HomeMy WebLinkAboutCity of Napaskiak Wind Power and Heat Recovery Project Heat Recovery Study - Sep 2011 - REF Grant 7040016NAPASKIAK, ALASKA
HEAT RECOVERY STUDY
PREPARED FOR:
ALASKA ENERGY AUTHORITY
Project: AEA10-029, 2010 Waste Heat Recovery
PREPARED BY:
Alaska Energy and Engineering, Inc.Mailing Address - P.O. Box 111405 Anchorage, AK 99511-1405
(907) 349-0100, 349-8001 FAX
September 8, 2011
AEA- Napaskiak Heat Recovery Analysis August 2011
Alaska Energy and Engineering
Page 1 of 5
EXECUTIVE SUMMARY
Four community facilities in Napaskiak were evaluated for heat recovery potential.
Based on the heat available, the Headstart, the VPSO, the Tribal Office, and nearby
garage are proposed for heat recovery at this time. Total estimated annual heating
fuel use of these facilities is approximately 7,260-gallons. Estimated fuel savings
realized by implementing a heat recovery system is 6,699-gallons. The estimated cost
for the heat recovery project is $532,717. The simple payback based on a fuel cost of
$ 6.38 per gallon is 12.5 years.
1.0 INTRODUCTION
Alaska Energy and Engineering, Inc. was retained by the Alaska Energy Authority
(AEA) to review the feasibility of providing available recovered heat from the existing
Napaskiak Joint Utilities power plant to adjacent community buildings in Napaskiak,
and provide a budgetary project cost estimate based on Force Account Construction,
including Design Engineering and Construction Administration.
Currently there is not a heat recovery system in Napaskiak utilizing recoverable heat
from the power plant. Evaluated buildings are located together between 350 and 800
feet from the power plant, with the Headstart being the furthest building. For purposes
of this report, it is assumed that the power plant modifications are limited to installation
of a heat exchanger, circulating pumps, expansion tank, and interconnection to the
existing power plant cooling system.
Additional assumptions have been made in the development of this report including
but not limited to the proposed arctic piping route, building heating loads, and flow
rates and pressure drops of the existing power plant cooling system. It is anticipated
that refinements in arctic pipe size and routing, pump and heat exchanger sizing, and
other design elements will be required as final design is developed.
Available as-built information was obtained from AEA regarding the existing
generation equipment and power plant heat loads. End-user annual fuel use was
obtained from The Village of Napaskiak and Napaskiak Incorporated. A site visit was
conducted June 2, 2011.
2.0 OVERVIEW
The purpose of this study is to provide an estimate of the heat that can be recovered
from the jacket water of the Napaskiak Electric Utility Power Plant diesel engines and
used to offset heating oil consumption at the nearby public buildings. Useable
recovered heat is quantified in gallons of heating fuel saved using a gross heating
value of 134,000 BTU per gallon of #1 arctic diesel fuel and an overall efficiency of
75% for boilers and 85% for Toyo Laser direct vent stoves.
Buildings considered for this analysis include the Headstart, VPSO, Tribal Office
(formally Washeteria), and Garage. The estimated average annual heating fuel
consumption for the end-user buildings is as follows: Headstart is 2940-gallons, VPSO
is 1320-gallons, Tribal Office (assumed) is 1800-gallons, and the Garage is 1200-
gallons.
During the site visit the old Washeteria was being renovated for use as the new Tribal
Office. For the purposes of this report, the fuel usage data for the former Washeteria
was used for the new Tribal Office.
AEA- Napaskiak Heat Recovery Analysis August 2011
Alaska Energy and Engineering
Page 2 of 5
3.0 ESTIMATED RECOVERED HEAT UTILIZATION
A heat recovery utilization spreadsheet has been developed to estimate the
recoverable heat based on monthly total electric power production, engine heat rates,
building heating demand, heating degree days, passive losses for power plant heat
and piping, and arctic piping losses. The spreadsheet utilizes assumed time-of-day
variations for electric power production and heat demand. Power Cost Equalization
(PCE) data for fiscal years 2008, 2009, and 2010 were averaged and used in the
spreadsheet. The estimated heat rejection rate for the lead power plant genset, a
John Deere 6090 1800 rpm genset, is used to estimate available recovered heat.
Heating degree-days for Bethel were utilized for this site. All arctic piping is assumed
e grade. Information collected
from power plant renovations in 2009 were used to estimate the heating load for the
power plant.
The spreadsheet uses monthly heating degree-days to distribute annual fuel
consumption by month. The monthly heat load is then allocated by hour of day using
an estimated daily temperature variation (diurnal cycle). The end-user hourly heat load
is compared to the hourly available heat from the power plant, less power plant
heating loads and parasitic piping losses, and the net delivered heat to the end-user is
determined.
Following is a summary of annual fuel use and estimated recovered heat utilization in
equivalent gallons of fuel:
Facility Estimated Annual
Fuel Use (Gallons)
Estimated Heat *
Delivered (Gallons)
Headstart
VPSO
Tribal Office
Garage
2940
1320
1800
1200
2713
1218
1661
1107
Total 7260 6699
* Does not account for peak DHW loads
jacketed engine. However, while the marine jacket significantly increases the available
recovered heat from each engine, the increase in heat does not offset the reduced
fuel economy of a marine jacketed engine, so the option was dismissed.
4.0 HEAT RECOVERY SYSTEM DESCRIPTION AND OPERATION:
A heat recovery system will capture jacket water heat generated by the Napaskiak
Joint Utilities power plant that is currently rejected to the atmosphere. The recovered
heat will be transferred via below grade arctic piping to the end-users. The objective is
to reduce the consumption of expensive heating fuel by utilizing available recovered
heat. Although heat recovery is an excellent method of reducing heating fuel
costs, recovered heat is a supplementary heat source and it is imperative that
the end-user facility heating systems are operational at all times.
AEA- Napaskiak Heat Recovery Analysis August 2011
Alaska Energy and Engineering
Page 3 of 5
Hot engine coolant is piped through a plate heat exchanger located at the power plant,
and heat is transferred from the engine coolant to the recovered heat loop without
mixing the fluids. The recovered heat fluid is pumped through arctic pipe to the end-
user facilities, and is typically tied into the end-user heating system using either a plate
heat exchanger or cabinet unit heater.
4.1 Napaskiak Power Plant Tie-in
Modifications to the Napaskiak Joint Utilities power plant cooling system include
installation of a power plant heat exchanger, district heating pump, a new expansion
tank and new instrumentation.
aluminum jacket where exposed to the weather. All valves will be either bronze ball
valves, or lug style butterfly valves with seals compatible with 50/50 glycol/water
mixtures at 200°F. Air vents, thermometers, pressure gauges, drain valves and
pressure relief valves will also be provided.
4.2 Arctic Piping (Recovered Heat Loop)
The piping will be routed from the Napaskiak Power Plant within existing rights-of-way
wherever possible to the end-user buildings. The piping will exit the power plant
adjacent to the radiators.
The arctic piping system is a pre-insulated, bonded PEX piping system. The pipes
consist of Cross-Linked Polyethylene carrier pipe and LDPE outer jacket bonded to
polyurethane foam insulation. The carrier piping uses hydraulically pressed bronze or
steel couplings, similar to those used in high-pressure hydraulic hoses. The system
comes complete with all fittings, tools and accessories required for assembly. The
recovered heat fluid will be a 50/50 Propylene Glycol/Water solution to provide freeze
protection to the piping.
4.3 End-User Building Tie-ins
End-user building tie-ins typically consist of either brazed plate heat exchangers or
cabinet unit heaters. Plate heat exchangers located in the end-user mechanical rooms
will be tied into the boiler return piping to pre-heat the boiler water. Where Toyo-style
heaters are used, cabinet unit heaters will be located in the occupied space. The
maximum anticipated recovered heat supply temperature is about 180°F. When there
is insufficient recovered heat to meet the building heating load, the building heating
system (boiler or heater) will fire and add heat.
Typical piping will be type L copper tube with solder joints. Isolation valves will be
solder end bronze ball valves or flanged butterfly valves. All piping will be insulated
-service jacket. Flexibility will be provided
where required for thermal expansion and differential movement. Air vents,
thermometers, pressure gauges, drain valves and pressure relief valves will also be
provided.
AEA- Napaskiak Heat Recovery Analysis August 2011
Alaska Energy and Engineering
Page 4 of 5
4.4 Rights-of-Way Issues
There does not appear to be any conflicts with rights-of-ways for the arctic piping
between the power plant and the end-user buildings, as the route is expected to be
within existing rights-of-ways, end-user building property, and Napaskiak Inc. property.
A Heat Sales/Right-of-Entry Agreement will be required between Napaskiak Joint
Utilities and the end-
heat, and to authorize the renovation of the power plant heat recovery equipment
5.0 PRELIMINARY EQUIPMENT SELECTIONS
The following initial equipment selections are sized and selected based on preliminary
data and will require minor modifications to reflect final design.
5.1 Heat Exchangers
Based on initial selected flow rates, brazed plate heat exchangers appear to be
suitable for all locations. Initial heat exchanger selections are as follows. Fluid in
Primary loop of power plant assumed to be 50% Ethylene Glycol, all other loops
assumed to be 50% Propylene Glycol.
HX-1: Power Plant 300 MBH capacity
Primary: 74 GPM 190 F° EWT, 2.0 PSI max WPD
Secondary: 41 GPM 180 F° LWT, 1.0 PSI max WPD
HX-2: Garage 40 MBH capacity
Primary: 6 GPM 180 F° EWT, 1.5 PSI max WPD
Secondary: 8 GPM 175 F° LWT, 2.0 PSI max WPD
CUH-1: Tribal Office 70 MBH capacity
Primary: 10 GPM 180 F° EWT, 2.0 PSI max WPD
CUH-2: VPSO 50 MBH capacity
Primary: 7 GPM 180 F° EWT, 2.0 PSI max WPD
CUH-3&4: Headstart 60 MBH capacity
Primary: 9 GPM 180 F° EWT, 2.0 PSI max WPD
5.2 Arctic Piping
The heat recovery loop piping between the power plant and Headstart is
approximately 1550-
PEX preinsulated arctic piping to minimize pressure drop and reduce pumping energy.
AEA- Napaskiak Heat Recovery Analysis August 2011
Alaska Energy and Engineering
Page 5 of 5
5.3 Circulating Pumps
The heat recovery loop circulating pump will be located in the power plant and will
circulate 50/50 propylene glycol to the end users. The pump is sized for the estimated
available recovered heat and not the end-
P-HR1: District Heating Pump
Initial Selection: Grundfos UPS 40-160/
5.4 Expansion Tank
The heat recovery loop volume is approximately 340-gallons. Pressure relief at the
power plant heat exchanger will be 50 PSIG and the maximum normal operating
pressure will be 90% of maximum (45 PSIG).
ET-1: System requirements: 39 gallon tank and 24 gallon acceptance
Select: Extrol AX-120V, 68 gallon tank and 34 gallon acceptance
6.0 CONCLUSIONS AND RECOMMENDATIONS
Estimated construction costs were determined based on prior recent heat recovery
project experience, and include materials, equipment, freight, labor, design,
construction management, and startup and testing. All work at the Napaskiak Power
Plant, Tribal Office, Garage, VPSO, and Headstart buildings, and design and
construction management/administration for the project is included (refer to attached
cost estimate).
The estimated project cost for the washeteria only is $532,717. Estimated fuel savings
are 6,699-gallons. Using an assumed fuel price of $6.38/gallon results in estimated
savings of $42,740 annually, for a simple payback of 12.5 years.
Heat Avail vs. DemandPage 5020040060080010001200Heating Fuel Equivalent (Gallons per Month) Napaskiak Estimated Recovered Heat Utilization Recovered Heat AvailableTotal Heat DemandRecovered Heat Delivered
9/8/2011 ANNUAL HEAT Page 6 of 15Page 6020040060080010001200Gallon #1 Heating Fuel NAPASKIAK RECOVERED HEAT 6699 Gal Recovered Heat561 Gal Boiler Heat
ALASKA ENERGY ENGINEERINGAEA - NAPASKIAK HEAT RECOVERY PROJECTFORCE ACCOUNT CONSTRUCTION COST ESTIMATESUMMARY 9/8/2011SITE WORK / ARCTIC PIPING $103,500POWER PLANT UPGRADES / EX HEAT RETROFIT $37,755POLICE STATION $39,960GARAGE 12 $39,660TRIBAL OFFICE $39,970HEADSTART $43,810MISCELLANEOUS $13,500OVERHEAD $29,815FREIGHT $35,961CONSTRUCTION SUB-TOTAL $383,931DESIGN AND CONSTRUCTION ADMIN. $30,000CONSTRUCTION MANAGEMENT $30,000PROJECT SUB-TOTAL $443,931CONTINGENCY @ 20% $88,786TOTAL PROJECT COST $532,717
ALASKA ENERGY AND ENGINEERINGAEA - NAPASKIAK HEAT RECOVERY PROJECTFORCE ACCOUNT CONSTRUCTION COST ESTIMATE9/8/2011ITEMQUANUNITUNITMATLUNITLABLABLABORCONTRFREIGHTTOTALUNITTOTAL COSTCOSTHRSHRSRATECOSTCOSTCOSTCOSTWTWT(#)SITE & EXTERIOR WORKPEX - 1" Arctic Pipe 100lin.ft.$15.00$1,5000.2020$85$1,700$3,2000.8080PEX - 1-1/4" Arctic Pipe 300lin.ft.$17.00$5,1000.1030$85$2,550$7,6500.90270PEX - 2" Arctic Pipe 320lin.ft.$25.00$8,0000.1340$85$3,400$11,4001.50480PEX - 63mm Arctic Pipe 575lin.ft.$27.00$15,5250.1058$85$4,888$20,4131.801035PEX - 75mm Arctic Pipe 700lin.ft.$30.00$21,0000.1070$85$5,950$26,9502.301610PEX Pipe Fittings3991/ft$5.00$1,9950$85$0$1,9951.0399Rigid Insulation (2"x24"x96")259ea.$20.00$5,1880.126$85$2,205$7,3921.0259Prop Glycol (50/50 - 55-gal drum)7ea.$650.00$4,55000$85$0$4,550520.03640Trenching / Grading997.5lin.ft.$0.00$000$85$0$19,950$19,9500.00Power Plant ModificationsPlate HXR, ( 300 MBh @ 15F)1ea.$2,000$2,0001010$85$850$2,850100.0100Circ Pump (42 GPM @ 38') 2 ea. $1,300 $2,600 40 80 $85 $6,800 $9,400 132.0 264Electrical (Misc) 1 ea. $2,000 $2,000 40 40 $84 $3,360 $5,360 500.0 500Misc Strut & Pipe Hangers 1 lump $3,000 $3,000 20 20 $85 $1,700 $4,700 200.0 200Pipe/Valves/Ftgs/Gauges 1 lump $7,000 $7,000 60 60 $85 $5,100 $12,100 1500.0 1500Expansion Tank (AX-120V) 1 ea. $1,645 $1,645 20 20 $85 $1,700 $3,345 235.0 235Police StationCabinet Unit Heater ( 50 MBh)1 ea. $1,500 $1,500 10 10 $85 $850 $2,350 100.0 100Electrical (Misc) 1 ea. $2,000 $2,000 40 40 $84 $3,360 $5,360 500.0 500Temp Control Device 1 ea. $1,500 $1,500 10 10 $85 $850 $2,350 10.0 10Pipe/Valves/Ftgs/Gauges 1 lump $7,000 $7,000 60 60 $85 $5,100 $12,100 1500.0 1500Misc Strut / Pipe Hangers/ Hardware 1 lump $2,000 $2,000 40 40 $85 $3,400 $5,400 500.0 500BTU meter 1 ea. $8,500 $8,500 20 20 $85 $1,700 $10,200 50.0 50Misc. Controls 1 lump $500 $500 20 20 $85 $1,700 $2,200 200.0 200Garage 12Plate HXR, ( 40 MBh)1 ea. $1,200 $1,200 10 10 $85 $850 $2,050 50.0 50Electrical (Misc) 1 ea. $2,000 $2,000 40 40 $84 $3,360 $5,360 500.0 500Temp Control Device 1 ea. $1,500 $1,500 10 10 $85 $850 $2,350 10.0 10Pipe/Valves/Ftgs/Gauges 1 lump $7,000 $7,000 60 60 $85 $5,100 $12,100 1500.0 1500Misc Strut / Pipe Hangers/ Hardware 1 lump $2,000 $2,000 40 40 $85 $3,400 $5,400 500.0 500BTU meter 1 ea. $8,500 $8,500 20 20 $85 $1,700 $10,200 50.0 50Misc. Controls 1 lump $500 $500 20 20 $85 $1,700 $2,200 200.0 200A-2 of 4
ALASKA ENERGY AND ENGINEERINGAEA - NAPASKIAK HEAT RECOVERY PROJECTFORCE ACCOUNT CONSTRUCTION COST ESTIMATE9/8/2011ITEMQUANUNITUNITMATLUNITLABLABLABORCONTRFREIGHTTOTALUNITTOTAL COSTCOSTHRSHRSRATECOSTCOSTCOSTCOSTWTWT(#)Tribal Office/Old LaundromatCabinet Unit Heater ( 70 MBh)1 ea. $1,500 $1,500 10 10 $86 $860 $2,360 100.0 100Electrical (Misc) 1 ea. $2,000 $2,000 40 40 $84 $3,360 $5,360 500.0 500Temp Control Device 1 ea. $1,500 $1,500 10 10 $85 $850 $2,350 10.0 10Pipe/Valves/Ftgs/Gauges 1 lump $7,000 $7,000 60 60 $85 $5,100 $12,100 1500.0 1500Misc Strut / Pipe Hangers/ Hardware 1 lump $2,000 $2,000 40 40 $85 $3,400 $5,400 500.0 500BTU meter 1 ea. $8,500 $8,500 20 20 $85 $1,700 $10,200 50.0 50Misc. Controls 1 lump $500 $500 20 20 $85 $1,700 $2,200 200.0 200HeadstartCabinet Unit Heater ( 60 MBh)2 ea. $1,500 $3,000 10 20 $85 $1,700 $4,700 50.0 100Electrical (Misc) 1 ea. $2,000 $2,000 40 40 $84 $3,360 $5,360 500.0 500Temp Control Device 1 ea. $1,500 $1,500 10 10 $85 $850 $2,350 10.0 10Pipe/Valves/Ftgs/Gauges 1 lump $8,500 $8,500 60 60 $85 $5,100 $13,600 1500.0 1500Misc Strut / Pipe Hangers/ Hardware 1 lump $2,000 $2,000 40 40 $85 $3,400 $5,400 500.0 500BTU meter 1 ea. $8,500 $8,500 20 20 $85 $1,700 $10,200 50.0 50Misc. Controls 1 lump $500 $500 20 20 $85 $1,700 $2,200 200.0 200MISCELLANEOUSMisc Hardware 1 lump $5,000 $5,000 0 0 $85 $0 $5,000 499.0 499Misc Hardware 1 lump $2,500 $2,500 0 0 $85 $0 $2,500 500.0 500Misc Tools & Safety Gear 1 lump $4,000 $4,000 0 0 $85 $0 $4,000 1500.0 1500Consumables, Gases, Etc. 1 lump $2,000 $2,000 0 0 $85 $0 $2,000 1500.0 1500OVERHEADROW Legal Work 1 lump $2,000 $2,000 0Rent Heavy Equip 1 lump $2,500 $2,500 0Misc Tool Rent 1 lump $5,000 $5,000 0Commission System & Training 20 hr 1 20 $95 $1,900 $1,900 0Superintendent Overhd Off-Site 40 hr 1 40 $95 $3,800 $3,800 0Superintendent Overhd On-Site 40 hr 1 40 $95 $3,800 $3,800 0Crew Travel Time 12 hr 1 12 $95 $1,140 $1,140 0Crew Airfares 2 trips $1,000 $2,000 $2,000 0Crew Per Diem 70mn.dy.$60 $4,186 $4,186 0Housing Rent2.3mo.$1,500$3,489$3,4890A-3 of 4
ALASKA ENERGY AND ENGINEERINGAEA - NAPASKIAK HEAT RECOVERY PROJECTFORCE ACCOUNT CONSTRUCTION COST ESTIMATE9/8/2011ITEMQUANUNITUNITMATLUNITLABLABLABORCONTRFREIGHTTOTALUNITTOTAL COSTCOSTHRSHRSRATECOSTCOSTCOSTCOSTWTWT(#)FREIGHT25,961Freight25961lb. $1.00 $25,961Air Freight Tool Mob & Demob 2 lump $2,500 $5,000Misc Small Freight & Gold Streaks1lump$5,000$5,000CONSTRUCTION SUB-TOTAL $189,3031,395$119,542$39,125$35,961$383,931Engineering (Design & CCA) 1 lump $30,000Construction Management1lump$30,000PROJECT SUB-TOTAL $189,303$119,54299,125$ $35,961$443,931Contingency20%$88,786CONSTRUCTION TOTAL$532,717A-4 of 4