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HomeMy WebLinkAboutMetlakatla Waste Heat Project Agreements, Contracts, & Budget 1988Version: 88/3/16/1200 METLAKATLA WASTE HEAT SYSTEM FEASIBILITY ANALYSIS TABLE OF CONTENTS: EXECUTIVE SUMMARY 1.0 Introduction and Background Conclusions RR NP FACILITY DESCRIPTION i) ° General Power plant The School facilities The Loussac Activity Center The Council Chambers The Clinic The Youth Center The Head Start Building The Townhall The Senior Center The Low Income Housing NNNNNNNNNM FPOWOONDUNFWNHEH NN PR WASTE HEAT SYSTEM CONCEPTS Ww Oo General 3.1 Concept Al 3.2 Concept A2 3.3 Concept A3 3.4 Concept Bl 3.5 Concept B2 3.6 COST ESTIMATES 4.0 General 4.1 Concept Al 4.2 Concept A2 4.3 Concept A3 4.4 Concept Bl 4.5 Concept B2 4.6 ECONOMIC ANALYSIS 5.0 General 5.1 Concept Al 5.2 Concept A2 Concept A3 Concept Bl Concept B2 CONCLUSIONS General Discussions Conclusions aann ana DAuFw NO 1.0 EXECUTIVE SUMMARY 1.1 Introduction and Background In the fall of 1987 Metlakatla Light and Power (ML&P) requested that the Alaska Power Authority investigate the feasibility of utilizing waste heat from its power plant for heating public buildings in Metlakatla including the local schools. Power Authority staff made a visit to Metlakatla where the facilities were audited for compatibility with waste heat recovery systems. Based on the information gathered, five concepts for waste heat recovery systems were developed. For each concept a preliminary cost estimate and the pay back time were calculated with a Lotus 1-2-3 program using relevant climatic and statistical data. This program simulates the operation of a waste heat recapture system over the life span of the project. This study does not include detailed engineering data such as soils conditions, local availability of skilled labor and local experience in undertaking construction projects. Thus, the cost estimates should be used with great caution. The economic analysis of system performance over the life span of the project is fairly accurate, provided that prudent maintenance is performed on the system. 1.2 Conclusions It is expected that the City would realize substantial savings in fuel and some savings in maintenance expenses from this project. Also, it is expected that ML&P would realize some savings from reduced station service loads. Maintenance savings have not been quantified and consequently have no effect on the calculated pay- back time. Annual operations and maintenance costs have been estimated at 2% of the capital cost of the project. No technical obstacles should prevent the installation of a waste heat recapture system utilizing waste heat from the power plant in a number of buildings. Provided that operational procedures are not changed drastically in the power plant, installation of a waste heat recapture system appears technically feasible. However, due to the relatively low price of fuel, and due to the length of the necessary distribution system, the economical feasibility appears unsatisfactory at this time. The five concepts show pay-back times of approximately 24, 22, 18, 26, and 30 years, when an annual fuel price escalation of 2% is used in conjunction with a real interest rate of 4% and a fuel cost of 0.80$/gallon. In accordance with the feasibility outlined above, it is recommended that the project be postponed until such times when the potential fuel savings will provide for a pay back time of no more than 10 years. As an alternative means of reducing operating costs for some of the buildings involved, it is recommended that these buildings be audited for potential energy efficiency improvements. Especially the Loussac Activity Center has a great potential for efficiency improvements. Pump and fan operating costs can be greatly reduced through optimization and heating costs can be reduced through a connection to the oil fired heating system installed in the high school. Also, it should be noted that the current plans for electric heating systems in the planned senior citizen center and low inclome housing unit will provide for very high future operating costs. Such plans appear to ignore economic realities and they should be changed. 2.0 FACILITY DESCRIPTION 2.1 General This facility description is limited to facilities and items that can be considered relevant in connection with waste heat recovery in Metlakatla. 2.2 Power Plant. The power plant is a well built and well maintained facility incorporating a 4,000 kw Caterpillar 3612 generating set. Waste heat recapture equipment has already been incorporated into the power plant with a horizontal core radiator providing automatic back up cooling capacity in case the waste heat recovery system is unable to utilize all the heat generated. 2.3 The School Facilities The school facilities to be connected to a potential waste heat recovery system include the upper and lower elementary schools, the junior high school, and the high school. These buildings all incorporate heating systems, which with some modifications will be able to accomodate waste heat. Such modifications may include the addition of additional radiation surface, installation of heat exchangers, and replacement of some controls. Annual fuel consumption for these buildings has been estimated at 34,349 gallons. 2.4 The Loussac Activity Center The heating system in this building is all electric with an estimated electrical consumption for heating purposes of 570,000 kwh. This has been converted to a fuel consumption of 19,500 gallons for the purpose of this study and consequently has been assigned a value of $15,600 using a fuel price of $0.80 per gallon. While it may be argued that the cost of the electric power used for heating is far higher, the actual value of the heat consumed is only $15,600. This is due the fact that the activity center could be provided with oil based heat either through the installation of a single boiler in the building or through an interconnection to the high school's oil fired heating system. Both conversions would be relatively inexpensive and should be considered independent of this study. 2.5 The Council Chambers It has been estimated that this building will use waste heat according to an estimated annual fuel consumption of 3,500 gallons. 2.6 The Clinic It has been estimated that this building will use waste heat according to an estimated annual fuel consumption of 1,500 gallons. 2.7 The Youth Center It has been estimated that this building will use waste heat according to an estimated annual fuel consumption of 1,500 gallons. 2.8 The Head Start Building It has been estimated that this building will use waste heat according to an estimated annual fuel consumption of 1,500 gallons. 2.9 The Town Hall The utilization of waste heat in the town hall would include the installation of separate unit heaters connected directly to the waste heat system. The existing heating system would serve as back up to supply heat at times when the waste heat system did not have sufficient capacity. It has been estimated that this building will use waste heat according to an estimated annual fuel consumption of 5,000 gallons. 2.10 The Senior Center The connection of this building to waste heat will require the installation of a water based heating system to replace the planned all electric heating system. The feasibility of installing all electric heat in a new building in Metlakatla must be questioned. While the initial installation costs will be lower for an all electric heating system, even the most basic life cycle cost analysis would reveal that the cost of electric heating over the life of the building will be several times the cost of any other means of heating. The value of heat provided for this building has been estimated to be equivalent to 8,000 gallons of fuel per year. 2.11 The Low Income Housing The connection of this building to waste heat will require the installation of a water based heating system to replace the planned all electric heating system. The feasibility of installing all electric heat in a new building in Metlakatla must be questioned. While the initial installation costs will be lower for an all electric heating system, even the most basic life cycle cost analysis would reveal that the cost of electric heating over the life of the building will be several times the cost of any other means of heating. The value of heat provided for this building has been estimated to be equivalent to 8,000 gallons of fuel per year. 3.0.0 WASTE HEAT SYSTEM CONCEPTS 3.1.0 General Waste heat system concepts that have been investigated in this study are described here. This study does not attempt to investigate all possible waste heat system concepts for use in Metlakatla, but concentrates on alternatives found reasonable as a result of the Power Authority’s experience with waste heat recapture systems. Based on the field date collected, it seems clear to Power Authority staff that several details are pre-determined. Thus the differences between the concepts are limited to pipe routings, the number of buildings connected and to some extent the method of connection. All concepts studied would involve a system using the existing installation of exhaust gas and jacket water waste heat equipment in the power plant. Heat would be delivered to the user buildings through a constant output temperature, variable flow, water based system, which feeds into an underground distribution network. The network would consist of pre-insulated pipe using a steel carrier pipe, high density urethane foam insulation and high density polyethylene jacket pipe. In buildings with hydronic type heating systems, a large flat plate heat exchanger would transfer heat to the boiler return line in the existing heating system. A simple control valve would maintain a pre-set temperature in the existing heating system by limiting the flow in the waste heat recovery system. With this concept the boiler would function as an automatic back up heat source in case insufficient heat was available from the power plant. It is not recommended that heat is metered as "Btu-meters" have proven to be expensive and and somewhat unreliable. As all buildings are supported by the same entity which owns Metlakatla Power and Light, metering will not be necessary. If the display of in-kind contributions to user entities are needed, such displays can reasonably be based on estimates of the amounts of heat delivered. 3.2.0 Concept Al This concept provides heat for all the above mentioned buildings through district heating lines extending from the power plant along Walden Pt. Road, Atkinson Street, past the Head Start Building to the school complex. From here branch lines will connect to the proposed low income housing building and along Hillcrest Street and across to the new senior citizen complex. The main pipe run will most likely be 4" diameter with 2" service lines to the three school boiler rooms and to the activity center, the senior citizen complex, and to the low income housing building. The pipe to the council chambers will also be of 2" diameter and 1" service lines will be installed to all other users. See also attached map A. 3.3.0 Concept A2 This concept will be identical to concept Al with the only difference being the deletion of the connection to the low income housing. 3.4.0 Concept A3 This concept will be identical to concept A2 with the only difference being the deletion of the connection to the senior citizen center. 3.4.0 Concept Bl. As it has been described for concept Al, this concept will also provide heat to the school facilities, the activity center, the council chambers, the clinic, the youth center, the head start building, the townhall, the senior citizen center, and to the low income housing units. As it can be seen from map B, the main line will extend from the power plant across the south end of the chip dump to Airport Road and from there along the new road past the proposed low income housing units to the corner of Skater Lake Road and Eighth Avenue. From here a branch line along Skater Lake Road and Hillcrest Street will connect to the proposed senior citizen center and another branch will supply the school facilities, the activity center, and the town hall. Another branch line will supply the council chambers along with the clinic, the head start building, and the youth center. 3.5.0. Concept B2. This concept is identical to concept Bl with the only difference being the deletion of the connection to the senior citizen center. 4.0 COST ESTIMATES 4.1 General The cost estimates presented in this report are based on _ the following assumptions: a. System design follows Alaska Power Authority standards. b. Construction is performed by City of Metlakatla crews on a "force account" basis with the Alaska Power Authority providing basic engineering, some supervision and inspection, and _ start-up assistance. c. All lines will be buried in existing roads where ever possible and these roads will be re-established according to their prior state. d. Labor rates of approximately $15/hour have been used for cost estimating purposes. Note that all cost estimates are based on preliminary designs only and consequently the cost estimates should be used with great caution. 4.2 Concept Al. Cost estimate: Power plant work $ 5,000 District heating piping 414,533 School facilities installation 41,000 LAC installation 12,500 Clinic, Youth Center, and Head Start 13,500 Council Ch., Senior C., and Low inc. 24,000 Townhall installation 5,500 Net construction $ 516,033 Job indirects, 30% 154,810 10 Construction cost $ 670,843 Overhead, 10% 67,084 Net project cost $ 737,927 Contingency, 15% 110,689 Total cost estimate $ 848,616 4.3 Concept A2. Cost estimate: Power plant work $ 5,000 District heating piping 353,578 School facilities installation 41,000 LAC installation 12,500 Clinic, Youth Center, and Head Start 13,500 Council Ch., and Senior C. 16,000 Townhall installation 5,500 Net construction $ 447,078 Job indirects, 30% 134,123 Construction cost $ 581,201 Overhead, 10% 58,120 Net project cost $ 639,321 Contingency, 15% 95,898 Total cost estimate $ 735,219 4.4 Concept A3. Cost estimate: Power plant work $ 5,000 District heating piping 274,705 11 School facilities installation 41,000 LAC installation 12,500 Clinic, Youth Center, and Head Start 13,500 Council Ch. 8,000 Townhall installation 5,500 Net construction $ 320,466 Job indirects, 30% 96,140 Construction cost $ 416,606 Overhead, 10% 41,661 Net project cost $ 458,267 Contingency, 15% 68,740 Total cost estimate $ 527,007 4.5 Concept Bl. Cost estimate: Power plant work $ 5,000 District heating piping 439,759 School facilities installation 41,000 LAC installation 12,500 Clinic, Youth Center, and Head Start 13,500 Council Ch., Senior C., Low in. 24,000 Townhall installation 5,500 Net construction $ 541,259 Job indirects, 30% 162,378 Construction cost $ 703,637 Overhead, 10% 70,364 Net project cost $ 774,001 Contingency, 15% 116,100 12 Total cost estimate $ 890,101 4.6 Concept B2. Cost estimate: Power plant work $ 5,000 District heating piping 427,753 School facilities installation 41,000 LAC installation 12,500 Clinic, Youth Center, and Head Start 13,500 Council Ch., Low in. 16,000 Townhall installation 5,500 Net construction $ 521,253 Job indirects, 30% 156,376 Construction cost $ 677,629 Overhead, 10% 67,763 Net project cost $ 745,392 Contingency, 15% 111,809 Total cost estimate $ 857,201 13 5.0 ECONOMIC ANALYSIS 5.1 General The economic analysis for the waste heat recapture system concepts addressed in this report was performed using the LOTUS 1-2-3 software and the following methodology: Based on actual power production figures for the diesel generator together with specific technical data for the generator the available waste heat was calculated for each hour during the year. Based on heating degree variations for Metlakatla together with fuel consumption data and operational characteristics provided by the City of Metlakatla the actual heat demand was calculated for each hour of the year. Comparing the available heat and the demand showed how much waste heat was actually utilized. At this point the estimated heat loss for the district heating lines was also taken into account. The waste heat utilized was added up hour by hour for the entire year. With a set of assumptions for load growth over the next 20 years, the same operation was done for each of the next 20 years and the annual fuel savings were derived. Based on current fuel cost and estimated fuel cost escalation together with the cost estimates presented in this report, a cash flow analysis and a pay _ back time were calculated for each of the concepts. Generally speaking, the pay back time indicates the period of time during which the project will have to operate as intended in order to pay off the initial investment. In this study, a discount rate of 4 percent has been used. The discount rate is approximately equal to the difference between the interest rate and the inflation rate. The annual operations and maintenance cost for each concept has been estimated at 2% of the construction cost for general operation and maintenance. (This item will be discussed in greater detail is subsequent sections.) Pay back times are based on the assumption that basic engineering and construction management is provided by the Alaska Power Authority and that all construction efforts are undertaken by the City of Metlakatla on a "force account" basis. 5.2 Concept Al. With the assumptions made, Concept Al shows a pay back time of 24 years. All heating needs for the buildings can be met during the first year of operation and it is anticipated that this waste 14 heat recapture concept would have annual operation and maintenance expenses of $16,972. Operation and maintenance expenses for the boiler systems could be expected to decrease significantly due to the systems being idle. 5.3 Concept A2. With the assumptions made, Concept A2 shows a pay back time of 22 years. All heating needs for the buildings can be met during the first year of operation and it is anticipated that this waste heat recapture concept would have annual operation and maintenance expenses of $14,704. Operation and maintenance expenses for the boiler systems could be expected to decrease significantly due to the systems being idle. 5.4 Concept A3. With the assumptions made, Concept A3 shows a pay back time of 18 years. All heating needs for the buildings can be met during the first year of operation and it is anticipated that this waste heat recapture concept would have annual operation and maintenance expenses of $11,847. Operation and maintenance expenses for the boiler systems could be expected to decrease significantly due to the systems being idle. 5.5 Concept Bl. With the assumptions made, Concept Bl shows a pay back time of 26 years. All heating needs for the buildings can be met during the first year of operation and it is anticipated that this waste heat recapture concept would have annual operation and maintenance expenses of $17,802. Operation and maintenance expenses for the boiler systems could be expected to decrease significantly due to the systems being idle. 5.6 Concept B2. With the assumptions made, Concept B2 shows a pay back time of 30 years. All heating needs for the buildings can be met during the first year of operation and it is anticipated that this waste heat recapture concept would have annual operation and maintenance expenses of $17,144. Operation and maintenance expenses for the boiler systems could be expected to decrease significantly due to the systems being idle. 15 6.0 CONCLUSIONS 6.1 General Discussion The power plant in Metlakatla is very well suited for the utilization of waste heat. District heating lines would be installed preferably in existing roads in order to avoid some of the very difficult soils conditions found around Metlakatla. It should be noted that no soils conditions have been investigated in detail, and consequently it cannot be guaranteed that it will even be possible to install a line through areas such as the chip dump. The cost estimates shown do not reflect any ripping of rocky soils nor do they include back filling with suitable replacement materials. The existing heating systems in the school can be modified for the utilization of waste heat. All systems seem to be capable of operating on medium grade heat, which is what is available from the power plant. Tie-ins in the existing boiler rooms would be fairly easy, as sufficient floor space is available and relatively simple heating systems are in place. All heating systems have been reviewed for compatibility with waste heat recapture systems, and it appears that no major technical obstacles will prevent the utilization of waste heat in the buildings addressed in this report. 6.2 Conclusion It is expected that the City would realize substantial savings in fuel and some savings in maintenance expenses from this project. Also, it is expected that the power plant would realize some savings from reduced station service loads. Maintenance savings have not been quantified and consequently have no effect on the calculated pay-back time. Annual operations and maintenance costs have been estimated at 2% of the capital cost of the project. No technical obstacles should prevent the installation of a waste heat recapture system utilizing waste heat from the power plant in a number of buildings. Provided that operational procedures are not changed drastically in the power plant, installation of a waste heat recapture system appears technically feasible. The concepts are similar in the sense that cost estimates are dominated by the cost of the distribution system. While it may be possible to reduce the cost of the distribution system through efficient installation techniques, it would not be prudent to base the cost estimates and thereby the project on such hopes. From the anticipated time of start up of all concepts, the plant will be capable of providing all the heating needs for all buildings connected. 16 Due to the relatively low price of fuel, and due to the length of the necessary distribution system, the economical feasibility appears unsatisfactory at this time. The five concepts show pay- back times of approximately 24, 22, 18, 26, and 30 years, when an annual fuel price escalation of 2% is used in conjunction with a real interest rate of 4% and a fuel cost of .80$/gallon. With the pay back times listed above, the project does not appear to be feasible at this time. Even if a fuel cost of $1.60 was used, the best alternative (A3) would show a pay back time of 7 years. In accordance with the feasibility demonstrated above, it is recommended that the project be postponed until such times when the potential fuel savings will provide for a pay back time of no more than 10 years. As an alternative means of reducing operating costs for some of the buildings involved, it is recommended that these buildings be audited for potential energy efficiency improvements. Especially the Loussac Activity Center has a great potential for efficiency improvements. Pump and fan operating costs can be greatly reduced through optimization and heating costs can be reduced through a connection to the oil fired high school heating system. 17 Version: 88/3/16/1200 METLAKATLA WASTE HEAT SYSTEM FEASIBILITY ANALYSIS TABLE OF CONTENTS: EXECUTIVE SUMMARY 1.0 Introduction and Background Conclusions BPR Nr FACILITY DESCRIPTION ND °o General Power plant The School facilities The Loussac Activity Center The Council Chambers The Clinic The Youth Center The Head Start Building The Townhall The Senior Center The Low Income Housing NNMONNNNNNND NN PR: : FPODCMYNDAUEWNHE WASTE HEAT SYSTEM CONCEPTS Ww °o General Concept Al Concept A2 Concept A3 Concept Bl Concept B2 WWWWWW DAUFWNrR COST ESTIMATES oO General Concept Al Concept A2 Concept A3 Concept Bl Concept B2 PREEEHE FF DUPWNeE ECONOMIC ANALYSIS 5.0 General Concept Al awn el Concept A2 Concept A3 Concept Bl Concept B2 CONCLUSIONS General Discussions Conclusions wan ano Le el Aufw 1.0 EXECUTIVE SUMMARY 1.1 Introduction and Background In the fall of 1987 Metlakatla Light and Power (ML&P) requested that the Alaska Power Authority investigate the feasibility of utilizing waste heat from its power plant for heating public buildings in Metlakatla including the local _ schools. Power Authority staff made a visit to Metlakatla where the facilities were audited for compatibility with waste heat recovery systems. Based on the information gathered, five concepts for waste heat recovery systems were developed. For each concept a preliminary cost estimate and the pay back time were calculated with a Lotus 1-2-3 program using relevant climatic and statistical data. This program simulates the operation of a waste heat recapture system over the life span of the project. This study does not include detailed engineering data such as soils conditions, local availability of skilled labor and local experience in undertaking construction projects. Thus, the cost estimates should be used with great caution. The economic analysis of system performance over the life span of the project is fairly accurate, provided that prudent maintenance is performed on the system. 1.2 Conclusions It is expected that the City would realize substantial savings in fuel and some savings in maintenance expenses from this project. Also, it is expected that ML&P would realize some savings from reduced station service loads. Maintenance savings have not been quantified and consequently have no effect on the calculated pay- back time. Annual operations and maintenance costs have been estimated at 2% of the capital cost of the project. No technical obstacles should prevent the installation of a waste heat recapture system utilizing waste heat from the power plant in a number of buildings. Provided that operational procedures are not changed drastically in the power plant, installation of a waste heat recapture system appears technically feasible. However, due to the relatively low price of fuel, and due to the length of the necessary distribution system, the economical feasibility appears unsatisfactory at this time. The five concepts show pay-back times of approximately 24, 22, 18, 26, and 30 years, when an annual fuel price escalation of 2% is used in conjunction with a real interest rate of 4% and a fuel cost of 0.80$/gallon. In accordance with the feasibility outlined above, it is recommended that the project be postponed until such times when the potential fuel savings will provide for a pay back time of no more than 10 years. As an alternative means of reducing operating costs for some of the buildings involved, it is recommended that these buildings be audited for potential energy efficiency improvements. Especially the Loussac Activity Center has a great potential for efficiency improvements. Pump and fan operating costs can be greatly reduced through optimization and heating costs can be reduced through a connection to the oil fired heating system installed in the high school. Also, it should be noted that the current plans for electric heating systems in the planned senior citizen center and low inclome housing unit will provide for very high future operating costs. Such plans appear to ignore economic realities and they should be changed. 2.0 FACILITY DESCRIPTION 2.1 General This facility description is limited to facilities and items that can be considered relevant in connection with waste heat recovery in Metlakatla. 2.2 Power Plant. The power plant is a well built and well maintained facility incorporating a 4,000 kw Caterpillar 3612 generating set. Waste heat recapture equipment has already been incorporated into the power plant with a horizontal core radiator providing automatic back up cooling capacity in case the waste heat recovery system is unable to utilize all the heat generated. 2.3 The School Facilities The school facilities to be connected to a potential waste heat recovery system include the upper and lower elementary schools, the junior high school, and the high school. These buildings all incorporate heating systems, which with some modifications will be able to accomodate waste heat. Such modifications may include the addition of additional radiation surface, installation of heat exchangers, and replacement of some controls. Annual fuel consumption for these buildings has been estimated at 34,349 gallons. 2.4 The Loussac Activity Center The heating system in this building is all electric with an estimated electrical consumption for heating purposes of 570,000 kwh. This has been converted to a fuel consumption of 19,500 gallons for the purpose of this study and consequently has been assigned a value of $15,600 using a fuel price of $0.80 per gallon. While it may be argued that the cost of the electric power used for heating is far higher, the actual value of the heat consumed is only $15,600. This is due the fact that the activity center could be provided with oil based heat either through the installation of a single boiler in the building or through an interconnection to the high school's oil fired heating system. Both conversions would be relatively inexpensive and should be considered independent of this study. 2.5 The Council Chambers It has been estimated that this building will use waste heat according to an estimated annual fuel consumption of 3,500 gallons. 2.6 The Clinic It has been estimated that this building will use waste heat according to an estimated annual fuel consumption of 1,500 gallons. 2.7 The Youth Center It has been estimated that this building will use waste heat according to an estimated annual fuel consumption of 1,500 gallons. 2.8 The Head Start Building It has been estimated that this building will use waste heat according to an estimated annual fuel consumption of 1,500 gallons. 2.9 The Town Hall The utilization of waste heat in the town hall would include the installation of separate unit heaters connected directly to the waste heat system. The existing heating system would serve as back up to supply heat at times when the waste heat system did not have sufficient capacity. It has been estimated that this building will use waste heat according to an estimated annual fuel consumption of 5,000 gallons. 2.10 The Senior Center The connection of this building to waste heat will require the installation of a water based heating system to replace the planned all electric heating system. The feasibility of installing all electric heat in a new building in Metlakatla must be questioned. While the initial installation costs will be lower for an all electric heating system, even the most basic life cycle cost analysis would reveal that the cost of electric heating over the life of the building will be several times the cost of any other means of heating. The value of heat provided for this building has been estimated to be equivalent to 8,000 gallons of fuel per year. 2.11 The Low Income Housing The connection of this building to waste heat will require the installation of a water based heating system to replace the planned all electric heating system. The feasibility of installing all electric heat in a new building in Metlakatla must be questioned. While the initial installation costs will be lower for an all electric heating system, even the most basic life cycle cost analysis would reveal that the cost of electric heating over the life of the building will be several times the cost of any other means of heating. The value of heat provided for this building has been estimated to be equivalent to 8,000 gallons of fuel per year. 3.0.0 WASTE HEAT SYSTEM CONCEPTS 3.1.0 General Waste heat system concepts that have been investigated in this study are described here. This study does not attempt to investigate all possible waste heat system concepts for use in Metlakatla, but concentrates on alternatives found reasonable as a result of the Power Authority's experience with waste heat recapture systems. Based on the field date collected, it seems clear to Power Authority staff that several details are pre-determined. Thus the differences between the concepts are limited to pipe routings, the number of buildings connected and to some extent the method of connection. All concepts studied would involve a system using the existing installation of exhaust gas and jacket water waste heat equipment in the power plant. Heat would be delivered to the user buildings through a constant output temperature, variable flow, water based system, which feeds into an underground distribution network. The network would consist of pre-insulated pipe using a steel carrier pipe, high density urethane foam insulation and high density polyethylene jacket pipe. In buildings with hydronic type heating systems, a large flat plate heat exchanger would transfer heat to the boiler return line in the existing heating system. A simple control valve would maintain a pre-set temperature in the existing heating system by limiting the flow in the waste heat recovery system. With this concept the boiler would function as an automatic back up heat source in case insufficient heat was available from the power plant. It is not recommended that heat is metered as "Btu-meters" have proven to be expensive and and somewhat unreliable. As all buildings are supported by the same entity which owns Metlakatla Power and Light, metering will not be necessary. If the display of in-kind contributions to user entities are needed, such displays can reasonably be based on estimates of the amounts of heat delivered. 3.2.0 Concept Al This concept provides heat for all the above mentioned buildings through district heating lines extending from the power plant along Walden Pt. Road, Atkinson Street, past the Head Start Building to the school complex. From here branch lines will connect to the proposed low income housing building and along Hillcrest Street and across to the new senior citizen complex. The main pipe run will most likely be 4" diameter with 2" service lines to the three school boiler rooms and to the activity center, the senior citizen complex, and to the low income housing building. The pipe to the council chambers will also be of 2" diameter and 1" service lines will be installed to all other users. See also attached map A. 3.3.0 Concept A2 This concept will be identical to concept Al with the only difference being the deletion of the connection to the low income housing. 3.4.0 Concept A3 This concept will be identical to concept A2 with the only difference being the deletion of the connection to the senior citizen center. 3.4.0 Concept Bl. As it has been described for concept Al, this concept will also provide heat to the school facilities, the activity center, the council chambers, the clinic, the youth center, the head start building, the townhall, the senior citizen center, and to the low income housing units. As it can be seen from map B, the main line will extend from the power plant across the south end of the chip dump to Airport Road and from there along the new road past the proposed low income housing units to the corner of Skater Lake Road and Eighth Avenue. From here a branch line along Skater Lake Road and Hillcrest Street will connect to the proposed senior citizen center and another branch will supply the school facilities, the activity center, and the town hall. Another branch line will supply the council chambers along with the clinic, the head start building, and the youth center. 3.5.0. Concept B2. This concept is identical to concept Bl with the only difference being the deletion of the connection to the senior citizen center. 4.0 COST ESTIMATES 4.1 General The cost estimates presented in this report are based on _ the following assumptions: a. System design follows Alaska Power Authority standards. b. Construction is performed by City of Metlakatla crews on a "force account" basis with the Alaska Power Authority providing basic engineering, some supervision and inspection, and start-up assistance. c. All lines will be buried in existing roads where ever possible and these roads will be re-established according to their prior state. d Labor rates of approximately $15/hour have been used for cost estimating purposes. Note that all cost estimates are based on preliminary designs only and consequently the cost estimates should be used with great caution. 4.2 Concept Al. Cost estimate: Power plant work $ 5,000 District heating piping 414,533 School facilities installation 41,000 LAC installation 12,500 Clinic, Youth Center, and Head Start 13,500 Council Ch., Senior C., and Low inc. 24,000 Townhall installation 5,500 Net construction $ 516,033 Job indirects, 30% 154,810 10 Construction cost $ 670,843 Overhead, 10% 67,084 Net project cost $ 737,927 Contingency, 15% 110,689 Total cost estimate $ 848,616 4.3 Concept A2. Cost estimate: Power plant work $ 5,000 District heating piping 353,578 School facilities installation 41,000 LAC installation 12,500 Clinic, Youth Center, and Head Start 13,500 Council Ch., and Senior C. 16,000 Townhall installation 5,500 Net construction $ 447,078 Job indirects, 30% 134,123 Construction cost $ 581,201 Overhead, 10% 58,120 Net project cost $ 639,321 Contingency, 15% 95,898 Total cost estimate $ 735,219 4.4 Concept A3. Cost estimate: Power plant work $ 5,000 District heating piping 274,705 11 School facilities installation 41,000 LAC installation 12,500 Clinic, Youth Center, and Head Start 13,500 Council Ch. 8,000 Townhall installation 5,500 Net construction $ 320,466 Job indirects, 30% 96,140 Construction cost $ 416,606 Overhead, 10% 41,661 Net project cost $ 458,267 Contingency, 15% 68,740 Total cost estimate $ 527,007 4.5 Concept Bl. Cost estimate: Power plant work $ 5,000 District heating piping 439,759 School facilities installation 41,000 LAC installation 12,500 Clinic, Youth Center, and Head Start 13,500 Council Ch., Senior C., Low in. 24,000 Townhall installation 5,500 Net construction $ 541,259 Job indirects, 30% 162,378 Construction cost $ 703,637 Overhead, 10% 70,364 Net project cost $ 774,001 Contingency, 15% 116,100 12 Total cost estimate $ 890,101 4.6 Concept B2. Cost estimate: Power plant work $ 5,000 District heating piping 427,753 School facilities installation 41,000 LAC installation 12,500 Clinic, Youth Center, and Head Start 13,500 Council Ch., Low in. 16,000 Townhall installation 5,500 Net construction $ 521,253 Job indirects, 30% 156,376 Construction cost $ 677,629 Overhead, 10% 67,763 Net project cost $ 745,392 Contingency, 15% 111,809 Total cost estimate $ 857,201 13 5.0 ECONOMIC ANALYSIS 5.1 General The economic analysis for the waste heat recapture system concepts addressed in this report was performed using the LOTUS 1-2-3 software and the following methodology: Based on actual power production figures for the diesel generator together with specific technical data for the generator the available waste heat was calculated for each hour during the year. Based on heating degree variations for Metlakatla together with fuel consumption data and operational characteristics provided by the City of Metlakatla the actual heat demand was calculated for each hour of the year. Comparing the available heat and the demand showed how much waste heat was actually utilized. At this point the estimated heat loss for the district heating lines was also taken into account. The waste heat utilized was added up hour by hour for the entire year. With a set of assumptions for load growth over the next 20 years, the same operation was done for each of the next 20 years and the annual fuel savings were derived. Based on current fuel cost and estimated fuel cost escalation together with the cost estimates presented in this report, a cash flow analysis and a pay back time were calculated for each of the concepts. Generally speaking, the pay back time indicates the period of time during which the project will have to operate as intended in order to pay off the initial investment. In this study, a discount rate of 4 percent has been used. The discount rate is approximately equal to the difference between the interest rate and the inflation rate. The annual operations and maintenance cost for each concept has been estimated at 2% of the construction cost for general operation and maintenance. (This item will be discussed in greater detail is subsequent sections.) Pay back times are based on the assumption that basic engineering and construction management is provided by the Alaska Power Authority and that all construction efforts are undertaken by the City of Metlakatla on a "force account" basis. 5.2 Concept Al. With the assumptions made, Concept Al shows a pay back time of 24 years. All heating needs for the buildings can be met during the first year of operation and it is anticipated that this waste 14 heat recapture concept would have annual operation and maintenance expenses of $16,972. Operation and maintenance expenses for the boiler systems could be expected to decrease significantly due to the systems being idle. 5.3 Concept A2. With the assumptions made, Concept A2 shows a pay back time of 22 years. All heating needs for the buildings can be met during the first year of operation and it is anticipated that this waste heat recapture concept would have annual operation and maintenance expenses of $14,704. Operation and maintenance expenses for the boiler systems could be expected to decrease significantly due to the systems being idle. 5.4 Concept A3. With the assumptions made, Concept A3 shows a pay back time of 18 years. All heating needs for the buildings can be met during the first year of operation and it is anticipated that this waste heat recapture concept would have annual operation and maintenance expenses of $11,847. Operation and maintenance expenses for the boiler systems could be expected to decrease significantly due to the systems being idle. 5.5 Concept Bl. With the assumptions made, Concept Bl shows a pay back time of 26 years. All heating needs for the buildings can be met during the first year of operation and it is anticipated that this waste heat recapture concept would have annual operation and maintenance expenses of $17,802. Operation and maintenance expenses for the boiler systems could be expected to decrease significantly due to the systems being idle. 5.6 Concept B2. With the assumptions made, Concept B2 shows a pay back time of 30 years. All heating needs for the buildings can be met during the first year of operation and it is anticipated that this waste heat recapture concept would have annual operation and maintenance expenses of $17,144. Operation and maintenance expenses for the boiler systems could be expected to decrease significantly due to the systems being idle. 15 6.0 CONCLUSIONS 6.1 General Discussion The power plant in Metlakatla is very well suited for the utilization of waste heat. District heating lines would be installed preferably in existing roads in order to avoid some of the very difficult soils conditions found around Metlakatla. It should be noted that no soils conditions have been investigated in detail, and consequently it cannot be guaranteed that it will even be possible to install a line through areas such as the chip dump. The cost estimates shown do not reflect any ripping of rocky soils nor do they include back filling with suitable replacement materials. The existing heating systems in the school can be modified for the utilization of waste heat. All systems seem to be capable of operating on medium grade heat, which is what is available from the power plant. Tie-ins in the existing boiler rooms would be fairly easy, as sufficient floor space is available and relatively simple heating systems are in place. All heating systems have been reviewed for compatibility with waste heat recapture systems, and it appears that no major technical obstacles will prevent the utilization of waste heat in the buildings addressed in this report. 6.2 Conclusion It is expected that the City would realize substantial savings in fuel and some savings in maintenance expenses from this project. Also, it is expected that the power plant would realize some savings from reduced station service loads. Maintenance savings have not been quantified and consequently have no effect on the calculated pay-back time. Annual operations and maintenance costs have been estimated at 2% of the capital cost of the project. No technical obstacles should prevent the installation of a waste heat recapture system utilizing waste heat from the power plant in a number of buildings. Provided that operational procedures are not changed drastically in the power plant, installation of a waste heat recapture system appears technically feasible. The concepts are similar in the sense that cost estimates are dominated by the cost of the distribution system. While it may be possible to reduce the cost of the distribution system through efficient installation techniques, it would not be prudent to base the cost estimates and thereby the project on such hopes. From the anticipated time of start up of all concepts, the plant will be capable of providing all the heating needs for all buildings connected. 16 Due to the relatively low price of fuel, and due to the length of the necessary distribution system, the economical feasibility appears unsatisfactory at this time. The five concepts show pay- back times of approximately 24, 22, 18, 26, and 30 years, when an annual fuel price escalation of 2% is used in conjunction with a real interest rate of 4% and a fuel cost of .80$/gallon. With the pay back times listed above, the project does not appear to be feasible at this time. Even if a fuel cost of $1.60 was used, the best alternative (A3) would show a pay back time of 7 years. In accordance with the feasibility demonstrated above, it is recommended that the project be postponed until such times when the potential fuel savings will provide for a pay back time of no more than 10 years. As an alternative means of reducing operating costs for some of the buildings involved, it is recommended that these buildings be audited for potential energy efficiency improvements. Especially the Loussac Activity Center has a great potential for efficiency improvements. Pump and fan operating costs can be greatly reduced through optimization and heating costs can be reduced through a connection to the oil fired high school heating system. 17