HomeMy WebLinkAboutUAF Organic Rankine Cycle Field Testing Tok Green Machine Project - May 2013 - REF Grant 7040046Tok Green Machine Project
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TOK GREEN MACHINE
INSTALLATION BY ALASKA POWER & TELEPHONE
FOR UAF/ACEP
May 2013
TABLE OF CONTENTS
1 Introduction……………………………………………………………………………..2
2 Cold side condensing Options…………………………………………………..3
3 Hot side heating Options……………………………………………….…………4
4 Tok Powerplant Considerations……………………………………………..…4
5 Selected Arrangement for Tok ORC…………………………………………..5
6 Cost estimate for Tok ORC Installation………………………………………5
7 ORC installation/Operation Schedule………………………………….…5-6
APPENDICES
Appendix A: Tok System Loads………………..………………………………7
Appendix B: Tok Existing Heat Loads……………………………………….8
Appendix C: Available Jacket Water Heat………………………………..9
Appendix D: Heat Recovery Modifications…………………………10-23
Appendix E: ORC Installation Cost………………………………………….24
Appendix F: ORC Installation Schedule…………………………………..25
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1. Introduction:
University of Alaska Fairbanks, Alaska Center for Energy and Power (UAF/ACEP) was
awarded a grant to demonstrate an Organic Rankine Cycle (ORC) generator in a diesel-
fired Tanana Chief’s Conference (TCC) -affiliated community in Alaska. The ORC was
procured by TCC in a previous grant and tested under laboratory conditions at UAF.
Alaska Power & Telephone (AP&T) has been contracted to deploy and demonstrate the
ORC in the Tok, AK powerplant. The first phase of this contract is to prepare a detailed
cost estimate and timeline for modifications to the Tok plant for installation and
operation of the ORC.
An ORC generates electric energy by pumping a working fluid to a boiler where it
changes state from liquid to gas using relatively low temperature heat. The pressurized
vapor is then expanded through a turbine that turns a generator and then returns to a
liquid in a condenser using a cooling medium. The working fluid boils at relatively low
temperature enabling an ORC to operate with low temperature heat sources such as
diesel jacket water, geothermal or industrial waste heat.
The ORC procured by TCC is a machine manufactured by ElectraTherm, Inc. This unit is
referred to by ElectraTherm as the Green Machine. While the output is rated at 30-
50kw, it is highly dependent on the temperatures and heat capacity of the hot and cold
sides. Several different heating and cooling alternatives were considered for the
installation in the Tok plant.
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2. COLD SIDE CONDENSING HEAT SINK OPTIONS CONSIDERED
Cooling Tower: ACEP has a cooling tower available. The cooling capacity and outlet
temperature are a function of ambient wet bulb temperature. Advantages:
moderate water requirements, reduced civil site work. Disadvantages: parasitic fan
and pumping loads, cold weather freeze issues, ice fog, condenser scaling.
Ground Loop Heat Sink: Advantages: Simple plastic pipe coils placed in trenches
and manifolded together. Disadvantages: very large area required for heat
dissipation, subject to non-repairable (winter) leaks, potential for dig in, frost heave
damage, permafrost melt, heat transfer reduced with glycol fluid.
Radiator and Fans: Advantages: no water requirement, no scale issues with glycol,
no civil construction, minimal fan requirement in the winter. Disadvantages:
physically large and expensive ($72k per McKinley), cooling limited during high
ambient temps, requires exterior cleaning maintenance, requires glycol which lowers
thermal exchange and is a hazmat, introduces pump and fan loads.
Exchanger in a well: Advantages: same advantages as the radiator plus the fan load
are eliminated. Disadvantages: large diameter well casing needed, custom built heat
exchanger to fit in well, exchanger design dependent on factors that would require
studies such as soil heat capacity, subterranean water flows etc, large wells do not
lend themselves to rural village construction.
Well or River water: Advantages: river or lake water available in many rural villages,
the Tok aquifer is believed to have sufficient supply (95gpm) of 38F water, no
additional parasitic loads beyond pumping, Disadvantages: requires significant
water supply, requires drain field, may create scale in the condenser, may require
pump to recirculate some of the discharge if the flow rate is too low.
Combination of radiator and well water: Advantages: utilize radiator in cold
weather and well water in the warm weather potentially reducing parasitic pumping
and fan loads, no scale issues in the GM. Disadvantages: the cold circuit will require
pumped glycol through the radiator and a heat exchanger between the well water
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and the glycol/radiator circuit, glycol and exchanger will decrease heat transfer
efficiency, more complicated operation and control, questionable reduction in
parasitic loads.
3. HOT SIDE HEAT RECOVERY OPTIONS CONSIDERED
Exhaust heat recovery: Approximately a third of the heat produced by the fuel is
expelled in the exhaust of a diesel engine. Of this amount, approximately 40-50% is
recoverable. Advantages: utilizes more of the heat available allowing an ORC match
with a smaller diesel generator, higher temperatures are available providing a
greater delta T between the ORC hot and cold side. Disadvantages: Coolant
circulation must be maintained or the exchanger will become a boiler (this is
overcome if the engine coolant pump is used to maintain circulation), exhaust
exchangers foul with soot and need frequent cleaning (may be automated with soot
blowers), high cost.
Jacket water heat recovery: Approximately a quarter of the heat produced by the
fuel in a diesel engine is rejected to the jacket water, oil cooler and aftercooler. The
jacket water is cooled via radiator and fans or some other heat exchange device.
Almost all of the jacket water heat is recoverable. Some diesels utilize a separate
circuit aftercooler (SCAC) that has a separate radiator or exchanger providing lower
temperature engine inlet air than possible with the jacket water. Heat recovery from
the SCAC is generally not feasible due to the lower temperature. Typical engine
jacket water temperature is 185F to 195F. To eliminate freeze problems, 60%
glycol/water mix is used where there will be exposure to arctic temperatures. This
provides freeze protection to -70F but reduces cooling capacity by 12%.
4. TOK POWERPLANT CONSIDERATIONS
The Green Machine ORC requires at least 1 million BTU’s per hour of heat. This
amount of heat is typically available from the jacket water of a diesel operating at
700 to 1000 kW electrical load. The Tok system electrical loads vary from winter to
summer and over the course of each day. Tok loads are shown in Appendix A.
The Tok power plant has six Caterpillar diesel generators. A heat recovery system
captures jacket water heat from all but the smallest engine and is utilized for the
building complex heat and maintaining the temperature of the non- operating
generators. In the winter, the heat recovery loop temperatures drop to as low as
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150F. Modifications to the heat recovery system will need to be made to capture
additional heat for the ORC.
While the heat available at the Tok plant is a function of the system load, other heat
loads reduce the amount of heat available for the ORC operation. Appendix B shows
the approximate existing heat loads for winter and summer.
The manufacturers’ heat rejection data varies by model so the heat available is
dependent on which generators are running. The largest generator, Unit 7, can carry
the entire Tok load solo. At other times, there will be two generators running in
parallel. Appendix C shows the potential jacket water heat available for winter and
summer, high and low load periods, and with single or parallel generator operation.
It appears that the ORC output will be limited during the low load periods.
In order to capture necessary heat to operate the ORC with any combination of
generators operating, modifications will need to be made to the Tok heat recovery
system. This will include reconnecting the heat recovery exchangers in series,
installation of thermostatically controlled valves to bypass the radiators, installing
larger heat recovery exchangers and pumps. Appendix D includes diagrams of the
heat recovery system and proposed modifications.
5. SELECTED ARRANGEMENT FOR TOK ORC
Several alternative arrangements have been considered for demonstration of the
TCC ORC in the Tok diesel plant. The selected configuration places the ORC next to
diesel Unit 7 which is at the west end of the heat recovery loop. The heat recovery
system will be upgraded to the extent possible with funding available. Cooling will
utilize water from well No. 2 and discharge into a new drainfield or possibly into Well
No.3. The power from the ORC will be connected to the plant 480 volt station
service panel located to the north. See Appendix D.
6. COST ESTIMATE FOR TOK ORC INSTALLATION
The installation of the Green Machine has been broken down into tasks for which
materials and labor have been estimated. Total amount is $187,954. A summary of
this estimate is found in Appendix E.
7. ORC INSTALLATION/OPERATION SCHEDULE
The installation was scheduled assuming AP&T in-house labor resources will be
available. The summer season is a busy time for AP&T and the schedule is subject to
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changes if emergencies arise requiring reallocation of labor. Local contractors may
be engaged if required to meet the schedule albeit at substantial increase in
expense.
AP&T would like to expedite the installation and gain as much operational
experience as possible before the conclusion of the demonstration. It is unfortunate
that the demonstration does not extend into the winter period. Appendix F has the
summary schedule.
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APPENDIX A
TOK ELECTRICAL SYSTEM LOADS 2011
Winter Winter Spring Spring Summer Summer Fall Fall
Time Weekday Weekend Weekday Weekend Weekday Weekend Weekday Weekend
0:00 1200 1260 900 930 930 930 820 840
1:00 1080 1200 870 900 900 930 820 810
2:00 1050 1140 840 840 870 870 780 780
3:00 1050 1110 840 840 810 780 780 780
4:00 1020 1140 850 840 810 780 780 750
5:00 1050 1140 900 810 780 810 810 780
6:00 1080 1170 1050 840 900 870 990 840
7:00 1260 1200 1200 930 1050 990 1170 900
8:00 1380 1260 1260 1020 1170 1080 1230 990
9:00 1490 1320 1260 1110 1230 1080 1200 1050
10:00 1500 1440 1290 1140 1260 1140 1320 1080
11:00 1500 1500 1290 1170 1200 1140 1290 1110
12:00 1500 1530 1300 1170 1230 1100 1230 1140
13:00 1560 1530 1260 1110 1230 1140 1260 1080
14:00 1470 1530 1230 1140 1200 1200 1200 1080
15:00 1500 1500 1170 1110 1200 1140 1260 1110
16:00 1380 1490 1170 1110 1170 1170 1200 1080
17:00 1380 1550 1140 1050 1170 1170 1200 1110
18:00 1500 1560 1110 1080 1200 1170 1170 1170
19:00 1560 1560 1110 1020 1200 1200 1230 1200
20:00 1440 1500 1050 1020 1200 1170 1200 1170
21:00 1380 1400 1100 1020 1200 1230 1110 1050
22:00 1320 1380 1100 1000 1140 1110 990 960
23:00 1260 1290 1020 1020 1080 1020 870 870
AVERAGE 1330 1363 1096 1009 1089 1051 1080 989
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APPENDIX B
Tok Estimated Heating Loads
Winter Non Winter
Exchanger EST BTU/hr EST BTU/hr
Office building Basement baseboard
100,000
40,000
Mgr House Basement baseboard
100,000
40,000
Truck Shop Dual Rads (2) Young CL174 Rad/Fan
168,000
50,000
Truck Shop N Rad Modine AK3-1 Rad/Fan
100,000
20,000
Garage Radiator /Fan
20,000
-
Garage/Office Baseboard
10,000
2,000
Powerplant office Baseboard
10,000
2,000
Switchgear Room Radiator /Fan
50,000
10,000
Well house Radiator /Fan
5,000
-
Fuel heat exchanger Radiator /Fan
5,000
-
C175 (winter heater) Radiator /Fan
380,000
-
No 3 heat HR exchanger/eng circ pump
10,000
10,000
No 4 heat HR exchanger/eng circ pump
10,000
10,000
No 5 heat HR exchanger/eng circ pump
10,000
10,000
No 9 heat HR exchanger/eng circ pump
10,000
10,000
No 8 heat HR exchanger/eng circ pump
10,000
10,000
No 7 heat Electric heaters
998,000
214,000
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APPENDIX C
Tok Diesel Plant Jacket Water Heat Available
After Heat Recovery Modifications
C175 Solo Operation
Winter High Winter low
Summer
High
Summer
Low
Load (kw) 1560 1020
1260 750
JW BTU/hr 4,301,640 2820720
3,477,840 2019000
Net after plant heat loads 3,303,640 1,822,720
3,263,840
1,805,000
Est Heat Available for ORC 2,609,876 1,439,949
2,578,434
1,425,950
Parallel Operation non C175
Winter High Winter low
Summer
High
Summer
Low
Load (kw) 1560 1020
1260 750
JW BTU/hr 2,916,000 1,944,000
2,481,600
1,551,000
Net after plant heat loads 1,918,000 946,000
2,267,600
1,337,000
Est Heat Available for ORC 1,515,220 747,340
1,791,404
1,056,230
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APPENDIX D
Tok Powerplant
ORC Installation
Heat Recovery System Modifications
R1
To achieve the maximum heat gain from latent heat in jacket water of engines 3, 4, 5, 8 & 9 the following mechanical
changes are planned:
Heat Recovery System Modifications
o The heat recovery system will be upgraded to improve flow and increase heat exchange through heat
recovery exchangers. We considered the upgrade of the system circulation pump but feel that the
existing pump will be adequate with the improved flow conditions of the modified heat recovery
system. The main change to the system will be reconnecting the unit heat recovery exchangers from the
parallel connected configuration they are currently in to a series connected configuration. In addition
isolation valves will be installed in the heat recovery header to direct heat recovery flow through
operating units and reduce flow through non operating units. The size of the heat recovery system
piping will be increased from 2” to 4” from the headers to the Unit 7 heat exchanger to allow the
capture of the heat from the C175 engine. Connections for the ORC will be included in this new 4”
piping.
Heat recovery system 4” headers 2” piping connections into HE7
Modify existing 4” supply header
Install series connection ports [6 places]
Install 4” control valves [5 places]
Extend 4” supply and return headers to west side of powerplant
Replace 2” heat recovery piping to HE7 with 4” piping
Reconnect Unit 3, 4, 5, 7 and 9 heat recovery exchangers
Add 4” ORC connections
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System Drawings
Plan View of Existing Tok Heat Recovery System
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System Drawings
Plan View of Modified Tok Heat Recovery System with ACEP ORC
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System Drawings
Existing System Modified System
Typical Parallel Connection Typical Series Connection
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System Drawings
ACEP ORC Installation, also shows addition of 4” piping runs to HE7
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Unit 3 Heat Recovery Modifications
o Option A
Heat recovery exchanger HE3 will be disconnected from the heat recovery piping and
reconnected in series with the other heat recovery exchangers.
Remove undersized shell & tube heat exchanger and replace with new higher capacity plate
exchanger
Reconnect recovery exchanger in series
o Additional Optional Improvements
The existing undersized heat recovery shell and tube exchanger will be replaced with a higher
capacity plate exchanger
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Unit 4 Heat Recovery Modifications
o Option
Heat recovery exchanger HE4 will be disconnected from the heat recovery piping and
reconnected in series with the other heat recovery exchangers.
o Additional Optional Improvements
Install a thermostatically controlled 3-way valve into engine radiator circuit
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Unit 5 Heat Recovery Modifications
o Option
Heat recovery exchanger HE5 will be disconnected from the heat recovery piping and
reconnected in series with the other heat recovery exchangers.
o Additional Optional Improvements
Install a thermostatically controlled 3-way valve into engine radiator circuit
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Unit 9 Heat Recovery Modifications
o Option A
Heat recovery exchanger HE9 will be disconnected from the heat recovery piping and
reconnected in series with the other heat recovery exchangers.
o Additional Optional Improvements
Remove plate type heat recovery exchanger and replace with higher capacity plate exchanger
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Unit 8 Heat Recovery Modifications
o Option A
No modifications required - Unit 8 currently does not have a connection into the heat recovery
system. Unit 8 is used regularly to provide generation to meet peaking loads.
o Additional Optional Improvements
Install heat recovery exchanger between engine cooling outlet and engine cooling exchanger
inlet
Install heat recovery piping between exchanger and heat recovery headers.
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Unit 7 Heat Recovery Modifications
o Option A
Unit 7 is the large machine at Tok and operates as a sole generator when operating. The heat
recovery exchanger HE7 is sufficient. A 3-way thermostatically controlled valve will be installed
into the radiator circuit to improve heat transfer. HE7 is currently connected to the heat
recovery system with 2” pipes that are small for rated ORC flow. New 4” pipes will be fabricated
and installed to connect HE7 into the heat recovery headers.
Disconnect HE7 from 2” heat distribution system
Reconnect HE7 with 4” heat recovery system
Add thermostatically controlled 3-way valve into engine radiator circuit
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Install ORC WCC [OPTION A]
o The ElectraTherm Green Machine that was tested by ACEP will be shipped and installed in the Tok
powerplant.
The ORC will be positioned near Unit 7.
The hot side connections will be made to the 4” heat recovery piping near HE7.
The cold side connections will be made to existing well #2 and new drain field that will be
constructed on the south side of the powerplant
The power generated by the ORC will feed the Tok electrical grid. The ORC will be connected to
the 480V service equipment located in front of Unit 7.
ACEP instrumentation will be installed for the collection of performance data
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Additional System Improvements to Increase Heat Recovery for Higher ORC Annual Output
System Drawing
Additional System Improvements to Increase Heat Recovery for Higher ORC Annual Output
Adding Thermostatic Bypass Valves at Units 4 and Unit 5
o To improve the recovery of heat from the generator cooling systems in the winter 3-way thermostatic
valves can be added to the radiator circuits to bypass the radiator.
http://www.amot.com/tenants/amot/documents/Datasheet_B_Thermostatic_Valve_0712_rev15.pdf
o A thermostatic valve will be added to the Unit 7 radiator circuit during the initial heat recovery system
modifications and has been included in the budget. Also being considered is the addition of similar
valves into the radiator systems of Unit 4 and 5.
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Replacing Inefficient Heat Recovery Heat Exchangers at Units 3 and Unit 9
o The existing shell and tube heat exchanger installed on Unit 3 is undersized to deliver optimum heat
transfer to the heat recovery system.
o Similarly the heat recovery plate exchanger currently installed at Unit 9 is not sized correctly and was
originally installed improperly each of these conditions limiting the amount of residual heat that can be
transferred into the heat recovery system.
Adding a Heat Recovery Heat Exchanger at Unit 8
o Currently Unit 8 is nor equipped with an exchanger to capture jacket water heat and transfer it into the
heat recovery system. Unit 8 is a small unit that is operated regularly at high efficiency to provide the
electrical power required to meet peaking loads. Adding a heat recovery heat exchanger could increase
the heat recovery system delivery to the ORC.
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APPENDIX E
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APPENDIX F
INSTALLATION SCHEDULE