccseccese ID 5.2 Cost of Options pcavcwewsnccenvecrwessesesacnwne sees) OF 5.3) Benefits Vs. Costs, scninncnese cc eiratrel(oNeteWolelel stetetarehenahsterctctel ster simes O Gre SUINMMA Ya rotieis oe oi silos 6h0) 6) si ucue) sire lone) ser ouoieloliclieliolelereieiors cheliokelelepoieneno mei) Description Page SECTION 6 - CONCLUSIONS AND RECOMMENDATIONS 6.1 General ConclusIOns ...cccccrccccccccscccccceccesvcccce Al 652 Recommendations sswsccscssccsssvccwessessecssssnoescsoss 42 APPENDICES A. Technology Profile for District Heating B. Technology Profile for Cogeneration BIBLIOGRAPHY =~ Introduction O EXISTING FACILITIES OFUTURE FACILITIES ; OPLAN FOR FUTURE GENERATOR INSTALLATION SECTION 1 - INTRODUCTION 1.1 EXISTING FACILITIES The existing generating facilities In Nome tnclude seven dlesel generator sets of varlous types and with varying remaining service lives. Table 1 summarizes key data for these generator sets. TABLE 1 EXISTING GENERATORS UNIT OUTPUT HRS, EFFICTENCY LUBE OIL NO. TYPE YEAR KW TOTAL KWH/GAL GAL /MWH 1 Cooper Bessemer 1954 600 37826 12.99 0.52 2 Cooper Bessemer 1954 600 36763 12.76 0.59 3 Cooper Bessemer 1952 600 36093 12.57 0.59 a GM Cleveland 1943 300 ? 11.63 0.91 5 Cooper Bessemer ? 1235 50978 13.75 0.26 6 Fairbanks Morse 1962 1035 11024 12.38 0.87 8 EMD 1980 2600 6320 13.49 0.37 Units 1 through 6 are located in the power plant at Snake River Point. Unit 8 is a remote unit located at Belmont PolInt. Both facilities seem very well maintained, and the Power Plant Operating Report indicates that the power plant Is professtonally operated. However, all units In the Snake River power plant are 20 to 40 years old, and most units have accumulated a rather large number of operating hours. The "Total Hrs." in Table 1 Is computed from the time of the last overhaul In most cases since historical information Is lacking. All numbers are current as of April 1983. Waste heat from the power plant Is utilized to heat city water and meets all demands for this. Unit No. 4 Is not connected to the waste heat recovery system. Also, the remote unit CUnIt No. 8) Is not connected to any waste heat recovery system. This In return limits the generating flexibility due to the need for heating the city water. As older generators are phased out at the Snake River power plant, this problem could become even more significant if remote units with waste heat recovery for space heating and without connection to the city water system were added. Replacement of the older units would typically be In the form of larger units. In Nome, the operation of a remote unit does not seem to cause any problems. This gives the option of placing a unit In a location where the waste heat can be utilized in a cost effective manner. 1.2 FUTURE FACILITIES The current generating capacity In Nome is approximately 7 Megawatts (MW) or 7,000 kilowatts (CkW) The peak load Is approximately 3.5 MW; thus a capacity factor of approximately 2 is present. This would normally be considered sufficient, as peak load could be met even If the largest unit was down. Due to the age of some of the units In Nome, an unfortunate situation can be foreseen. For example, let us surmise that Unit No. 5 Is down for an extended period of time because of lead time on spare parts; if Unit No. 8 breaks down during this period, the peak load can no longer be met. Based on References (1) and (2), a demand and peak load forecast has been made for Nome, TABLE 2 DEMAND AND PEAK LOAD FORECAST TOTAL JACKET TOTAL WASTE WASTE DEMAND PEAK HEAT HEAT DEMAND AND DEMAND/CAPITA MWH/YEAR (2) LOAD (3) GALS OIL GALS OIL YEAR POPULATION KWH/YEAR 61) X_1000 MW. X_1000 X_1000 1983 3317 5850, 1.94 3600 597 358 1984 3383 6142 2.08 3860 640 384 1985 3451 6450 2.23 . 4138 686 412 1986 3520 6772 2.38 4416 732 439 1987 3590 7111 2.55 4732 785 471 1988 3662 7466 2.73 5066 840 504 1989 3735 7840 2.93 5437 902 541 1990 3810 8232 3.14 5827 966 580 1991 3829 8643 3.31 6142 1019 ‘611 1992 3848 9075 3.49 6476 1074 644 1993 3867 9529 3.68 6829 1132 679 1994 3886 9910 3.85 7144 1185 711 1995 3906 10307 4.03 7812 1296 778 1997 3945 11148 4.40 8165 1354 812 1998 3965 11593 4.60 8536 1416 850 1999 3985 12057 4.80 8907 1477 886 2000 4005 12540 5.02 9315 1545 927 2001 4025 13041 5.25 9742 1616 970 2002 4045 13563 5.49 10188 1689 1013 2003 4065 14105 5.73 10633 1763 1058 2004 4085 14810 6.05 11227 1862 1117 According to this forecast, per capita consumption in Nome by the turn of the century will be comparable to the per capita consumption experienced In Anchorage In 1982. No extraordinary conservation measures were anticipated to take place In this scenarlo, and neither were any major peak shaving’ energy Management measures. C1) Based on (2) C™Non-OCS Base Case Population"). (2) Based on 1982 statistics with 5% annual increase untlIl 1993, and 4% annual Increase from 1993. CIncrease ratios are from (1).) (3) Based on 1982 Peak Load/Total demand ratios. As this ratio normally decreases with system. size, peak load forecast would be high late in planning period. 1.3 PLAN FOR FUTURE GENERATOR INSTALLATION AND RETIREMENT The demand and peak load forecast from Table 2 calls for a continuous upgrading of existing facilities In order to meet projection demands. Table 3 summarizes a plan which willl make It possible to meet projected requirements using Increasing generator rises as demand grows. This plan also places emphasis on heavy utilization of newest equipment In order to have the most current equipment on line at all times. This will reduce overall operation and malntenance cost and allow greater flexibility im choosing the right size equipment for the current demand. The generating capacity planned to be available will at all times .be able to deliver the projected peak load, even If the largest unit Is down. The plan calls for retirement of Unit Nos. 2, 3, and 4 in 1986, when another 2.5 MW unit CEMD or slow turning diesel of comparable size) Is to be Installed. By that time, Units Nos. l, 2, and 3 should each have accumulated 45,000 to 50,000 hours and one or more of the three units should be kept on an emergency stand-by status. In 1990, a last 2.6 EMD, or a generator of comparable size, Is to be brought on line while Unit No. 5 is retired. By the year 1998, Unit No. 8 (the EMD Installed In 1980) will have accumulated approximately 96,000 hours and will be kept on emergency standby only. The growing demand at this time will call for additional 5,000 kW capacity and, providing that the operational savings with units this size make it feasible, the 5,000 kW should all be delivered by one large unit. This could be a slow speed 2 stroke diesel burning cheaper No. 3 fuel oll. At this time, Unit No. 6 should be retired also. According to this plan, it has been operating as a peak load unit since 1984, and should thus be ready for retirement. Finally, In the year 2002, another 5,000 kW unit Is to be brought on lIne and Unit No. 8 will be retired completely while Unit No. 9, Installed In 1986, Is kept as an emergency standby. As can be seen from Table 3, the life expectancy for the EMD Is estimated at 96,000 hours with two or three major overhauls. Figure 1 shows the projected peak loads over the planning perlod and shows the units on line at any particular time, unit numbers In parenthesis Indicate that the unit Is on emergency stand-by only. TABLE 3 GENERATOR UNIT INSTALLATION AND RETIREMENT SCHEDULE HOURS UNIT EMERGENCY TIME ACCUMULATED NO. SIZE ON LINE STAND-BY RETIRED ACCUMULATED 2004 kW Year Year Year Hours Hours 1 600 1954 1986 1990 47,500* N/A 2 600 1954 1986 1990 47,500* N/A 3 600 1952 1986 1990 47,500%* N/A 4 300 1943 N/A 1986 N/A* N/A 5 1235 N/A* 1990 1994 78,000* N/A 6 1035 1962 N/A 1998 43,000* N/A 8 2600 1986 1998 2002 96,000 N/A 9 2600 1986 2002 96,000 96,000 10 2600 1990 N/A N/A 62,000 11 2600 1994 N/A N/A 28,000 1/2 5000 1998 N/A N/A 56,000 13 5000 2002 N/A N/A 12,000 Pr Historical data Is incomplete. It should be noted that this plan does not preclude the possible Installation of a diesel generator for co-generation purposes at the None/Beltz High School complex. If this installation Is made, the need for additional peak load capacity will simply be FIGURE 1 POWER PLANT UPGRADING SCHEDULE 20 19] unit number in service 18) 7 unit number on emergency stand by 16 =a=am peak load 15) 14 13 MW 12 11 16 11 WwW - | 102. 104 > oO s ° asp e | s | 2 | Ys [2] oO sje{ » | e | 3 [a] \ oO 8 === © © Roo alylo| o lat \ sleje| ex © ff glele| « Ke ff 96 98 a The dotted line represents the estimated peak load over a 20 year perlod. Clear unit numbers Indicate units in service; shaded numbers Indicate units on emergency stand-by status. The heltght of the unit number box Indicates the unlit stze. delayed accordingly. The added costs Incurred by adding more smaller units Instead of one big unit could easily be Justified If a reasonable amount of waste heat was recaptured from these smaller units. 2 - Waste Heat Characteristics © WASTE HEAT FROM DIESEL GENERATION O SEASONAL VARIATIONS ~ ODIURNAL VARIATIONS O OPERATIONAL VARIATIONS O FUTURE WASTE HEAT AVAILABILITY SECTION 2 - WASTE HEAT CHARACTERISTICS 2.1 WASTE HEAT FROM DIESEL GENERATION Waste heat from diesel generation Is available from a number of sources, |l.e., from exhaust, jacket cooling, oil cooling, turbo charger and manifold cooling, or from engine radiation. Whether a particular waste heat source permits recovery depends largely on engine design and size. For this study, only jacket cooling and exhaust gas are considered to be of any Interest. Figure 2 shows typical energy flow through a diesel generator. 2.1.1 JACKET COOLING Jacket water cooling can provide approximately 30 percent of the heat value of the fuel burned. The exact amount Is a function of numerous parameters, Including design, load, adjustments, etc. For this study, 30 percent Is used for all generators. The max imum temperature available Is approximately 200°F depending on type, manufacturer, etc. This temperature Is normally adequate for space heating via a district heating loop. Utilization of jacket water waste heat Is normally considered simple and cost effective. 2.1.2 EXHAUST GAS COOLING Utilization of exhaust gas heat is also an old and well known technology, as almost any diesel driven ship of any appreciable size Is utilizing exhaust gas heat for steam generation. Temperatures up to 800°F can be reached, which is of course much higher than needed for space heating. FIGURE 2 ENERGY FLOW THROUGH DIESEL GENERATOR stack loss 9% radiation etc. 8% Out of 100 Btu of fuel burned In a diesel generator, typically 33 Btu are converted to electricity, 30 Btu can be recovered from the cooling jacket, and 20 Btu can be recovered from an exhaust gas boller. Nine Btu are lost with the exhaust gases and 8 Btu are lost due to radiation, etc. The technology Is quite simple as the exhaust gases are led through a boller similar to a conventional steam or hot water boiler. Recoverable waste heat from exhaust gas Is 15 to 30 percent of the heat value of the fuel burned; for this study, 20 percent has been used as a rather conservative number. Recent utilization of exhaust gas waste heat has not been very successful In Alaska as severe corrosion and valve burning has been experltenced. Such problems are normally caused by poor malntenance and/or operational errors. Even though utIlization of exhaust gas waste heat Involves simple and well known technology only, It should not be used In any location where operation and maintenance Is not performed by a professtional and experienced crew. 2.2 SEASONAL VARIATIONS As the amount of waste heat available Is almost proportional to the amount of electricity produced, it Is evident that’ the dynamics from the electric grid to a great extent govern the output from a waste heat recapture system. To determine the feasibility of a waste heat recapture system, the amount of waste heat available must be compared to the heating load for any system. Figure 3 shows a typical seasonal variation in heating load. The seasonal variation In electricity demand fs however somewhat different as can be seen from Figure 4&, In comparing the two figures, we can see that the heating load varlation Is much greater than the variation In electricity demand. Thus If we design a waste heat recapture system based on space heating that will utilize all the heat available during the summer, this system will need additional heat during the winter. Or, It we design a system that does not need additional heat during the winter, this system will not be able to utilize all the heat available during the summer. 10 FIGURE 3 TYPICAL VARIATION SEASONAL HEATING LOAD Hid a i A July requires less than 3 percent of the total yearly heating load, while February requires almost 14 percent. 11 FIGURE 4 TYPICAL VARIATION SEASONAL ELECTRICAL LOAD TTT \ 1] / / l y Waal aks ) | I | ! | ! | | , month In Nome, a part of the waste heat Is used for heating the city water. Thus the amount of waste heat available Is not only dependent on the electricity demand, but also on the water consumption. Figure 5 shows the average seasonal heating load from heating the city water to 50°f and the seasonal varltation in average avallable waste heat from Jacket cooling and from jacket cooling and exhaust gas (stack) combined. The amount of heat not used for water heating Is avallable for other purposes. This amount Is shown in Figure 6. Reference (2) Indicates that 1 kW of heat will keep 135 square feet of public type building floor area heated at 0°F outer temperature. Thus the approximate 3200 kW avallable In December should be sufficient to heat 432,000 square feet of school, hospital, etc. This number however only gives an Idea of the order of magnitude. Several parameters have to be taken Into account, I.e., diurnal variations In the load, the Insulation standard of the bulldings, the heat loss In the system, etc. These factors all tend to decrease the area that can be heated. If only jacket water heat was utilized, the amount of heat available for other than city water would be approximately half of the amounts mentioned above. 2.3 DIURNAL VARIATIONS The diurnal variations In the city water heating load, avallable jacket heat, and available jacket heat and stack heat combined can be seen on Figure 7 for a typical summer day. The corresponding amounts for a typical winter day can be seen on Figure 8. 13 The heavy heating. engine FIGURE 5 SEASONAL VARIATION WASTE HEAT AND CITY WATER HEATING 400 fl ; AVAILABLE HEAT AVAILABLE HEAT ~ STACK AND ~ JACKET meen =JACKET — I “ ====] HEATING LOAD CITY WATER (DERG: Re 3000 i so = 2 2000) a ' , 1000}: a a Se egos pee poss erese ooo = sae == Sse esas ee see: a = ss ae = ee BE Ss oes ee ee = SS oF = ee — = “ ! : 6 TT wl 12 month line shows the average load per month on city water CWater Is cooler In summer and Is assumed heated to 50°F year round.) The dotted jacket. The thin line line represents available heat from 14 represents the total available waste heat from engine jacket and exhaust gas boller (stack). FIGURE 6 SEASONAL VARIATION EXCESS WASTE HEAT 400 1. { IL EXCESS HEAT gg! EXCESS HEAT R= srsccaso UD er 1 3000 100 The broken ltIne shows the total amount of heat avallable for space heating from the stack and jacket. uS) FIGURE 7 DIURNAL VARIATION WASTE HEAT - SUMMER 1 | 4000 ic AVAILABLE HEAT HEATING LOAD STACK AND - CITY WATER JACKET AVAILABLE HEAT - JACKET 3000 + { | 200 kw heat 1000 | Hl | | al aia | a : a f SaaS: See eS eee a Bota SE Soe Soseeoes SSeS eon i SOOO APOC esas EO TOQ KT soit HAE OS ae Ha ae ae RS OEE se OES: 2029421028007 SEs, gee seSsoserares eae CRAG Oar AQIS ES: Scrseeeates Pe 3 Su Sr so sie Ss SOO 14 SOO OO Ee 0 3! 6 9 12' 15 18 21 24 hour The heavy line shows the water heating load varlation. The broken line represents the avallable Jacket heat, and the thin line shows the varlation In the total waste heat amount avallable. 16 FIGURE 8 DIURNAL VARIATION WASTE HEAT - WINTER , AVAILABLE HEAT - STACK 4000 AVAILABLE HEAT ~ JACKET = HEATING LOAD ~ CITY WATER The heavy line shows broken line the water heating load vartation. The represents the avallable Jacket heat, and the thin line shows the varlation In the total waste heat amount avallable, 17 The amount of Jacket heat not used for city water heating can be seen on Figure 9 for typical summer and winter situations. The corresponding amounts of jacket and stack heat can be seen on Figure 10. 2.4 OPERATIONAL VARIATIONS The relatively limited amount of heat available at night could be compensated for by using automatic night set back of temperature In bulldings that are primarily used during the day. Also, operational experience would allow a coordination of water pumping and waste heat utilization In such a manner that city water heating loads were limited during hours with heavy space heating loads. Lied FUTURE WASTE HEAT AVAILABILITY The amount of waste heat avallable can be considered almost proportional to the number’ of kilowatt hours generated. Figure 11 shows the amounts of waste heat avallable over the next 20 year period according to the electricity demand forecast as described In Section 1.2. As can be seen from Table 2, the amount of waste heat available [In 1982 equals approximately 600,000 gallons of ofl worth more than $800,000. As discussed earlier, this Is the theoretical upper limit for waste heat utI lI zation. In the real world, this limit will of course be lower. 18 FIGURE 9 DIURNAL VARIATION EXCESS WASTE HEAT - JACKET | 4000 | | | +- gg wnter SUMMER L 3000 3 oo 2 2000 3 x 1006 | 6 9! 12 15° 18 24 hours The heavy line shows the waste heat avallable for space heating In summer. The broken line shows the waste heat available for space heating In the winter. lg FIGURE 10 DIURNAL VARIATION EXCESS WASTE HEAT - STACK AND JACKET 4000 Cl SUMMER 3000 2000 kw heat Seateaag reer oad hit see aie Sie seneanenenur hannah z sear SrT oa: 555 The heavy line shows the waste heat available for space heating in summer. The broken line shows the waste heat avallable for space heating In winter. 20 FIGURE 11 FUTURE WASTE HEAT AVAILABILITY x 1000 galions of oll equivalent Based on the electrical load forecast from SectlIon 1, the broken line shows future waste heat avallable from jacket water. The heavy line represents the total waste heat amounts estimated to be available from jacket and stack combined. 21 4 Waste Heat Uses—Options O BELMONT POINT PLANT CONVERSION O NEW SCHOOL SITE O DISTRICT HEATING = SNAKE RIVER POINT - IN-PLANT USE. - BELMONT POINT — AIRPORT - DOWNTOWN O GREENHOUSE SECTION 3 - WASTE HEAT USE OPTIONS 3.1 SUMMARY A number of waste heat use options presently exist In Nome. Some of these are: le City water heating with EMD at Belmont Point. 2. Relocation of an existing diesel or Installation of new medium size diesel with waste heat recapture for space heating and city water heating at the Nome/Beltz High School. 3. Upgrading of the Snake River power plant heating system to utilize waste heat. 4, District heating loop from the Snake River power plant to the airport. 56 District heating loop In the Snake River power plant vicinity: 6. District heating loop In the downtown area (Bering Street / Front Street) from the Belmont Point Plant. 7 Construction of a greenhouse behind the Snake River power plant. 8. Other. Brea, CITY WATER HEATING AT BELMONT POINT This option would add flexibility to the power generating system, as the best combination of generators could be chosen for any load. In the present situation, the demand for city water heating limits the use of the EMD and forces operation of less efficient units. As there are no oil fired boilers being used to heat the water system, the energy savings will however be limited. Assuming an average Increase In electrical output from 13.185 kWh per gallon to 13.4 kWh per gallon, the annual savings will amount to approximately $30,000. Considering the Power Plant's annual fuel ol] budget of almost $2,000,000, a saving of 22 this magnitude wlll not have any noticeable economic Impact. rt might however be sufficient In order to pay off In a relatively short time perlod. “Thus this option should mainly be used as an operational Improvement. 3.3 REMOTE GENERATOR AT THE NOME/BELTZ HIGH SCHOOL The Nome/Beltz High School complex has an average annual heating load of approximately 1.82 million Btu per hour, or 532 kW. The corresponding peak load is estimated at 5.4 milllon BTU per hour, or 1,580 kW. It has been estimated that 80 percent of the total heat consumption takes place when the load is 50 percent, or less, of the peak load. Thus a diesel generator with an electrical output of 790 kW will provide 80 percent of the total heat consumption if only jacket water heat Is utilized. If jacket and exhaust gas heat are utilized, a diesel generator with an output of 457 kW wlll provide 80 percent of the total heat consumption. Gites assumed that the generator Is allowed to generate at 100 percent load whenever the heating demand calls for It.) The average electrical load at the school complex Is only 165 kw; thus the electrical Intertie from the school to the city would have to have a transfer capacity similar to the generator's maximum output. The line has more than 1 MW transfer capacity. However, the Intertie runs along the Nome/Beltz road, so there Is a certain risk of this line being hit by a car and knocked down. If this happens at a time when the generators on line within the city limits are not capable of handling the current load, the entire system will go down. If the generator at the Nome/Beltz High School is limited to approximately 800 kW, the EMD at Belmont Point would, at most times, be capable of compensating for a sudden loss of the power generated at the high school. 25 The relocation/Installation at the high school should Include a diesel generator of approximately 800 kW output and with Jacket heat recapture only. Consequently, If future heat demand In the vicinity called for it, the exhaust gas utIlIization could be added at a nominal cost, providing that the Initial system Is designed with this In mind. The annual fuel oll savings at the school would amount to between $150,000 and $160,000 with this configuration. If the Installation Is made whenever added generating capacity is needed anyway, the extra cost compared to Installing the generating capacity In the power plant will be rather limited. The feasibility seems quite promising, and this option should be subject to further Investigation. 3.4 UPGRADING OF THE SNAKE RIVER POWER PLANT HEATING SYSTEM The offices surrounding the Snake River power plant are currently heated electrically, while at the same time large amounts of waste heat are discarded Into the atmosphere. The cost of electricity to the power plant will always be at least the cost of fuel burned. At $1.35 per gallon and 13 kWh produced per gallon burned, this amounts to approximately $.10 per kWh. It should also be noted that the operating personnel are exposed to cold drafts due to Insufficient ventilation. This problem could be remedied at the same time. When judging the feasibility of this project, It should be taken Into consideration that there Is a possIbIlity that no new generators will ever be Installed in this power plant. A feasible utilization of waste heat requires that the power plant is located close to the end users of the heat. This makes the Snake River Point location less desirable than the Belmont Point location. Also, the Snake River power plant is located on a flood plain; thus there Is a possibillty that Nome might at_ some time lose Its power plant due to flooding. However, a good number of years In service as a peak 24 load plant can be foreseen, and a short pay back time seems likely on this conversion. The conversion would Include the circulation of engine coolant In bulldings and Installation of unlt/cabInet heaters and base board ‘heaters. Assuming an average heat loss of 0.35 BTU per hour per degree Fahrenhelt per square foot, the peak load will be 441,000 BTU per hour. A backup boller should be Installed in order to keep bulldings warm In the event the power plant Is shut down. This would allow complete shutdown of the Snake River plant whenever operational or maintenance considerations called for this.* An oll fired boller with 600,000 BTU per hour Input should be sufficient for this purpose. It might seem uneconomical to transfer the load to the EMD and shut down the Snake River power plant at night. This would necessitate the burning of fuel oll In order to keep the Snake River power plant warm. However, the added efficiency of the EMD would more than compensate for this. Consider this calculation: 600 kW on Cooper Bessemer gives ol] consumption of 47.0 gal/hr. 600 kW on EMD gives olf1 consumption of 44.5 gal/hr. Oi] saved 2.5 gal/hr. Boiler consumption at 240,000 BTU/hr output Cavg. load) 2.2 gal/hr. x Providing that the Belmont Point power plant was connected to the city water system. 25 This means that shutting down just one Cooper Bessemer and transferring the load to the EMD would more than compensate for the bolfler oll consumption. Also, flexibility of operation would be greatly Increased, as the EMD at Belmont Point could be operated as a true base load plant. Even though the energy savings from this conversion are rather small, this Implementation would allow for considerable Indirect savings as It adds flexibility to the generating system and allows for remote units with waste recapture to be bullt and operated as base load or first priority peak load units. 3.5 DISTRICT HEATING LOOP IN THE POWER PLANT VICINITY As a separate option or as part of Option 4, a small district heating loop could be constructed In the Snake River Point power plant vicinity. This would only allow for utilization of a small portion of the total waste heat amount avallable, and It should be judged as a minor project only. The warehouse type bulldings In the area are within close distance to the power plant; thus this project could be feasible. If this district heating loop was constructed, it could at a later point in time be extended In order to supply heat to future port facilities In this area. 3.6 DISTRICT HEATING LOOP TO THE AIRPORT If It was decided to maintain the power plant at the Snake River Point location, supplying the airport with district heating could become a viable option, as piping distance is less than 2,000 feet. However, It should be recognized that the airport would only be able to use a small portion of the heat avallable. The use of existing World War II vintage concrete utIlidors for district heating Is not believed to provide any significant savings as compared to using new preinsulated district heating pipes. 26 Diol, DISTRICT HEATING LOOP IN DOWNTOWN NOME A large scale utilization of waste heat In Nome would have to Include a district heating loop In the downtown areas In order to utilize the large amounts of waste heat available. This could be done by constructing a main transfer line from the Belmont Polnt power plant along Seppala Drive to Bering Street. On Bering Street one branch would extend north across Fifth Avenue and one branch would extend south to and along Front Street to Moore Way. This plan would not necessarily fix the Belmont Point location as the natural location for additlonal generating units as these become needed. When designing the main transfer lines, future expansion of Nome's generating capabilities should be taken Into consideration In order to keep the total Investment per recovered heat unit as low as possible. Public bulldings and major privately owned buildings would be served first, and the system would be expanded as local operating experience and public acceptance warranted. On general district heating, see the Technology Profile in the appendix. This option Is obviously the most expensive, as It contains a lot of major construction work. The transfer line to Bering Street would be two prelinsulated 6-IiInch lines with outer diameters of 10 Inches; each line would be about 0.5 miles long. Fully utilized, the Belmont Point power plant would be capable of providing heat for the replacement of approximately $600,000 worth of ol]! per year at current oil prices. A general district heating system In parts of Nome could very well be fed Into from more different locations, and future generating units could easily be located closer to the heat end users. It should, however, be recognized that there are considerable environmental benefits In keeping a power plant 217) separated from densely populated areas. These benefits particularly Include reduced alr and nolse pollution. Even If a five year pay back time was required, this option would still allow for approximately $3 million of constructlon work. 3.8 GREENHOUSE PROJECT Reference (3) Indicates a heating load of 114 BTU per square foot for a greenhouse with heated soil. Thus a typical electrical load of 2.5 MW would provide heat for city water heating plus 90,000 square feet of greenhouse if exhaust gas was utIlized. Without exhaust gas utilization, this number would be 65,000 square feet. The benefit from this project would most likely be limited number of new jobs In Nome. Reference (3) Indicates a construction cost of $127 per square foot In Antak. If no other expenses (labor, seeds, fertilizer, etc.) were Incurred, a pay back time of 19 years would still be experltenced. It Is recognized that the Anfak project in Reference (3) Is partly a research project; the economics still seem somewhat questionable. In McGrath, a grant funded greenhouse heated with waste heat Is operating with economic benefits to the village. 3.9 OTHER Several other waste heat recapture options are avallable to the City of Nome, such as: 1. Organic Rankine Cycle generators converting parts of the exhaust gas heat to electricity. vam Exhaust gas boller with steam turbine to convert part of the exhaust gas to electricity. ae Stirling engine driven generator to convert part of the exhaust gas heat to electricity. 4a, Etch 28 These options can be feasible In areas where no other use for the heat avallable can be found. However, they normally do not utIllIize any Jacket heat, and thelr conversion efficiency Is quite low. Option 2 Is found on numerous ships and In several larger diesel power plants around the world. In such systems, conversion ratios of up to 19 kWh per gallon have been experienced. Such efficiencies are, nevertheless, not realistic for a load of the magnitude found In Nome. 29 4 Other Considerations O ENERGY STORAGE O RESERVE CAPACITY REQUIREMENTS O WATER TANK STORAGE SECTION & - OTHER CONSIDERATIONS 4.1 GENERAL The need for Increased generating capacity could be somewhat reduced If varlous peak shaving/load management procedures were Introduced. Such measures could be implemented In_ public bulldings and possibly larger privately owned bulldings. The reduced peak loads from the larger consumers would reduce the overall peak loads felt at the power plant. However, no really drastic peak load reductions should be expected in Nome, as the number of large consumers is limited. Energy conservation in general in all public bulldings would have fuel conserving as well -as a peak shaving effect and could thus be highly beneficial to the City of Nome. 4.2 ENERGY STORAGE At this time, storing diesel generated electricity cannot be considered practical or feasible. An illustration of this would be that elght (8) hours of Nome's electricIty demand would require approximately $2,500,000 worth of storage equipment. Losses would be up to 50 percent. Also, the load characteristics In Nome do not call for storage. Thermal storage Is, on the other hand, quite possible and feasible, and Is being widely used In numerous locations. For large scale thermal storage tn connection with cogeneration, hot water tanks have been In use in Europe since World War II. These systems are normally used In connection with peak load power plants that operate during the day only. Over a 12 to 15 hour perlod, the tank Is heated to 205°F by waste heat. At 30 night the power plant Is shut down and the dIstrict heating demand Is supplied by the storage tank, which Is gradually cooled to)! 150° FR. The storage tank utIlizes the ability of water to maintain well defined boundaries between layers of different temperatures; thus supply temperatures can be _ kept fairly constant. Thermal storage tanks have been constructed In all sizes ranging from 55 gallon residential type storage tanks to multi million gallon tanks bullt In connection with large coal fired power Plants. Thermal storage will not serve any purpose [In Nome as long as surplus waste heat Is available at all times. 4.3 RESERVE CAPACITY REQUIREMENTS No State statutes exist concerning reserve capacity In Nome. However, according to Reference (4) It Is considered good Practice to have enough reserve capacity to be able to meet peak load demand even with the largest unit out of service. At this time, the generating units In Nome are capable of delivering approximately 125 percent of the peak load, even with the largest unit (the EMD) our of service. This should not be viewed as excess capacity. As mentioned In Section 1.1, most of the existing units are quite old. Thus their availability could, at times, be limited due to long lead times on spare parts. In order to be prepared fer future replacement and/or capacity expansion, the CIty of Nome should prepare a detailed plan for this. This plan should take into account waste heat recovery considerations and should also Include fast relief measures to come In to effect should a total breakdown or longer lasting unavailability of some of the units occur. In addition, this plan should address the possible relocation of the major part of the generating capacity away from the flood plain. 31 4.4 WATER TANK LEAKAGE The existing water tank at the power plant has developed serious leaks which are estimated at 20 gallons per_ minute In Reference (5). This Is about 7.6 percent of the total water consumption. Thus from a water resource standpoint, it can be considered a serlous problem. From a heat stand point, It does not represent any problem as It only requires 41 kW to heat the water lost from the tank. CNormal jacket water heat from one 600 kW Cooper Bessemer is about 456 kW.) As long as most waste heat Is not utilized at all, this heat cannot be sald to represent any value.. If, however, at some polInt of time all waste heat was utIlized, this heat would be able to replace approximately 10,000 gallons of ol! per year. ae. . Economic Analysis O COST OF OPTIONS ' . © BENIFITS V.S. COSTS SECTION 5 - ECONOMIC ANALYSIS 5.1 GENERAL The estimates In this sectlon are based on sketches of project concepts, and thus they should be used with caution. As no preliminary designs have been made at this’ point, several parameters could very well change. The numbers In this section should only be used to give an understanding of the order of magnitude for the various projects. The major purpose has been to Identify the most feasible options for recapture and use of waste heat In Nome today and, for this purpose, the accuracy Is deemed sufficient. Estimates have been made of the economic benefits from the waste heat use options based on a fuel ofl price of $1.35 per gallon and a real Interest of 5.5 percent per annum. CFuel ofl Inflation Is assumed to be equivalent to general inflation.) Operation and maintenance costs are based on the capital cost of the project, the complexity of the system, and the estimated life time of the system. Thus for each project, operation and malntenance costs will appear as an estimated percentage of the capital cost of the project. 33 5.2 SUMMARIZED COST ESTIMATES Belmont Point Plant Conversion, 1,000 kW water heating capacity. (The present average load is 453 kW.) Estimated cost Installed: $ 45,000 Nome/Beltz High School Generator, 800 kW diesel generator with jacket water waste heat recapture. Estimated costs: Diesel Generator $ 250,000 Installation, Switchgear, Etc. 300,000 Waste Heat Recapture System Installed $ 250,000 Total Cost Installed $ 800,000 Snake River Point Power Plant Conversion, recapture of waste heat for In-plant use with oll fired back up boiler. Heating system with baseboard and unit heaters. Estimated Cost: $ 35,000 Snake River Point District Heating Loop, recapture of waste heat from power plant for heating warehouses and garages In power plant vicinity. Project to Include connections to existing heating systems and Installation of unit heaters In previously non heated structures. Estimated Cost: $ 120,000 34 Alrport District Heating Loop, recapture of waste heat from power plant for use In heated - bulldings at the alrport. Project to Include connections to exIsting heating systems. Estimated Costs: Downtown District Heating Loop, recapture of all heat from Belmont Point power plant, connection to hospital, school, and other larger bulldings along Bering Street and Front Street via double 6-Inch district heating main lines. System to be prepared for future expansion. Estimated Cost: Greenhouse, connected to Snake River power plant which provides heat necessary for the growing of common vegetables. Project to Include l-acre greenhouse. Estimated Cost: 35 $ 310,000 $1,800,000 $5,000,000 5.3 BENEFITS VS. COSTS Belmont Polnt Plant Converstion Assuming that this conversion will allow for 5,000 hours of operation per year of the Belmont Point plant as compared to the current 2,000 hours per year, the load transfer to this more efficient unit will give an annual fuel savings of approximately 28,000 gallons of fuel oll. No operation and maintenance savings here have been taken Into account. Project Cost: $ 45,000 Annual Fuel Saving 28,000 Gallons Each $1.35: 37,800 Pay Back Time: 1 - 2 Years 36 Nome/Beltz High School Generator It Is anticipated that this unit Is equivalent to WartsIila Diesel CCummins) and thus delivers approximately 800 kW at a kwh-per-gallon ratio of 15.2. It is also anticipated that this unit Is on-line 90 percent of the time with full output. This willl provide the school with approximately 75 percent of Its heating needs. The school's heating o!l1 budget for 1983 Is assumed to be $196,000. As shown In Section 5.2, Installation costs are estimated at $300,000. Of this sum, $50,000 Is assumed to be added cost from the remote location. As the waste heat recapture system Is estimated at $250,000, the total added cost as compared to adding an equivalent diesel generator to the existing power plant will be approximately $300,000. Operation and maintenance costs are not belleved to Increase as compared to usIng existing diesels. Project Cost: $ 300,000 Fuel oll savings at the high School 0.75 x $196,000: 147,000 Fuel oll savings from Increased efficiency as compared to average efficiency Cadjusted for increased line losses): 35,200 gallons of fuel oll, each $1.35: 47,000 Savings per Year: 194,000 Pay Back Time: 1 - 2 Years 37 Snake River Point Power Plant Conversion No added operation and maintenance costs have been anticipated. Project Cost: $ 35,000 Electricity Savings (based on $0.15 per kWh): 11,000 Pay Back Time: 3 - & Years Snake River Point District Heating Loop Operation and maintenance costs are assumed to be 2 percent of the project cost. Fuel savings are based on 21,000 square feet, each utilizing 75,000 BTU per year. This corresponds to an Indoor temperature of 50°F In the heated garages. Savings from hot lines are based on five vehicles on 1.5 kW hot lines 2,000 hours per year. Project Cost: $ 120,000 Operation and Maintenance: 2,400 Fuel O11 Savings; 15,200 gallons, each $1.35: 20,520 Hot Line Savings; 150,000 kWh, each $0.15: 2,250 Total Savings per Year: / $ 20,400 Pay Back Time: 7 - 8 Years 38 Alrport District Heating Loop Operation and maintenance costs are assumed to be 2 percent of the project costs. Energy savings are based on 25,000 square feet, each utilizing 120,000 BTU per year. Project Cost: $ 310,000 Fuel Savings per Year: 29,000 Gallons, each $1.35: 39,200 Operation and Malntenance Costs, 2 % of $310,000: 6,200 Total Savings per Year: $ 33,000 Pay Back Time: . 13 - 14 Years Downtown District Heating Loop Anticipated operation and maintenance costs are 5 percent of the project cost due to the complexity of the system. It Is assumed that the Belmont Point power plant Is In operation 90 percent of the time, and that on a yearly basis 60 percent of all heat from the plant is utilized. The average electrical load on EMD Is estimated at 75 percent. Project Cost: $1,900,000 Operation and Maintenance Cost per Year: 95,000 Fuel Savings per Year; 460,000 Gallons, each $1.35: 621,000 Total Savings Per Year: 526,000 Pay Back Time: 4 - 5 Years 39 Greenhouse Project The estimated costs for a complete l-acre greenhouse (50 percent of Reference (3) estimate): $2,720,000 Value of Crop Per Year: 473,000 Operation and Maintenance; 5 Men Full Time: 180,000 Total Annual Savings: $ 293,000 Pay Back Time: 13 - 14 Years Expenses for light, seeds, fertilizer, etc. have not been taken Into account. The project cost has been estimated at only 50 percent of the Reference (3) estimate. 5.4 SUMMARY PAY OIL DIS- SAVINGS BACK PLACE- PROJECT PROJECT COST PER YEAR TIME MENT $/Year Years Gals/Yr Belmont Pt. Conversion $ 45,000 $ 37,800 1-2 28,000 Nome/Beltz High School 300,000 194,000 = 2 144,000 Snake River Pt. Plant Conversion 35,000 11,000 3-4 5,600 Snake River Pt. District Heat 120,000 20,400 7-8 16,300 Airport District Heat 310,000 33,000 13 - 14 29,000 Downtown District Heat 1,900,000 526,000 4-5 460,000 Greenhouse 2,730,000 293,000 13 - 14 -0- 40 Conclusions & Recommendations SECTION 6 - CONCLUSIONS AND RECOMMENDATIONS 6.1 GENERAL CONCLUSIONS From the previous” section, It can be concluded that’ the greenhouse option and the alrport district heating loop seem to be less than feasible. The poor feasibility of the greenhouse project Is caused by the very high construction cost and the Crelatively) low price of vegetables flown In from the Lower 48. The distance form the alrport to the Snake River power plant and the relatively limited heating demand at the airport limit the feasibility of this project. In-plant use of the waste heat form the Snake River power plant seems to be the only viable alternative. This project Is of limited magnitude and, In spite of a short pay back time, the savings assoclated with this project will not have any significant economic Impact In Nome. The construction of a limited district heating loop to serve the Snake River plant vicinity seems to have a somewhat questionable feasibility. This Its caused by the relatively limited heating load from these bulldings. Considering the standard of some of the buildings, there seems to be a more feasible means of conserving energy such as Insulation and weatherstripping. The most feasible projects at this time seem to be: I. Belmont Point conversion to heat city water. 2. Installation of a remote diesel generator at’ the Nome/Beltz HIgh School. 41 3. Snake River Point plant conversion to use waste heat for heating the power plant. 4, Bering Street / Front Street district heating loop. The two power plant conversion projects are minor projects with minor economic Impact. The remote generator and the downtown district heating project are medium and large projects with significant potential benefits to Nome. 6.2 RECOMMENDATIONS Based on the previous sections, the following Is recommended to the Board of Nome JolInt Utilities: Ls Move ahead with design and construction of the Belmont Point power plant conversion to heat city water. 2. Move ahead with design and constriction of the Snake River power plant conversion to heat the power plant using waste heat. 3. Move ahead with design and Cif funds can be made avallable) construction of a remote generator at the Nome/Beltz High School. 4, Move ahead with preliminary design, detailed cost estimate, and In depth feasibility analysis of the downtown district heating project with utilization of waste heat from the Belmont Point power plant. 42 Appendices | O PROFILE FOR DISTRICT HEATING O PROFILE FOR COGENERATION APPENDIX A — TECHNOLOGY PROFILES FOR DISTRICT HEATING GENERAL DESCRIPTION District heating Is a collective heating system, supplylIng energy for space heating purposes and water heating In urban communities. The system Is comprised of three elements: Cla central heat source, (€2) a piping system, and (3) consumer equipment. The idea was born In the United States and has been In commercial use In many parts of the work since the beginning of this century. Having fewer fossil fuels, the Northern European countries have developed hot water district heating systems and proved them to be _ economical, efficient, and profitable. Initially steam was distributed, but developments showed that hot water was a more convenient heat medium, offering many technical and economical advantages. The origtinal background for establishing the schemes was a wish to achieve a greater comfort, rather than conserving energy. However, an important Improvement of the environment was achieved as a number of inadequate Individual stoves were replaced by one single efficient heat source. For example, in Denmark today more than 400 schemes serve approx- imately 750,000 homes all over the country. Approximately 350 of these schemes are privately owned cooperatives serving mainly the small towns and villages. Thus a great part of these serve less than a few hundred one-family houses. Also many communities In Greenland have district heating schemes utilizing waste heat from power plants. A district heating network consists of an Insulated, double pipe system connecting the Individual users with one or more central heat sources. From the heating stations, hot water of approxi- mately 160°F Is sent out through the flow pipe system. In the consumers! houses, the heat content of the water Is released in the heating systems, and water of approximately 100°F to 160°F returns through the return pipe system for reheating In the station. Surplus heat from thermal power plants Cdlesel engines, gas, or steam turbine engines) offers a big potential for dlIstrict heating and Is easy to recover at low cost, depending on the system and Installation. Boller stations can be designed for combustion of coal, oll, gas, wood waste, or even straw, If available. Opposed to small Individual boilers, such stations can utilize cheaper qualities of fuels, e.g. heavy fuel oll, and they may be desIgned for a combination of fuels In order to reduce the dependency on one particular fuel. Also, Incineration plants for household garbage or Industrial waste offer a heating potential by which a double purpose Is achieved: solving a refuse and an energy problem at the same time. A district heating scheme Is capital Intensive, but a community operating such a facility which serves a large number of consumers can, contrary to the Individual, afford to Install specialized equipment for utilization of various kinds of low- grade fuels such as heavy fuel oll, local coal, waste products, or even waste heat. In other words, It Is possible to reduce the consumption of imported, highly refined and consequently costly fuels (which are the types of fuel Individual heat consumers use in their small heating plants), and replace these by local, lowgrade, cheap alternatives which can only be used In large scale systems. In this way, a higher degree of flexibility and Independence can be achieved. PERFORMANCE CHARACTERISTICS A modern low-temperature, water-based district heating system offers high flexibllity, as almost any fuel, combustible waste material, or waste heat source may be converted In to useful energy. The waste heat or central heat source Is usually a heat-only boller, or an electrical power plant which has been converted for cogeneration. Cogeneration allows the reject heat from electrical generation modes to be used for district heating. Cogeneration Increases a power plant's’ overall efficiency, resulting In substantial savings and making the performance benefit ratio high for cogeneration district heating systems. SUMMARY The eventual Installation of a hot water district heating system In Nome may result In the savings of many dollars presently being expended for business and Individual home heating. The existing diesel electric plant producing electricity will be more efficient with cogeneration, the joint production of thermal and electric products. District heating Is not IImited to a single fuel source. Therefore, Individual boilers fired by oll, wood, coal, and refuse could be considered for Nome. District heating has the following additional advantages: 1. Elimination of consumer handling and storage of fuel. as Reduction of pollution from burning oll. 3. Rellability of heat delivery. polarconsult IN - (to willis fe = 3 Th ~ OUTLINE OF A | 2 DISTRICT HEATING / il | oe SCHEME HEAT INPUT FROM: \ 1. Power plant 2. Boiler station 3. Incinerator J 4 5 6 . Industry . Geothermal energy / . Sewage system/ heat pump J 7. Solar collector WwW = APPENDIX B - TECHNOLOGY PROFILE FOR COGENERATION GENERAL In cogeneration systems, electrical or mechanical energy and useful thermal energy are produced simultaneously. Such improved efficiency systems use a combInat lon of mechanisms to utIlize more of the heat energy produced when conventional fuels are burned than Is possible with any existing single system. Using cogeneration rather than separate systems to produce heat and electricity will yleld considerable fuel savings. Production of efficiency generating electricity Is 22 to 34 percent and recover- able heat Is 43 to 63 percent, permitting total system efficiency of 65 percent to 85 percent in cogeneration cycles. Cogeneration systems Include dual-purpose power plants, waste heat utilization systems, certain types of district heating, and total energy systems. Such systems have been applied since the late 1880's and, In the United States, have been used much more widely In the past than they are today. In the early 1900's, most U.S. Industrial plants generated thelr own electricity, and many used the exhaust steam for Industrial processes. Many utIlIty companies’ supplied cogenerated steam to large Industrial users and densely populated urban areas. By 1909, an estimated 150 utility companies were providing district heating. Cogeneration operations In the United States declined largely because of the avallability and low cost of natural gas heating and of relatively low-cost rellable supplles of electrical power from large generation plants located In sites remote from densely populated areas. TYRES OF SYSTEMS There are two fundamental types of cogeneration systems, topping and bottoming, differentiated on the basis of whether electrical Cor mechanical) energy or thermal energy Is produced first. Ina topping system, electricity or mechanical power is_ produced first, and the thermal exhaust from the turbine Is used as Industrial process heat, for space heating, or In other appli- cations. The topping cycle Is the common choice for utility and Industrial applications. In a bottoming system, thermal energy for process use (such as steel-reheat furnaces, glass kilns, and alumInum-remelt furnaces) Is produced first, then the waste heat Is recovered as an energy source for generating electricity or more mechanical power. Converting a large part of the low temperature process exhaust to useful work limits the application of bottoming cycles. Choosing a system depends on the balance of thermal energy and electrical Cmechanical) power needed, and the level of waste heat available. PERFORMANCE CHARACTERISTICS Topping Systems Steam turbines CRankine engines), gas turbines (Brayton engines), and diesel engines are the three primary heat engines used In cogeneration topping systems. A steam turbine system consists of a boller and a backpressure turbine. The boller can be fired by ol11, natural gas, coal, wood, or Industrial by-products and wastes. The turbine drives an electric generator and provides exhaust steam, still under pressure, for heating purposes. The overall efficiency of steam turbine cogeneration systems generally ranges from 65 to 85 percent. A_gas turbine combined cycle system consists of a gas turbine waste heat recovery boller and steam turbine generator. Natural gas or light petroleum products (Cdistillate olls) are used as fuels, and the combustion gases produced are used In the gas turbIne to provide the mechanical shaft power that drives an electrical generator. The exhaust heat from the gas turbine €850° to 950°F) Is recovered In the waste heat boller to produce high pressure steam pliped to the steam turbine generator. The steam turbine may be the back pressure or condensing type. Condensing of the turbIne exhaust can be utilized In district heating systems or for process. requirements. The efficiency of gas turbines Is sensitive to Inlet alr temper- ature; the lower the ambient temperature, the higher the units power output, f.e., a simple cycle gas turbine that will produce 4,000 kW at 60°F can produce 4,750 kW at -20°F. A diesel _ system, consisting of a diesel engine and a waste heat recovery unit, uses natural gas or distillate oil. The combustion of fuel In the engine ylelds the mechanical power that drives an electrical generator. Overall efficiencies of 75 to 85 percent have been demonstrated. The engine exhaust can provide process heat or low-pressure process’ steam,, but requires carefully controlled water treatment equipment. For process heating applications, the exhaust Cat about 900°F) has been used. Process steam of about 100 psi Is generated In boilers that recover heat from the engine exhaust. In addition to the engine exhaust, heat can be recovered from the water-cooled engine Jacket; low pressure steam is produced, or water for district heating can be generated at 190 to 200°F through a_ heat exchanger. Production of steam from exhaust and jacket water has not enjoyed as much success In Alaska. Maintenance on steam waste heat recovery systems Is higher than the other topping systems. Typically, minor repairs are required every 7,000 to 10,000 hours, and major overhauls every 20,000 to 30,000 hours. Bottoming Systems All bottoming systems are based on the Rankine cycle for waste heat recovery. Two types of Rankine cycles are used: steam and organic. Steam bottoming systems recover heat rejected from thermal processes at high temperatures. Steam engines operate within a heat temperature range of 300 to 1,000°F with thermal efficiencies of 14 to 36 percent, and generally have capacities of over 500 kW. Bottoming cycles that use organic working flulds to recover thermal energy are avallable In limited sizes, ranging from 1,000 kW. BEcause these operate at lower temperatures (195 to 340°F), such systems can recover lower temperature waste heat. These systems have low efficiencies. Work on bottoming systems Is focused on further development of organic-fluld Rankine cycles. Because the organic fluids vaporize at temperatures below 212°F, and are more efficient than water at higher temperatures, it should be possible to develop high performance organic Rankine cycles. Combined-Cycle Systems Combined cycle systems are comprised of two or more different thermodynamic cycles connected together In a way to gain maximum effictlency from the primary heat source, usually to generate electricity. However, turbine exhaust Is readily used for district heating. Such systems using coal or coal-derived fuels offer significant Improvements over conventional systems for electric power generation In terms of Increased efficiency, potentially lower cost, and reduced environmental impact. The concept of this advanced system Is to burn coal or coal- derived gaseous or liquid fuels in air to produce a high temperature as 2,600°F or higher before expanding It through the turbIne to produce electricity. After expansion, remaining hot gases can be used to generate steam In a conventional steam turbine plant to produce additional electricity. The open-cycle gas turbIne/steam system forms a combined cycle power plant with potentially greater efficiency than today's standard steam plant. Integrating a combIned-cycle system with a low-Btu coal gasifier appears to be most promising from the standpoints of efficiency, cost of electricity, and emissions. Advances In combined-cycle power plants focus on high-temperature gas turbines combined with steam engines. Le Open-Cycle Gas Turbine Combined Cycles Open-cycle gas turbines that burn natural gas and distillate fuels are used commonly for utility peak load applications. CombIined-cycle power plants couple such gas-turbines with steam- turbine technology to reduce the cost of electricity. There ts one oll-fired and two gas-fired combined-cycle plants currently In utIi lity service In Alaska. Relatively low capital Investment/kW, higher conversion efficlency, capability for base and Intermediate load service, and ease of waste heat utilization are factors’ making investment In new combined-cycle units increasingly attractIve to electric utilities. The advantage of combined-cycle systems Is represented by rellabillity due to the use of two tried and proven technologies. System efficlencles can reach 85 percent with waste heat utilization of the steam turbine exhaust In a district heating system or other heating process. Rellabillity can be Improved by arranging the waste heat recovery boiler for auxillary firing. Generating plants in the Anchorage area using combined cycle technology generating electricity and heating city water has a heat rate at full loaf on both units of 7,400 Btu/kW. BIBLIOGRAPHY Alaska Power Authority, "Kotzebue Coal-Fired Cogeneration, District Heating and Other Energy Alternatives FeasIbIility Assessment" Anchorage, November 1982 "Coastal Management Program" Background Report City of Nome, July 1981 Alaska Department of Commerce and Economic Development, Division of Energy and Power Development, "Rural Waste Heat Capture for Alaskan Agriculture" Anchorage, November 1981 Personal Communication, Alaska Public Utilities Commission Representative April 29, 1982 City of Nome, "Water and Sewer Master Plan Update" Nome, November 1982 CONCEPTUAL ESTIMATE ENERGY WASTE HEAT PROGRAM FOR NOME, ALASKA Cost Consultant Engineers HMS, Inc. 4103 Minnesota Drive Anchorage, Alaska 99503 Polarconsult Alaska, Inc. 2735 East Tudor Road, Suite 201 Anchorage, Alaska 99507 (907) 561-1653 May 31, 1983 CONCEPTUAL ESTIMATE ENERGY WASTE HEAT PROGRAM FOR NOME, ALASKA Cost Consultant Engineers HMS, Inc. 4103 Minnesota Drive Anchorage, Alaska 99503 Polarconsult Alaska, Inc. 2735 East Tudor Road, Suite 201 Anchorage, Alaska 99507 (907) 561-1653 May 31, 1983 NOME ENERGY WASTE HEAT PROGRAM PAGE 1 CONCEPTUAL ESTIMATE MAY 31, 1983 Notes R tn the ti £ This © 1 Estimat The attached estimate has been prepared from notes and descriptions provided by Polarconsult Alaska, Inc. of Anchorage, Alaska on May 27, 1983. ‘. The estimate is based on current construction costs and has been projected to reflect a competitive bidding date of August 1983 and assumes that the DOT/PF current contract for installation of utilities will run simultaneously in order that: these pipes may be installed at the same time (prepurchase of pipe and insulation for the city's distribution needs have been considered in this estimate). A two and one half percent (2-1/2%) contingency has been included for escalation as well as a ten percent (10%) contingency for design changes. ; / ay This is a construction cost estimate and does not include for consultants' fees, administrative or other off-site costs. NOME ENERGY WASTE HEAT PROGRAM CONCEPTUAL ESTIMATE 1. Adaptation o . $ 133,000 2. City Distribution 671,100 3. Supply to 12 Facilities 528,000 4. EL seay// 16,00 oe oe, Requirements and Profi 293 ,90: 6. —— 2077500 catingrie Estimate of Obable Construction PAGE 2 MAY 31, 1983 NOME ENERGY WASTE HEAT PROGRAM CONCEPTUAL ESTIMATE PAGE 3 MAY 31, 1983 Cut into existing return pipes, make tee connections including valves and pipework in forming new loop for waste heat converter Circulation pumps Heat exchanger complete with connections Glycol and make-up system complete with pumps Expansion tanks with airtrol unit Large circulation pumps Insulated piping including fittings, 8-in. diameter to 2-in. diameter - Valves Controls Sundry requirements and alterations 400 bi hi gp SS g Fy 3 10,000 3,000 50,000 5,000 3,000 8,000 18,000 6,000 10,000 20,000 TOTAL ESTIMATED COST: 133,000 NOME ENERGY WASTE HEAT PROGRAM : PAGE 4 CONCEPTUAL ESTIMATE MAY 31, 1983 2. CITY DISTRIBUTION QUANTITY UNIT ESTIMATED COST Arctic pipe comprising two each 8-in. diameter flow and return lines each with ; factory applied urethane and a polyurethane ; jacket with trench and backfilling by others under a separate contract with DOT/PF ; 2,500 LF 231,600 Ditto with (2 each) 6-in. diameter flow and ; . return lines y / ~ 3,350 . LF 257,300 Ditto with (2 each) 4-in. diameter flow and ie Ss, return lines 950 IF. 61,600 Service lateral to 12 facilities ditto 3-in. — to 2-in. diameter pipes | 1,200 LF 70,600 Expansion loops ; 10 EA 10,000 Sundry support and other requirements LS -—- ~~ 10,000 Remote circulation pumps including electrical connection and housing 2 EA 30,000 hy | TOTAL ESTIMATED COST: 671, rae NOME ENERGY WASTE HEAT PROGRAM PAGE 5 CONCEPTUAL ESTIMATE MAY 31, 1983 3. SUPPLY TO 12 FACILITIES Cut existing pipes and move existing pumps 2 FA 1,000 Pump a 1 FA 2,500 Flat plate heat exchanger plus-or-minus . 500 MBUH ; ol FA 15,000 Drip pan 1 FA 200 4-in. copper pipes, fittings, and insulation 7 260 “LF 11,100 3-in. ditto “iso 640 5-in. to 4-in. reducer 2 FA 420 4-in. gate valve 7 FA 2,660 4-in. drain valve 2 EA 480 4-in. strainer valve 1 FA 250 4-in. balance valve il FA “ 350 Pressure relief valve 2 ra EA 240 Manual air vent 6° f FA 540 Pressure gauge and cock “2 FA 220 Thermometer 4 EA 720 Connect to existing pipes 2 FA 160 Electrical connections 1 Lot 2,000 Subtotal: "38, 480 TOTAL ESTIMATED COST: continued NOME ENERGY WASTE HEAT PROGRAM PAGE 6 CONCEPTUAL ESTIMATE MAY 31, 1983 3. SUPPLY TO 12 FACILITIES Subtotal Brought Forward: LA 38,480 B.W.1I.C.. for installation of exchanger and piping 2 5,520 Subtotal: NY 44,000 ‘ x 12 units NOME ENERGY WASTE HEAT PROGRAM PAGE 7 CONCEPTUAL ESTIMATE MAY 31, 1983 QUANTITY UNIT ESTIMATED COST Connection to existing mains ; 1 EA 2,500 Motor control panel with starters and | disconnectors 5 1 FA 6,000 Connect to equipment: Single phase i 5 FA 1,000 Three phase ’ ji i) 10 FA 3,500 Alarm system peer ‘1. tor ‘, 3,000 Zo ya . * NOME ENERGY WASTE HEAT PROGRAM PAGE 8 CONCEPTUAL ESTIMATE MAY 31, 1983 5. GENERAL REQUIREMENTS AND PROFIT QUANTITY UNIT ESTIMATED COST Mobilization and transportation . LS = 80,000 “ — Operation costs is 6 MTHS 66,000 Overhead and profit “ “10 g 147,900 . \ 4 TOTAL ESTIMATED COST: 293 ,900 °. NOME ENERGY WASTE HEAT PROGRAM CONCEPTUAL ESTIMATE The estimator's allowance for architectural and engineering requirements that are not apparent at an early level of se documentation Escalation es fone The assessment of inflation on the project © cost from the date of the estimate to " contract commencement (August 1983 bid date) ~ 10 2.5 PAGE 9 MAY 31, 1983 ESTIMATED COST 162,700 44,800 TOTAL ESTIMATED COST: 207, 500